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Sample records for wing flow field

  1. Experimental study of flow field distribution over a generic cranked double delta wing

    Directory of Open Access Journals (Sweden)

    Mojtaba Dehghan Manshadi

    2016-10-01

    Full Text Available The flow fields over a generic cranked double delta wing were investigated. Pressure and velocity distributions were obtained using a Pitot tube and a hot wire anemometer. Two different leading edge shapes, namely “sharp” and “round”, were applied to the wing. The wing had two sweep angles of 55° and 30°. The experiments were conducted in a closed circuit wind tunnel at velocity 20 m/s and angles of attack of 5°–20° with the step of 5°. The Reynolds number of the model was about 2 × 105 according to the root chord. A dual vortex structure was formed above the wing surface. A pressure drop occurred at the vortex core and the root mean square of the measured velocity increased at the core of the vortices, reflecting the instability of the flow in that region. The magnitude of power spectral density increased strongly in spanwise direction and had the maximum value at the vortex core. By increasing the angle of attack, the pressure drop increased and the vortices became wider; the vortices moved inboard along the wing, and away from the surface; the flow separation was initiated from the outer portion of the wing and developed to its inner part. The vortices of the wing of the sharp leading edge were stronger than those of the round one.

  2. Flow Field Analysis of Fully Coupled Computations of a Flexible Wing undergoing Stall Flutter

    Science.gov (United States)

    2016-01-01

    instantaneously measure the wing deformation . Clearly, these sensors rely upon the structural deformation for determining the extent of the defor...Torsion Figure 3. Modal structural model containing both bending and torsional modes. which can be simplified to Cµ = U2j A j U2∞Are f (6) since the...orthogonal decomposition (POD) was used on the pressure in the flow field.? Because the mesh is deforming due to the fluid-structure coupling and the

  3. Flow Field Characteristics and Lift Changing Mechanism for Half-Rotating Wing in Hovering Flight

    Science.gov (United States)

    Li, Q.; Wang, X. Y.; Qiu, H.; Li, C. M.; Qiu, Z. Z.

    2017-12-01

    Half-rotating wing (HRW) is a new similar-flapping wing system based on half-rotating mechanism which could perform rotating-type flapping instead of oscillating-type flapping. The characteristics of flow field and lift changing mechanism for HRW in hovering flight are important theoretical basis to improve the flight capability of HRW aircraft. The driving mechanism and work process of HRW were firstly introduced in this paper. Aerodynamic simulation model of HRW in hovering flight was established and solved using XFlow software, by which lift changing rule of HRW was drawn from the simulation solution. On the other hand, the development and shedding of the distal vortex throughout one stroke would lead to the changes of the lift force. Based on analyzing distribution characteristics of vorticity, velocity and pressure around wing blade, the main features of the flow field for HRW were further given. The distal attached vortex led to the increase of the lift force, which would gradually shed into the wake with a decline of lift in the later downstroke. The wake ring directed by the distal end of the blade would generate the downward accelerating airflow which produced the upward anti-impulse to HRW. The research results mentioned above illustrated that the behavior characteristics of vortex formed in flow field were main cause of lift changing for HRW.

  4. Aerodynamic characteristics and flow field of delta wings with the canard

    Directory of Open Access Journals (Sweden)

    Mochizuki Saya

    2018-01-01

    Full Text Available Now, many kinds of explorations for outer planets have been proposed around the world. Among them Mars attracts much attention for future exploration. Orbiters and landers have been used for Mars exploration. Recently as a new exploration method, the usage of an airplane has been seriously considered and there are some development projects for Mars airplane. However, the airplane flying on the Earth atmosphere cannot fly on the Mars atmosphere, because atmospheric conditions are much different each other. Therefore, we focused on the usage of the airplane with unfolding wings for Mars exploration. These unfolding wings are designed as delta wings. However, delta wings do not have enough aerodynamics characteristics in a low speed region. In this study, to improve the aerodynamic characteristics of delta wings, we have proposed the usage of canard wings. The purpose of this study is to examine the effectiveness of canard wings to improve aerodynamic characteristics in a low speed region. CFD analysis is performed using four wing models with different canard shapes. The result shows that the usage of canards is effective to improve aerodynamic characteristics of delta wings in a low speed region. In addition, increasing lift coefficient is possible by changing the shape of canards.

  5. Flow structure on a rotating wing undergoing deceleration to rest

    Science.gov (United States)

    Tudball Smith, Daniel; Rockwell, Donald; Sheridan, John

    2013-11-01

    Inspired by the behavior of small biological flyers and micro aerial Vehicles, this study experimentally addresses the flow structure on a low aspect ratio rotating wing at low Reynolds number. The study focuses on a wing decelerating to rest after rotating at constant velocity. The wing was set to a constant 45° angle of attack and, during the initial phase of the motion, accelerated to a constant velocity at its radius of gyration, which resulted in a Reynolds number of 1400 based on the chord length. Stereoscopic PIV was used to construct phase-averaged three-dimensional (volumetric) velocity fields that develop and relax throughout the deceleration and cessation of the wing motion. During gradual deceleration, the flow structure is maintained when normalised by the instantaneous velocity; the distinguishing feature is shedding of a trailing edge vortex that develops due to the deceleration. At higher deceleration rates to rest, the flow structure quickly degrades. Induced flow in the upstream direction along the surface of the wing causes detachment of the previously stable leading edge vortex; simultaneously, a trailing-edge vortex and the reoriented tip vortex form a co-rotating vortex pair, drawing flow downward away from the wing.

  6. Unsteady flow over flexible wings at different low Reynolds numbers

    Directory of Open Access Journals (Sweden)

    Genç Mustafa Serdar

    2016-01-01

    Full Text Available In this study, unsteady flow around flexible membrane wing which had aspect ratio of 1 (AR=1 was investigated experimentally at various Reynolds numbers (Re = 25000 and Re = 50000. Smoke-wire technique for flow visualization over the flexible membrane wing was utilized in the experiments. Digital Image Correlation system (DIC was used for measuring deformation of AR = 1 flexible membrane wing. Instantaneous deformation measurements of membrane wing were combined with the flow field measurements. In low aspect ratio flexible membrane wings, unsteadiness includes tip vortices and vortex shedding, and the combination of tip vortices. In these types of wings, complex unsteady deformations occurred due to vortex shedding. The results showed that the increasing angle of attack results in increase of membrane deformation. Moreover, it was concluded that analysis of the instantaneous deformation revealed chordwise and spanwise, modes which were due to the shedding of leading-edge vortices as well as tip vortices. Consequently, vibrational mode decreased and maximum standard deviation location approached to the trailing edge by reason of increasing angle of attack.

  7. Flow structure of vortex-wing interaction

    Science.gov (United States)

    McKenna, Christopher K.

    Impingement of a streamwise-oriented vortex upon a fin, tail, blade or wing represents a fundamental class of flow-structure interaction that extends across a range of applications. This interaction can give rise to time-averaged loading, as well as unsteady loading known as buffeting. The loading is sensitive to parameters of the incident vortex as well as the location of vortex impingement on the downstream aerodynamic surface, generically designated as a wing. Particle image velocimetry is employed to determine patterns of velocity, vorticity, swirl ratio, and streamlines on successive cross-flow planes upstream of and along the wing, which lead to volume representations and thereby characterization of the interaction. At locations upstream of the leading edge of the wing, the evolution of the incident vortex is affected by the presence of the wing, and is highly dependent on the spanwise location of vortex impingement. Even at spanwise locations of impingement well outboard of the wing tip, a substantial influence on the structure of the incident vortex at locations significantly upstream of the leading edge of the wing was observed. For spanwise locations close to or intersecting the vortex core, the effects of upstream influence of the wing on the vortex are to: decrease the swirl ratio; increase the streamwise velocity deficit; decrease the streamwise vorticity; increase the azimuthal vorticity; increase the upwash; decrease the downwash; and increase the root-mean-square fluctuations of both streamwise velocity and vorticity. The interrelationship between these effects is addressed, including the rapid attenuation of axial vorticity in presence of an enhanced defect of axial velocity in the central region of the vortex. Moreover, when the incident vortex is aligned with, or inboard of, the tip of the wing, the swirl ratio decreases to values associated with instability of the vortex, giving rise to enhanced values of azimuthal vorticity relative to the

  8. Flow Measurements of a Plunging Wing in Unsteady Environment

    Science.gov (United States)

    Wengel, Jesse; Nathan, Rungun; Cheng, Bo; Eslam-Panah, Azar

    2017-11-01

    Despite the great progress in their design and control, Unmanned Aerial Vehicles (UAVs) are tremendously troubled while flying in turbulent environments, which are common in the lower atmospheric boundary layer (ABL). A nominally 2D plunging wing was developed and tested in the presence of unsteady wake to investigate the effect of the flow disturbances on vorticity fields. The experiments were conducted in a water channel facility with test section width of 0.76 m, and a water depth of 0.6 m. The unsteady wake in the form of von Kármán Vortex Street was generated by a cylinder located upstream of the plunging wing. The plunge amplitude and frequency of the oscillation were adjusted to bracket the range of Strouhal numbers relevant to the biological locomotion (0.25PIV) was employed to quantitatively study the effect of unsteady wake on the flow measurements of the plunging wing.

  9. Heating and flow-field studies on a straight-wing hypersonic reentry vehicle at angles of attack from 20 to 80 deg with simulation of real-gas trends

    Science.gov (United States)

    Hunt, J. L.

    1973-01-01

    Data are presented from a series of phase-change heat transfer and flow visualization tests at Mach 7.4, 8, and 10.3 in air, Mach 19.5 in nitrogen, Mach 20.3 in helium, and Mach 6 in tetrafluoromethane (CF4) on the windward surface of a straight wing hypersonic reentry configuration for angles of attack from 20 deg to 80 deg. The results indicate that: (1) for hypersonic stream Mach numbers, the flow field over the straight-wing configuration is essentially independent of Mach number, (2) transition Reynolds number decreases with increasing angle of attack, (3) at some critical angle of attack, the wing-shock standoff distance is greatly increased and the stagnation line moves downstream from the wing leading edge, (4) value of the critical angle of attack is very sensitive to the flow shock density ratio or effective gamma, and (5) at angles of attack above the critical value for all gases, the nondimensional level of heat transfer to the wing is higher for the higher shock density ratio flows.

  10. Flow Modulation and Force Control of Flapping Wings

    Science.gov (United States)

    2014-10-29

    tested on a flapping wing model in the oil tank. Robotic flapper equipped with DC motors drove the wing model, and the imbedded servo motor could flap...the overall wake structure on the hovering wings. Totally, two volumetric flow measurements were performed on two mechanical flappers with different...wing kinematics but similar wing geometry. On the flappers with small stroke angle and passive rotation, the general vortex wake structure

  11. Gliding swifts attain laminar flow over rough wings.

    Directory of Open Access Journals (Sweden)

    David Lentink

    Full Text Available Swifts are among the most aerodynamically refined gliding birds. However, the overlapping vanes and protruding shafts of their primary feathers make swift wings remarkably rough for their size. Wing roughness height is 1-2% of chord length on the upper surface--10,000 times rougher than sailplane wings. Sailplanes depend on extreme wing smoothness to increase the area of laminar flow on the wing surface and minimize drag for extended glides. To understand why the swift does not rely on smooth wings, we used a stethoscope to map laminar flow over preserved wings in a low-turbulence wind tunnel. By combining laminar area, lift, and drag measurements, we show that average area of laminar flow on swift wings is 69% (n = 3; std 13% of their total area during glides that maximize flight distance and duration--similar to high-performance sailplanes. Our aerodynamic analysis indicates that swifts attain laminar flow over their rough wings because their wing size is comparable to the distance the air travels (after a roughness-induced perturbation before it transitions from laminar to turbulent. To interpret the function of swift wing roughness, we simulated its effect on smooth model wings using physical models. This manipulation shows that laminar flow is reduced and drag increased at high speeds. At the speeds at which swifts cruise, however, swift-like roughness prolongs laminar flow and reduces drag. This feature gives small birds with rudimentary wings an edge during the evolution of glide performance.

  12. Study of interaction of a pair of longitudinal vortices with a horseshoe vortex around a wing. 2nd Report. Behavior of the interacting flow field controlled passively; Tsubasa mawari no bateikei uzu to tateuzu no kansho ni kansuru kenkyu. 2. Judo seigyosareta nagareba no kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Hara, H. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan); Shizawa, T.; Honami, S. [Science University of Tokyo, Tokyo (Japan). Faculty of Engineering

    1999-12-25

    This paper presents the behavior of a passively controlled horseshoe vortex at the root of NACA0024 wing which is established on a turbulent boundary layer, A pair of vortex generators of half delta wing is installed upstream of the wing. The flow field of the optimally controlled horseshoe vortex both in case of Common Flow Up (CFUC) and Common Flow Down Configuration (CFDC) is carefully investigated by an X-array hot-wire. In case of CFUC, the horseshoe vortex is not shifted from the wing, because the longitudinal vortex is restrained. The interacted vortex presents a circular profile, in a optimally controlled case. In case of CFDC, the interacted vortex that has strong vorticity by the pairing process is shifted away from the wing. Then, the high momentum fluid flow penetrates between the wing and the vortex. (author)

  13. Three-dimensional flow and load characteristics of flexible revolving wings at low Reynolds number

    NARCIS (Netherlands)

    van de Meerendonk, R.; Perçin, M.; van Oudheusden, B.W.

    2016-01-01

    This study explores the flow field and fluid-dynamic loads generated by revolving low-aspect-ratio flat plate wings undergoing a revolving motion starting from rest. Three wings with different degree of chordwise flexural stiffness (i.e., rigid, moderate flexibility and high flexibility) have been

  14. The flow over a 'high' aspect ratio gothic wing at supersonic speeds

    Science.gov (United States)

    Narayan, K. Y.

    1975-01-01

    Results are presented of an experimental investigation on a nonconical wing which supports an attached shock wave over a region of the leading edge near the vertex and a detached shock elsewhere. The shock detachment point is determined from planform schlieren photographs of the flow field and discrepancies are shown to exist between this and the one calculated by applying the oblique shock equations normal to the leading edge. On a physical basis, it is argued that the shock detachment has to obey the two-dimensional law normal to the leading edges. From this, and from other measurements on conical wings, it is thought that the planform schlieren technique may not be particularly satisfactory for detecting shock detachment. Surface pressure distributions are presented and are explained in terms of the flow over related delta wings which are identified as a vertex delta wing and a local delta wing.

  15. Computational Optimization of a Natural Laminar Flow Experimental Wing Glove

    Science.gov (United States)

    Hartshom, Fletcher

    2012-01-01

    Computational optimization of a natural laminar flow experimental wing glove that is mounted on a business jet is presented and discussed. The process of designing a laminar flow wing glove starts with creating a two-dimensional optimized airfoil and then lofting it into a three-dimensional wing glove section. The airfoil design process does not consider the three dimensional flow effects such as cross flow due wing sweep as well as engine and body interference. Therefore, once an initial glove geometry is created from the airfoil, the three dimensional wing glove has to be optimized to ensure that the desired extent of laminar flow is maintained over the entire glove. TRANAIR, a non-linear full potential solver with a coupled boundary layer code was used as the main tool in the design and optimization process of the three-dimensional glove shape. The optimization process uses the Class-Shape-Transformation method to perturb the geometry with geometric constraints that allow for a 2-in clearance from the main wing. The three-dimensional glove shape was optimized with the objective of having a spanwise uniform pressure distribution that matches the optimized two-dimensional pressure distribution as closely as possible. Results show that with the appropriate inputs, the optimizer is able to match the two dimensional pressure distributions practically across the entire span of the wing glove. This allows for the experiment to have a much higher probability of having a large extent of natural laminar flow in flight.

  16. 3-D flow and scour near a submerged wing dike: ADCP measurements on the Missouri River

    Science.gov (United States)

    Jamieson, E.C.; Rennie, C.D.; Jacobson, R.B.; Townsend, R.D.

    2011-01-01

    Detailed mapping of bathymetry and three-dimensional water velocities using a boat-mounted single-beam sonar and acoustic Doppler current profiler (ADCP) was carried out in the vicinity of two submerged wing dikes located in the Lower Missouri River near Columbia, Missouri. During high spring flows the wing dikes become submerged, creating a unique combination of vertical flow separation and overtopping (plunging) flow conditions, causing large-scale three-dimensional turbulent flow structures to form. On three different days and for a range of discharges, sampling transects at 5 and 20 m spacing were completed, covering the area adjacent to and upstream and downstream from two different wing dikes. The objectives of this research are to evaluate whether an ADCP can identify and measure large-scale flow features such as recirculating flow and vortex shedding that develop in the vicinity of a submerged wing dike; and whether or not moving-boat (single-transect) data are sufficient for resolving complex three-dimensional flow fields. Results indicate that spatial averaging from multiple nearby single transects may be more representative of an inherently complex (temporally and spatially variable) three-dimensional flow field than repeated single transects. Results also indicate a correspondence between the location of calculated vortex cores (resolved from the interpolated three-dimensional flow field) and the nearby scour holes, providing new insight into the connections between vertically oriented coherent structures and local scour, with the unique perspective of flow and morphology in a large river.

  17. Computational wing design studies relating to natural laminar flow

    Science.gov (United States)

    Waggoner, Edgar G.

    1986-01-01

    Two research studies are described which directly relate to the application of natural laminar flow (NLF) technology to transonic transport-type wing planforms. Each involved using state-of-the-art computational methods to design three-dimensional wing contours which generate significant runs of favorable pressure gradients. The first study supported the Variable Sweep Transition Flight Experiment and involves design of a full-span glove which extends from the leading edge to the spoiler hinge line on the upper surface of an F-14 outer wing panel. A wing was designed computationally for a corporate transport aircraft in the second study. The resulting wing design generated favorable pressure gradients from the leading edge aft to the mid-chord on both upper and lower surfaces at the cruise design point. Detailed descriptions of the computational design approach are presented along with the various constraints imposed on each of the designs.

  18. Volumetric PIV Behind a Flapping Wing in an Incoming Vortex Flow

    Science.gov (United States)

    Curet, Oscar; Finkel, Cyndee; von Ellenrieder, Karl; Bissell, Daniel

    2013-11-01

    The propulsive surfaces of flying and swimming animals interact with vortices shed by their own bodies or other animals, if they are traveling in groups. The interaction of the propulsive surface with these structured vortices might be fundamental for stability and/or decreasing the cost of transport. In this work, we investigate the wake generated by a flapping wing in an incoming vortex flow. We used a NACA0012 wing model with aspect ratio of 2, and a d-profile cylinder to generated the incoming vortices. The model was tested in a water channel at a Reynolds number of approximately 10,000, which is relevant to many biological swimmers and flyers. The flow structure generated by the flapping wing was measured using three-dimensional Particle Image Velocimetry (3-D PIV). A series of experiments were performed for different Strouhal numbers, St = fL/U, where f is the flapping frequency, L is the amplitude of oscillation, and U is the incoming flow speed. We present the 3-D flow field of the flapping wing in an incoming vortex flow and compare it with the structure of a flapping wing with an undisturbed incoming flow.

  19. Investigation of asymmetry of vortex flow over slender delta wings

    Science.gov (United States)

    Atashbaz, Ghasem

    Vortex flow, a major area of interest in fluid mechanics, is widespread in nature and in many man-made fluid mechanical devices. It can create havoc as cyclones or tornadoes or have significant implications in the performance of turbo-fluid machines or supersonic vehicles and so forth. Asymmetric vortices can cause a loss of lift and increase in rolling moment which can significantly affect wing stability and control. Up until the early nineties, it was generally believed that vortex asymmetry was the result of vortex interactions due to the close proximity of vortices over slender delta wings. However, some recent studies have thrown considerable doubt on the validity of this hypothesis. As a result, wind tunnel investigations were conducted on a series of nine delta wing planforms with sharp and round leading edges to examine the occurrence of vortex asymmetry at different angles of attack and sideslip. The study included surface oil and laser light sheet flow visualization in addition to surface pressure and hot-wire velocity measurements under static conditions. The effects of incidence, sideslip and sweep angles as well as Reynolds number variations were investigated. In this study, it was found that the effect of apex and leading edge shape played an important role in vortex asymmetry generation at high angle of attack. Vortex asymmetry was not observed over slender sharp leading edge delta wings due to the separation point being fixed at the sharp leading edge. Experimental results for these wings showed that the vortices do not impinge on one another because they do not get any closer beyond a certain value of angle of attack. Thus vortex asymmetry was not generated. However, significant vortex asymmetry was observed for round leading-edged delta wings. Asymmetric separation positions over the round leading edge was the result of laminar/turbulent transition which caused vortex asymmetry on these delta wing configurations. Sideslip angle and vortex

  20. Unsteady Flow Interactions Between Pitching Wings In Schooling Arrangements

    Science.gov (United States)

    Kurt, Melike; Moored, Keith

    2017-11-01

    In nature, many fish aggregate into large groups or schools for protection against predators, for social interactions and to save energy during migrations. Regardless of their prime motivation, fish experience three-dimensional flow interactions amongst themselves that can improve or hamper swimming performance and give rise to fluid-mediated forces between individuals. To date, the unsteady, three-dimensional flow interactions among schooling fish remains relatively unexplored. In order to study these interactions, the caudal fins of two interacting fish are idealized as two finite span pitching wings arranged in mixtures of canonical in-line and side-by-side arrangements. The forces and moments acting on the wings in the streamwise and cross-stream directions are quantified as the arrangement and the phase delay between the wings is altered. Particle image velocimetry is employed to characterize the flow physics during high efficiency locomotion. Finally, the forces and flowfields of two-dimensional pitching wings are compared with three-dimensional wings to distinguish how three-dimensionality alters the flow interactions in schools of fish.

  1. A parametric wing design study for a modern laminar flow wing

    Science.gov (United States)

    Koegler, J. A., Jr.

    1979-01-01

    The results of a parametric wing design study using a modern laminar flow airfoil designed to exhibit desirable stall characteristics while maintaining high cruise performance are presented. It was found that little is sacrificed in cruise performance when satisfying the stall margin requirements if a taper ratio of 0.65 or greater is used.

  2. Experimental and computational study of transonic flow about swept wings

    Science.gov (United States)

    Bertelrud, A.; Bergmann, M. Y.; Coakley, T. J.

    1980-01-01

    An experimental investigation of NACA 0010 and 10% circular arc wing models, swept at 45 deg, spanning a channel, and at zero angle of attack is described. Measurements include chordwise and spanwise surface pressure distributions and oil-flow patterns for a range of transonic Mach numbers and Reynolds numbers. Calculations using a new three-dimensional Navier-Stokes code and a two-equation turbulence model are included for the circular-arc wing flow. Reasonable agreement between measurements and computations is obtained.

  3. Automatic analysis and characterization of the hummingbird wings motion using dense optical flow features

    International Nuclear Information System (INIS)

    Martínez, Fabio; Romero, Eduardo; Manzanera, Antoine

    2015-01-01

    A new method for automatic analysis and characterization of recorded hummingbird wing motion is proposed. The method starts by computing a multiscale dense optical flow field, which is used to segment the wings, i.e., pixels with larger velocities. Then, the kinematic and deformation of the wings were characterized as a temporal set of global and local measures: a global angular acceleration as a time function of each wing and a local acceleration profile that approximates the dynamics of the different wing segments. Additionally, the variance of the apparent velocity orientation estimates those wing foci with larger deformation. Finally a local measure of the orientation highlights those regions with maximal deformation. The approach was evaluated in a total of 91 flight cycles, captured using three different setups. The proposed measures follow the yaw turn hummingbird flight dynamics, with a strong correlation of all computed paths, reporting a standard deviation of 0.31 rad/frame 2 and 1.9 (rad/frame) 2 for the global angular acceleration and the global wing deformation respectively. (paper)

  4. EFFECT OF SWEEP ANGLE ON THE VORTICAL FLOW OVER DELTA WINGS AT AN ANGLE OF ATTACK OF 10°

    Directory of Open Access Journals (Sweden)

    JAMES BRETT

    2014-12-01

    Full Text Available CFD simulations have been used to analyse the vortical flows over sharp edged delta wings with differing sweep angles under subsonic conditions at an angle of attack of 10°. RANS simulations were validated against experimental data for a 65° sweep wing, with a flat cross-section, and the steadiness of the flow field was assessed by comparing the results against unsteady URANS and DES simulations. To assess the effect of sweep angle on the flow field, a range of sweep angles from 65° to 43° were simulated. For moderate sweep wings the primary vortex was observed to detach from the leading edge, undergoing vortex breakdown, and a weaker, replacement, "shadow" vortex was formed. The shadow vortex was observed for sweep angles of 50° and less, and resulted in reduced lift production near the wing tips loss of the stronger primary vortex.

  5. Electro-Magnetic Flow Control to Enable Natural Laminar Flow Wings Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This research team has developed a solid-state electromagnetic device that, when embedded along the leading edge of an aircraft wing, can disrupt laminar air flow on...

  6. Electro-Magnetic Flow Control to Enable Natural Laminar Flow Wings

    Data.gov (United States)

    National Aeronautics and Space Administration — This research team has developed a solid-state electromagnetic device that, when embedded along the leading edge of an aircraft wing, can disrupt laminar air flow on...

  7. Effect of delta wing on the particle flow in a novel gas supersonic separator

    DEFF Research Database (Denmark)

    Wen, Chuang; Yang, Yan; Walther, Jens Honore

    2016-01-01

    The present work presents numerical simulations of the complex particle motion in a supersonic separator with a delta wing located in the supersonic flow. The effect of the delta wing on the strong swirling flow is analysed using the Discrete Particle Method. The results show that the delta wings...... re-compress the upstream flow and the gas Mach number decreases correspondingly. However, the Mach number does not vary significantly from the small, medium and large delta wing configurations. The small delta wing generates a swirl near its surface, but has minor influences on the flow above it....... On the contrary, the use of the large delta wing produces a strong swirling flow in the whole downstream region. For the large delta wing, the collection efficiency reaches 70% with 2 μm particles, indicating a good separation performance of the proposed supersonic separator....

  8. Three-Dimensional Unsteady Flow Elicited by Finite Wings and Complex Configurations.

    Science.gov (United States)

    1987-01-01

    flow. Anemometric measurements added quantitative magnitudes and spatial verification to the visualized flow structures. The experiments were designed... anemometric measurements were taken at each span location and chordwise at 0.00c(leading edge), 0.17c, 0.33c, 0.50c, 0.67c, 0.83c and 1.00c. " An X...The hot wire recorded the absolute velocity of the flow field during the cyclic motion history of the three wings. The anemometric measurements were

  9. Analysis of Low Speed Stall Aerodynamics of a Swept Wing with Laminar Flow Glove

    Science.gov (United States)

    Bui, Trong T.

    2014-01-01

    Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) analysis was conducted to study the low-speed stall aerodynamics of a GIII aircraft's swept wing modified with a laminar-flow wing glove. The stall aerodynamics of the gloved wing were analyzed and compared with the unmodified wing for the flight speed of 120 knots and altitude of 2300 ft above mean sea level (MSL). The Star-CCM+ polyhedral unstructured CFD code was first validated for wing stall predictions using the wing-body geometry from the First American Institute of Aeronautics and Astronautics (AIAA) CFD High-Lift Prediction Workshop. It was found that the Star-CCM+ CFD code can produce results that are within the scattering of other CFD codes considered at the workshop. In particular, the Star-CCM+ CFD code was able to predict wing stall for the AIAA wing-body geometry to within 1 degree of angle of attack as compared to benchmark wind-tunnel test data. Current results show that the addition of the laminar-flow wing glove causes the gloved wing to stall much earlier than the unmodified wing. Furthermore, the gloved wing has a different stall characteristic than the clean wing, with no sharp lift drop-off at stall for the gloved wing.

  10. Analysis of Low-Speed Stall Aerodynamics of a Swept Wing with Laminar-Flow Glove

    Science.gov (United States)

    Bui, Trong T.

    2014-01-01

    Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) analysis was conducted to study the low-speed stall aerodynamics of a GIII aircraft's swept wing modified with a laminar-flow wing glove. The stall aerodynamics of the gloved wing were analyzed and compared with the unmodified wing for the flight speed of 120 knots and altitude of 2300 ft above mean sea level (MSL). The Star-CCM+ polyhedral unstructured CFD code was first validated for wing stall predictions using the wing-body geometry from the First American Institute of Aeronautics and Astronautics (AIAA) CFD High-Lift Prediction Workshop. It was found that the Star-CCM+ CFD code can produce results that are within the scattering of other CFD codes considered at the workshop. In particular, the Star-CCM+ CFD code was able to predict wing stall for the AIAA wing-body geometry to within 1 degree of angle of attack as compared to benchmark wind-tunnel test data. Current results show that the addition of the laminar-flow wing glove causes the gloved wing to stall much earlier than the unmodified wing. Furthermore, the gloved wing has a different stall characteristic than the clean wing, with no sharp lift drop-off at stall for the gloved wing.

  11. Wind Tunnel Test of a Risk-Reduction Wing/Fuselage Model to Examine Juncture-Flow Phenomena

    Science.gov (United States)

    Kegerise, Michael A.; Neuhart, Dan H.

    2016-01-01

    A wing/fuselage wind-tunnel model was tested in the Langley 14- by 22-foot Subsonic Wind Tunnel in preparation for a highly-instrumented Juncture Flow Experiment to be conducted in the same facility. This test, which was sponsored by the NASA Transformational Tool and Technologies Project, is part of a comprehensive set of experimental and computational research activities to develop revolutionary, physics-based aeronautics analysis and design capability. The objectives of this particular test were to examine the surface and off-body flow on a generic wing/body combination to: 1) choose a final wing for a future, highly instrumented model, 2) use the results to facilitate unsteady pressure sensor placement on the model, 3) determine the area to be surveyed with an embedded laser-doppler velocimetry (LDV) system, 4) investigate the primary juncture corner- flow separation region using particle image velocimetry (PIV) to see if the particle seeding is adequately entrained and to examine the structure in the separated region, and 5) to determine the similarity of observed flow features with those predicted by computational fluid dynamics (CFD). This report documents the results of the above experiment that specifically address the first three goals. Multiple wing configurations were tested at a chord Reynolds number of 2.4 million. Flow patterns on the surface of the wings and in the region of the wing/fuselage juncture were examined using oil- flow visualization and infrared thermography. A limited number of unsteady pressure sensors on the fuselage around the wing leading and trailing edges were used to identify any dynamic effects of the horseshoe vortex on the flow field. The area of separated flow in the wing/fuselage juncture near the wing trailing edge was observed for all wing configurations at various angles of attack. All of the test objectives were met. The staff of the 14- by 22-foot Subsonic Wind Tunnel provided outstanding support and delivered

  12. A further note on the force discrepancy for wing theory in Euler flow

    Indian Academy of Sciences (India)

    As in the two previous papers by the authors on wing theory in Euler flow [E Chadwick, ... It is over 250 years since Euler presented the Euler equations for fluid flow [11], and they have proven extraordinarily ... dard aerodynamic theory for flow past wings, a further assumption is made by supposing a discontinuous trailing ...

  13. Material development for laminar flow control wing panels

    Science.gov (United States)

    Meade, L. E.

    1977-01-01

    The absence of suitable porous materials or techniques for the economic perforation of surface materials has previously restricted the design of laminar flow control (LFC) wing panels to a consideration of mechanically slotted LFC surfaces. A description is presented of a program which has been conducted to exploit recent advances in materials and manufacturing technology for the fabrication of reliable porous or perforated LFC surface panels compatible with the requirements of subsonic transport aircraft. Attention is given to LFC design criteria, surface materials, surface concepts, the use of microporous composites, perforated composites, and perforated metal. The described program was successful in that fabrication processes were developed for producing predictable perforated panels both of composite and of metal.

  14. Supersonic vortex breakdown over a delta wing in transonic flow

    Science.gov (United States)

    Kandil, Hamdy A.; Kandil, Osama A.; Liu, C. H.

    1993-01-01

    The effects of freestream Mach number and angle of attack on the leading-edge vortex breakdown due to the terminating shock on a 65-degree, sharp-edged, cropped delta wing are investigated computationally, using the time-accurate solution of the laminar unsteady compressible full Navier-Stokes equations with the implicit upwind flux-difference splitting, finite-volume scheme. A fine O-H grid consisting of 125 x 85 x 84 points in the wrap-around, normal, and axial directions, respectively, is used for all the flow cases. Keeping the Reynolds number fixed at 3.23 x 10 exp 6, the Mach number is varied from 0.85 to 0.9 and the angle of attack is varied from 20 to 24 deg. The results show that, at 20-deg angle of attack, the increase of the Mach number from 0.85 to 0.9 results in moving the location of the terminating shock downstream. The results also show that, at 0.85 Mach number, the increase of the angle of attack from 20 to 24 deg results in moving the location of the terminating shock upstream. The results are in good agreement with the experimental data.

  15. Air Forces and Moments on Triangular and Related Wings With Subsonic Leading Edges Oscillating in Supersonic Potential Flow

    National Research Council Canada - National Science Library

    Watkins, Charles

    1961-01-01

    This analysis treats the air forces and moments in supersonic potential flow on oscillating triangular wings and a series of sweptback and arrow wings with subsonic leading edges and supersonic trailing edges...

  16. Experimental and Computational Study of the Flow past a Simplified Geometry of an Engine/Pylon/Wing Installation at low velocity/moderate incidence flight conditions

    Science.gov (United States)

    Bury, Yannick; Lucas, Matthieu; Bonnaud, Cyril; Joly, Laurent; ISAE Team; Airbus Team

    2014-11-01

    We study numerically and experimentally the vortices that develop past a model geometry of a wing equipped with pylon-mounted engine at low speed/moderate incidence flight conditions. For such configuration, the presence of the powerplant installation under the wing initiates a complex, unsteady vortical flow field at the nacelle/pylon/wing junctions. Its interaction with the upper wing boundary layer causes a drop of aircraft performances. In order to decipher the underlying physics, this study is initially conducted on a simplified geometry at a Reynolds number of 200000, based on the chord wing and on the freestream velocity. Two configurations of angle of attack and side-slip angle are investigated. This work relies on unsteady Reynolds Averaged Navier Stokes computations, oil flow visualizations and stereoscopic Particle Image Velocimetry measurements. The vortex dynamics thus produced is described in terms of vortex core position, intensity, size and turbulent intensity thanks to a vortex tracking approach. In addition, the analysis of the velocity flow fields obtained from PIV highlights the influence of the longitudinal vortex initiated at the pylon/wing junction on the separation process of the boundary layer near the upper wing leading-edge.

  17. Study on flow over finite wing with respect to F-22 raptor, Supermarine Spitfire, F-7 BG aircraft wing and analyze its stability performance and experimental values

    Science.gov (United States)

    Ali, Md. Nesar; Alam, Mahbubul

    2017-06-01

    A finite wing is a three-dimensional body, and consequently the flow over the finite wing is three-dimensional; that is, there is a component of flow in the span wise direction. The physical mechanism for generating lift on the wing is the existence of a high pressure on the bottom surface and a low pressure on the top surface. The net imbalance of the pressure distribution creates the lift. As a by-product of this pressure imbalance, the flow near the wing tips tends to curl around the tips, being forced from the high-pressure region just underneath the tips to the low-pressure region on top. This flow around the wing tips is shown in the front view of the wing. As a result, on the top surface of the wing, there is generally a span wise component of flow from the tip toward the wing root, causing the streamlines over the top surface to bend toward the root. On the bottom surface of the wing, there is generally a span wise component of flow from the root toward the tip, causing the streamlines over the bottom surface to bend toward the tip. Clearly, the flow over the finite wing is three-dimensional, and therefore we would expect the overall aerodynamic properties of such a wing to differ from those of its airfoil sections. The tendency for the flow to "leak" around the wing tips has another important effect on the aerodynamics of the wing. This flow establishes a circulatory motion that trails downstream of the wing; that is, a trailing vortex is created at each wing tip. The aerodynamics of finite wings is analyzed using the classical lifting line model. This simple model allows a closed-form solution that captures most of the physical effects applicable to finite wings. The model is based on the horseshoe-shaped vortex that introduces the concept of a vortex wake and wing tip vortices. The downwash induced by the wake creates an induced drag that did not exist in the two-dimensional analysis. Furthermore, as wingspan is reduced, the wing lift slope decreases

  18. Supersonic flow over a pitching delta wing using surface pressure measurements and numerical simulations

    Directory of Open Access Journals (Sweden)

    Mostafa HADIDOOLABI

    2018-01-01

    Full Text Available Experimental and numerical methods were applied to investigating high subsonic and supersonic flows over a 60° swept delta wing in fixed state and pitching oscillation. Static pressure coefficient distributions over the wing leeward surface and the hysteresis loops of pressure coefficient versus angle of attack at the sensor locations were obtained by wind tunnel tests. Similar results were obtained by numerical simulations which agreed well with the experiments. Flow structure around the wing was also demonstrated by the numerical simulation. Effects of Mach number and angle of attack on pressure distribution curves in static tests were investigated. Effects of various oscillation parameters including Mach number, mean angle of attack, pitching amplitude and frequency on hysteresis loops were investigated in dynamic tests and the associated physical mechanisms were discussed. Vortex breakdown phenomenon over the wing was identified at high angles of attack using the pressure coefficient curves and hysteresis loops, and its effects on the flow features were discussed.

  19. Hydrodynamic characteristics for flow around wavy wings with different wave lengths

    Directory of Open Access Journals (Sweden)

    Mi Jeong Kim

    2012-12-01

    Full Text Available The present study numerically investigates the effect of the wavy leading edge on hydrodynamic characteristics for the flow of rectangular wings with the low aspect ratio of 1.5. Five different wave lengths at fixed wavy amplitude have been considered. Numerical simulations are performed at a wide range of the angle of attack (0° ≤α ≤ 40° at one Reynolds number of 106. The wavy wings considered in this study did not experience enough lift drop to be defined as the stall, comparing with the smooth wing. However, in the pre-stall region, the wavy wings reveal the considerable loss of the lift, compared to the smooth wing. In the post-stall, the lift coefficients of the smooth wing and the wavy wings are not much different. The pressure coefficient, limiting streamlines and the iso-surface of the spanwise vorticity are also highlighted to examine the effect of the wave length on the flow structures.

  20. Flow cytometry determination of ploidy level in winged bean ...

    African Journals Online (AJOL)

    Ploidy determination and mutation breeding of crop plants are inseparable twins given that mutation breeding is hinged majorly on polyploidization of crop's chromosome number. The present research was aimed at determining the ploidy level of 20 accessions of winged bean (Psophoscarpus tetragonolobus) using known ...

  1. Ground vortex flow field investigation

    Science.gov (United States)

    Kuhn, Richard E.; Delfrate, John H.; Eshleman, James E.

    1988-01-01

    Flow field investigations were conducted at the NASA Ames-Dryden Flow Visualization Facility (water tunnel) to investigate the ground effect produced by the impingement of jets from aircraft nozzles on a ground board in a STOL operation. Effects on the overall flow field with both a stationary and a moving ground board were photographed and compared with similar data found in other references. Nozzle jet impingement angles, nozzle and inlet interaction, side-by-side nozzles, nozzles in tandem, and nozzles and inlets mounted on a flat plate model were investigated. Results show that the wall jet that generates the ground effect is unsteady and the boundary between the ground vortex flow field and the free-stream flow is unsteady. Additionally, the forward projection of the ground vortex flow field with a moving ground board is one-third less than that measured over a fixed ground board. Results also showed that inlets did not alter the ground vortex flow field.

  2. Flow over 50º Delta Wings with Different Leading-Edge Radii

    NARCIS (Netherlands)

    Verhaagen, N.G.

    2011-01-01

    The experimental study focuses on the effects of the leading-edge radius on the flow over 50º swept delta wing models. Three models were tested, one model has a sharp leading edge and two other have a semi-circular leading edge of different radius. The vortical flow on and off the surface of the

  3. Europa's Alfvén wing: shrinkage and displacement influenced by an induced magnetic field

    Directory of Open Access Journals (Sweden)

    M. Volwerk

    2007-05-01

    Full Text Available The Galileo magnetometer data are used to investigate the structure of the Alfvén wing during three flybys of Europa. The presence of an induced magnetic field is shown to shrink the cross section of the Alfvén wing and offset it along the direction radial to Jupiter. Both the shrinkage and the offset depend on the strength of the induced field. The entry and exit points of the spacecraft into and out of the Alfvén wings are modeled to determine the angle between the wings and the background magnetic field. Tracing of the Alfvén characteristics in a model magnetic field consisting of Jupiter's background field and an induced field in Europa produces an offset and shrinking of the Alfvén wing consistent with the geometric modeling. Thus we believe that the Alfvén wing properties have been determined correctly. The Alfvén wing angle is directly proportional to the local Alfvén velocity, and is thus a probe for the local plasma density. We show that the inferred plasma density can be understood in terms of the electron density measured by the plasma wave experiment. When Europa is located in the Jovian plasma sheet the derived mass-per-charge exceeds the previous estimates, which is a result of increased pickup of sputtered ions near the moon. The estimated rate of O2+ pickup agrees well with the results from numerical models.

  4. CFD simulations of steady flows over the IAR 65o delta wing

    International Nuclear Information System (INIS)

    Benmeddour, A.; Mebarki, Y.; Huang, X.Z.

    2004-01-01

    Computational Fluid Dynamics (CFD) studies have been conducted to simulate vortical flows around the IAR 65 o delta wing with a sharp leading edge. The effects of the centerbody on the aerodynamic characteristics of the wing are also investigated. Two flow solvers have been employed to compute steady inviscid flows over with and without centerbody configurations of the wing. These two solvers are an IAR in-house code, FJ3SOLV, and the CFD-FASTRAN commercial software. The computed flow solutions of the two solvers have been compared and correlated against the IAR wind tunnel data, including Pressure Sensitive Paint (PSP) measurements. The major features of the primary vortex have been well captured and overall reasonable accuracy was obtained. In accordance with the experimental observations for the flow conditions considered, the CFD computations revealed no major global effects of the centerbody on the surface pressure distributions of the wing and on the lift coefficient. However, CFD-FASTRAN seems to predict a vortex breakdown, which is neither predicted by FJ3SOLV nor observed in the wind tunnel for the flow conditions considered. (author)

  5. Computational Design and Analysis of a Transonic Natural Laminar Flow Wing for a Wind Tunnel Model

    Science.gov (United States)

    Lynde, Michelle N.; Campbell, Richard L.

    2017-01-01

    A natural laminar flow (NLF) wind tunnel model has been designed and analyzed for a wind tunnel test in the National Transonic Facility (NTF) at the NASA Langley Research Center. The NLF design method is built into the CDISC design module and uses a Navier-Stokes flow solver, a boundary layer profile solver, and stability analysis and transition prediction software. The NLF design method alters the pressure distribution to support laminar flow on the upper surface of wings with high sweep and flight Reynolds numbers. The method addresses transition due to attachment line contamination/transition, Gortler vortices, and crossflow and Tollmien-Schlichting modal instabilities. The design method is applied to the wing of the Common Research Model (CRM) at transonic flight conditions. Computational analysis predicts significant extents of laminar flow on the wing upper surface, which results in drag savings. A 5.2 percent scale semispan model of the CRM NLF wing will be built and tested in the NTF. This test will aim to validate the NLF design method, as well as characterize the laminar flow testing capabilities in the wind tunnel facility.

  6. Visualization of Flow Field of Weis-Fogh Type Water Turbine Using the PIV

    Energy Technology Data Exchange (ETDEWEB)

    Ro, Ki Deok [Gyeongsang Nat’l Univ., Jinju (Korea, Republic of)

    2017-03-15

    In this study, the visualization of the unsteady flow field of a Weis-Fogh-type water turbine was investigated using particle-image velocimetry. The visualization experiments were performed in a parameter range that provided relatively high-efficiency wing conditions, that is, at a wing opening angle α= 40 .deg. and at a velocity ratio of the uniform flow to the moving wing U/V = 1.5~2.5. The flow fields at the opening, translational, and closing stages were investigated for each experimental parameter. In the opening stage, the fluid was drawn in between the wing and wall at a velocity that increased with an increase in the opening angle and velocity ratio. In the translational stage, the fluid on the pressure face of the wing moved in the direction of the wing motion, and the boundary layer at the back face of the wing was the thinnest and had a velocity ratio of 2.0. In the closing stage, the fluid between the wing and wall was jetted at a velocity that increased as the opening angle decreased; however, the velocity was independent of the velocity ratio.

  7. Sound radiation and wing mechanics in stridulating field crickets (Orthoptera: Gryllidae).

    Science.gov (United States)

    Montealegre-Z, Fernando; Jonsson, Thorin; Robert, Daniel

    2011-06-15

    Male field crickets emit pure-tone mating calls by rubbing their wings together. Acoustic radiation is produced by rapid oscillations of the wings, as the right wing (RW), bearing a file, is swept across the plectrum borne on the left wing (LW). Earlier work found the natural resonant frequency (f(o)) of individual wings to be different, but there is no consensus on the origin of these differences. Previous studies suggested that the frequency along the song pulse is controlled independently by each wing. It has also been argued that the stridulatory file has a variable f(o) and that the frequency modulation observed in most species is associated with this variability. To test these two hypotheses, a method was developed for the non-contact measurement of wing vibrations during singing in actively stridulating Gryllus bimaculatus. Using focal microinjection of the neuroactivator eserine into the cricket's brain to elicit stridulation and micro-scanning laser Doppler vibrometry, we monitored wing vibration in actively singing insects. The results show significantly lower f(o) in LWs compared with RWs, with the LW f(o) being identical to the sound carrier frequency (N=44). But during stridulation, the two wings resonate at one identical frequency, the song carrier frequency, with the LW dominating in amplitude response. These measurements also demonstrate that the stridulatory file is a constant resonator, as no variation was observed in f(o) along the file during sound radiation. Our findings show that, as they engage in stridulation, cricket wings work as coupled oscillators that together control the mechanical oscillations generating the remarkably pure species-specific song.

  8. An Experimental Investigation of Flow past a Wing at high Angles of Attack

    Science.gov (United States)

    Dalela, Vipul; Mukherjee, Rinku

    2017-11-01

    The aerodynamic characteristics for post-stall angles of attack past a single and/or multiple 3D wing(s) have been studied using a novel `decambering technique' assuming the flow to be steady. It is expected that the location of separation as well as the strength of the separated flow is unsteady. The objective of this work therefore is to investigate flow at high angles of attack considering unsteady behavior. The numerical technique used for this purpose that accounts for loss in camber due to flow separation is termed as `decambering'. Two linear functions are used to define the `decambering' for the steady case, located at the leading edge and anywhere between 50%-80% chord. Wind tunnel experiments are to be conducted to study the unsteady nature of separated flow using flow visualization techniques. An estimation of the unsteady wake will be of paramount importance. It is expected to get an experimental corroboration for the numerical decambering. A NACA 4415 wing section is being tested for a range of Reynolds numbers. It is observed from the preliminary results that the drag becomes more dominant after increasing the Reynolds number from Re = 0.093 ×106 to Re = 0.128 ×106 resulting a gentle decrease in the lift coefficient, Cl.

  9. Aphid wing induction and ecological costs of alarm pheromone emission under field conditions.

    Directory of Open Access Journals (Sweden)

    Eduardo Hatano

    2010-06-01

    Full Text Available The pea aphid, Acyrthosiphon pisum Harris, (Homoptera: Aphididae releases the volatile sesquiterpene (E-beta-farnesene (EBF when attacked by a predator, triggering escape responses in the aphid colony. Recently, it was shown that this alarm pheromone also mediates the production of the winged dispersal morph under laboratory conditions. The present work tested the wing-inducing effect of EBF under field conditions. Aphid colonies were exposed to two treatments (control and EBF and tested in two different environmental conditions (field and laboratory. As in previous experiments aphids produced higher proportion of winged morphs among their offspring when exposed to EBF in the laboratory but even under field conditions the proportion of winged offspring was higher after EBF application (6.84+/-0.98% compared to the hexane control (1.54+/-0.25%. In the field, the proportion of adult aphids found on the plant at the end of the experiment was lower in the EBF treatment (58.1+/-5.5% than in the control (66.9+/-4.6%, in contrast to the climate chamber test where the numbers of adult aphids found on the plant at the end of the experiment were, in both treatments, similar to the numbers put on the plant initially. Our results show that the role of EBF in aphid wing induction is also apparent under field conditions and they may indicate a potential cost of EBF emission. They also emphasize the importance of investigating the ecological role of induced defences under field conditions.

  10. Nacelle/pylon/wing integration on a transport model with a natural laminar flow nacelle

    Science.gov (United States)

    Lamb, M.; Aabeyounis, W. K.; Patterson, J. C., Jr.

    1985-01-01

    Tests were conducted in the Langley 16-Foot Transonic Tunnel at free-stream Mach numbers from 0.70 to 0.82 and angles of attack from -2.5 deg to 4.0 deg to determine if nacelle/pylon/wing integration affects the achievement of natural laminar flow on a long-duct flow-through nacelle for a high-wing transonic transport configuration. In order to fully assess the integration effect on a nacelle designed to achieve laminar flow, the effects of fixed and free nacelle transitions as well as nacelle longitudinal position and pylon contouring were obtained. The results indicate that the ability to achieve laminar flow on the nacelle is not significantly altered by nacelle/pylon/wing integration. The increment in installed drag between free and fixed transition for the nacelles on symmetrical pylons is essentially the calculated differences between turbulent and laminar flow on the nacelles. The installed drag of the contoured pylon is less than that of the symmetrical pylon. The installed drag for the nacelles in a rearward position is greater than that for the nacelles in a forward position.

  11. Flow interactions lead to orderly formations of flapping wings in forward flight

    Science.gov (United States)

    Ramananarivo, Sophie; Fang, Fang; Oza, Anand; Zhang, Jun; Ristroph, Leif

    2016-11-01

    Classic models of fish schools and flying formations of birds are built on the hypothesis that the preferred locations of an individual are determined by the flow left by its upstream neighbor. Lighthill posited that arrangements may in fact emerge passively from hydro- or aerodynamic interactions, drawing an analogy to the formation of crystals by intermolecular forces. Here, we carry out physical experiments aimed at testing the Lighthill conjecture and find that self-propelled flapping wings spontaneously assume one of multiple arrangements due to flow interactions. Wings in a tandem pair select the same forward speed, which tends to be faster than a single wing, while maintaining a separation distance that is an integer multiple of the wavelength traced out by each body. When perturbed, these locomotors robustly return to the same arrangement, and direct hydrodynamic force measurements reveal springlike restoring forces that maintain group cohesion. We also use these data to construct an interaction potential, showing how the observed positions of the follower correspond to stable wells in an energy landscape. Flow visualization and vortex-based theoretical models reveal coherent interactions in which the follower surfs on the periodic wake left by the leader. These results indicate that, for the high-Reynolds-number flows characteristic of schools and flocks, collective locomotion at enhanced speed and in orderly formations can emerge from flow interactions alone. If true for larger groups, then the view of collectives as ordered states of matter may prove to be a useful analogy.

  12. Comparison of Experimental Surface and Flow Field Measurements to Computational Results of the Juncture Flow Model

    Science.gov (United States)

    Roozeboom, Nettie H.; Lee, Henry C.; Simurda, Laura J.; Zilliac, Gregory G.; Pulliam, Thomas H.

    2016-01-01

    Wing-body juncture flow fields on commercial aircraft configurations are challenging to compute accurately. The NASA Advanced Air Vehicle Program's juncture flow committee is designing an experiment to provide data to improve Computational Fluid Dynamics (CFD) modeling in the juncture flow region. Preliminary design of the model was done using CFD, yet CFD tends to over-predict the separation in the juncture flow region. Risk reduction wind tunnel tests were requisitioned by the committee to obtain a better understanding of the flow characteristics of the designed models. NASA Ames Research Center's Fluid Mechanics Lab performed one of the risk reduction tests. The results of one case, accompanied by CFD simulations, are presented in this paper. Experimental results suggest the wall mounted wind tunnel model produces a thicker boundary layer on the fuselage than the CFD predictions, resulting in a larger wing horseshoe vortex suppressing the side of body separation in the juncture flow region. Compared to experimental results, CFD predicts a thinner boundary layer on the fuselage generates a weaker wing horseshoe vortex resulting in a larger side of body separation.

  13. Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect

    International Nuclear Information System (INIS)

    Truong, Tien Van; Yoon, Kwang Joon; Byun, Doyoung; Kim, Min Jun; Park, Hoon Cheol

    2013-01-01

    The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff

  14. Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect.

    Science.gov (United States)

    Van Truong, Tien; Byun, Doyoung; Kim, Min Jun; Yoon, Kwang Joon; Park, Hoon Cheol

    2013-09-01

    The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff.

  15. Adaptive computations of flow around a delta wing with vortex breakdown

    Science.gov (United States)

    Modiano, David L.; Murman, Earll M.

    1993-01-01

    An adaptive unstructured mesh solution method for the three-dimensional Euler equations was used to simulate the flow around a sharp edged delta wing. Emphasis was on the breakdown of the leading edge vortex at high angle of attack. Large values of entropy, which indicate vortical regions of the flow, specified the region in which adaptation was performed. The aerodynamic normal force coefficients show excellent agreement with wind tunnel data measured by Jarrah, and demonstrate the importance of adaptation in obtaining an accurate solution. The pitching moment coefficient and the location of vortex breakdown are compared with experimental data measured by Hummel and Srinivasan, showing good agreement in cases in which vortex breakdown is located over the wing.

  16. Flow around a corrugated wing over the range of dragonfly flight

    Science.gov (United States)

    Padinjattayil, Sooraj; Agrawal, Amit

    2017-11-01

    The dragonfly flight is very much affected by the corrugations on their wings. A PIV based study is conducted on a rigid corrugated wing for a range of Reynolds number 300-12000 and three different angles of attack (5°-15°) to understand the mechanism of dragonfly flight better. The study revealed that the shape of the corrugation plays a key role in generating vortices. The vortices trapped in the valleys of corrugation dictates the shape of a virtual airfoil around the corrugated wing. A fluid roller bearing effect is created over the virtual airfoil when the trapped vortices merge with each other. A travelling wave produced by the moving virtual boundary around the fluid roller bearings avoids the formation of boundary layer on the virtual surface, thereby leading to high aerodynamic performance. It is found that the lift coefficient increases as the number of vortices increases on the suction surface. Also, it is shown that the partially merged co- rotating vortices give higher lift as compared to fully merged vortices. Further, the virtual airfoil formed around the corrugated wing is compared with a superhydrophobic airfoil which exhibits slip on its surface; several similarities in their flow characteristics are observed. The corrugated airfoil performs superior to the superhydrophobic airfoil in the aerodynamic efficiency due to the virtual slip caused by the travelling wave.

  17. Flow-around modes for a rhomboid wing with a stall vortex in the shock layer

    Science.gov (United States)

    Zubin, M. A.; Maximov, F. A.; Ostapenko, N. A.

    2017-12-01

    The results of theoretical and experimental investigation of an asymmetrical hypersonic flow around a V-shaped wing with the opening angle larger than π on the modes with attached shockwaves on forward edges, when the stall flow is implemented on the leeward wing cantilever behind the kink point of the cross contour. In this case, a vortex of nonviscous nature is formed in which the velocities on the sphere exceeding the speed of sound and resulting in the occurrence of pressure shocks with an intensity sufficient for the separation of the turbulent boundary layer take place in the reverse flow according to the calculations within the framework of the ideal gas. It is experimentally established that a separation boundary layer can exist in the reverse flow, and its structure is subject to the laws inherent to the reverse flow in the separation region of the turbulent boundary layer arising in the supersonic conic flow under the action of a shockwave incident to the boundary layer.

  18. Flow field analysis for a class of waverider configurations

    Science.gov (United States)

    Moitra, Anutosh

    1990-01-01

    A package of computer codes for analysis of flow fields for waverider configurations is described. The package consists of a surface/volume grid generator and a finite-volume flow solver. The grid generator defines body geometries and computational grids by an algebraic homotopy procedure. The algebraic procedure is versatile in its application and can readily generate configurations in the class of blended wing-body geometries. This code has the ability to produce a wide variety of geometries in the given class with varying geometrical attributes. The flow solver employs a finite-volume formation and solves the explicit, Runge-Kutta integration technique. The method or flow simulation incorporates several techniques for acceleration of the convergence of the interaction process and an entropy corrected enthalpy damping procedure for efficient computation of high Mach number flows.

  19. Forced Rolling Oscillation of a 65 deg-Delta Wing in Transonic Vortex-Breakdown Flow

    Science.gov (United States)

    Menzies, Margaret A.; Kandil, Osama A.; Kandil, Hamdy A.

    1996-01-01

    Unsteady, transonic, vortex dominated flow over a 65 deg. sharp-edged, cropped-delta wing of zero thickness undergoing forced rolling oscillations is investigated computationally. The wing angle of attack is 20 deg. and the free stream Mach number and Reynolds number are 0.85 and 3.23 x 10(exp 6), respectively. The initial condition of the flow is characterized by a transverse terminating shock which induces vortex breakdown of the leading edge vortex cores. The computational investigation uses the time accurate solution of the laminar, unsteady, compressible, full Navier-Stokes equations with the implicit, upwind, Roe flux difference splitting, finite-volume scheme. While the maximum roll amplitude is kept constant at 4.0 deg., both Reynolds number and roll frequency are varied covering three cases of forced sinusoidal rolling. First, the Reynolds number is held at 3.23 x 10(exp 6) and the wing is forced to oscillate in roll around the axis of geometric symmetry at a reduced frequency of 2(pi). Second, the Reynolds number is reduced to 0.5 x 10(exp 6) to observe the effects of added viscosity on the vortex breakdown. Third, with the Reynolds number held at 0.5 x 10(exp 6), the roll frequency is reduced to 1(pi) to complete the study.

  20. Simulation of wing-body junction flows with hybrid RANS/LES methods

    International Nuclear Information System (INIS)

    Fu Song; Xiao Zhixiang; Chen Haixin; Zhang Yufei; Huang Jingbo

    2007-01-01

    In this paper, flows past two wing-body junctions, the Rood at zero angle of attack and NASA TN D-712 at 12.5 o angle of attack, are investigated with two Reynolds-Averaged Navier-Stokes (RANS) and large eddy simulation (LES) hybrid methods. One is detached eddy simulation (DES) and the other is delayed-DES, both are based on a weakly nonlinear two-equation k-ω model. While the RANS method can predict the mean flow behaviours reasonably accurately, its performance for the turbulent kinetic energy and shear stress, as compared with available experimental data, is not satisfactory. DES, through introducing a length scale in the dissipation terms of the turbulent kinetic energy equation, delivers flow separation, a vortex or the onset of vortex breakdown too early. DDES, with its delayed effect, shows a great improvement in flow structures and turbulence characteristics, and agrees well with measurements

  1. A three-dimensional viscous/potential flow interaction analysis method for multi-element wings

    Science.gov (United States)

    Dvorak, F. A.; Woodward, F. A.; Maskew, B.

    1977-01-01

    An analysis method and computer program were developed for the calculation of the viscosity dependent aerodynamic characteristics of multi-element, finite wings in incompressible flow. A fully-three dimensional potential flow program is used to determine the inviscid pressure distribution about the configuration. The potential flow program uses surface source and vortex singularities to represent the inviscid flow. The method is capable of analysing configurations having at most one slat, a main element, and two slotted flaps. Configurations are limited to full span slats or flaps. The configuration wake is allowed to relax as a force free wake, although roll up is not allowed at this time. Once the inviscid pressure distribution is calculated, a series of boundary layer computations are made along streamwise strips.

  2. Flow structures in end-view plane of slender delta wing

    Directory of Open Access Journals (Sweden)

    Sahin Besir

    2017-01-01

    Full Text Available Present investigation focuses on unsteady flow structures in end-view planes at the trailing edge of delta wing, X/C=1.0, where consequences of vortex bursting and stall phenomena vary according to angles of attack over the range of 25° ≤ α ≤ 35° and yaw angles, β over the range of 0° ≤ β ≤ 20°. Basic features of counter rotating vortices in end-view planes of delta win with 70° sweep angle, Λ are examined both qualitatively and quantitatively using Rhodamine dye and the PIV system. In the light of present experiments it is seen that with increasing yaw angle, β symmetrical flow structure is disrupted continuously. Dispersed wind-ward side leading edge vortices cover a large part of flow domain, on the other hand, lee-ward side leading edge vortices cover only a small portion of flow domain.

  3. Experimental Investigation of Pitch Control Enhancement to the Flapping Wing Micro Air Vehicle

    National Research Council Canada - National Science Library

    Kian, Chin C

    2006-01-01

    .... The MAV without the main fixed-wing is placed in a laminar flow field within a low speed wind tunnel with the wake after the flapping wings characterized with a constant temperature anemometer...

  4. Blowing jets as a circulation flow control to enhancement the lift of wing or generated power of wind turbine

    Directory of Open Access Journals (Sweden)

    Alexandru DUMITRACHE

    2014-06-01

    Full Text Available The goal of this paper is to provide a numerical flow analysis based on RANS equations in two directions: the study of augmented high-lift system for a cross-section airfoil of a wing up to transonic regime and the circulation control implemented by tangentially blowing jet over a highly curved surface due to Coanda effect on a rotor blade for a wind turbine. This study were analyzed the performance, sensitivities and limitations of the circulation control method based on blowing jet for a fixed wing as well as for a rotating wing. Directions of future research are identified and discussed.

  5. POD Analysis of Flow Behind a Four-wing Vortex Generator

    Science.gov (United States)

    Hosseinali, Mahdi; Wilkins, Stephen; Hall, Joseph

    2015-11-01

    Wing-tip vortices that persist long after the passage of large aircraft are of major concern to aircraft controllers and are responsible for considerable delays between aircraft take-off times. Understanding these vortices is extremely important, with the ultimate goal to reduce or eliminate delays altogether. Simple theoretical models of vortices can be studied experimentally using a four-wing vortex generator. The cross-stream planes are measured with a two-component Particle Image Velocimetry (PIV) system, and the resulting vector fields were analyzed with a Proper Orthogonal Decomposition (POD) via the method of snapshots. POD analysis will be employed both before and after removing vortex core meandering to investigate the meandering effect on POD modes for a better understanding of it.

  6. Vortical flows over delta wings and numerical prediction of vortex breakdown

    Science.gov (United States)

    Ekaterinaris, J. A.; Schiff, Lewis B.

    1990-01-01

    Navier-Stokes solutions of subsonic vortical flow over a 75 deg sweep delta wing with a sharp leading edge are presented. The sensitivity of the solution to the numerical scheme is examined using both a partially upwind scheme and a scheme with central differencing in all directions. At moderate angles of attack, no vortex breakdown is observed, whereas the higher angle-of-attack cases exhibit breakdown. The effect of numerical grid density is investigated, and solutions that are obtained with various grid densities are compared with experimental data. An embedded grid approach is implemented to enable higher resolution in selected isolated flow regions, such as the leeward-side surface, the leading-edge vortical flow, and the vortex breakdown region.

  7. Topological structures of vortex flow on a flying wing aircraft, controlled by a nanosecond pulse discharge plasma actuator

    Science.gov (United States)

    Du, Hai; Shi, Zhiwei; Cheng, Keming; Wei, Dechen; Li, Zheng; Zhou, Danjie; He, Haibo; Yao, Junkai; He, Chengjun

    2016-06-01

    Vortex control is a thriving research area, particularly in relation to flying wing or delta wing aircraft. This paper presents the topological structures of vortex flow on a flying wing aircraft controlled by a nanosecond plasma dielectric barrier discharge actuator. Experiments, including oil flow visualization and two-dimensional particle image velocimetry (PIV), were conducted in a wind tunnel with a Reynolds number of 0.5 × 106. Both oil and PIV results show that the vortex can be controlled. Oil topological structures on the aircraft surface coincide with spatial PIV flow structures. Both indicate vortex convergence and enhancement when the plasma discharge is switched on, leading to a reduced region of separated flow.

  8. Leading-edge flow reattachment and the lateral static stability of low-aspect-ratio rectangular wings

    Science.gov (United States)

    Linehan, Thomas; Mohseni, Kamran

    2017-11-01

    The relationship between lateral static stability derivative, Clβ,lift coefficient, CL, and angle of attack was investigated for rectangular wings of aspect ratio A R =0.75 ,1 ,1.5 , and 3 using Stereo-Digital Particle Image Velocimetry (S-DPIV) and direct force and moment measurements. When the product Cl βA R is plotted with respect to CL, the lateral stability curves of each wing collapse to a single line for CL0.7 , the linearity and scaling of Clβwith respect to CL is lost. S-DPIV is used to elucidate the flow physics in this nonlinear regime. At α =10∘ , the leading-edge separation region emerges on the leeward portion of the sideslipped wing by means of vortex shedding. For the A R ≤1.5 wings at α >15∘ , the tip vortex downwash is sufficient to restrict the shedding of leading-edge vorticity thereby sustaining the lift of the leading-edge separation region at high angles of attack. Concurrently, the windward tip vortex grows in size and strength with increasing angle of attack, displacing the leading-edge separation region further toward the leeward wing. This reorganization of lift-generating vorticity results in the initial nonlinearities between Cl β and CL at angles of attack for which CL is still increasing. At angles of attack near that of maximum lift for the A R ≤1 wings, the windward tip vortex lifts off the wing, decreasing the lateral static stability of the wing prior to lift stall. For the A R =3 wing at α >10∘ , nonlinear trends in Cl β versus CL occur due to the spanwise evolution of stalled flow.

  9. 3D flow visualization and tomographic particle image velocimetry for vortex breakdown over a non-slender delta wing

    Science.gov (United States)

    Wang, ChengYue; Gao, Qi; Wei, RunJie; Li, Tian; Wang, JinJun

    2016-06-01

    Volumetric measurement for the leading-edge vortex (LEV) breakdown of a delta wing has been conducted by three-dimensional (3D) flow visualization and tomographic particle image velocimetry (TPIV). The 3D flow visualization is employed to show the vortex structures, which was recorded by four cameras with high resolution. 3D dye streaklines of the visualization are reconstructed using a similar way of particle reconstruction in TPIV. Tomographic PIV is carried out at the same time using same cameras with the dye visualization. Q criterion is employed to identify the LEV. Results of tomographic PIV agree well with the reconstructed 3D dye streaklines, which proves the validity of the measurements. The time-averaged flow field based on TPIV is shown and described by sections of velocity and streamwise vorticity. Combining the two measurement methods sheds light on the complex structures of both bubble type and spiral type of breakdown. The breakdown position is recognized by investigating both the streaklines and TPIV velocity fields. Proper orthogonal decomposition is applied to extract a pair of conjugated helical instability modes from TPIV data. Therefore, the dominant frequency of the instability modes is obtained from the corresponding POD coefficients of the modes based on wavelet transform analysis.

  10. Vortex Lattice Simulations of Attached and Separated Flows around Flapping Wings

    Directory of Open Access Journals (Sweden)

    Thomas Lambert

    2017-04-01

    Full Text Available Flapping flight is an increasingly popular area of research, with applications to micro-unmanned air vehicles and animal flight biomechanics. Fast, but accurate methods for predicting the aerodynamic loads acting on flapping wings are of interest for designing such aircraft and optimizing thrust production. In this work, the unsteady vortex lattice method is used in conjunction with three load estimation techniques in order to predict the aerodynamic lift and drag time histories produced by flapping rectangular wings. The load estimation approaches are the Katz, Joukowski and simplified Leishman–Beddoes techniques. The simulations’ predictions are compared to experimental measurements from wind tunnel tests of a flapping and pitching wing. Three types of kinematics are investigated, pitch-leading, pure flapping and pitch lagging. It is found that pitch-leading tests can be simulated quite accurately using either the Katz or Joukowski approaches as no measurable flow separation occurs. For the pure flapping tests, the Katz and Joukowski techniques are accurate as long as the static pitch angle is greater than zero. For zero or negative static pitch angles, these methods underestimate the amplitude of the drag. The Leishman–Beddoes approach yields better drag amplitudes, but can introduce a constant negative drag offset. Finally, for the pitch-lagging tests the Leishman–Beddoes technique is again more representative of the experimental results, as long as flow separation is not too extensive. Considering the complexity of the phenomena involved, in the vast majority of cases, the lift time history is predicted with reasonable accuracy. The drag (or thrust time history is more challenging.

  11. Twin Tail/Delta Wing Configuration Buffet Due to Unsteady Vortex Breakdown Flow

    Science.gov (United States)

    Kandil, Osama A.; Sheta, Essam F.; Massey, Steven J.

    1996-01-01

    The buffet response of the twin-tail configuration of the F/A-18 aircraft; a multidisciplinary problem, is investigated using three sets of equations on a multi-block grid structure. The first set is the unsteady, compressible, full Navier-Stokes equations. The second set is the coupled aeroelastic equations for bending and torsional twin-tail responses. The third set is the grid-displacement equations which are used to update the grid coordinates due to the tail deflections. The computational model consists of a 76 deg-swept back, sharp edged delta wing of aspect ratio of one and a swept-back F/A-18 twin-tails. The configuration is pitched at 32 deg angle of attack and the freestream Mach number and Reynolds number are 0.2 and 0.75 x 10(exp 6) respectively. The problem is solved for the initial flow conditions with the twin tail kept rigid. Next, the aeroelastic equations of the tails are turned on along with the grid-displacement equations to solve for the uncoupled bending and torsional tails response due to the unsteady loads produced by the vortex breakdown flow of the vortex cores of the delta wing. Two lateral locations of the twin tail are investigated. These locations are called the midspan and inboard locations.

  12. Development of Advanced High Lift Leading Edge Technology for Laminar Flow Wings

    Science.gov (United States)

    Bright, Michelle M.; Korntheuer, Andrea; Komadina, Steve; Lin, John C.

    2013-01-01

    This paper describes the Advanced High Lift Leading Edge (AHLLE) task performed by Northrop Grumman Systems Corporation, Aerospace Systems (NGAS) for the NASA Subsonic Fixed Wing project in an effort to develop enabling high-lift technology for laminar flow wings. Based on a known laminar cruise airfoil that incorporated an NGAS-developed integrated slot design, this effort involved using Computational Fluid Dynamics (CFD) analysis and quality function deployment (QFD) analysis on several leading edge concepts, and subsequently down-selected to two blown leading-edge concepts for testing. A 7-foot-span AHLLE airfoil model was designed and fabricated at NGAS and then tested at the NGAS 7 x 10 Low Speed Wind Tunnel in Hawthorne, CA. The model configurations tested included: baseline, deflected trailing edge, blown deflected trailing edge, blown leading edge, morphed leading edge, and blown/morphed leading edge. A successful demonstration of high lift leading edge technology was achieved, and the target goals for improved lift were exceeded by 30% with a maximum section lift coefficient (Cl) of 5.2. Maximum incremental section lift coefficients ( Cl) of 3.5 and 3.1 were achieved for a blown drooped (morphed) leading edge concept and a non-drooped leading edge blowing concept, respectively. The most effective AHLLE design yielded an estimated 94% lift improvement over the conventional high lift Krueger flap configurations while providing laminar flow capability on the cruise configuration.

  13. Low Reynolds Number Wing Transients in Rotation and Translation

    Science.gov (United States)

    Jones, Anya; Schlueter, Kristy

    2012-11-01

    The unsteady aerodynamic forces and flow fields generated by a wing undergoing transient motions in both rotation and translation were investigated. An aspect ratio 2 flat plate wing at a 45 deg angle of attack was driven over 84 deg of rotation (3 chord-lengths of travel at 3/4 span) and 3 and 10 chord-lengths of translation in quiescent water at Reynolds numbers between 2,500 and 15,000. Flow visualization on the rotating wing revealed a leading edge vortex that lifted off of the wing surface, but remained in the vicinity of the wing for the duration of the wing stroke. A second spanwise vortex with strong axial flow was also observed. As the tip vortex grew, the leading edge vortex joined the tip vortex in a loop-like structure over the aft half of the wing. Near the leading edge, spanwise flow in the second vortex became entrained in the tip vortex near the corner of the wing. Unsteady force measurements revealed that lift coefficient increased through the constant-velocity portion of the wing stroke. Forces were compared for variations in wing acceleration and Reynolds number for both rotational and translational motions. The effect of tank blockage was investigated by repeating the experiments on multiple wings, varying the distance between the wing tip and tank wall. U.S. Air Force Research Laboratory, Summer Faculty Fellowship Program.

  14. Experimental study of the vortex flow behavior on a generic fighter wing at subsonic and transonic speeds

    Science.gov (United States)

    Erickson, Gary E.; Rogers, Lawrence W.

    1987-01-01

    A subsonic and transonic investigation of the vortex flow behavior of a generic fighter configuration with 55-deg cropped delta wing has been conducted in order to improve current understanding of vortical motions on a wing with deflected leading edge flap at moderate and high angles-of-attack. The leading edge vortex strength was reduced, and the vortex was flatter and closer to the wing surface, as the Mach number increased. Transonically, at high angles-of-attack, the test data suggested the development of a cross-flow shock wave above the vortex sheet which coexisted with a rear shock wave. Subsonically, a deflected leading edge flap was able to sustain a concentrated vortex on the forward-facing surface.

  15. The stability of two-phase flow over a swept-wing

    Science.gov (United States)

    Coward, Adrian; Hall, Philip

    1994-01-01

    We use numerical and asymptotic techniques to study the stability of a two-phase air/water flow above a flat porous plate. This flow is a model of the boundary layer which forms on a yawed cylinder and can be used as a useful approximation to the air flow over swept wings during heavy rainfall. We show that the interface between the water and air layers can significantly destabilize the flow, leading to traveling wave disturbances which move along the attachment line. This instability occurs for lower Reynolds numbers than in the case of the absence of a water layer. We also investigate the instability of inviscid stationary modes. We calculate the effective wavenumber and orientation of the stationary disturbance when the fluids have identical physical properties. Using perturbation methods we obtain corrections due to a small stratification in viscosity, thus quantifying the interfacial effects. Our analytical results are in agreement with the numerical solution which we obtain for arbitrary fluid properties.

  16. Investigation of the interference effects of mixed flow long duct nacelles on a DC-10 wing

    Science.gov (United States)

    Patel, S. P.; Donelson, J. E.

    1982-01-01

    Wind tunnel test results utilizing a 4.7 percent scale semispan model in the 11 foot transonic wind tunnel are presented. A low drag long duct nacelle installation for the DC-10 jet transport was developed. A long duct nacelle representative of a CF6-50 mixed flow configuration was investigated on the DC-10-30. The results showed that the long duct nacelle installation located in the same position as the current short duct nacelle and with the current production symmetrical pylon is a relatively low risk installation for the DC-10 aircraft. Tuft observations and analytical boundary layer analysis confirmed that the flow on the nacelle afterbody was attached. A small pylon fairing was evaluated and found to reduce channel peak suction pressures, which resulted in a small drag improvement. The test also confirmed that the optimum nacelle incidence angle is the same as for the short duct nacelle, thus the same engine mount as for the production short duct nacelle can be used for the long duct nacelle installation. Comparison of the inboard wing pylon nacelle channel pressure distributions, with flow through and powered long duct nacelles showed that the power effects did not change the flow mechanism; hence, power effects can be considered negligible.

  17. Aerodynamic Characterization of ‘DelFly Micro’ in Forward Flight Configuration by Force Measurements and Flow Field Visualization

    OpenAIRE

    Deng, Shuanghou; Percin, Mustafa; van Oudheusden, Bas

    2015-01-01

    This study explores the flow structures and unsteady force generation mechanisms of a flapping-wing micro air vehicle ‘DelFly Micro’ in forward flight configuration. Stereoscopic Particle Image Velocimetry (Stereo-PIV) measurements were performed to acquire three dimensional flow fields in the wake. Six components of forces and moments were captured simultaneously by use of a miniature force sensor.

  18. Aerodynamic Characterization of ‘DelFly Micro’ in Forward Flight Configuration by Force Measurements and Flow Field Visualization

    NARCIS (Netherlands)

    Deng, S.; Percin, M.; Van Oudheusden, B.

    2015-01-01

    This study explores the flow structures and unsteady force generation mechanisms of a flapping-wing micro air vehicle ‘DelFly Micro’ in forward flight configuration. Stereoscopic Particle Image Velocimetry (Stereo-PIV) measurements were performed to acquire three dimensional flow fields in the wake.

  19. Vector Fields and Flows on Differentiable Stacks

    DEFF Research Database (Denmark)

    A. Hepworth, Richard

    2009-01-01

    This paper introduces the notions of vector field and flow on a general differentiable stack. Our main theorem states that the flow of a vector field on a compact proper differentiable stack exists and is unique up to a uniquely determined 2-cell. This extends the usual result on the existence...... of vector fields....

  20. A PIV Study of Baseline and Controlled Flow over the Highly Deflected Flap of a Generic Low Aspect Ratio Trapezoidal Wing

    Science.gov (United States)

    Tewes, Philipp; Genschow, Konstantin; Little, Jesse; Wygnanski, Israel

    2017-11-01

    A detailed flow survey using PIV was conducted over a highly-deflected flap (55°) of a low-aspect ratio trapezoidal wing. The wing section is a NACA 0012 with 45° sweep at both the leading and trailing edges, an aspect ratio of 1.5 and a taper ratio of 0.27. The main element is equipped with 7 equally spaced fluidic oscillators, covering the inner 60 % of the span, located near the flap hinge. Experiments were carried out at 0° and 8° incidence at a Reynolds number of 1.7 .106 for both baseline and active flow control (AFC) cases. Velocity ISO-surfaces, x-vorticity and streamlines are analyzed / discussed. A flap leading edge vortex governs the baseline flow field for 0°. This vortical structure interacts with the jets emitted by the actuators (Cμ = 1 %). Its development is hampered and the vortex is redirected toward the trailing edge resulting in a CL increase. At 8°, the dominant flap leading edge vortex could not be detected and is believed to have already merged with the tip vortex. AFC attached the flow over the flap and enhanced the lift by up to 20 % while maintaining longitudinal stability. The dominant flow features in the AFC cases are actuator-generated streamwise vortices which appear stronger at 8°. This work was supported by the Office of Naval Research under ONR Grant No. N00014-14-1-0387.

  1. Force production and time-averaged flow structure around thin, non-slender delta wings

    Science.gov (United States)

    Tu, Han; Green, Melissa

    2017-11-01

    Experimental force measurement and time-averaged three dimensional flow visualization of low Reynolds number baseline cases have been carried out on a steady flat plate delta wing. Current data will serve as steady reference for future unsteady flow and actuation cases. The comprehensive study will compare force production in highly unsteady environments, which is necessary to consider in unmanned combat aerial vehicle (UCAV) control strategies. Force measurements are carried out at angles of attack 10, 15, 20, 25 and 30 degrees. The coefficient of drag increases with angle of attack, while the coefficient of lift reaches a maximum value at 20 degrees. Time-averaged flow visualization conducted at angles of attack of 20, 25 and 30 degrees shows vortices with larger magnitude that persist farther into wake are generated at higher angles of attack. These results compare analogously with similar steady baseline experiment results of high Reynolds number conducted by collaborators. This work was supported by the Office of Naval Research under ONR Award No. N00014-16-1-2732. We also acknowledge the collaborative support of Dr. David Rival and Mr. Matthew Marzanek at Queen's University.

  2. Europa's Alfvén wing: shrinkage and displacement influenced by an induced magnetic field

    Directory of Open Access Journals (Sweden)

    M. Volwerk

    2007-05-01

    Full Text Available The Galileo magnetometer data are used to investigate the structure of the Alfvén wing during three flybys of Europa. The presence of an induced magnetic field is shown to shrink the cross section of the Alfvén wing and offset it along the direction radial to Jupiter. Both the shrinkage and the offset depend on the strength of the induced field. The entry and exit points of the spacecraft into and out of the Alfvén wings are modeled to determine the angle between the wings and the background magnetic field. Tracing of the Alfvén characteristics in a model magnetic field consisting of Jupiter's background field and an induced field in Europa produces an offset and shrinking of the Alfvén wing consistent with the geometric modeling. Thus we believe that the Alfvén wing properties have been determined correctly. The Alfvén wing angle is directly proportional to the local Alfvén velocity, and is thus a probe for the local plasma density. We show that the inferred plasma density can be understood in terms of the electron density measured by the plasma wave experiment. When Europa is located in the Jovian plasma sheet the derived mass-per-charge exceeds the previous estimates, which is a result of increased pickup of sputtered ions near the moon. The estimated rate of O2+ pickup agrees well with the results from numerical models.

  3. Flow structure and aerodynamic performance of a hovering bristled wing in low Re

    Science.gov (United States)

    Lee, Seunghun; Lahooti, Mohsen; Kim, Daegyoum

    2017-11-01

    Previous studies on a bristled wing have mainly focused on simple kinematics of the wing such as translation or rotation. The aerodynamic performance of a bristled wing in a quasi-steady phase is known to be comparable to that of a smooth wing without a gap because shear layers in the gaps of the bristled wing are sufficiently developed to block the gaps. However, we point out that, in the starting transient phase where the shear layers are not fully developed, the force generation of a bristled wing is not as efficient as that of a quasi-steady state. The performance in the transient phase is important to understand the aerodynamics of a bristled wing in an unsteady motion. In the hovering motion, due to repeated stroke reversals, the formation and development of shear layers inside the gaps is repeated in each stroke. In this study, a bristled wing in hovering is numerically investigated in the low Reynolds number of O(10). We especially focus on the development of shear layers during a stroke reversal and its effect on the overall propulsive performance. Although the aerodynamic force generation is slightly reduced due to the gap vortices, the asymmetric behavior of vortices in a gap between bristles during a stroke reversal makes the bristled wing show higher lift to drag ratio than a smooth wing.

  4. Flow characteristics of air in square duct using delta wing vortex generators

    Directory of Open Access Journals (Sweden)

    Mahesh R. Ingalagi

    2016-09-01

    Full Text Available Performance improvement in terms of improving heat transfer coefficient and reducing pressure drop becomes essential in heat exchange applications and a large number of methods for reducing pressure drop exist in the literature and the present work is an investigation on use of delta wings as vortex generators for reducing pressure drop. Methodology includes air from a blower entering the test section through orificemeter and differential-micro manometer to measure the flow rate and pressure drop across the test section. Depending upon the pressure drops, friction factors for smooth and rough surface of the duct are estimated. The effect of geometrical parameters of delta wing and duct aspect ratio on friction factor ratios are reported Based on Reynolds number in the range of 8000−24000. The geometrical parameters of vortex generators varied in this study were the pitch-to-vortex generator height ratio (p/e, vortex generator height to duct hydraulic diameter ratio (e/Dh, aspect ratio of vortex generator (ar. Results are reported for 0.1 < e/Dh < 0.5, p/e = 4,8,12,16, (ar = 1.6,2.3,4, N = 1 in ducts having aspect ratio AR = 1, Detailed friction factor analysis for Re 8000−24000 has been presented for different configurations of vortex generators used in the square duct. The experimental results of the present study for friction factor in smooth square duct matches well with values taken from formula proposed by Blasius. The friction factor ratio increases with increase in e/Dh value, which may be attributed to increased blockage of the flow passage. For a given p/e, increasing e/Dh ratio for the same (ar has the effect of increasing circulation strength and core size of the vortex thereby offering more resistance to flow that results into a higher friction factor ratio. The results have been presented in the form of the friction factor ratio of the roughened and smooth ducts operating at equal Reynolds numbers. Semi

  5. Effects of Coupled Rolling and Pitching Oscillations on Transonic Shock-Induced Vortex-Breakdown Flow of a Delta Wing

    Science.gov (United States)

    Kandil, Osama A.; Menzies, Margaret A.

    1996-01-01

    Unsteady, transonic vortex-breakdown flow over a 65 deg. sharp edged, cropped-delta wing of zero thickness undergoing forced coupled pitching and rolling oscillations is investigated computationally. The initial condition of the flow is characterized by a transverse terminating shock which induces of the leading edge vortex cores to breakdown. The computational investigation uses the time-accurate solution of the laminar, unsteady, compressible, full Navier-Stokes equations with the implicit, upwind, Roe flux-difference splitting, finite-volume scheme. The main focus is to analyze the effects of coupled motion on the wing response and vortex-breakdown flow by varying oscillation frequency and phase angle while keeping the maximum pitch and roll amplitude equal.

  6. Flow Control and High-Lift Performance for Flying-Wing Unmanned Combat Air Vehicle Configurations by inserting slots

    Directory of Open Access Journals (Sweden)

    U Ali

    2016-06-01

    Full Text Available The objectives of the present study on Unmanned Combat Air Vehicles (UCAVs are two-fold: first to control the flow by inserting leading-edge and cross-flow slots and analysing the viscous flow development over the outer panels of a flying-wing configuration to maximise the performance of the elevons control surfaces; second to predict high-lift performance particularly the maximum-lift characteristics. This is demonstrated using a variety of inviscid Vortex Lattice Method (VLM and Euler, and viscous CFD Reynolds Averaged Navier-Stokes (RANS methods. The computational results are validated against experiment measured in a wind tunnel. Two flying-wing planforms are considered based around a generic 40˚ edge-aligned configuration. The VLM predicts a linear variation of lift and pitching moment with incidence angle, and substantially under-predicts the induced drag. Results obtained from RANS and Euler agree well with experiment.

  7. Flow visualization of a low density hypersonic flow field

    International Nuclear Information System (INIS)

    Masson, B.S.; Jumper, E.J.; Walters, E.; Segalman, T.Y.; Founds, N.D.

    1989-01-01

    Characteristics of laser induced iodine fluorescence (LIIF) in low density hypersonic flows are being investigated for use as a diagnostic technique. At low pressures, doppler broadening dominates the iodine absorption profile producing a fluorescence signal that is primarily temperature and velocity dependent. From this dependency, a low pressure flow field has the potential to be mapped for its velocity and temperature fields. The theory for relating iodine emission to the velocity and temperature fields of a hypersonic flow is discussed in this paper. Experimental observations are made of a fluorescencing free expansion and qualitatively related to the theory. 7 refs

  8. The Aerodynamic Behavior of a Harmonically Oscillating Finite Sweptback Wing in Supersonic Flow

    National Research Council Canada - National Science Library

    Chang, Chieh-Chien

    1951-01-01

    By an extension of Evvard's "diaphragm" concept outside the wing tip, the present paper presents two approximate methods for calculating the aerodynamic behavior of harmonically oscillating, sweptback...

  9. Intergration effects of D-shaped, underwing, aft-mounted, separate-flow, flow-through nacelles on a high-wing transport

    Science.gov (United States)

    Lamb, Milton; Carlson, John R.; Pendergraft, Odis C., Jr.

    1987-01-01

    An experimental investigation was conducted in the Langley 16-Foot Transonic Tunnel at freestream Mach numbers from 0.70 to 0.82 and angles of attack from -3.0 to 4.0 deg to determine the integration effects of D-shaped, underwing, aft-mounted, separate-flow, flow-through nacelles on a high-wing transonic transport configuration. The results showed that the aft-mounted nacelle/pylon produced an increase in lift over that of the wing-body configuration by pressurizing much of the wing lower surface in front of the pylon. For the D-shaped nacelle, a substantial region of supersonic flow over the wing, aft of the lip of the nacelle, cancelled the reduction in drag caused by the increase in pressures ahead of the lip, to increase interference and form drag compared with a similar circular-shaped nacelle. The installed drag of the D=shaped nacelle was essentially the same as that of an aft-mounted circular nacelle from a previous investigation.

  10. SALLY LEVEL II- COMPUTE AND INTEGRATE DISTURBANCE AMPLIFICATION RATES ON SWEPT AND TAPERED LAMINAR FLOW CONTROL WINGS WITH SUCTION

    Science.gov (United States)

    Srokowski, A. J.

    1994-01-01

    The computer program SALLY was developed to compute the incompressible linear stability characteristics and integrate the amplification rates of boundary layer disturbances on swept and tapered wings. For some wing designs, boundary layer disturbance can significantly alter the wing performance characteristics. This is particularly true for swept and tapered laminar flow control wings which incorporate suction to prevent boundary layer separation. SALLY should prove to be a useful tool in the analysis of these wing performance characteristics. The first step in calculating the disturbance amplification rates is to numerically solve the compressible laminar boundary-layer equation with suction for the swept and tapered wing. A two-point finite-difference method is used to solve the governing continuity, momentum, and energy equations. A similarity transformation is used to remove the wall normal velocity as a boundary condition and place it into the governing equations as a parameter. Thus the awkward nonlinear boundary condition is avoided. The resulting compressible boundary layer data is used by SALLY to compute the incompressible linear stability characteristics. The local disturbance growth is obtained from temporal stability theory and converted into a local growth rate for integration. The direction of the local group velocity is taken as the direction of integration. The amplification rate, or logarithmic disturbance amplitude ratio, is obtained by integration of the local disturbance growth over distance. The amplification rate serves as a measure of the growth of linear disturbances within the boundary layer and can serve as a guide in transition prediction. This program is written in FORTRAN IV and ASSEMBLER for batch execution and has been implemented on a CDC CYBER 70 series computer with a central memory requirement of approximately 67K (octal) of 60 bit words. SALLY was developed in 1979.

  11. A Structural Design Concept for a Multi-Shell Blended Wing Body with Laminar Flow Control

    Directory of Open Access Journals (Sweden)

    Majeed Bishara

    2018-02-01

    Full Text Available Static and fatigue analyses are presented for a new blended wing body (BWB fuselage concept considering laminar flow control (LFC by boundary layer suction in order to reduce the aerodynamic drag. BWB aircraft design concepts profit from a structurally beneficial distribution of lift and weight and allow a better utilization of interior space over conventional layouts. A structurally efficient design concept for the pressurized BWB cabin is a vaulted layout that is, however, aerodynamically disadvantageous. A suitable remedy is a multi-shell design concept with a separate outer skin. The synergetic combination of such a multi-shell BWB fuselage with a LFC via perforation of the outer skin to attain a drag reduction appears promising. In this work, two relevant structural design aspects are considered. First, a numerical model for a ribbed double-shell design of a fuselage segment is analyzed. Second, fatigue aspects of the perforation in the outer skin are investigated. A design making use of controlled fiber orientation is proposed for the perforated skin. The fatigue behavior is compared to perforation methods with conventional fiber topologies and to configurations without perforations.

  12. The influence of wing morphology on the three-dimensional flow patterns of a flapping wing at bird scale

    NARCIS (Netherlands)

    Thielicke, William; Stamhuis, Eize J.

    The effect of airfoil design parameters, such as airfoil thickness and camber, are well understood in steady-state aerodynamics. But this knowledge cannot be readily applied to the flapping flight in insects and birds: flow visualizations and computational analyses of flapping flight have identified

  13. Coupled Rolling and Pitching Oscillation Effects on Transonic Shock-Induced Vortex-Breakdown Flow of a Delta Wing

    Science.gov (United States)

    Kandil, Osama A.; Menzies, Margaret A.

    1996-01-01

    Unsteady, transonic vortex dominated flow over a 65 deg. sharp edged, cropped-delta wing of zero thickness undergoing forced coupled pitching and rolling oscillations is investigated computationally. The wing mean angle of attack is 20 deg. and the free stream Mach number and Reynolds number are 0.85 and 3.23 x 10(exp 6), respectively. The initial condition of the flow is characterized by a transverse terminating shock and vortex breakdown of the leading edge vortex cores. The computational investigation uses the time-accurate solution of the laminar, unsteady, compressible, full Navier-Stokes equations with the implicit, upwind, Roe flux-difference splitting, finite volume scheme. The main focus is to analyze the effects of coupled motion on the wing response and vortex breakdown flow by varying oscillation frequency and phase angle while the maximum pitch and roll amplitude is kept constant at 4.0 deg. Four cases demonstrate the following: simultaneous motion at a frequency of 1(pi), motion with a 90 deg. phase lead in pitch, motion with a rolling frequency of twice the pitching frequency, and simultaneous motion at a frequency of 2(pi). Comparisons with single mode motion at these frequencies complete this study and illustrate the effects of coupling the oscillations.

  14. Heat transfer and oil flow studies on a single-stage-to-orbit control-configured winged entry vehicle

    Science.gov (United States)

    Helms, V. T., III; Bradley, P. F.

    1984-01-01

    Results are presented for oil flow and phase change paint heat transfer tests conducted on a 0.006 scale model of a proposed single stage to orbit control configured vehicle. The data were taken at angles of attack up to 40 deg at a free stream Mach number of 10 for Reynolds numbers based on model length of 0.5 x 10 to the 6th power, 1.0 x 10 to the 6th power and 2.0 x 10 to the 6th power. The magnitude and distribution of heating are characterized in terms of angle of attack and Reynolds number aided by an analysis of the flow data which are used to suggest the presence of various three dimensional flow structures that produce the observed heating patterns. Of particular interest are streak heating patterns that result in high localized heat transfer rates on the wing windward surface at low to moderate angles of attack. These streaks are caused by the bow-shock/wing-shock interaction and formation of the wing-shock. Embedded vorticity was found to be associated with these interactions.

  15. Flow NMR of polymers in external fields

    Energy Technology Data Exchange (ETDEWEB)

    Boehme, Ute; Bagusat, Frank; Scheler, Ulrich [Leibniz Institute of Polymer Research Dresden (Germany)

    2008-07-01

    Pulsed-field gradient NMR is applied to study the motion of polymers in an external electric field and under mechanical shear. The application of an electric field drives motion of charged species. In conjunction with the diffusion coefficient from the electrophoretic mobility the effective charge per molecule is derived. The electric field applicable in the aqueous system is too weak to deform the polymer or even abstract counterions. In a shear flow established in a Couette cell partial orientation of polymer chains is measured via residual dipolar couplings. The entire flow field in a non-symmetric flow cell is monitored by a combination of PFG NMR and NMR imaging exhibiting regions of high shear and locally low shear, where polymers relax.

  16. A summary of lateral-stability derivatives calculated for wing plan forms in supersonic flow

    Science.gov (United States)

    Jones, Arthur L; Alksne, Alberta

    1951-01-01

    A compilation of theoretical values of the lateral-stability derivatives for wings at supersonic speeds is presented in the form of design charts. The wing plan forms for which this compilation has been prepared include a rectangular, two trapezoidal, two triangular, a fully-tapered swept-back, a sweptback hexagonal, an unswept hexagonal, and a notched triangular plan form. A full set of results, that is, values for all nine of the lateral-stability derivatives for wings, was available for the first six of these plan forms only. The reasons for the incompleteness of the results available for other plan forms are discussed.

  17. Visualization of numerically simulated aerodynamic flow fields

    International Nuclear Information System (INIS)

    Hian, Q.L.; Damodaran, M.

    1991-01-01

    The focus of this paper is to describe the development and the application of an interactive integrated software to visualize numerically simulated aerodynamic flow fields so as to enable the practitioner of computational fluid dynamics to diagnose the numerical simulation and to elucidate essential flow physics from the simulation. The input to the software is the numerical database crunched by a supercomputer and typically consists of flow variables and computational grid geometry. This flow visualization system (FVS), written in C language is targetted at the Personal IRIS Workstations. In order to demonstrate the various visualization modules, the paper also describes the application of this software to visualize two- and three-dimensional flow fields past aerodynamic configurations which have been numerically simulated on the NEC-SXIA Supercomputer. 6 refs

  18. Front propagation in a chaotic flow field

    Science.gov (United States)

    Mehrvarzi, C. O.; Paul, M. R.

    2014-07-01

    We investigate numerically the dynamics of a propagating front in the presence of a spatiotemporally chaotic flow field. The flow field is the three-dimensional time-dependent state of spiral defect chaos generated by Rayleigh-Bénard convection in a spatially extended domain. Using large-scale parallel numerical simulations, we simultaneously solve the Boussinesq equations and a reaction-advection-diffusion equation with a Fischer-Kolmogorov-Petrovskii-Piskunov reaction for the transport of the scalar species in a large-aspect-ratio cylindrical domain for experimentally accessible conditions. We explore the front dynamics and geometry in the low-Damköhler-number regime, where the effect of the flow field is significant. Our results show that the chaotic flow field enhances the front propagation when compared with a purely cellular flow field. We quantify this enhancement by computing the spreading rate of the reaction products for a range of parameters. We use our results to quantify the complexity of the three-dimensional front geometry for a range of chaotic flow conditions.

  19. Improved modeling techniques for turbomachinery flow fields

    Energy Technology Data Exchange (ETDEWEB)

    Lakshminarayana, B.; Fagan, J.R. Jr.

    1995-12-31

    This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbomachinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. This will be accomplished in a cooperative program by Penn State University and the Allison Engine Company. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tenor.

  20. Unsteady characteristics of a slat-cove flow field

    Science.gov (United States)

    Pascioni, Kyle A.; Cattafesta, Louis N.

    2018-03-01

    The leading-edge slat of a multielement wing is a significant contributor to the acoustic signature of an aircraft during the approach phase of the flight path. An experimental study of the two-dimensional 30P30N geometry is undertaken to further understand the flow physics and specific noise source mechanisms. The mean statistics from particle image velocimetry (PIV) shows the differences in the flow field with angle of attack, including the interaction between the cove and trailing-edge flow. Phase-locked PIV successfully links narrow-band peaks found in the surface pressure spectrum to shear layer instabilities and also reveals that a bulk cove oscillation at a Strouhal number based on a slat chord of 0.15 exists, indicative of shear layer flapping. Unsteady surface pressure measurements are documented and used to estimate spanwise coherence length scales. A narrow-band frequency prediction scheme is also tested and found to agree well with the data. Furthermore, higher-order spectral analysis suggests that nonlinear effects cause additional peaks to arise in the power spectrum, particularly at low angles of attack.

  1. Hovering hummingbird wing aerodynamics during the annual cycle. II. Implications of wing feather moult

    Science.gov (United States)

    Sapir, Nir; Elimelech, Yossef

    2018-01-01

    Birds usually moult their feathers in a particular sequence which may incur aerodynamic, physiological and behavioural implications. Among birds, hummingbirds are unique species in their sustained hovering flight. Because hummingbirds frequently hover-feed, they must maintain sufficiently high flight capacities even when moulting their flight feathers. A hummingbird wing consists of 10 primary flight feathers whose absence during moult may strongly affect wing performance. Using dynamic similarity rules, we compared time-accurate aerodynamic loads and flow field measurements over several wing geometries that follow the natural feather moult sequence of Calypte anna, a common hummingbird species in western North America. Our results suggest a drop of more than 20% in lift production during the early stages of the moult sequence in which mid-wing flight feathers are moulted. We also found that the wing's ability to generate lift strongly depended on the morphological integrity of the outer primaries and leading-edge. These findings may explain the evolution of wing morphology and moult attributes. Specifically, the high overlap between adjacent wing feathers, especially at the wing tip, and the slow sequential replacement of the wing feathers result in a relatively small reduction in wing surface area during moult with limited aerodynamic implications. We present power and efficiency analyses for hover flight during moult under several plausible scenarios, suggesting that body mass reduction could be a compensatory mechanism that preserves the energetic costs of hover flight. PMID:29515884

  2. Flow-synchronous field motion refrigeration

    Science.gov (United States)

    Hassen, Charles N.

    2017-08-22

    An improved method to manage the flow of heat in an active regenerator in a magnetocaloric or an electrocaloric heat-pump refrigeration system, in which heat exchange fluid moves synchronously with the motion of a magnetic or electric field. Only a portion of the length of the active regenerator bed is introduced to or removed from the field at one time, and the heat exchange fluid flows from the cold side toward the hot side while the magnetic or electric field moves along the active regenerator bed.

  3. The Realization and Study of Optical Wings

    Science.gov (United States)

    Artusio-Glimpse, Alexandra Brae

    Consider the airfoil: a carefully designed structure capable of stable lift in a uniform air flow. It so happens that air pressure and radiation (light) pressure are similar phenomena because each transfer momentum to flow-disturbing objects. This, then, begs the question: does an optical analogue to the airfoil exist? Though an exceedingly small effect, scientists harness radiation pressure in a wide gamut of applications from micromanipulation of single biological particles to the propulsion of large spacecrafts called solar sails. We introduce a cambered, refractive rod that is subjected to optical forces analogous to those seen in aerodynamics, and I call this analogue the optical wing. Flight characteristics of optical wings are determined by wing shape and material in a uniform radiation field. Theory predicts the lift force and axial torque are functions of the wing's angle of attack with stable and unstable orientations. These structures can operate as intensity-dependent, parametrically driven oscillators. In two-dimensions, the wings exhibit bistability when analyzed in an accelerating frame. In three-dimensions, the motion of axially symmetric spinning hemispherical wings is analogous to a spinning top. Experiments on semi-buoyant wings in water found semicylindrically shaped, refractive microparticles traversed a laser beam and rotated to an illumination-dependent stable orientation. Preliminary tests aid in the development of a calibrated force measurement experiment to directly evaluate the optical forces and torque on these samples. A foundational study of the optical wing, this work contributes to future advancements of flight-by-light.

  4. Integration effects of underwing forward- and rearward-mounted separate-flow, flow-through nacelles on a high-wing transport

    Science.gov (United States)

    Lamb, M.; Abeyounis, W. K.

    1986-01-01

    An experimental investigation was conducted in the Langley 16-Foot Transonic Tunnel at free-stream Mach numbers from 0.70 to 0.82 and angles of attack from -2.5 to 4.0 degrees to determine the integration effects of pylon-mounted underwing forward and rearward separate-flow, flow-through nacelles on a high-wing transonic transport configuration. The results showed that the installed drag of the nacelle/pylon in the rearward location was slightly less than that of the nacelle/pylon in the forward location. This reduction was due to the reduction in calculated skin friction of the nacelle/pylon configuration. In all cases the combined value of form, wave, and interference drag was excessively high. However, the configuration with the nacelle/pylon in a rearward location produced an increase in lift over that of the basic wing-body configuration.

  5. Hovering hummingbird wing aerodynamics during the annual cycle. I. Complete wing.

    Science.gov (United States)

    Achache, Yonathan; Sapir, Nir; Elimelech, Yossef

    2017-08-01

    The diverse hummingbird family (Trochilidae) has unique adaptations for nectarivory, among which is the ability to sustain hover-feeding. As hummingbirds mainly feed while hovering, it is crucial to maintain this ability throughout the annual cycle-especially during flight-feather moult, in which wing area is reduced. To quantify the aerodynamic characteristics and flow mechanisms of a hummingbird wing throughout the annual cycle, time-accurate aerodynamic loads and flow field measurements were correlated over a dynamically scaled wing model of Anna's hummingbird ( Calypte anna ). We present measurements recorded over a model of a complete wing to evaluate the baseline aerodynamic characteristics and flow mechanisms. We found that the vorticity concentration that had developed from the wing's leading-edge differs from the attached vorticity structure that was typically found over insects' wings; firstly, it is more elongated along the wing chord, and secondly, it encounters high levels of fluctuations rather than a steady vortex. Lift characteristics resemble those of insects; however, a 20% increase in the lift-to-torque ratio was obtained for the hummingbird wing model. Time-accurate aerodynamic loads were also used to evaluate the time-evolution of the specific power required from the flight muscles, and the overall wingbeat power requirements nicely matched previous studies.

  6. Identifying the Flow Physics and Modeling Transient Forces on Two-Dimensional Wings

    Science.gov (United States)

    2016-09-02

    understanding the dynamics of these unsteady flows, and uses state-of-the- art techniques, both for measuring these phenomena in experiments (using an... art techniques, both for measuring these phenomena in experiments (using an unsteady wind tunnel at IIT), and for analyzing the data and developing...domain far-field boundary conditions. Computer Methods in Applied Mechanics and Engineering, 197:2131–2146, 2008. [35] Laurent Cordier, El Majd, B

  7. Channel flow analysis. [velocity distribution throughout blade flow field

    Science.gov (United States)

    Katsanis, T.

    1973-01-01

    The design of a proper blade profile requires calculation of the blade row flow field in order to determine the velocities on the blade surfaces. An analysis theory is presented for several methods used for this calculation and associated computer programs that were developed are discussed.

  8. A viscous/potential flow interaction analysis method for multi-element infinite swept wings, volume 1

    Science.gov (United States)

    Dvorak, F. A.; Woodward, F. A.

    1974-01-01

    An analysis method and computer program have been developed for the calculation of the viscosity dependent aerodynamic characteristics of multi-element infinite swept wings in incompressible flow. The wing configuration consisting at the most of a slat, a main element and double slotted flap is represented in the method by a large number of panels. The inviscid pressure distribution about a given configuration in the normal chord direction is determined using a two dimensional potential flow program employing a vortex lattice technique. The boundary layer development over each individual element of the high lift configuration is determined using either integral or finite difference boundary layer techniques. A source distribution is then determined as a function of the calculated boundary layer displacement thickness and pressure distributions. This source distribution is included in the second calculation of the potential flow about the configuration. Once the solution has converged (usually after 2-5 iterations between the potential flow and boundary layer calculations) lift, drag, and pitching moments can be determined as functions of Reynolds number.

  9. Unsteady Aerodynamics of Flapping Wing of a Bird

    Directory of Open Access Journals (Sweden)

    M. Agoes Moelyadi

    2013-04-01

    Full Text Available The unsteady flow behavior and time-dependent aerodynamic characteristics of the flapping motion of a bird’s wing were investigated using a computational method. During flapping, aerodynamic interactions between bird wing surfaces and surrounding flow may occur, generating local time-dependent flow changes in the flow field and aerodynamic load of birds. To study the effect of flapping speed on unsteady aerodynamic load, two kinds of computational simulations were carried out, namely a quasi-steady and an unsteady simulation. To mimic the movement of the down-stroke and the upstroke of a bird, the flapping path accorded to a sinus function, with the wing attitude changing in dihedral angle and time. The computations of time-dependent viscous flow were based on the solution of the Reynolds Averaged Navier-Stokes equations by applying the k-e turbulence model. In addition, the discretization for the computational domain around the model used multi-block structured grid to provide more accuracy in capturing viscous flow, especially in the vicinity of the wing and body surfaces, to obtain a proper wing-body geometry model. For this research, the seagull bird was chosen, which has high aspect ratio wings with pointed wing-tips and a high camber wing section. The results include mesh movement, velocity contours as well as aerodynamic coefficients of the flapping motion of the bird at various flapping frequencies.

  10. Effects of leading-edge flap oscillation on unsteady delta wing flow and rock control

    Science.gov (United States)

    Kandil, Osama A.; Salman, Ahmed A.

    1991-01-01

    The isolated and interdisciplinary problems of unsteady fluid dynamics and rigid-body dynamics and control of delta wings with and without leading-edge flap oscillation are considered. For the fluid dynamics problem, the unsteady, compressible, thin-layer Navier-Stokes (NS) equations, which are written relative to a moving frame of reference, are solved along with the unsteady, linearized, Navier-displacement (ND) equations. The NS equations are solved for the flowfield using an implicit finite-volume scheme. The ND equations are solved for the grid deformation, if the leading-edge flaps oscillate, using an ADI scheme. For the dynamics and control problem, the Euler equation of rigid-body rolling motion for a wing and its flaps are solved interactively with the fluid dynamics equations for the wing-rock motion and subsequently for its control. A four-stage Runge-Kutta scheme is used to explicitly integrate the dynamics equation.

  11. Experimental Investigations on Leading-Edge Vortex Structures for Flow over Non-Slender Delta Wings

    International Nuclear Information System (INIS)

    Jin-Jun, Wang; Wang, Zhang

    2008-01-01

    The dye injection and hydrogen bubble visualization techniques are used to investigate the dual-vortex structure including its development, breakdown and the spatial location of vortex core over nonslender delta wings. It is concluded that the dual-vortex structure can be affected significantly by sweep angle and Reynolds number, and generated only at small angle of attack. The angle between the projection of outer vortex core on delta wing surface and the root chord line has nothing to do with the Reynolds Number and angle of attack, but has simple linear relation with the sweep angle of the model tested. (fundamental areas of phenomenology (including applications))

  12. Flow field mapping in data rack model

    Directory of Open Access Journals (Sweden)

    Matěcha J.

    2013-04-01

    Full Text Available The main objective of this study was to map the flow field inside the data rack model, fitted with three 1U server models. The server model is based on the common four-processor 1U server. The main dimensions of the data rack model geometry are taken fully from the real geometry. Only the model was simplified with respect to the greatest possibility in the experimental measurements. The flow field mapping was carried out both experimentally and numerically. PIV (Particle Image Velocimetry method was used for the experimental flow field mapping, when the flow field has been mapped for defined regions within the 2D/3D data rack model. Ansys CFX and OpenFOAM software were used for the numerical solution. Boundary conditions for numerical model were based on data obtained from experimental measurement of velocity profile at the output of the server mockup. This velocity profile was used as the input boundary condition in the calculation. In order to achieve greater consistency of the numerical model with experimental data, the numerical model was modified with regard to the results of experimental measurements. Results from the experimental and numerical measurements were compared and the areas of disparateness were identified. In further steps the obtained proven numerical model will be utilized for the real geometry of data racks and data.

  13. Installation of flow deflectors and wing baffles to reduce dead zone and enhance flashing light effect in an open raceway pond.

    Science.gov (United States)

    Zhang, Qinghua; Xue, Shengzhang; Yan, Chenghu; Wu, Xia; Wen, Shumei; Cong, Wei

    2015-12-01

    To reduce the dead zone and enhance the flashing light effect, a novel open raceway pond with flow deflectors and wing baffles was developed. The hydrodynamics and light characteristics in the novel open raceway pond were investigated using computational fluid dynamics. Results showed that, compared with the control pond, pressure loss in the flow channel of the pond with optimized flow deflectors decreased by 14.58%, average fluid velocity increased by 26.89% and dead zone decreased by 60.42%. With wing baffles built into the raceway pond, significant swirling flow was produced. Moreover, the period of average L/D cycle was shortened. In outdoor cultivation of freshwater Chlorella sp., the biomass concentration of Chlorella sp. cultivated in the raceway pond with wing baffles was 30.11% higher than that of the control pond. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. A further note on the force discrepancy for wing theory in Euler flow

    Indian Academy of Sciences (India)

    the horseshoe vortices tends to zero, an integral distribution of infinitesimal horseshoe vortices over the vortex sheet is obtained. The contribution to the force on the wing due to the presence of one of the infinitesimal horseshoe vortices in the distribution is focused upon. Most of the algebra in the force calculation is ...

  15. Effects of flexibility and aspect ratio on the aerodynamic performance of flapping wings.

    Science.gov (United States)

    Fu, Junjiang; Liu, Xiaohui; Shyy, Wei; Qiu, Huihe

    2018-01-26

    In the current study, we experimentally investigated the flexibility effects on the aerodynamic performance of flapping wings and the correlation with aspect ratio at angle of attack α = 45o. The Reynolds number based on the chord length and the wing tip velocity is maintained at Re = 5.3x103. Our result for compliant wings with an aspect ratio of 4 shows that wing flexibility can offer improved aerodynamic performance compared to that of a rigid wing. Flexible wings are found to offer higher lift-to-drag ratios; in particular, there is significant reduction in drag with little compromise in lift. The mechanism of the flexibility effects on the aerodynamic performance is addressed by quantifying the aerodynamic lift and drag forces, the transverse displacement on the wings and the flow field around the wings. The regime of the effective stiffness that offers improved aerodynamic performance is quantified in a range of about 0.5~10 and it matches the stiffness of insect wings with similar aspect ratios. Furthermore, we find that the aspect ratio of the wing is the predominant parameter determining the flexibility effects of compliant wings. Compliant wings with an aspect ratio of two do not demonstrate improved performance compared to their rigid counterparts throughout the entire stiffness regime investigated. The correlation between wing flexibility effects and the aspect ratio is supported by the stiffness of real insect wings. © 2018 IOP Publishing Ltd.

  16. A comparison of multicopter and fixed-wing unmanned aerial systems (UAS) applied to mapping debris flows in small alpine catchments

    Science.gov (United States)

    Sotier, Bernadette; Lechner, Veronika

    2016-04-01

    The use of unmanned aerial systems (UAS) for documenting natural hazard events (e.g. debris flows) is becoming increasingly popular, as UAS allow on-demand, flexible and cost-efficient data acquisition. In this paper, we present the results of a comparison of multicopter and fixed-wing UAS. They were employed in the summer of 2015 to map two small alpine catchments located in Western Austria, where debris flows had occurred recently: The first event took place in the Seigesbach (Tyrol), the second occurred in the Plojergraben (Salzburg). For the Seigesbach mission, a fixed-wing UAS (Multiplex Mentor), equipped with a Sony NEX5 (50 mm prime lens, 14 MP sensor resolution) was employed to acquire approximately 4,000 images. In the Plojergraben an AustroDrones X18 octocopter was used, carrying a Sony ILCE-7R (35 mm prime lens, 36 MP sensor resolution) to record 1,700 images. Both sites had a size of approximately 2km². 20 ground control points (GCP) were distributed within both catchments, and their location was measured (Trimble GeoXT, expected accuracy 0.15 m). Using standard structure-from-motion photogrammetry software (AgiSoft PhotoScan Pro, v. 1.1.6), orthophotos (5 cm ground sampling distance - GSD) and digital surface models (DSM) (20 cm GSD) were calculated. Volume differences caused by the debris flow (i.e. deposition heights and erosion depths) computed by subtracting post-event from pre-event DSMs. Even though the terrain conditions in the two catchments were comparable, the challenges during the field campaign and the evaluation of the aerial images were very different. The main difference between the two campaigns was the number of flights required to cover the catchment: only four were needed by the fixed-wing UAS, while the multicopter required eleven in the Plojergraben. The fixed-wing UAS is specially designed for missions in hardly accessible regions, requiring only two people to carry the whole equipment, while in this case a car was needed for the

  17. Determination of pressure and load characteristics of flexible revolving wings by means of tomographic PIV

    NARCIS (Netherlands)

    van de Meerendonk, R.; Perçin, M.; van Oudheusden, B.W.

    2016-01-01

    This study explores the flow field and fluid-dynamic loads generated by revolving low-aspect-ratio wings. The pressure field and load characteristics are successfully reconstructed from the phase-locked tomographic measurements in three independently measured volumes along the span of the wing. The

  18. Numerical Investigation of unsteady inlet flow fields

    Science.gov (United States)

    Hsieh, T.; Wardlaw, A. B., Jr.; Collins, P.; Coakley, T.

    1984-01-01

    The flow field within an unsteady, two-dimensional inlet is studied numerically, using a two dimensional Navier Stokes and a one-dimensional inviscid model. Unsteadiness is introduced by varying the outflow pressure boundary condition. The cases considered include outflow pressure variations which were a single pressure pulse, a rapid increase and a sine function. The amplitude of the imposed exit plane pressure disturbance varied between 1 percent and 20 percent of the mean exit pressure. At the higher levels of pressure fluctuation, the viscous flow field results bore little resemblance to the inviscid ones. The viscous solution included such phenomena as shock trains and bifurcating separation pockets. The induced velocity at the outflow plane predicted by the viscous model differs significantly from accoustical theory or small perturbation results.

  19. Field-flow fractionation of chromosomes

    Energy Technology Data Exchange (ETDEWEB)

    Giddings, J.C.

    1990-09-01

    Research continued on field flow fractionation of chromosomes. Progress in the past year can be organized into three main categories: (1) chromosome sample preparation; (2) preliminary chromosome fractionation; (3) fractionation of a polystyrene aggregate model which approximates the chromosome shape. We have been successful in isolating metaphase chromosomes from the Chinese hamster. We also received a human chromosome sample from Dr. Carolyn Bell-Prince of Los Alamos National Laboratory. Results are discussed. 2 figs.

  20. Structural development of laminar flow control aircraft chordwise wing joint designs

    Science.gov (United States)

    Fischler, J. E.; Jerstad, N. M.; Gallimore, F. H., Jr.; Pollard, T. J.

    1989-01-01

    For laminar flow to be achieved, any protuberances on the surface must be small enough to avoid transition to turbulent flow. However, the surface must have joints between the structural components to allow assembly or replacement of damaged parts, although large continuous surfaces can be utilized to minimize the number the number of joints. Aircraft structural joints usually have many countersunk bolts or rivets on the outer surface. To maintain no mismatch on outer surfaces, it is desirable to attach the components from the inner surface. It is also desirable for the panels to be interchangeable, without the need for shims at the joint, to avoid surface discontinuities that could cause turbulence. Fabricating components while pressing their outer surfaces against an accurate mold helps to ensure surface smoothness and continuity at joints. These items were considered in evaluating the advantages and disadvantages of the joint design concepts. After evaluating six design concepts, two of the leading candidates were fabricated and tested using many small test panels. One joint concept was also built and tested using large panels. The small and large test panel deflections for the leading candidate designs at load factors up to +1.5 g's were well within the step and waviness requirements for avoiding transition.The small panels were designed and tested for compression and tension at -65 F, at ambient conditions, and at 160 F. The small panel results for the three-rib and the sliding-joint concepts indicated that they were both acceptable. The three-rib concept, with tapered splice plates, was considered to be the most practical. A modified three-rib joint that combined the best attributes of previous candidates was designed, developed, and tested. This improved joint met all of the structural strength, surface smoothness, and waviness criteria for laminar flow control (LFC). The design eliminated all disadvantages of the initial three-rib concept except for

  1. Computational Aerodynamic Analysis of a Micro-CT Based Bio-Realistic Fruit Fly Wing

    Science.gov (United States)

    Brandt, Joshua; Doig, Graham; Tsafnat, Naomi

    2015-01-01

    The aerodynamic features of a bio-realistic 3D fruit fly wing in steady state (snapshot) flight conditions were analyzed numerically. The wing geometry was created from high resolution micro-computed tomography (micro-CT) of the fruit fly Drosophila virilis. Computational fluid dynamics (CFD) analyses of the wing were conducted at ultra-low Reynolds numbers ranging from 71 to 200, and at angles of attack ranging from -10° to +30°. It was found that in the 3D bio-realistc model, the corrugations of the wing created localized circulation regions in the flow field, most notably at higher angles of attack near the wing tip. Analyses of a simplified flat wing geometry showed higher lift to drag performance values for any given angle of attack at these Reynolds numbers, though very similar performance is noted at -10°. Results have indicated that the simplified flat wing can successfully be used to approximate high-level properties such as aerodynamic coefficients and overall performance trends as well as large flow-field structures. However, local pressure peaks and near-wing flow features induced by the corrugations are unable to be replicated by the simple wing. We therefore recommend that accurate 3D bio-realistic geometries be used when modelling insect wings where such information is useful. PMID:25954946

  2. Shock/shock interactions between bodies and wings

    Directory of Open Access Journals (Sweden)

    Gaoxiang XIANG

    2018-02-01

    Full Text Available This paper examines the Shock/Shock Interactions (SSI between the body and wing of aircraft in supersonic flows. The body is simplified to a flat wedge and the wing is assumed to be a sharp wing. The theoretical spatial dimension reduction method, which transforms the 3D problem into a 2D one, is used to analyze the SSI between the body and wing. The temperature and pressure behind the Mach stem induced by the wing and body are obtained, and the wave configurations in the corner are determined. Numerical validations are conducted by solving the inviscid Euler equations in 3D with a Non-oscillatory and Non-free-parameters Dissipative (NND finite difference scheme. Good agreements between the theoretical and numerical results are obtained. Additionally, the effects of the wedge angle and sweep angle on wave configurations and flow field are considered numerically and theoretically. The influences of wedge angle are significant, whereas the effects of sweep angle on wave configurations are negligible. This paper provides useful information for the design and thermal protection of aircraft in supersonic and hypersonic flows. Keywords: Body and wing, Flow field, Hypersonic flow, Shock/shock interaction, Wave configurations

  3. A computational study on the influence of insect wing geometry on bee flight mechanics

    Directory of Open Access Journals (Sweden)

    Jeffrey Feaster

    2017-12-01

    Full Text Available Two-dimensional computational fluid dynamics (CFD is applied to better understand the effects of wing cross-sectional morphology on flow field and force production. This study investigates the influence of wing cross-section on insect scale flapping flight performance, for the first time, using a morphologically representative model of a bee (Bombus pensylvanicus wing. The bee wing cross-section was determined using a micro-computed tomography scanner. The results of the bee wing are compared with flat and elliptical cross-sections, representative of those used in modern literature, to determine the impact of profile variation on aerodynamic performance. The flow field surrounding each cross-section and the resulting forces are resolved using CFD for a flight speed range of 1 to 5 m/s. A significant variation in vortex formation is found when comparing the ellipse and flat plate with the true bee wing. During the upstroke, the bee and approximate wing cross-sections have a much shorter wake structure than the flat plate or ellipse. During the downstroke, the flat plate and elliptical cross-sections generate a single leading edge vortex, while the approximate and bee wings generate numerous, smaller structures that are shed throughout the stroke. Comparing the instantaneous aerodynamic forces on the wing, the ellipse and flat plate sections deviate progressively with velocity from the true bee wing. Based on the present findings, a simplified cross-section of an insect wing can misrepresent the flow field and force production. We present the first aerodynamic study using a true insect wing cross-section and show that the wing corrugation increases the leading edge vortex formation frequency for a given set of kinematics.

  4. A computational study on the influence of insect wing geometry on bee flight mechanics.

    Science.gov (United States)

    Feaster, Jeffrey; Battaglia, Francine; Bayandor, Javid

    2017-12-15

    Two-dimensional computational fluid dynamics (CFD) is applied to better understand the effects of wing cross-sectional morphology on flow field and force production. This study investigates the influence of wing cross-section on insect scale flapping flight performance, for the first time, using a morphologically representative model of a bee ( Bombus pensylvanicus ) wing. The bee wing cross-section was determined using a micro-computed tomography scanner. The results of the bee wing are compared with flat and elliptical cross-sections, representative of those used in modern literature, to determine the impact of profile variation on aerodynamic performance. The flow field surrounding each cross-section and the resulting forces are resolved using CFD for a flight speed range of 1 to 5 m/s. A significant variation in vortex formation is found when comparing the ellipse and flat plate with the true bee wing. During the upstroke, the bee and approximate wing cross-sections have a much shorter wake structure than the flat plate or ellipse. During the downstroke, the flat plate and elliptical cross-sections generate a single leading edge vortex, while the approximate and bee wings generate numerous, smaller structures that are shed throughout the stroke. Comparing the instantaneous aerodynamic forces on the wing, the ellipse and flat plate sections deviate progressively with velocity from the true bee wing. Based on the present findings, a simplified cross-section of an insect wing can misrepresent the flow field and force production. We present the first aerodynamic study using a true insect wing cross-section and show that the wing corrugation increases the leading edge vortex formation frequency for a given set of kinematics. © 2017. Published by The Company of Biologists Ltd.

  5. Petiolate wings: effects on the leading-edge vortex in flapping flight.

    Science.gov (United States)

    Phillips, Nathan; Knowles, Kevin; Bomphrey, Richard J

    2017-02-06

    The wings of many insect species including crane flies and damselflies are petiolate (on stalks), with the wing planform beginning some distance away from the wing hinge, rather than at the hinge. The aerodynamic impact of flapping petiolate wings is relatively unknown, particularly on the formation of the lift-augmenting leading-edge vortex (LEV): a key flow structure exploited by many insects, birds and bats to enhance their lift coefficient. We investigated the aerodynamic implications of petiolation P using particle image velocimetry flow field measurements on an array of rectangular wings of aspect ratio 3 and petiolation values of P = 1-3. The wings were driven using a mechanical device, the 'Flapperatus', to produce highly repeatable insect-like kinematics. The wings maintained a constant Reynolds number of 1400 and dimensionless stroke amplitude Λ * (number of chords traversed by the wingtip) of 6.5 across all test cases. Our results showed that for more petiolate wings the LEV is generally larger, stronger in circulation, and covers a greater area of the wing surface, particularly at the mid-span and inboard locations early in the wing stroke cycle. In each case, the LEV was initially arch-like in form with its outboard end terminating in a focus-sink on the wing surface, before transitioning to become continuous with the tip vortex thereafter. In the second half of the wing stroke, more petiolate wings exhibit a more detached LEV, with detachment initiating at approximately 70% and 50% span for P = 1 and 3, respectively. As a consequence, lift coefficients based on the LEV are higher in the first half of the wing stroke for petiolate wings, but more comparable in the second half. Time-averaged LEV lift coefficients show a general rise with petiolation over the range tested.

  6. Mean flow characteristics of two-dimensional wings in ground effect

    Directory of Open Access Journals (Sweden)

    Jae Hwan Jung

    2012-06-01

    Full Text Available The present study numerically investigates the aerodynamic characteristics of two-dimensional wings in the vicinity of the ground by solving two-dimensional steady incompressible Navier-Stokes equations with the turbulence closure model of the realizable k-ε model. Numerical simulations are performed at a wide range of the normalized ground clearance by the chord length (0.1≤h/C ≤ 1.25 for the angles of attack (0° ≤ α ≤ 10° in the pre-stall regime at a Reynolds number (Re of 2×106 based on free stream velocity U∞ and the chord length. As the physical model of this study, a cambered airfoil of NACA 4406 has been selected by a performance test for various airfoils. The maximum lift-to-drag ratio is achieved at α = 4° and h/C = 0.1. Under the conditions of α = 4° and h/C = 0.1, the effect of the Reynolds number on the aerodynamic characteristics of NACA 4406 is investigated in the range of 2× 10 5 ≤ Re ≤ 2× 109. As Re increases, Cl and Cd augments and decreases, respectively, and the lift-to-drag ratio increases linearly.

  7. Flow analysis of vortex generators on wing sections by stereoscopic particle image velocimetry measurements

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Hansen, Martin Otto Laver; Cavar, Dalibor

    2008-01-01

    Stereoscopic particle image velocimetry measurements have been executed in a low speed wind tunnel in spanwise planes in the flow past a row of vortex generators, mounted on a bump in a fashion producing counter-rotating vortices. The measurement technique is a powerful tool which provides all...... to measure and resolve. The flow behaves as expected, in the sense that the vortices transport high momentum fluid into the boundary layer, making it thinner and more resistant to the adverse pressure gradient with respect to separation. The amount of reversed flow is significantly reduced when vortex...

  8. Time Accurate Euler Calculations of Vortical Flow over a Delta Wing in Rolling Motion

    National Research Council Canada - National Science Library

    Fritz, W

    2003-01-01

    .... An important component of the program were the Common Exercises (CE), which promoted the exchange of knowledge between the participating nations and aided the development of computational methods to predict vortical flows...

  9. Estimation of fluid flow fields and their stagnation points

    DEFF Research Database (Denmark)

    Larsen, Rasmus

    Given a temporal sequence of images of fluids we will use local polynomials to regularise obser-vations of normal flows into smooth flow fields. This technique furthermore allows us to give a qualitative local description of the flow field and to estimate the position of stagnation points...

  10. Nonlinear Dynamics of Wind Turbine Wings

    DEFF Research Database (Denmark)

    Larsen, Jesper Winther

    Wind turbines with a nominal effect of 5MW with a rotor diameter of up to 126m are produced today. With the increasing size wind turbines also become more and more optimized with respect to structural dimensions and material usage, without increasing the stiffness proportionally. Consequently......, large wind turbines become increasingly flexible and dynamically sensitive. This project focuses on the structural analysis of highly flexible wind turbine wings, and the aerodynamic loading of wind turbine wings under large changes in flow field due to elastic deformations and changing wind conditions....

  11. Plasma Flows in Crossed Magnetic and Electric Fields

    International Nuclear Information System (INIS)

    Belikov, A.G.

    2005-01-01

    The effect of the magnitude and direction of an external electric field on the plasma flowing through a magnetic barrier is studied by numerically solving two-fluid MHD equations. The drift velocity of the plasma flow and the distribution of the flow electrons over transverse velocities are found to depend on the magnitude and direction of the electric field. It is shown that the direction of the induced longitudinal electric field is determined by the direction of the external field and that the electric current generated by the plasma flow significantly disturbs the barrier field

  12. Effects of Wing Leading Edge Penetration with Venting and Exhaust Flow from Wheel Well at Mach 24 in Flight

    Science.gov (United States)

    Gnoffo, Peter A.

    2003-01-01

    A baseline solution for CFD Point 1 (Mach 24) in the STS-107 accident investigation was modified to include effects of: (1) holes through the leading edge into a vented cavity; and (2) a scarfed, conical nozzle directed toward the centerline of the vehicle from the forward, inboard corner of the landing gear door. The simulations were generated relatively quickly and early in the investigation because simplifications were made to the leading edge cavity geometry and an existing utility to merge scarfed nozzle grid domains with structured baseline external domains was implemented. These simplifications in the breach simulations enabled: (1) a very quick grid generation procedure; and (2) high fidelity corroboration of jet physics with internal surface impingements ensuing from a breach through the leading edge, fully coupled to the external shock layer flow at flight conditions. These simulations provided early evidence that the flow through a two-inch diameter (or larger) breach enters the cavity with significant retention of external flow directionality. A normal jet directed into the cavity was not an appropriate model for these conditions at CFD Point 1 (Mach 24). The breach diameters were of the same order or larger than the local, external boundary-layer thickness. High impingement heating and pressures on the downstream lip of the breach were computed. It is likely that hole shape would evolve as a slot cut in the direction of the external streamlines. In the case of the six-inch diameter breach the boundary layer is fully ingested. The intent of externally directed jet simulations in the second scenario was to approximately model aerodynamic effects of a relatively large internal wing pressure, fueled by combusting aluminum, which deforms the corner of the landing gear door and directs a jet across the windside surface. These jet interactions, in and of themselves, were not sufficiently large to explain observed aerodynamic behavior.

  13. Wind tunnel investigation of the interaction and breakdown characteristics of slender wing vortices at subsonic, transonic, and supersonic speeds

    Science.gov (United States)

    Erickson, Gary E.

    1991-01-01

    The vortex dominated aerodynamic characteristics of a generic 65 degree cropped delta wing model were studied in a wind tunnel at subsonic through supersonic speeds. The lee-side flow fields over the wing-alone configuration and the wing with leading edge extension (LEX) added were observed at M (infinity) equals 0.40 to 1.60 using a laser vapor screen technique. These results were correlated with surface streamline patterns, upper surface static pressure distributions, and six-component forces and moments. The wing-alone exhibited vortex breakdown and asymmetry of the breakdown location at the subsonic and transonic speeds. An earlier onset of vortex breakdown over the wing occurred at transonic speeds due to the interaction of the leading edge vortex with the normal shock wave. The development of a shock wave between the vortex and wing surface caused an early separation of the secondary boundary layer. With the LEX installed, wing vortex breakdown asymmetry did not occur up to the maximum angle of attack in the present test of 24 degrees. The favorable interaction of the LEX vortex with the wing flow field reduced the effects of shock waves on the wing primary and secondary vortical flows. The direct interaction of the wing and LEX vortex cores diminished with increasing Mach number. The maximum attainable vortex-induced pressure signatures were constrained by the vacuum pressure limit at the transonic and supersonic speeds.

  14. Boundary Layer Transition, Separation and Flow Control on Airfoils, Wings and Bodies in CFD, Wind-Tunnel and In-Flight Studies

    Czech Academy of Sciences Publication Activity Database

    Popelka, Lukáš; Matějka, M.; Šimurda, David; Součková, Natálie

    2011-01-01

    Roč. 35, č. 4 (2011), s. 97-104 ISSN 0744-8996 R&D Projects: GA MŠk(CZ) 1M06031; GA AV ČR IAA2076403; GA ČR GA101/08/1112 Institutional research plan: CEZ:AV0Z20760514 Keywords : airfoil * wing-fuselage interaction * flow control Subject RIV: BK - Fluid Dynamics

  15. Wing Tip Drag Reduction at Nominal Take-Off Mach Number: An Approach to Local Active Flow Control with a Highly Robust Actuator System

    Directory of Open Access Journals (Sweden)

    Matthias Bauer

    2016-10-01

    Full Text Available This paper discusses wind tunnel test results aimed at advancing active flow control technology to increase the aerodynamic efficiency of an aircraft during take-off. A model of the outer section of a representative civil airliner wing was equipped with two-stage fluidic actuators between the slat edge and wing tip, where mechanical high-lift devices fail to integrate. The experiments were conducted at a nominal take-off Mach number of M = 0.2. At this incidence velocity, separation on the wing section, accompanied by increased drag, is triggered by the strong slat edge vortex at high angles of attack. On the basis of global force measurements and local static pressure data, the effect of pulsed blowing on the complex flow is evaluated, considering various momentum coefficients and spanwise distributions of the actuation effort. It is shown that through local intensification of forcing, a momentum coefficient of less than c μ = 0.6 % suffices to offset the stall by 2.4°, increase the maximum lift by more than 10% and reduce the drag by 37% compared to the uncontrolled flow.

  16. Aeroelasticity of morphing wings using neural networks

    Science.gov (United States)

    Natarajan, Anand

    In this dissertation, neural networks are designed to effectively model static non-linear aeroelastic problems in adaptive structures and linear dynamic aeroelastic systems with time varying stiffness. The use of adaptive materials in aircraft wings allows for the change of the contour or the configuration of a wing (morphing) in flight. The use of smart materials, to accomplish these deformations, can imply that the stiffness of the wing with a morphing contour changes as the contour changes. For a rapidly oscillating body in a fluid field, continuously adapting structural parameters may render the wing to behave as a time variant system. Even the internal spars/ribs of the aircraft wing which define the wing stiffness can be made adaptive, that is, their stiffness can be made to vary with time. The immediate effect on the structural dynamics of the wing, is that, the wing motion is governed by a differential equation with time varying coefficients. The study of this concept of a time varying torsional stiffness, made possible by the use of active materials and adaptive spars, in the dynamic aeroelastic behavior of an adaptable airfoil is performed here. Another type of aeroelastic problem of an adaptive structure that is investigated here, is the shape control of an adaptive bump situated on the leading edge of an airfoil. Such a bump is useful in achieving flow separation control for lateral directional maneuverability of the aircraft. Since actuators are being used to create this bump on the wing surface, the energy required to do so needs to be minimized. The adverse pressure drag as a result of this bump needs to be controlled so that the loss in lift over the wing is made minimal. The design of such a "spoiler bump" on the surface of the airfoil is an optimization problem of maximizing pressure drag due to flow separation while minimizing the loss in lift and energy required to deform the bump. One neural network is trained using the CFD code FLUENT to

  17. Unsteady fluid dynamics around a hovering wing

    Science.gov (United States)

    Krishna, Swathi; Green, Melissa; Mulleners, Karen

    2017-11-01

    The unsteady flow around a hovering flat plate wing has been investigated experimentally using particle image velocimetry and direct force measurements. The measurements are conducted on a wing that rotates symmetrically about the stroke reversal at a reduced frequency of k = 0.32 and Reynolds number of Re = 220 . The Lagrangian finite-time Lyapunov exponent method is used to analyse the unsteady flow fields by identifying dynamically relevant flow features such as the primary leading edge vortex (LEV), secondary vortices, and topological saddles, and their evolution within a flapping cycle. The flow evolution is divided into four stages that are characterised by the LEV (a)emergence, (b)growth, (c)lift-off, and (d)breakdown and decay. Tracking saddle points is shown to be helpful in defining the LEV lift-off which occurs at the maximum stroke velocity. The flow fields are correlated with the aerodynamic forces revealing that the maximum lift and drag are observed just before LEV lift-off. The end of wing rotation in the beginning of the stroke stimulates a change in the direction of the LEV growth and the start of rotation at the end of the stroke triggers the breakdown of the LEV.

  18. Estimation of Centers and Stagnation points in optical flow fields

    DEFF Research Database (Denmark)

    Larsen, Rasmus

    1997-01-01

    distribution of spatio-temporal energy, which is sampled using a set of spatio-temporal quadrature filters. These observations of normal flows are then integrated into smooth flow fields by locally approximating first order polynomials in the spatial coordinates to the flow vectors. This technique furthermore......In a topological sense fluid flows are characterised by their stagnation points. Given a temporal sequence of images of fluids we will consider the application of local polynomials to the estimation of smooth fluid flow fields. The normal flow at intensity contours is estimated from the local...... allows us to give a qualitative local description of the flow field and to estimate the position of stagnation points (e.g. nodes, saddles, and centers). We will apply the algorithm to two data sets. The first sequence consists of infrared images from the meteorological satellite Meteosat. Here...

  19. Effects of local flow field on flow accelerated corrosion. Effect of flow velocity on corrosion rate

    International Nuclear Information System (INIS)

    Nagaya, Yukinori; Nakamura, Akira; Murase, Michio; Utanohara, Yoichi

    2010-01-01

    Flow accelerated corrosion (FAC) is one of important issues for aging of nuclear power plants. In this study, in order to evaluate the effects of flow field on corrosion rate due to FAC, corrosion rates downstream of an orifice were measured using an electric resistance method. In these experiments, a test loop under high temperature and high pressure conditions was used. The pipe inner diameter was 50 mm and the ratio of orifice diameter which was 24.3 mm to the pipe diameter was about 0.5. The water temperature was controlled at 150 within ± 1 degC. To evaluate the effect of flow velocity on FAC rate, we carried out two series of measurements. During each period of measurements, we changed the flow velocity from 1.4 to 5.0 m/s, or from 2.1 to 3.5 m/s. In these results, FAC rates downstream of the orifice increased remarkably by increasing the flow velocity, while the changes of FAC rates upstream were little. The results show a possibility that the effect of flow velocity on FAC rate in the upstream of the orifice is different from that in the downstream. It turned out that the maximum FAC rate downstream of the orifice is proportional to Re 0.82 in the range of Reynolds number, Re=3.5x10 5 - 1.3x10 6 . However these measurement results might be different on the little difference of water quality or the difference of initial conditions of sensor surface, therefore we have to evaluate these effects in the future. We confirmed that FAC rates downstream of the orifice can possibly be evaluated by the parameter based on the flow velocity. (author)

  20. Geology of the Tyrrhenus Mons Lava Flow Field, Mars

    Science.gov (United States)

    Crown, David A.; Mest, Scott C.

    2014-11-01

    The ancient, eroded Martian volcano Tyrrhenus Mons exhibits a central caldera complex, layered flank deposits dissected by radial valleys, and a 1000+ km-long flow field extending to the southwest toward Hellas Planitia. Past studies suggested an early phase of volcanism dominated by large explosive eruptions followed by subsequent effusive activity at the summit and to the southwest. As part of a new geologic mapping study of northeast Hellas, we are examining the volcanic landforms and geologic evolution of the Tyrrhenus Mons flow field, including the timing and nature of fluvial activity and effects on volcanic units. New digital geologic mapping incorporates THEMIS IR (100 m/pixel) and CTX (5 m/pixel) images as well as constraints from MOLA topography.Mapping results to-date include delineation of the boundaries of the flow field, identification and mapping of volcanic and erosional channels within the flow field, and mapping and analysis of lava flow lobes. THEMIS IR and CTX images allow improved discrimination of the numerous flow lobes that are observed in the flow field, including refinement of the margins of previously known flows and identification of additional and smaller lobes. A prominent sinuous rille extending from Tyrrhenus Mons’ summit caldera is a major feature that supplied lava to the flow field. Smaller volcanic channels are common throughout the flow field; some occur in segments along crests of local topographic highs and may delineate lava tubes. In addition to volcanic channels, the flow field surface is characterized by several types of erosional channels, including wide troughs with scour marks, elongate sinuous channels, and discontinuous chains of elongate pits and troughs. High-resolution images reveal the widespread and significant effects of fluvial activity in the region, and further mapping studies will examine spatial and temporal interactions between volcanism and fluvial processes.

  1. Experimental investigation of heat transfer and fluid flow behaviour in multiple square perforated twisted tape with square wing inserts heat exchanger tube

    Science.gov (United States)

    Suri, Amar Raj Singh; Kumar, Anil; Maithani, Rajesh

    2018-01-01

    The present work deals with experimental investigation of heat transfer and fluid flow characteristics of multiple square perforated twisted tape with wing inserts in a heat exchanger tube. The range of selected geometrical parameters are, perforation width ratio (a/WT) of 0.083-0.333, twist ratio (TL/WT) of 2.0-3.5, wing depth ratio (Wd/WT) of 0.042-0.167 and number of twisted tapes (TP) of 4. The Reynolds number (Ren) selected for experimentation ranges from 5000 to 27,000. The maximum heat transfer and friction factor enhancement was found to be 6.96 and 8.34 times that of plane tube, respectively. The maximum heat transfer enhancement is observed at a a/WT of 0.250, TL/WT of 2.5, and Wd/WT of 0.167.

  2. Rice- and butterfly-wing effect inspired self-cleaning and low drag micro/nanopatterned surfaces in water, oil, and air flow

    Science.gov (United States)

    Bixler, Gregory D.; Bhushan, Bharat

    2013-12-01

    In search of new solutions to complex challenges, researchers are turning to living nature for inspiration. For example, special surface characteristics of rice leaves and butterfly wings combine the shark skin (anisotropic flow leading to low drag) and lotus leaf (superhydrophobic and self-cleaning) effects, producing the so-called rice and butterfly wing effect. In this paper, we study four microstructured surfaces inspired by rice leaves and fabricated with photolithography techniques. We also present a method of creating such surfaces using a hot embossing procedure for scaled-up manufacturing. Fluid drag, self-cleaning, contact angle, and contact angle hysteresis data are presented to understand the role of sample geometrical dimensions. Conceptual modeling provides design guidance when developing novel low drag, self-cleaning, and potentially antifouling surfaces for medical, marine, and industrial applications.

  3. Wake patterns of the wings and tail of hovering hummingbirds

    Science.gov (United States)

    Altshuler, Douglas L.; Princevac, Marko; Pan, Hansheng; Lozano, Jesse

    The flow fields of slowly flying bats and fasterflying birds differ in that bats produce two vortex loops during each stroke, one per wing, and birds produce a single vortex loop per stroke. In addition, the circulation at stroke transition approaches zero in bats but remains strong in birds. It is unknown if these difference derive from fundamental differences in wing morphology or are a consequence of flight speed. Here, we present an analysis of the horizontal flow field underneath hovering Anna's hummingbirds (Calypte anna) to describe the wake of a bird flying at zero forward velocity. We also consider how the hummingbird tail interacts with the wake generated by the wings. High-speed image recording and analysis from three orthogonal perspectives revealed that the wing tips reach peak velocities in the middle of each stroke and approach zero velocity at stroke transition. Hummingbirds use complex tail kinematic patterns ranging from in phase to antiphase cycling with respect to the wings, covering several phase shifted patterns. We employed particle image velocimetry to attain detailed horizontal flow measurements at three levels with respect to the tail: in the tail, at the tail tip, and just below the tail. The velocity patterns underneath the wings indicate that flow oscillates along the ventral-dorsal axis in response to the down- and up-strokes and that the sideways flows with respect to the bird are consistently from the lateral to medial. The region around the tail is dominated by axial flows in dorsal to ventral direction. We propose that these flows are generated by interaction between the wakes of the two wings at the end of the upstroke, and that the tail actively defects flows to generate moments that contribute to pitch stability. The flow fields images also revealed distinct vortex loops underneath each wing, which were generated during each stroke. From these data, we propose a model for the primary flow structures of hummingbirds that more

  4. Optimization Design of Bipolar Plate Flow Field in PEM Stack

    Science.gov (United States)

    Wen, Ming; He, Kanghao; Li, Peilong; Yang, Lei; Deng, Li; Jiang, Fei; Yao, Yong

    2017-12-01

    A new design of bipolar plate flow field in proton exchange membrane (PEM) stack was presented to develop a high-performance transfer efficiency of the two-phase flow. Two different flow fields were studied by using numerical simulations and the performance of the flow fields was presented. the hydrodynamic properties include pressure gap between inlet and outlet, the Reynold’s number of the two types were compared based on the Navier–Stokes equations. Computer aided optimization software was implemented in the design of experiments of the preferable flow field. The design of experiments (DOE) for the favorable concept was carried out to study the hydrodynamic properties when changing the design parameters of the bipolar plate.

  5. Dynamics of Deformable Active Particles under External Flow Field

    Science.gov (United States)

    Tarama, Mitsusuke

    2017-10-01

    In most practical situations, active particles are affected by their environment, for example, by a chemical concentration gradient, light intensity, gravity, or confinement. In particular, the effect of an external flow field is important for particles swimming in a solvent fluid. For deformable active particles such as self-propelled liquid droplets and active vesicles, as well as microorganisms such as euglenas and neutrophils, a general description has been developed by focusing on shape deformation. In this review, we present our recent studies concerning the dynamics of a single active deformable particle under an external flow field. First, a set of model equations of active deformable particles including the effect of a general external flow is introduced. Then, the dynamics under two specific flow profiles is discussed: a linear shear flow, as the simplest example, and a swirl flow. In the latter case, the scattering dynamics of the active deformable particles by the swirl flow is also considered.

  6. Aerodynamic performance and particle image velocimetery of piezo actuated biomimetic manduca sexta engineered wings towards the design and application of a flapping wing flight vehicle

    Science.gov (United States)

    DeLuca, Anthony M.

    Considerable research and investigation has been conducted on the aerodynamic performance, and the predominate flow physics of the Manduca Sexta size of biomimetically designed and fabricated wings as part of the AFIT FWMAV design project. Despite a burgeoning interest and research into the diverse field of flapping wing flight and biomimicry, the aerodynamics of flapping wing flight remains a nebulous field of science with considerable variance into the theoretical abstractions surrounding aerodynamic mechanisms responsible for aerial performance. Traditional FWMAV flight models assume a form of a quasi-steady approximation of wing aerodynamics based on an infinite wing blade element model (BEM). An accurate estimation of the lift, drag, and side force coefficients is a critical component of autonomous stability and control models. This research focused on two separate experimental avenues into the aerodynamics of AFIT's engineered hawkmoth wings|forces and flow visualization. 1. Six degree of freedom force balance testing, and high speed video analysis was conducted on 30°, 45°, and 60° angle stop wings. A novel, non-intrusive optical tracking algorithm was developed utilizing a combination of a Gaussian Mixture Model (GMM) and ComputerVision (OpenCV) tools to track the wing in motion from multiple cameras. A complete mapping of the wing's kinematic angles as a function of driving amplitude was performed. The stroke angle, elevation angle, and angle of attack were tabulated for all three wings at driving amplitudes ranging from A=0.3 to A=0.6. The wing kinematics together with the force balance data was used to develop several aerodynamic force coefficient models. A combined translational and rotational aerodynamic model predicted lift forces within 10%, and vertical forces within 6%. The total power consumption was calculated for each of the three wings, and a Figure of Merit was calculated for each wing as a general expression of the overall efficiency of

  7. Streamwise-body-force-model for rapid simulation combining internal and external flow fields

    Directory of Open Access Journals (Sweden)

    Cui Rong

    2016-10-01

    Full Text Available A streamwise-body-force-model (SBFM is developed and applied in the overall flow simulation for the distributed propulsion system, combining internal and external flow fields. In view of axial stage effects, fan or compressor effects could be simplified as body forces along the streamline. These body forces which are functions of local parameters could be added as source terms in Navier-Stokes equations to replace solid boundary conditions of blades and hubs. The validation of SBFM with uniform inlet and distortion inlet of compressors shows that pressure performance characteristics agree well with experimental data. A three-dimensional simulation of the integration configuration, via a blended wing body aircraft with a distributed propulsion system using the SBFM, has been completed. Lift coefficient and drag coefficient agree well with wind tunnel test results. Results show that to reach the goal of rapid integrated simulation combining internal and external flow fields, the computational fluid dynamics method based on SBFM is reasonable.

  8. Propulsion efficiency and imposed flow fields of a copepod jump

    DEFF Research Database (Denmark)

    Jiang, H.; Kiørboe, Thomas

    2011-01-01

    the imposed flow fields and associated energetics of jumps by means of computational fluid dynamics simulations by modeling the copepod as a self-propelled body. The computational fluid dynamics simulation was validated by particle image velocimetry data. The flow field generated by a repositioning jump...... velocity vectors pointing towards the copepod; such a flow field may inform the predator of the whereabouts of the escaping copepod prey. High Froude propulsion efficiency (0.94–0.98) was obtained for individual power stroke durations of all simulated jumps. This is unusual for small aquatic organisms...

  9. PIV Measurements of Gas Flow Fields from Burning End

    Science.gov (United States)

    Huang, Yifei; Wu, Junzhang; Zeng, Jingsong; Tang, Darong; Du, Liang

    2017-12-01

    To study the influence of cigarette gas on the environment, it is necessary to know the cigarette gas flow fields from burning end. By using PIV technique, in order to reveal velocity characteristics of gas flow fields, the velocities of cigarette gas flow fields was analyzed with different stepping motor frequencies corresponding to suction pressures, and the trend of velocity has been given with image fitting. The results shows that the velocities of the burning end increased with suction pressures; Between velocities of the burning end and suction pressures, the relations present polynomial rule; The cigarette gas diffusion in combustion process is faster than in the smoldering process.

  10. Modulating patterns of two-phase flow with electric fields.

    Science.gov (United States)

    Liu, Dingsheng; Hakimi, Bejan; Volny, Michael; Rolfs, Joelle; Anand, Robbyn K; Turecek, Frantisek; Chiu, Daniel T

    2014-07-01

    This paper describes the use of electro-hydrodynamic actuation to control the transition between three major flow patterns of an aqueous-oil Newtonian flow in a microchannel: droplets, beads-on-a-string (BOAS), and multi-stream laminar flow. We observed interesting transitional flow patterns between droplets and BOAS as the electric field was modulated. The ability to control flow patterns of a two-phase fluid in a microchannel adds to the microfluidic tool box and improves our understanding of this interesting fluid behavior.

  11. Taylor-Couette flow stability with toroidal magnetic field

    International Nuclear Information System (INIS)

    Shalybkov, D

    2005-01-01

    The linear stability of the dissipative Taylor-Couette flow with imposed azimuthal magnetic field is considered. Unlike to ideal flow, the magnetic field is fixed function of radius with two parameters only: a ratio of inner to outer cylinder radii and a ratio of the magnetic field values on outer and inner cylinders. The magnetic field with boundary values ratio greater than zero and smaller than inverse radii ratio always stabilizes the flow and called stable magnetic field below. The current free magnetic field is the stable magnetic field. The unstable magnetic field destabilizes every flow if the magnetic field (or Hartmann number) exceeds some critical value. This instability survives even without rotation (for zero Reynolds number). For the stable without the magnetic field flow, the unstable modes are located into some interval of the vertical wave numbers. The interval length is zero for critical Hartmann number and increases with increasing Hartmann number. The critical Hartmann numbers and the length of the unstable vertical wave numbers interval is the same for every rotation law. There are the critical Hartmann numbers for m = 0 sausage and m = 1 kink modes only. The critical Hartmann numbers are smaller for kink mode and this mode is the most unstable mode like to the pinch instability case. The flow stability do not depend on the magnetic Prandtl number for m = 0 mode. The same is true for critical Hartmann numbers for m = 0 and m = 1 modes. The typical value of the magnetic field destabilizing the liquid metal Taylor-Couette flow is order of 100 Gauss

  12. Combined, nonlinear aerodynamic and structural method for the aeroelastic design of a three-dimensional wing in supersonic flow

    Science.gov (United States)

    Pittman, J. L.; Giles, G. L.

    1986-01-01

    An iterative procedure for the static aeroelastic design of a flexible wing at supersonic speeds has been developed. The procedure combines a nonlinear, full-potential solver (NCOREL) with an equivalent plate structural analysis method. The NCOREL method yields significantly improved aerodynamic estimates compared to linear theory. The equivalent plate structural analysis method demonstrates an order of magnitude reduction in computer memory and execution time compared to finite-element methods. A highly swept wing is analyzed at high lift using this aeroelastic procedure. The results indicate that the wing deforms favorably due to aerodynamic loading and, consequently, that the inviscid drag levels do not vary at the required lift coefficient although the angle of attack varies significantly. A sensitivity analysis of the type required for optimization studies was also performed with the aeroelastic design procedure.

  13. Calculating Study of the Turbine at Last Stage Flow Field in the Small Volume Flow Condition

    Directory of Open Access Journals (Sweden)

    Jiang Tieliu

    2017-11-01

    Full Text Available Based on basic equation and boundary layer theory of pneumodynamics, the thesis conducts numerical modeling and theoretical analysis on the last stage of turbine characteristics at a small volume flow by using FLUENT, gives an emphasized analysis on the position of first occurrence of backflow and its expansion direction and comes up with flow structure of the turbine flow field at last stage in the small volume flow condition. In connection with specific experiments, it puts forward the flow model of backflow occurring in the last stage field and the solution to the model. The flow field at last stage for a 100MW turbine in the small volume flow condition that is calculated by using the model is basically in conformity to the actual result.

  14. Effect of external jet-flow deflector geometry on OTW aero-acoustic characteristics. [Over-The-Wing

    Science.gov (United States)

    Von Glahn, U.; Groesbeck, D.

    1976-01-01

    The effect of geometry variations in the design of external deflectors for use with OTW configurations was studied at model scale and subsonic jet velocities. Included in the variations were deflector size and angle as well as wing size and flap setting. A conical nozzle (5.2-cm diameter) mounted at 0.1 chord above and downstream of the wing leading edges was used. The data indicate that external deflectors provide satisfactory take-off and approach aerodynamic performance and acoustic characteristics for OTW configurations. These characteristics together with expected good cruise aerodynamics, since external deflectors are storable, may provide optimum OTW design configurations.

  15. Sequence recombination and conservation of Varroa destructor virus-1 and deformed wing virus in field collected honey bees (Apis mellifera.

    Directory of Open Access Journals (Sweden)

    Hui Wang

    Full Text Available We sequenced small (s RNAs from field collected honeybees (Apis mellifera and bumblebees (Bombuspascuorum using the Illumina technology. The sRNA reads were assembled and resulting contigs were used to search for virus homologues in GenBank. Matches with Varroadestructor virus-1 (VDV1 and Deformed wing virus (DWV genomic sequences were obtained for A. mellifera but not B. pascuorum. Further analyses suggested that the prevalent virus population was composed of VDV-1 and a chimera of 5'-DWV-VDV1-DWV-3'. The recombination junctions in the chimera genomes were confirmed by using RT-PCR, cDNA cloning and Sanger sequencing. We then focused on conserved short fragments (CSF, size > 25 nt in the virus genomes by using GenBank sequences and the deep sequencing data obtained in this study. The majority of CSF sites confirmed conservation at both between-species (GenBank sequences and within-population (dataset of this study levels. However, conserved nucleotide positions in the GenBank sequences might be variable at the within-population level. High mutation rates (Pi>10% were observed at a number of sites using the deep sequencing data, suggesting that sequence conservation might not always be maintained at the population level. Virus-host interactions and strategies for developing RNAi treatments against VDV1/DWV infections are discussed.

  16. On the flow magnitude and field-flow alignment at Earth's core surface

    DEFF Research Database (Denmark)

    Finlay, Chris; Amit, H.

    We present a method to estimate the typical magnitude of flow close toEarth's core surface based on observational knowledge of the maingeomagnetic field (MF) and its secular variation (SV), together withprior information concerning field-flow alignment gleaned from numericaldynamo models. An expr......We present a method to estimate the typical magnitude of flow close toEarth's core surface based on observational knowledge of the maingeomagnetic field (MF) and its secular variation (SV), together withprior information concerning field-flow alignment gleaned from numericaldynamo models...... geomagnetic field model gufm1for the interval 1840.0 - 1990.0, the method predicts temporalvariations in flow magnitude similar to those found in earlier studies.The calculations rely primarily on knowledge of the MF and SV spectra;by extrapolating these beyond observed scales the influence of smallscales...

  17. Experimental studies of vertical mixing patterns in open channel flow generated by two delta wings side-by-side

    Science.gov (United States)

    Vaughan, Garrett

    Open channel raceway bioreactors are a low-cost system used to grow algae for biofuel production. Microalgae have many promises when it comes to renewable energy applications, but many economic hurdles must be overcome to achieve an economic fuel source that is competitive with petroleum-based fuels. One way to make algae more competitive is to improve vertical mixing in algae raceway bioreactors. Previous studies show that mixing may be increased by the addition of mechanisms such as airfoils. The circulation created helps move the algae from the bottom to top surface for necessary photosynthetic exchange. This improvement in light utilization allowed a certain study to achieve 2.2-2.4 times the amount of biomass relative to bioreactors without airfoils. This idea of increasing mixing in open channel raceways has been the focus of the Utah State University (USU) raceway hydraulics group. Computational Fluid Dynamics (CFD), Acoustic Doppler Velocimetry (ADV), and Particle Image Velocimetry (PIV) are all methods used at USU to computationally and experimentally quantify mixing in an open channel raceway. They have also been used to observe the effects of using delta wings (DW) in increasing vertical mixing in the raceway. These efforts showed great potential in the DW in increasing vertical mixing in the open channel bioreactor. However, this research begged the question, does the DW help increase algae growth? Three algae growth experiments comparing growth in a raceway with and without DW were completed. These experiments were successful, yielding an average 27.1% increase in the biomass. The DW appears to be a promising method of increasing algae biomass production. The next important step was to quantify vertical mixing and understand flow patterns due to two DWs side-by-side. Raceway channels are wider as they increase in size; and arrays of DWs will need to be installed to achieve quality mixing throughout the bioreactor. Quality mixing was attained for

  18. Josephson flux-flow oscillators in nonuniform microwave fields

    DEFF Research Database (Denmark)

    Salerno, Mario; Samuelsen, Mogens Rugholm

    2000-01-01

    We present a simple theory for Josephson flux-flow oscillators in the presence of nonuniform microwave fields. In particular we derive an analytical expression for the I-V characteristic of the oscillator from which we show that satellite steps are spaced around the main flux-flow resonance by only...

  19. The electromagnetic force field, fluid flow field and temperature profiles in levitated metal droplets

    Science.gov (United States)

    El-Kaddah, N.; Szekely, J.

    1982-01-01

    A mathematical representation was developed for the electromagnetic force field, the flow field, the temperature field (and for transport controlled kinetics), in a levitation melted metal droplet. The technique of mutual inductances was employed for the calculation of the electromagnetic force field, while the turbulent Navier - Stokes equations and the turbulent convective transport equations were used to represent the fluid flow field, the temperature field and the concentration field. The governing differential equations, written in spherical coordinates, were solved numerically. The computed results were in good agreement with measurements, regarding the lifting force, and the average temperature of the specimen and carburization rates, which were transport controlled.

  20. Effect of square wings in multiple square perforated twisted tapes on fluid flow and heat transfer of heat exchanger tube

    Directory of Open Access Journals (Sweden)

    Amar Raj Singh Suri

    2017-09-01

    Full Text Available This work presents, an experimental study on Nusselt number (Nurs and friction factor (frs of heat exchanger circular tube fitted with multiple square perforated with square wing twisted tape inserts. The experimental determination encompassed the geometrical parameters namely, wing depth ratio (Wd/WT of 0.042–0.167, perforation width ratio (a/WT of 0.250, twist ratio (TL/WT of 2.5, and number of twisted tapes (NT of 4.0. The effect of multiple square perforated twisted tape with square wing has been investigated for the range of Reynolds number (Ren varied from 5000 to 27,000. The maximum enhancement in Nurs and frs is observed to be 6.96 and 8.34 times of that of the plain circular tube, respectively. Correlations of Nurs, frs and ηp are established in term of Ren and geometrical parameters of wings twisted tape which can be used to predict the values of Nurs, frs and ηp with considerably good accuracy.

  1. Waving Wing Aerodynamics at Low Reynolds Numbers

    Science.gov (United States)

    2010-07-01

    wing. An attached leading edge vortex has been observed by multiple research groups on both mechanical wing flappers (8; 22; 21; 4) and revolving wing...observed by Ellington et al. (8) in their earlier experiments on the mechanical hawkmoth flapper at Re ≈ 10,000. In these experiments the spanwise flow...on mechanical wing flappers at similar Reynolds numbers, Re ≈ 1,000 and 1,400 respectively. Both sets of experiments revealed a stable attached

  2. Polymer electrolyte fuel cells: flow field for efficient air operation

    Energy Technology Data Exchange (ETDEWEB)

    Buechi, F.N.; Tsukada, A.; Haas, O.; Scherer, G.G. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    A new flow field was designed for a polymer electrolyte fuel cell stack with an active area of 200 cm{sup 2} for operation at low air stoichiometry and low air over pressure. Optimum of gas flow and channel dimensions were calculated based on the required pressure drop in the fluid. Single cells and a bi-cell stack with the new flow field show an improved current/voltage characteristic when operated at low air stoichiometries as compared to that of the previous non optimized design. (author) 4 figs., 3 refs.

  3. Time to Spread Your Wings: A Review of the Avian Ancient DNA Field

    Directory of Open Access Journals (Sweden)

    Alicia Grealy

    2017-07-01

    Full Text Available Ancient DNA (aDNA has the ability to inform the evolutionary history of both extant and extinct taxa; however, the use of aDNA in the study of avian evolution is lacking in comparison to other vertebrates, despite birds being one of the most species-rich vertebrate classes. Here, we review the field of “avian ancient DNA” by summarising the past three decades of literature on this topic. Most studies over this time have used avian aDNA to reconstruct phylogenetic relationships and clarify taxonomy based on the sequencing of a few mitochondrial loci, but recent studies are moving toward using a comparative genomics approach to address developmental and functional questions. Applying aDNA analysis with more practical outcomes in mind (such as managing conservation is another increasingly popular trend among studies that utilise avian aDNA, but the majority of these have yet to influence management policy. We find that while there have been advances in extracting aDNA from a variety of avian substrates including eggshell, feathers, and coprolites, there is a bias in the temporal focus; the majority of the ca. 150 studies reviewed here obtained aDNA from late Holocene (100–1000 yBP material, with few studies investigating Pleistocene-aged material. In addition, we identify and discuss several other issues within the field that require future attention. With more than one quarter of Holocene bird extinctions occurring in the last several hundred years, it is more important than ever to understand the mechanisms driving the evolution and extinction of bird species through the use of aDNA.

  4. Pedestrian Flow in the Mean Field Limit

    KAUST Repository

    Haji Ali, Abdul Lateef

    2012-11-01

    We study the mean-field limit of a particle-based system modeling the behavior of many indistinguishable pedestrians as their number increases. The base model is a modified version of Helbing\\'s social force model. In the mean-field limit, the time-dependent density of two-dimensional pedestrians satisfies a four-dimensional integro-differential Fokker-Planck equation. To approximate the solution of the Fokker-Planck equation we use a time-splitting approach and solve the diffusion part using a Crank-Nicholson method. The advection part is solved using a Lax-Wendroff-Leveque method or an upwind Backward Euler method depending on the advection speed. Moreover, we use multilevel Monte Carlo to estimate observables from the particle-based system. We discuss these numerical methods, and present numerical results showing the convergence of observables that were calculated using the particle-based model as the number of pedestrians increases to those calculated using the probability density function satisfying the Fokker-Planck equation.

  5. Transverse Flow of Gluon Fields in Heavy Ion Collision

    Science.gov (United States)

    Chen, Guangyao; Fries, Rainer J.

    2014-09-01

    We describe the dynamics of initial gluon fields in heavy ion collision using a formal recursive solution of the Yang Mills equations and solving for the energy momentum tensor analytically in a boost-invariant setup. We generalize the original McLerran-Venugopalan (MV) model in order to allow for realistic nuclear profiles. This leads to a transverse flow of gluon fields. This flow pattern is inherited by the quark gluon plasma fluid after thermalization. Its most interesting aspect is a rapidity-odd flow component. We show that this rapidity-odd flow does not break boost invariance and that it emerges naturally from the Yang Mills equations. It leads to directed flow of particles and introduces angular momentum to the system.

  6. Instabilities in the flow past localized magnetic fields

    International Nuclear Information System (INIS)

    Beltran, Alberto; Cuevas, Sergio; Smolentsev, Sergey

    2007-01-01

    The flow in a shallow layer of an electrically conducting fluid past a localized magnetic field is analyzed numerically. The field occupies only a small fraction of the total flow domain and resemblances the magnetic field created by a permanent magnet located close to the fluid layer. Two different physical cases are considered. In the first one, the fluid layer is free from externally injected electric currents, therefore, only induced currents are present. In the second case, an external electric current is injected to the fluid layer, transversally to the main flow direction. It is shown that the Lorentz force created by the interaction of the electric currents with the non-uniform magnetic field acts as an obstacle for the flow and creates different flow patterns similar to those observed in the flow past bluff bodies. A quasi-two-dimensional model that takes into account the existence of the bottom wall through a linear Hartmann-Rayleigh friction term is considered. When inertial and magnetic forces are strong enough, the wake formed behind the zone of high magnetic field is destabilized and a periodic vortex shedding similar to the classical von Karman street is found. The effect of Hartmann-Rayleigh friction in the emergence of the instability is analyzed

  7. Instabilities in the flow past localized magnetic fields

    Science.gov (United States)

    Beltrán, Alberto; Cuevas, Sergio; Smolentsev, Sergey

    2007-04-01

    The flow in a shallow layer of an electrically conducting fluid past a localized magnetic field is analyzed numerically. The field occupies only a small fraction of the total flow domain and resemblances the magnetic field created by a permanent magnet located close to the fluid layer. Two different physical cases are considered. In the first one, the fluid layer is free from externally injected electric currents, therefore, only induced currents are present. In the second case, an external electric current is injected to the fluid layer, transversally to the main flow direction. It is shown that the Lorentz force created by the interaction of the electric currents with the non-uniform magnetic field acts as an obstacle for the flow and creates different flow patterns similar to those observed in the flow past bluff bodies. A quasi-two-dimensional model that takes into account the existence of the bottom wall through a linear Hartmann-Rayleigh friction term is considered. When inertial and magnetic forces are strong enough, the wake formed behind the zone of high magnetic field is destabilized and a periodic vortex shedding similar to the classical von Kármán street is found. The effect of Hartmann-Rayleigh friction in the emergence of the instability is analyzed.

  8. Numerical simulation of interior flow field of nuclear model pump

    International Nuclear Information System (INIS)

    Wang Chunlin; Peng Na; Kang Can; Zhao Baitong; Zhang Hao

    2009-01-01

    Reynolds time-averaged N-S equations and the standard k-ε turbulent model were adopted, and three-dimensional non-structural of tetrahedral mesh division was used for modeling. Multiple reference frame model of rotating fluid mechanical model was used, under the design condition, the three-dimensional incompressible turbulent flow of nuclear model pump was simulated, and the results preferably post the characteristics of the interior flow field. This paper first analyzes the total pressure and velocity distribution in the flow field, and then describes the interior flow field characteristics of each part such as the impeller, diffuser and spherical shell, and also discusses the reasons that cause these characteristics. The study results can be used to estimate the performance of nuclear model pump, and will provide some useful references for its hydraulic optimized design. (authors)

  9. Numerical analysis of flow fields generated by accelerating flames

    Energy Technology Data Exchange (ETDEWEB)

    Kurylo, J.

    1977-12-01

    Presented here is a numerical technique for the analysis of non-steady flow fields generated by accelerating flames in gaseous media. Of particular interest in the study is the evaluation of the non-steady effects on the flow field and the possible transition of the combustion process to detonation caused by an abrupt change in the burning speed of an initially steady flame propagating in an unconfined combustible gas mixture. Optically recorded observations of accelerating flames established that the flow field can be considered to consist of non-steady flow fields associated with an assembly of interacting shock waves, contact discontinuities, deflagration and detonation fronts. In the analysis, these flow fields are treated as spatially one-dimensional, the influence of transport phenomena is considered to be negligible, and unburned and burned substances are assumed to behave as perfect gases with constant, but different, specific heats. The basis of the numerical technique is an explicit, two step, second order accurate, finite difference scheme employed to integrate the flow field equations expressed in divergence form. The burning speed, governing the motion of the deflagration, is expressed in the form of a power law dependence on pressure and temperature immediately ahead of its front. The steady wave solution is obtained by the vector polar interaction technique, that is, by determining the point of intersection between the loci of end states in the plane of the two interaction invariants, pressure and particle velocity. The technique is illustrated by a numerical example in which a steady flame experiences an abrupt change in its burning speed. Solutions correspond either to the eventual reestablishment of a steady state flow field commensurate with the burning speed or to the transition to detonation. The results are in satisfactory agreement with experimental observations.

  10. Magnetic field-aligned electric potentials in nonideal plasma flows

    Science.gov (United States)

    Schindler, K.; Hesse, M.; Birn, J.

    1991-01-01

    The electric field component parallel to the magnetic field arising from plasma flows which violate the frozen-in field condition of ideal magnetohydrodynamics is discussed. The quantity of interest is the potential U = integral E parallel ds where the integral is extended along field lines. It is shown that U can be directly related to magnetic field properties, expressed by Euler potentials, even when time-dependence is included. These results are applicable to earth's magnetosphere, to solar flares, to aligned-rotator models of compact objects, and to galactic rotation. On the basis of order-of-magnitude estimates, these results support the view that parallel electric fields associated with nonideal plasma flows might play an important role in cosmic particle acceleration.

  11. Analysis of a solar collector field water flow network

    Science.gov (United States)

    Rohde, J. E.; Knoll, R. H.

    1976-01-01

    A number of methods are presented for minimizing the water flow variation in the solar collector field for the Solar Building Test Facility at the Langley Research Center. The solar collector field investigated consisted of collector panels connected in parallel between inlet and exit collector manifolds to form 12 rows. The rows were in turn connected in parallel between the main inlet and exit field manifolds to complete the field. The various solutions considered included various size manifolds, manifold area change, different locations for the inlets and exits to the manifolds, and orifices or flow control valves. Calculations showed that flow variations of less than 5 percent were obtainable both inside a row between solar collector panels and between various rows.

  12. Flow Driven by an Archimedean Helical Permanent Magnetic Field. Part I: Flow Patterns and Their Transitions

    Science.gov (United States)

    Wang, Bo; Wang, Xiaodong; Etay, Jacqueline; Na, Xianzhao; Zhang, Xinde; Fautrelle, Yves

    2016-04-01

    In this study, an Archimedean helical permanent magnetic field was constructed and its driving effects on liquid metal were examined. A magnetic stirrer was constructed using a series of arc-like magnets. The helical distribution of its magnetic field, which was confirmed via Gauss probe measurements and numerical simulations, can be considered a combination of rotating and traveling magnetic fields. The characteristics of the flow patterns, particularly the transitions between the meridian secondary flow (two vortices) and the global axial flow (one vortex), driven by this magnetic field were quantitatively measured using ultrasonic Doppler velocimetry. The transient and modulated flow behaviors will be presented in a companion article. The D/ H dimension ratio was used to characterize the transitions of these two flow patterns. The results demonstrated that the flow patterns depend on not only the intrinsic structure of the magnetic field, e.g., the helix lead angle, but also the performance parameters, e.g., the dimensional ratio of the liquid bulk. The notable opposing roles of these two flow patterns in the improvement of macrosegregations when imposing such magnetic fields near the solidifying front were qualitatively addressed.

  13. Flow, current, and electric field in omnigenous stellarators

    Science.gov (United States)

    Landreman, Matt

    2011-10-01

    An omnigenous magnetic field is one in which all collisionless drift orbits are confined. Omnigenity is a less restrictive condition than quasisymmetry, for a magnetic field can be omnigenous without being quasisymmetric, whereas all quasisymmetric fields are omnigenous. Even though an omnigenous stellarator is generally fully three-dimensional, we have derived concise, explicit expressions for the bootstrap current, ion flow, and radial electric field in these devices in the long-mean-free-path regime, as well as expressions for the collisionality-independent Pfirsch-Schlüter current and flow in these devices. The radial electric field is determined in a manner that is consistent with intrinsic ambipolarity in the quasisymmetric limit. This electric field turns out to be independent of the details of the magnetic field geometry. The flow and current expressions involve only one more term than known expressions for quasisymmetric plasmas, but our results apply to a much larger class of stellarators. If the B contours of an omnigenous field close poloidally, the bootstrap current vanishes,. As a result, the drive for MHD instability is reduced, and the magnetic field optimization is less sensitive to the pressure profile. Stellarators that are optimized for maximal alpha-particle confinement will be approximately omnigenous, so our analytic results may give new insight into the physics of advanced stellarators. Supported by US DoE contract DE-FG02-91ER-54109.

  14. Internal Flow of a High Specific-Speed Diagonal-Flow Fan (Rotor Outlet Flow Fields with Rotating Stall

    Directory of Open Access Journals (Sweden)

    Norimasa Shiomi

    2003-01-01

    Full Text Available We carried out investigations for the purpose of clarifying the rotor outlet flow fields with rotating stall cell in a diagonal-flow fan. The test fan was a high–specific-speed (ns=1620 type of diagonal-flow fan that had 6 rotor blades and 11 stator blades. It has been shown that the number of the stall cell is 1, and its propagating speed is approximately 80% of its rotor speed, although little has been known about the behavior of the stall cell because a flow field with a rotating stall cell is essentially unsteady. In order to capture the behavior of the stall cell at the rotor outlet flow fields, hot-wire surveys were performed using a single-slant hotwire probe. The data obtained by these surveys were processed by means of a double phase-locked averaging technique, which enabled us to capture the flow field with the rotating stall cell in the reference coordinate system fixed to the rotor. As a result, time-dependent ensemble averages of the three-dimensional velocity components at the rotor outlet flow fields were obtained. The behavior of the stall cell was shown for each velocity component, and the flow patterns on the meridional planes were illustrated.

  15. An Experimental Study into Pylon, Wing, and Flap Installation Effects on Jet Noise Generated by Commercial Aircraft

    Science.gov (United States)

    Perrino, Michael

    A pylon bottom bifurcation and a wing with variable flaps were designed and built to attach to a scaled model of a coaxial exhaust nozzle system. The presence of the pylon bifurcation, wing, and flaps modify the characteristics of the exhaust flow forc- ing asymmetric flow and acoustics. A parametric study was carried out for assessing and relating the flow field characteristics to the near-field pressure and far-field acous- tic spectra. The flow field was investigated experimentally using both stream-wise and cross-stream PIV techniques where the near-field pressure and far-field acoustic spectra were measured using microphone arrays. Contour mapping of the flow field characteristics (e.g. mean velocity and turbulence kinetic energy levels) and near-field acoustics with and without installation effects were used to explain the changes in the far-field acoustics.

  16. Different elution modes and field programming in gravitational field-flow fractionation. III. Field programming by flow-rate gradient generated by a programmable pump

    Czech Academy of Sciences Publication Activity Database

    Plocková, Jana; Chmelík, Josef

    2001-01-01

    Roč. 918, č. 2 (2001), s. 361-370 ISSN 0021-9673 R&D Projects: GA AV ČR IAA4031805 Institutional research plan: CEZ:AV0Z4031919 Keywords : field-flow fractionation * field programming * flow-rate gradients Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 2.793, year: 2001

  17. Field-effect Flow Control in Polymer Microchannel Networks

    Science.gov (United States)

    Sniadecki, Nathan; Lee, Cheng S.; Beamesderfer, Mike; DeVoe, Don L.

    2003-01-01

    A new Bio-MEMS electroosmotic flow (EOF) modulator for plastic microchannel networks has been developed. The EOF modulator uses field-effect flow control (FEFC) to adjust the zeta potential at the Parylene C microchannel wall. By setting a differential EOF pumping rate in two of the three microchannels at a T-intersection with EOF modulators, the induced pressure at the intersection generated pumping in the third, field-free microchannel. The EOF modulators are able to change the magnitude and direction of the pressure pumping by inducing either a negative or positive pressure at the intersection. The flow velocity is tracked by neutralized fluorescent microbeads in the microchannels. The proof-of-concept of the EOF modulator described here may be applied to complex plastic ,microchannel networks where individual microchannel flow rates are addressable by localized induced-pressure pumping.

  18. Effects of Agricultural Management Policies on the Exposure of Black-Winged Stilts (Himantopus himantopus Chicks to Cholinesterase-Inhibiting Pesticides in Rice Fields.

    Directory of Open Access Journals (Sweden)

    Gregorio M Toral

    Full Text Available Levels of exposure to pesticides in rice fields can be significant depending on the environmental policies practiced. The aim of European Union integrated management policy is to reduce pesticide use and impact on environment. Rice fields provide an alternative breeding habitat for many waterbirds that are exposed to the pesticides used and therefore can be valuable indicators of their risk for wildlife. To evaluate integrated management success we examined exposure of Black-winged Stilts (Himantopus himantopus to cholinesterase-inhibiting pesticides in rice fields under different types of management by measuring plasma cholinesterase activity. Cholinesterase activity was lower in birds sampled in (a 2008 after a period of intense pesticide application, than in (b 2005-2007 and 2011 in rice fields subject to integrated management in Doñana (SW Spain and (c in control natural wetlands in Spain and Morocco. During 2009 and 2010, cholinesterase activity was lower in rice fields in Doñana than in rice fields in Larache and Sidi Allal Tazi (NW Morocco. Our results suggest that integrated management successfully reduced the exposure of Black-winged Stilts to pesticides in most of the years. Care should be taken to implement mosquito and pest crop controls on time and with environmentally friendly products in order to reduce its impact on wildlife.

  19. Flow field measurements in the cell culture unit

    Science.gov (United States)

    Walker, Stephen; Wilder, Mike; Dimanlig, Arsenio; Jagger, Justin; Searby, Nancy

    2002-01-01

    The cell culture unit (CCU) is being designed to support cell growth for long-duration life science experiments on the International Space Station (ISS). The CCU is a perfused loop system that provides a fluid environment for controlled cell growth experiments within cell specimen chambers (CSCs), and is intended to accommodate diverse cell specimen types. Many of the functional requirements depend on the fluid flow field within the CSC (e.g., feeding and gas management). A design goal of the CCU is to match, within experimental limits, all environmental conditions, other than the effects of gravity on the cells, whether the hardware is in microgravity ( micro g), normal Earth gravity, or up to 2g on the ISS centrifuge. In order to achieve this goal, two steps are being taken. The first step is to characterize the environmental conditions of current 1g cell biology experiments being performed in laboratories using ground-based hardware. The second step is to ensure that the design of the CCU allows the fluid flow conditions found in 1g to be replicated from microgravity up to 2g. The techniques that are being used to take these steps include flow visualization, particle image velocimetry (PIV), and computational fluid dynamics (CFD). Flow visualization using the injection of dye has been used to gain a global perspective of the characteristics of the CSC flow field. To characterize laboratory cell culture conditions, PIV is being used to determine the flow field parameters of cell suspension cultures grown in Erlenmeyer flasks on orbital shakers. These measured parameters will be compared to PIV measurements in the CSCs to ensure that the flow field that cells encounter in CSCs is within the bounds determined for typical laboratory experiments. Using CFD, a detailed simulation is being developed to predict the flow field within the CSC for a wide variety of flow conditions, including microgravity environments. Results from all these measurements and analyses of the

  20. Complex analysis with applications to flows and fields

    CERN Document Server

    Braga da Costa Campos, Luis Manuel

    2012-01-01

    Complex Analysis with Applications to Flows and Fields presents the theory of functions of a complex variable, from the complex plane to the calculus of residues to power series to conformal mapping. The book explores numerous physical and engineering applications concerning potential flows, the gravity field, electro- and magnetostatics, steady heat conduction, and other problems. It provides the mathematical results to sufficiently justify the solution of these problems, eliminating the need to consult external references.The book is conveniently divided into four parts. In each part, the ma

  1. Numerical simulation of transverse jet flow field under supersonic inflow

    Directory of Open Access Journals (Sweden)

    Qian Li

    2017-01-01

    Full Text Available Transverse jet flow field under supersonic inflow is simulated numerically for studying the characteristic of fuel transverse jet and fuel mixing in scramjet combustion chamber. Comparison is performed between simulated results and the results of references and experiments. Results indicate that the CFD code in this paper is applicable for simulation of transverse jut flow field under supersonic inflow, but in order to providing more effective numerical predictive method, CFD code should be modified through increasing mesh density and adding LES module.

  2. Flow field bipolar plates in a proton exchange membrane fuel cell: Analysis & modeling

    International Nuclear Information System (INIS)

    Kahraman, Huseyin; Orhan, Mehmet F.

    2017-01-01

    Highlights: • Covers a comprehensive review of available flow field channel configurations. • Examines the main design considerations and limitations for a flow field network. • Explores the common materials and material properties used for flow field plates. • Presents a case study of step-by-step modeling for an optimum flow field design. - Abstract: This study investigates flow fields and flow field plates (bipolar plates) in proton exchange membrane fuel cells. In this regard, the main design considerations and limitations for a flow field network have been examined, along with a comprehensive review of currently available flow field channel configurations. Also, the common materials and material properties used for flow field plates have been explored. Furthermore, a case study of step-by-step modeling for an optimum flow field design has been presented in-details. Finally, a parametric study has been conducted with respect to many design and performance parameters in a flow field plate.

  3. A Study of Coaxial Rotor Performance and Flow Field Characteristics

    Science.gov (United States)

    2016-01-22

    1950 (Ref. 8) in the full-scale wind tunnel at NASA Langley Research Center. The coaxial rotor consisted of two 20-in diameter rotors , with two blades...C., “ Wind - tunnel studies of the perfor- mance of multirotor configurations,” NACA TN- 3236, Au- gust 1954. 17Kim, H. W. and Brown, R. E...A Study of Coaxial Rotor Performance and Flow Field Characteristics Natasha L. Barbely Aerospace Engineer NASA Ames Research Center Moffett Field

  4. WINGS Data Release

    DEFF Research Database (Denmark)

    Moretti, A.; Poggianti, B. M.; Fasano, G.

    2014-01-01

    Context. To effectively investigate galaxy formation and evolution, it is of paramount importance to exploit homogeneous data for large samples of galaxies in different environments. Aims. The WIde-field Nearby Galaxy-cluster Survey (WINGS) project aim is to evaluate physical properties of galaxies...... in a complete sample of low redshift clusters to be used as reference sample for evolutionary studies. The WINGS survey is still ongoing and the original dataset will be enlarged with new observations. This paper presents the entire collection of WINGS measurements obtained so far. Methods. We decided to make......, and on the cluster redshift, reaching on average 90% at V ≲ 21.7. Near-infrared photometric catalogs for 26 (in K) and 19 (in J) clusters are part of the database and the number of sources is 962 344 in K and 628 813 in J. Here again the completeness depends on the data quality, but it is on average higher than 90...

  5. DEM simulation of granular flows in a centrifugal acceleration field

    Science.gov (United States)

    Cabrera, Miguel Angel; Peng, Chong; Wu, Wei

    2017-04-01

    The main purpose of mass-flow experimental models is abstracting distinctive features of natural granular flows, and allow its systematic study in the laboratory. In this process, particle size, space, time, and stress scales must be considered for the proper representation of specific phenomena [5]. One of the most challenging tasks in small scale models, is matching the range of stresses and strains among the particle and fluid media observed in a field event. Centrifuge modelling offers an alternative to upscale all gravity-driven processes, and it has been recently employed in the simulation of granular flows [1, 2, 3, 6, 7]. Centrifuge scaling principles are presented in Ref. [4], collecting a wide spectrum of static and dynamic models. However, for the case of kinematic processes, the non-uniformity of the centrifugal acceleration field plays a major role (i.e., Coriolis and inertial effects). In this work, we discuss a general formulation for the centrifugal acceleration field, implemented in a discrete element model framework (DEM), and validated with centrifuge experimental results. Conventional DEM simulations relate the volumetric forces as a function of the gravitational force Gp = mpg. However, in the local coordinate system of a rotating centrifuge model, the cylindrical centrifugal acceleration field needs to be included. In this rotating system, the centrifugal acceleration of a particle depends on the rotating speed of the centrifuge, as well as the position and speed of the particle in the rotating model. Therefore, we obtain the formulation of centrifugal acceleration field by coordinate transformation. The numerical model is validated with a series of centrifuge experiments of monodispersed glass beads, flowing down an inclined plane at different acceleration levels and slope angles. Further discussion leads to the numerical parameterization necessary for simulating equivalent granular flows under an augmented acceleration field. The premise of

  6. Electrohydrodynamic flow caused by field-enhanced dissociation solely

    Science.gov (United States)

    Vasilkov, S. A.; Chirkov, V. A.; Stishkov, Yu. K.

    2017-06-01

    Electrohydrodynamic (EHD) flows emerge in dielectric liquids under the action of the Coulomb force and underlie energy-efficient techniques for heat and mass transfer. The key issue in the phenomena is the way how the net charge is created. One of the most promising, yet poorly studied charge formation mechanisms is the field-enhanced dissociation (or the Wien effect). So the paper studies an EHD flow caused solely by the effect by virtue of both experiment and computer simulation. To preclude the competing mechanism of charge formation—the injection—a new EHD system of a special design was examined. Its main feature is the use of solid insulation to create the region of the strong electric field far from the electrode metal surfaces. The experimental study used the particle image velocimetry technique to observe velocity distributions, whereas the computations were based on the complete set of electrohydrodynamic equations employing the commercial software package COMSOL Multiphysics. Spatial distributions of key quantities (including the ion concentrations, the total space charge density, and the velocity) and the acting forces were obtained in the computer simulation and were analyzed. The experimental flow structure was observed for a number of voltages up to 30 kV. The comparison of the numerical and experimental results yielded a good quantitative agreement for strong electric fields though some overshoot was observed for weak ones. The results allow concluding on the applicability of the Onsager theory of the field-enhanced dissociation in the context of EHD flows.

  7. Magnetic and velocity fields MHD flow of a stretched vertical ...

    African Journals Online (AJOL)

    Analytical solutions for heat and mass transfer by laminar flow of Newtonian, viscous, electrically conducting and heat generation/absorbing fluid on a continuously moving vertical permeable surface with buoyancy in the presence of a magnetic field and a first order chemical reaction are reported. The solutions for magnetic ...

  8. Factors affecting particle retention in thermal field-flow fractionation

    African Journals Online (AJOL)

    ABSTRACT. In this paper, we report a range of factors which affect the retention of colloidal particles in thermal field-flow fractionation (ThFFF). These results are observed among different sizes of polystyrene (PS) latex particles suspended in both aqueous and nonaqueous liquid carriers and very low density lipoproteins in ...

  9. Estimation of Dense Image Flow Fields in Fluids

    DEFF Research Database (Denmark)

    Larsen, Rasmus; Conradsen, Knut; Ersbøll, Bjarne Kjær

    1998-01-01

    of the local energy distribution, which is sampled using a set of 3-D spatio-temporal filters. The estimated local energy distribution also allows us to compute a confidence measure of the estimated local normal flow. The algorithm furthermore utilises Markovian random fields in order to integrate the local...

  10. Estimation of Dense Image Flow Fields in Fluids

    DEFF Research Database (Denmark)

    Larsen, Rasmus; Conradsen, Knut; Ersbøll, Bjarne Kjær

    of the local energy distribution, which is sampled using a set of 3-D spatio-temporal filters. The estimated local energy distribution also allows us to compute a certainty measure of the estimated local flow. The algorithm furhtermore utilizes Markovian random fields in order to incorporate smoothness across...

  11. factors affecting particle retention in thermal field-flow fractionation

    African Journals Online (AJOL)

    In this paper, we report a range of factors which affect the retention of colloidal particles in thermal field-flow fractionation (ThFFF). These results are observed among different sizes of polystyrene (PS) latex particles suspended in both aqueous and nonaqueous liquid carriers and very low density lipoproteins in a phosphate ...

  12. Field research program for unsaturated flow and transport experimentation

    International Nuclear Information System (INIS)

    Tidwell, V.C.; Rautman, C.A.; Glass, R.J.

    1992-01-01

    As part of the Yucca Mountain Site Characterization Project, a field research program has been developed to refine and validate models for flow and transport through unsaturated fractured rock. Validation of these models within the range of their application for performance assessment requires a more sophisticated understanding of the processes that govern flow and transport within fractured porous media than currently exists. In particular, our research is prioritized according to understanding and modeling processes that, if not accurately incorporated into performance assessment models, would adversely impact the project's ability to evaluate repository performance. For this reason, we have oriented our field program toward enhancing our understanding of scaling processes as they relate to effective media property modeling, as well as to the conceptual modeling of complex flow and transport phenomena

  13. Flow field design for high-pressure PEM electrolysis cells

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Kær, Søren Knudsen

    -water distributes. Water not only serves a reactant, it also aids in cooling due to its high specific heat capacity. The movement of liquid water at the anode is difficult to model, since it is highly coupled to the formation of gas bubbles. To capture the complex two-phase flow behaviour that takes place within...... micro-channels and porous media, our research group has developed an Euler-Euler model in the computational fluid dynamics modelling framework of ANSYS CFX. In addition to two-phase flow, the model accounts for turbulence, species transport in the gas phase, heat transport in all three phases (i.......e. solid, gas and liquid), as well as charge transport of electrons and ions. Our recent improvements have focused on the models ability to account for phase change and electrochemistry as well as the modelling of two-phase flow regimes. For comparison, an interdigitated and parallel channel flow field...

  14. Mathematical Modeling of Electrolyte Flow Dynamic Patterns and Volumetric Flow Penetrations in the Flow Channel over Porous Electrode Layered System in Vanadium Flow Battery with Serpentine Flow Field Design

    OpenAIRE

    Ke, Xinyou; Prahl, Joseph M.; Alexander, J. Iwan D.; Savinell, Robert F.

    2016-01-01

    In this work, a two-dimensional mathematical model is developed to study the flow patterns and volumetric flow penetrations in the flow channel over the porous electrode layered system in vanadium flow battery with serpentine flow field design. The flow distributions at the interface between the flow channel and porous electrode are examined. It is found that the non-linear pressure distributions can distinguish the interface flow distributions under the ideal plug flow and ideal parabolic fl...

  15. Using optic flow in the far peripheral field.

    Science.gov (United States)

    McManus, Meaghan; D'Amour, Sarah; Harris, Laurence R

    2017-07-01

    Self-motion information can be used to update spatial memory of location through an estimate of a change in position. Viewing optic flow alone can create Illusory self-motion or "vection." Early studies suggested that peripheral vision is more effective than central vision in evoking vection, but controlling for retinal area and perceived distance suggests that all retinal areas may be equally effective. However, the contributions of the far periphery, beyond 90°, have been largely neglected. Using a large-field Edgeless Graphics Geometry display (EGG, Christie, Canada, field of view ±112°) and systematically blocking central (±20° to ±90°) or peripheral (viewing through tunnels ±20° to ±40°) parts of the field, we compared the effectiveness of different retinal regions at evoking forwards linear vection. Fifteen participants indicated when they had reached the position of a previously presented target after visually simulating motion down a simulated corridor. The amount of simulated travel needed to match a given target distance was modelled with a leaky spatial integrator model to estimate gains (perceived/actual distance) and a spatial decay factor. When optic flow was presented only in the far periphery (beyond 90°) gains were significantly higher than for the same motion presented full field or in only the central field, resulting in accurate performance in the range of speeds associated with normal walking. The increased effectiveness of optic flow in the peripheral field alone compared to full-field motion is discussed in terms of emerging neurophysiological studies that suggest brain areas dedicated to processing information from the far peripheral field.

  16. Effects of wing locations on wing rock induced by forebody vortices

    Directory of Open Access Journals (Sweden)

    Ma Baofeng

    2016-10-01

    Full Text Available Previous studies have shown that asymmetric vortex wakes over slender bodies exhibit a multi-vortex structure with an alternate arrangement along a body axis at high angle of attack. In this investigation, the effects of wing locations along a body axis on wing rock induced by forebody vortices was studied experimentally at a subcritical Reynolds number based on a body diameter. An artificial perturbation was added onto the nose tip to fix the orientations of forebody vortices. Particle image velocimetry was used to identify flow patterns of forebody vortices in static situations, and time histories of wing rock were obtained using a free-to-roll rig. The results show that the wing locations can affect significantly the motion patterns of wing rock owing to the variation of multi-vortex patterns of forebody vortices. As the wing locations make the forebody vortices a two-vortex pattern, the wing body exhibits regularly divergence and fixed-point motion with azimuthal variations of the tip perturbation. If a three-vortex pattern exists over the wing, however, the wing-rock patterns depend on the impact of the highest vortex and newborn vortex. As the three vortices together influence the wing flow, wing-rock patterns exhibit regularly fixed-points and limit-cycled oscillations. With the wing moving backwards, the newborn vortex becomes stronger, and wing-rock patterns become fixed-points, chaotic oscillations, and limit-cycled oscillations. With further backward movement of wings, the vortices are far away from the upper surface of wings, and the motions exhibit divergence, limit-cycled oscillations and fixed-points. For the rearmost location of the wing, the wing body exhibits stochastic oscillations and fixed-points.

  17. Transient simulation in interior flow field of lobe pump

    International Nuclear Information System (INIS)

    Li, Y B; Sang, X H; Shen, H; Jia, K; Meng, Q W

    2013-01-01

    The subject of this paper is mainly focused on the development and control of the double folium and trifolium lobe pump profiles by using the principle of involute engagement and use CAD to get an accurate involute profile. We use the standard k-ε turbulence model and PISO algorithm based on CFD software FLUENT. The dynamic mesh and UDF technology is introduced to simulate the interior flow field inside a lobe pump, and the variation of interior flow field under the condition of the lobe rotating is analyzed. We also analyse the influence produced by the difference in lobes, and then reveal which lobe is best. The results show that dynamic variation of the interior flow field is easily obtained by dynamic mesh technology and the distribution of its pressure and velocity. Because of the small gaps existing between the rotors and pump case, the higher pressure area will flow into the lower area though the small gaps which cause the working area keep with higher pressure all the time. Both of the double folium and trifolium are existing the vortex during the rotting time and its position, size and shape changes all the time. The vortexes even disappear in a circle period and there are more vortexes in double folium lobe pump. The velocity and pressure pulsation of trifolium pump are lower than that of the double folium

  18. Path planning in uncertain flow fields using ensemble method

    KAUST Repository

    Wang, Tong

    2016-08-20

    An ensemble-based approach is developed to conduct optimal path planning in unsteady ocean currents under uncertainty. We focus our attention on two-dimensional steady and unsteady uncertain flows, and adopt a sampling methodology that is well suited to operational forecasts, where an ensemble of deterministic predictions is used to model and quantify uncertainty. In an operational setting, much about dynamics, topography, and forcing of the ocean environment is uncertain. To address this uncertainty, the flow field is parametrized using a finite number of independent canonical random variables with known densities, and the ensemble is generated by sampling these variables. For each of the resulting realizations of the uncertain current field, we predict the path that minimizes the travel time by solving a boundary value problem (BVP), based on the Pontryagin maximum principle. A family of backward-in-time trajectories starting at the end position is used to generate suitable initial values for the BVP solver. This allows us to examine and analyze the performance of the sampling strategy and to develop insight into extensions dealing with general circulation ocean models. In particular, the ensemble method enables us to perform a statistical analysis of travel times and consequently develop a path planning approach that accounts for these statistics. The proposed methodology is tested for a number of scenarios. We first validate our algorithms by reproducing simple canonical solutions, and then demonstrate our approach in more complex flow fields, including idealized, steady and unsteady double-gyre flows.

  19. Laboratory Observation of Magnetic Field Growth Driven by Shear Flow

    Science.gov (United States)

    Intrator, Thomas; Dorf, L.; Sun, X.; Sears, J.; Weber, T.; Feng, Y.

    2013-04-01

    We have measured in the laboratory profiles of magnetic flux ropes, that include ion flow, magnetic field, current density, and plasma pressure. The electron flows v_e can therefore be inferred, and we use this information to evaluate the Hall J × B term in a two fluid magnetohydrodynamic Ohm’s Law. Mutually attracted and compressed flux ropes break the cylindrical symmetry. This simple and coherent example of shear flow supports magnetic field growth corresponding to non vanishing curl × v_e × B. In the absence of magnetic reconnection we measure and predict a quadrupole out of plane magnetic field δBz, even though this has historically been invoked to be the signature of Hall magnetic reconnection. This provides a natural and general mechanism for large scale sheared flows to acquire smaller scale magnetic features, disordered structure, and possibly turbulence. *Supported by DOE Office of Fusion Energy Sciences under LANS contract DE-AC52-06NA25369, NASA Geospace NNHIOA044I, Basic

  20. Asymmetrical flow field-flow fractionation of white wine chromophoric colloidal matter.

    Science.gov (United States)

    Coelho, Christian; Parot, Jérémie; Gonsior, Michael; Nikolantonaki, Maria; Schmitt-Kopplin, Philippe; Parlanti, Edith; Gougeon, Régis D

    2017-04-01

    Two analytical separation methods-size-exclusion chromatography and asymmetrical flow field-flow fractionation-were implemented to evaluate the integrity of the colloidal composition of Chardonnay white wine and the impact of pressing and fermentations on the final macromolecular composition. Wine chromophoric colloidal matter, representing UV-visible-absorbing wine macromolecules, was evaluated by optical and structural measurements combined with the description of elution profiles obtained by both separative techniques. The objective of this study was to apply these two types of fractionation on a typical Chardonnay white wine produced in Burgundy and to evaluate how each of them impacted the determination of the macromolecular chromophoric content of wine. UV-visible and fluorescence measurements of collected fractions were successfully applied. An additional proteomic study revealed that grape and microorganism proteins largely impacted the composition of chromophoric colloidal matter of Chardonnay wines. Asymmetrical flow field-flow fractionation appeared to be more reliable and less invasive with respect to the native chemical environment of chromophoric wine macromolecules, and hence is recommended as a tool to fractionate chromophoric colloidal matter in white wines. Graphical Abstract An innovative macromolecular separation method based on Asymmetrical Flow Field-Flow Fractionation was developed to better control colloidal dynamics across Chardonnay white winemaking.

  1. Effect of torsional stiffness and inertia on the dynamics of low aspect ratio flapping wings.

    Science.gov (United States)

    Xiao, Qing; Hu, Jianxin; Liu, Hao

    2014-03-01

    Micro air vehicle-motivated aerodynamics in biological flight has been an important subject in the past decade. Inspired by the novel flapping wing mechanisms in insects, birds and bats, we have carried out a numerical study systematically investigating a three-dimensional flapping rigid wing with passively actuated lateral and rotational motion. Distinguishing it from the limited existing studies, this work performs a systematic examination on the effects of wing aspect ratio (AR = 1.0 to infinity), inertia (density ratio σ = 4-32), torsional stiffness (frequency ratio F = 1.5-10 and infinity) and pivot point (from chord-center to leading edge) on the dynamics response of a low AR rectangular wing under an initial zero speed flow field condition. The simulation results show that the symmetry breakdown of the flapping wing results in a forward/backward motion with a rotational pitching. When the wing reaches its stable periodic state, the induced pitching frequency is identical to its forced flapping frequency. However, depending on various kinematic and dynamic system parameters, (i.e. flapping frequency, density ratio and pitching axis), the lateral induced velocity shows a number of different oscillating frequencies. Furthermore, compared with a one degree of freedom (DoF) wing in the lateral direction only, the propulsion performance of such a two DoF wing relies very much on the magnitude of torsional stiffness adding on the pivot point, as well as its pitching axis. In all cases examined here, thrust force and moment generated by a long span wing is larger than that of a short wing, which is remarkably linked to the strong reverse von Kármán vortex street formed in the wake of a wing.

  2. Design studies of Laminar Flow Control (LFC) wing concepts using superplastics forming and diffusion bonding (SPF/DB)

    Science.gov (United States)

    Wilson, V. E.

    1980-01-01

    Alternate concepts and design approaches were developed for suction panels and techniques were defined for integrating these panel designs into a complete LFC 200R wing. The design concepts and approaches were analyzed to assure that they would meet the strength, stability, and internal volume requirements. Cost and weight comparisions of the concepts were also made. Problems of integrating the concepts into a complete aircraft system were addressed. Methods for making splices both chordwise and spanwise, fuel light joints, and internal duct installations were developed. Manufacturing problems such as slot aligment, tapered slot spacing, production methods, and repair techniques were addressed. An assessment of the program was used to developed recommendations for additional research in the development of SPF/DB for LFC structure.

  3. A study of supersonic mixing flow field with ramp injector

    Science.gov (United States)

    Yamane, Yoshiyuki; Sawaguchi, Seiichi; Ando, Yasunori; Aso, Shigeru; Fukuda, Masahiro

    1994-06-01

    The purposes of the present paper are to investigate the structure of supersonic mixing flow field in ram/scramjet combustor and to develop the CFD code which will be used for the design of the combustor. One type of parallel injection method with ramp injector has been studied numerically and experimentally. The patterns of shock waves obtained by numerical simulations agreed with experimental results in schlieren photograph. Comparisons of static pressure distributions on the wall surface showed good agreement qualitatively. Numerical results captured the structures of flow field clearly, which were generating process of a pair of streamwise vortices and vortical roll-up of the jet. Oblique shocks made injectant gas lift off from wall surface, as found in calculations and experiments. According to these results, it could be said that the CFD code used in this study was useful for investigation of fuel-air mixing in supersonic flow field with parallel injection. From the numerical results, it was confirmed that the streamwise vortices generated by ramp injector and interaction between mixing field and oblique shocks were key factors for enhancement of fuel-air mixing in ram/scramjet combustor.

  4. Field measurement of basal forces generated by erosive debris flows

    Science.gov (United States)

    McCoy, S.W.; Tucker, G.E.; Kean, J.W.; Coe, J.A.

    2013-01-01

    It has been proposed that debris flows cut bedrock valleys in steeplands worldwide, but field measurements needed to constrain mechanistic models of this process remain sparse due to the difficulty of instrumenting natural flows. Here we present and analyze measurements made using an automated sensor network, erosion bolts, and a 15.24 cm by 15.24 cm force plate installed in the bedrock channel floor of a steep catchment. These measurements allow us to quantify the distribution of basal forces from natural debris‒flow events that incised bedrock. Over the 4 year monitoring period, 11 debris‒flow events scoured the bedrock channel floor. No clear water flows were observed. Measurements of erosion bolts at the beginning and end of the study indicated that the bedrock channel floor was lowered by 36 to 64 mm. The basal force during these erosive debris‒flow events had a large‒magnitude (up to 21 kN, which was approximately 50 times larger than the concurrent time‒averaged mean force), high‒frequency (greater than 1 Hz) fluctuating component. We interpret these fluctuations as flow particles impacting the bed. The resulting variability in force magnitude increased linearly with the time‒averaged mean basal force. Probability density functions of basal normal forces were consistent with a generalized Pareto distribution, rather than the exponential distribution that is commonly found in experimental and simulated monodispersed granular flows and which has a lower probability of large forces. When the bed sediment thickness covering the force plate was greater than ~ 20 times the median bed sediment grain size, no significant fluctuations about the time‒averaged mean force were measured, indicating that a thin layer of sediment (~ 5 cm in the monitored cases) can effectively shield the subjacent bed from erosive impacts. Coarse‒grained granular surges and water‒rich, intersurge flow had very similar basal force distributions despite

  5. The Flow Field on Hydrofoils with Leading Edge Protuberances

    Science.gov (United States)

    Custodio, Derrick; Henoch, Charles; Johari, Hamid

    2009-11-01

    The exceptional mobility of the humpback whale has been linked to the use of its unique pectoral flippers. Biologists speculate that the flippers leading edge protuberances are a form of passive flow control. Force measurements on 2D hydrofoils with spanwise uniform leading edge protuberances, resembling those seen on the humpback whale flipper, were taken in a water tunnel and have revealed performance modifications when compared to a baseline NACA 63(4)-021 hydrofoil model. Qualitative flow visualization techniques and Particle Image Velocimetry (PIV) flow field measurements on the modified hydrofoils have shown that streamwise vortices originating from the shoulders of the protuberances are the likely cause of performance changes. Varying levels of interaction among adjacent streamwise vortices have been observed as a function of angle of attack and chord location. The circulation of these vortices as a function of angle of attack and spatial location was measured and an analysis of the vortex interactions will be presented.

  6. The effect of aspect ratio on the leading-edge vortex over an insect-like flapping wing.

    Science.gov (United States)

    Phillips, Nathan; Knowles, Kevin; Bomphrey, Richard J

    2015-10-09

    Insect wing shapes are diverse and a renowned source of inspiration for the new generation of autonomous flapping vehicles, yet the aerodynamic consequences of varying geometry is not well understood. One of the most defining and aerodynamically significant measures of wing shape is the aspect ratio, defined as the ratio of wing length (R) to mean wing chord (c). We investigated the impact of aspect ratio, AR, on the induced flow field around a flapping wing using a robotic device. Rigid rectangular wings ranging from AR = 1.5 to 7.5 were flapped with insect-like kinematics in air with a constant Reynolds number (Re) of 1400, and a dimensionless stroke amplitude of 6.5c (number of chords traversed by the wingtip). Pseudo-volumetric, ensemble-averaged, flow fields around the wings were captured using particle image velocimetry at 11 instances throughout simulated downstrokes. Results confirmed the presence of a high-lift, separated flow field with a leading-edge vortex (LEV), and revealed that the conical, primary LEV grows in size and strength with increasing AR. In each case, the LEV had an arch-shaped axis with its outboard end originating from a focus-sink singularity on the wing surface near the tip. LEV detachment was observed for AR > 1.5 around mid-stroke at ~70% span, and initiated sooner over higher aspect ratio wings. At AR > 3 the larger, stronger vortex persisted under the wing surface well into the next half-stroke leading to a reduction in lift. Circulatory lift attributable to the LEV increased with AR up to AR = 6. Higher aspect ratios generated proportionally less lift distally because of LEV breakdown, and also less lift closer to the wing root due to the previous LEV's continuing presence under the wing. In nature, insect wings go no higher than AR ~ 5, likely in part due to architectural and physiological constraints but also because of the reducing aerodynamic benefits of high AR wings.

  7. Determining 3D flow fields via multi-camera light field imaging.

    Science.gov (United States)

    Truscott, Tadd T; Belden, Jesse; Nielson, Joseph R; Daily, David J; Thomson, Scott L

    2013-03-06

    In the field of fluid mechanics, the resolution of computational schemes has outpaced experimental methods and widened the gap between predicted and observed phenomena in fluid flows. Thus, a need exists for an accessible method capable of resolving three-dimensional (3D) data sets for a range of problems. We present a novel technique for performing quantitative 3D imaging of many types of flow fields. The 3D technique enables investigation of complicated velocity fields and bubbly flows. Measurements of these types present a variety of challenges to the instrument. For instance, optically dense bubbly multiphase flows cannot be readily imaged by traditional, non-invasive flow measurement techniques due to the bubbles occluding optical access to the interior regions of the volume of interest. By using Light Field Imaging we are able to reparameterize images captured by an array of cameras to reconstruct a 3D volumetric map for every time instance, despite partial occlusions in the volume. The technique makes use of an algorithm known as synthetic aperture (SA) refocusing, whereby a 3D focal stack is generated by combining images from several cameras post-capture (1). Light Field Imaging allows for the capture of angular as well as spatial information about the light rays, and hence enables 3D scene reconstruction. Quantitative information can then be extracted from the 3D reconstructions using a variety of processing algorithms. In particular, we have developed measurement methods based on Light Field Imaging for performing 3D particle image velocimetry (PIV), extracting bubbles in a 3D field and tracking the boundary of a flickering flame. We present the fundamentals of the Light Field Imaging methodology in the context of our setup for performing 3DPIV of the airflow passing over a set of synthetic vocal folds, and show representative results from application of the technique to a bubble-entraining plunging jet.

  8. Flow field investigation in a bulb turbine diffuser

    Science.gov (United States)

    Pereira, M.; Duquesne, P.; Aeschlimann, V.; Deschênes, C.

    2017-04-01

    An important drop in turbine performances has been measured in a bulb turbine model operated at overload. Previous investigations have correlated the performance drop with diffuser losses, and particularly to the flow separation zone at the diffuser wall. The flow has been investigated in the transition part of the diffuser using two LDV measurement sections. The transition part is a diffuser section that transforms from a circular to a rectangular section. The two measurement sections are at the inlet and outlet of the diffuser transition part. The turbine has been operated at three operating points, which are representative of different flow patterns at the diffuser exit at overload. In addition to the average velocity field, the analysis is conducted based on a backflow occurrence function and on the swirl level. Results reveal a counter-rotating zone in the diffuser, which intensifies with the guide vanes opening. The guide vanes opening induces a modification of the flow phenomena: from a central backflow recirculation zone at the lowest flowrate to a backflow zone induced by flow separation at the wall at the highest flowrate.

  9. Review Results on Wing-Body Interference

    Directory of Open Access Journals (Sweden)

    Frolov Vladimir

    2016-01-01

    Full Text Available The paper presents an overview of results for wing-body interference, obtained by the author for varied wing-body combinations. The lift-curve slopes of the wing-body combinations are considered. In this paper a discrete vortices method (DVM and 2D potential model for cross-flow around fuselage are used. The circular and elliptical cross-sections of the fuselage and flat wings of various forms are considered. Calculations showed that the value of the lift-curve slopes of the wing-body combinations may exceed the same value for an isolated wing. This result confirms an experimental data obtained by other authors earlier. Within a framework of the used mathematical models the investigations to optimize the wing-body combination were carried. The present results of the optimization problem for the wing-body combination allowed to select the optimal geometric characteristics for configuration to maximize the values of the lift-curve slopes of the wing-body combination. It was revealed that maximums of the lift-curve slopes for the optimal mid-wing configuration with elliptical cross-section body had a sufficiently large relative width of the body (more than 30% of the span wing.

  10. The morphology and evolution of the Stromboli 2002-2003 lava flow field--An example of a basaltic flow field emplaced on a steep slope

    Science.gov (United States)

    Lodato, Luigi; Harris, A.; Spampinato, L.; Calvari, Sonia; Dehn, J.; Patrick, M.

    2007-01-01

    The use of a hand-held thermal camera during the 2002–2003 Stromboli effusive eruption proved essential in tracking the development of flow field structures and in measuring related eruption parameters, such as the number of active vents and flow lengths. The steep underlying slope on which the flow field was emplaced resulted in a characteristic flow field morphology. This comprised a proximal shield, where flow stacking and inflation caused piling up of lava on the relatively flat ground of the vent zone, that fed a medial–distal lava flow field. This zone was characterized by the formation of lava tubes and tumuli forming a complex network of tumuli and flows linked by tubes. Most of the flow field was emplaced on extremely steep slopes and this had two effects. It caused flows to slide, as well as flow, and flow fronts to fail frequently, persistent flow front crumbling resulted in the production of an extensive debris field. Channel-fed flows were also characterized by development of excavated debris levees in this zone (Calvari et al. 2005). Collapse of lava flow fronts and inflation of the upper proximal lava shield made volume calculation very difficult. Comparison of the final field volume with that expecta by integrating the lava effusion rates through time suggests a loss of ~70% erupted lava by flow front crumbling and accumulation as debris flows below sea level. Derived relationships between effusion rate, flow length, and number of active vents showed systematic and correlated variations with time where spreading of volume between numerous flows caused an otherwise good correlation between effusion rate, flow length to break down. Observations collected during this eruption are useful in helping to understand lava flow processes on steep slopes, as well as in interpreting old lava–debris sequences found in other steep-sided volcanoes subject to effusive activity.

  11. Field-Flow Fractionation of Carbon Nanotubes and Related Materials

    Energy Technology Data Exchange (ETDEWEB)

    John P. Selegue

    2011-11-17

    During the grant period, we carried out FFF studies of carbonaceous soot, single-walled and multi-walled carbon nanotubes, carbon nano-onions and polyoxometallates. FFF alone does not provide enough information to fully characterize samples, so our suite of characterization techniques grew to include light scattering (especially Photon Correlation Spectroscopy), scanning and transmission electron microscopy, thermogravimetric analysis and spectroscopic methods. We developed convenient techniques to deposit and examine minute FFF fractions by electron microscopy. In collaboration with Arthur Cammers (University of Kentucky), we used Flow Field-Flow Fractionation (Fl-FFF) to monitor the solution-phase growth of keplerates, a class of polyoxometallate (POM) nanoparticles. We monitored the evolution of Mo-POM nanostructures over the course of weeks by by using flow field-flow fractionation and corroborated the nanoparticle structures by using transmission electron microscopy (TEM). Total molybdenum in the solution and precipitate phases was monitored by using inductively coupled plasma analyses, and total Mo-POM concentration by following the UV-visible spectra of the solution phase. We observe crystallization-driven formation of (Mo132) keplerate and solution phase-driven evolution of structurally related nanoscopic species (3-60 nm). FFF analyses of other classes of materials were less successful. Attempts to analyze platelets of layered materials, including exfoliated graphite (graphene) and TaS2 and MoS2, were disappointing. We were not able to optimize flow conditions for the layered materials. The metal sulfides react with the aqueous carrier liquid and settle out of suspension quickly because of their high density.

  12. Modeling field scale unsaturated flow and transport processes

    International Nuclear Information System (INIS)

    Gelhar, L.W.; Celia, M.A.; McLaughlin, D.

    1994-08-01

    The scales of concern in subsurface transport of contaminants from low-level radioactive waste disposal facilities are in the range of 1 to 1,000 m. Natural geologic materials generally show very substantial spatial variability in hydraulic properties over this range of scales. Such heterogeneity can significantly influence the migration of contaminants. It is also envisioned that complex earth structures will be constructed to isolate the waste and minimize infiltration of water into the facility. The flow of water and gases through such facilities must also be a concern. A stochastic theory describing unsaturated flow and contamination transport in naturally heterogeneous soils has been enhanced by adopting a more realistic characterization of soil variability. The enhanced theory is used to predict field-scale effective properties and variances of tension and moisture content. Applications illustrate the important effects of small-scale heterogeneity on large-scale anisotropy and hysteresis and demonstrate the feasibility of simulating two-dimensional flow systems at time and space scales of interest in radioactive waste disposal investigations. Numerical algorithms for predicting field scale unsaturated flow and contaminant transport have been improved by requiring them to respect fundamental physical principles such as mass conservation. These algorithms are able to provide realistic simulations of systems with very dry initial conditions and high degrees of heterogeneity. Numerical simulation of the movement of water and air in unsaturated soils has demonstrated the importance of air pathways for contaminant transport. The stochastic flow and transport theory has been used to develop a systematic approach to performance assessment and site characterization. Hypothesis-testing techniques have been used to determine whether model predictions are consistent with observed data

  13. Improved Flow-Field Structures for Direct Methanol Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Gurau, Bogdan [Nuvant Systems Inc., Crown Point, IN (United States)

    2013-05-31

    The direct methanol fuel cell (DMFC) is ideal if high energy-density liquid fuels are required. Liquid fuels have advantages over compressed hydrogen including higher energy density and ease of handling. Although state-of-the-art DMFCs exhibit manageable degradation rates, excessive fuel crossover diminishes system energy and power density. Although use of dilute methanol mitigates crossover, the concomitant lowering of the gross fuel energy density (GFED) demands a complex balance-of-plant (BOP) that includes higher flow rates, external exhaust recirculation, etc. An alternative approach is redesign of the fuel delivery system to accommodate concentrated methanol. NuVant Systems Inc. (NuVant) will maximize the GFED by design and assembly of a DMFC that uses near neat methanol. The approach is to tune the diffusion of highly concentrated methanol (to the anode catalytic layer) to the back-diffusion of water formed at the cathode (i.e. in situ generation of dilute methanol at the anode layer). Crossover will be minimized without compromising the GFED by innovative integration of the anode flow-field and the diffusion layer. The integrated flow-field-diffusion-layers (IFDLs) will widen the current and potential DMFC operating ranges and enable the use of cathodes optimized for hydrogen-air fuel cells.

  14. Evaluation of Aircraft Wing-Tip Vortex Using PIV

    Science.gov (United States)

    Alsayed, Omer A.; Asrar, Waqar; Omar, Ashraf A.

    2010-06-01

    The formation and development of a wing-tip vortex in a near and extended near filed were studied experimentally. Particle image velocimetry was used in a wind tunnel to measure the tip vortex velocity field and hence investigate the flow structure in a wake of aircraft half-wing model. The purpose of this investigation is to evaluate the main features of the lift generated vortices in order to find ways to alleviate hazardous wake vortex encounters for follower airplanes during start and approach such that the increase in airport capacity can be achieved. First the wake structure at successive downstream planes crosswise to the axis of the wake vortices was investigated by measuring parameters such as core radius, maximum tangential velocities, vorticities and circulation distributions. The effect of different angles of attack setting on vortex parameters was examined at one downstream location. In very early stages the vortex sheet evolution makes the tip vortex to move inward and to the suction side of the wing. While the core radius and circulation distributions hardly vary with the downstream distance, noticeable differences for the same vortex parameters at different angles of attack settings were observed. The center of the wing tip vortices scatter in a circle of radius nearly equal to 1% of the mean wing chord and wandering amplitudes shows no direct dependence on the vortex strength but linearly increase with the downstream distance.

  15. High resolution flow field prediction for tail rotor aeroacoustics

    Science.gov (United States)

    Quackenbush, Todd R.; Bliss, Donald B.

    The prediction of tail rotor noise due to the impingement of the main rotor wake poses a significant challenge to current analysis methods in rotorcraft aeroacoustics. This paper describes the development of a new treatment of the tail rotor aerodynamic environment that permits highly accurate resolution of the incident flow field with modest computational effort relative to alternative models. The new approach incorporates an advanced full-span free wake model of the main rotor in a scheme which reconstructs high-resolution flow solutions from preliminary, computationally inexpensive simulations with coarse resolution. The heart of the approach is a novel method for using local velocity correction terms to capture the steep velocity gradients characteristic of the vortex-dominated incident flow. Sample calculations have been undertaken to examine the principal types of interactions between the tail rotor and the main rotor wake and to examine the performance of the new method. The results of these sample problems confirm the success of this approach in capturing the high-resolution flows necessary for analysis of rotor-wake/rotor interactions with dramatically reduced computational cost. Computations of radiated sound are also carried out that explore the role of various portions of the main rotor wake in generating tail rotor noise.

  16. Flow rate estimation using acoustic field distortions caused by turbulent flows: time-reversal approach

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, A L; Perez, N; Adamowski, J C, E-mail: zimmer09@gmail.com [Department of Mechatronics and Mechanical Systems Engineering, University of Sao Paulo, Sao Paulo, SP, 05508-10 (Brazil)

    2011-05-01

    A new acoustic technique for flow rate estimation is proposed here. This technique is based on the traditional ultrasonic cross-correlation flow meter, but instead of using a continuous wave or pulse trains in each transmitter-receiver pair, the acoustic time-reversal technique is applied. The system relies on the principle that a turbulent flow with multiple vortices will cause random distortions in a given acoustic field; hence, analyzing this noise caused in the ultrasound signal by the turbulence over time allows a 'signature' or 'tag' of the flow to be defined. In other words, the vortices modify the frequency response function of the flowing system uniquely, since the distortion is assumed to be random. The use of the time-reversal procedure in the cross-correlation flow meter provides improvements in several aspects: it simplifies the signal processing needed after the reception of the signals, avoiding the use of a demodulator to obtain the signature of the vortex; the signal is focused at the position of the reception transducer and; the sensitivity is also increased because the wave travels twice in the acoustic channel. The method is theoretically discussed showing its limitations and improvements. Experimental results in a laboratory water tank are also presented.

  17. Magnetic field dynamos and magnetically triggered flow instabilities

    Science.gov (United States)

    Stefani, F.; Albrecht, T.; Arlt, R.; Christen, M.; Gailitis, A.; Gellert, M.; Giesecke, A.; Goepfert, O.; Herault, J.; Kirillov, O. N.; Mamatsashvili, G.; Priede, J.; Rüdiger, G.; Seilmayer, M.; Tilgner, A.; Vogt, T.

    2017-07-01

    The project A2 of the LIMTECH Alliance aimed at a better understanding of those magnetohydrodynamic instabilities that are relevant for the generation and the action of cosmic magnetic fields. These comprise the hydromagnetic dynamo effect and various magnetically triggered flow instabilities, such as the magnetorotational instability and the Tayler instability. The project was intended to support the experimental capabilities to become available in the framework of the DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN). An associated starting grant was focused on the dimensioning of a liquid metal experiment on the newly found magnetic destabilization of rotating flows with positive shear. In this survey paper, the main results of these two projects are summarized.

  18. Numerical simulation of aerodynamic characteristics of multi-element wing with variable flap

    Science.gov (United States)

    Lv, Hongyan; Zhang, Xinpeng; Kuang, Jianghong

    2017-10-01

    Based on the Reynolds averaged Navier-Stokes equation, the mesh generation technique and the geometric modeling method, the influence of the Spalart-Allmaras turbulence model on the aerodynamic characteristics is investigated. In order to study the typical configuration of aircraft, a similar DLR-F11 wing is selected. Firstly, the 3D model of wing is established, and the 3D model of plane flight, take-off and landing is established. The mesh structure of the flow field is constructed and the mesh is generated by mesh generation software. Secondly, by comparing the numerical simulation with the experimental data, the prediction of the aerodynamic characteristics of the multi section airfoil in takeoff and landing stage is validated. Finally, the two flap deflection angles of take-off and landing are calculated, which provide useful guidance for the aerodynamic characteristics of the wing and the flap angle design of the wing.

  19. Flow balancing orifice for ITER toroidal field coil

    Science.gov (United States)

    Litvinovich, A. V.; Y Rodin, I.; Kovalchuk, O. A.; Safonov, A. V.; Stepanov, D. B.; Guryeva, T. M.

    2017-12-01

    Flow balancing orifices (FBOs) are used in in International thermonuclear experimental reactor (ITER) Toroidal Field coil to uniform flow rate of cooling gas in the side double pancakes which have a different conductor length: 99 m and 305 m, respectively. FBOs consist of straight parts, elbows produced from a 316L stainless steel tube 21.34 x 2.11 mm and orifices made from a 316L stainless steel rod. Each of right and left FBOs contains 6 orifices, straight FBOs contain 4 and 6 orifices. Before manufacturing of qualification samples D.V. Efremov Institute of Electrophysical Apparatus (JSC NIIEFA) proposed to ITER a new approach to provide the seamless connection between a tube and a plate therefore the most critical weld between the orifice with 1 mm thickness and the tube removed from the FBOs final design. The proposed orifice diameter is three times less than the minimum requirement of the ISO 5167, therefore it was tasked to define accuracy of calculation flow characteristics at room temperature and compare with the experimental data. In 2015 the qualification samples of flow balancing orifices were produced and tested. The results of experimental data showed that the deviation of calculated data is less than 7%. Based on this result and other tests ITER approved the design of FBOs, which made it possible to start the serial production. In 2016 JSC NIIEFA delivered 50 FBOs to ITER, i.e. 24 left side, 24 right side and 2 straight FBOs. In order to define the quality of FBOs the test facility in JSC NIIEFA was prepared. The helium tightness test at 10-9 m3·Pa/s the pressure up to 3 MPa, flow rate measuring at the various pressure drops, the non-destructive tests of orifices and weld seams (ISO 5817, class B) were conducted. Other tests such as check dimensions and thermo cycling 300 - 80 - 300 K also were carried out for each FBO.

  20. Aerodynamic structures and processes in rotationally augmented flow fields

    DEFF Research Database (Denmark)

    Schreck, S.J.; Sørensen, Niels N.; Robinson, M.C.

    2007-01-01

    Rotational augmentation of horizontal axis wind turbine blade aerodynamics currently remains incompletely characterized and understood. To address this, the present study concurrently analysed experimental measurements and computational predictions, both of which were unique and of high quality...... to reliably identify and track pertinent features in the rotating blade boundary layer topology as they evolved in response to varying wind speed. Subsequently, boundary layer state was linked to above-surface flow field structure and used to deduce mechanisms; underlying augmented aerodynamic force...... production during rotating conditions. Copyright (C) 2007 John Wiley & Sons, Ltd....

  1. Modeling two-phase flow in three-dimensional complex flow-fields of proton exchange membrane fuel cells

    Science.gov (United States)

    Kim, Jinyong; Luo, Gang; Wang, Chao-Yang

    2017-10-01

    3D fine-mesh flow-fields recently developed by Toyota Mirai improved water management and mass transport in proton exchange membrane (PEM) fuel cell stacks, suggesting their potential value for robust and high-power PEM fuel cell stack performance. In such complex flow-fields, Forchheimer's inertial effect is dominant at high current density. In this work, a two-phase flow model of 3D complex flow-fields of PEMFCs is developed by accounting for Forchheimer's inertial effect, for the first time, to elucidate the underlying mechanism of liquid water behavior and mass transport inside 3D complex flow-fields and their adjacent gas diffusion layers (GDL). It is found that Forchheimer's inertial effect enhances liquid water removal from flow-fields and adds additional flow resistance around baffles, which improves interfacial liquid water and mass transport. As a result, substantial improvements in high current density cell performance and operational stability are expected in PEMFCs with 3D complex flow-fields, compared to PEMFCs with conventional flow-fields. Higher current density operation required to further reduce PEMFC stack cost per kW in the future will necessitate optimizing complex flow-field designs using the present model, in order to efficiently remove a large amount of product water and hence minimize the mass transport voltage loss.

  2. Velocity flow field and water level measurements in shoaling and breaking water waves

    CSIR Research Space (South Africa)

    Mukaro, R

    2010-01-01

    Full Text Available levels were measured using capacitive waves gauges, while the instantaneous velocity flow fields were measured using video techniques together with digital correlation techniques. The instantaneous velocity flow fields were further analyzed to yield...

  3. Effect of leading edge roundness on a delta wing in wing-rock motion

    Science.gov (United States)

    Ng, T. Terry; Malcolm, Gerald N.

    1990-01-01

    The effect of wing leading-edge roundness on wing rock was investigated using flow visualization in a water tunnel. Eighty degree delta wing models were tested on free-to-roll and forced oscillation rigs. The onset of wing rock was delayed by increasing the roundness of the leading edges. The wing rock amplitude and frequency results suggested that damping was increased at lower angles of attack but reduced at higher angles of attack. Vortex lift-off and vortex breakdown, especially during dynamic situations, were strongly affected by the leading edge roundness. Different forms of wing rock motion could be sustained by combinations of vortex breakdown and vortex lift-off. Behaviors of the wing and vortex motions were explained by the influence of leading edge roundness on the separation location, vortex trajectory, and vortex breakdown.

  4. Role of wing morphing in thrust generation

    Directory of Open Access Journals (Sweden)

    Mehdi Ghommem

    2014-01-01

    Full Text Available In this paper, we investigate the role of morphing on flight dynamics of two birds by simulating the flow over rigid and morphing wings that have the characteristics of two different birds, namely the Giant Petrel and Dove Prion. The simulation of a flapping rigid wing shows that the root of the wing should be placed at a specific angle of attack in order to generate enough lift to balance the weight of the bird. However, in this case the generated thrust is either very small, or even negative, depending on the wing shape. Further, results show that morphing of the wing enables a significant increase in the thrust and propulsive efficiency. This indicates that the birds actually utilize some sort of active wing twisting and bending to produce enough thrust. This study should facilitate better guidance for the design of flapping air vehicles.

  5. Aerodynamic effects of flexibility in flapping wings

    Science.gov (United States)

    Zhao, Liang; Huang, Qingfeng; Deng, Xinyan; Sane, Sanjay P.

    2010-01-01

    Recent work on the aerodynamics of flapping flight reveals fundamental differences in the mechanisms of aerodynamic force generation between fixed and flapping wings. When fixed wings translate at high angles of attack, they periodically generate and shed leading and trailing edge vortices as reflected in their fluctuating aerodynamic force traces and associated flow visualization. In contrast, wings flapping at high angles of attack generate stable leading edge vorticity, which persists throughout the duration of the stroke and enhances mean aerodynamic forces. Here, we show that aerodynamic forces can be controlled by altering the trailing edge flexibility of a flapping wing. We used a dynamically scaled mechanical model of flapping flight (Re ≈ 2000) to measure the aerodynamic forces on flapping wings of variable flexural stiffness (EI). For low to medium angles of attack, as flexibility of the wing increases, its ability to generate aerodynamic forces decreases monotonically but its lift-to-drag ratios remain approximately constant. The instantaneous force traces reveal no major differences in the underlying modes of force generation for flexible and rigid wings, but the magnitude of force, the angle of net force vector and centre of pressure all vary systematically with wing flexibility. Even a rudimentary framework of wing veins is sufficient to restore the ability of flexible wings to generate forces at near-rigid values. Thus, the magnitude of force generation can be controlled by modulating the trailing edge flexibility and thereby controlling the magnitude of the leading edge vorticity. To characterize this, we have generated a detailed database of aerodynamic forces as a function of several variables including material properties, kinematics, aerodynamic forces and centre of pressure, which can also be used to help validate computational models of aeroelastic flapping wings. These experiments will also be useful for wing design for small robotic

  6. Aerodynamic effects of flexibility in flapping wings.

    Science.gov (United States)

    Zhao, Liang; Huang, Qingfeng; Deng, Xinyan; Sane, Sanjay P

    2010-03-06

    Recent work on the aerodynamics of flapping flight reveals fundamental differences in the mechanisms of aerodynamic force generation between fixed and flapping wings. When fixed wings translate at high angles of attack, they periodically generate and shed leading and trailing edge vortices as reflected in their fluctuating aerodynamic force traces and associated flow visualization. In contrast, wings flapping at high angles of attack generate stable leading edge vorticity, which persists throughout the duration of the stroke and enhances mean aerodynamic forces. Here, we show that aerodynamic forces can be controlled by altering the trailing edge flexibility of a flapping wing. We used a dynamically scaled mechanical model of flapping flight (Re approximately 2000) to measure the aerodynamic forces on flapping wings of variable flexural stiffness (EI). For low to medium angles of attack, as flexibility of the wing increases, its ability to generate aerodynamic forces decreases monotonically but its lift-to-drag ratios remain approximately constant. The instantaneous force traces reveal no major differences in the underlying modes of force generation for flexible and rigid wings, but the magnitude of force, the angle of net force vector and centre of pressure all vary systematically with wing flexibility. Even a rudimentary framework of wing veins is sufficient to restore the ability of flexible wings to generate forces at near-rigid values. Thus, the magnitude of force generation can be controlled by modulating the trailing edge flexibility and thereby controlling the magnitude of the leading edge vorticity. To characterize this, we have generated a detailed database of aerodynamic forces as a function of several variables including material properties, kinematics, aerodynamic forces and centre of pressure, which can also be used to help validate computational models of aeroelastic flapping wings. These experiments will also be useful for wing design for small

  7. Field-Scale Measurements for Separation of Catchment Discharge into Flow Route Contributions

    NARCIS (Netherlands)

    Velde, van der Y.; Rozemeijer, J.; Rooij, de G.H.; Geer, van F.C.; Broers, H.P.

    2010-01-01

    Agricultural pollutants in catchments are transported toward the discharging stream through various flow routes such as tube drain flow, groundwater flow, interflow, and overland flow. Direct measurements of flow route contributions are difficult and often impossible. We developed a field-scale

  8. How Do Wings Generate Lift?

    Indian Academy of Sciences (India)

    Newton's second law of motion. Hence if a wing can generate lift equal to its weight (total weight of the vehicle) it can balance the gravitational pull and can maintain level flight. The equations for fluid flow that are equivalent to the second law are the well- known Navier–Stokes (N–S) equations [1]. These equations have.

  9. Turbulent flow field structure of initially asymmetric jets

    International Nuclear Information System (INIS)

    Kim, Kyung Hoon; Kim, Bong Whan; Kim, Suk Woo

    2000-01-01

    The near field structure of round turbulent jets with initially asymmetric velocity distributions is investigated experimentally. Experiments are carried out using a constant temperature hot-wire anemomentry system to measure streamwise velocity in the jets. The measurements are undertaken across the jet at various streamwise stations in a range starting from the jet exit plane and up to a downstream location of twelve diameters. The experimental results include the distributions of mean and instantaneous velocities, vorticity field, turbulence intensity, and the Reynolds shear stresses. The asymmetry of the jet exit plane was obtained by using circular cross-section pipes with a bend upstream of the exit. Three pipes used here include a straight pipe, and 90 and 160 degree-bend pipes. Therefore, at the upstream of the pipe exit, secondary flow through the bend and mean streamwise velocity distribution could be controlled by changing the curvature of pipes. The jets into the atmosphere have two levels of initial velocity skewness in addition to an axisymmetric jet from a straight pipe. In case of the curved pipe, a six diameterlong straight pipe section follows the bend upstream of the exit. The Reynolds number based on the exit bulk velocity is 13,400. The results indicate that the near field structure is considerably modified by the skewness of an initial mean velocity distribution. As the skewness increases, the decay rate of mean velocity at the centerline also increases

  10. Conductivity-Dependent Flow Field-Flow Fractionation of Fulvic and Humic Acid Aggregates

    Directory of Open Access Journals (Sweden)

    Martha J. M. Wells

    2015-09-01

    Full Text Available Fulvic (FAs and humic acids (HAs are chemically fascinating. In water, they have a strong propensity to aggregate, but this research reveals that tendency is regulated by ionic strength. In the environment, conductivity extremes occur naturally—freshwater to seawater—warranting consideration at low and high values. The flow field flow fractionation (flow FFF of FAs and HAs is observed to be concentration dependent in low ionic strength solutions whereas the corresponding flow FFF fractograms in high ionic strength solutions are concentration independent. Dynamic light scattering (DLS also reveals insight into the conductivity-dependent behavior of humic substances (HSs. Four particle size ranges for FAs and humic acid aggregates are examined: (1 <10 nm; (2 10 nm–6 µm; (3 6–100 µm; and (4 >100 µm. Representative components of the different size ranges are observed to dynamically coexist in solution. The character of the various aggregates observed—such as random-extended-coiled macromolecules, hydrogels, supramolecular, and micellar—as influenced by electrolytic conductivity, is discussed. The disaggregation/aggregation of HSs is proposed to be a dynamic equilibrium process for which the rate of aggregate formation is controlled by the electrolytic conductivity of the solution.

  11. Shape optimisation and performance analysis of flapping wings

    KAUST Repository

    Ghommem, Mehdi

    2012-09-04

    In this paper, shape optimisation of flapping wings in forward flight is considered. This analysis is performed by combining a local gradient-based optimizer with the unsteady vortex lattice method (UVLM). Although the UVLM applies only to incompressible, inviscid flows where the separation lines are known a priori, Persson et al. [1] showed through a detailed comparison between UVLM and higher-fidelity computational fluid dynamics methods for flapping flight that the UVLM schemes produce accurate results for attached flow cases and even remain trend-relevant in the presence of flow separation. As such, they recommended the use of an aerodynamic model based on UVLM to perform preliminary design studies of flapping wing vehicles Unlike standard computational fluid dynamics schemes, this method requires meshing of the wing surface only and not of the whole flow domain [2]. From the design or optimisation perspective taken in our work, it is fairly common (and sometimes entirely necessary, as a result of the excessive computational cost of the highest fidelity tools such as Navier-Stokes solvers) to rely upon such a moderate level of modelling fidelity to traverse the design space in an economical manner. The objective of the work, described in this paper, is to identify a set of optimised shapes that maximise the propulsive efficiency, defined as the ratio of the propulsive power over the aerodynamic power, under lift, thrust, and area constraints. The shape of the wings is modelled using B-splines, a technology used in the computer-aided design (CAD) field for decades. This basis can be used to smoothly discretize wing shapes with few degrees of freedom, referred to as control points. The locations of the control points constitute the design variables. The results suggest that changing the shape yields significant improvement in the performance of the flapping wings. The optimisation pushes the design to "bird-like" shapes with substantial increase in the time

  12. Extensive lava flow fields on Venus: Preliminary investigation of source elevation and regional slope variations

    Science.gov (United States)

    Magee-Roberts, K.; Head, James W., III; Lancaster, M. G.

    1992-01-01

    Large-volume lava flow fields have been identified on Venus, the most areally extensive of which are known as fluctus and have been subdivided into six morphologic types. Sheetlike flow fields (Type 1) lack the numerous, closely spaced, discrete lava flow lobes that characterize digitate flow fields. Transitional flow fields (Type 2) are similar to sheetlike flow fields but contain one or more broad flow lobes. Digitate flow fields are divided further into divergent (Types 3-5) and subparallel (Type 6) classes on the basis of variations in the amount of downstream flow divergence. As a result of our previous analysis of the detailed morphology, stratigraphy, and tectonic associations of Mylitta Fluctus, we have formulated a number of questions to apply to all large flow fields on Venus. In particular, we would like to address the following: (1) eruption conditions and style of flow emplacement (effusion rate, eruption duration), (2) the nature of magma storage zones (presence of neutral buoyancy zones, deep or shallow crustal magma chambers), (3) the origin of melt and possible link to mantle plumes, and (4) the importance of large flow fields in plains evolution. To answer these questions we have begun to examine variations in flow field dimension and morphology; the distribution of large flow fields in terms of elevation above the mean planetary radius; links to regional tectonic or volcanic structures (e.g., associations with large shield edifices, coronae, or rift zones); statigraphic relationships between large flow fields, volcanic plains, shields, and coronae; and various models of flow emplacement in order to estimate eruption parameters. In this particular study, we have examined the proximal elevations and topographic slopes of 16 of the most distinctive flow fields that represent each of the 6 morphologic types.

  13. Evaluation of the flow-accelerated corrosion downstream of an orifice. 1. Measurements and numerical analysis of flow field

    International Nuclear Information System (INIS)

    Utanohara, Yoichi; Nagaya, Yukinori; Nakamura, Akira; Murase, Michio

    2008-01-01

    In this study, in order to evaluate the effects of flow field on corrosion rate due to flow accelerated corrosion (FAC), an orifice flow was measured and calculated. The diameter of pipe is 50 mm and that of the orifice is 24.3 mm, and flow velocity in a water loop was set at 2.41 m/s. Flow field was measured by laser Doppler velocimetry (LDV) and particle image velocimetry (PIV), and compared with a calculation for the same flow conditions. Measurements of wall shear stress downstream of the orifice was also planed. The calculated velocity distribution of standard k-□ agreed qualitatively with PIV data and quantitatively with LDV data. Instantaneous flow field measured by PIV showed vortices around the jet from the orifice and some of them reached near the pipe wall. (author)

  14. Optimization and evaluation of asymmetric flow field-flow fractionation of silver nanoparticles

    DEFF Research Database (Denmark)

    Löschner, Katrin; Navratilova, Jana; Legros, Samuel

    2013-01-01

    Asymmetric flow field-flow fractionation (AF(4)) in combination with on-line optical detection and mass spectrometry is one of the most promising methods for separation and quantification of nanoparticles (NPs) in complex matrices including food. However, to obtain meaningful results regarding...... especially the NP size distribution a number of parameters influencing the separation need to be optimized. This paper describes the development of a separation method for polyvinylpyrrolidone-stabilized silver nanoparticles (AgNPs) in aqueous suspension. Carrier liquid composition, membrane material, cross...... obtained by the three detection methods were explained based on the physical origin of the signal. Two different approaches for conversion of retention times of AgNPs to their corresponding sizes and size distributions were tested and compared, namely size calibration with polystyrene nanoparticles (PSNPs...

  15. Nanoparticle separation with a miniaturized asymmetrical flow field-flow fractionation cartridge

    Science.gov (United States)

    Müller, David; Cattaneo, Stefano; Meier, Florian; Welz, Roland; de Mello, Andrew J.

    2015-01-01

    Asymmetrical Flow Field-Flow Fractionation (AF4) is a separation technique applicable to particles over a wide size range. Despite the many advantages of AF4, its adoption in routine particle analysis is somewhat limited by the large footprint of currently available separation cartridges, extended analysis times and significant solvent consumption. To address these issues, we describe the fabrication and characterization of miniaturized AF4 cartridges. Key features of the down-scaled platform include simplified cartridge and reagent handling, reduced analysis costs and higher throughput capacities. The separation performance of the miniaturized cartridge is assessed using certified gold and silver nanoparticle standards. Analysis of gold nanoparticle populations indicates shorter analysis times and increased sensitivity compared to conventional AF4 separation schemes. Moreover, nanoparticulate titanium dioxide populations exhibiting broad size distributions are analyzed in a rapid and efficient manner. Finally, the repeatability and reproducibility of the miniaturized platform are investigated with respect to analysis time and separation efficiency. PMID:26258119

  16. Nanoparticle separation with a miniaturized asymmetrical flow field-flow fractionation cartridge

    Directory of Open Access Journals (Sweden)

    David eMüller

    2015-07-01

    Full Text Available Asymmetrical Flow Field-Flow Fractionation (AF4 is a separation technique applicable to particles over a wide size range. Despite the many advantages of AF4, its adoption in routine particle analysis is somewhat limited by the large footprint of currently available separation cartridges, extended analysis times and significant solvent consumption. To address these issues, we describe the fabrication and characterization of miniaturized AF4 cartridges. Key features of the scale-down platform include simplified cartridge and reagent handling, reduced analysis costs and higher throughput capacities. The separation performance of the miniaturized cartridge is assessed using certified gold and silver nanoparticle standards. Analysis of gold nanoparticle populations indicates shorter analysis times and increased sensitivity compared to conventional AF4 separation schemes. Moreover, nanoparticulate titanium dioxide populations exhibiting broad size distributions are analyzed in a rapid and efficient manner. Finally, the repeatability and reproducibility of the miniaturized platform are investigated with respect to analysis time and separation efficiency.

  17. Separation of platelets from other blood cells in continuous-flow by dielectrophoresis field-flow-fractionation

    OpenAIRE

    Piacentini, Niccolò; Mernier, Guillaume; Tornay, Raphaël; Renaud, Philippe

    2011-01-01

    We present a microfluidic device capable of separating platelets from other blood cells in continuous flow using dielectrophoresis field-flow-fractionation. The use of hydrodynamic focusing in combination with the application of a dielectrophoretic force allows the separation of platelets from red blood cells due to their size difference. The theoretical cell trajectory has been calculated by numerical simulations of the electrical field and flow speed, and is in agreement with the experiment...

  18. Physical cleaning by bubbly streaming flow in an ultrasound field

    Science.gov (United States)

    Yamashita, Tatsuya; Ando, Keita

    2017-11-01

    Low-intensity ultrasonic cleaning with gas-supersaturated water is a promising method of physical cleaning without erosion; we are able to trigger cavitation bubble nucleation by weak ultrasound under gas supersaturation and thus clean material surfaces by mild bubble dynamics. Here, we perform particle image velocimetry (PIV) measurement of liquid flow and cavitation bubble translation in an ultrasonic cleaning bath driven at 28 kHz and then relate it to cleaning tests using glass slides at which silica particles are attached. The ultrasound pressure amplitude at the cleaning spot is set at 1.4 atm. We select the supersaturation level of dissolved oxygen (DO) as a parameter and control it by oxygen microbubble aeration. It follows from the PIV measurement that the liquid flow is enhanced by the cavitation bubble translation driven by acoustic radiation force; this trend becomes clearer when the bubbles appear more densely as the DO supersaturation increases. In the cleaning tests, the cleaned areas appear as straight streaks. This suggests that physical cleaning is achieved mainly by cavitation bubbles that translate in ultrasound fields.

  19. Biomat flow: fluorescent dye field experiments, pore-scale modeling of flow and transport properties, and field-scale flow models

    Science.gov (United States)

    Gerke, K.; Sidle, R. C.; Mallants, D.; Vasilyev, R.; Karsanina, M.; Skvortsova, E. B.; Korost, D. V.

    2013-12-01

    Recent studies highlight the important role that the upper litter layer in forest soils (biomat) plays in hillslope and catchment runoff generation. This biomat layer is a very loose material with high porosity and organic content. Direct sampling is usually problematic due to limited layer thickness. Conventional laboratory measurements can mobilize solids or even cause structure failure of the sample thus making measurements unreliable. It is also difficult to assess local variation in soil properties and transition zones using these methods; thus, they may not be applicable to biomat studies. However, if the physics of flow through this layer needs to be quantified and incorporated into a model, a detailed study of hydraulic properties is necessary. Herein we show the significance of biomat flow by staining experiments in the field, study its structure and transition to mineral soil layer using X-ray micro-tomography, assess hydraulic properties and structure differences using a pore-scale modeling approach, and, finally, use conventional variably-saturated flow modeling based on Richards equation to simulate flow in the hillslope. Using staining tracers we show that biomat flow in forested hillslopes can extend long distances (lateral displacement was about 1.2 times larger than for subsurface lateral flow) before infiltration occurs into deeper layers. The three-dimensional structure of an undisturbed sample (4 x 3 x 2.5 cm) of both biomat and deeper consolidated soil was obtained using an X-ray micro-tomography device with a resolution of 15 um. Local hydraulic properties (e.g., permeability and water retention curve) for numerous layers (e.g., transition zones, biomat, mineral soil) were calculated using Stokes flow FDM solution and pore-network modeling. Anisotropy, structure differences, and property fluctuations of different layers were quantified using local porosity analysis and correlation functions. Current results support the hypothesis that small

  20. Application of a flow generated by IR laser and AC electric field in micropumping and micromixing

    International Nuclear Information System (INIS)

    Nakano, M; Mizuno, A

    2008-01-01

    In this paper, it is described that measurement of fluid flow generated by simultaneous operation of an infrared (IR) laser and AC electric field in a microfabricated channel. When an IR laser (1026 nm) was focused under an intense AC electric field, a circulating flow was generated around the laser focus. The IR laser and the electric field generate two flow patterns of the electrohydrodynamicss. When the laser focus is placed at the center of the gap between electrodes, the flow pattern is parallel to the AC electric field toward electrodes from the centre. On the other hand, when the laser focus is placed close to one of the electrodes, one directional flow is generated. First flow pattern can be used as a micromixer and the second one as a micropump. Flow velocity profiles of the two flow patterns were measured as a function of the laser power, intensity of the AC electric field and AC frequency.

  1. Flow field characteristics of impinging sweeping jets: TR-PIV measurement

    Science.gov (United States)

    Wen, Xin; Peng, Di; Liu, Yingzheng; Tang, Hui

    2017-11-01

    Influence of Reynolds number of sweeping jets on its impinging flow fields was extensively investigated in a water tank. Toward this end, a fluidic oscillator was specially designed to produce spatially sweeping jets which imping on a flat plate. Six Reynolds numbers were tested by controlling the supply flow rate of the fluidic oscillator. Impinging flow fields were captured by time-resolved Particle Image Velocimetry (TR-PIV) measurement. Reference signals were extracted from the flow fields for phase reconstruction. The oscillating flow fields with super-harmonic frequency at different regions were discussed in term of the phase-averaged velocity, vorticity and turbulent velocity. Dynamic mode decomposition (DMD) was used to capture the most-energetic flow patterns with distinct frequencies. By projecting the phase-averaged flow fields onto a reduced basis of DMD modes, the phase correlation between the distinct flow patterns were analyzed under different Reynolds numbers.

  2. Numerical Study of Flow Motion and Patterns Driven by a Rotating Permanent Helical Magnetic Field

    Science.gov (United States)

    Yang, Wenzhi; Wang, Xiaodong; Wang, Bo; Baltaretu, Florin; Etay, Jacqueline; Fautrelle, Yves

    2016-10-01

    Liquid metal magnetohydrodynamic flow driven by a rotating permanent helical magnetic field in a cylindrical container is numerically studied. A three-dimensional numerical simulation provides insight into the visualization of the physical fields, including the magnetic field, the Lorentz force density, and the flow structures, especially the flow patterns in the meridional plane. Because the screen parameter is sufficiently small, the model is decoupled into electromagnetic and hydrodynamic components. Two flow patterns in the meridional plane, i.e., the global flow and the secondary flow, are discovered and the impact of several system parameters on their transition is investigated. Finally, a verifying model is used for comparison with the previous experiment.

  3. Computation of Lifting Wing-Flap Configurations

    Science.gov (United States)

    Cantwell, Brian; Kwak, Dochan

    1996-01-01

    Research has been carried out on the computation of lifting wing-flap configurations. The long term goal of the research is to develop improved computational tools for the analysis and design of high lift systems. Results show that state-of-the-art computational methods are sufficient to predict time-averaged lift and overall flow field characteristics on simple high-lift configurations. Recently there has been an increased interest in the problem of airframe generated noise and experiments carried out in the 7 x 10 wind tunnel at NASA Ames have identified the flap edge as an important source of noise. A follow-on set of experiments will be conducted toward the end of 1995. The computations being carried out under this project are coordinated with these experiments. In particular, the model geometry being used in the computations is the same as that in the experiments. The geometry consists of a NACA 63-215 Mod B airfoil section which spans the 7 x lO tunnel. The wing is unswept and has an aspect ratio of two. A 30% chord Fowler flap is deployed modifications of the flap edge geometry have been shown to be effective in reducing noise and the existing code is currently being used to compute the effect of a modified geometry on the edge flow.

  4. Analysis of the pressure fields in a swirling annular jet flow

    NARCIS (Netherlands)

    Perçin, M.; Vanierschot, M.; van Oudheusden, B.W.

    2017-01-01

    In this paper, we investigate the flow structures and pressure fields of a free annular swirling jet flow undergoing vortex breakdown. The flow field is analyzed by means of time-resolved tomographic particle image velocimetry measurements, which enable the reconstruction of the three-dimensional

  5. Numerical study of aerodynamic characteristics of FSW aircraft with different wing positions under supersonic condition

    Directory of Open Access Journals (Sweden)

    Lei Juanmian

    2016-08-01

    Full Text Available This paper investigates the influence of forward-swept wing (FSW positions on the aerodynamic characteristics of aircraft under supersonic condition (Ma = 1.5. The numerical method based on Reynolds-averaged Navier–Stokes (RANS equations, Spalart–Allmaras (S–A turbulence model and implicit algorithm is utilized to simulate the flow field of the aircraft. The aerodynamic parameters and flow field structures of the horizontal tail and the whole aircraft are presented. The results demonstrate that the spanwise flow of FSW flows from the wingtip to the wing root, generating an upper wing surface vortex and a trailing edge vortex nearby the wing root. The vortexes generated by FSW have a strong downwash effect on the tail. The lower the vertical position of FSW, the stronger the downwash effect on tail. Therefore, the effective angle of attack of tail becomes smaller. In addition, the lift coefficient, drag coefficient and lift–drag ratio of tail decrease, and the center of pressure of tail moves backward gradually. For the whole aircraft, the lower the vertical position of FSW, the smaller lift, drag and center of pressure coefficients of aircraft. The closer the FSW moves towards tail, the bigger pitching moment and center of pressure coefficients of the whole aircraft, but the lift and drag characteristics of the horizontal tail and the whole aircraft are basically unchanged. The results have potential application for the design of new concept aircraft.

  6. Program to stimulate graduate training in the field of aeroacoustics. [cross correlation of flow fields of a jet-blown flap with far fields

    Science.gov (United States)

    Becker, R. S.

    1975-01-01

    An experiment is reported to cross correlate the output of hot film probes located at various points in the flow field of a jet-blown flap with the output of microphones in the acoustic far field. Fluid dynamic measurements of the flow fields of the test configuration are reported.

  7. Research on the spatial structure of crude oil flow and the characteristics of its flow field in China

    International Nuclear Information System (INIS)

    Zhao, Yuan; Hao, Li-Sha; Wan, Lu

    2007-01-01

    Crude oil flow is a sort of oil spatial movement, and in China, it is large scale and covers wide area with extensive social-economic effects. This paper analyses the spatial structure of crude oil flow in China, the characters of its flow field and the layout of its flow track. The results show that oil flow in China has a spatial characteristic of centralized output and decentralized input; its spatial structure is composed of Source System in the shape of right-angled triangle, Confluence System in the shape of right-angled trapezium and Multiplex System in the shape of obtuse-angled triangle, which are mutually nested, and on a whole, the presence of Multiplex System balances and optimizes the flow layout; oil flow field in China can be divided into four parts, i.e. the North, North-west, East and South Field, two or three of which overlap with each other, extending the oil flow and making the flow more flexible and maneuverable; oil flow track is a multi-objective decision-making route and in the decision-making process oil transportation cost is one of the essential factors, in China, oil flow track falls into the Northeast, North, East, Northwest and South five cluster regions, which connect with each other, and series-parallel connection between various kinds of transportation channels is widely seen in them, reinforcing the supply security of crude oil

  8. Time Resolved Digital PIV Measurements of Flow Field Cyclic Variation in an Optical IC Engine

    International Nuclear Information System (INIS)

    Jarvis, S; Justham, T; Clarke, A; Garner, C P; Hargrave, G K; Halliwell, N A

    2006-01-01

    Time resolved digital particle image velocimetry (DPIV) experimental data is presented for the in-cylinder flow field development of a motored four stroke spark ignition (SI) optical internal combustion (IC) engine. A high speed DPIV system was employed to quantify the velocity field development during the intake and compression stroke at an engine speed of 1500 rpm. The results map the spatial and temporal development of the in-cylinder flow field structure allowing comparison between traditional ensemble average and cycle average flow field structures. Conclusions are drawn with respect to engine flow field cyclic variations

  9. Three-dimensional numerical study on cell performance and transport phenomena of PEM fuel cells with conventional flow fields

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Jer-Huan [Department of Mechanical Engineering, Northern Taiwan Institute of Science and Technology, Beitou, Taipei 11202 (China); Yan, Wei-Mon; Li, Hung-Yi; Tsai, Wei-Che [Department of Mechatronic Engineering, Huafan University, Shih-Ting, Taipei 22305 (China)

    2008-01-15

    In this paper, a three-dimensional numerical model of the proton exchange membrane fuel cells (PEMFCs) with conventional flow field designs (parallel flow field, Z-type flow field, and serpentine flow field) has been established to investigate the performance and transport phenomena in the PEMFCs. The influences of the flow field designs on the fuel utilization, the water removal, and the cell performance of the PEMFC are studied. The distributions of velocity, oxygen mass fraction, current density, liquid water, and pressure with the convention flow fields are presented. For the conventional flow fields, the cell performance can be enhanced by adding the corner number, increasing the flow channel length, and decreasing the flow channel number. The cell performance of the serpentine flow field is the best, followed by the Z-type flow field and then the parallel flow field. (author)

  10. Measurements of non-reacting and reacting flow fields of a liquid swirl flame burner

    Science.gov (United States)

    Chong, Cheng Tung; Hochgreb, Simone

    2015-03-01

    The understanding of the liquid fuel spray and flow field characteristics inside a combustor is crucial for designing a fuel efficient and low emission device. Characterisation of the flow field of a model gas turbine liquid swirl burner is performed by using a 2-D particle imaging velocimetry(PIV) system. The flow field pattern of an axial flow burner with a fixed swirl intensity is compared under confined and unconfined conditions, i.e., with and without the combustor wall. The effect of temperature on the main swirling air flow is investigated under open and non-reacting conditions. The result shows that axial and radial velocities increase as a result of decreased flow density and increased flow volume. The flow field of the main swirling flow with liquid fuel spray injection is compared to non-spray swirling flow. Introduction of liquid fuel spray changes the swirl air flow field at the burner outlet, where the radial velocity components increase for both open and confined environment. Under reacting condition, the enclosure generates a corner recirculation zone that intensifies the strength of radial velocity. The reverse flow and corner recirculation zone assists in stabilizing the flame by preheating the reactants. The flow field data can be used as validation target for swirl combustion modelling.

  11. A video-image study of electrolytic flow structure in parallel electric-magnetic fields

    International Nuclear Information System (INIS)

    Gu, Z.H.; Fahidy, T.Z.

    1987-01-01

    The structure of free convective flow propagating from a vertical cathode into the electrolyte bulk has been studied via video-imaging. The enhancing effect of imposed horizontal uniform magnetic fields is manifest by vortex propagation and bifurcating flow

  12. Cfd Simulation to the Flow Field of Venturi Injector

    Science.gov (United States)

    Huang, Xingfa; Li, Guangyong; Wang, Miao

    Venturi injector is widely used in fertigation system due to its obvious advantages such as cheap and robust system without mobile pieces, simple structure, convenient to operation, stable performance, needless of external energy for operation etc. At present, the hydraulic parameters such as suction capacity (injection rate) for the most of the Venturi injectors produced domestically are not very desirable. In this paper, CFD (Computational Fluid Dynamics) method was used to simulate the inner flow field of the Venturi injectors, and the relationships among the structure parameters (i.e., throat length L, throat diameter D, slot diameter Da) and suction capacity q, and the optimal structure sizes of the Venturi injector were analyzed. The results show that when the inlet pressure and the slot position are kept unchanged as the sample one, the suction capacity of Venturi injector increases with the decrease of throat diameter D and throat length L, and the increase of slot diameter Da; while keeping the slot diameter Da, throat diameter D and throat length L unchanged, the suction capacity of Venturi injector q increases with the increase of inlet pressure P. The optimal combination of the structural parameters in this size was selected as follows: throat diameter D=8mm, slot diameter Da=18.5mm, and throat length L=14mm. In this case, the suction capacity of the Venturi injector q=1.203m3/h. The results can provide theoretic support for domestic Venturi injector research, design and manufacturing.

  13. Effect of an electromagnetic field on the spectra and elliptic flow of particles

    OpenAIRE

    Feng, Bohao; Wang, Zeyan

    2017-01-01

    In 2+1 dimensions, the evolution of flow under the influence of an external electromagnetic field is simulated. The external electromagnetic field is exponentially decaying with time. Under the same initial conditions, flow evolution with and without the external electromagnetic field is compared. It was found that the production of particles was enhanced when the external electromagnetic field was present. As the strength of the electromagnetic field increased, more particles were produced. ...

  14. Rice starch granule characterization by flow cytometry scattering techniques hyphenated with sedimentation field-flow fractionation.

    Science.gov (United States)

    Clédat, Dominique; Battu, Serge; Mokrini, Redouane; Cardot, Philippe J P

    2004-09-17

    Sedimentation field-flow fractionation (SdFFF) elution mode of micron sized particle is described generically as "Hyperlayer" and involves particle size, density, shape and rigidity. It requires the use of specific detectors of mass, size, surface, or of other characteristics of the eluted particles. Correlation of FFF retention data with such signals gives hyphenated information about particle properties. Flow cytometry (FC) is a multi dimensional particle counter, which permits specific particle property characterization using light scattering and fluorescence principles. It appears therefore as a powerful technique for micron sized species description. FC is mostly known for cell analyses, while its potential is much broader once proper calibration performed. In this report, forward angle signal (FS) is calibrated in size by using standard latex beads and produces, for a given particle sample, a number versus size histogram, describing particle size distribution. These histograms can be an alternative to Coulter counting. That methodology is tested with rice starch population (RSP) fractions obtained from FFF separation.

  15. The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

    KAUST Repository

    Elbaz, Ayman M.

    2015-08-29

    The stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work. The stability map of partial premixed flames illustrates that the flames are stable between two extinction limits. A low extinction limit when partial premixed flames approach non-premixed flame conditions, and a high extinction limit, with the partial premixed flames approach fully premixed flame conditions. These two limits showed that the most stable flame conditions are achieved at a certain degree of partial premixed. The stability is improved by adding air co-flow. As the air co-flow velocity increases the most stable flames are those that approach fully premixed. The turbulent flow field of three flames at 0, 5, 10 m/s co-flow velocity are investigated using Stereo Particle Image Velocimetry (SPIV) in order to explore the improvement of the flame stability due to the use of air co-flow. The three flames are all at a jet equivalence ratio (Φj) of 2, fixed level of partial premixing and jet Reynolds number (Rej) of 10,000. The use of co-flow results in the formation of two vortices at the cone exit. These vortices act like stabilization anchors for the flames to the nozzle tip. With these vortices in the flow field, the reaction zone shifts toward the reduced turbulence intensity at the nozzle rim of the cone. Interesting information about the structure of the flow field with and without co-flow are identified and reported in this work.

  16. Apparatus and method for using radar to evaluate wind flow fields for wind energy applications

    Science.gov (United States)

    Schroeder, John; Hirth, Brian; Guynes, Jerry

    2017-02-21

    The present invention provides an apparatus and method for obtaining data to determine one or more characteristics of a wind flow field using one or more radars. Data is collected from the one or more radars, and analyzed to determine the one or more characteristics of the wind flow field. The one or more radars are positioned to have a portion of the wind flow field within a scanning sector of the one or more radars.

  17. Combined particle-image velocimetry and force analysis of the three-dimensional fluid-structure interaction of a natural owl wing.

    Science.gov (United States)

    Winzen, A; Roidl, B; Schröder, W

    2016-04-01

    Low-speed aerodynamics has gained increasing interest due to its relevance for the design process of small flying air vehicles. These small aircraft operate at similar aerodynamic conditions as, e.g. birds which therefore can serve as role models of how to overcome the well-known problems of low Reynolds number flight. The flight of the barn owl is characterized by a very low flight velocity in conjunction with a low noise emission and a high level of maneuverability at stable flight conditions. To investigate the complex three-dimensional flow field and the corresponding local structural deformation in combination with their influence on the resulting aerodynamic forces, time-resolved stereoscopic particle-image velocimetry and force and moment measurements are performed on a prepared natural barn owl wing. Several spanwise positions are measured via PIV in a range of angles of attack [Formula: see text] 6° and Reynolds numbers 40 000 [Formula: see text] 120 000 based on the chord length. Additionally, the resulting forces and moments are recorded for -10° ≤ α ≤ 15° at the same Reynolds numbers. Depending on the spanwise position, the angle of attack, and the Reynolds number, the flow field on the wing's pressure side is characterized by either a region of flow separation, causing large-scale vortical structures which lead to a time-dependent deflection of the flexible wing structure or wing regions showing no instantaneous deflection but a reduction of the time-averaged mean wing curvature. Based on the force measurements the three-dimensional fluid-structure interaction is assumed to considerably impact the aerodynamic forces acting on the wing leading to a strong mechanical loading of the interface between the wing and body. These time-depending loads which result from the flexibility of the wing should be taken into consideration for the design of future small flying air vehicles using flexible wing structures.

  18. Analysis on the design and property of flow field plates of innovative direct methanol fuel cell.

    Science.gov (United States)

    Chang, Ho; Kao, Mu-Jung; Chen, Chih-Hao; Kuo, Chin-Guo; Lee, Kuang-Ying

    2014-10-01

    The paper uses technology of lithography process to etch flow fields on single side of a printed circuit board (PCB), and combines flow field plate with collector plate to make innovative anode flow field plates and cathode flow field plates required in direct methanol fuel cell (DMFC), and meanwhile makes membrane electrode assembly (MEA) and methanol fuel plate. The flow field plates are designed to be in the form of serpentine flow field. The paper measured the assembled DMFC to achieve the overall efficiency of DMFC under the conditions of different screw torques and different concentration, flow rate and temperature of methanol. Experimental results show that when the flow field width of flow field plate is 1 mm, the screw torque is 16 kgf/cm, and the concentration, flow rate and temperature of methanol-water are 1 M, 180 ml/h and 50 degrees C respectively, the prepared DMFC can have better power density of 5.5 mW/cm2, 5.4 mW/cm2, 11.2 mW/cm2 and 11.8 mW/cm2. Besides, the volume of the DMFC designed and assembled by the study is smaller than the generally existing DMFC by 40%.

  19. Structure of the radial electric field and toroidal/poloidal flow in high temperature toroidal plasma

    International Nuclear Information System (INIS)

    Ida, Katsumi

    2001-01-01

    The structure of the radial electric field and toroidal/poloidal flow is discussed for the high temperature plasma in toroidal systems, tokamak and Heliotron type magnetic configurations. The spontaneous toroidal and poloidal flows are observed in the plasma with improved confinement. The radial electric field is mainly determined by the poloidal flow, because the contribution of toroidal flow to the radial electric field is small. The jump of radial electric field and poloidal flow are commonly observed near the plasma edge in the so-called high confinement mode (H-mode) plasmas in tokamaks and electron root plasma in stellarators including Heliotrons. In general the toroidal flow is driven by the momentum input from neutral beam injected toroidally. There is toroidal flow not driven by neutral beam in the plasma and it will be more significant in the plasma with large electric field. The direction of these spontaneous toroidal flows depends on the symmetry of magnetic field. The spontaneous toroidal flow driven by the ion temperature gradient is in the direction to increase the negative radial electric field in tokamak. The direction of spontaneous toroidal flow in Heliotron plasmas is opposite to that in tokamak plasma because of the helicity of symmetry of the magnetic field configuration. (author)

  20. Research on the flow field of undershot cross-flow water turbines using experiments and numerical analysis

    International Nuclear Information System (INIS)

    Nishi, Y; Inagaki, T; Li, Y; Omiya, R; Hatano, K

    2014-01-01

    The purpose of this research is to develop a water turbine appropriate for low-head open channels in order to effectively utilize the unused hydropower energy of rivers and agricultural waterways. The application of the cross-flow runner to open channels as an undershot water turbine has come under consideration and, to this end, a significant simplification was attained by removing the casings. However, the flow field of undershot cross-flow water turbines possesses free surfaces. This means that with the variation in the rotational speed, the water depth around the runner will change and flow field itself is significantly altered. Thus it is necessary to clearly understand the flow fields with free surfaces in order to improve the performance of this turbine. In this research, the performance of this turbine and the flow field were studied through experiments and numerical analysis. The experimental results on the performance of this turbine and the flow field were consistent with the numerical analysis. In addition, the inlet and outlet regions at the first and second stages of this water turbine were clarified

  1. Flapping and fixed wing aerodynamics of low Reynolds number flight vehicles

    Science.gov (United States)

    Viieru, Dragos

    Lately, micro air vehicles (MAVs), with a maximum dimension of 15 cm and nominal flight speed around 10m/s, have attracted interest from scientific and engineering communities due to their potential to perform desirable flight missions and exhibit unconventional aerodynamics, control, and structural characteristics, compared to larger flight vehicles. Since MAVs operate at a Reynolds number of 105 or lower, the lift-to-drag ratio is noticeably lower than the larger manned flight vehicles. The light weight and low flight speed cause MAVs to be sensitive to wind gusts. The MAV's small overall dimensions result in low aspect ratio wings with strong wing tip vortices that further complicate the aerodynamics of such vehicles. In this work, two vehicle concepts are considered, namely, fixed wings with flexible structure aimed at passive shape control, and flapping wings aimed at enhancing aerodynamic performance using unsteady flow fields. A finite volume, pressure-based Navier-Stokes solver along with moving grid algorithms is employed to simulate the flow field. The coupled fluid-structural dynamics of the flexible wing is treated using a hyperelastic finite element structural model, the above-mentioned fluid solver via the moving grid technique, and the geometric conservation law. Three dimensional aerodynamics around a low aspect ratio wing for both rigid and flexible structures and fluid-structure interactions for flexible structures have been investigated. In the Reynolds numbers range of 7x10 4 to 9x104, the flexible wing exhibits self-initiated vibrations even in steady free-stream, and is found to have a similar performance to the identical rigid wing for modest angles of attack. For flapping wings, efforts are made to improve our understanding of the unsteady fluid physics related to the lift generation mechanism at low Reynolds numbers (75 to 1,700). Alternative moving grid algorithms, capable of handling the large movements of the boundaries (characteristic

  2. Rock glaciers Gruben, Muragl and Murtel, Switzerland: Area-wide flow fields, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — Besides their thermal and mechanical properties, rock glaciers are essentially defined by their kinematics. Knowledge of the permafrost flow field provides important...

  3. Toward the Experimental Characterization of an Unmanned Air System Flow Field

    Science.gov (United States)

    Velarde, John-Michael; Connors, Jacob; Glauser, Mark

    2017-11-01

    The velocity flow field around a small unmanned air system (sUAS) is investigated in a series of experiments at Syracuse University. Experiments are conducted in the 2'x2' sub-sonic wind tunnel at Syracuse University and the Indoor Flow Lab. The goal of these experiments is to gain a better understanding of the rich, turbulent flow field that a sUAS creates. Comparison to large, multi-rotor manned vehicles is done to gain a better understanding of the flow physics that could be occurring with the sUAS. Regions of investigation include the downwash, above the vehicle, and far downstream. Characterization of the flow is performed using hotwire anemometry. Investigation of several locations around the sUAS show that dominant frequencies exist within the flow field. Analysis of the flow field using power spectral density will be presented as well as looking at which parameters have an effect on these dominant frequencies.

  4. On the use of various oscillatory air flow fields for characterization of biomimetic hair flow sensors

    NARCIS (Netherlands)

    Droogendijk, H.; Dagamseh, A.M.K.; Yntema, Doekle Reinder; Sanders, Remco G.P.; Krijnen, Gijsbertus J.M.

    To determine the characteristics of flow sensors, a suitable source for flow generation is required. We discuss three different sources for oscillating air flow, by considering their acoustic impedance, frequency range, velocity and ability to distinguish between flow and pressure. We discuss the

  5. Local transport phenomena and cell performance of PEM fuel cells with various serpentine flow field designs

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiao-Dong [Department of Thermal Engineering, School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Duan, Yuan-Yuan [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084 (China); Yan, Wei-Mon [Department of Mechatronic Engineering, Huafan University, Taipei 22305 (China); Peng, Xiao-Feng [Laboratory of Phase Change and Interfacial Transport Phenomena, Tsinghua University, Beijing 100084 (China)

    2008-01-03

    The flow field design in bipolar plates is very important for improving reactant utilization and liquid water removal in proton exchange membrane fuel cells (PEMFCs). A three-dimensional model was used to analyze the effect of the design parameters in the bipolar plates, including the number of flow channel bends, number of serpentine flow channels and the flow channel width ratio, on the cell performance of miniature PEMFCs with the serpentine flow field. The effect of the liquid water formation on the porosities of the porous layers was also taken into account in the model while the complex two-phase flow was neglected. The predictions show that (1) for the single serpentine flow field, the cell performance improves as the number of flow channel bends increases; (2) the single serpentine flow field has better performance than the double and triple serpentine flow fields; (3) the cell performance only improves slowly as the flow channel width increases. The effects of these design parameters on the cell performance were evaluated based on the local oxygen mass flow rates and liquid water distributions in the cells. Analysis of the pressure drops showed that for these miniature PEMFCs, the energy losses due to the pressure drops can be neglected because they are far less than the cell output power. (author)

  6. Liquid metal flow in a finite-length cylinder with a rotating magnetic field

    International Nuclear Information System (INIS)

    Gelfgat, Yu.M.; Gorbunov, L.A.; Kolevzon, V.

    1993-01-01

    A liquid metal flow induced by a rotating magnetic field in a cylindrical container of finite height was investigated experimentally. It was demonstrated that the flow in a rotating magnetic field is similar to geophysical flows: the fluid rotates uniformly with depth and the Ekman layer exists at the container bottom. Near the vertical wall the flow is depicted in the form of a confined jet whose thickness determines the instability onset in a rotating magnetic field. It was shown that the critical Reynolds number can be found by using the jet velocity u 0 for Re cr =u 2 0 /ν∂u/∂r. The effect of frequency of a magnetic field on the fluid flow was also studied. An approximate theoretical model is presented for describing the fluid flow in a uniform rotating magnetic field. (orig.)

  7. A tapered serpentine flow field for the anode of micro direct methanol fuel cells

    Science.gov (United States)

    Zhang, Yufeng; Zhang, Peng; Yuan, Zhenyu; He, Hong; Zhao, Youran; Liu, Xiaowei

    2011-03-01

    We develop a self-breathing micro direct methanol fuel cell (μDMFC) characterized by a new anode structure with tapered single serpentine flow fields to improve cell performance. Compared with the conventional single serpentine flow field, this new design enhances the methanol mass transport efficiency and the exhaust resultant (CO2) rate due to the increasing pressure difference between adjacent flow channels. The μDMFCs with two single serpentine flow fields are fabricated using silicon-based micro-electro-mechanical systems (MEMS) technologies and are tested at room temperature. The experimental results reveal that the new tapered single serpentine flow field exhibits a significantly higher peak power density than that of the conventional flow field, demonstrating a substantial increase of 17.9% in mass transport coefficients.

  8. stochastic estimation of transmissivity fields conditioned to flow connectivity data

    Science.gov (United States)

    Freixas, Genis; Fernàndez-Garcia, Daniel; Sanchez-vila, Xavier

    2017-04-01

    Most methods for hydraulic parameter interpretation rely on a number of simplifications regarding the homogeneity of the underlying porous media. This way, the actual heterogeneity of any natural parameter, such as transmissivity, is transferred to the estimated in a way heavily dependent on the interpretation method used. An example is a pumping test, in most cases interpreted by means of the Cooper-Jacob method, which implicitly assumes a homogeneous isotropic confined aquifer. It was shown that the estimates obtained from this method when applied to a real site are not local values, but still have a physical meaning; the estimated transmissivity is equal to the effective transmissivity characteristic of the regional scale, while the log-ratio of the estimated storage coefficient with respect to the actual real value (assumed constant), indicated by , is an indicator of flow connectivity, representative of the scale given by the distance between the pumping and the observation wells. In this work we propose a methodology to use together with actual measurements of the log transmissivity at selected points to obtain a map of the best local transmissivity estimates using cokriging. Since the interpolation involves two variables measured at different support scales, a critical point is the estimation of the covariance and crosscovariance matrices, involving some quadratures that are obtained using some simplified approach. The method was applied to a synthetic field displaying statistical anisotropy, showing that the use of connectivity indicators mixed with the local values provide a better representation of the local value map, in particular regarding the enhanced representation of the continuity of structures corresponding to either high or low values.

  9. Decoding complex flow-field patterns in visual working memory.

    Science.gov (United States)

    Christophel, Thomas B; Haynes, John-Dylan

    2014-05-01

    There has been a long history of research on visual working memory. Whereas early studies have focused on the role of lateral prefrontal cortex in the storage of sensory information, this has been challenged by research in humans that has directly assessed the encoding of perceptual contents, pointing towards a role of visual and parietal regions during storage. In a previous study we used pattern classification to investigate the storage of complex visual color patterns across delay periods. This revealed coding of such contents in early visual and parietal brain regions. Here we aim to investigate whether the involvement of visual and parietal cortex is also observable for other types of complex, visuo-spatial pattern stimuli. Specifically, we used a combination of fMRI and multivariate classification to investigate the retention of complex flow-field stimuli defined by the spatial patterning of motion trajectories of random dots. Subjects were trained to memorize the precise spatial layout of these stimuli and to retain this information during an extended delay. We used a multivariate decoding approach to identify brain regions where spatial patterns of activity encoded the memorized stimuli. Content-specific memory signals were observable in motion sensitive visual area MT+ and in posterior parietal cortex that might encode spatial information in a modality independent manner. Interestingly, we also found information about the memorized visual stimulus in somatosensory cortex, suggesting a potential crossmodal contribution to memory. Our findings thus indicate that working memory storage of visual percepts might be distributed across unimodal, multimodal and even crossmodal brain regions. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Understanding Angiography-Based Aneurysm Flow Fields through Comparison with Computational Fluid Dynamics.

    Science.gov (United States)

    Cebral, J R; Mut, F; Chung, B J; Spelle, L; Moret, J; van Nijnatten, F; Ruijters, D

    2017-06-01

    Hemodynamics is thought to be an important factor for aneurysm progression and rupture. Our aim was to evaluate whether flow fields reconstructed from dynamic angiography data can be used to realistically represent the main flow structures in intracranial aneurysms. DSA-based flow reconstructions, obtained during interventional treatment, were compared qualitatively with flow fields obtained from patient-specific computational fluid dynamics models and quantitatively with projections of the computational fluid dynamics fields (by computing a directional similarity of the vector fields) in 15 cerebral aneurysms. The average similarity between the DSA and the projected computational fluid dynamics flow fields was 78% in the parent artery, while it was only 30% in the aneurysm region. Qualitatively, both the DSA and projected computational fluid dynamics flow fields captured the location of the inflow jet, the main vortex structure, the intrasaccular flow split, and the main rotation direction in approximately 60% of the cases. Several factors affect the reconstruction of 2D flow fields from dynamic angiography sequences. The most important factors are the 3-dimensionality of the intrasaccular flow patterns and inflow jets, the alignment of the main vortex structure with the line of sight, the overlapping of surrounding vessels, and possibly frame rate undersampling. Flow visualization with DSA from >1 projection is required for understanding of the 3D intrasaccular flow patterns. Although these DSA-based flow quantification techniques do not capture swirling or secondary flows in the parent artery, they still provide a good representation of the mean axial flow and the corresponding flow rate. © 2017 by American Journal of Neuroradiology.

  11. A study of flow field of feeder outlet pipe at CANDU for understanding flow accelerated(assistant) corrosion phenomena

    International Nuclear Information System (INIS)

    Kweon, H.; Seo, D. W.; Park, K. C.; Jeong, H. S.

    2002-01-01

    The FAC(Flow Accelerated Corrosion) on feeder outlet pipe is an important phenomena for surveying an integrity of CANDU plant. There are correlated a corrosion effect in electrochemistry and a flow field effect in hydrodynamics. A mass transfer rate is main governing parameter in macroscopic analysis of FAC phenomena. Therefore, first of all, at the hydrodynamic aspect the analysis of FAC is carried out. CFX 4.3 code calculates the flow field of feeder outlet pipe with complex geometry and the calculated results are estimated with an experimental data. On the basis of power plant data base, the worst location about wall thinning is compared with calculated and experimental location

  12. Controllability and observability of 2D thermal flow in bulk storage facilities using sensitivity fields

    NARCIS (Netherlands)

    Grubben, Nik L.M.; Keesman, Karel J.

    2017-01-01

    To control and observe spatially distributed thermal flow systems, the controllable field and observable field around the actuator and sensor are of interest, respectively. For spatially distributed systems, the classical systems theoretical concepts of controllability and observability are, in

  13. Research on Duct Flow Field Optimisation of a Robot Vacuum Cleaner

    Directory of Open Access Journals (Sweden)

    Xiao-bo Lai

    2011-11-01

    Full Text Available The duct of a robot vacuum cleaner is the length of the flow channel between the inlet of the rolling brush blower and the outlet of the vacuum blower. To cope with the pressure drop problem of the duct flow field in a robot vacuum cleaner, a method based on Pressure Implicit with Splitting of Operators (PRISO algorithm is introduced and the optimisation design of the duct flow field is implemented. Firstly, the duct structure in a robot vacuum cleaner is taken as a research object, with the computational fluid dynamics (CFD theories adopted; a three-dimensional fluid model of the duct is established by means of the FLUENT solver of the CFD software. Secondly, with the k-∊ turbulence model of three-dimensional incompressible fluid considered and the PRISO pressure modification algorithm employed, the flow field numerical simulations inside the duct of the robot vacuum cleaner are carried out. Then, the velocity vector plots on the arbitrary plane of the duct flow field are obtained. Finally, an investigation of the dynamic characteristics of the duct flow field is done and defects of the original duct flow field are analysed, the optimisation of the original flow field has then been conducted. Experimental results show that the duct flow field after optimisation can effectively reduce pressure drop, the feasibility as well as the correctness of the theoretical modelling and optimisation approaches are validated.

  14. Research on Duct Flow Field Optimisation of a Robot Vacuum Cleaner

    Directory of Open Access Journals (Sweden)

    Xiao-bo Lai

    2011-11-01

    Full Text Available The duct of a robot vacuum cleaner is the length of the flow channel between the inlet of the rolling brush blower and the outlet of the vacuum blower. To cope with the pressure drop problem of the duct flow field in a robot vacuum cleaner, a method based on Pressure Implicit with Splitting of Operators (PRISO algorithm is introduced and the optimisation design of the duct flow field is implemented. Firstly, the duct structure in a robot vacuum cleaner is taken as a research object, with the computational fluid dynamics (CFD theories adopted; a three‐dimensional fluid model of the duct is established by means of the FLUENT solver of the CFD software. Secondly, with the k‐ε turbulence model of three‐ dimensional incompressible fluid considered and the PRISO pressure modification algorithm employed, the flow field numerical simulations inside the duct of the robot vacuum cleaner are carried out. Then, the velocity vector plots on the arbitrary plane of the duct flow field are obtained. Finally, an investigation of the dynamic characteristics of the duct flow field is done and defects of the original duct flow field are analysed, the optimisation of the original flow field has then been conducted. Experimental results show that the duct flow field after optimisation can effectively reduce pressure drop, the feasibility as well as the correctness of the theoretical modelling and optimisation approaches are validated.

  15. The leading-edge vortex of swift-wing shaped delta wings

    Science.gov (United States)

    Muir, Rowan; Arredondo-Galeana, Abel; Viola, Ignazio Maria

    2017-11-01

    Recent investigations on the aerodynamics of natural fliers have illuminated the significance of the Leading-Edge Vortex (LEV) for lift generation in a variety of flight conditions. In this investigation, a model non-slender delta shaped wing with a sharp leading-edge is tested at low Reynolds Number, along with a delta wing of the same design, but with a modified trailing edge inspired by the wing of a common swift Apus apus. The effect of the tapering swift wing on LEV development and stability is compared with the flow structure over the un-modified delta wing model through particle image velocimetry. For the first time, a leading-edge vortex system consisting of a dual or triple LEV is recorded on a swift-wing shaped delta wing, where such a system is found across all tested conditions. It is shown that the spanwise location of LEV breakdown is governed by the local chord rather than Reynolds Number or angle of attack. These findings suggest that the trailing-edge geometry of the swift wing alone does not prevent the common swift from generating an LEV system comparable with that of a delta shaped wing. This work received funding from the Engineering and Physical Sciences Research Council [EP/M506515/1] and the Consejo Nacional de Ciencia y Tecnología (CONACYT).

  16. Numerical simulation of flow fields and particle trajectories

    DEFF Research Database (Denmark)

    Mayer, Stefan

    2000-01-01

    A model describing the ciliary driven flow and motion of suspended particles in downstream suspension feeders is developed. The quasi-steady Stokes equations for creeping flow are solved numerically in an unbounded fluid domain around cylindrical bodies using a boundary integral formulation. The ...

  17. Vorticity Transport on a Flexible Wing in Stall Flutter

    Science.gov (United States)

    Akkala, James; Buchholz, James; Farnsworth, John; McLaughlin, Thomas

    2014-11-01

    The circulation budget within dynamic stall vortices was investigated on a flexible NACA 0018 wing model of aspect ratio 6 undergoing stall flutter. The wing had an initial angle of attack of 6 degrees, Reynolds number of 1 . 5 ×105 and large-amplitude, primarily torsional, limit cycle oscillations were observed at a reduced frequency of k = πfc / U = 0 . 1 . Phase-locked stereo PIV measurements were obtained at multiple chordwise planes around the 62.5% and 75% spanwise locations to characterize the flow field within thin volumetric regions over the suction surface. Transient surface pressure measurements were used to estimate boundary vorticity flux. Recent analyses on plunging and rotating wings indicates that the magnitude of the pressure-gradient-driven boundary flux of secondary vorticity is a significant fraction of the magnitude of the convective flux from the separated leading-edge shear layer, suggesting that the secondary vorticity plays a significant role in regulating the strength of the primary vortex. This phenomenon is examined in the present case, and the physical mechanisms governing the growth and evolution of the dynamic stall vortices are explored. This work was supported by the Air Force Office of Scientific Research through the Flow Interactions and Control Program monitored by Dr. Douglas Smith, and through the 2014 AFOSR/ASEE Summer Faculty Fellowship Program (JA and JB).

  18. Stability of phospholipid vesicles studied by asymmetrical flow field-flow fractionation and capillary electrophoresis

    Energy Technology Data Exchange (ETDEWEB)

    Yohannes, Gebrenegus [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland); Pystynen, Kati-Henna [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland); Riekkola, Marja-Liisa [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland); Wiedmer, Susanne K. [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland)]. E-mail: susanne.wiedmer@helsinki.fi

    2006-02-23

    The stability of zwitterionic phosphatidylcholine vesicles in the presence of 20 mol% phosphatidyl serine (PS), phosphatidic acid (PA), phosphatidyl inositol (PI), and diacylphosphatidyl glycerol (PG) phospholipid vesicles, and cholesterol or calcium chloride was investigated by asymmetrical flow field-flow fractionation (AsFlFFF). Large unilamellar vesicles (LUV, diameter 100 nm) prepared by extrusion at 25 deg. C were used. Phospholipid vesicles (liposomes) were stored at +4 and -18 deg. C over an extended period of time. Extruded egg yolk phosphatidylcholine (EPC) particle diameters at peak maximum and mean measured by AsFlFFF were 101 {+-} 3 nm and 122 {+-} 5 nm, respectively. No significant change in diameter was observed after storage at +4 deg. C for about 5 months. When the storage period was extended to about 8 months (250 days) larger destabilized aggregates were formed (172 and 215 nm at peak maximum and mean diameters, respectively). When EPC was stored at -18 deg. C, large particles with diameters of 700-800 nm were formed as a result of dehydration, aggregation, and fusion processes. In the presence of calcium chloride, EPC alone did not form large aggregates. Addition of 20 mol% of negatively charged phospholipids (PS, PA, PI, or PG) to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) vesicles increased the electrostatic interactions between calcium ion and the vesicles and large aggregates were formed. In the presence of cholesterol, large aggregates of about 250-350 nm appeared during storage at +4 and -18 deg. C for more than 1 day. The effect of liposome storage temperature on phospholipid coatings applied in capillary electrophoresis (CE) was studied by measuring the electroosmotic flow (EOF). EPC coatings with and without cholesterol, PS, or calcium chloride, prepared from liposomes stored at +25, +4, and -18 deg. C, were studied at 25 deg. C. The performances of the coatings were further evaluated with three uncharged compounds

  19. How to Determine Losses in a Flow Field: A Paradigm Shifttowards the Second Law Analysis

    Directory of Open Access Journals (Sweden)

    Heinz Herwig

    2014-05-01

    Full Text Available Assuming that CFD solutions will be more and more used to characterizelosses in terms of drag for external flows and head loss for internal flows, we suggest toreplace single-valued data, like the drag force or a pressure drop, by field information aboutthe losses. These information are gained when the entropy generation in the flow field isanalyzed, an approach that often is called second law analysis (SLA, referring to the secondlaw of thermodynamics. We show that this SLA approach is straight-forward, systematicand helpful when it comes to the physical interpretation of the losses in a flow field. Variousexamples are given, including external and internal flows, two phase flow, compressible flowand unsteady flow. Finally, we show that an energy transfer within a certain process can beput into a broader perspective by introducing the entropic potential of an energy.

  20. Internal Flow Field Uniformity Study of Dust Collector for A Street Vacuum Sweeper Based on CFD

    Science.gov (United States)

    Xi, Yuan; Dai, Yan; Xiao, Yonghou; Cheng, Kai; Xiao, Tao; Zhao, Shixiang

    2017-12-01

    Internal flow field of dust collector for a street vacuum is studied by Computational Fluid Dynamics (CFD). The causes of uneven distribution of flow field were diagnosed by simulation, and an improvement measure was put forward. The result shows that flow ratce distribution of dust collector is uneven, the reason for which is the higher wind velocity at the Inlet. A baffle plate was added at the Inlet to improve the uniformity of internal flow field. The main technical parameters, maximum flow rate uneven amplitude Δk i and overall flow rate uneven amplitude Δ \\bar{{k}i} and overall flow rate uneven amplitude, are decreased in this way. Δk is reduced from 0.3429 to 0.1308. While Δ \\bar{{k}i} is reduced from 0.1012 to 0.0402.

  1. Extended SO2 outgassing from the 2014-2015 Holuhraun lava flow field, Iceland

    Science.gov (United States)

    Simmons, Isla C.; Pfeffer, Melissa A.; Calder, Eliza S.; Galle, Bo; Arellano, Santiago; Coppola, Diego; Barsotti, Sara

    2017-11-01

    The 2014-2015 Holuhraun eruption was the largest fissure eruption in Iceland in the last 200 years. This flood basalt eruption produced 1.6 km3 of lava, forming a lava flow field covering an area of 84 km2. Over the 6-month course of the eruption, 11 Mt of SO2 were released from the eruptive vents as well as from the cooling lava flow field. This work examines the post-eruption SO2 flux emitted by the Holuhraun lava flow field, providing the first study of the extent and relative importance of the outgassing of a lava flow field after emplacement. We use data from a scanning differential optical absorption spectroscopy (DOAS) instrument installed at the eruption site to monitor the flux of SO2. In this study, we propose a new method to estimate the SO2 emissions from the lava flow field, based on the characteristic shape of the scanned column density distribution of a homogenous source close to the ground. Post-eruption outgassing of the lava flow field continued for at least 3 months after the end of the eruption, with SO2 flux between < 1 and 9 kg/s. The lava flow field post-eruption emissions were not a significant contributor to the total SO2 released during the eruption; however, the lava flow field was still an important polluter and caused high concentrations of SO2 at ground level after lava effusion ceased.

  2. Analytical scale purification of zirconia colloidal suspension using field programmed sedimentation field flow fractionation.

    Science.gov (United States)

    Van-Quynh, Alexandra; Blanchart, Philippe; Battu, Serge; Clédat, Dominique; Cardot, Philippe

    2006-03-03

    Sedimentation field flow fractionation was used to obtain purified fractions from a polydispersed zirconia colloidal suspension in the potential purpose of optical material hybrid coating. The zirconia particle size ranged from 50/70 nm to 1000 nm. It exhibited a log-Gaussian particle size distribution (in mass or volume) and a 115% polydispersity index (P.I.). Time dependent eluted fractions of the original zirconia colloidal suspension were collected. The particle size distribution of each fraction was determined with scanning electron microscopy and Coulter sub-micron particle sizer (CSPS). These orthogonal techniques generated similar data. From fraction average elution times and granulometry measurements, it was shown that zirconia colloids are eluted according to the Brownian elution mode. The four collected fractions have a Gaussian like distribution and respective average size and polydispersity index of 153 nm (P.I. = 34.7%); 188 nm (P.I. = 27.9%); 228 nm (P.I. = 22.6%), and 276 nm (P.I. = 22.3%). These data demonstrate the strong size selectivity of SdFFF operated with programmed field of exponential profile for sorting particles in the sub-micron range. Using this technique, the analytical production of zirconia of given average size and reduced polydispersity is possible.

  3. Numerical simulation of electro-magnetic and flow fields of TiAl melt under electric field

    Directory of Open Access Journals (Sweden)

    Zhang Yong

    2010-08-01

    Full Text Available This article aims at building an electromagnetic and fluid model, based on the Maxwell equations and Navier-Stokes equations, in TiAl melt under two electric fields. FEM (Finite Element Method and APDL (ANSYS Parametric Design Language were employed to perform the simulation, model setup, loading and problem solving. The melt in molds of same cross section area with different flakiness ratio (i.e. width/depth under the load of sinusoidal current or pulse current was analyzed to obtain the distribution of electromagnetic field and flow field. The results show that the induced magnetic field occupies sufficiently the domain of the melt in the mold with a flakiness ratio of 5:1. The melt is driven bipolarly from the center in each electric field. It is also found that the pulse electric field actuates the TiAl melt to flow stronger than what the sinusoidal electric field does.

  4. Distribution of Zelus longipes (Hemiptera: Reduviidae) in south Florida corn fields and its functional response to corn-infesting picture-winged flies (Diptera: Ulidiidae).

    Science.gov (United States)

    Kalsi, M; Seal, D R; Nuessly, G S; Capinera, J L; Martin, C G

    2014-10-01

    The milkweed assassin bug, Zelus longipes (L.) (Hemiptera: Reduviidae), is a generalist predator and a potential biological control agent of picture-winged flies (Diptera: Ulidiidae), which cause considerable economic damage to sweet corn yields in Florida. We studied the potential of Z. longipes as a biocontrol agent of four ulidiid pests in corn fields: Euxesta stigmatias Loew, Euxesta eluta Loew, Euxesta annonae F., and Chaetopsis massyla Walker. Within-plant and within-field distributions of Z. longipes and ulidiids and functional responses of Z. longipes to ulidiid prey were determined. Highest numbers of Z. longipes and ulidiids in the R1, R2, and R3 corn stages were generally in the basal or middle leaves at 09:00 h EST, ears at 13:00 h EST, and top and tassel at 17:00 h EST. Hence, there seemed to be a coordinated migration of Z. longipes and ulidiids from the lowest to the highest parts of the corn plant during the day. Within the corn field, aggregated (clumped) distributions were most common for Z. longipes and ulidiids especially in the later R2 and R3 stages based on Taylor's power law, Iwao's patchiness regression, index of dispersion, and Lloyd's patchiness indices of dispersion. However, predator and prey populations were lower in the R1 stage, and there were inconsistent results for dispersion indices among times of day and between predators and prey. Ulidiid distributions in R1 were mostly regular (uniform) at 13:00 h EST, but aggregated at 09:00 h and 17:00 h. However, Z. longipes R1 distributions were mostly aggregated at 13:00 h, but random or regular at 09:00 h and 17:00 h EST. Handling times for male and female Z. longipes were 1.0-1.39 h and 0.67-0.97 h, respectively, and each had a type II functional response to E. stigmatias, E. eluta, and E. annonae and consumed about five flies per day. Although the population abundance of Z. longipes can vary between seasons, it appears to be a promising biocontrol agent of ulidiid flies in corn.

  5. Effects of wing/elevon gap sealing flapper doors on orbiter elevon effectiveness of model 16-0 in the NAAL 7.75 by 11 foot continuous flow wind tunnel (OA119A)

    Science.gov (United States)

    Mennell, R.

    1974-01-01

    Space shuttle orbiter elevon effectiveness was measured with the 6 inch elevon/elevon and elevon/fuselage gaps and various configurations of wing/elevon upper hingeline gap sealing flapper doors. The elevon configuration parametric variations consisted of sealing the lower hingeline to prevent flow-through and testing a long chord flapper door, a short chord flapper door, no flapper door (elevon/wing gap upper hingeline completely open), and a completely sealed elevon at elevon deflections from +20 deg to -40 deg. Preliminary data analysis indicates loss of elevon effectiveness at deflections more negative than -20 deg, and little or no effect of flapper door configuration on elevon effectiveness. Flow visualization photographs taken at alpha = 15 deg for two flapper door configurations substantiated the force data results. Aerodynamic force and moment data were measured in the body axis by a 2.5 inch task type internal strain gage balance. The model was sting supported through the base region with a nominal angle of attack range of -10 deg less than or equal to alpha less than or equal to 24 deg at a model angle of sideslip of Beta equal to 0 deg.

  6. Core flow control system for field applications; Sistema de controle de core-flow

    Energy Technology Data Exchange (ETDEWEB)

    Granzotto, Desiree G.; Adachi, Vanessa Y.; Bannwart, Antonio C.; Moura, Luiz F.M. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil); Sassim, Natache S.D.A. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Centro de Estudo do Petroleo (CEPETRO); Carvalho, Carlos H.M. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

    2008-07-01

    The significant heavy oil reserves worldwide and the presently high crude oil prices make it essential the development of technologies for heavy oil production and transportation. Heavy oils, with their inherent features of high viscosity (100- 10,000 cP) and density (below 20 deg API) require specific techniques to make it viable their flow in pipes at high flow rates. One of the simplest methods, which do not require use of heat or diluents, is provided by oil-water annular flow (core-flow). Among the still unsolved issues regarding core-flow is the two-phase flow control in order to avoid abrupt increases in the pressure drop due to the possible occurrence of bad water-lubricated points, and thus obtain a safe operation of the line at the lowest possible water-oil ratio. This work presents results of core flow tests which allow designing a control system for the inlet pressure of the line, by actuating on the water flow rate at a fixed oil flow rate. With the circuit model and the specified controller, simulations can be done to assess its performance. The experiments were run at core-flow circuit of LABPETRO-UNICAMP. (author)

  7. Insights from field observations into controls on flow front speed in submarine sediment flows

    Science.gov (United States)

    Heerema, C.; Talling, P.; Cartigny, M.; Paull, C. K.; Gwiazda, R.; Clare, M. A.; Parsons, D. R.; Xu, J.; Simmons, S.; Maier, K. L.; Chapplow, N.; Gales, J. A.; McGann, M.; Barry, J.; Lundsten, E. M.; Anderson, K.; O'Reilly, T. C.; Rosenberger, K. J.; Sumner, E. J.; Stacey, C.

    2017-12-01

    Seafloor avalanches of sediment called turbidity currents are one of the most important processes for moving sediment across our planet. Only rivers carry comparable amounts of sediment across such large areas. Here we present some of the first detailed monitoring of these underwater flows that is being undertaken at a series of test sites. We seek to understand the factors that determine flow front speed, and how that speed varies with distance. This frontal speed is particularly important for predicting flow runout, and how the power of these hazardous flows varies with distance. First, we consider unusually detailed measurements of flow front speed defined by transit times between moorings and other tracked objects placed on the floor of Monterey Canyon offshore California in 2016-17. These measurements are then compared to flow front speeds measured using multiple moorings in Bute Inlet, British Columbia in 2016; and by cable breaks in Gaoping Canyon offshore Taiwan in 2006 and 2009. We seek to understand how flow front velocity is related to seafloor gradient, flow front thickness and density. It appears that the spatial evolution of frontal speed is similar in multiple flows, although their peak frontal velocities vary. Flow front velocity tends to increase rapidly initially before declining rather gradually over tens or even hundreds of kilometres. It has been proposed that submarine flows will exist in one of two states; either eroding and accelerating, or depositing sediment and dissipating. We conclude by discussing the implications of this global compilation of flow front velocities for understanding submarine flow behaviour.

  8. Asymmetrical flow field-flow fractionation with on-line detection for drug transfer studies: a feasibility study

    DEFF Research Database (Denmark)

    Hinna, A.; Steiniger, F.; Hupfeld, S.

    2014-01-01

    Knowledge about drug retention within colloidal carriers is of uppermost importance particularly if drug targeting is anticipated. The aim of the present study was to evaluate asymmetrical flow field-flow fractionation (AF4) with on-line UV/VIS drug quantification for its suitability to determine......-line absorbance measurements was found feasible for the chosen model drug, but careful (re-) evaluation of turbidity effects is crucial for other drug and carrier combinations....

  9. Fractionating power and outlet stream polydispersity in asymmetrical flow field-flow fractionation. Part II: programmed operation.

    Science.gov (United States)

    Williams, P Stephen

    2017-01-01

    Asymmetrical flow field-flow fractionation (As-FlFFF) is a widely used technique for analyzing polydisperse nanoparticle and macromolecular samples. The programmed decay of cross flow rate is often employed. The interdependence of the cross flow rate through the membrane and the fluid flow along the channel length complicates the prediction of elution time and fractionating power. The theory for their calculation is presented. It is also confirmed for examples of exponential decay of cross flow rate with constant channel outlet flow rate that the residual sample polydispersity at the channel outlet is quite well approximated by the reciprocal of four times the fractionating power. Residual polydispersity is of importance when online MALS or DLS detection are used to extract quantitative information on particle size or molecular weight. The theory presented here provides a firm basis for the optimization of programmed flow conditions in As-FlFFF. Graphical abstract Channel outlet polydispersity remains significant following fractionation by As-FlFFF under conditions of programmed decay of cross flow rate.

  10. The leading-edge vortex of swift wing-shaped delta wings.

    Science.gov (United States)

    Muir, Rowan Eveline; Arredondo-Galeana, Abel; Viola, Ignazio Maria

    2017-08-01

    Recent investigations on the aerodynamics of natural fliers have illuminated the significance of the leading-edge vortex (LEV) for lift generation in a variety of flight conditions. A well-documented example of an LEV is that generated by aircraft with highly swept, delta-shaped wings. While the wing aerodynamics of a manoeuvring aircraft, a bird gliding and a bird in flapping flight vary significantly, it is believed that this existing knowledge can serve to add understanding to the complex aerodynamics of natural fliers. In this investigation, a model non-slender delta-shaped wing with a sharp leading edge is tested at low Reynolds number, along with a delta wing of the same design, but with a modified trailing edge inspired by the wing of a common swift Apus apus . The effect of the tapering swift wing on LEV development and stability is compared with the flow structure over the unmodified delta wing model through particle image velocimetry. For the first time, a leading-edge vortex system consisting of a dual or triple LEV is recorded on a swift wing-shaped delta wing, where such a system is found across all tested conditions. It is shown that the spanwise location of LEV breakdown is governed by the local chord rather than Reynolds number or angle of attack. These findings suggest that the trailing-edge geometry of the swift wing alone does not prevent the common swift from generating an LEV system comparable with that of a delta-shaped wing.

  11. A numerical model to evaluate the flow distribution in a large solar collector field

    DEFF Research Database (Denmark)

    Bava, Federico; Dragsted, Janne; Furbo, Simon

    2017-01-01

    This study presents a numerical model to evaluate the flow distribution in a large solar collector field, with solar collectors connected both in series and in parallel. The boundary conditions of the systems, such as flow rate, temperature, fluid type and layout of the collector field can...... be easily changed in the model. The model was developed in Matlab and the calculated pressure drop and flow distribution were compared with measurements from a solar collector field. A good agreement between model and measurements was found. The model was then used to study the flow distribution...... in different conditions. Balancing valves proved to be an effective way to achieve uniform flow distribution also in conditions different from those for which the valves were regulated. For small solar collector fields with limited number of collector rows connected in parallel, balancing valves...

  12. Experimental Investigation of Scalar Patterns in a Spatially Periodic Flow Field

    Science.gov (United States)

    Rajaei, Hadi; Baskan, Ozge; Speetjens, Michel; Clercx, Herman

    2013-11-01

    Spatially persisting patterns that form during the downstream evolution of passive scalars in three-dimensional (3D) spatially periodic flow fields is a fundamental aspect of industrial mixing processes that rely on the static mixing principle. Despite many numerical studies on 3D spatially periodic flow fields, a comprehensive experimental research on the periodic flow field is still scarce. This research focuses on a comparative analysis between laboratory experiments and numerical simulations on the evolution of the periodic flow field and coherent flow structures and concerns the effect of boundary (i.e. inlet) conditions on the periodicity of the flow field in a representative inline mixer consisting of spatially periodic internal elements. The experimental setup is composed of an optically accessible vertical test section with transparent internal elements which is fed by a pressure-driven pipe flow containing tracer particles. The 3D streamlines, hence, the flow field, are measured by 3D Particle-Tracking Velocimetry technique. The streamwise development of the periodicity within few internal elements regardless of the inlet conditions has been proven by preliminary studies.

  13. THE EFFECT OF MAGNETIC FIELD ON MEAN FLOW GENERATION BY ROTATING TWO-DIMENSIONAL CONVECTION

    Energy Technology Data Exchange (ETDEWEB)

    Currie, Laura K., E-mail: lcurrie@astro.ex.ac.uk [Department of Physics and Astronomy, University of Exeter, Stocker Road, EX4 4QL Exeter (United Kingdom)

    2016-11-20

    Motivated by the significant interaction of convection, rotation, and magnetic field in many astrophysical objects, we investigate the interplay between large-scale flows driven by rotating convection and an imposed magnetic field. We utilize a simple model in two dimensions comprised of a plane layer that is rotating about an axis inclined to gravity. It is known that this setup can result in strong mean flows; we numerically examine the effect of an imposed horizontal magnetic field on such flows. We show that increasing the field strength in general suppresses the time-dependent mean flows, but in some cases it organizes them, leading to stronger time-averaged flows. Furthermore, we discuss the effect of the field on the correlations responsible for driving the flows and the competition between Reynolds and Maxwell stresses. A change in behavior is observed when the (fluid and magnetic) Prandtl numbers are decreased. In the smaller Prandtl number regime, it is shown that significant mean flows can persist even when the quenching of the overall flow velocity by the field is relatively strong.

  14. Experimental Measurement of the Flow Field of Heavy Trucks

    Energy Technology Data Exchange (ETDEWEB)

    Fred Browand; Charles Radovich

    2005-05-31

    Flat flaps that enclose the trailer base on the sides and top are known to reduce truck drag and reduce fuel consumption. Such flapped-truck geometries have been studied in laboratory wind tunnels and in field tests. A recent review of wind tunnel data for a variety of truck geometries and flow Reynolds numbers show roughly similar values of peak drag reduction, but differ in the determination of the optimum flap angle. Optimum angles lie in the range 12 degrees-20 degrees, and may be sensitive to Reynolds number and truck geometry. The present field test is undertaken to provide additional estimates of the magnitude of the savings to be expected on a typical truck for five flap angles 10, 13, 16, 19, and 22 degrees. The flaps are constructed from a fiberglass-epoxy-matrix material and are one-quarter of the base width in length (about 61 cm, or 2 feet). They are attached along the rear door hinge lines on either side of the trailer, so that no gap appears at the joint between the flap and the side of the trailer The flap angle is adjusted by means of two aluminum supports. The present test is performed on the NASA Crows Landing Flight Facility at the northern end of the San Joaquin valley in California. The main runway is approximately 2400 meters in length, and is aligned approximately in a north-south direction The test procedure is to make a series of runs starting at either end of the runway. All runs are initiated under computer control to accelerate the truck to a target speed of 60 mph (96 6 km/hr), to proceed at the target speed for a fixed distance, and to decelerate at the far end of the runway. During a run, the broadcast fuel rate, the engine rpm, forward speed, elapsed time--as well as several other parameters (10 in all)--are digitized at a rate of 100 digitizations per second. Various flapped-conditions are interspersed with the ''no flaps'' control, and are sequenced in a different order on different days. Approximately 310 runs

  15. Algebraic structure of general electromagnetic fields and energy flow

    International Nuclear Information System (INIS)

    Hacyan, Shahen

    2011-01-01

    Highlights: → Algebraic structure of general electromagnetic fields in stationary spacetime. → Eigenvalues and eigenvectors of the electomagnetic field tensor. → Energy-momentum in terms of eigenvectors and Killing vector. → Explicit form of reference frame with vanishing Poynting vector. → Application of formalism to Bessel beams. - Abstract: The algebraic structures of a general electromagnetic field and its energy-momentum tensor in a stationary space-time are analyzed. The explicit form of the reference frame in which the energy of the field appears at rest is obtained in terms of the eigenvectors of the electromagnetic tensor and the existing Killing vector. The case of a stationary electromagnetic field is also studied and a comparison is made with the standard short-wave approximation. The results can be applied to the general case of a structured light beams, in flat or curved spaces. Bessel beams are worked out as example.

  16. The gas heterogeneous flows cleaning technology from corona discharge field

    Science.gov (United States)

    Bogdanov, A.; Tokarev, A.; Judanov, V.; Vinogradov, V.

    2017-11-01

    A nanogold capture and extraction from combustion products of Kara-Keche coal, description the process: a coal preparation to experiments, nanogold introducing in its composition, temperature and time performance of combustion, device and function of experimental apparatus, gas-purification of the gas flow process and receiving combustion products (condensate, coke, ash, rags) is offerred.

  17. Discharge characteristics in inhomogeneous fields under air flow

    DEFF Research Database (Denmark)

    Vogel, Stephan; Holbøll, Joachim

    2017-01-01

    was connected to a variable DC potential of up to 100kV over a grounded plate in order to trigger different corona modes. The impact of the air flow on the space charges created in the vicinity of the electrode is evaluated by means of PD measurements in time domain. The results indicate that the wind increases...

  18. Flow field development in a direct injection diesel engine with ...

    African Journals Online (AJOL)

    The flow characteristics of these engine manifolds are examined under transient conditions using Computational Fluid Dynamics (CFD) code STAR-CD. The predicted CFD results of mean swirl velocity of the engine at different locations inside the combustion chamber at the end of compression stroke are compared with ...

  19. Spatial statistics of magnetic field in two-dimensional chaotic flow in the resistive growth stage

    Energy Technology Data Exchange (ETDEWEB)

    Kolokolov, I.V., E-mail: igor.kolokolov@gmail.com [Landau Institute for Theoretical Physics RAS, 119334, Kosygina 2, Moscow (Russian Federation); NRU Higher School of Economics, 101000, Myasnitskaya 20, Moscow (Russian Federation)

    2017-03-18

    The correlation tensors of magnetic field in a two-dimensional chaotic flow of conducting fluid are studied. It is shown that there is a stage of resistive evolution where the field correlators grow exponentially with time. The two- and four-point field correlation tensors are computed explicitly in this stage in the framework of Batchelor–Kraichnan–Kazantsev model. They demonstrate strong temporal intermittency of the field fluctuations and high level of non-Gaussianity in spatial field distribution.

  20. Effects of wall conditions on flow field in a circular micro-channel

    International Nuclear Information System (INIS)

    Zhou, Hao; Cai, Guobiao; He, Bijiao

    2016-01-01

    Highlights: • TMAC rather than NMAC has great influence on the flow field in circular microchannel. • The flow field is greatly influenced by the velocity stages in vicinity of the wall. • Effect of wall roughness on flow field is much greater than that of wall material. - Abstract: Effects of a gas-surface interaction model, the Cercignani-Lampise-Lord model, on primary fluid properties in a circular micro-channel are investigated in this paper. The tangential momentum accommodation coefficient (TMAC) has a significant influence on the flow field in the micro-channel. However, the variation of the flow field with the normal momentum accommodation coefficient is not as significant as that with the TMAC. The fundamental mechanism behind the change of flow field is revealed. Moreover, it is found that the effect of the wall roughness on the flow field is much greater than that of the wall material. When the wall roughness varies, the mass flux of the ring section region between the half radius and the radius changes a lot while the rest remains unchanged. However, the heat flux over the cross section remains almost unchanged with the variation of the wall material when the wall is rough.

  1. Lift, drag and flow-field measurements around a small ornithopter

    Energy Technology Data Exchange (ETDEWEB)

    Balakumar, B J [Los Alamos National Laboratory; Chavez - Alarcon, Ramiro [NMSU; Shu, Fangjun [NMSU

    2011-01-12

    The aerodynamics of a flight-worthy, radio controlled ornithopter is investigated using a combination of Particle-Image Velocimetry (PIV), load cell measurements, and high-speed photography of smoke visualizations. The lift and thrust forces of the ornithopter are measured at various flow speeds, flapping frequencies and angles of attack to characterize the flight performance. These direct force measurements are then compared with forces estimated using control volume analysis on PIV data. High-speed photography of smoke streaks is used to visualize the evolution of leading edge vortices, and to qualitatively infer the effect of wing deformation on the net downwash. Vortical structures in the wake are compared to previous studies on root flapping, and direct measurements of flapping efficiency are used to argue that the current ornithopter operates sub-optimally in converting the input energy into propulsive work.

  2. Estimation of local and regional components of drain - flow from an irrigated field

    International Nuclear Information System (INIS)

    Eching, S.O.; Hopmans, J.W.; Wallender, W.W.; Macyntyre, J.L.; Peters, D.

    1995-01-01

    The contribution of regional ground water and deep percolation from a furrow irrigated field to total drain flow was estimated using salt load analysis. It was found that 64% of the drain flow comes from regional ground water flow. The electrical conductivity of the drain water was highly correlated with the drain flow rate. From the field water balance with deep percolation as estimated from the salt load analysis, using yield function derived evapotranspiration, and measured changes in root zone water storage, it was shown that 14% of the crop evapotranspiration comes from ground water during the study period. 8 figs; 5 tabs; 15 refs ( Author )

  3. Pollen- and seed-mediated transgene flow in commercial cotton seed production fields.

    Directory of Open Access Journals (Sweden)

    Shannon Heuberger

    Full Text Available BACKGROUND: Characterizing the spatial patterns of gene flow from transgenic crops is challenging, making it difficult to design containment strategies for markets that regulate the adventitious presence of transgenes. Insecticidal Bacillus thuringiensis (Bt cotton is planted on millions of hectares annually and is a potential source of transgene flow. METHODOLOGY/PRINCIPAL FINDINGS: Here we monitored 15 non-Bt cotton (Gossypium hirsutum, L. seed production fields (some transgenic for herbicide resistance, some not for gene flow of the Bt cotton cry1Ac transgene. We investigated seed-mediated gene flow, which yields adventitious Bt cotton plants, and pollen-mediated gene flow, which generates outcrossed seeds. A spatially-explicit statistical analysis was used to quantify the effects of nearby Bt and non-Bt cotton fields at various spatial scales, along with the effects of pollinator abundance and adventitious Bt plants in fields, on pollen-mediated gene flow. Adventitious Bt cotton plants, resulting from seed bags and planting error, comprised over 15% of plants sampled from the edges of three seed production fields. In contrast, pollen-mediated gene flow affected less than 1% of the seed sampled from field edges. Variation in outcrossing was better explained by the area of Bt cotton fields within 750 m of the seed production fields than by the area of Bt cotton within larger or smaller spatial scales. Variation in outcrossing was also positively associated with the abundance of honey bees. CONCLUSIONS/SIGNIFICANCE: A comparison of statistical methods showed that our spatially-explicit analysis was more powerful for understanding the effects of surrounding fields than customary models based on distance. Given the low rates of pollen-mediated gene flow observed in this study, we conclude that careful planting and screening of seeds could be more important than field spacing for limiting gene flow.

  4. Analysis of magnetic nanoparticles using quadrupole magnetic field-flow fractionation

    International Nuclear Information System (INIS)

    Carpino, Francesca; Moore, Lee R.; Zborowski, Maciej; Chalmers, Jeffrey J.; Williams, P. Stephen

    2005-01-01

    The new technique of quadrupole magnetic field-flow fractionation is described. It is a separation and characterization technique for particulate magnetic materials. Components of a sample are eluted from the separation channel at times dependent on the strength of their interaction with the magnetic field. A quadrupole electromagnet allows a programmed reduction of field strength during analysis of polydisperse samples

  5. Three-dimensional vortex wake structure of flapping wings in hovering flight.

    Science.gov (United States)

    Cheng, Bo; Roll, Jesse; Liu, Yun; Troolin, Daniel R; Deng, Xinyan

    2014-02-06

    Flapping wings continuously create and send vortices into their wake, while imparting downward momentum into the surrounding fluid. However, experimental studies concerning the details of the three-dimensional vorticity distribution and evolution in the far wake are limited. In this study, the three-dimensional vortex wake structure in both the near and far field of a dynamically scaled flapping wing was investigated experimentally, using volumetric three-component velocimetry. A single wing, with shape and kinematics similar to those of a fruitfly, was examined. The overall result of the wing action is to create an integrated vortex structure consisting of a tip vortex (TV), trailing-edge shear layer (TESL) and leading-edge vortex. The TESL rolls up into a root vortex (RV) as it is shed from the wing, and together with the TV, contracts radially and stretches tangentially in the downstream wake. The downwash is distributed in an arc-shaped region enclosed by the stretched tangential vorticity of the TVs and the RVs. A closed vortex ring structure is not observed in the current study owing to the lack of well-established starting and stopping vortex structures that smoothly connect the TV and RV. An evaluation of the vorticity transport equation shows that both the TV and the RV undergo vortex stretching while convecting downwards: a three-dimensional phenomenon in rotating flows. It also confirms that convection and secondary tilting and stretching effects dominate the evolution of vorticity.

  6. Three dimensional numerical simulation for air flow field in melt blowing

    Science.gov (United States)

    Xie, Sheng; Han, Wanli; Jiang, Guojun

    2017-10-01

    Melt blowing is one-step approach for producing microfibrous nonwovens. In this study, the characteristics of air flow field in different die melt blowing were studied. CFD simulation analysis was adopted to complete the air flow field simulation. The characteristics of the air flow fields in different die melt blowing were revealed and compared. Meanwhile, the fiber paths in these two melt-blowing processes are recorded with a high-speed camera. The fiber path profiles, especially the whipping, are obtained and presented.

  7. Surface and Flow Field Measurements on the FAITH Hill Model

    Science.gov (United States)

    Bell, James H.; Heineck, James T.; Zilliac, Gregory; Mehta, Rabindra D.; Long, Kurtis R.

    2012-01-01

    A series of experimental tests, using both qualitative and quantitative techniques, were conducted to characterize both surface and off-surface flow characteristics of an axisymmetric, modified-cosine-shaped, wall-mounted hill named "FAITH" (Fundamental Aero Investigates The Hill). Two separate models were employed: a 6" high, 18" base diameter machined aluminum model that was used for wind tunnel tests and a smaller scale (2" high, 6" base diameter) sintered nylon version that was used in the water channel facility. Wind tunnel and water channel tests were conducted at mean test section speeds of 165 fps (Reynolds Number based on height = 500,000) and 0.1 fps (Reynolds Number of 1000), respectively. The ratio of model height to boundary later height was approximately 3 for both tests. Qualitative techniques that were employed to characterize the complex flow included surface oil flow visualization for the wind tunnel tests, and dye injection for the water channel tests. Quantitative techniques that were employed to characterize the flow included Cobra Probe to determine point-wise steady and unsteady 3D velocities, Particle Image Velocimetry (PIV) to determine 3D velocities and turbulence statistics along specified planes, Pressure Sensitive Paint (PSP) to determine mean surface pressures, and Fringe Imaging Skin Friction (FISF) to determine surface skin friction (magnitude and direction). This initial report summarizes the experimental set-up, techniques used, data acquired and describes some details of the dataset that is being constructed for use by other researchers, especially the CFD community. Subsequent reports will discuss the data and their interpretation in more detail

  8. Comparison of Inflation Processes at the 1859 Mauna Loa Flow, HI, and the McCartys Flow Field, NM

    Science.gov (United States)

    Bleacher, Jacob E.; Garry, W. Brent; Zimbelman, James R.; Crumpler, Larry S.

    2012-01-01

    Basaltic lavas typically form channels or tubes during flow emplacement. However, the importance of sheet flow in the development of basalt ic terrains received recognition over the last 15 years. George Walke r?s research on the 1859 Mauna Loa Flow was published posthumously in 2009. In this paper he discusses the concept of endogenous growth, or inflation, for the distal portion of this otherwise channeldominated lava flow. We used this work as a guide when visiting the 1859 flow to help us better interpret the inflation history of the McCartys flow field in NM. Both well preserved flows display similar clues about the process of inflation. The McCartys lava flow field is among the you ngest (approx.3000 yrs) basaltic lava flows in the continental United States. It was emplaced over slopes of topographic plateaus and depressions. Some depressions display level floors with surfaces as described above, while some are bowl shaped with floors covered in broken lava slabs. Th e boundaries between plateaus and depressions are also typically smoo th, grooved surfaces that have been tilted to angles sometimes approaching vertical. The upper margin of these tilted surfaces displays lar ge cracks, sometimes containing squeeze-ups. The bottom boundary with smooth floored depressions typically shows embayment by younger lavas. It appears that this style of terrain represents the emplacement of an extensive sheet that experiences inflation episodes within prefer red regions where lateral spreading of the sheet is inhibited, thereby forming plateaus. Depressions are often the result of non-inflation and can be clearly identified by lateral squeeze-outs along the pit walls that form when the rising crust exposes the still liquid core of the sheet. Our current efforts are focused on.

  9. The Interaction of Focused Attention with Flow-field Sensitivity

    Science.gov (United States)

    Stoffregen, T.

    1984-01-01

    Two studies were performed to determine whether a subject's response to naturalistic optical flow specifying egomotion would be affected by a concurrent attention task. In the first study subjects stood in a moving room in which various areas of the optical flow generated by room movement were visible. Subjects responded to room motion with strong compensatory sway when the entire room was visible. When the side walls of the room were completely obscured by stationary screens, leaving only the front wall visible, sway was significantly reduced, though it remained greater than in an eyes-closed control. In Exp. 2 subjects were presented with either the full room (large sway response) or the room with only the front wall visible (moderate response), each in combination with either a hard or easy verbal addition task. Preliminary results show that swaying in the fully visible room and in the room with only the front wall visible increased when combined with either the hard or easy tasks. These preliminary results suggest that at the least the pick-up of optical flow specifying egomotion is not affected by concurrent attentional activity.

  10. Semi-automated quantitative Drosophila wings measurements.

    Science.gov (United States)

    Loh, Sheng Yang Michael; Ogawa, Yoshitaka; Kawana, Sara; Tamura, Koichiro; Lee, Hwee Kuan

    2017-06-28

    Drosophila melanogaster is an important organism used in many fields of biological research such as genetics and developmental biology. Drosophila wings have been widely used to study the genetics of development, morphometrics and evolution. Therefore there is much interest in quantifying wing structures of Drosophila. Advancement in technology has increased the ease in which images of Drosophila can be acquired. However such studies have been limited by the slow and tedious process of acquiring phenotypic data. We have developed a system that automatically detects and measures key points and vein segments on a Drosophila wing. Key points are detected by performing image transformations and template matching on Drosophila wing images while vein segments are detected using an Active Contour algorithm. The accuracy of our key point detection was compared against key point annotations of users. We also performed key point detection using different training data sets of Drosophila wing images. We compared our software with an existing automated image analysis system for Drosophila wings and showed that our system performs better than the state of the art. Vein segments were manually measured and compared against the measurements obtained from our system. Our system was able to detect specific key points and vein segments from Drosophila wing images with high accuracy.

  11. Field implementation of Particle Image Velocimetry (PIV) for studying flow dynamics at river confluences

    Science.gov (United States)

    Lewis, Q. W.; Rhoads, B. L.

    2014-12-01

    The complex hydrodynamics of river confluences have been the focus of numerous investigations over the past several decades. Confluences are locations in river systems characterized by complex patterns of turbulent flow structure, especially within the mixing interface that develops between the two flows. To date, most field investigations of flow structure at stream confluences have been based on point measurements of velocity time series (e.g using ADVs) or on time-averaged data with high spatial resolution, but poor temporal resolution (e.g. using ADCPs). Past approaches have failed to capture the spatial and temporal density of velocity measurements needed to adequately characterize complex turbulent flow structures. In contrast, Particle Image Velocimetry (PIV) has been used successfully in laboratory studies to define in considerable detail the characteristics of turbulent structures. This study uses field-based PIV to characterize surficial flow structure within a small stream confluence. Landscape mulch served as seeding material for the PIV. Particle motion was recorded at a high frame rate using a small action camera mounted above the surface of the flow. Near-surface 3D velocities of flow were measured with an acoustic Doppler velocimeter (ADV) to evaluate velocity data generated by the PIV analysis. Results show that field-based PIV captures nicely complex patterns of fluid motion at the surface of the flow, revealing the two-dimensional characteristics of coherent flow structures. Velocities resulting from the PIV analysis match measured velocities most closely where the flow is least complex and where seeding material remains uniformly distributed throughout the flow. Overall the method appears promising for qualitatively assessing flow structure and for quantifying the size, duration, and vorticity of turbulent structures. Field-based PIV is a valuable technique that can be used along with traditional velocity measurements to more completely and

  12. Flow of liquid metals in curved channels under a transversely applied magnetic field, (3)

    International Nuclear Information System (INIS)

    Arai, Shigeki; Tomita, Yukio; Sudou, Kouzou.

    1979-01-01

    With the development of electromagnetic pumps in nuclear, metallurgical and casting industries, investigations of not only laminar flow but also transient and turbulent flows in magnetohydrodynamic (MHD) channels are the matters of much concern. However, it is no exaggeration to say that there was no investigation of transient and turbulent flows in curved MHD channels. In this report, the influences of Reynolds number, Hartmann number, radius of curvature and aspect ratio on the coefficient of friction in transient and turbulent flow channels are discussed. In transient flow region, the curve representing the product of the coefficient of channel friction in curved channels and Reynolds number has no clear transition point in the flow of comparatively small Hartmann number. However, as the intensity of magnetic field is increased, the curve transfers to the transition due to the effect of suppressing secondary flow, and if the magnetic field is further increased, it was found that it approached the crisis-free type transition. In turbulent flow region, the coefficient of channel friction can be expressed approximately by the empirical equation given first in this report. Also the effect of magnetic field on the turbulent flow in curved channels can be explained by using Hartmann effect, turbulence suppression effect, and the effect of suppressing secondary flow based on Lorentz's force. (Wakatsuki, Y.)

  13. Computational Flow Dynamic Simulation of Micro Flow Field Characteristics Drainage Device Used in the Process of Oil-Water Separation

    Directory of Open Access Journals (Sweden)

    Guangya Jin

    2017-01-01

    Full Text Available Aqueous crude oil often contains large amounts of produced water and heavy sediment, which seriously threats the safety of crude oil storage and transportation. Therefore, the proper design of crude oil tank drainage device is prerequisite for efficient purification of aqueous crude oil. In this work, the composition and physicochemical properties of crude oil samples were tested under the actual conditions encountered. Based on these data, an appropriate crude oil tank drainage device was developed using the principle of floating ball and multiphase flow. In addition, the flow field characteristics in the device were simulated and the contours and streamtraces of velocity magnitude at different nine moments were obtained. Meanwhile, the improvement of flow field characteristics after the addition of grids in crude oil tank drainage device was validated. These findings provide insights into the development of effective selection methods and serve as important references for oil-water separation process.

  14. Fuel density effect on near nozzle flow field in small laminar coflow diffusion flames

    KAUST Repository

    Xiong, Yuan

    2015-01-01

    Flow characteristics in small coflow diffusion flames were investigated with a particular focus on the near-nozzle region and on the buoyancy force exerted on fuels with densities lighter and heavier than air (methane, ethylene, propane, and n-butane). The flow-fields were visualized through the trajectories of seed particles. The particle image velocimetry technique was also adopted for quantitative velocity field measurements. The results showed that the buoyancy force exerted on the fuel as well as on burnt gas significantly distorted the near-nozzle flow-fields. In the fuels with densities heavier than air, recirculation zones were formed very close to the nozzle, emphasizing the importance of the relative density of the fuel to that of the air on the flow-field. Nozzle heating influenced the near-nozzle flow-field particularly among lighter fuels (methane and ethylene). Numerical simulations were also conducted, focusing specifically on the effect of specifying inlet boundary conditions for fuel. The results showed that a fuel inlet boundary with a fully developed velocity profile for cases with long tubes should be specified inside the fuel tube to permit satisfactory prediction of the flow-field. The calculated temperature fields also indicated the importance of the selection of the location of the inlet boundary, especially in testing various combustion models that include soot in small coflow diffusion flames. © 2014 The Combustion Institute.

  15. Thermodynamic coupling of heat and matter flows in near-field regions of nuclear waste repositories

    International Nuclear Information System (INIS)

    Carnahan, C.L.

    1983-11-01

    In near-field regions of nuclear waste repositories, thermodynamically coupled flows of heat and matter can occur in addition to the independent flows in the presence of gradients of temperature, hydraulic potential, and composition. The following coupled effects can occur: thermal osmosis, thermal diffusion, chemical osmosis, thermal filtration, diffusion thermal effect, ultrafiltration, and coupled diffusion. Flows of heat and matter associated with these effects can modify the flows predictable from the direct effects, which are expressed by Fourier's law, Darcy's law, and Fick's law. The coupled effects can be treated quantitatively together with the direct effects by the methods of the thermodynamics of irreversible processes. The extent of departure of fully coupled flows from predictions based only on consideration of direct effects depends on the strengths of the gradients driving flows, and may be significant at early times in backfills and in near-field geologic environments of repositories. Approximate calculations using data from the literature and reasonable assumptions of repository conditions indicate that thermal-osmotic and chemical-osmotic flows of water in semipermeable backfills may exceed Darcian flows by two to three orders of magnitude, while flows of solutes may be reduced greatly by ultrafiltration and chemical osmosis, relative to the flows predicted by advection and diffusion alone. In permeable materials, thermal diffusion may contribute to solute flows to a smaller, but still significant, extent

  16. Slot Nozzle Effects for Reduced Sonic Boom on a Generic Supersonic Wing Section

    Science.gov (United States)

    Caster, Raymond S.

    2010-01-01

    NASA has conducted research programs to reduce or eliminate the operational restrictions of supersonic aircraft over populated areas. Restrictions are due to the disturbance from the sonic boom, caused by the coalescence of shock waves formed off the aircraft. Results from two-dimensional computational fluid dynamic (CFD) analyses (performed on a baseline Mach 2.0 nozzle in a simulated Mach 2.2 flow) indicate that over-expanded and under-expanded operation of the nozzle has an effect on the N-wave boom signature. Analyses demonstrate the feasibility of reducing the magnitude of the sonic boom N-wave by controlling the nozzle plume interaction with the nozzle boat tail shock structure. This work was extended to study the impact of integrating a high aspect ratio exhaust nozzle or long slot nozzle on the trailing edge of a supersonic wing. The nozzle is operated in a highly under-expanded condition, creating a large exhaust plume and a shock at the trailing edge of the wing. This shock interacts with and suppresses the expansion wave caused by the wing, a major contributor to the sonic boom signature. The goal was to reduce the near field pressures caused by the expansion using a slot nozzle located at the wing trailing edge. Results from CFD analysis on a simulated wing cross-section and a slot nozzle indicate potential reductions in sonic boom signature compared to a baseline wing with no propulsion or trailing edge exhaust. Future studies could investigate if this effect could be useful on a supersonic aircraft for main propulsion, auxiliary propulsion, or flow control.

  17. Optimum Tilt Angle of Flow Guide in Steam Turbine Exhaust Hood Considering the Effect of Last Stage Flow Field

    Science.gov (United States)

    CAO, Lihua; LIN, Aqiang; LI, Yong; XIAO, Bin

    2017-07-01

    Heat transfer and vacuum in condenser are influenced by the aerodynamic performance of steam turbine exhaust hood. The current research on exhaust hood is mainly focused on analyzing flow loss and optimal design of its structure without consideration of the wet steam condensing flow and the exhaust hood coupled with the front and rear parts. To better understand the aerodynamic performance influenced by the tilt angle of flow guide inside a diffuser, taking a 600 MW steam turbine as an example, a numerical simulator CFX is adopted to solve compressible three-dimensional (3D) Reynolds time-averaged N-S equations and standard k- ɛ turbulence model. And the exhaust hood flow field influenced by different tilt angles of flow guide is investigated with consideration of the wet steam condensing flow and the exhaust hood coupled with the last stage blades and the condenser throat. The result shows that the total pressure loss coefficient and the static pressure recovery coefficient of exhaust hood change regularly and monotonously with the gradual increase of tilt angle of flow guide. When the tilt angle of flow guide is within the range of 30° to 40°, the static pressure recovery coefficient is in the range of 15.27% to 17.03% and the total pressure loss coefficient drops to approximately 51%, the aerodynamic performance of exhaust hood is significantly improved. And the effective enthalpy drop in steam turbine increases by 0.228% to 0.274%. It is feasible to obtain a reasonable title angle of flow guide by the method of coupling the last stage and the condenser throat to exhaust hood in combination of the wet steam model, which provides a practical guidance to flow guide transformation and optimal design in exhaust hood.

  18. Fluid Flow and Sound Generation at Hydrothermal Vent Fields

    Science.gov (United States)

    1988-04-01

    hydrothermal venting is that of an active ridge of the Juan de Fuca Ridge, largely asa result ofthe sensitivity of heat flow calculations to the resolution of...114 Hell 9 0.5. 10Hz1 100 to- 3~ Pztquakcy Ha Henl 9 0.9- Os 0.7- 0.6 0.3 0.4 0.3 00 1 2 3 4 5 6 7 9 9 30 Fzectaicy (HOz HeUI90.5.IO1s 300 ISO. 10

  19. Enhanced flow field visualization using a flexible animation procedure

    International Nuclear Information System (INIS)

    Marconi, F.; Moretti, G.; Englund, D.C.

    1989-01-01

    A flexible and powerful procedure for transposing computer-generated images onto video tape is used in flowfield visualization. The result is animated sequences which can be used very effectively in the study of both steady and unsteady flows. The key to the procedure is the fact that the images (i.e., frames) of the animated sequence are recorded on the video tapes one at a time after they are created. Thus, the need for a mass storage system is eliminated because after a frame is recorded it is discarded. 7 references

  20. Analysis of the pressure fields in a swirling annular jet flow

    Science.gov (United States)

    Percin, M.; Vanierschot, M.; Oudheusden, B. W. van

    2017-12-01

    In this paper, we investigate the flow structures and pressure fields of a free annular swirling jet flow undergoing vortex breakdown. The flow field is analyzed by means of time-resolved tomographic particle image velocimetry measurements, which enable the reconstruction of the three-dimensional time-resolved pressure fields using the governing flow equations. Both time-averaged and instantaneous flow structures are discussed, including a characterization of the first- and second-order statistical moments. A Reynolds decomposition of the flow field shows that the time-averaged flow is axisymmetric with regions of high anisotropic Reynolds stresses. Two recirculation zones exist that are surrounded by regions of very intense mixing. Notwithstanding the axisymmetric nature of the time-averaged flow, a non-axisymmetric structure of the instantaneous flow is revealed, comprising a central vortex core which breaks up into a precessing vortex core. The winding sense of this helical structure is opposite to the swirl direction and it is wrapped around the vortex breakdown bubble. It precesses around the central axis of the flow at a frequency corresponding to a Strouhal number of 0.27. The precessing vortex core is associated with a low-pressure region along the central axis of the jet and the maximum pressure fluctuations occur upstream of the vortex breakdown location, where the azimuthal velocity component also reaches peak values as a result of the inward motion of the fluid and the conservation of angular momentum. The POD analysis of the pressure fields suggests that the precessing helical vortex formation is the dominant coherent structure in the instantaneous flow.

  1. Experimental study of flow field characteristics on bed configurations in the pebble bed reactor

    International Nuclear Information System (INIS)

    Jia, Xinlong; Gui, Nan; Yang, Xingtuan; Tu, Jiyuan; Jia, Haijun; Jiang, Shengyao

    2017-01-01

    Highlights: • PTV study of flow fields of pebble bed reactor with different configurations are carried out. • Some criteria are proposed to quantify vertical velocity field and flow uniformity. • The effect of different pebble bed configurations is also compared by the proposed criteria. • The displacement thickness is used analogically to analyze flow field characteristics. • The effect of mass flow variation in the stagnated region of the funnel flow is measured. - Abstract: The flow field characteristics are of fundamental importance in the design work of the pebble bed high temperature gas cooled reactor (HTGR). The different effects of bed configurations on the flow characteristics of pebble bed are studied through the PTV (Particle Tracking Velocimetry) experiment. Some criteria, e.g. flow uniformity (σ) and mass flow level (α), are proposed to estimate vertical velocity field and compare the bed configurations. The distribution of the Δθ (angle difference between the individual particle velocity and the velocity vector sum of all particles) is also used to estimate the resultant motion consistency level. Moreover, for each bed configuration, the thickness of displacement is analyzed to measure the effect of the funnel flow zone based on the boundary layer theory. Detailed information shows the quantified characteristics of bed configuration effects on flow uniformity and other characteristics; and the sequence of levels of each estimation criterion is obtained for all bed configurations. In addition, a good design of the pebble bed configuration is suggested and these estimation criteria can be also applied and adopted in testing other geometry designs of pebble bed.

  2. Local motion detectors are required for the computation of expansion flow-fields

    Directory of Open Access Journals (Sweden)

    Tabea Schilling

    2015-09-01

    Full Text Available Avoidance of predators or impending collisions is important for survival. Approaching objects can be mimicked by expanding flow-fields. Tethered flying fruit flies, when confronted with an expansion flow-field, reliably turn away from the pole of expansion when presented laterally, or perform a landing response when presented frontally. Here, we show that the response to an expansion flow-field is independent of the overall luminance change and edge acceleration. As we demonstrate by blocking local motion-sensing neurons T4 and T5, the response depends crucially on the neural computation of appropriately aligned local motion vectors, using the same hardware that also controls the optomotor response to rotational flow-fields.

  3. Integrated PEMFC Flow Field Design Concept for Gravity Independent Passive Water Removal Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ElectroChem proposes a Phase II program to advance its very successful SBIR Phase I PEM fuel cell (PEMFC) program. In Phase I, the unique integrated-flow-field...

  4. High Resolution Multispectral Flow Imaging of Cells with Extended Depth of Field, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Proposed is the development the extended depth of field (EDF) or confocal like imaging capabilities of a breakthrough multispectral high resolution imaging flow...

  5. High Resolution Multispectral Flow Imaging of Cells with Extended Depth of Field, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Proposed is the development the extended depth of field (EDF) or confocal like imaging capabilities of a breakthrough multispectral high resolution imaging flow...

  6. Field Effect Flow Control in a Polymer T-Intersection Microfluidic Network

    Science.gov (United States)

    Sniadecki, Nathan J.; Chang, Richard; Beamesderfer, Mike; Lee, Cheng S.; DeVoe, Don L.

    2003-01-01

    We present a study of induced pressure pumping in a polymer microchannel due to differential electroosmotic flow @OF) rates via field-effect flow control (FEFC). The experimental results demonstrate that the induced pressure pumping is dependent on the distance of the FEFC gate from the cathodic gate. A proposed flow model based on a linearly-decaying zeta potential profile is found to successfully predict experimental trends.

  7. Trends in Polymer and Particle Characterization by Microfluidic Field-Flow Fractionation Methods: Science or Business?

    Czech Academy of Sciences Publication Activity Database

    Janča, Josef; Sobota, Jaroslav

    2014-01-01

    Roč. 19, 16 May (2014), s. 296-308 ISSN 1023-666X R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : Asymmetrical flow FFF * Electrical FFF * Field-flow fractionation * Flow FFF * Microelectrical FFF * Microfluidic channels * Microthermal FFF * Miniaturization and resolution * Polymers and particles separation * Sedimentation FFF * Technical benefits of microchannels * Thermal FFF Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.264, year: 2014

  8. Control of Flowing Liquid Films By Electrostatic Fields in Space

    Science.gov (United States)

    Bankoff, S. George; Miksis, Michael J.; Kim, Hyo

    1996-01-01

    A novel type of lightweight space radiator has been proposed which employs internal electrostatic fields to stop coolant leaks from punctures caused by micrometeorites or space debris. Extensive calculations have indicated the feasibility of leak stoppage without film destabilization for both stationary and rotating designs. Solutions of the evolution equation for a liquid-metal film on an inclined plate, using lubrication theory for low Reynolds numbers, Karman-Pohlhausen quadratic velocity profiles for higher Reynolds numbers, and a direct numerical solution are shown. For verification an earth-based falling-film experiment on a precisely-vertical wall with controllable vacuum on either side of a small puncture is proposed. The pressure difference required to start and to stop the leak, in the presence and absence of a strong electric field, will be measured and compared with calculations. Various parameters, such as field strength, film Reynolds number, contact angle, and hole diameter will be examined. A theoretical analysis will be made of the case where the electrode is close enough to the film surface that the electric field equation and the surface dynamics equations are coupled. Preflight design calculations will be made in order to transfer the modified equipment to a flight experiment.

  9. An Effect of Magnetic Field on Arc Plasma Flow

    Czech Academy of Sciences Publication Activity Database

    Kotalík, Pavel; Nishiyama, H.

    2002-01-01

    Roč. 30, č. 1 (2002), s. 160-161 ISSN 0093-3813 Institutional research plan: CEZ:AV0Z2043910 Keywords : magnetic field, plasma Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.170, year: 2002

  10. Low stoichiometry operation of a proton exchange membrane fuel cell employing the interdigitated flow field

    DEFF Research Database (Denmark)

    Berning, Torsten; Kær, Søren Knudsen

    2012-01-01

    A multiphase fuel cell model based on computational fluid dynamics is used to investigate the possibility of operating a proton exchange membrane fuel cell at low stoichiometric flow ratios (ξ < 1.5) employing the interdigitated flow field design and using completely dry inlet gases. A case study...

  11. Localized electric field induced transition and miniaturization of two-phase flow patterns inside microchannels.

    Science.gov (United States)

    Sharma, Abhinav; Tiwari, Vijeet; Kumar, Vineet; Mandal, Tapas Kumar; Bandyopadhyay, Dipankar

    2014-10-01

    Strategic application of external electrostatic field on a pressure-driven two-phase flow inside a microchannel can transform the stratified or slug flow patterns into droplets. The localized electrohydrodynamic stress at the interface of the immiscible liquids can engender a liquid-dielectrophoretic deformation, which disrupts the balance of the viscous, capillary, and inertial forces of a pressure-driven flow to engender such flow morphologies. Interestingly, the size, shape, and frequency of the droplets can be tuned by varying the field intensity, location of the electric field, surface properties of the channel or fluids, viscosity ratio of the fluids, and the flow ratio of the phases. Higher field intensity with lower interfacial tension is found to facilitate the oil droplet formation with a higher throughput inside the hydrophilic microchannels. The method is successful in breaking down the regular pressure-driven flow patterns even when the fluid inlets are exchanged in the microchannel. The simulations identify the conditions to develop interesting flow morphologies, such as (i) an array of miniaturized spherical or hemispherical or elongated oil drops in continuous water phase, (ii) "oil-in-water" microemulsion with varying size and shape of oil droplets. The results reported can be of significance in improving the efficiency of multiphase microreactors where the flow patterns composed of droplets are preferred because of the availability of higher interfacial area for reactions or heat and mass exchange. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Laminar and turbulent nozzle-jet flows and their acoustic near-field

    International Nuclear Information System (INIS)

    Bühler, Stefan; Obrist, Dominik; Kleiser, Leonhard

    2014-01-01

    We investigate numerically the effects of nozzle-exit flow conditions on the jet-flow development and the near-field sound at a diameter-based Reynolds number of Re D = 18 100 and Mach number Ma = 0.9. Our computational setup features the inclusion of a cylindrical nozzle which allows to establish a physical nozzle-exit flow and therefore well-defined initial jet-flow conditions. Within the nozzle, the flow is modeled by a potential flow core and a laminar, transitional, or developing turbulent boundary layer. The goal is to document and to compare the effects of the different jet inflows on the jet flow development and the sound radiation. For laminar and transitional boundary layers, transition to turbulence in the jet shear layer is governed by the development of Kelvin-Helmholtz instabilities. With the turbulent nozzle boundary layer, the jet flow development is characterized by a rapid changeover to a turbulent free shear layer within about one nozzle diameter. Sound pressure levels are strongly enhanced for laminar and transitional exit conditions compared to the turbulent case. However, a frequency and frequency-wavenumber analysis of the near-field pressure indicates that the dominant sound radiation characteristics remain largely unaffected. By applying a recently developed scaling procedure, we obtain a close match of the scaled near-field sound spectra for all nozzle-exit turbulence levels and also a reasonable agreement with experimental far-field data

  13. Effect of non-uniform mean flow field on acoustic propagation problems in computational aeroacoustics

    DEFF Research Database (Denmark)

    Si, Haiqing; Shen, Wen Zhong; Zhu, Wei Jun

    2013-01-01

    Acoustic propagation in the presence of a non-uniform mean flow is studied numerically by using two different acoustic propagating models, which solve linearized Euler equations (LEE) and acoustic perturbation equations (APE). As noise induced by turbulent flows often propagates from near field t...

  14. Computational analysis of flow field around Ahmed car model passing underneath a flyover

    Science.gov (United States)

    Musa, Md Nor; Osman, Kahar; Hamat, Ab Malik A.

    2012-06-01

    A flow structure around a ground vehicle has been studied by many researchers using numerous methods, either computational or experimental. However, no analysis of flow field generated by a car passing under a flyover has been carried out. One of the famous simplified models of a car is the Ahmed body that has been established to investigate the influence of the flow structure on the drag. In this paper, we investigate a flow field around Ahmed body of a single cruising condition as the vehicle passes under a flyover, using a computational method with RANS equation. The main objective of this paper is to evaluate the turbulence kinetic energy and velocity magnitude developed within the wall boundary created by the flyover, to the air flow field that is generated by the Ahmed reference car. It was observed that the simulated airflow passes the vehicle was bounded by the wall of the flyover and consequently changes the pattern of the flow field. Understanding the characteristic of this flow field under a flyover is essential if one wants to maximize the recovery of the dissipated energy which, for example, can be used to power a small vertical-axis wind turbine to produce and store electrical energy for lighting under the flyover.

  15. Analysis of Low-Speed Stall Aerodynamics of a Business Jets Wing Using STAR-CCM+

    Science.gov (United States)

    Bui, Trong

    2016-01-01

    Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) analysis was conducted: to study the low-speed stall aerodynamics of a GIII aircrafts swept wing modified with (1) a laminar-flow wing glove, or (2) a seamless flap. The stall aerodynamics of these two different wing configurations were analyzed and compared with the unmodified baseline wing for low-speed flight. The Star-CCM+ polyhedral unstructured CFD code was first validated for wing stall predictions using the wing-body geometry from the First AIAA CFD High-Lift Prediction Workshop.

  16. Optimization of aerodynamic efficiency for twist morphing MAV wing

    Directory of Open Access Journals (Sweden)

    N.I. Ismail

    2014-06-01

    Full Text Available Twist morphing (TM is a practical control technique in micro air vehicle (MAV flight. However, TM wing has a lower aerodynamic efficiency (CL/CD compared to membrane and rigid wing. This is due to massive drag penalty created on TM wing, which had overwhelmed the successive increase in its lift generation. Therefore, further CL/CDmax optimization on TM wing is needed to obtain the optimal condition for the morphing wing configuration. In this paper, two-way fluid–structure interaction (FSI simulation and wind tunnel testing method are used to solve and study the basic wing aerodynamic performance over (non-optimal TM, membrane and rigid wings. Then, a multifidelity data metamodel based design optimization (MBDO process is adopted based on the Ansys-DesignXplorer frameworks. In the adaptive MBDO process, Kriging metamodel is used to construct the final multifidelity CL/CD responses by utilizing 23 multi-fidelity sample points from the FSI simulation and experimental data. The optimization results show that the optimal TM wing configuration is able to produce better CL/CDmax magnitude by at least 2% than the non-optimal TM wings. The flow structure formation reveals that low TV strength on the optimal TM wing induces low CD generation which in turn improves its overall CL/CDmax performance.

  17. Effects of Canard on the Flowfield over a Wing

    Science.gov (United States)

    Nayebzadeh, Arash

    2015-11-01

    Surface and flowfield pressure measurements have been done over delta wing/canard configuration in a variety of canard vertical and horizontal locations and angles of attack. The experimental model consisted of wing, canard and a body to accommodate pressure tubing and canard rotation mechanism. All the tests have been performed at subsonic velocities and the effect of canard were analyzed through comparison between surface and flowfield pressure distributions. It was found that vortex flow pattern over the wing is dominated mainly by canard vertical position and in some cases, by merging of canard and wing vortices. In addition, the pressure loss induced by canard vortex on the wing surface moves the wing vortex toward the leading edge. In the mid canard configuration, canard and wing vortices merge at x/c greater than 0.5 and as a result of this phenomenon, abrupt pressure loss induces more stable vortex flow over the wing. It is also shown that canard plays a vital role in vortex break down over the wing.

  18. Feasibility study of red blood cell debulking by magnetic field-flow fractionation with step-programmed flow.

    Science.gov (United States)

    Moore, Lee R; Williams, P Stephen; Nehl, Franziska; Abe, Koji; Chalmers, Jeffrey J; Zborowski, Maciej

    2014-02-01

    Emerging applications of rare cell separation and analysis, such as separation of mature red blood cells from hematopoietic cell cultures, require efficient methods of red blood cell (RBC) debulking. We have tested the feasibility of magnetic RBC separation as an alternative to centrifugal separation using an approach based on the mechanism of magnetic field-flow fractionation (MgFFF). A specially designed permanent magnet assembly generated a quadrupole field having a maximum field of 1.68 T at the magnet pole tips, zero field at the aperture axis, and a nearly constant radial field gradient of 1.75 T/mm (with a negligible angular component) inside a cylindrical aperture of 1.9 mm (diameter) and 76 mm (length). The cell samples included high-spin hemoglobin RBCs obtained by chemical conversion of hemoglobin to methemoglobin (met RBC) or by exposure to anoxic conditions (deoxy RBC), low-spin hemoglobin obtained by exposure of RBC suspension to ambient air (oxy RBC), and mixtures of deoxy RBC and cells from a KG-1a white blood cell (WBC) line. The observation that met RBCs did not elute from the channel at the lower flow rate of 0.05 mL/min applied for 15 min but quickly eluted at the subsequent higher flow rate of 2.0 mL/min was in agreement with FFF theory. The well-defined experimental conditions (precise field and flow characteristics) and a well-established FFF theory verified by studies with model cell systems provided us with a strong basis for making predictions about potential practical applications of the magnetic RBC separation.

  19. The forced flow high field test facility SULTAN

    International Nuclear Information System (INIS)

    Horvath, I.; Vecsey, G.; Weymuth, P.

    1984-01-01

    The construction of the 8 Tesla, 1 m bore Test Facility SULTAN - I, a common action of ENEA (I-Frascati), ECN (NL-Petten) and SIN (CH-Villigen), is completed. Results on assembly, cooldown and the first operation of the whole system are presented. The SULTAN facility provides a wide range of capability of parameter variations (field, current, cooling) for the investigation of steady state performance and stability of technical superconductors unders nominal and limiting conditions

  20. Power reduction and the radial limit of stall delay in revolving wings of different aspect ratio

    NARCIS (Netherlands)

    Kruyt, J.W.; Heijst, Van G.F.; Altshuler, D.L.; Lentink, David

    2015-01-01

    Airplanes and helicopters use high aspect ratio wings to reduce the power required to fly, but must operate at low angle of attack to prevent flow separation and stall. Animals capable of slow sustained flight, such as hummingbirds, have low aspect ratio wings and flap their wings at high angle

  1. Liquid-metal flow in a rectangular duct with a non-uniform magnetic field

    International Nuclear Information System (INIS)

    Walker, J.S.

    1986-04-01

    This paper treats liquid-metal flow in rectangular ducts with thin conducting walls. A transverse magnetic field changes from a uniform strength upstream to a weaker uniform strength downstream. The Hartmann number and the interaction parameter are assumed to be large, while the magnetic Reynolds number is assumed to be small. If the magnetic field changes gradually over a long duct length, the velocity and pressure are nearly uniform in each cross section and the flow differs slightly from locally fully developed flow. If the magnetic field changes more abruptly over a shorter duct length, the velocity and pressure are much larger near the walls parallel to the magnetic field than in the central part of duct. Solutions for the pressure drops due to the magnetic field change are presented

  2. Artificial blood-flow controlling effects of inhomogeneity of twisted magnetic fields

    Science.gov (United States)

    Nakagawa, Hidenori; Ohuchi, Mikio

    2017-06-01

    We developed a blood-flow controlling system using magnetic therapy for some types of nervous diseases. In our research, we utilized overlapped extremely low frequency (ELF) fields for the most effective blood-flow for the system. Results showed the possibility that the inhomogeneous region obtained by overlapping the fields at 50 Hz, namely, a desirably twisted field revealed a significant difference in induced electromotive forces at the insertion points of electrodes. In addition, ELF exposures with a high inhomogeneity of the twisted field at 50 Hz out of phase were more effective in generating an induced electromotive difference by approximately 31%, as contrasted with the difference generated by the exposure in phase. We expect that the increase of the inhomogeneity of the twisted field around a blood vessel can produce the most effective electromotive difference in the blood, and also moderately affect the excitable cells relating to the autonomic nervous system for an outstanding blood-flow control in vivo.

  3. Modeling flow and shear stress fields over unsteady three dimensional dunes

    Science.gov (United States)

    Hardy, Richard; Parsons, Dan; Ashworth, Phil; Reesink, Arjan; Best, Jim

    2014-05-01

    The flow field over dunes has been extensively measured in laboratory conditions and there is general understanding on the nature of the flow over dunes formed under equilibrium flow conditions. This has allowed an understanding of bed shear stress to be derived and the development of morpho-dynamic models. However, fluvial systems typically experience unsteady flow and therefore the sediment-water interface is constantly responding and reorganizing to these unsteady flows and stresses, over a range of both spatial and temporal scales. This is primarily through the adjustment of bed forms (including ripples, dunes and bar forms) which then subsequently alter the flow field. This paper investigates, through the application of a numerical model, the influence of these roughness elements on the overall flow and bed shear stress. A series of physical experiments were undertaken in a flume, 16m long and 2m wide, where a fine sand (D50 of 239µm) was water worked under a range of unsteady hydraulic conditions to generate a series of quasi-equilibrium three dimensional bed forms. During the experiments flow was measured with acoustic Doppler velocimeters, (aDv's). On four occasions the flume was drained and the bed topography measured with terrestrial LiDAR to create digital elevation models. This data provide the necessary boundary conditions and validation data for a numerical three dimensional flow model. The prediction of flow over the four static beds demonstrates the spatial distribution of shear stress and the potential sediment transport paths between the dune crests. These appear to be associated with coherent flow structures formed by localized shear flow. These flow predictions are currently being used to develop a fully three dimensional morphodynamic model to further understand dune dynamics under unsteady flow conditions.

  4. Flow field studies on a micro-air-vehicle-scale cycloidal rotor in forward flight

    Science.gov (United States)

    Lind, Andrew H.; Jarugumilli, Tejaswi; Benedict, Moble; Lakshminarayan, Vinod K.; Jones, Anya R.; Chopra, Inderjit

    2014-12-01

    This paper examines the flow physics and principles of force production on a cycloidal rotor (cyclorotor) in forward flight. The cyclorotor considered here consists of two blades rotating about a horizontal axis, with cyclic pitch angle variation about the blade quarter-chord. The flow field at the rotor mid-span is analyzed using smoke flow visualization and particle image velocimeV are compared with flow fields predicted using 2D CFD and time-averaged force measurements acquired in an open-jet wind tunnel at three advance ratios. It is shown that the experimental flow field is nearly two dimensional at μ = 0.73 allowing for qualitative comparisons to be made with CFD. The incoming flow velocity decreases in magnitude as the flow passes through the retreating (upper) half of the rotor and is attributed to power extraction by the blades. A significant increase in flow velocity is observed across the advancing (lower) half of the rotor. The aerodynamic analysis demonstrates that the blades accelerate the flow through the lower aft region of the rotor, where they operate in a high dynamic pressure environment. This is consistent with CFD-predicted values of instantaneous aerodynamic forces which reveal that the aft section of the rotor is the primary region of force production. Phase-averaged flow field measurements showed two blade wakes in the flow, formed by each of the two blades. Analysis of the blades at several azimuthal positions revealed two significant blade-wake interactions. The locations of these blade-wake interactions are correlated with force peaks in the CFD-predicted instantaneous blade forces and highlight their importance to the generation of lift and propulsive force of the cyclorotor.

  5. Effect of electromagnetic field induced by radio frequency waves at 900 to 1800 MHz on bone mineral density of iliac bone wings.

    Science.gov (United States)

    Atay, Tolga; Aksoy, Besir Andac; Aydogan, Nevres Hurriyet; Baydar, Metin Lutfi; Yildiz, Mustafa; Ozdemir, Ragip

    2009-09-01

    Telecommunication has gained a different meaning in daily life with the introduction of the mobile phone system. However, electromagnetic pollution has increased in parallel to this improvement. In this study, we aimed to investigate the effects of electromagnetic waves emitted from cellular phones operating at a frequency of 900 to 1800 MHz on the bone mineral density of the human iliac bone wings, which are the most common carriage sites for mobile phones. A total of 150 male volunteer participants were included in this study. The mean age was 31.85 years, and the age range was between 21 and 57 years. The participants were separated into 2 groups based on as follows: iliac side exposed to electromagnetic wave (group 1) and unexposed side (group 2). Of the total number of participants, 122 were carrying their phones on their right iliac wings, whereas 28 were carrying their phones on their left iliac wings. The mean daily carriage duration was 14.7 hours (between 12 and 20 h), and the mean duration for cellular phone use was 6.2 years (between 4 and 9 yr). Mineral bone density was measured using dual-energy x-ray absorptiometry in the right and the left iliac wings of all the participants. The SPSS 15 software (SPSS Inc, Chicago, IL) was used for statistical analysis. In the comparison of the 2 sides, Student t test was performed and P 0.05). In addition, the mean values of group 1 were not as low as those measured in osteopeny or osteoporosis cases. Current data may suggest that taking into consideration cellular phone use when iliac bone graft is necessary in clinical practice would constitute an important factor for more favorable outcomes.

  6. Numerical analyses of a Couette-Taylor flow in the presence of a magnetic field

    International Nuclear Information System (INIS)

    Tagawa, T; Kaneda, M

    2005-01-01

    An axisymmetric Couette-Taylor flow of liquid metal in the presence of a magnetic field has been numerically studied. An inner cylinder of a coaxial container is rotating at a constant angular velocity whereas the outer cylindrical wall is at rest. An axial or a toroidal magnetic field is applied to this configuration to investigate the influence of such magnetic fields on the liquid metal Couette-Taylor flow. The toroidal magnetic field can be produced with a straight wire along the central axis in which electric current passes. The governing equations of mass conservation, momentum, Ohm's law and conservation of electric charge for an axisymmetric cylindrical coordinate system have been numerically solved with a finite difference method using the HSMAC algorithm. In the numerical analyses, since the Joule heating and the induced magnetic field are neglected, the system parameters are the Hartmann number and the Reynolds number. The numerical results reveal significant difference in the Couette-Taylor flow depending on whether the applied magnetic field is axial or toroidal as well as on the Hartmann and Reynolds numbers. The axial magnetic field damps out the secondary flow efficiently and velocity gradient in the direction of the magnetic field tends to diminish while the toroidal magnetic field does not have such an efficient damping

  7. Effects of the Observed Meridional Flow Variations since 1996 on the Sun's Polar Fields

    Science.gov (United States)

    Hathaway, David H.; Upton, Lisa

    2013-01-01

    The cause of the low and extended minimum in solar activity between Sunspot Cycles 23 and 24 was the small size of Sunspot Cycle 24 itself - small cycles start late and leave behind low minima. Cycle 24 is small because the polar fields produced during Cycle 23 were substantially weaker than those produced during the previous cycles and those (weak) polar fields are the seeds for the activity of the following cycle. The polar fields are produced by the latitudinal transport of magnetic flux that emerged in low-latitude active regions. The polar fields thus depend upon the details of both the flux emergence and the flux transport. We have measured the flux transport flows (differential rotation, meridional flow, and supergranules) since 1996 and find systematic and substantial variation in the meridional flow alone. Here we present experiments using a Surface Flux Transport Model in which magnetic field data from SOHO/MDI and SDO/HMI are assimilated into the model only at latitudes between 45-degrees north and south of the equator (this assures that the details of the active region flux emergence are well represented). This flux is then transported in both longitude and latitude by the observed flows. In one experiment the meridional flow is given by the time averaged (and north-south symmetric) meridional flow profile. In the second experiment the time-varying and north-south asymmetric meridional flow is used. Differences between the observed polar fields and those produced in these two experiments allow us to ascertain the effects of these meridional flow variations on the Sun s polar fields.

  8. An investigation of a flow field in one and half axial turbine stage

    Science.gov (United States)

    Němec, Martin; Jelínek, Tomáš; Milčák, Petr

    2017-09-01

    An investigation of one and half axial turbine stage configuration was carried out in a closed-loop wind tunnel. The investigation was addressed to that impact how the previous stage outlet flow field influences a flow structures in the next stator in steam multistage turbines. The detailed measurement behind the rotor and the second stator was performed with a pneumatic probes to gain a useful data for an impact analysis. Various rotor shroud clearances were also tested to capture the shroud outlet flow field influences.

  9. Research on Duct Flow Field Optimisation of a Robot Vacuum Cleaner

    OpenAIRE

    Lai, Xiao-bo; Wang, Hai-shun; Liu, Hua-shan

    2011-01-01

    The duct of a robot vacuum cleaner is the length of the flow channel between the inlet of the rolling brush blower and the outlet of the vacuum blower. To cope with the pressure drop problem of the duct flow field in a robot vacuum cleaner, a method based on Pressure Implicit with Splitting of Operators (PRISO) algorithm is introduced and the optimisation design of the duct flow field is implemented. Firstly, the duct structure in a robot vacuum cleaner is taken as a research object, with the...

  10. Numerical and experimental research of flow and sound fields in an axial-flow check valve and its optimization

    Directory of Open Access Journals (Sweden)

    Jianping Yu

    2015-11-01

    Full Text Available In order to find a proper method to study the flow and sound fields in an axial-flow check valve, the jetting noise at a nozzle is investigated with simulations and experiments. Based on optimization principle, the main channel of the valve body is numerically investigated and optimized twice. The results show that the resistance coefficient and the maximum noise of the valve are decreased by 0.37 and 23.8 dB, respectively, and the head and the tail of the valve plug are optimized when streamline design is employed on the main channel structure of the valve body.

  11. Dynamically orthogonal field equations for stochastic flows and particle dynamics

    Science.gov (United States)

    2011-02-01

    fields implies orthogonality of their spatial Fourier, Gabor, and Wavelet transforms [5], [35]. Therefore, different DO modes always contain different...modes stochastic solution u (x, t;ω) to the stochastic subspace computed using the five modes solution, i.e. σ2i (t) = var [〈u (x, t;ω) ,vi (x, t...Antoine, R. Murenzi, P. Vandergheynst, and S.T. Ali. Two-dimensional wavelets and their relatives. Cambridge University Press, 2004. [6] V.I. Arnold and

  12. Correlations of Surface Deformation and 3D Flow Field in a Compliant Wall Turbulent Channel Flow.

    Science.gov (United States)

    Wang, Jin; Zhang, Cao; Katz, Joseph

    2015-11-01

    This study focuses on the correlations between surface deformation and flow features, including velocity, vorticity and pressure, in a turbulent channel flow over a flat, compliant Polydimethylsiloxane (PDMS) wall. The channel centerline velocity is 2.5 m/s, and the friction Reynolds number is 2.3x103. Analysis is based on simultaneous measurements of the time resolved 3D velocity and surface deformation using tomographic PIV and Mach-Zehnder Interferometry. The volumetric pressure distribution is calculated plane by plane by spatially integrating the material acceleration using virtual boundary, omni-directional method. Conditional sampling based on local high/low pressure and deformation events reveals the primary flow structures causing the deformation. High pressure peaks appear at the interface between sweep and ejection, whereas the negative deformations peaks (dent) appear upstream, under the sweeps. The persistent phase lag between flow and deformations are presumably caused by internal damping within the PDMS. Some of the low pressure peaks and strong ejections are located under the head of hairpin vortices, and accordingly, are associated with positive deformation (bump). Others bumps and dents are correlated with some spanwise offset large inclined quasi-streamwise vortices that are not necessarily associated with hairpins. Sponsored by ONR.

  13. Engineering of Biomimetic Hair-Flow Sensor Arrays Dedicated to High-Resolution Flow Field Measurements

    NARCIS (Netherlands)

    Dagamseh, A.M.K.; Bruinink, C.M.; Droogendijk, H.; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Krijnen, Gijsbertus J.M.

    2010-01-01

    This paper addresses the latest developments in biomimetic hair-flow sensors towards sensitive high-density arrays. Improving the electrodes design of the hair sensor, using Silicon-on-Insulator (SOI) wafer technology, has resulted in the ability to measure small capacitance changes as caused by

  14. The role of wing kinematics of freely flying birds downstream the wake of flapping wings

    Science.gov (United States)

    Krishnan, Krishnamoorthy; Gurka, Roi

    2016-11-01

    Avian aerodynamics has been a topic of research for centuries. Avian flight features such as flapping, morphing and maneuvering make bird aerodynamics a complex system to study, analyze and understand. Aerodynamic performance of the flapping wings can be quantified by measuring the vortex structures present in the downstream wake. Still, the direct correlation between the flapping wing kinematics and the evolution of wake features need to be established. In this present study, near wake of three bird species (western sandpiper, European starling and American robin) have been measured experimentally. Long duration, time-resolved, particle image velocimetry technique has been used to capture the wake properties. Simultaneously, the bird kinematics have been captured using high speed camera. Wake structures are reconstructed from the collected PIV images for long chord distances downstream. Wake vorticities and circulation are expressed in the wake composites. Comparison of the wake features of the three birds shows similarities and some key differences are also found. Wing tip motions of the birds are extracted for four continuous wing beat cycle to analyze the wing kinematics. Kinematic parameters of all the three birds are compared to each other and similar trends exhibited by all the birds have been observed. A correlation between the wake evolutions with the wing motion is presented. It was found that the wings' motion generates unique flow patterns at the near wake, especially at the transition phases. At these locations, a drastic change in the circulation was observed.

  15. Flow Field and Acoustic Predictions for Three-Stream Jets

    Science.gov (United States)

    Simmons, Shaun Patrick; Henderson, Brenda S.; Khavaran, Abbas

    2014-01-01

    Computational fluid dynamics was used to analyze a three-stream nozzle parametric design space. The study varied bypass-to-core area ratio, tertiary-to-core area ratio and jet operating conditions. The flowfield solutions from the Reynolds-Averaged Navier-Stokes (RANS) code Overflow 2.2e were used to pre-screen experimental models for a future test in the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center (GRC). Flowfield solutions were considered in conjunction with the jet-noise-prediction code JeNo to screen the design concepts. A two-stream versus three-stream computation based on equal mass flow rates showed a reduction in peak turbulent kinetic energy (TKE) for the three-stream jet relative to that for the two-stream jet which resulted in reduced acoustic emission. Additional three-stream solutions were analyzed for salient flowfield features expected to impact farfield noise. As tertiary power settings were increased there was a corresponding near nozzle increase in shear rate that resulted in an increase in high frequency noise and a reduction in peak TKE. As tertiary-to-core area ratio was increased the tertiary potential core elongated and the peak TKE was reduced. The most noticeable change occurred as secondary-to-core area ratio was increased thickening the secondary potential core, elongating the primary potential core and reducing peak TKE. As forward flight Mach number was increased the jet plume region decreased and reduced peak TKE.

  16. Robust size illusion produced by expanding and contracting flow fields.

    Science.gov (United States)

    Dong, Xue; Bai, Jianying; Bao, Min

    2017-04-01

    A new illusion is described. Randomly positioned dots moved radially within an imaginary annular window. The dots' motion periodically changed the direction, leading to an alternating percept of expanding and contracting motion. Strikingly, the apparent size of the enclosed circular region shrank during the dots' expanding phases and dilated during the contracting phases. We quantitatively measured the illusion, and found that the presence of energy at the local kinetic edge could not account for the illusion. Besides, we reproduced the illusion on a natural scene background seen from a first-person point of view that moved forward and backward periodically. Blurring the boundaries of motion areas could not reverse the illusion in all subjects. Taken together, our observed illusion is likely induced by optic flow processing with some components of motion contrast. Expanding or contracting dots may induce the self-motion perception of either approaching or leaving way from the circle. These will make the circle appear smaller or larger since its retinal size remains constant. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Numerical simulation of nonequilibrium inductive plasma flow coupled with electromagnetic field calculation

    Science.gov (United States)

    Yu, Minghao; Takahashi, Yusuke; Kihara, Hisashi; Abe, Ken-ichi; Yamada, Kazuhiko; Abe, Takashi

    2014-12-01

    Numerical investigation of nonequilibrium inductively coupled plasma (ICP) flow was carried out to study the physical properties of the flow inside a 10-kW ICP torch with the working gas being nitrogen. The flow field was described by two-dimensional compressible axisymmetric Navier-Stokes (N-S) equations that took into account 5 species and 8 chemical reactions. The magnetic vector-potential equations were tightly coupled with the flow-field equations to describe the heating process by inductive discharge. A four-temperature model was adopted to model thermal nonequilibrium process in the discharge torch. The characteristics of ICP flow such as thermal nonequilibrium, inductive discharge, and strong effects of Lorentz forces became clear through the present study.

  18. Numerical Simulation of Bottomhole Flow Field Structure in Particle Impact Drilling

    Science.gov (United States)

    Zhou, Weidong; Huang, Jinsong; Li, Luopeng

    2018-01-01

    In order to quantitatively describe the flow field distribution of the PID drilling bit in the bottomhole working condition, the influence of the fluid properties (pressure and viscosity) on the flow field of the bottom hole and the erosion and wear law of the drill body are compared. The flow field model of the eight - inch semi - vertical borehole drilling bit was established by CFX software. The working state of the jet was returned from the inlet of the drill bit to the nozzle outlet and flowed out at the bottom of the nozzle. The results show that there are irregular three-dimensional motion of collision and bounce after the jetting, resulting in partial impact on the drill body and causing impact and damage to the cutting teeth. The jet of particles emitted by different nozzles interfere with each other and affect the the bottom of the impact pressure; reasonable nozzle position can effectively reduce these interference.

  19. Effect of far-field flow on a columnar crystal in the convective undercooled melt

    Science.gov (United States)

    Ji, Xiao-Jian; Chen, Ming-Wen; Xu, Xiao-Hua; Wang, Zi-Dong

    2015-01-01

    The growth behavior of a columnar crystal in the convective undercooled melt affected by the far-field uniform flow is studied and the asymptotic solution for the interface evolution of the columnar crystal is derived by means of the asymptotic expansion method. The results obtained reveal that the far-field flow induces a significant change of the temperature around the columnar crystal and the convective flow caused by the far-field flow accelerates the growth velocity of the interface of the growing columnar crystal in the upstream direction and inhibits its growth velocity in the downstream direction. Our results are similar to the experimental data and numerical simulations. Project supported by the Overseas Distinguished Scholar Program by the Ministry of Education of China (Grant No. MS2010BJKJ005), the National Natural Science Foundation of China (Grant No. 10972030), and the Science and Technology Support Project of Jiangxi, China (Grant No. 20112BBE50006).

  20. Numerical solutions of Navier-Stokes equations for a Butler wing

    Science.gov (United States)

    Abolhassani, Jamshid S.; Tiwari, Surendra N.; Smith, Robert E.

    1987-01-01

    The flow field is simulated on the surface of a Butler wing in a uniform stream. Results are presented for Mach number 3.5 and Reynolds number of 2,000,000. The simulation is done by integrating the viscous Navier-Stokes equations. These equations govern the unsteady, viscous, compressible and heat conducting flow of an ideal gas. The equations are written in curvilinear coordinates so that the wing surface is represented accurately. The O-type and H-type grids have been used for this study, and results are compared. The governing equations are solved by the MacCormack time-split method, and the results are compared with other theoretical and experimental results. The codes are written in FORTRAN, vectorized and currently run on the CDC Vector Processing System (VPS-32) computer.

  1. Numerical Analysis of Flow Field in Generator End-Winding Region

    Directory of Open Access Journals (Sweden)

    Wei Tong

    2008-01-01

    Full Text Available Cooling in an end-winding region of a high-powered, large-sized generator still remains a challenge today because of a number of factors: a larger number of parts/components with irregular geometries, complexity in cooling flow paths, flow splitting and mixing, and interactions between rotor-induced rotating flows and nonrotating flows from stationary sections. One of the key challenges is to model cooling flows passing through armature bars, which are made up of bundles of strands of insulated copper wires and are bent oppositely to cross each other. This work succeeded in modeling a complex generator end-winding region with great efforts to simplify the model by treating the armature bar region as a porous medium. The flow and pressure fields at the end-winding region were investigated numerically using an axial symmetric computational fluid dynamics (CFD model. Based on the analysis, the cooling flow rate at each flow branch (rotor-stator gap, rotor subslot, outside space block, and small ventilation holes to the heat exchanger was determined, and the high-pressure gradient zones were identified. The CFD results have been successfully used to optimize the flow path configuration for improving the generator operation performance, and the control of the cooling flow, as well as minimizing windage losses and flow-introduced noises.

  2. Effect of CO2 injection on brine flow and salt precipitation after gas field production

    NARCIS (Netherlands)

    Tambach, T.J.; Loeve, D.; Hofstee, C.; Plug, W.J.; Maas, J.G.

    2014-01-01

    This paper reports modeling of gas field production and CO2 injection in a theoretical reservoir based on characteristics of the P18 gas field in the Dutch offshore, which consists of four geological deposits with different petrophysical properties. We especially focus on the brine flow during and

  3. Effect of a magnetic field on a rotating fluid flow | Fenuga | Journal of ...

    African Journals Online (AJOL)

    In this paper, we investigate the effect of a magnetic field on a rotating fluid flow in a rotating frame. A system of equations of motion was considered for some components of velocity and magnetic fields. Under some mathematical conditions and assumptions, the system of equations of motion give rise to a differential ...

  4. Time-varying vector fields and their flows

    CERN Document Server

    Jafarpour, Saber

    2014-01-01

    This short book provides a comprehensive and unified treatment of time-varying vector fields under a variety of regularity hypotheses, namely finitely differentiable, Lipschitz, smooth, holomorphic, and real analytic. The presentation of this material in the real analytic setting is new, as is the manner in which the various hypotheses are unified using functional analysis. Indeed, a major contribution of the book is the coherent development of locally convex topologies for the space of real analytic sections of a vector bundle, and the development of this in a manner that relates easily to classically known topologies in, for example, the finitely differentiable and smooth cases. The tools used in this development will be of use to researchers in the area of geometric functional analysis.

  5. The importance of three dimensional dune morphology on the time dependent flow field

    Science.gov (United States)

    Hardy, Richard; Parsons, Dan; Reesink, Arnold; Best, Jim

    2017-04-01

    The flow field over dunes has been extensively studied and there is general understanding of the nature of the flow over dunes formed over two dimensional dunes under equilibrium flow conditions. This model is typically used to explain flow fields over all dunes fields. However, fluvial systems typically experience unsteady flow and therefore the sediment-water interface is constantly reorganizing to form complex three-dimensional morphologies (ripples, dunes and bar forms). Here we investigate how flow over natural three dimensional dunes differs from the accepted model of flow of two dimensional dunes. A series of experiments were undertaken in a flume where fine sand was water worked under a range of unsteady hydraulic conditions to generate quasi-equilibrium three dimensional bed forms. On four occasions, the flume was drained and the bed topography measured with terrestrial LiDAR to create digital elevation models (DEM). Here to demonstrate the approach we choose the DEM with the greatest topographic variation and apply a new Large Eddy Simulation model with an wall-adapting local eddy-viscosity (WALE) turbulence model and a non-linear higher-order numerical differencing scheme. This provided a three dimensional time dependent prediction of the flow field over the static three-dimensional dune morphology at millimeter and hertz scale resolution. The numerically predicted flows were analyzed by standard Reynolds decomposition approaches and Eulerian and Lagrangian coherent flow structure identification methods. The results show that the superimposed bed forms can cause changes in the nature of the classical separated flow regions, in particularly the number of locations where vortices are shed and the points of flow reattachment. Coalescence of vortices generated downstream and can be seen to move to the free surface and form kolk signatures. These structures also correlate in space and time showing a clear flow morphology feedback. The modified flow field

  6. Comparison of Miniaturized and Conventional Asymmetrical Flow Field-Flow Fractionation (AF4 Channels for Nanoparticle Separations

    Directory of Open Access Journals (Sweden)

    Zengchao You

    2017-03-01

    Full Text Available The performance of a miniaturized channel for the separation of polymer and metal nanoparticles (NP using Asymmetrical Flow Field-Flow Fractionation (AF4 was investigated and compared with a conventional AF4 system. To develop standard separation methods, experimental parameters like cross flow, gradient profile and injection time were varied and optimized. Corresponding chromatographic parameters were calculated and compared. Our results indicate that the chromatographic resolution in the miniaturized channel is lower, whereas significantly shorter analyses time and less solvent consumption were obtained. Moreover, the limit of detection (LOD and limit of quantification (LOQ obtained from hyphenation with a UV-detector are obviously lower than in a conventional channel, which makes the miniaturized channel interesting for trace analysis.

  7. Secular variation of the Earth's magnetic field: induced by the ocean flow?

    International Nuclear Information System (INIS)

    Ryskin, Gregory

    2009-01-01

    Secular variation of the Earth's main magnetic field is believed to originate in the Earth's core. (The main field is operationally defined as comprising spherical harmonics of degree l≤10.) I propose a different mechanism of secular variation: ocean water being a conductor of electricity, the magnetic field induced by the ocean as it flows through the Earth's main field may depend on time and manifest itself globally as secular variation. This proposal is supported by calculation of secular variation using the induction equation of magnetohydrodynamics, the observed main field and the ocean flow field. The predicted secular variation is in rough agreement with that observed. Additional support is provided by the striking temporal correlation (hitherto unsuspected) between the intensity of the North Atlantic oceanic circulation and the rate of secular variation in Western Europe; this explains, in particular, the geomagnetic jerks, and the recently discovered correlation between secular variation and climate. Spatial correlation between ocean currents and secular variation is also strong.

  8. Numerical simulation of a backward-facing step flow in a microchannel with external electric field

    Directory of Open Access Journals (Sweden)

    Qing-He Yao

    2015-03-01

    Full Text Available A backward-facing step flow in the microchannel with external electric field was investigated numerically by a high-order accuracy upwind compact difference scheme in this work. The Poisson–Boltzmann and Navier–Stokes equations were computed by the high-order scheme, and the results confirmed the ability of the new solver in simulation of micro-scale electric double layer effects. The flow fields were displayed for different Reynolds numbers; the positions of the vortex saddle point of model with external electric field and model without external electric field were compared. The average velocity increases linearly with the electric field intensity; however, the Joule heating effects cannot be neglected when the electric field intensity increases to a certain level.

  9. Flow of conductive fluid between parallel disks in an axial magnetic field, (2)

    International Nuclear Information System (INIS)

    Koike, Kazuo; Kamiyama, Shin-ichi

    1981-01-01

    The basic characteristics of the flow in a disc type non-equilibrium MHD power generator were studied. The flow of conductive fluid between parallel disks in an axial magnetic field was analyzed as the subsonic MHD turbulent approach flow of viscous compressible fluid, taking the electron temperature dependence of conductivity into account. The equations for the flow between disks are described by ordinary electromagnetic hydrodynamic approximation. Practical numerical calculation was performed for the non-equilibrium argon plasma seeded with potassium. The effects of the variation of characteristics of non-equilibrium plasma in main flow and boundary layer on the flow characteristics became clear. The qualitative tendency of the properties of MHD generators can be well explained. (Kato, T.)

  10. Flow of a two-dimensional liquid metal jet in a strong magnetic field

    International Nuclear Information System (INIS)

    Reed, C.B.; Molokov, S.

    2002-01-01

    Two-dimensional, steady flow of a liquid metal slender jet pouring from a nozzle in the presence of a transverse, nonuniform magnetic field is studied. The surface tension has been neglected, while gravity is shown to be not important. The main aim of the study is to evaluate the importance of the inertial effects. It has been shown that for gradually varying fields characteristic for the divertor region of a tokamak, inertial effects are negligible for N > 10, where N is the interaction parameter. Thus the inertialess flow model is expected to give good results even for relatively low magnetic fields and high jet velocity. Simple relations for the jet thickness and velocity have been derived. The results show that the jet becomes thicker if the field increases along the flow and thinner if it decreases

  11. Effect of the induced magnetic field on peristaltic flow of a couple stress fluid

    International Nuclear Information System (INIS)

    Mekheimer, Kh.S.

    2008-01-01

    We have analyzed the MHD flow of a conducting couple stress fluid in a slit channel with rhythmically contracting walls. In this analysis we are taking into account the induced magnetic field. Analytical expressions for the stream function, the magnetic force function, the axial pressure gradient, the axial induced magnetic field and the distribution of the current density across the channel are obtained using long wavelength approximation. The results for the pressure rise, the frictional force per wave length, the axial induced magnetic field and distribution of the current density across the channel have been computed numerically and the results were studied for various values of the physical parameters of interest, such as the couple stress parameter γ, the Hartmann number M, the magnetic Reynolds number R m and the time averaged mean flow rate θ. Contour plots for the stream and magnetic force functions are obtained and the trapping phenomena for the flow field is discussed

  12. Heat transfer and flow analysis of nanofluid flow between parallel plates in presence of variable magnetic field using HPM

    Energy Technology Data Exchange (ETDEWEB)

    Hatami, M., E-mail: m.hatami@tue.nl [Esfarayen University of Technology, Mechanical Engineering Department, Esfarayen, North Khorasan (Iran, Islamic Republic of); Jing, Dengwei; Song, Dongxing [International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi' an 710049 (China); Sheikholeslami, M.; Ganji, D.D. [Department of Mechanical Engineering, Babol University of Technology, Babol (Iran, Islamic Republic of)

    2015-12-15

    In this study, effect of variable magnetic field on nanofluid flow and heat transfer analysis between two parallel disks is investigated. By using the appropriate transformation for the velocity, temperature and concentration, the basic equations governing the flow, heat and mass transfer were reduced to a set of ordinary differential equations. These equations subjected to the associated boundary conditions were solved analytically using Homotopy perturbation method. The analytical investigation is carried out for different governing parameters namely: squeeze number, suction parameter, Hartmann number, Brownian motion parameter, thermophrotic parameter and Lewis number. Results show that Nusselt number has direct relationship with Brownian motion parameter and thermophrotic parameter but it is a decreasing function of squeeze number, suction parameter, Hartmann number and Lewis number. - Highlights: • Heat and mass transfer of nanofluids between parallel plates investigated. • A variable magnetic field is applied on the plates. • Governing equations are solved analytically. • Effects of physical parameters are discussed on the Nusselt number.

  13. Heat transfer and flow analysis of nanofluid flow between parallel plates in presence of variable magnetic field using HPM

    International Nuclear Information System (INIS)

    Hatami, M.; Jing, Dengwei; Song, Dongxing; Sheikholeslami, M.; Ganji, D.D.

    2015-01-01

    In this study, effect of variable magnetic field on nanofluid flow and heat transfer analysis between two parallel disks is investigated. By using the appropriate transformation for the velocity, temperature and concentration, the basic equations governing the flow, heat and mass transfer were reduced to a set of ordinary differential equations. These equations subjected to the associated boundary conditions were solved analytically using Homotopy perturbation method. The analytical investigation is carried out for different governing parameters namely: squeeze number, suction parameter, Hartmann number, Brownian motion parameter, thermophrotic parameter and Lewis number. Results show that Nusselt number has direct relationship with Brownian motion parameter and thermophrotic parameter but it is a decreasing function of squeeze number, suction parameter, Hartmann number and Lewis number. - Highlights: • Heat and mass transfer of nanofluids between parallel plates investigated. • A variable magnetic field is applied on the plates. • Governing equations are solved analytically. • Effects of physical parameters are discussed on the Nusselt number

  14. Attenuated Vector Tomography -- An Approach to Image Flow Vector Fields with Doppler Ultrasonic Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qiu; Peng, Qiyu; Huang, Bin; Cheryauka, Arvi; Gullberg, Grant T.

    2008-05-15

    The measurement of flow obtained using continuous wave Doppler ultrasound is formulated as a directional projection of a flow vector field. When a continuous ultrasound wave bounces against a flowing particle, a signal is backscattered. This signal obtains a Doppler frequency shift proportional to the speed of the particle along the ultrasound beam. This occurs for each particle along the beam, giving rise to a Doppler velocity spectrum. The first moment of the spectrum provides the directional projection of the flow along theultrasound beam. Signals reflected from points further away from the detector will have lower amplitude than signals reflected from points closer to the detector. The effect is very much akin to that modeled by the attenuated Radon transform in emission computed tomography.A least-squares method was adopted to reconstruct a 2D vector field from directional projection measurements. Attenuated projections of only the longitudinal projections of the vector field were simulated. The components of the vector field were reconstructed using the gradient algorithm to minimize a least-squares criterion. This result was compared with the reconstruction of longitudinal projections of the vector field without attenuation. Ifattenuation is known, the algorithm was able to accurately reconstruct both components of the full vector field from only one set of directional projection measurements. A better reconstruction was obtained with attenuation than without attenuation implying that attenuation provides important information for the reconstruction of flow vector fields.This confirms previous work where we showed that knowledge of the attenuation distribution helps in the reconstruction of MRI diffusion tensor fields from fewer than the required measurements. In the application of ultrasound the attenuation distribution is obtained with pulse wave transmission computed tomography and flow information is obtained with continuous wave Doppler.

  15. Attenuated Vector Tomography -- An Approach to Image Flow Vector Fields with Doppler Ultrasonic Imaging

    International Nuclear Information System (INIS)

    Huang, Qiu; Peng, Qiyu; Huang, Bin; Cheryauka, Arvi; Gullberg, Grant T.

    2008-01-01

    The measurement of flow obtained using continuous wave Doppler ultrasound is formulated as a directional projection of a flow vector field. When a continuous ultrasound wave bounces against a flowing particle, a signal is backscattered. This signal obtains a Doppler frequency shift proportional to the speed of the particle along the ultrasound beam. This occurs for each particle along the beam, giving rise to a Doppler velocity spectrum. The first moment of the spectrum provides the directional projection of the flow along the ultrasound beam. Signals reflected from points further away from the detector will have lower amplitude than signals reflected from points closer to the detector. The effect is very much akin to that modeled by the attenuated Radon transform in emission computed tomography.A least-squares method was adopted to reconstruct a 2D vector field from directional projection measurements. Attenuated projections of only the longitudinal projections of the vector field were simulated. The components of the vector field were reconstructed using the gradient algorithm to minimize a least-squares criterion. This result was compared with the reconstruction of longitudinal projections of the vector field without attenuation. If attenuation is known, the algorithm was able to accurately reconstruct both components of the full vector field from only one set of directional projection measurements. A better reconstruction was obtained with attenuation than without attenuation implying that attenuation provides important information for the reconstruction of flow vector fields.This confirms previous work where we showed that knowledge of the attenuation distribution helps in the reconstruction of MRI diffusion tensor fields from fewer than the required measurements. In the application of ultrasound the attenuation distribution is obtained with pulse wave transmission computed tomography and flow information is obtained with continuous wave Doppler

  16. Pressure drop and heat transfer of lithium single-phase flow under transverse magnetic field

    International Nuclear Information System (INIS)

    Takahashi, Minoru; Aritomi, Masanori; Inoue, Akira; Matsuzaki, Mitsuo

    1996-01-01

    Pressure drop and heat transfer characteristics of a lithium single-phase flow in a rectangular channel was investigated experimentally in the presence of a magnetic field. Friction loss coefficient under non-magnetic field and skin friction coefficient under magnetic field agreed well with the Blasius formula and a simple analytical expression, respectively. Nusselt number under non-magnetic field was slightly lower than the correlation by Hartnett and Irvine. Heat transfer was enhanced by increasing magnetic field above the Hartmann number of about 200. (author)

  17. The Fabrication of Flow Field Plates for Direct Methanol Fuel Cell Using Lithography and Radio Frequency Sputtering.

    Science.gov (United States)

    Chang, Ho; Kao, Mu-Jung; Chen, Chih-Hao; Cho, Kun-Ching; Hsu, Chun-Yao; Chen, Zhi-Lun

    2015-08-01

    This study uses lithography to etch flow fields on a single side of a printed circuit board (PCB) and combines a flow field plate with a collector plate to make innovative anode flow field plates and cathode flow field plates for a direct methanol fuel cell (DMFC). TiO2 thin film is also sputtered on the anode flow field plate using radio frequency (RF) sputtering. The experimental results show that the prepared DMFC has a better maximum power density of 11.928 mW/cm2. Furthermore, when a TiO2 thin film is sputtered on the flow field plate of the assembled DMFC, the maximum power density is 14.426 mW/cm2, which is actually 21% more than that for a DMFC with no TiO2 thin film coated on the flow field plate.

  18. Kelvin-Helmholtz instability for a bounded plasma flow in a longitudinal magnetic field

    Science.gov (United States)

    Burinskaya, T. M.; Shevelev, M. M.; Rauch, J.-L.

    2011-01-01

    Kelvin-Helmholtz MHD instability in a plane three-layer plasma is investigated. A general dispersion relation for the case of arbitrarily orientated magnetic fields and flow velocities in the layers is derived, and its solutions for a bounded plasma flow in a longitudinal magnetic field are studied numerically. Analysis of Kelvin-Helmholtz instability for different ion acoustic velocities shows that perturbations with wavelengths on the order of or longer than the flow thickness can grow in an arbitrary direction even at a zero temperature. Oscillations excited at small angles with respect to the magnetic field exist in a limited range of wavenumbers even without allowance for the finite width of the transition region between the flow and the ambient plasma. It is shown that, in a low-temperature plasma, solutions resulting in kink-like deformations of the plasma flow grow at a higher rate than those resulting in quasi-symmetric (sausage-like) deformations. The transverse structure of oscillatory-damped eigenmodes in a low-temperature plasma is analyzed. The results obtained are used to explain mechanisms for the excitation of ultra-low-frequency long-wavelength oscillations propagating along the magnetic field in the plasma sheet boundary layer of the Earth's magnetotail penetrated by fast plasma flows.

  19. Kelvin-Helmholtz instability for a bounded plasma flow in a longitudinal magnetic field

    International Nuclear Information System (INIS)

    Burinskaya, T. M.; Shevelev, M. M.; Rauch, J.-L.

    2011-01-01

    Kelvin-Helmholtz MHD instability in a plane three-layer plasma is investigated. A general dispersion relation for the case of arbitrarily orientated magnetic fields and flow velocities in the layers is derived, and its solutions for a bounded plasma flow in a longitudinal magnetic field are studied numerically. Analysis of Kelvin-Helmholtz instability for different ion acoustic velocities shows that perturbations with wavelengths on the order of or longer than the flow thickness can grow in an arbitrary direction even at a zero temperature. Oscillations excited at small angles with respect to the magnetic field exist in a limited range of wavenumbers even without allowance for the finite width of the transition region between the flow and the ambient plasma. It is shown that, in a low-temperature plasma, solutions resulting in kink-like deformations of the plasma flow grow at a higher rate than those resulting in quasi-symmetric (sausage-like) deformations. The transverse structure of oscillatory-damped eigenmodes in a low-temperature plasma is analyzed. The results obtained are used to explain mechanisms for the excitation of ultra-low-frequency long-wavelength oscillations propagating along the magnetic field in the plasma sheet boundary layer of the Earth’s magnetotail penetrated by fast plasma flows.

  20. Wing geometry of Triatoma sordida (Hemiptera: Reduviidae) populations from Brazil.

    Science.gov (United States)

    Vendrami, Daniel Pagotto; Obara, Marcos Takashi; Gurgel-Gonçalves, Rodrigo; Ceretti-Junior, Walter; Marrelli, Mauro Toledo

    2017-04-01

    Triatoma sordida has a widespread distribution in Argentina, Bolivia, Brazil, Paraguay, and Uruguay and is frequently found in peridomestic environments. We investigated size and shape variability of T. sordida wings across Brazil. Field-collected adults from twelve populations were studied. For each individual female, seven landmarks on the right wing were digitalized. Shape variables derived from Procrustes superimposition were used in Principal Component Analysis (PCA). Wing size and shape variations among populations was explored by means of ANOVA. Wing centroid size was significantly different among T. sordida populations; specimens from Bahia (East) were larger than those of Mato Grosso do Sul (West). PCA based on wing shape variables showed low wing shape variability. These results reinforce previous data showing low genetic variability among T. sordida populations from Brazil. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Measurement of shape and deformation of insect wing

    Science.gov (United States)

    Yin, Duo; Wei, Zhen; Wang, Zeyu; Zhou, Changqiu

    2018-01-01

    To measure the shape and deformation of an insect wing, a scanning setup adopting laser triangulation and image matching was developed. Only one industry camera with two light sources was employed to scan the transparent insect wings. 3D shape and point to point full field deformation of the wings could be obtained even when the wingspan is less than 3 mm. The venation and corrugation could be significantly identified from the results. The deformation of the wing under pin loading could be seen clearly from the results as well. Calibration shows that the shape and deformation measurement accuracies are no lower than 0.01 mm. Laser triangulation and image matching were combined dexterously to adapt wings' complex shape, size, and transparency. It is suitable for insect flight research or flapping wing micro-air vehicle development.

  2. Behavior of nanoparticle clouds around a magnetized microsphere under magnetic and flow fields.

    Science.gov (United States)

    Magnet, C; Kuzhir, P; Bossis, G; Meunier, A; Nave, S; Zubarev, A; Lomenech, C; Bashtovoi, V

    2014-03-01

    When a micron-sized magnetizable particle is introduced into a suspension of nanosized magnetic particles, the nanoparticles accumulate around the microparticle and form thick anisotropic clouds extended in the direction of the applied magnetic field. This phenomenon promotes colloidal stabilization of bimodal magnetic suspensions and allows efficient magnetic separation of nanoparticles used in bioanalysis and water purification. In the present work, the size and shape of nanoparticle clouds under the simultaneous action of an external uniform magnetic field and the flow have been studied in detail. In experiments, a dilute suspension of iron oxide nanoclusters (of a mean diameter of 60 nm) was pushed through a thin slit channel with the nickel microspheres (of a mean diameter of 50 μm) attached to the channel wall. The behavior of nanocluster clouds was observed in the steady state using an optical microscope. In the presence of strong enough flow, the size of the clouds monotonically decreases with increasing flow speed in both longitudinal and transverse magnetic fields. This is qualitatively explained by enhancement of hydrodynamic forces washing the nanoclusters away from the clouds. In the longitudinal field, the flow induces asymmetry of the front and the back clouds. To explain the flow and the field effects on the clouds, we have developed a simple model based on the balance of the stresses and particle fluxes on the cloud surface. This model, applied to the case of the magnetic field parallel to the flow, captures reasonably well the flow effect on the size and shape of the cloud and reveals that the only dimensionless parameter governing the cloud size is the ratio of hydrodynamic-to-magnetic forces-the Mason number. At strong magnetic interactions considered in the present work (dipolar coupling parameter α≥2), the Brownian motion seems not to affect the cloud behavior.

  3. Investigation of film flow of a conducting fluid in a transverse magnetic field, (1)

    International Nuclear Information System (INIS)

    Oshima, Shuzo; Yamane, Ryuichiro; Mochimaru, Yoshihiro; Sudo, Kouzo.

    1985-01-01

    Accompanying the development of large electromagnetic pumps transporting liquid metals used as the heat transfer media for nuclear power plants and the electromagnetic flow meters of large capacity, many researches have been carried out on the flow of liquid metals under the action of magnetic field. The utilization of electromagnetic force for continuous casting facilities seems very effective for the total processes from refining to solidification. Hereafter, it will be a technologically important problem to clarify the behavior of electro-conductive fluid with free surface under the action of magnetic field concerning the non-contact control of the interface form of molten metals as well as the cooling problem in nuclear fusion reactors. In this study, first the flow phenomena of MHD liquid film flow in a magnetic field with intensity gradient was analytically examined, and the effect of magnetic field gradient exerted on liquid film thickness and liquid surface form was clarified. Next, the experiment using mercury was carried out. For liquid film flow, magnetic field gradient acted as a kind of non-contact weir. (Kako, I.)

  4. Feasibility and accuracy assessment of light field (plenoptic) PIV flow-measurement technique

    Science.gov (United States)

    Shekhar, Chandra; Ogawa, Syo; Kawaguchi, Tatsuya

    A light field camera can enable measurement of all the three velocity components of a flow field inside a three-dimensional volume when implemented in a PIV measurement. Due to the usage of only one camera, the measurement procedure gets greatly simplified, as well as measurement of the flows with limited visual access also becomes possible. Due to these advantages, light field cameras and their usage in PIV measurements are actively studied. The overall procedure of obtaining an instantaneous flow field consists of imaging a seeded flow at two closely separated time instants, reconstructing the two volumetric distributions of the particles using algorithms such as MART, followed by obtaining the flow velocity through cross-correlations. In this study, we examined effects of various configuration parameters of a light field camera on the in-plane and the depth resolutions, obtained near-optimal parameters in a given case, and then used it to simulate a PIV measurement scenario in order to assess the reconstruction accuracy.

  5. Feasibility and accuracy assessment of light field (plenoptic PIV flow-measurement technique

    Directory of Open Access Journals (Sweden)

    Shekhar Chandra

    2017-01-01

    Full Text Available A light field camera can enable measurement of all the three velocity components of a flow field inside a three-dimensional volume when implemented in a PIV measurement. Due to the usage of only one camera, the measurement procedure gets greatly simplified, as well as measurement of the flows with limited visual access also becomes possible. Due to these advantages, light field cameras and their usage in PIV measurements are actively studied. The overall procedure of obtaining an instantaneous flow field consists of imaging a seeded flow at two closely separated time instants, reconstructing the two volumetric distributions of the particles using algorithms such as MART, followed by obtaining the flow velocity through cross-correlations. In this study, we examined effects of various configuration parameters of a light field camera on the in-plane and the depth resolutions, obtained near-optimal parameters in a given case, and then used it to simulate a PIV measurement scenario in order to assess the reconstruction accuracy.

  6. Numerical and experimental investigations on unsteady aerodynamics of flapping wings

    Science.gov (United States)

    Yu, Meilin

    the flow fields around a series of plunging NACA symmetric airfoils with thickness ratio ranging from 4.0% to 20.0% of the airfoil chord length. The contribution of viscous force to flapping propulsion is accessed and it is found that viscous force becomes thrust producing, instead of drag producing, and plays a non-negligible role in thrust generation for thin airfoils. This is closely related to the variations of the dynamics of the unsteady vortex structures around the plunging airfoils. As nature flyers use complex wing kinematics in flapping flight, kinematics effects on the aerodynamic performance with different airfoil thicknesses are numerically studied by using a series of NACA symmetric airfoils. It is found that the combined plunging and pitching motion can outperform the pure plunging or pitching motion by sophisticatedly adjusting the airfoil gestures during the oscillation stroke. The thin airfoil better manipulates leading edge vortices (LEVs) than the thick airfoil (NACA0030) does in studied cases, and there exists an optimal thickness for large thrust generation with reasonable propulsive efficiency. With the present kinematics and dynamic parameters, relatively low reduced frequency is conducive for thrust production and propulsive efficiency for all tested airfoil thicknesses. In order to obtain the optimal kinematics parameters of flapping flight, a kinematics optimization is then performed. A gradient-based optimization algorithm is coupled with a second-order SD Navier-Stokes solver to search for the optimal kinematics of a certain airfoil undergoing a combined plunging and pitching motion. Then a high-order SD scheme is used to verify the optimization results and reveal the detailed vortex structures associated with the optimal kinematics of the flapping flight. It is found that for the case with maximum propulsive efficiency, there exists no leading edge separation during most of the oscillation cycle. In order to provide constructive

  7. On the role of neutral flow in field-aligned currents

    Directory of Open Access Journals (Sweden)

    A. J. Mannucci

    2018-01-01

    Full Text Available In this brief note we explore the role of the neutral atmosphere in magnetosphere–ionosphere coupling. We analyze momentum balance in the ion rest frame to form hypotheses regarding the role of neutral momentum in the lower ionosphere during geomagnetic storms. Neutral momentum that appears in the ion rest frame is likely the result of momentum imparted to ionospheric ions by solar wind flow and the resultant magnetospheric dynamics. The resulting ion-neutral collisions lead to the existence of an electric field. Horizontal electron flow balances the momentum supplied by this electric field. We suggest a possible role played by the neutral atmosphere in generating field-aligned currents due to local auroral heating. Our physical interpretation suggests that thermospheric neutral dynamics plays a complementary role to the high-latitude field-aligned currents and electric fields resulting from magnetospheric dynamics.

  8. Fluid Flow and Solidification Under Combined Action of Magnetic Fields and Microgravity

    Science.gov (United States)

    Li, B. Q.; Shu, Y.; Li, K.; deGroh, H. C.

    2002-01-01

    Mathematical models, both 2-D and 3-D, are developed to represent g-jitter induced fluid flows and their effects on solidification under combined action of magnetic fields and microgravity. The numerical model development is based on the finite element solution of governing equations describing the transient g-jitter driven fluid flows, heat transfer and solutal transport during crystal growth with and without an applied magnetic field in space vehicles. To validate the model predictions, a ground-based g-jitter simulator is developed using the oscillating wall temperatures where timely oscillating fluid flows are measured using a laser PIV system. The measurements are compared well with numerical results obtained from the numerical models. Results show that a combined action derived from magnetic damping and microgravity can be an effective means to control the melt flow and solutal transport in space single crystal growth systems.

  9. Mixed Finite Element Formulation for Magnetic Fluid Oil Flow in Electromagnetic Field

    Directory of Open Access Journals (Sweden)

    Tan Phey Hoon

    2017-01-01

    Full Text Available Pressure depletion and high viscosity of crude oil in oil reservoir are the main challenges in oil recovery process. A potential solution is to employ electromagnetic heating coupled with magnetic fluid injection. The present work delivers a fundamental study on the interaction between magnetic fluid flow with electromagnetic field. The two-dimensional, incompressible flow is solved numerically using mixed finite element method. The velocity fields, temperature and pressure are the variables of interest, to be obtained by solving mass, momentum and energy equations coupled with Maxwell’ equations. The fluid stress arises simultaneously with the external magnetic force which mobilises and increases the temperature of the oil flow. Verification is made against available data obtained from different numerical method reported in literature. The results justify feasibility of the mixed finite element formulation as an alternative for the modelling of the magnetic fluid flow.

  10. Reproduction of pressure field in ultrasonic-measurement-integrated simulation of blood flow.

    Science.gov (United States)

    Funamoto, Kenichi; Hayase, Toshiyuki

    2013-07-01

    Ultrasonic-measurement-integrated (UMI) simulation of blood flow is used to analyze the velocity and pressure fields by applying feedback signals of artificial body forces based on differences of Doppler velocities between ultrasonic measurement and numerical simulation. Previous studies have revealed that UMI simulation accurately reproduces the velocity field of a target blood flow, but that the reproducibility of the pressure field is not necessarily satisfactory. In the present study, the reproduction of the pressure field by UMI simulation was investigated. The effect of feedback on the pressure field was first examined by theoretical analysis, and a pressure compensation method was devised. When the divergence of the feedback force vector was not zero, it influenced the pressure field in the UMI simulation while improving the computational accuracy of the velocity field. Hence, the correct pressure was estimated by adding pressure compensation to remove the deteriorating effect of the feedback. A numerical experiment was conducted dealing with the reproduction of a synthetic three-dimensional steady flow in a thoracic aneurysm to validate results of the theoretical analysis and the proposed pressure compensation method. The ability of the UMI simulation to reproduce the pressure field deteriorated with a large feedback gain. However, by properly compensating the effects of the feedback signals on the pressure, the error in the pressure field was reduced, exhibiting improvement of the computational accuracy. It is thus concluded that the UMI simulation with pressure compensation allows for the reproduction of both velocity and pressure fields of blood flow. Copyright © 2012 John Wiley & Sons, Ltd.

  11. Mean-field diffusivities in passive scalar and magnetic transport in irrotational flows

    Science.gov (United States)

    Rädler, Karl-Heinz; Brandenburg, Axel; Del Sordo, Fabio; Rheinhardt, Matthias

    2011-10-01

    Certain aspects of the mean-field theory of turbulent passive scalar transport and of mean-field electrodynamics are considered with particular emphasis on aspects of compressible fluids. It is demonstrated that the total mean-field diffusivity for passive scalar transport in a compressible flow may well be smaller than the molecular diffusivity. This is in full analogy to an old finding regarding the magnetic mean-field diffusivity in an electrically conducting turbulently moving compressible fluid. These phenomena occur if the irrotational part of the motion dominates the vortical part, the Péclet or magnetic Reynolds number is not too large, and, in addition, the variation of the flow pattern is slow. For both the passive scalar and the magnetic cases several further analytical results on mean-field diffusivities and related quantities found within the second-order correlation approximation are presented, as well as numerical results obtained by the test-field method, which applies independently of this approximation. Particular attention is paid to nonlocal and noninstantaneous connections between the turbulence-caused terms and the mean fields. Two examples of irrotational flows, in which interesting phenomena in the above sense occur, are investigated in detail. In particular, it is demonstrated that the decay of a mean scalar in a compressible fluid under the influence of these flows can be much slower than without any flow, and can be strongly influenced by the so-called memory effect, that is, the fact that the relevant mean-field coefficients depend on the decay rates themselves.

  12. Behavior of boundary string field theory associated with integrable massless flow.

    Science.gov (United States)

    Fujii, A; Itoyama, H

    2001-06-04

    We put forward an idea that the boundary entropy associated with integrable massless flow of thermodynamic Bethe ansatz (TBA) is identified with tachyon action of boundary string field theory. We show that the temperature parametrizing a massless flow in the TBA formalism can be identified with tachyon energy for the classical action at least near the ultraviolet fixed point, i.e., the open string vacuum.

  13. Local and Nonlocal Strain Rate Fields and Vorticity Alignment in Turbulent Flows

    OpenAIRE

    Hamlington, Peter E.; Schumacher, Jörg; Dahm, Werner J. A.

    2008-01-01

    Local and nonlocal contributions to the total strain rate tensor at any point in a flow are formulated from an expansion of the vorticity field in a local spherical neighborhood of radius R centered on x. The resulting exact expression allows the nonlocal (background) strain rate tensor to be obtained from the total strain rate tensor. In turbulent flows, where the vorticity naturally concentrates into relatively compact structures, this allows the local alignment of vorticity with the most e...

  14. Numerical and experimental investigation of the unsteady flow field over a simplified hydrofoil plate

    OpenAIRE

    Pislevikj, Jasmina

    2017-01-01

    In this thesis, the behavior of a simplified hydrofoil in an unsteady water flow field is tested. Due to frequent load variations in high head Francis turbines, the runner vanes happen to break. Rotor stator interaction causes vibrations on the runner vanes. To simulate those vibrations in laboratory conditions, the hydrofoil, mounted in a cascade test rig, is excited with piezo electric patches. The experiment in this thesis shows the behavior of the hydrofoil in different water flow velocit...

  15. Experimental investigation of flow field in a laboratory-scale compressor

    Directory of Open Access Journals (Sweden)

    Hongwei Ma

    2017-02-01

    Full Text Available The inner flow environment of turbomachinery presents strong three-dimensional, rotational, and unsteady characteristics. Consequently, a deep understanding of these flow phenomena will be the prerequisite to establish a state-of-the-art design system of turbomachinery. Currently the development of more accurate turbulence models and CFD tools is in urgent need for a high-quality database for validation, especially the advanced CFD tools, such as large eddy simulation (LES. Under this circumstance, this paper presents a detailed experimental investigation on the 3D unsteady flow field inside a laboratory-scale isolated-rotor with multiple advanced measurement techniques, including traditional aerodynamic probes, hotwire probes, unsteady endwall static pressure measurement, and stereo particle image velocimetry (SPIV. The inlet boundary layer profile is measured with both hotwire probe and aerodynamic probe. The steady and unsteady flow fields at the outlet of the rotor are measured with a mini five-hole probe and a single-slanted hotwire probe. The instantaneous flow field in the rotor tip region inside the passage is captured with SPIV, and then a statistical analysis of the spatial distribution of the instantaneous tip leakage vortex/flow is performed to understand its dynamic characteristics. Besides these, the uncertainty analysis of each measurement technique is described. This database is quite sufficient to validate the advanced numerical simulation with LES. The identification process of the tip leakage vortex core in the instantaneous frames obtained from SPIV is performed deliberately. It is concluded that the ensemble-averaged flow field could not represent the tip leakage vortex strength and the trajectory trace. The development of the tip leakage vortex could be clearly cataloged into three phases according to their statistical spatial distribution. The streamwise velocity loss induced by the tip leakage flow increases until the

  16. Interaction of counter-streaming plasma flows in dipole magnetic field

    OpenAIRE

    Shaikhislamov, I F; Posukh, V G; Melekhov, A V; Prokopov, P A; Boyarintsev, E L; Zakharov, Yu P; Ponomarenko, A G

    2017-01-01

    Transient interaction of counter-streaming super-sonic plasma flows in dipole magnetic dipole is studied in laboratory experiment. First quasi-stationary flow is produced by teta-pinch and forms a magnetosphere around the magnetic dipole while laser beams focused at the surface of the dipole cover launch second explosive plasma expanding from inner dipole region outward. Laser plasma is energetic enough to disrupt magnetic field and to sweep through the background plasma for large distances. ...

  17. A preliminary field study of patient flow management in a trauma center for designing information technology*

    OpenAIRE

    Gurses, Ayse P.; Hu, Peter; Gilger, Sheila; Dutton, Richard P.; Trainum, Therese; Ross, Kathy; Xiao, Yan

    2006-01-01

    We described the information transfer and communication activities of nurse coordinators (NCO), who lead patient flow management in a major trauma center. A field study was conducted to identify information sources and information tools used, leading purposes of communication, and the information types NCOs need for patient flow management. In addition to verbal communication, NCOs frequently used a combination of patient-oriented and process-oriented information tools.

  18. A visual description of the convective flow field around the heat of a human

    DEFF Research Database (Denmark)

    Özcan, Oktay; Meyer, Knud Erik; Melikov, Arsen Krikor

    2005-01-01

    Mean velocity data obtained by PIV (Particle Image Velocimetry) around the head of a real-life size breathing thermal manikin are presented for two cases of `no breathing' and `continuous exhalation through nose'. Experiments were conducted in a special chamber which provided stationary convectiv...... flows around the seated manikin. Results are limited to the plane of symmetry. The paper aims to describe the physical structure of the turbulent flow field by presenting velocity and vorticity data in color graphics....

  19. Laser transit anemometer measurements of a JANNAF nozzle base velocity flow field

    Science.gov (United States)

    Hunter, William W., Jr.; Russ, C. E., Jr.; Clemmons, J. I., Jr.

    1990-01-01

    Velocity flow fields of a nozzle jet exhausting into a supersonic flow were surveyed. The measurements were obtained with a laser transit anemometer (LTA) system in the time domain with a correlation instrument. The LTA data is transformed into the velocity domain to remove the error that occurs when the data is analyzed in the time domain. The final data is shown in velocity vector plots for positions upstream, downstream, and in the exhaust plane of the jet nozzle.

  20. Novel Applications of Magnetic Fields for Fluid Flow Control and for Simulating Variable Gravity Conditions

    Science.gov (United States)

    Ramachandran, N.

    2005-01-01

    Static and dynamic magnetic fields have been used to control convection in many materials processing applications. In most of the applications, convection control (damping or enhancement) is achieved through the Lorentz force that can be tailored to counteract/assist dominant system flows. This technique has been successfully applied to liquids that are electrically conducting, such as high temperature melts of semiconductors, metals and alloys, etc. In liquids with low electrical conductivity such as ionic solutions of salts in water, the Lorentz force is weak and hence not very effective and alternate ways of flow control are necessary. If the salt in solution is paramagnetic then the variation of magnetic susceptibility with temperature and/or concentration can be used for flow control. For thermal buoyancy driven flows this can be accomplished in a temperature range below the Curie point of the salt. The magnetic force is proportional to the magnetic susceptibility and the product of the magnetic field and its gradient. By suitably positioning the experiment cell in the magnet, system flows can be assisted or countered, as desired. A similar approach can be extended to diamagnetic substances and fluids but the required magnetic force is considerably larger than that required for paramagnetic substances. The presentation will provide an overview of work to date on a NASA fluid physics sponsored project that aims to test the hypothesis of convective flow control using strong magnetic fields in protein crystal growth. The objective is to understand the nature of the various forces that come into play, delineate causative factors for fluid flow and to quantify them through experiments, analysis, and numerical modeling. The seminar will report specifically on the experimental results using paramagnetic salts and solutions in magnetic fields and compare them to analytical predictions. Applications of the concept to protein crystallization studies will be discussed

  1. Theoretical background and the flow fields in downhole liquid-liquid hydrocyclone (LLHC

    Directory of Open Access Journals (Sweden)

    Osei Harrison

    2014-07-01

    Full Text Available Hydrocyclone system for downhole oil-water separation provides an effective technique of enhancing the economic viability of higher water-cut wells while at the same time reducing the risk of environmental pollution. This paper describes the hydrodynamics of the liquid-liquid hydrocyclones and the flow fields within it are paramount for achieving successful separation process. Some of the important hydrodynamic flow phenomenon within the liquid-liquid hydrocyclone and how they influence the separation efficiency of water/oil was analyzed through analytical solution. The properties of the liquids were based on Bayan offshore field measured properties. The results indicated that there are two swirling zones separated by stagnant flow field. The inner is the light liquid zone, while the outer is the heavy liquid zone.

  2. Computation and analysis of backward ray-tracing in aero-optics flow fields.

    Science.gov (United States)

    Xu, Liang; Xue, Deting; Lv, Xiaoyi

    2018-01-08

    A backward ray-tracing method is proposed for aero-optics simulation. Different from forward tracing, the backward tracing direction is from the internal sensor to the distant target. Along this direction, the tracing in turn goes through the internal gas region, the aero-optics flow field, and the freestream. The coordinate value, the density, and the refractive index are calculated at each tracing step. A stopping criterion is developed to ensure the tracing stops at the outer edge of the aero-optics flow field. As a demonstration, the analysis is carried out for a typical blunt nosed vehicle. The backward tracing method and stopping criterion greatly simplify the ray-tracing computations in the aero-optics flow field, and they can be extended to our active laser illumination aero-optics study because of the reciprocity principle.

  3. Full-Field Reconstruction of Structural Deformations and Loads from Measured Strain Data on a Wing Using the Inverse Finite Element Method

    Science.gov (United States)

    Miller, Eric J.; Manalo, Russel; Tessler, Alexander

    2016-01-01

    A study was undertaken to investigate the measurement of wing deformation and internal loads using measured strain data. Future aerospace vehicle research depends on the ability to accurately measure the deformation and internal loads during ground testing and in flight. The approach uses the inverse Finite Element Method (iFEM). The iFEM is a robust, computationally efficient method that is well suited for real-time measurement of real-time structural deformation and loads. The method has been validated in previous work, but has yet to be applied to a large-scale test article. This work is in preparation for an upcoming loads test of a half-span test wing in the Flight Loads Laboratory at the National Aeronautics and Space Administration Armstrong Flight Research Center (Edwards, California). The method has been implemented into an efficient MATLAB® (The MathWorks, Inc., Natick, Massachusetts) code for testing different sensor configurations. This report discusses formulation and implementation along with the preliminary results from a representative aerospace structure. The end goal is to investigate the modeling and sensor placement approach so that the best practices can be applied to future aerospace projects.

  4. Characteristics of magnetized plasma flow for helicity injection into reversed-field pinch

    Science.gov (United States)

    Suzuki, Shotaro; Asai, Tomohiko; Nagata, Masayoshi; Koguchi, Haruhisa; Hirano, Yoichi; Sakakita, Hajime; Kiyama, Satoru

    2007-11-01

    The magnetized plasma flow injection experiment has been performed on the large sized reversed-field pinch (RFP) device of TPE-RX. The magnetized plasma flow injection has been demonstrated to support RFP formation fueling and helicity injection. In the start-up experiment with the plasma flow injection, reduced density pump-out, loop voltage and Da emission have been observed clearly. Also the effect of plasma flow on the RFP with improved confinement by PPCD technique has been evaluated. To determine the efficiency of fueling and helicity injection, density, temperature and magnetic structure have been measured by using Langmuir and magnetic probe arrays.The series of experiments will show the magnetic structure and actual helicity and energy contents of injected magnetized plasma flow.

  5. Numerical analysis of the internal flow field in screw centrifugal blood pump based on CFD

    Science.gov (United States)

    Han, W.; Han, B. X.; Y Wang, H.; Shen, Z. J.

    2013-12-01

    As to the impeller blood pump, the high speed of the impeller, the local high shear force of the flow field and the flow dead region are the main reasons for blood damage. The screw centrifugal pump can effectively alleviate the problems of the high speed and the high shear stress for the impeller. The softness and non-destructiveness during the transfer process can effectively reduce the extent of the damage. By using CFD software, the characteristics of internal flow are analyzed in the screw centrifugal pump by exploring the distribution rules of the velocity, pressure and shear deformation rate of the blood when it flows through the impeller and the destructive effects of spiral blades on blood. The results show that: the design of magnetic levitation solves the sealing problems; the design of regurgitation holes solves the problem of the flow dead zone; the magnetic levitated microcirculation screw centrifugal pump can effectively avoid the vortex, turbulence and high shear forces generated while the blood is flowing through the pump. Since the distribution rules in the velocity field, pressure field and shear deformation rate of the blood in the blood pump are comparatively uniform and the gradient change is comparatively small, the blood damage is effectively reduced.

  6. Modeling of a pitching and plunging airfoil using experimental flow field and load measurements

    Science.gov (United States)

    Troshin, Victor; Seifert, Avraham

    2018-01-01

    The main goal of the current paper is to outline a low-order modeling procedure of a heaving airfoil in a still fluid using experimental measurements. Due to its relative simplicity, the proposed procedure is applicable for the analysis of flow fields within complex and unsteady geometries and it is suitable for analyzing the data obtained by experimentation. Currently, this procedure is used to model and predict the flow field evolution using a small number of low profile load sensors and flow field measurements. A time delay neural network is used to estimate the flow field. The neural network estimates the amplitudes of the most energetic modes using four sensory inputs. The modes are calculated using proper orthogonal decomposition of the flow field data obtained experimentally by time-resolved, phase-locked particle imaging velocimetry. To permit the use of proper orthogonal decomposition, the measured flow field is mapped onto a stationary domain using volume preserving transformation. The analysis performed by the model showed good estimation quality within the parameter range used in the training procedure. However, the performance deteriorates for cases out of this range. This situation indicates that, to improve the robustness of the model, both the decomposition and the training data sets must be diverse in terms of input parameter space. In addition, the results suggest that the property of volume preservation of the mapping does not affect the model quality as long as the model is not based on the Galerkin approximation. Thus, it may be relaxed for cases with more complex geometry and kinematics.

  7. Investigation of the internal behavior in segmented PEMFCs of different flow fields during cold start process

    International Nuclear Information System (INIS)

    Lin, R.; Ren, Y.S.; Lin, X.W.; Jiang, Z.H.; Yang, Z.; Chang, Y.T.

    2017-01-01

    In this study, we have researched the internal behavior in segmented proton exchange membrane fuel cells (PEMFCs) with three different flow fields during cold start process. The change of internal current density and temperature in fuel cells with different flow fields could be obviously shown by the printed circuit board (PCB) technology, and the study shows that the flow field is significant for enhancing the cold start ability and durability. Single serpentine flow field has the best cold start performance, while triple channel serpentine flow field has the best uniformity. It is found that without a robust temperature rising tendency, the cell temperature reaching 0 °C does not definitely mean a successful cold start because the cell temperature might drop down 0 °C again. Polarization curves show that there is almost no performance degradation after successful cold start, but the cell degrades quickly after the failed cold start at −7 °C and −10 °C. Based on these characteristics, we optimized the rapid cold start strategy by using electric heating and make it possible to start up the PEMFC at temperatures down to −20 °C within about 11 min. - Highlights: • Segmented fuel cell were used to record the internal current density and temperature distributions during the cold start. • The effects of flow fields on the PEMFC cold start capacity were evaluated. • The effect of cold start on the performance of fuel cell was evaluated. • An optimized strategy was adopted to improve the cold start capacity.

  8. Magnetic field effect on blood flow of Casson fluid in axisymmetric cylindrical tube: A fractional model

    International Nuclear Information System (INIS)

    Ali, Farhad; Sheikh, Nadeem Ahmad; Khan, Ilyas; Saqib, Muhammad

    2017-01-01

    The effects of magnetohydrodynamics on the blood flow when blood is represented as a Casson fluid, along with magnetic particles in a horizontal cylinder is studied. The flow is due to an oscillating pressure gradient. The Laplace and finite Hankel transforms are used to obtain the closed form solutions of the fractional partial differential equations. Effects of various parameters on the flow of both blood and magnetic particles are shown graphically. The analysis shows that, the model with fractional order derivatives bring a remarkable changes as compared to the ordinary model. The study highlights that applied magnetic field reduces the velocities of both the blood and magnetic particles.

  9. Magnetic field effect on blood flow of Casson fluid in axisymmetric cylindrical tube: A fractional model

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Farhad, E-mail: farhadaliecomaths@yahoo.com [Department of Mathematics, City University of Science and Information Technology, Peshawar 25000 (Pakistan); Sheikh, Nadeem Ahmad [Department of Mathematics, City University of Science and Information Technology, Peshawar 25000 (Pakistan); Khan, Ilyas [Basic Engineering Sciences Department, College of Engineering Majmaah University, Majmaah 11952 (Saudi Arabia); Saqib, Muhammad [Department of Mathematics, City University of Science and Information Technology, Peshawar 25000 (Pakistan)

    2017-02-01

    The effects of magnetohydrodynamics on the blood flow when blood is represented as a Casson fluid, along with magnetic particles in a horizontal cylinder is studied. The flow is due to an oscillating pressure gradient. The Laplace and finite Hankel transforms are used to obtain the closed form solutions of the fractional partial differential equations. Effects of various parameters on the flow of both blood and magnetic particles are shown graphically. The analysis shows that, the model with fractional order derivatives bring a remarkable changes as compared to the ordinary model. The study highlights that applied magnetic field reduces the velocities of both the blood and magnetic particles.

  10. Laser Anemometer Measurements of the Flow Field in a 4:1 Pressure Ratio Centrifugal Impeller

    Science.gov (United States)

    Skoch, G. J.; Prahst, P. S.; Wernet, M. P.; Wood, J. R.; Strazisar, A. J.

    1997-01-01

    A laser-doppler anemometer was used to obtain flow-field velocity measurements in a 4:1 pressure ratio, 4.54 kg/s (10 lbm/s), centrifugal impeller, with splitter blades and backsweep, which was configured with a vaneless diffuser. Measured through-flow velocities are reported for ten quasi-orthogonal survey planes at locations ranging from 1% to 99% of main blade chord. Measured through-flow velocities are compared to those predicted by a 3-D viscous steady flow analysis (Dawes) code. The measurements show the development and progression through the impeller and vaneless diffuser of a through-flow velocity deficit which results from the tip clearance flow and accumulation of low momentum fluid centrifuged from the blade and hub surfaces. Flow traces from the CFD analysis show the origin of this deficit which begins to grow in the inlet region of the impeller where it is first detected near the suction surface side of the passage. It then moves toward the pressure side of the channel, due to the movement of tip clearance flow across the impeller passage, where it is cut by the splitter blade leading edge. As blade loading increases toward the rear of the channel the deficit region is driven back toward the suction surface by the cross-passage pressure gradient. There is no evidence of a large wake region that might result from flow separation and the impeller efficiency is relatively high. The flow field in this impeller is quite similar to that documented previously by NASA Lewis in a large low-speed backswept impeller.

  11. Flow characteristics and exchange in complex biological systems as observed by pulsed-field-gradient magnetic-resonance imaging

    NARCIS (Netherlands)

    Homan, N.; Venne, B.B.; As, van H.

    2010-01-01

    Water flow through model porous media was studied in the presence of surface relaxation, internal magnetic field inhomogeneities and exchange with stagnant water pools with different relaxation behavior, demonstrating how the apparent flow parameters average velocity, volume flow and flow conducting

  12. Unitarity Bounds and RG Flows in Time Dependent Quantum Field Theory

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xi; Horn, Bart; Silverstein, Eva; Torroba, Gonzalo; /Stanford U., ITP /Stanford U., Phys. Dept. /SLAC

    2012-04-05

    We generalize unitarity bounds on operator dimensions in conformal field theory to field theories with spacetime dependent couplings. Below the energy scale of spacetime variation of the couplings, their evolution can strongly affect the physics, effectively shifting the infrared operator scaling and unitarity bounds determined from correlation functions in the theory. We analyze this explicitly for large-N double-trace flows, and connect these to UV complete field theories. One motivating class of examples comes from our previous work on FRW holography, where this effect explains the range of flavors allowed in the dual, time dependent, field theory.

  13. 3D field induced collisionless zonal flow decay in tokamak plasmas

    Science.gov (United States)

    Choi, G. J.; Hahm, T. S.

    2018-02-01

    We perform a gyrokinetic study of 3D resonant magnetic perturbation (RMP) field effect on zonal flows in tokamak plasmas. The result indicates that energy-dependent secular radial drift of particles due to the tangential component (δ B_\\Vert ) of the RMP field induces a further long term algebraic decay of the Rosenbluth–Hinton (1998 Phys. Rev. Lett. 80 724) residual flow expected in an axisymmetric tokamak. This mechanism could be related to an increase of H-mode transition power threshold in the presence of RMP observed in many tokamak experiments.

  14. Sakiadis flow of Maxwell fluid considering magnetic field and convective boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Mustafa, M., E-mail: meraj-mm@hotmail.com [School of Natural Sciences (SNS), National University of Sciences and Technology (NUST), Islamabad 44000 (Pakistan); Khan, Junaid Ahmad [Research Centre for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), Islamabad 44000 (Pakistan); Hayat, T. [Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan); Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Alsaedi, A. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia)

    2015-02-15

    In this paper we address the flow of Maxwell fluid due to constantly moving flat radiative surface with convective condition. The flow is under the influence of non-uniform transverse magnetic field. The velocity and temperature distributions have been evaluated numerically by shooting approach. The solution depends on various interesting parameters including local Deborah number De, magnetic field parameter M, Prandtl number Pr and Biot number Bi. We found that variation in velocity with an increase in local Deborah number De is non-monotonic. However temperature is a decreasing function of local Deborah number De.

  15. Optimization of the Turbulence Model on Numerical Simulations of Flow Field within a Hydrocyclone

    Directory of Open Access Journals (Sweden)

    Yan Xu

    2015-01-01

    Full Text Available Reynolds Stress Model and Large Eddy Simulation are used to respectively perform numerical simulation for the flow field of a hydrocyclone. The three-dimensional hexahedral computational grids were generated. Turbulence intensity, vorticity, and the velocity distribution of different cross sections were gained. The velocity simulation results were compared with the LDV test results, and the results indicated that Large Eddy Simulation was more close to LDV experimental data. Large Eddy Simulation was a relatively appropriate method for simulation of flow field within a hydrocyclone.

  16. Examination of forced unsteady separated flow fields on a rotating wind turbine blade

    Energy Technology Data Exchange (ETDEWEB)

    Huyer, S [Univ. of Colorado, Boulder, CO (US)

    1993-04-01

    The wind turbine industry faces many problems regarding the construction of efficient and predictable wind turbine machines. Steady state, two-dimensional wind tunnel data are generally used to predict aerodynamic loads on wind turbine blades. Preliminary experimental evidence indicates that some of the underlying fluid dynamic phenomena could be attributed to dynamic stall, or more specifically to generation of forced unsteady separated flow fields. A collaborative research effort between the University of Colorado and the National Renewable Energy Laboratory was conducted to systematically categorize the local and global effects of three- dimensional forced unsteady flow fields.

  17. Determine of velocity field with PIV and CFD during the flow around of bridge piers

    Directory of Open Access Journals (Sweden)

    Picka D.

    2013-04-01

    Full Text Available The article describes the processing of specific junior research FAST-J-11-51/1456 which dealt with physical and CFD of the velocity field during the flow around of bridge piers. Physical modelling has been carried out in Laboratory of water management research in Institute of Water Structures in Brno University of Technology – Faculty of Civil Engineering. To measure of the velocity field in profile of bridge piers were used laser measuring method PIV (Particle Image Velocimetry. The results of PIV served as a basis for comparing experimental data with CFD results of this type of flow in the commercial software ANSYS CFX.

  18. Numerical Simulation of 3D Solid-Liquid Turbulent Flow in a Low Specific Speed Centrifugal Pump: Flow Field Analysis

    Directory of Open Access Journals (Sweden)

    Baocheng Shi

    2014-06-01

    Full Text Available For numerically simulating 3D solid-liquid turbulent flow in low specific speed centrifugal pumps, the iteration convergence problem caused by complex internal structure and high rotational speed of pump is always a problem for numeral simulation researchers. To solve this problem, the combination of three measures of dynamic underrelaxation factor adjustment, step method, and rotational velocity control means according to residual curves trends of operating parameters was used to improve the numerical convergence. Numeral simulation of 3D turbulent flow in a low specific speed solid-liquid centrifugal pump was performed, and the results showed that the improved solution strategy is greatly helpful to the numerical convergence. Moreover, the 3D turbulent flow fields in pumps have been simulated for the bottom ash-particles with the volume fraction of 10%, 20%, and 30% at the same particle diameter of 0.1 mm. The two-phase calculation results are compared with those of single-phase clean water flow. The calculated results gave the main region of the abrasion of the impeller and volute casing and improve the hydraulic design of the impeller in order to decrease the abrasion and increase the service life of the pump.

  19. Flapping wing aerodynamics: from insects to vertebrates.

    Science.gov (United States)

    Chin, Diana D; Lentink, David

    2016-04-01

    More than a million insects and approximately 11,000 vertebrates utilize flapping wings to fly. However, flapping flight has only been studied in a few of these species, so many challenges remain in understanding this form of locomotion. Five key aerodynamic mechanisms have been identified for insect flight. Among these is the leading edge vortex, which is a convergent solution to avoid stall for insects, bats and birds. The roles of the other mechanisms - added mass, clap and fling, rotational circulation and wing-wake interactions - have not yet been thoroughly studied in the context of vertebrate flight. Further challenges to understanding bat and bird flight are posed by the complex, dynamic wing morphologies of these species and the more turbulent airflow generated by their wings compared with that observed during insect flight. Nevertheless, three dimensionless numbers that combine key flow, morphological and kinematic parameters - the Reynolds number, Rossby number and advance ratio - govern flapping wing aerodynamics for both insects and vertebrates. These numbers can thus be used to organize an integrative framework for studying and comparing animal flapping flight. Here, we provide a roadmap for developing such a framework, highlighting the aerodynamic mechanisms that remain to be quantified and compared across species. Ultimately, incorporating complex flight maneuvers, environmental effects and developmental stages into this framework will also be essential to advancing our understanding of the biomechanics, movement ecology and evolution of animal flight. © 2016. Published by The Company of Biologists Ltd.

  20. Antenna diagnostics for power flow in extreme near-field of a standard gain horn

    DEFF Research Database (Denmark)

    Popa, Paula Irina; Breinbjerg, Olav

    2016-01-01

    The plane wave spectrum of an aperture antenna can be calculated from a complex measurement of the radiated near- or far-field and it facilitates antenna diagnostics for the extreme near-field of the antenna. While antenna diagnostics often concerns the magnitude of the co-polar field, the plane...... wave spectrum actually allows for determination of both magnitude and phase of all three components of the electric as well as the magnetic field - and thus also the Poynting vector. In this work we focus on the Poynting vector and thus the power flow in the extreme near-field; as an example we employ...... that these oscillations are not merely a “Gibbs-like” phenomenon due to the availability of only the visible region of the plane wave spectrum and they are not caused by multiple reflections between the horn and the near-field probe - but resulted from the interference between the direct field and the edge...

  1. Development and Testing of an Unconventional Morphing Wing Concept with Variable Chord and Camber

    NARCIS (Netherlands)

    Keidel, D.H.K.; Sodja, J.; Werter, N.P.M.; De Breuker, R.; Ermanni, P.; Monajjemi, M.; Liang, W.

    2015-01-01

    Driven by the need to improve the performance and energy-efficiency of aircraft, current research in the field of morphing wings is growing in significance. The most recently developed concepts typically adjust only one characteristic of the wing. Within this paper a new concept for morphing wings

  2. Artificial blood-flow controlling effects of inhomogeneity of twisted magnetic fields

    International Nuclear Information System (INIS)

    Nakagawa, Hidenori; Ohuchi, Mikio

    2017-01-01

    We developed a blood-flow controlling system using magnetic therapy for some types of nervous diseases. In our research, we utilized overlapped extremely low frequency (ELF) fields for the most effective blood-flow for the system. Results showed the possibility that the inhomogeneous region obtained by overlapping the fields at 50 Hz, namely, a desirably twisted field revealed a significant difference in induced electromotive forces at the insertion points of electrodes. In addition, ELF exposures with a high inhomogeneity of the twisted field at 50 Hz out of phase were more effective in generating an induced electromotive difference by approximately 31%, as contrasted with the difference generated by the exposure in phase. We expect that the increase of the inhomogeneity of the twisted field around a blood vessel can produce the most effective electromotive difference in the blood, and also moderately affect the excitable cells relating to the autonomic nervous system for an outstanding blood-flow control in vivo. - Highlights: • The principal aim of this research is to contribute to the utilization of the twisted fields for the most effective blood-flow in vivo. • Two newly designed coil systems were used for producing a desirably twisted magnetic field under the measuring domain in the flow channel. • Further, we investigated the magnetohydrodynamic efficiencies of a prototype of a magnetic device, which was converted from use as a commercial alternating magnetic therapy apparatus. • The system was well-constructed with a successful application of a plural exposure coil; therefore, we were able to detect a maximum of induced electromotive force in a fluid of an artificial solution as a substitute for blood. • This new finding demonstrates that the process of blood massotherapy by magnetic stimuli is a therapy for many diseases.

  3. Artificial blood-flow controlling effects of inhomogeneity of twisted magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, Hidenori, E-mail: hnakagawa-tdt@umin.ac.jp; Ohuchi, Mikio

    2017-06-01

    We developed a blood-flow controlling system using magnetic therapy for some types of nervous diseases. In our research, we utilized overlapped extremely low frequency (ELF) fields for the most effective blood-flow for the system. Results showed the possibility that the inhomogeneous region obtained by overlapping the fields at 50 Hz, namely, a desirably twisted field revealed a significant difference in induced electromotive forces at the insertion points of electrodes. In addition, ELF exposures with a high inhomogeneity of the twisted field at 50 Hz out of phase were more effective in generating an induced electromotive difference by approximately 31%, as contrasted with the difference generated by the exposure in phase. We expect that the increase of the inhomogeneity of the twisted field around a blood vessel can produce the most effective electromotive difference in the blood, and also moderately affect the excitable cells relating to the autonomic nervous system for an outstanding blood-flow control in vivo. - Highlights: • The principal aim of this research is to contribute to the utilization of the twisted fields for the most effective blood-flow in vivo. • Two newly designed coil systems were used for producing a desirably twisted magnetic field under the measuring domain in the flow channel. • Further, we investigated the magnetohydrodynamic efficiencies of a prototype of a magnetic device, which was converted from use as a commercial alternating magnetic therapy apparatus. • The system was well-constructed with a successful application of a plural exposure coil; therefore, we were able to detect a maximum of induced electromotive force in a fluid of an artificial solution as a substitute for blood. • This new finding demonstrates that the process of blood massotherapy by magnetic stimuli is a therapy for many diseases.

  4. Improvement of Separation of Polystyrene Particles with PAN Membranes in Hollow Fiber Flow Field-Flow Fractionation

    International Nuclear Information System (INIS)

    Shin, Se Jong; Chung, Hyun Joo; Min, Byoung Ryul; Park, Jin Won; An, Ik Sung; Lee, Kang Taek

    2003-01-01

    Hollow Fiber flow field-flow fractionation (HF-FlFFF) has been tested in polyacrylonitrile (PAN) membrane channel in order to compare it with polysulfone (PSf) membrane channel. It has been experimentally shown that the separation time of 0.05-0.304 μm polystyrene latex (PSL) standards in PAN membrane channel is shorter than that in PSf channel by approximately 65%. The optimized separation condition in PAN membrane is V out / V rad = 1.4/0.12 mL/min, which is equal to the condition in PSf membrane channel. In addition both the resolution (Rs) and plate height (H) in PAN membrane channel are better than that in PSf membrane channel. The membrane radius was obtained by back calculation with retention time. It shows that the PSf membrane is expanded by swelling and pressure, but the PAN membrane doesn't expand by swelling and pressure

  5. Flow field velocity measurements for non-isothermal systems. [of chemically reactive flow inside fused silica CVD reactor vessels

    Science.gov (United States)

    Johnson, E. J.; Hyer, P. V.; Culotta, P. W.; Clark, I. O.

    1991-01-01

    Experimental techniques which can be potentially utilized to measure the gas velocity fields in nonisothermal CVD systems both in ground-based and space-based investigations are considered. The advantages and disadvantages of a three-component laser velocimetry (LV) system that was adapted specifically for quantitative determination of the mixed convective flows in a chamber for crystal growth and film formation by CVD are discussed. Data from a horizontal research CVD reactor indicate that current models for the effects of thermophoretic force are not adequate to predict the thermophoretic bias in arbitrary flow configurations. It is concluded that LV techniques are capable of characterizing the fluid dynamics of a CVD reactor at typical growth temperatures. Thermal effects are shown to dominate and stabilize the fluid dynamics of the reactor. Heating of the susceptor increases the gas velocities parallel to the face of a slanted susceptor by up to a factor of five.

  6. Temporal variability of colloidal material in agricultural storm runoff from managed grassland using flow field-flow fractionation.

    Science.gov (United States)

    Gimbert, Laura J; Worsfold, Paul J

    2009-12-25

    This paper reports the use of flow field-flow fractionation (FlFFF) to determine the temporal variability of colloidal (material in the runoff analysed by FlFFF. The technique had sufficient sensitivity to determine directly the changing colloidal profile over the 0.08-1.0mum size range in the runoff waters during these storm events. Rainfall, total phosphorus and suspended solids in the bulk runoff samples were also determined throughout one storm and showed significant correlation (Pmaterial. Whilst there are some uncertainties in the resolution and absolute calibration of the FlFFF profiles, the technique has considerable potential for the quantification of colloidal material in storm runoff waters.

  7. Cardiovascular fluid dynamics. Methods for flow and pressure field analysis from magnetic resonance imaging

    International Nuclear Information System (INIS)

    Ebbers, T.

    2001-01-01

    Cardiovascular blood flow is highly complex and incompletely understood. Blood flow patterns are expected to influence the opening and closing of normal and prosthetic heart valves, the efficiency of cardiac filling and ejection, and the resistance to thrombus formation within the heart. Conventional diagnostic techniques are poorly suited to the study of the three-dimensional (3D) blood flow patterns in the heart chambers and large vessels. Noninvasive methods have also been inadequate in studying intracardiac pressure differences, which are the driving force of flow and are critical in the evaluation of many cardiovascular abnormalities. This thesis focuses on the development of non-invasive methods for analysis of 3D cardiovascular blood flow. Simultaneous study of cardiovascular fluid dynamics allowed knowledge exchange across the two disciplines, facilitating the development process and broadening the applicability of the methods. A time-resolved 3D phase-contrast Magnetic Resonance Imaging (MRI) technique was used to acquire the velocity vector field in a 3D volume encompassing the entire heart or a large vessel. Cardiovascular blood flow patterns were visualized by use of particle traces, which revealed, for instance, vortical flow patterns in the left atrium. By applying the Navier-Stokes equation along a user-defined line in the 3D velocity vector field, the relative pressure could be obtained as an excellent supplement to the flow pattern visualization. Using a delineation of the blood pool, the time-varying 3D relative pressure field in the human left ventricle was obtained from the velocity field by use of the pressure Poisson equation. A delineation of the heart muscle, a task that is almost impossible to perform on 3D MRI either automatically or manually, was also achieved by usage of particle traces. This segmentation allows automatic calculation of the 3D relative pressure field, as well as calculation of well-established parameters such as

  8. The Payun-Matru lava field: a source of analogues for Martian long lava flows

    Science.gov (United States)

    Giacomini, L.; Pasquarè, G.; Massironi, M.; Frigeri, A.; Bistacchi, A.; Frederico, C.

    2007-08-01

    The Payun Matru Volcanic complex is a Quaternary fissural structure belonging to the back-arc extensional area of the Andes in the Mendoza Province (Argentina). The eastern portion of the volcanic structure is covered by a basaltic field of pahoehoe lava flows advanced over more than 180 km from the fissural feeding vents that are aligned with a E-W fault system (Carbonilla fault). Thanks to their widespread extension, these flows represent some of the largest lava flows in the world and the Pampas Onduladas flow can be considered the longest sub-aerial individual lava flow on the Earth surface [1,2]. These gigantic flows propagated over the nearly flat surface of the Pampean foreland, moving on a 0.3 degree slope. The very low viscosity of the olivine basalt lavas, coupled with the inflation process and an extensive system of lava tubes are the most probable explanation for their considerable length. The inflation process likely develop under a steady flow rate sustained for a long time [3]. A thin viscoelastic crust, built up at an early stage, is later inflated by the underlying fluid core, which remains hot and fluid thanks to the thermal-shield effect of the crust. The crust is progressively thickened by accretion from below and spreading is due to the continuous creation of new inflated lobes, which develop at the front of the flow. Certain morphological features are considered to be "fingerprints" of inflation [4, 5, 6]; these include tumuli, lava rises, lava lobes and ridges. All these morphologies are present in the more widespread Payun Matru lava flows that, where they form extensive sheetflows, can reach a maximum thickness of more than 20 meters. After the emplacement of the major flows, a second eruptive cycle involved the Payun Matru volcanic structure. During this stage thick and channelized flows of andesitic and dacitic lavas, accompanied the formation of two trachitic and trachiandesitic strato-volcanoes (Payun Matru and Payun Liso) culminated

  9. Conical quarl swirl stabilized non-premixed flames: flame and flow field interaction

    KAUST Repository

    Elbaz, Ayman M.

    2017-09-19

    The flame-flow field interaction is studied in non-premixed methane swirl flames stabilized in quartz quarl via simultaneous measurements of the flow field using a stereo PIV and OH-PLIF at 5 KHz repetition rate. Under the same swirl intensity, two flames with different fuel jet velocity were investigated. The time-averaged flow field shows a unique flow pattern at the quarl exit, where two recirculation vortices are formed; a strong recirculation zone formed far from the quarl exit and a larger recirculation zone extending inside the quarl. However, the instantaneous images show that, the flow pattern near the quarl exit plays a vital role in the spatial location and structure of the reaction zone. In the low fuel jet velocity flame, a pair of vortical structures, located precisely at the corners of the quarl exit, cause the flame to roll up into the central region of low speed flow, where the flame sheet then tracks the axial velocity fluctuations. The vorticity field reveals a vortical structure surrounding the reaction zones, which reside on a layer of low compressive strain adjacent to that vortical structure. In the high fuel jet velocity flame, initially a laminar flame sheet resides at the inner shear layer of the main jet, along the interface between incoming fresh gas and high temperature recirculating gas. Further downstream, vortex breakdown alters the flame sheet path toward the central flame region. The lower reaction zones show good correlation to the regions of maximum vorticity and track the regions of low compressive strain associated with the inner shear layer of the jet flow. In both flames the reactions zones conform the passage of the large structure while remaining inside the low speed regions or at the inner shear layer.

  10. Shock tunnel measurements of surface pressures in shock induced separated flow field using MEMS sensor array

    International Nuclear Information System (INIS)

    Sriram, R; Jagadeesh, G; Ram, S N; Hegde, G M; Nayak, M M

    2015-01-01

    Characterized not just by high Mach numbers, but also high flow total enthalpies—often accompanied by dissociation and ionization of flowing gas itself—the experimental simulation of hypersonic flows requires impulse facilities like shock tunnels. However, shock tunnel simulation imposes challenges and restrictions on the flow diagnostics, not just because of the possible extreme flow conditions, but also the short run times—typically around 1 ms. The development, calibration and application of fast response MEMS sensors for surface pressure measurements in IISc hypersonic shock tunnel HST-2, with a typical test time of 600 μs, for the complex flow field of strong (impinging) shock boundary layer interaction with separation close to the leading edge, is delineated in this paper. For Mach numbers 5.96 (total enthalpy 1.3 MJ kg −1 ) and 8.67 (total enthalpy 1.6 MJ kg −1 ), surface pressures ranging from around 200 Pa to 50 000 Pa, in various regions of the flow field, are measured using the MEMS sensors. The measurements are found to compare well with the measurements using commercial sensors. It was possible to resolve important regions of the flow field involving significant spatial gradients of pressure, with a resolution of 5 data points within 12 mm in each MEMS array, which cannot be achieved with the other commercial sensors. In particular, MEMS sensors enabled the measurement of separation pressure (at Mach 8.67) near the leading edge and the sharply varying pressure in the reattachment zone. (paper)

  11. Instantaneous flow field above the free end of finite-height cylinders and prisms

    International Nuclear Information System (INIS)

    Rostamy, N.; Sumner, D.; Bergstrom, D.J.; Bugg, J.D.

    2013-01-01

    Highlights: • PIV measurements of the flow above the free end of finite-height bodies. • Effect of cross-sectional shape of the models on the instantaneous flow. • Small-scale structures generated by the separated shear layer were revealed. • Effect of aspect ratio on the reattachment of the separated flow on the free end. -- Abstract: The flow above the free ends of surface-mounted finite-height circular cylinders and square prisms was studied experimentally using particle image velocimetry (PIV). Cylinders and prisms with aspect ratios of AR = 9, 7, 5, and 3 were tested at a Reynolds number of Re = 4.2 × 10 4 . The bodies were mounted normal to a ground plane and were partially immersed in a turbulent zero-pressure-gradient boundary layer, where the boundary layer thickness relative to the body width was δ/D = 1.6. PIV measurements were made above the free ends of the bodies in a vertical plane aligned with the flow centreline. The present PIV results provide insight into the effects of aspect ratio and body shape on the instantaneous flow field. The recirculation zone under the separated shear layer is larger for the square prism of AR = 3 compared to the more slender prism of AR = 9. Also, for a square prism with low aspect ratio (AR = 3), the influence of the reverse flow over the free end surface becomes more significant compared to that for a higher aspect ratio (AR = 9). For the circular cylinder, a cross-stream vortex forms within the recirculation zone. As the aspect ratio of the cylinder decreases, the reattachment point of the separated flow on the free end surface moves closer to the trailing edge. For both the square prism and circular cylinder cases, the instantaneous velocity vector field and associated in-plane vorticity field revealed small-scale structures mostly generated by the separated shear layer

  12. Wind Tunnel Investigation of Passive Vortex Control and Vortex-Tail Interactions on a Slender Wing at Subsonic and Transonic Speeds

    Science.gov (United States)

    Erickson, Gary E.

    2013-01-01

    A wind tunnel experiment was conducted in the NASA Langley 8-Foot Transonic Pressure Tunnel to determine the effects of passive porosity on vortex flow interactions about a slender wing configuration at subsonic and transonic speeds. Flow-through porosity was applied in several arrangements to a leading-edge extension, or LEX, mounted to a 65-degree cropped delta wing as a longitudinal instability mitigation technique. Test data were obtained with LEX on and off in the presence of a centerline vertical tail and twin, wing-mounted vertical fins to quantify the sensitivity of the aerodynamics to tail placement and orientation. A close-coupled canard was tested as an alternative to the LEX as a passive flow control device. Wing upper surface static pressure distributions and six-component forces and moments were obtained at Mach numbers of 0.50, 0.85, and 1.20, unit Reynolds number of 2.5 million, angles of attack up to approximately 30 degrees, and angles of sideslip to +/-8 degrees. The off-surface flow field was visualized in cross planes on selected configurations using a laser vapor screen flow visualization technique. Tunnel-to-tunnel data comparisons and a Reynolds number sensitivity assessment were also performed. 15.

  13. Magnetic field distribution in the plasma flow generated by a plasma focus discharge

    Energy Technology Data Exchange (ETDEWEB)

    Mitrofanov, K. N., E-mail: mitrofan@triniti.ru [Troitsk Institute for Innovaiton and Fusion Research (Russian Federation); Krauz, V. I., E-mail: krauz_vi@nrcki.ru; Myalton, V. V.; Velikhov, E. P.; Vinogradov, V. P.; Vinogradova, Yu. V. [National Research Centre Kurchatov Institute (Russian Federation)

    2014-11-15

    The magnetic field in the plasma jet propagating from the plasma pinch region along the axis of the chamber in a megajoule PF-3 plasma focus facility is studied. The dynamics of plasma with a trapped magnetic flow is analyzed. The spatial sizes of the plasma jet region in which the magnetic field concentrates are determined in the radial and axial directions. The magnetic field configuration in the plasma jet is investigated: the radial distribution of the azimuthal component of the magnetic field inside the jet is determined. It is shown that the magnetic induction vector at a given point in space can change its direction during the plasma flight. Conclusions regarding the symmetry of the plasma flow propagation relative to the chamber axis are drawn.

  14. Short revolving wings enable hovering animals to avoid stall and reduce drag

    Science.gov (United States)

    Lentink, David; Kruyt, Jan W.; Heijst, Gertjan F.; Altshuler, Douglas L.

    2014-11-01

    Long and slender wings reduce the drag of airplanes, helicopters, and gliding animals, which operate at low angle of attack (incidence). Remarkably, there is no evidence for such influence of wing aspect ratio on the energetics of hovering animals that operate their wings at much higher incidence. High incidence causes aircraft wings to stall, hovering animals avoid stall by generating an attached vortex along the leading edge of their wings that elevates lift. Hypotheses that explain this capability include the necessity for a short radial distance between the shoulder joint and wing tip, measured in chord lengths, instead of the long tip-to-tip distance that elevates aircraft performance. This stems from how hovering animals revolve their wings around a joint, a condition for which the precise effect of aspect ratio on stall performance is unknown. Here we show that the attachment of the leading edge vortex is determined by wing aspect ratio with respect to the center of rotation-for a suite of aspect ratios that represent both animal and aircraft wings. The vortex remains attached when the local radius is shorter than 4 chord lengths, and separates outboard on more slender wings. Like most other hovering animals, hummingbirds have wing aspect ratios between 3 and 4, much stubbier than helicopters. Our results show this makes their wings robust against flow separation, which reduces drag below values obtained with more slender wings. This revises our understanding of how aspect ratio improves performance at low Reynolds numbers.

  15. Measurement of circulation around wing-tip vortices and estimation of lift forces using stereo PIV

    Science.gov (United States)

    Asano, Shinichiro; Sato, Haru; Sakakibara, Jun

    2017-11-01

    Applying the flapping flight to the development of an aircraft as Mars space probe and a small aircraft called MAV (Micro Air Vehicle) is considered. This is because Reynolds number assumed as the condition of these aircrafts is low and similar to of insects and small birds flapping on the earth. However, it is difficult to measure the flow around the airfoil in flapping flight directly because of its three-dimensional and unsteady characteristics. Hence, there is an attempt to estimate the flow field and aerodynamics by measuring the wake of the airfoil using PIV, for example the lift estimation method based on a wing-tip vortex. In this study, at the angle of attack including the angle after stall, we measured the wing-tip vortex of a NACA 0015 cross-sectional and rectangular planform airfoil using stereo PIV. The circulation of the wing-tip vortex was calculated from the obtained velocity field, and the lift force was estimated based on Kutta-Joukowski theorem. Then, the validity of this estimation method was examined by comparing the estimated lift force and the force balance data at various angles of attack. The experiment results are going to be presented in the conference.

  16. Experimental study and comparison of various designs of gas flow fields to PEM fuel cells and cell stack performance

    Directory of Open Access Journals (Sweden)

    Hong eLiu

    2014-01-01

    Full Text Available In this study, a significant number of experimental tests to PEM fuel cells were conducted to investigate the effect of gas flow fields on fuel cell performance. Graphite plates with various flow field or flow channel designs, from literature survey and also novel designs by the authors, were used for the PEM fuel cell assembly. The fabricated fuel cells all have an effective membrane area of 23.5 cm2. The results showed that the serpentine flow channel design is still favorable, giving the best single fuel cell performance amongst all the studied flow channel designs. A novel symmetric serpentine flow field was proposed for relatively large size fuel cell application. Four fuel cell stacks each including four cells were assembled using different designs of serpentine flow channels. The output power performances of fuel cell stacks were compared and the novel symmetric serpentine flow field design is recommended for its very good performance.

  17. Breaking down the delta wing vortex: The role of vorticity in the breakdown process

    Science.gov (United States)

    Nelson, R. C.; Visser, Kenneth Dale

    1991-01-01

    Experimental x-wire measurements of the flowfield above a 70 degree and 75 degree flat plate delta wing were performed at a Reynolds number of 250,000. Grids were taken normal to the wing at various chordwise locations for angles of attack of 20 degrees and 30 degrees. Axial and azimuthal vorticity distributions were derived from the velocity fields. The dependence of circulation on distance from the vortex core and on chordwise location was also examined. The effects of nondimensionalization in comparison with other experimental data is made. The results indicate that the circulation distribution scales with the local semispan and grows in a nearly linear fashion in the chordwise direction. The spanwise distribution of axial vorticity is severely altered through the breakdown region and the amount of vorticity present appears to reach a maximum immediately preceding breakdown. The axial velocity components with a negative sense, such as that found in the secondary vortex, seem to remain unaffected by changes in wing sweep or angle of attack, in direct contrast to the visible components. In addition, the inclusion of the local wing geometry into a previously derived correlation parameter allows the circulation of growing leading edge vortex flows to be reduced to a single curve.

  18. Design, fabrication and testing of an air-breathing micro direct methanol fuel cell with compound anode flow field

    Science.gov (United States)

    Wang, Luwen; Zhang, Yufeng; Zhao, Youran; An, Zijiang; Zhou, Zhiping; Liu, Xiaowei

    2011-10-01

    An air-breathing micro direct methanol fuel cell (μDMFC) with a compound anode flow field structure (composed of the parallel flow field and the perforated flow field) is designed, fabricated and tested. To better analyze the effect of the compound anode flow field on the mass transfer of methanol, the compound flow field with different open ratios (ratio of exposure area to total area) and thicknesses of current collectors is modeled and simulated. Micro process technologies are employed to fabricate the end plates and current collectors. The performances of the μDMFC with a compound anode flow field are measured under various operating parameters. Both the modeled and the experimental results show that, comparing the conventional parallel flow field, the compound one can enhance the mass transfer resistance of methanol from the flow field to the anode diffusion layer. The results also indicate that the μDMFC with an anode open ratio of 40% and a thickness of 300 µm has the optimal performance under the 7 M methanol which is three to four times higher than conventional flow fields. Finally, a 2 h stability test of the μDMFC is performed with a methanol concentration of 7 M and a flow velocity of 0.1 ml min-1. The results indicate that the μDMFC can work steadily with high methanol concentration.

  19. Large Eddy Simulation of turbulent flow fields over three- dimensional alluvial dunes

    Science.gov (United States)

    Hardy, R. J.; Parsons, D. R.; Best, J.; Reesink, A. J. H.; Ockelford, A.

    2016-12-01

    Flow over fluvial dunes has been extensively studied and there is general understanding of the nature of the flow field over two dimensional dunes under equilibrium flow conditions. However, fluvial systems typically experience unsteady flow and therefore the sediment-water interface is constantly reorganizing to form complex three-dimensional morphologies (ripples, dunes and bar forms). Here we report on a numerical experiment which predicts flow over three dimensional dunes using Large Eddy Simulation (LES). Bed topography generated through flume experiments, where fine sand was water worked under a range of unsteady hydraulic conditions to generate quasi-equilibrium three dimensional bed forms, was measured with terrestrial LiDAR to create digital elevation models. This topography was then incorporated into a LES model, with a wall-adapting local eddy-viscosity turbulence model, through a Mass Flux Scaling algorithm, to generate three dimensional, high resolution space time prediction of flow over naturally formed dunes. The numerically predicted flows were analysed by standard Reynolds decomposition approaches, Eulerian and Lagrangian coherent flow structure identification methods and proper orthogonal decomposition. The results show that superimposed bed forms can cause changes in the nature of the classical separated flow regions and turbulence field. In particular, the number of locations where vortices are shed increase which causes coalescence of vortices. This increases the rate of transfer of turbulent kinetic energy into smaller scales. This has significant implications for the time dependent prediction of shear stress and as such for sediment transport dynamics which are required for an improved process understanding of three-dimensional bed form adjustment.

  20. Effects of Wing-Cuff on NACA 23015 Aerodynamic Performances

    Directory of Open Access Journals (Sweden)

    Meftah S.M.A

    2014-03-01

    Full Text Available The main subject of this work is the numerical study control of flow separation on a NACA 23015 airfoil by using wing cuff. This last is a leading edge modification done to the wing. The modification consists of a slight extension of the chord on the outboard section of the wings. Different numerical cases are considered for the baseline and modified airfoil NACA 23015 according at different angle of incidence. The turbulence is modeled by two equations k-epsilon model. The results of this numerical investigation showed several benefits of the wing cuff compared with a conventional airfoil and an agreement is observed between the experimental data and the present study. The most intriguing result of this research is the capability for wing cuff to perform short take-offs and landings.

  1. Chaotic dynamics of the magnetic field generated by dynamo action in a turbulent flow

    Energy Technology Data Exchange (ETDEWEB)

    Petrelis, F; Fauve, S [Laboratoire de Physique Statistique, CNRS UMR 8550, Ecole Normale Superieure, 24 rue Lhomond, F-75005 Paris (France)], E-mail: petrelis@lps.ens.fr

    2008-12-10

    We present models related to the results of a recent experiment (the 'VKS experiment') showing the generation of a magnetic field by a fully turbulent flow of liquid sodium. We first discuss the geometry of the mean magnetic field when the two coaxial impellers driving the flow counter-rotate at the same frequency. We then show how we expect this geometry to be modified when the impellers rotate at different frequencies. We also show that, in the latter case, dynamical regimes of the magnetic field can be easily understood from the interaction of modes with dipolar (respectively quadrupolar) symmetry. In particular, this interaction generates magnetic field reversals that have been observed in the experiment and display a hierarchy of timescales similar to the Earth's magnetic field: the duration of the steady phases is widely distributed, but is always much longer than the time needed to switch polarity. In addition to reversals, several other large scale features of the generated magnetic field are obtained when varying the governing parameters of the flow. These results are also understood in the framework of the same model.

  2. Numerical analysis of non-Newtonian rheology effect on hydrocyclone flow field

    Directory of Open Access Journals (Sweden)

    Lin Yang

    2015-03-01

    Full Text Available In view of the limitations of the existing Newton fluid effects on the vortex flow mechanism study, numerical analysis of non Newton fluid effects was presented. Using Reynolds stress turbulence model (RSM and mixed multiphase flow model (Mixture of FLUENT (fluid calculation software and combined with the constitutive equation of apparent viscosity of non-Newtonian fluid, the typical non-Newtonian fluid (drilling fluid, polymer flooding sewage and crude oil as medium and Newton flow field (water as medium were compared by quantitative analysis. Based on the research results of water, the effects of non-Newtonian rheology on the key parameters including the combined vortex motion index n and tangential velocity were analyzed. The study shows that: non-Newtonian rheology has a great effect on tangential velocity and n value, and tangential velocity decreases with non-Newtonian increasing. The three kinds of n values (constant segment are: 0.564(water, 0.769(polymer flooding sewage, 0.708(drilling fluid and their variation amplitudes are larger than Newtonian fluid. The same time, non-Newtonian rheology will lead to the phenomenon of turbulent drag reduction in the vortex flow field. Compared with the existing formula calculation results shown, the calculation result of non-Newtonian rheology is most consistent with the simulation result, and the original theory has large deviations. The study provides reference for theory research of non-Newtonian cyclone separation flow field.

  3. A new car-following model for autonomous vehicles flow with mean expected velocity field

    Science.gov (United States)

    Wen-Xing, Zhu; Li-Dong, Zhang

    2018-02-01

    Due to the development of the modern scientific technology, autonomous vehicles may realize to connect with each other and share the information collected from each vehicle. An improved forward considering car-following model was proposed with mean expected velocity field to describe the autonomous vehicles flow behavior. The new model has three key parameters: adjustable sensitivity, strength factor and mean expected velocity field size. Two lemmas and one theorem were proven as criteria for judging the stability of homogeneousautonomous vehicles flow. Theoretical results show that the greater parameters means larger stability regions. A series of numerical simulations were carried out to check the stability and fundamental diagram of autonomous flow. From the numerical simulation results, the profiles, hysteresis loop and density waves of the autonomous vehicles flow were exhibited. The results show that with increased sensitivity, strength factor or field size the traffic jam was suppressed effectively which are well in accordance with the theoretical results. Moreover, the fundamental diagrams corresponding to three parameters respectively were obtained. It demonstrates that these parameters play almost the same role on traffic flux: i.e. before the critical density the bigger parameter is, the greater flux is and after the critical density, the opposite tendency is. In general, the three parameters have a great influence on the stability and jam state of the autonomous vehicles flow.

  4. Unsteady flow field around a human hand and propulsive force in swimming.

    Science.gov (United States)

    Matsuuchi, K; Miwa, T; Nomura, T; Sakakibara, J; Shintani, H; Ungerechts, B E

    2009-01-05

    Much effort has been undertaken for the estimation of propulsive force of swimmers in the front crawl. Estimation is typically based on steady flow theory: the so-called quasi-steady analysis. Flow fields around a swimmer, however, are extremely unsteady because the change direction of hand produces unsteady vortex motions. To evaluate the force correctly, it is necessary to know the unsteady properties determined from the vortex dynamics because that unsteadiness is known to make the force greater. Unsteady flow measurements were made for this study using a sophisticated technique called particle image velocimetry (PIV) in several horizontal planes for subjects swimming in a flume. Using that method, a 100 time-sequential flow fields are obtainable simultaneously. Each flow field was calculated from two particle images using the cross-correlation method. The intensity of vortices and their locations were identified. A strong vortex was generated near the hand and then shed by directional change of the hand in the transition phase from in-sweep to out-sweep. When the vortex was shed, a new vortex rotating in the opposite direction around the hand was created. The pair of vortices induced the velocity component in the direction opposite to the swimming. Results of this study show that the momentum change attributable to the increase in this velocity component is the origin of thrust force by the hand.

  5. μ-PIV measurements of the ensemble flow fields surrounding a migrating semi-infinite bubble.

    Science.gov (United States)

    Yamaguchi, Eiichiro; Smith, Bradford J; Gaver, Donald P

    2009-08-01

    Microscale particle image velocimetry (μ-PIV) measurements of ensemble flow fields surrounding a steadily-migrating semi-infinite bubble through the novel adaptation of a computer controlled linear motor flow control system. The system was programmed to generate a square wave velocity input in order to produce accurate constant bubble propagation repeatedly and effectively through a fused glass capillary tube. We present a novel technique for re-positioning of the coordinate axis to the bubble tip frame of reference in each instantaneous field through the analysis of the sudden change of standard deviation of centerline velocity profiles across the bubble interface. Ensemble averages were then computed in this bubble tip frame of reference. Combined fluid systems of water/air, glycerol/air, and glycerol/Si-oil were used to investigate flows comparable to computational simulations described in Smith and Gaver (2008) and to past experimental observations of interfacial shape. Fluorescent particle images were also analyzed to measure the residual film thickness trailing behind the bubble. The flow fields and film thickness agree very well with the computational simulations as well as existing experimental and analytical results. Particle accumulation and migration associated with the flow patterns near the bubble tip after long experimental durations are discussed as potential sources of error in the experimental method.

  6. μ-PIV measurements of the ensemble flow fields surrounding a migrating semi-infinite bubble

    Science.gov (United States)

    Yamaguchi, Eiichiro; Smith, Bradford J.; Gaver, Donald P.

    2012-01-01

    Microscale particle image velocimetry (μ-PIV) measurements of ensemble flow fields surrounding a steadily-migrating semi-infinite bubble through the novel adaptation of a computer controlled linear motor flow control system. The system was programmed to generate a square wave velocity input in order to produce accurate constant bubble propagation repeatedly and effectively through a fused glass capillary tube. We present a novel technique for re-positioning of the coordinate axis to the bubble tip frame of reference in each instantaneous field through the analysis of the sudden change of standard deviation of centerline velocity profiles across the bubble interface. Ensemble averages were then computed in this bubble tip frame of reference. Combined fluid systems of water/air, glycerol/air, and glycerol/Si-oil were used to investigate flows comparable to computational simulations described in Smith and Gaver (2008) and to past experimental observations of interfacial shape. Fluorescent particle images were also analyzed to measure the residual film thickness trailing behind the bubble. The flow fields and film thickness agree very well with the computational simulations as well as existing experimental and analytical results. Particle accumulation and migration associated with the flow patterns near the bubble tip after long experimental durations are discussed as potential sources of error in the experimental method. PMID:23049158

  7. Measurement Part I: Flow Field at the Design Condition (Speed Ratio 0.6

    Directory of Open Access Journals (Sweden)

    Y. F. Liu

    2001-01-01

    Full Text Available The relative flow field in an automotive torque converter turbine was measured at three locations inside the passage (turbine 1/4 chord, mid-chord, and 4/4 chord using a highfrequency response rotating five-hole-probe. “Jet-Wake” flow structure was found in the turbine passage. Possible flow separation region was observed at the core/suction side at the turbine 1/4 chord and near the suction side at the turbine mid-chord. The mass averaged stagnation pressure drop is almost evenly distributed along the turbine flow path at the design condition (SR=0.6. The pressure drop due to centrifugal and Coriolis forces is found to be appreciable. The rotary stagnation pressure distribution indicates that there are higher losses at the first half of the turbine passage than at the second half. The major reasons for these higher losses and inefficiency are possible flow separation and a mismatch between the pump exit and the turbine inlet flow field. The fuel economy of a torque converter can be improved through redesign of the core region and by properly matching the pump and the turbine. The Part I of the paper deals with the design speed ratio (SR=0.6, and Part II deals with the off-design condition (SR=0.065 and the effects of speed ratio.

  8. Estimation of particle size based on LDV measurements in a de-accelerating flow field

    Science.gov (United States)

    Meyers, J. F.

    1985-01-01

    The accuracy of velocity measurements made with a laser velocimeter is strongly dependent upon the response of the seeding particles to the dynamics of the flow field. The smaller the particle the better the response to flow fluctuations and gradients and therefore the more accurate velocity measurement. In direct conflict is the requirement of light scattering efficiency to obtain signals with the laser velocimeter which, in general, is better as the particle size is increased. In low speed flow fields these two requirements on particle size overlap and accurate measurements may be obtained. However in high speed flows, where the velocity gradients may be severe, very small particles are required to maintain sufficient dynamic response characteristics to follow the flow. Therefore if velocity measurements are to be made in these flows, the laser velocimeter must be designed with sufficient sensitivity to obtain signals from these small particles. An insitu determination of the size distribution of kaolin particles (Al2O3, .2 + or - SiO2 . 2H2O) in the 16-foot Transonic Tunnel and the sensitivity characteristics of the laser velocimeter system is described.

  9. Magnetic field effect on a three-dimensional mixed convective flow ...

    African Journals Online (AJOL)

    An analytical solution to the problem of the MHD free and forced convection three dimensional flow of an incompressible viscous electrically conducting fluid with mass transfer along a vertical porous plate with transverse sinusoidal suction velocity is presented. A uniform magnetic field is assumed to be applied transversely ...

  10. Three-Dimensional Numerical Analysis of LOX/Kerosene Engine Exhaust Plume Flow Field Characteristics

    Directory of Open Access Journals (Sweden)

    Hong-hua Cai

    2017-01-01

    Full Text Available Aiming at calculating and studying the flow field characteristics of engine exhaust plume and comparative analyzing the effects of different chemical reaction mechanisms on the engine exhaust plume flow field characteristics, a method considering fully the combustion state influence is put forward, which is applied to exhaust plume flow field calculation of multinozzle engine. On this basis, a three-dimensional numerical analysis of the effects of different chemical reaction mechanisms on LOX/kerosene engine exhaust plume flow field characteristics was carried out. It is found that multistep chemical reaction can accurately describe the combustion process in the LOX/kerosene engine, the average chamber pressure from the calculation is 4.63% greater than that of the test, and the average chamber temperature from the calculation is 3.34% greater than that from the thermodynamic calculation. The exhaust plumes of single nozzle and double nozzle calculated using the global chemical reaction are longer than those using the multistep chemical reaction; the highest temperature and the highest velocity on the plume axis calculated using the former are greater than that using the latter. The important influence of chemical reaction mechanism must be considered in the study of the fixing structure of double nozzle engine on the rocket body.

  11. Flow dynamics at a river confluence on Mississippi River: field measurement and large eddy simulation

    Science.gov (United States)

    Le, Trung; Khosronejad, Ali; Bartelt, Nicole; Woldeamlak, Solomon; Peterson, Bonnie; Dewall, Petronella; Sotiropoulos, Fotis; Saint Anthony Falls Laboratory, University of Minnesota Team; Minnesota Department of Transportation Team

    2015-11-01

    We study the dynamics of a river confluence on Mississippi River branch in the city of Minneapolis, Minnesota, United States. Field measurements by Acoustic Doppler Current Profiler using on-board GPS tracking were carried out for five campaigns in the summer of 2014 and 2015 to collect both river bed elevation data and flow fields. Large Eddy Simulation is carried out to simulate the flow field with the total of 100 million grid points for the domain length of 3.2 km. The simulation results agree well with field measurements at measured cross-sections. The results show the existence of wake mode on the mixing interface of two branches near the upstream junction corner. The mutual interaction between the shear layers emanating from the river banks leading to the formation of large scale energetic structures that leads to ``switching'' side of the flow coherent structures. Our result here is a feasibility study for the use of eddy-resolving simulations in predicting complex flow dynamics in medium-size natural rivers. This work is funded by Minnesota Dept. Transportation and Minnesota Institute of Supercomputing.

  12. Characterization of Diamond Nanoparticles by High-Speed Micro-Thermal Field-Flow Fractionation

    Czech Academy of Sciences Publication Activity Database

    Janča, Josef

    2015-01-01

    Roč. 20, č. 8 (2015), s. 671-680 ISSN 1023-666X R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : diamond nanoparticles * high-speed microfluidic separation * micro-thermal field-flow fractionation, * article size distribution Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.515, year: 2015

  13. A Direct inverse model to determine permeability fields from pressure and flow rate measurements

    NARCIS (Netherlands)

    Brouwer, G.K.; Fokker, P.A.; Wilschut, F.; Zijl, W.

    2008-01-01

    The determination of the permeability field from pressure and flow rate measurements in wells is a key problem in reservoir engineering. This paper presents a Double Constraint method for inverse modeling that is an example of direct inverse modeling. The method is used with a standard

  14. Design of flow-field patterns for proton exchange membrane fuel cell application

    International Nuclear Information System (INIS)

    Rosli, M.I.; Wan Ramli Wan Daud; Kamaruzzaman Sopian; Jaafar Sahari

    2006-01-01

    Fuel cells are electrochemical devices that produce electricity at high efficiency without combustion. Fuel cells are emerging as viable candidates as power sources in many applications, including road vehicles, small-scale power stations, and possibly even portable electronics. This paper addresses the design of flow-field patterns for proton exchange membrane fuel cell (PEMFC). The PEMFC is a low-temperature fuel cell, in which a proton conductive polymer membrane is used as the electrolyte. In PEMFC, flow-field pattern is one important thing that effects the performance of PEMFC. This paper present three types of flow-field pattern that will be consider to be testing using CFD analysis and by experimental. The design look detail on to their shape and dimension to get the best pattern in term of more active electrode area compare to electrode area that will be used. Another advantage and disadvantage for these three type of flow-field patterns from literature also compared in this paper

  15. A new modified-serpentine flow field for application in high temperature polymer electrolyte fuel cell

    DEFF Research Database (Denmark)

    Singdeo, Debanand; Dey, Tapobrata; Gaikwad, Shrihari

    2017-01-01

    Flow field design for the distribution of reactants and products on the electrode surface plays an important role in the overall performance of the fuel cell. It acts as a crucial factor when the laboratory scale fuel cell is scaled up for commercial applications. In the present work, a novel flo...

  16. Improved real gas routines for Sandia's NASA Ames flow field program

    Energy Technology Data Exchange (ETDEWEB)

    Eaton, R.R.; Larson, D.E.

    1976-02-01

    The real gas subroutines in Sandia's version of the NASA Ames flow field code have been extensively revised. Using these modifications the required computer run time for a difficult high Mach number case has been reduced from 1330 seconds to 151 seconds. (auth)

  17. Lattice energy-momentum tensor from the Yang-Mills gradient flow -- inclusion of fermion fields

    OpenAIRE

    Makino, Hiroki; Suzuki, Hiroshi

    2014-01-01

    Local products of fields deformed by the so-called Yang--Mills gradient flow become renormalized composite operators. This fact has been utilized to construct a correctly normalized conserved energy--momentum tensor in the lattice formulation of the pure Yang--Mills theory. In the present paper, this construction is further generalized for vector-like gauge theories containing fermions.

  18. Numerical analysis of blood flow in realistic arteries subjected to strong non-uniform magnetic fields

    NARCIS (Netherlands)

    Kenjeres, S.

    2008-01-01

    The paper reports on a comprehensive mathematical model for simulations of blood flow under the presence of strong non-uniform magnetic fields. The model consists of a set of Navier–Stokes equations accounting for the Lorentz and magnetisation forces, and a simplified set of Maxwell’s equations

  19. Lava flow field emplacement studies of Manua Ulu (Kilauea Volcano, Hawai'i, United States) and Venus, using field and remote sensing analyses

    Science.gov (United States)

    Byrnes, Jeffrey Myer

    2002-04-01

    This work examines lava emplacement processes by characterizing surface units using field and remote sensing analyses in order to understand the development of lava flow fields. Specific study areas are the 1969--1974 Mauna Ulu compound flow field, (Kilauea Volcano, Hawai'i, USA), and five lava flow fields on Venus: Turgmam Fluctus, Zipaltonal Fluctus, the Tuli Mons/Uilata Fluctus flow complex, the Var Mons flow field, and Mylitta Fluctus. Lava surface units have been examined in the field and with visible-, thermal-, and radar-wavelength remote sensing datasets for Mauna Ulu, and with radar data for the Venusian study areas. For the Mauna Ulu flow field, visible characteristics are related to color, glass abundance, and dm- to m-scale surface irregularities, which reflect the lava flow regime, cooling, and modification due to processes such as coalescence and inflation. Thermal characteristics are primarily affected by the abundance of glass and small-scale roughness elements (such as vesicles), and reflect the history of cooling, vesiculation and degassing, and crystallization of the lava. Radar characteristics are primarily affected by unit topography and fracturing, which are related to flow inflation, remobilization, and collapse, and reflect the local supply of lava during and after unit emplacement. Mauna Ulu surface units are correlated with pre-eruption topography, lack a simple relationship to the main feeder lava tubes, and are distributed with respect to their position within compound flow lobes and with distance from the vent. The Venusian lava flow fields appear to have developed through emplacement of numerous, thin, simple and compound flows, presumably over extended periods of time, and show a wider range of radar roughness than is observed at Mauna Ulu. A potential correlation is suggested between flow rheology and surface roughness. Distributary flow morphologies may result from tube-fed flows, and flow inflation is consistent with observed

  20. Numerical analysis for the flow field past a two-staged conical orifice

    International Nuclear Information System (INIS)

    Kim, Yeon Soo; Kim, You Gon

    2001-01-01

    The objective of the paper was to measure the pressure drop and to investigate the recirculation region of the conical orifices used in Kwang-yang Iron and Steel Company. The flow field with water used as a working fluid was the turbulent flow for Reynolds number of 2x10 4 . The effective parameters for the pressure drop and the recirculation region were the conical orifice's inclined angle (θ) against the wall, the interval(L) between orifices, the relative angle of rotation(α) of the orifices, the shape of the orifice's hole(circle, rectangle, triangle) having the same area. It was found that the shape of the orifice's hold affected the pressure drop and the flow field a lot. But the other parameters did not make much differences to the pressure drop. The PISO algorithm with FLUENT code was employed

  1. A CFD Study on Inlet Plenum Flow Field of Pebble Bed Reactor

    International Nuclear Information System (INIS)

    Kim, Min Hwan; Lee, Won Jae; Chang, Jong Hwa

    2005-01-01

    High temperature gas cooled reactor, largely divided into two types of PBR (Pebble Bed Reactor) and PMR (Prismatic Modular Reactor), has becomes great interest of researchers in connection with the hydrogen production. KAERI has started a project to develop the gas cooled reactor for the hydrogen production and has been doing in-depth study for selecting the reactor type between PBR and PMR. As a part of the study, PBMR (Pebble Bed Modular Reactor) was selected as a reference PBR reactor for the CFD analysis and the flow field of its inlet plenum was simulated with computational fluid dynamics program CFX5. Due to asymmetrical arrangement of pipes to the inlet plenum, non-uniform flow distribution has been expected to occur, giving rise to non-uniform power distribution at the core. Flow fields of different arrangement of inlet pipes were also investigated, as one of measures to reduce the non-uniformity

  2. Advances in field-flow fractionation for the analysis of biomolecules: instrument design and hyphenation.

    Science.gov (United States)

    Schachermeyer, Samantha; Ashby, Jonathan; Zhong, Wenwan

    2012-09-01

    Field-flow fractionation (FFF) separates analytes by use of an axial channel-flow and a cross-field. Its soft separation capability makes it an ideal tool for initial fractionation of complex mixtures, but large elution volumes and high flow rates have limited its applicability without significant user handling. Recent advances in instrumentation and miniaturization have successfully reduced channel size and elution speed, and thus the volume of each fraction, making it possible to conveniently couple FFF with orthogonal separation techniques for improved resolution. More detailed analysis can also be performed on the fractions generated by FFF by use of diverse analytical techniques, including MS, NMR, and even X-ray scattering. These developmental trends have given FFF more power in the analysis of different types of molecule, and will be the direction of choice for further advances in FFF technology.

  3. Short-range dynamics and prediction of mesoscale flow patterns in the MISTRAL field experiment

    Energy Technology Data Exchange (ETDEWEB)

    Weber, R.O.; Kaufmann, P.; Talkner, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    In a limited area of about 50 km by 50 km with complex topography, wind measurements on a dense network were performed during the MISTRAL field experiment in 1991-1992. From these data the characteristic wind fields were identified by an automated classification method. The dynamics of the resulting twelve typical regional flow patterns is studied. It is discussed how transitions between the flow patterns take place and how well the transition probabilities can be described in the framework of a Markov model. Guided by this discussion, a variety of prediction models were tested which allow a short-term forecast of the flow pattern type. It is found that a prediction model which uses forecast information from the synoptic scale has the best forecast skill. (author) 2 figs., 7 refs.

  4. Background-oriented schlieren for the study of large flow fields

    Science.gov (United States)

    Trolinger, James D.; Buckner, Ben; L'Esperance, Drew

    2015-09-01

    Modern digital recording and processing techniques combined with new lighting methods and relatively old schlieren visualization methods move flow visualization to a new level, enabling a wide range of new applications and a possible revolution in the visualization of very large flow fields. This paper traces the evolution of schlieren imaging from Robert Hooke, who, in 1665, employed candles and lenses, to modern digital background oriented schlieren (BOS) systems, wherein image processing by computer replaces pure optical image processing. New possibilities and potential applications that could benefit from such a capability are examined. Example applications include viewing the flow field around full sized aircraft, large equipment and vehicles, monitoring explosions on bomb ranges, cooling systems, large structures and even buildings. Objectives of studies include aerodynamics, aero optics, heat transfer, and aero thermal measurements. Relevant digital cameras, light sources, and implementation methods are discussed.

  5. Application of Stochastic Unsaturated Flow Theory, Numerical Simulations, and Comparisons to Field Observations

    DEFF Research Database (Denmark)

    Jensen, Karsten Høgh; Mantoglou, Aristotelis

    1992-01-01

    A stochastic unsaturated flow theory and a numerical simulation model have been coupled in order to estimate the large-scale mean behavior of an unsaturated flow system in a spatially variable soil. On the basis of the theoretical developments of Mantoglou and Gelhar (1987a, b, c), the theory...... unsaturated flow equation representing the mean system behavior is solved using a finite difference numerical solution technique. The effective parameters are evaluated from the stochastic theory formulas before entering them into the numerical solution for each iteration. The stochastic model is applied...... to a field site in Denmark, where information is available on the spatial variability of soil parameters and variables. Numerical simulations have been carried out, and predictions of the mean behavior and the variance of the capillary tension head and the soil moisture content have been compared to field...

  6. Magnetohydrodynamic flow of generalized Maxwell fluids in a rectangular micropump under an AC electric field

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Guangpu [School of Mathematical Science, Inner Mongolia University, Hohhot, Inner Mongolia 010021 (China); Jian, Yongjun, E-mail: jianyj@imu.edu.cn [School of Mathematical Science, Inner Mongolia University, Hohhot, Inner Mongolia 010021 (China); Chang, Long [School of Mathematics and Statistics, Inner Mongolia University of Finance and Economics, Hohhot, Inner Mongolia 010051 (China); Buren, Mandula [School of Mathematical Science, Inner Mongolia University, Hohhot, Inner Mongolia 010021 (China)

    2015-08-01

    By using the method of separation of variables, an analytical solution for the magnetohydrodynamic (MHD) flow of the generalized Maxwell fluids under AC electric field through a two-dimensional rectangular micropump is reduced. By the numerical computation, the variations of velocity profiles with the electrical oscillating Reynolds number Re, the Hartmann number Ha, the dimensionless relaxation time De are studied graphically. Further, the comparison with available experimental data and relevant researches is presented. - Highlights: • MHD flow of the generalized Maxwell fluids under AC electric field is analyzed. • The MHD flow is confined to a two-dimensional rectangular micropump. • Analytical solution is obtained by using the method of separation of variables. • The influences of related parameters on the MHD velocity are discussed.

  7. Magnetohydrodynamic flow of generalized Maxwell fluids in a rectangular micropump under an AC electric field

    International Nuclear Information System (INIS)

    Zhao, Guangpu; Jian, Yongjun; Chang, Long; Buren, Mandula

    2015-01-01

    By using the method of separation of variables, an analytical solution for the magnetohydrodynamic (MHD) flow of the generalized Maxwell fluids under AC electric field through a two-dimensional rectangular micropump is reduced. By the numerical computation, the variations of velocity profiles with the electrical oscillating Reynolds number Re, the Hartmann number Ha, the dimensionless relaxation time De are studied graphically. Further, the comparison with available experimental data and relevant researches is presented. - Highlights: • MHD flow of the generalized Maxwell fluids under AC electric field is analyzed. • The MHD flow is confined to a two-dimensional rectangular micropump. • Analytical solution is obtained by using the method of separation of variables. • The influences of related parameters on the MHD velocity are discussed

  8. Effect of Axisymmetric Aft Wall Angle Cavity in Supersonic Flow Field

    Science.gov (United States)

    Jeyakumar, S.; Assis, Shan M.; Jayaraman, K.

    2018-03-01

    Cavity plays a significant role in scramjet combustors to enhance mixing and flame holding of supersonic streams. In this study, the characteristics of axisymmetric cavity with varying aft wall angles in a non-reacting supersonic flow field are experimentally investigated. The experiments are conducted in a blow-down type supersonic flow facility. The facility consists of a supersonic nozzle followed by a circular cross sectional duct. The axisymmetric cavity is incorporated inside the duct. Cavity aft wall is inclined with two consecutive angles. The performance of the aft wall cavities are compared with rectangular cavity. Decreasing aft wall angle reduces the cavity drag due to the stable flow field which is vital for flame holding in supersonic combustor. Uniform mixing and gradual decrease in stagnation pressure loss can be achieved by decreasing the cavity aft wall angle.

  9. Field data vs. modeling: influence of erosion on pyroclastic flow mobility

    Science.gov (United States)

    Bernard, Julien; Kelfoun, Karim; Le Pennec, Jean-Luc

    2013-04-01

    Studies of pyroclastic flow deposits on numerous volcanoes around the world (eg. Merapi, Ngauruhe, Lascar) strongly suggest that erosion processes occur during the flow emplacement itself. This incorporation of accidental material into a moving flow can dramatically modify its properties, such as mobility and velocity, and has to be taken into account for hazard assessment. In order to address this issue, we carried out fieldwork on pyroclastic density current (PDC) deposits from the 2006 paroxysm of Tungurahua volcano, Ecuador. We identified where the deposition from these PDCs began, in one of the gullies affected by the flows (the "Juive"). We then performed precise granulometric and componentry analysis using a series of six high resolution numerical images taken of outcrops from the upper, initial point of deposition through to the lower spreading zone of PDC deposits. Our preliminary results, extracted from 2D data, allow us to precisely quantify the proportions of both juvenile and accidental material in the deposits along the entire gully. We found constant proportions of accidental material -around 40 percent- in all of our samples, showing that erosion mainly occurs before deposition, on the upper slopes (>30°) of the volcano. We wrote theoretical equations to explore the effect of erosion on pyroclastic flow mobility. These equations are based on the balance of forces applied to a single particle of an erodible bed. We defined the time needed by a particle to leave its position in an eroded zone, allowing the erosion to subsequently remove lower particles from the substratum. Both Coulomb and Plastic rheology were investigated for the PDC. The resulting equations were integrated into a VolcFlow-based numerical model, and 2D simulations were performed on Tungurahua volcano, in the gully where the field data were collected. Comparisons between modeled flows and field data are very promising: modeled erosion only occurs on steep slopes, which is consistent

  10. Simulation of unsaturated flow and nonreactive solute transport in a heterogeneous soil at the field scale

    International Nuclear Information System (INIS)

    Rockhold, M.L.

    1993-02-01

    A field-scale, unsaturated flow and solute transport experiment at the Las Cruces trench site in New Mexico was simulated as part of a ''blind'' modeling exercise to demonstrate the ability or inability of uncalibrated models to predict unsaturated flow and solute transport in spatially variable porous media. Simulations were conducted using a recently developed multiphase flow and transport simulator. Uniform and heterogeneous soil models were tested, and data from a previous experiment at the site were used with an inverse procedure to estimate water retention parameters. A spatial moment analysis was used to provide a quantitative basis for comparing the mean observed and simulated flow and transport behavior. The results of this study suggest that defensible predictions of waste migration and fate at low-level waste sites will ultimately require site-specific data for model calibration

  11. Effect of magnetic field on Blasius and Sakiadis flow of nanofluids past an inclined plate

    Directory of Open Access Journals (Sweden)

    S.P. Anjali Devi

    2017-11-01

    Full Text Available A theoretical study on the effect of magnetic field on the classical Blasius and Sakiadis flow of nanofluids over an inclined plate is presented in this paper. The governing partial differential equations are converted into ordinary differential equations using suitable similarity transformations. The transformed boundary layer equations are solved numerically using MATLAB (bvp4c. Two types of nanoparticles are chosen namely copper and alumina in the base fluid of water with the Prandtl number (Pr = 6.2. The effects of the governing physical parameters over the velocity, temperature, skin friction coefficient and reduced Nusselt number for both the Blasius and Sakiadis flows are displayed graphically. The characteristics of physical and engineering interest are discussed in detail. Keywords: Nanofluid, Blasius flow, Sakiadis flow, MHD, Inclined plate, Mixed convection

  12. Computational Relativistic Astrophysics Using the Flow Field-Dependent Variation Theory

    Science.gov (United States)

    Richardson, G. A.; Chung, T. J.

    2002-01-01

    We present our method for solving general relativistic nonideal hydrodynamics. Relativistic effects become pronounced in such cases as jet formation from black hole magnetized accretion disks which may lead to the study of gamma-ray bursts. Nonideal flows are present where radiation, magnetic forces, viscosities, and turbulence play an important role. Our concern in this paper is to reexamine existing numerical simulation tools as to the accuracy and efficiency of computations and introduce a new approach known as the flow field-dependent variation (FDV) method. The main feature of the FDV method consists of accommodating discontinuities of shock waves and high gradients of flow variables such as occur in turbulence and unstable motions. In this paper, the physics involved in the solution of relativistic hydrodynamics and solution strategies of the FDV theory are elaborated. The general relativistic astrophysical flow and shock solver (GRAFSS) is introduced, and some simple example problems for computational relativistic astrophysics (CRA) are demonstrated.

  13. Flow field and load characteristics of the whole MEXICO wind turbine

    DEFF Research Database (Denmark)

    Xu, Haoran; Yang, Hua; Liu, Chao

    2017-01-01

    CFD(Computational Fluid Dynamics) method was used to perform steady numerical simulation investigation on the flow field and load characteristics of MEXICO(Model EXperiment In Controlled cOnditions) wind turbine under non-yawed condition. Circumferentially-Averaged method was used to extract...... the calculated axial, radial and tangential components of velocity along the axial direction, then these components were compared with the experimental data, the compared results show that the computational components agree well with the experimental data and the computational results are reliable. The flow...... characteristics around the blade was analyzed and the points of flow separation were found along the blade, the results show that the points of flow separation move towards trailing edge with the increase of radius. The distribution of vorticity in the wake of MEXICO rotor was also analyzed. The distribution...

  14. Single-well push-pull test in transient Forchheimer flow field

    Science.gov (United States)

    Wang, Quanrong; Zhan, Hongbin; Wang, Yanxin

    2017-06-01

    Using the single-well push-pull (SWPP) test to quantify in situ aquifer characteristics associated with solute transport (dispersion coefficient, geobiochemical reaction rates), the accuracy of parameter estimation was not only dependent on the solute transport models but also the groundwater flow models. However, many previous studies on the SWPP test were based on assumptions over-simplifying the flow field, namely, groundwater flow followed Darcy's law; flow was in the steady state during the entire test duration; the wellbore storage could be negligible. In this study, we have carefully examined such assumptions by developing a new finite-difference model of the SWPP test under the transient Forchheimer flow condition, considering the wellbore storage. The SWPP test included an injection phase, a chaser phase, a rest phase, and an extraction phase. The results showed that the concentration of the steady-state flow solution was greater than that of the transient flow solution at the beginning, and its peak value was also greater than that of the transient flow solution. The difference between the breakthrough curves (BTCs) of the transient flow SWPP model and the steady-state flow SWPP model was not negligible, and such a difference increased with the decreasing specific storage. We also found that BTCs were not sensitive to the inertial force coefficient, while they were sensitive to the wellbore storage. BTCs with different radius of the wellbore (rw) were clearly different from each other, and a larger rw resulted in a greater concentration at the well during the extraction phase.

  15. Study on steric transition in asymmetrical flow field-flow fractionation and application to characterization of high-energy material.

    Science.gov (United States)

    Dou, Haiyang; Lee, Yong-Ju; Jung, Euo Chang; Lee, Byung-Chul; Lee, Seungho

    2013-08-23

    In field-flow fractionation (FFF), there is the 'steric transition' phenomenon where the sample elution mode changes from the normal to steric/hyperlayer mode. Accurate analysis by FFF requires understanding of the steric transition phenomenon, particularly when the sample has a broad size distribution, for which the effect by combination of different modes may become complicated to interpret. In this study, the steric transition phenomenon in asymmetrical flow FFF (AF4) was studied using polystyrene (PS) latex beads. The retention ratio (R) gradually decreases as the particle size increases (normal mode) and reaches a minimum (Ri) at diameter around 0.5μm, after which R increases with increasing diameter (steric/hyperlayer mode). It was found that the size-based selectivity (Sd) tends to increase as the channel thickness (w) increases. The retention behavior of cyclo-1,3,5-trimethylene-2,4,6-trinitramine (commonly called 'research department explosive' (RDX)) particles in AF4 was investigated by varying experimental parameters including w and flow rates. AF4 showed a good reproducibility in size determination of RDX particles with the relative standard deviation of 4.1%. The reliability of separation obtained by AF4 was evaluated by transmission electron microscopy (TEM). Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Spontaneous generation and reversals of mean flows in a convectively-generated internal gravity wave field

    Science.gov (United States)

    Couston, Louis-Alexandre; Lecoanet, Daniel; Favier, Benjamin; Le Bars, Michael

    2017-11-01

    We investigate via direct numerical simulations the spontaneous generation and reversals of mean zonal flows in a stably-stratified fluid layer lying above a turbulent convective fluid. Contrary to the leading idealized theories of mean flow generation by self-interacting internal waves, the emergence of a mean flow in a convectively-generated internal gravity wave field is not always possible because nonlinear interactions of waves of different frequencies can disrupt the mean flow generation mechanism. Strong mean flows thus emerge when the divergence of the Reynolds stress resulting from the nonlinear interactions of internal waves produces a strong enough anti-diffusive acceleration for the mean flow, which, as we will demonstrate, is the case when the Prandtl number is sufficiently low, or when the energy input into the internal wavefield by the convection and density stratification are sufficiently large. Implications for mean zonal flow production as observed in the equatorial stratospheres of the Earth, Saturn and Jupiter, and possibly occurring in other geophysical systems such as planetary and stellar interiors will be briefly discussed. Funding provided by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program through Grant Agreement No. 681835-FLUDYCO-ERC-2015-CoG.

  17. CFD modelling and PIV experimental validation of flow fields in urban environments

    Directory of Open Access Journals (Sweden)

    Gnatowska Renata

    2017-01-01

    Full Text Available The problem of flow field in the urban boundary-layer (UBL in aspects of wind comfort around buildings and pollutant dispersion has grown in importance since human activity has become so intense that it started to have considerable impact on environment. The issue of wind comfort in urban areas is the result of complex interactions of many flow phenomena and for a long time it arouses a great interest of the research centres. The aim of article is to study urban atmospheric flow at the local scale, which allows for both a detailed reproduction of the flow phenomena and the development of wind comfort criteria. The proposed methodology involves the use of PIV wind tunnel experiments as well as numerical simulations (Computational Fluid Dynamics, CFD in order to enhance understanding of the flow phenomena at this particular scale in urban environments. The analysis has been performed for the 3D case of two surface-mounted buildings arranged in tandem, which were placed with one face normal to the oncoming flow. The local characteristics of flow were obtained by the use of commercial CFD code (ANSYS Fluent. The validation was carried out with reference to the PIV results.

  18. In situ spatiotemporal mapping of flow fields around seeded stem cells at the subcellular length scale.

    Directory of Open Access Journals (Sweden)

    Min Jae Song

    2010-09-01

    Full Text Available A major hurdle to understanding and exploiting interactions between the stem cell and its environment is the lack of a tool for precise delivery of mechanical cues concomitant to observing sub-cellular adaptation of structure. These studies demonstrate the use of microscale particle image velocimetry (μ-PIV for in situ spatiotemporal mapping of flow fields around mesenchymal stem cells, i.e. murine embryonic multipotent cell line C3H10T1/2, at the subcellular length scale, providing a tool for real time observation and analysis of stem cell adaptation to the prevailing mechanical milieu. In the absence of cells, computational fluid dynamics (CFD predicts flow regimes within 12% of μ-PIV measures, achieving the technical specifications of the chamber and the flow rates necessary to deliver target shear stresses at a particular height from the base of the flow chamber. However, our μ-PIV studies show that the presence of cells per se as well as the density at which cells are seeded significantly influences local flow fields. Furthermore, for any given cell or cell seeding density, flow regimes vary significantly along the vertical profile of the cell. Hence, the mechanical milieu of the stem cell exposed to shape changing shear stresses, induced by fluid drag, varies with respect to proximity of surrounding cells as well as with respect to apical height. The current study addresses a previously unmet need to predict and observe both flow regimes as well as mechanoadaptation of cells in flow chambers designed to deliver precisely controlled mechanical signals to live cells. An understanding of interactions and adaptation in response to forces at the interface between the surface of the cell and its immediate local environment may be key for de novo engineering of functional tissues from stem cell templates as well as for unraveling the mechanisms underlying multiscale development, growth and adaptation of organisms.

  19. Wind-Tunnel Survey of an Oscillating Flow Field for Application to Model Helicopter Rotor Testing

    Science.gov (United States)

    Mirick, Paul H.; Hamouda, M-Nabil H.; Yeager, William T., Jr.

    1990-01-01

    A survey was conducted of the flow field produced by the Airstream Oscillator System (AOS) in the Langley Transonic Dynamics Tunnel (TDT). The magnitude of a simulated gust field was measured at 15 locations in the plane of a typical model helicopter rotor when tested in the TDT using the Aeroelastic Rotor Experimental System (ARES) model. These measurements were made over a range of tunnel dynamic pressures typical of those used for an ARES test. The data indicate that the gust field produced by the AOS is non-uniform across the tunnel test section, but should be sufficient to excite a model rotor.

  20. Design, Development and Testing of Shape Shifting Wing Model

    Directory of Open Access Journals (Sweden)

    Dean Ninian

    2017-11-01

    Full Text Available The design and development of morphing (shape shifting aircraft wings—an innovative technology that has the potential to increase the aerodynamic efficiency and reduce noise signatures of aircrafts—was carried out. This research was focused on reducing lift-induced drag at the flaps of the aerofoil and to improve the design to achieve the optimum aerodynamic efficiency. Simulation revealed a 10.8% coefficient of lift increase for the initial morphing wing and 15.4% for the optimized morphing wing as compared to conventional wing design. At angles of attack of 0, 5, 10 and 15 degrees, the optimized wing has an increase in lift-to-drag ratio of 18.3%, 10.5%, 10.6% and 4% respectively when compared with the conventional wing. Simulations also showed that there is a significant improvement on pressure distribution over the lower surface of the morphing wing aerofoil. The increase in flow smoothness and reduction in vortex size reduced pressure drag along the trailing edge of the wing as a result an increase in pressure on the lower surface was experienced. A morphing wing reduced the size of the vortices and therefore the noise levels measured were reduced by up to 50%.

  1. Visualization techniques for studying high angle of attack separated vortical flows

    Science.gov (United States)

    Nelson, Robert C.

    1988-01-01

    Flow visualization techniques can provide information on high angle of attack separated flows around slender aircraft configurations that may be unobtainable otherwise. At large angles of attack the flow field is dominated by vortical structures originating on the forebody wing extension, wing and forward control surfaces. Several techniques that are suitable for tracking vortices in subsonic wind tunnels are introduced. A discussion of visualization photographs and quantitative data obtained from visualization studies on vortex trajectory and breakdown position on both static and dynamic wind tunnel models is presented.

  2. Survey of studies on the flow and heat transfer of two-component, two-phase flow of liquid metal in magnetic field

    International Nuclear Information System (INIS)

    Kumamaru, Hiroshige

    1980-01-01

    Brief review of the studies on the flow and heat transfer of two-component, two-phase flow of liquid metal in magnetic field is presented. R.J. Thome measured the distribution of void rate, slip ratio and pressure loss for the two-phase flow of NaK-N 2 under vertical magnetic field. The void rate distribution became even and the slip ratio increased with the increasing magnetic field. The experimental results of pressure loss was compared with the calculation by an equation derived from the homogeneous flow model. R.G. Owen et al. made the analytical studies of the MHD friction loss of two phase flow. Michiyoshi et al. made experimental studies on the hydrodynamic local properties of Hg-Ar two-phase flow of slug region in a vertically ascending tube under magnetic field, and Kimi et al. also made studies on the heat transfer of Hg-Ar flow under magnetic field. Saito et al. measured the slip ratio and pressure loss of NaK-N 2 flow. As a whole, it can be said that the average void rate decreases, and its distribution becomes even under magnetic field. The slip ratio increases, and the friction loss factor becomes nearly one. It was hard to make clear the heat transfer characteristics. (Kato, T.)

  3. Lifetime, turnover time, and fast magnetic field regeneration in random flows

    International Nuclear Information System (INIS)

    Tanner, S. E. M.

    2007-01-01

    The fast dynamo is thought to be relevant in the regeneration of magnetic fields in astrophysics where the value of the magnetic Reynolds number (Rm) is immense. The fast dynamo picture is one in which chaotic flows provide a mechanism for the stretching of magnetic field lines. Furthermore, a cascade of energy down to small scales results in intermittent regions of a small-scale, intense magnetic field. Given this scenario it is natural to invoke the use of kinematic random flows in order to understand field regeneration mechanisms better. Here a family of random flows is used to study the effects that L, the lifetime of the cell, and τ, the turnover time of the cell, may have on magnetic field regeneration. Defining the parameter Γ=L/τ, it has been varied according to Γ>1, Γ<1, Γ∼O(1). In the kinematic regime, dynamo growth rates and Lyapunov exponents are examined at varying values of Rm. The possibility of fast dynamo action is considered. In the nonlinear regime, magnetic and kinetic energies are examined. Results indicate that there does appear to be a relationship between Γ and dynamo efficiency. In particular, the most efficient dynamos seem to operate at lower values of Γ

  4. Understanding dielectrophoretic trapping of neuronal cells: modelling electric field, electrode-liquid interface and fluid flow

    International Nuclear Information System (INIS)

    Heida, T.; Rutten, W.L.C.; Marani, E.

    2002-01-01

    By application of dielectrophoresis neuronal cells can be trapped successfully. Several trapping experiments have been performed using a quadrupole electrode structure at different amplitudes (1, 3, and 5 V pp ) and frequencies (10-50 MHz). Due to the high conductivity of the suspending medium negative dielectrophoretic forces are created. The dielectrophoretic force is determined by the gradient of the electric field. However, the electrode-liquid interfaces are responsible for decreased electric field strengths, and thus decreased field gradients, inside the medium, especially at lower frequencies. Circuit modelling is used to determine the frequency-dependent electric field inside the medium. The creation of an electric field in high conductivity of the medium results in local heating, which in turn induces fluid flow. This flow also drives the neurons and was found to enhance the trapping effect of the dielectrophoretic force. With the use of finite element modelling, this aspect was investigated. The results show that the dielectrophoretic force is dominating just above the substrate. When the upward dielectrophoretic force is large enough to levitate the cells, they may be dragged along with the fluid flow. The result is that more cells may be trapped than expected on the basis of dielectrophoresis alone. (author)

  5. The effects of magnetic fields on the growth of thermal instabilities in cooling flows

    Science.gov (United States)

    David, Laurence P.; Bregman, Joel N.

    1989-01-01

    The effects of heat conduction and magnetic fields on the growth of thermal instabilities in cooling flows are examined using a time-dependent hydrodynamics code. It is found that, for magnetic field strengths of roughly 1 micro-Gauss, magnetic pressure forces can completely suppress shocks from forming in thermally unstable entropy perturbations with initial length scales as large as 20 kpc, even for initial amplitudes as great as 60 percent. Perturbations with initial amplitudes of 50 percent and initial magnetic field strengths of 1 micro-Gauss cool to 10,000 K on a time scale which is only 22 percent of the initial instantaneous cooling time. Nonlinear perturbations can thus condense out of cooling flows on a time scale substantially less than the time required for linear perturbations and produce significant mass deposition of cold gas while the accreting intracluster gas is still at large radii.

  6. Experiments on a low aspect ratio wing at low Reynolds numbers

    Science.gov (United States)

    Morse, Daniel R.

    At the start of the 21st century much of the focus of aircraft design has been turned to unmanned aerial vehicles (UAVs) which generally operate at much lower speeds in higher risk areas than manned aircraft. One subset of UAVs are Micro Air Vehicles (MAVs) which usually are no larger than 20cm and rely on non-traditional shapes to generate lift at very low velocities. This purpose of this work is to describe, in detail with experimental methods, the flow field around a low aspect ratio wing operating at low Reynolds numbers and at high angles of attack. Quantitative measurements are obtained by Three Component Time Resolved Particle Image Velocimetry (3C TR PIV) which describe the mean and turbulent flow field. This research focuses on the leading edge separation zone and the vortex shedding process which occurs at the leading edge. Streamwise wing tip vortices which dominate the lift characteristics are described with flow visualization and 3C TR PIV measurements. Turbulent Kinetic Energy (TKE) is described at the leading edge over several angles of attack. Turbulent Reynolds stresses in all three directions are described over the wing span and several Reynolds numbers. Two primary cyclic processes are observed within the flow field; one low frequency oscillation in the separated region and one high frequency event associated with leading edge vortex formation and convection. Two length scales are proposed and are shown to match well with each other, one based on leading edge vortex shedding frequency and convective velocity and the other based on mean vortex separation distance. A new method of rendering velocity frequency content over large data sets is proposed and used to illustrate the different frequencies observed at the leading edge.

  7. Magnetohydrodynamic flow in a rectangular duct under a uniform transverse magnetic field at high Hartmann number

    International Nuclear Information System (INIS)

    Temperley, D.J.

    1976-01-01

    In this paper we consider fully developed, laminar, unidirectional flow of uniformly conducting, incompressible fluid through a rectangular duct of uniform cross-section. An externally applied magnetic field acts parallel to one pair of opposite walls and induced velocity and magnetic fields are generated in a direction parallel to the axis of the duct. The governing equations and boundary conditions for the latter fields are introduced and study is then concentrated on the special case of a duct having all walls non-conducting. For values of the Hartmann number M>>1, classical asymptotic analysis reveals the leading terms in the expansions of the induced fields in all key regions, with the exception of certain boundary layers near the corners of the duct. The order of magnitude of the affect of the latter layers on the flow-rate is discussed and closed-form solutions are obtained for the induced fields near the corners of the duct. Attempts were made to formulate a concise Principle of Minimum Singularity to enable the correct choice of eigen functions for the various field components in the boundary layers on the walls parallel to the applied field. It was found, however, that these components are best found by taking the outer expansion of the closed-form solution in those boundary-layers near the corners of the duct where classical asymptotic analysis is not applicable. (author)

  8. Development of Delta Wing Aerodynamics Research in Universiti Teknologi Malaysia Low Speed Wind Tunnel

    Directory of Open Access Journals (Sweden)

    Shabudin Mat

    2014-07-01

    Full Text Available This paper presents wind tunnel experiment on two delta wing configurations which are differentiated by their leading edge profiles: sharp and round-edged wings. The experiments were performed as a part of the delta wing aerodynamics research development in Universiti Teknologi Malaysia, low speed tunnel (UTM-LST. Steady load balance and flow visualization tests were conducted at Reynolds numbers of 0.5, 1, and 1.5 × 106, respectively. The flow measurement at low Reynolds number was also performed at as low as speed of 5 m/s. During the experiments, laser with smoke flow visualizations test was performed on both wings. The study has identified interesting features of the interrelationship between the conventional leading edge primary vortex and the occurrence and development of the vortex breakdown above the delta wings. The results conclude the vortex characteristics are largely dependent on the Reynolds number, angle of attack, and leading-edge radii of the wing.

  9. Flapping and flexible wings for biological and micro air vehicles

    Science.gov (United States)

    Shyy, Wei; Berg, Mats; Ljungqvist, Daniel

    1999-07-01

    Micro air vehicles (MAVs) with wing spans of 15 cm or less, and flight speed of 30-60 kph are of interest for military and civilian applications. There are two prominent features of MAV flight: (i) low Reynolds number (10 4-10 5), resulting in unfavorable aerodynamic conditions to support controlled flight, and (ii) small physical dimensions, resulting in certain favorable scaling characteristics including structural strength, reduced stall speed, and low inertia. Based on observations of biological flight vehicles, it appears that wing motion and flexible airfoils are two key attributes for flight at low Reynolds number. The small size of MAVs corresponds in nature to small birds, which do not glide like large birds, but instead flap with considerable change of wing shape during a single flapping cycle. With flapping and flexible wings, birds overcome the deteriorating aerodynamic performance under steady flow conditions by employing unsteady mechanisms. In this article, we review both biological and aeronautical literatures to present salient features relevant to MAVs. We first summarize scaling laws of biological and micro air vehicles involving wing span, wing loading, vehicle mass, cruising speed, flapping frequency, and power. Next we discuss kinematics of flapping wings and aerodynamic models for analyzing lift, drag and power. Then we present issues related to low Reynolds number flows and airfoil shape selection. Recent work on flexible structures capable of adjusting the airfoil shape in response to freestream variations is also discussed.

  10. Integration of Research for an Exhaust Thermoelectric Generator and the Outer Flow Field of a Car

    Science.gov (United States)

    Jiang, T.; Su, C. Q.; Deng, Y. D.; Wang, Y. P.

    2017-05-01

    The exhaust thermoelectric generator (TEG) can generate electric power from a car engine's waste heat. It is important to maintain a sufficient temperature difference across the thermoelectric modules. The radiator is connected to the cooling units of the thermoelectric modules and used to take away the heat from the TEG system. This paper focuses on the research for the integration of a TEG radiator and the flow field of the car chassis, aiming to cool the radiator by the high speed flow around the chassis. What is more, the TEG radiator is designed as a spoiler to optimize the flow field around the car chassis and even reduce the aerodynamic drag. Concentrating on the flow pressure of the radiator and the aerodynamic drag force, a sedan model with eight different schemes of radiator configurations are studied by computational fluid dynamics simulation. Finally, the simulation results indicate that a reasonable radiator configuration can not only generate high flow pressure to improve the cooling performance, which provides a better support for the TEG system, but also acts as a spoiler to reduce the aerodynamic drag force.

  11. Dynamic X-ray radiography reveals particle size and shape orientation fields during granular flow.

    Science.gov (United States)

    Guillard, François; Marks, Benjy; Einav, Itai

    2017-08-15

    When granular materials flow, the constituent particles segregate by size and align by shape. The impacts of these changes in fabric on the flow itself are not well understood, and thus novel non-invasive means are needed to observe the interior of the material. Here, we propose a new experimental technique using dynamic X-ray radiography to make such measurements possible. The technique is based on Fourier transformation to extract spatiotemporal fields of internal particle size and shape orientation distributions during flow, in addition to complementary measurements of velocity fields through image correlation. We show X-ray radiography captures the bulk flow properties, in contrast to optical methods which typically measure flow within boundary layers, as these are adjacent to any walls. Our results reveal the rich dynamic alignment of particles with respect to streamlines in the bulk during silo discharge, the understanding of which is critical to preventing destructive instabilities and undesirable clogging. The ideas developed in this paper are directly applicable to many other open questions in granular and soft matter systems, such as the evolution of size and shape distributions in foams and biological materials.

  12. Study on the temporal and spatial characteristics of high-speed turbulent flow field and its optical transmission effects

    Science.gov (United States)

    Chen, Cheng; Fei, Jindong; Yi, Shihe; Tang, Wenzhuo

    2011-08-01

    When the aircraft flights in the earth's atmosphere with high speed, it will bring the aero-optical effects into optical imaging detector system. These aero-optical propagation effects are caused by two parts: high-speed turbulent flow field and aero-thermal window. This paper discusses the light propagation effects caused by high-speed turbulent flow field. The high-speed turbulent flow field is a highly non-uniformly time-varying medium, which possesses some characteristics depending on both time and space. While the light propagates through such a medium, the imaging on target of detector system will be affected. This paper describes both the temporal and spatial characteristics of high-speed turbulent flow field. To obtain the instantaneous distribution characteristics of turbulent flow field, one method is applying NPLS-based measurement technique of supersonic flow field. The three-dimensional density field is obtained by the relationship between density and image gray. We studied the physical phenomena of optical wave propagating through turbulent flow field and then the caused optical distortion. The NPLS technique is a high-resolution measurement method of the fine structure of supersonic three-dimensional complex flow field. The time resolution of NPLS technique is 6 ns, and the time correlation resolution is 200 ns. These resolutions can satisfy the description of the characteristics related to the time scale. We are able to describe the time correlation characteristics of density field using NPLS image with different time intervals. Finally, the optical transmission effects of light, which propagates through turbulent flow field, were simulated and studied. According to the instantaneous density field obtained from the NPLS technique, it is carried out that the simulation of optical transmission effect of high-speed turbulent flow field at several typical states. Then, using the ray-tracing method, the optical distance OPDi along the propagation path is

  13. A Video-Based Experimental Investigation of Wing Rock

    Science.gov (United States)

    1989-08-01

    maintained a negative damping in roll (Fig. 6b). Ross concluded that wing tanks act like an aerodynamic fence, controlling flow separation over the wing...to Ross that wing rock was initiated by a nonlinear yawing moment due to sideslip, which caused a divergent Dutch roll oscillation to grow into the...20 30 40 50 e) (p (D EG) * Fig. 128 Continued S * 158 (Fig. 128a) and cycle B (Fig. 128b ) both occurred early in the 0 build-up and consisted of

  14. Influence of the temperature-dependent viscosity on convective flow in the radial force field.

    Science.gov (United States)

    Travnikov, Vadim; Zaussinger, Florian; Beltrame, Philippe; Egbers, Christoph

    2017-08-01

    The numerical investigation of convective flows in the radial force field caused by an oscillating electric field between spherical surfaces has been performed. A temperature difference (T_{1}>T_{2}) as well as a radial force field triggers a fluid flow similar to the Rayleigh-Bénard convection. The onset of convective flow has been studied by means of the linear stability analysis as a function of the radius ratio η=R_{1}/R_{2}. The influence of the temperature-dependent viscosity has been investigated in detail. We found that a varying viscosity contrast β=ν(T_{2})/ν(T_{1}) between β=1 (constant viscosity) and β=50 decreases the critical Rayleigh number by a factor of 6. Additionally, we perform a bifurcation analysis based on numerical simulations which have been calculated using a modified pseudospectral code. Numerical results have been compared with the GeoFlow experiment which is located on the International Space Station (ISS). Nonturbulent three-dimensional structures are found in the numerically predicted parameter regime. Furthermore, we observed multiple stable solutions in both experiments and numerical simulations, respectively.

  15. Magnetic particle movement program to calculate particle paths in flow and magnetic fields

    International Nuclear Information System (INIS)

    Inaba, Toru; Sakazume, Taku; Yamashita, Yoshihiro; Matsuoka, Shinya

    2014-01-01

    We developed an analysis program for predicting the movement of magnetic particles in flow and magnetic fields. This magnetic particle movement simulation was applied to a capturing process in a flow cell and a magnetic separation process in a small vessel of an in-vitro diagnostic system. The distributions of captured magnetic particles on a wall were calculated and compared with experimentally obtained distributions. The calculations involved evaluating not only the drag, pressure gradient, gravity, and magnetic force in a flow field but also the friction force between the particle and the wall, and the calculated particle distributions were in good agreement with the experimental distributions. Friction force was simply modeled as static and kinetic friction forces. The coefficients of friction were determined by comparing the calculated and measured results. This simulation method for solving multiphysics problems is very effective at predicting the movements of magnetic particles and is an excellent tool for studying the design and application of devices. - Highlights: ●We developed magnetic particles movement program in flow and magnetic fields. ●Friction force on wall is simply modeled as static and kinetic friction force. ●This program was applied for capturing and separation of an in-vitro diagnostic system. ●Predicted particle distributions on wall were agreed with experimental ones. ●This method is very effective at predicting movements of magnetic particles

  16. Structural Controls on Groundwater Flow in Basement Terrains: Geophysical, Remote Sensing, and Field Investigations in Sinai

    KAUST Repository

    Mohamed, Lamees

    2015-07-09

    An integrated [very low frequency (VLF) electromagnetic, magnetic, remote sensing, field, and geographic information system (GIS)] study was conducted over the basement complex in southern Sinai (Feiran watershed) for a better understanding of the structural controls on the groundwater flow. The increase in satellite-based radar backscattering values following a large precipitation event (34 mm on 17–18 January 2010) was used to identify water-bearing features, here interpreted as preferred pathways for surface water infiltration. Findings include: (1) spatial analysis in a GIS environment revealed that the distribution of the water-bearing features (conductive features) corresponds to that of fractures, faults, shear zones, dike swarms, and wadi networks; (2) using VLF (43 profiles), magnetic (7 profiles) techniques, and field observations, the majority (85 %) of the investigated conductive features were determined to be preferred pathways for groundwater flow; (3) northwest–southeast- to north–south-trending conductive features that intersect the groundwater flow (southeast to northwest) at low angles capture groundwater flow, whereas northeast–southwest to east–west features that intersect the flow at high angles impound groundwater upstream and could provide potential productive well locations; and (4) similar findings are observed in central Sinai: east–west-trending dextral shear zones (Themed and Sinai Hinge Belt) impede south to north groundwater flow as evidenced by the significant drop in hydraulic head (from 467 to 248 m above mean sea level) across shear zones and by reorientation of regional flow (south–north to southwest–northeast). The adopted integrated methodologies could be readily applied to similar highly fractured basement arid terrains elsewhere. © 2015 Springer Science+Business Media Dordrecht

  17. Architecture and emplacement of flood basalt flow fields: case studies from the Columbia River Basalt Group, NW USA

    Science.gov (United States)

    Vye-Brown, C.; Self, S.; Barry, T. L.

    2013-03-01

    The physical features and morphologies of collections of lava bodies emplaced during single eruptions (known as flow fields) can be used to understand flood basalt emplacement mechanisms. Characteristics and internal features of lava lobes and whole flow field morphologies result from the forward propagation, radial spread, and cooling of individual lobes and are used as a tool to understand the architecture of extensive flood basalt lavas. The features of three flood basalt flow fields from the Columbia River Basalt Group are presented, including the Palouse Falls flow field, a small (8,890 km2, ˜190 km3) unit by common flood basalt proportions, and visualized in three dimensions. The architecture of the Palouse Falls flow field is compared to the complex Ginkgo and more extensive Sand Hollow flow fields to investigate the degree to which simple emplacement models represent the style, as well as the spatial and temporal developments, of flow fields. Evidence from each flow field supports emplacement by inflation as the predominant mechanism producing thick lobes. Inflation enables existing lobes to transmit lava to form new lobes, thus extending the advance and spread of lava flow fields. Minimum emplacement timescales calculated for each flow field are 19.3 years for Palouse Falls, 8.3 years for Ginkgo, and 16.9 years for Sand Hollow. Simple flow fields can be traced from vent to distal areas and an emplacement sequence visualized, but those with multiple-layered lobes present a degree of complexity that make lava pathways and emplacement sequences more difficult to identify.

  18. Mean-field effects on flows in relativistic heavy-ion collisions

    Energy Technology Data Exchange (ETDEWEB)

    Isse, M.; Ohnishi, A. [Hokkaido Univ., Graduate School of Science, Sapporo, Hokkaido (Japan); Otuka, N. [Hokkaido Univ., Graduate School of Engineering, Sapporo, Hokkaido (Japan); Sahu, P.K. [Istituto Nazionale di Fisica Nucleare, Sezione di Catania (Italy); Nara, Y. [Brookhaven National Laboratory, RIKEN BNL Research Center, Upton, NY (United States)

    2002-09-01

    At RHIC experiments, started in 2000, the data obtained recently seem to exhibit QGP formation, but the conclusion is not drawn yet. Here, we pay out attention to the collective flows at hadronic freeze-out as an evidence of QGP formation. To discuss it, the mean-field effect on the flows is not negligible. It is dominant at SIS or AGS energy, and our conjecture is that it is negligible at SPS or RHIC energy. We formed a model to investigate our assumption, and some simulated results are shown. (author)

  19. Subsurface flow in a soil-mantled subtropical dolomite karst slope: A field rainfall simulation study

    Science.gov (United States)

    Fu, Z. Y.; Chen, H. S.; Zhang, W.; Xu, Q. X.; Wang, S.; Wang, K. L.

    2015-12-01

    Soil and epikarst co-evolve resulting in complex structures, but their coupled structural effects on hydrological processes are poorly understood in karst regions. This study examined the plot-scale subsurface flow characteristics from an integrated soil-epikarst system perspective in a humid subtropical cockpit karst region of Southwest China. A trench was excavated to the epikarst lower boundary for collecting individual subsurface flows in five sections with different soil thicknesses. Four field rainfall simulation experiments were carried out under different initial moisture conditions (dry and wet) and rainfall intensities (114 mm h- 1 (high) and 46 mm h- 1 (low) on average). The soil-epikarst system was characterized by shallow soil overlaying a highly irregular epikarst surface with a near-steady infiltration rate of about 35 mm h- 1. The subsurface flows occurred mainly along the soil-epikarst interface and were dominated by preferential flow. The subsurface flow hydrographs showed strong spatial variability and had high steady-state coefficients (0.52 and 0.36 for high and low rainfall intensity events). Irregular epikarst surface combining with high vertical drainage capacity resulted in high threshold rainfall depths for subsurface flows: 67 mm and 263 mm for initial wet and dry conditions, respectively. The above results evidenced that the irregular and permeable soil-epikarst interface was a crucial component of soil-epikarst architecture and consequently should be taken into account in the hydrological modeling for karst regions.

  20. New multiphase choke correlations for a high flow rate Iranian oil field

    Directory of Open Access Journals (Sweden)

    M. Safar Beiranvand

    2012-06-01

    Full Text Available The multiphase flow through wellhead restrictions of an offshore oil field in Iran is investigated and two sets of new correlations are presented for high flow rate and water cut conditions. The both correlations are developed by using 748 actual data points, corresponding to critical flow conditions of gas-liquid mixtures through wellhead chokes. The first set of correlations is a modified Gilbert equation and predicts liquid flow rates as a function of flowing wellhead pressure, gas-liquid ratio and surface wellhead choke size. To minimize error in such condition, in the second correlation, free water, sediment and emulsion (BS & W is also considered as an effective parameter. The predicted oil flow rates by the new sets of correlations are in the excellent agreement with the measured ones. These results are found to be statistically superior to those predicted by other relevant published correlations. The both proposed correlations exhibit more accuracy (only 2.95% and 2.0% average error, respectively than the existent correlations. These results should encourage the production engineer which works at such condition to utilize the proposed correlations for future practical answers when a lack of available information, time, and calculation capabilities arises.