WorldWideScience

Sample records for aerodynamic stability

  1. Aerodynamic stability of cable-stayed bridges under erection

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xin-jun; SUN Bing-nan; XIANG Hai-fan

    2005-01-01

    In this work, nonlinear multimode aerodynamic analysis of the Jingsha Bridge under erection over the Yangtze River is conducted, and the evolutions of structural dynamic characteristics and the aerodynamic stability with erection are numerically generated. Instead of the simplified method, nonlinear multimode aerodynamic analysis is suggested to predict the aerodynamic stability of cable-stayed bridges under erection. The analysis showed that the aerodynamic stability maximizes at the relatively early stages, and decreases as the erection proceeds. The removal of the temporary piers in side spans and linking of the main girder to the anchor piers have important influence on the dynamic characteristics and aerodynamic stability of cable-stayed bridges under erection.

  2. Aerodynamic stability of cable-stayed-suspension hybrid bridges

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xin-jun; SUN Bing-nan

    2005-01-01

    Three-dimensional nonlinear aerodynamic stability analysis was applied to study the aerodynamic stability of a cable-stayed-suspension (CSS) hybrid bridge with main span of 1400 meters, and the effects of some design parameters (such as the cable sag, length of suspension portion, cable plane arrangement, subsidiary piers in side spans, the deck form, etc.) on the aerodynamic stability of the bridge are analytically investigated. The key design parameters, which significantly influence the aerodynamic stability of CSS hybrid bridges, are pointed out, and based on the wind stability the favorable structural system of CSS hybrid bridges is discussed.

  3. Aerodynamic stability of cable-supported bridges using CFRP cables

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xin-jun; YING Lei-dong

    2007-01-01

    To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable's cross-sectional area is determined by the principle of equivalent axial stiffness.Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge,its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable's cross-sectional area should be determined by the principle of equivalent axial stiffness.

  4. An experimental study of the longitudinal aerodynamic and static stability characteristics of hang gliders

    OpenAIRE

    Kilkenny, E. A.

    1986-01-01

    A mobile experimental test facility has been developed to carry out the aerodynamic evaluation of hang glider wings normally performed in a wind tunnel. Longitudinal aerodynamic data obtained using this facility is presented for three modern hang glider wings, a Silhouette, Demon 175 and Magic 166, together with surface flow patterns for the latter two wings. The longitudinal stability criterion are studied and alternatives established, equivalent to the stick fixed an...

  5. Stability-Constrained Aerodynamic Shape Optimization with Applications to Flying Wings

    Science.gov (United States)

    Mader, Charles Alexander

    A set of techniques is developed that allows the incorporation of flight dynamics metrics as an additional discipline in a high-fidelity aerodynamic optimization. Specifically, techniques for including static stability constraints and handling qualities constraints in a high-fidelity aerodynamic optimization are demonstrated. These constraints are developed from stability derivative information calculated using high-fidelity computational fluid dynamics (CFD). Two techniques are explored for computing the stability derivatives from CFD. One technique uses an automatic differentiation adjoint technique (ADjoint) to efficiently and accurately compute a full set of static and dynamic stability derivatives from a single steady solution. The other technique uses a linear regression method to compute the stability derivatives from a quasi-unsteady time-spectral CFD solution, allowing for the computation of static, dynamic and transient stability derivatives. Based on the characteristics of the two methods, the time-spectral technique is selected for further development, incorporated into an optimization framework, and used to conduct stability-constrained aerodynamic optimization. This stability-constrained optimization framework is then used to conduct an optimization study of a flying wing configuration. This study shows that stability constraints have a significant impact on the optimal design of flying wings and that, while static stability constraints can often be satisfied by modifying the airfoil profiles of the wing, dynamic stability constraints can require a significant change in the planform of the aircraft in order for the constraints to be satisfied.

  6. Aerodynamics of bridge hangers in smooth and turbulent flow and implications on aeroelastic stability

    DEFF Research Database (Denmark)

    Demartino, Cristoforo; Ricciardelli, Francesco; Georgakis, Christos T.

    2015-01-01

    by an extruded High Density PolyEthylene (HDPE) circular sheath [1]. In the last 20 years, several bridge cable manufacturers have introduced surface modifications on HDPE sheath in order to reduce the drag and to ensure the aerodynamic stability in all climatic conditions. In the case of plain HDPE sheaths......, of mechanical damage occurring during transport and installation, as well as of the ageing process due to the exposure to environmental factors. Few experimental works are already available dealing with the effects of imperfections on the aerodynamics of bridge cables. For example, Matteoni and Georgakis...... of a full scale yawed bridge cable section model, for varying Reynolds numbers and wind angles-of-attack, using passive dynamic wind tunnel tests. They demonstrated that the in-plane aerodynamic damping of a bridge cable section and the overall dynamic response are strongly affected by changes in the angle...

  7. Study of the aerostatic and aerodynamic stability of super long-span cable-stayed bridges

    Institute of Scientific and Technical Information of China (English)

    Zhang Xinjun; Sun Hailing

    2014-01-01

    With the increase of span length,the bridge tends to be more flexible,and the wind stability be-comes an important problem for the design and construction of super long-span cable-stayed bridges. By taking a super long-span cable-stayed bridge with a main span of 1 400 m as example,the aerostatic and aerodynamic stability of the bridge are investigated by three-dimensional nonlinear aerostatic and aerodynamic stability analy-sis,and the results are compared with those of a suspension bridge with a main span of 1 385 m,and from the aspect of wind stability,the feasibility of using cable-stayed bridge in super long-span bridge with a main span above 1 000 m is discussed. In addition,the influences of design parameters including the depth and width of the girder,the tower structure,the tower height-to-span ratio,the side-to-main span ratio,the auxiliary piers in the side span and the anchorage system of stay cables,etc on the aerostatic and aerodynamic stability of su-per long-span cable-stayed bridges are investigated numerically;the key design parameters are pointed out,and also their reasonable values are proposed.

  8. Overview of stability and transition in external aerodynamics

    NARCIS (Netherlands)

    Henkes, R.A.W.M.; Van Ingen, J.L.

    1998-01-01

    The boundary layer along the fuselage, wings and tailplanes of aircraft will usually be laminar at the leading edge and will become unstable further downstream. Once the boundary layer has become unstable it will undergo transition to turbulence. Stability and transition can be considered as one of

  9. Fast Trailed Vorticity Modeling for Wind Turbine Aerodynamics and its Influence on Aeroelastic Stability

    DEFF Research Database (Denmark)

    Pirrung, Georg

    In this work, an aerodynamic model for the use in aeroelastic wind turbine codes is presented. It consists of a simplified lifting line model covering the induction due to the trailed vorticity in the near wake, a 2D shed vorticity model and a far wake model using the well known blade element...... to earlier implementations, the model has been improved in several ways: Among other things, the need for model-specific user input has been removed, the effect of downwind convection of the trailed vorticity is modeled, the near wake induction is iterated to stabilize the computations and the numerical...... efficiency is increased. The model is validated against results from full rotor CFD and free wake panel code computations, which show that the model yields improved results in steady and unsteady simulations compared to unsteady BEM modeling. Especially the aerodynamic work due to prescribed in-plane and out...

  10. A numerical investigation into the aerodynamic characteristics and aeroelastic stability of a footbridge

    Science.gov (United States)

    Taylor, I. J.; Vezza, M.

    2009-01-01

    The results of a numerical investigation into the aerodynamic characteristics and aeroelastic stability of a proposed footbridge across a highway in the north of England are presented. The longer than usual span, along with the unusual nature of the pedestrian barriers, indicated that the deck configuration was likely to be beyond the reliable limits of the British design code BD 49/01. The calculations were performed using the discrete vortex method, DIVEX, developed at the Universities of Glasgow and Strathclyde. DIVEX has been successfully validated on a wide range of problems, including the aeroelastic response of bridge deck sections. In particular, the investigation focussed on the effects of non-standard pedestrian barriers on the structural integrity of the bridge. The proposed deck configuration incorporated a barrier comprised of angled flat plates, and the bridge was found to be unstable at low wind speeds, with the plates having a strong turning effect on the flow at the leading edge of the deck. These effects are highlighted in both a static and dynamic analysis of the bridge deck, along with modifications to the design that aim to improve the aeroelastic stability of the deck. Proper orthogonal decomposition (POD) was also used to investigate the unsteady pressure field on the upper surface of the static bridge deck. The results of the flutter investigation and the POD analysis highlight the strong influence of the pedestrian barriers on the overall aerodynamic characteristics and aeroelastic stability of the bridge.

  11. A CFD-based analysis of the 14-Bis aircraft aerodynamics and stability

    Directory of Open Access Journals (Sweden)

    Leonardo Ostan Bitencourt

    2011-05-01

    Full Text Available The work reported in the present paper was performed to honor the centennial of the flight by Alberto Santos Dumont with his 14-Bis aircraft. The paper describes results for a computational fluid dynamics (CFD analysis of the 14-Bis aircraft aerodynamics and flight stability. The 14-Bis aircraft geometry was generated from historical sources and observations. CFD computations were performed using well-established commercial codes for calculation of the historical flight conditions. Simulations considered a Reynolds-averaged Navier-Stokes formulation, in which turbulence closure was achieved by using Menter's model. The flight conditions investigated were primarily concerned with historical observations regarding flight speeds and the need for a more powerful engine, as well as flight stability characteristics of the 14-Bis airplane, which are unknown up to the present day. The results led to qualitative agreement with historical reports, although quite interesting conclusions could be drawn with regard to the actual aerodynamic flight speeds and the aircraft stability parameters.

  12. Influence of time domain unsteady aerodynamics on coupled flap-lag-torsional aeroelastic stability and response of rotor blades

    Science.gov (United States)

    Friedmann, P. P.; Robinson, L. H.

    1988-01-01

    This paper describes the incorporation of finite-state, time-domain aerodynamics in a flag-lag-torsional aeroelastic stability and response analysis in forward flight. Improvements to a previous formulation are introduced which eliminate spurious singularities. The methodology for solving the aeroelastic stability and response problems with augmented states, in the time domain, is presented using an implicit formulation. Results describing the aeroelastic behavior of soft and stiff in-plane hingeless rotor blades, in forward flight, are presented to illustrate the sensitivity of both the stability and response problems to time domain unsteady aerodynamics.

  13. The effect of winglets on the static aerodynamic stability characteristics of a representative second generation jet transport model

    Science.gov (United States)

    Jacobs, P. F.; Flechner, S. G.

    1976-01-01

    A baseline wing and a version of the same wing fitted with winglets were tested. The longitudinal aerodynamic characteristics were determined through an angle-of-attack range from -1 deg to 10 deg at an angle of sideslip of 0 deg for Mach numbers of 0.750, 0.800, and 0.825. The lateral aerodynamic characteristics were determined through the same angle-of-attack range at fixed sideslip angles of 2.5 deg and 5 deg. Both configurations were investigated at Reynolds numbers of 13,000,000, per meter (4,000,000 per foot) and approximately 20,000,000 per meter (6,000,000 per foot). The winglet configuration showed slight increases over the baseline wing in static longitudinal and lateral aerodynamic stability throughout the test Mach number range for a model design lift coefficient of 0.53. Reynolds number variation had very little effect on stability.

  14. Effect of Side Wind on the Directional Stability and Aerodynamics of a Hybrid Buoyant Aircraft

    Directory of Open Access Journals (Sweden)

    Haque Anwar U

    2016-01-01

    Full Text Available Directional stability characteristics explain the capabilities of a hybrid buoyant aircraft’s performance against the side wind, which induces flow separation that is chaotic in nature and may lead to oscillations of the aerodynamic surfaces. A numerical study is carried out to estimate the effect of side wind. The boundary conditions for the computational domain are set to velocity inlet and pressure outlet. Due to the incompressible flow at the cruise velocity, the density is taken to be constant. For these steady state simulations, the time is discretized in first order implicit and the SIMPLE scheme is employed for pressure velocity coupling alongwith k-ω SST model. Based on the results obtained so far, it is concluded that voluminous hybrid lifting fuselage is the major cause of directional.

  15. Aerodynamic modeling and stability analysis of a high-speed train under strong rain and crosswind conditions

    Institute of Scientific and Technical Information of China (English)

    Xue-ming SHAO; Jun WAN; Da-wei CHEN; Hong-bing XIONG

    2011-01-01

    With the development of high-speed train,it is considerably concerned about the aerodynamic characteristics and operation safety issues of the high-speed train under extreme weather conditions.The aerodynamic performance of a high-speed train under heavy rain and strong crosswind conditions are modeled using the Eulerian two-phase model in this paper.The impact of heavy rainfall on train aerodynamics is investigated,coupling heavy rain and a strong crosswind.Results show that the lift force,side force,and rolling moment of the train increase significantly with wind speed up to 40 m/s under a rainfall rate of 60 mm/h.when considering the rain and wind conditions.The increases of the lift force,side force,and rolling moment may deteriorate the train operating safety and cause the train to overturn.A quasi-static stability analysis based on the moment balance is used to determine the limit safety speed of a train under different rain and wind levels.The results can provide a frame of reference for the train safe operation under strong rain and crosswind conditions.

  16. The influence of time dependent flight and maneuver velocities and elastic or viscoelastic flexibilities on aerodynamic and stability derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Cochrane, Alexander P. [Aerospace Engineering Department, University of Glasgow, University Avenue, Glasgow, Lanarkshire (United Kingdom); Merrett, Craig G. [Mechanical and Aerospace Engineering Department, Carleton Univ., 1125 Col. By Dr., Ottawa, ON (Canada); Hilton, Harry H. [Aerospace Engineering Department in the College of Engineering and Private Sector Program Division at the National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States)

    2014-12-10

    The advent of new structural concepts employing composites in primary load carrying aerospace structures in UAVs, MAVs, Boeing 787s, Airbus A380s, etc., necessitates the inclusion of flexibility as well as viscoelasticity in static structural and aero-viscoelastic analyses. Differences and similarities between aeroelasticity and aero-viscoelasticity have been investigated in [2]. An investigation is undertaken as to the dependence and sensitivity of aerodynamic and stability derivatives to elastic and viscoelastic structural flexibility and as to time dependent flight and maneuver velocities. Longitudinal, lateral and directional stabilities are investigated. It has been a well established fact that elastic lifting surfaces are subject to loss of control effectiveness and control reversal at certain flight speeds, which depend on aerodynamic, structural and material properties [5]. Such elastic analyses are extended to linear viscoelastic materials under quasi-static, dynamic, and sudden and gradual loading conditions. In elastic wings one of the critical static parameters is the velocity at which control reversal takes place (V{sub REV}{sup E}). Since elastic formulations constitute viscoelastic initial conditions, viscoelastic reversal may occur at speeds V{sub REV<}{sup ≧}V{sub REV}{sup E}, but furthermore does so in time at 0 < t{sub REV} ≤ ∞. The influence of the twin effects of viscoelastic and elastic materials and of variable flight velocities on longitudinal, lateral, directional and spin stabilities are also investigated. It has been a well established fact that elastic lifting surfaces are subject to loss of control effectiveness and control reversal at certain flight speeds, which depend on aerodynamic, structural and material properties [5]. Such elastic analyses are here extended to linear viscoelastic materials under quasi-static, dynamic, and sudden and gradual loading conditions. In elastic wings the critical parameter is the velocity at

  17. Aerodynamic stability of long span suspension bridges with low torsional natural frequencies

    DEFF Research Database (Denmark)

    Andersen, Michael Styrk; Johansson, Jens; Brandt, Anders

    2016-01-01

    Classical flutter of suspended bridge decks can be avoided if the torsional frequencies are lower than the vertical. Wind tunnel tests of single boxes and twin box section models with torsional natural frequencies above and below the vertical frequency has been conducted. Flutter was avoided in all....... In order to design aerodynamically stable suspension bridges with low torsional natural frequencies it is suggested to increase the mass moment of inertia and provide adequate torsional stiffness by the main cables spacing....

  18. Aerodynamic stability of long span suspension bridges with low torsional natural frequencies

    DEFF Research Database (Denmark)

    Andersen, Michael Styrk; Johansson, Jens; Brandt, Anders;

    2016-01-01

    Classical flutter of suspended bridge decks can be avoided if the torsional frequencies are lower than the vertical. Wind tunnel tests of single boxes and twin box section models with torsional natural frequencies above and below the vertical frequency has been conducted. Flutter was avoided in a....... In order to design aerodynamically stable suspension bridges with low torsional natural frequencies it is suggested to increase the mass moment of inertia and provide adequate torsional stiffness by the main cables spacing....

  19. The Influence of Geometric Coupling on the Whirl Flutter Stability in Tiltrotor Aircraft with Unsteady Aerodynamics

    DEFF Research Database (Denmark)

    Kim, Taeseong; Shin, SangJoon; Kim, Do-Hyung

    2012-01-01

    A further improvement is attempted of an existing analytical model for an accurate prediction of the aeroelastic stability of a tiltrotor aircraft. A rigid-bladed rotor structural model with the natural frequencies selected appropriately in both the flapping and lagging motions is used. The geome......A further improvement is attempted of an existing analytical model for an accurate prediction of the aeroelastic stability of a tiltrotor aircraft. A rigid-bladed rotor structural model with the natural frequencies selected appropriately in both the flapping and lagging motions is used...

  20. Aerodynamic tricks for pitching oscillation and visual stabilization in a hovering bird

    Science.gov (United States)

    Su, Jian-Yuan; Ting, Shang-Chieh; Yang, Jing-Tang

    2010-11-01

    We experimentally investigate how small birds attain a stabilized vision and body posture during hovering. Wing-beats of finches and passerines executing asymmetrical hovering provide lift merely during the downstroke. The downstroke lift is significantly greater than the bird weight, thereby causing a pitch-up swing of the bird body. A hovering bird skillfully and unceasingly tunes the position and orientation of lift force to stabilize its vision, so that the eye displacement is approximately one-tenth less than the tail, causing an illusion that the bird body is rotating about the eye. The hovering birds also spread and fold periodically their tail with an evident phase relationship with respect to the beating wings. We found that hovering birds use their tail to intercept the strong downward air-flow induced by the downstroking wings, and sophisticatedly spread their tail upon the arrival of the downward air-flow, rendering a pitch-up moment that effectively counteracts the pitch-down body rotation. Hence during hovering the bird essentially undergoes a dynamically-stable pitching oscillation, and concurrently attains a stabilized vision.

  1. A parametric study of planform and aeroelastic effects on aerodynamic center, alpha- and q- stability derivatives. Appendix A: A computer program for calculating alpha- and q- stability derivatives and induced drag for thin elastic aeroplanes at subsonic and supersonic speeds

    Science.gov (United States)

    Roskam, J.; Lan, C.; Mehrotra, S.

    1972-01-01

    The computer program used to determine the rigid and elastic stability derivatives presented in the summary report is listed in this appendix along with instructions for its use, sample input data and answers. This program represents the airplane at subsonic and supersonic speeds as (a) thin surface(s) (without dihedral) composed of discrete panels of constant pressure according to the method of Woodward for the aerodynamic effects and slender beam(s) for the structural effects. Given a set of input data, the computer program calculates an aerodynamic influence coefficient matrix and a structural influence coefficient matrix.

  2. Aerodynamic stability study of a long-span prestressed concrete cable-stayed bridge. Aerodynamic behavior of edge box girder under uniform flow; Chodai PC shachokyo no taifu anteisei ni kansuru kenkyu. Ichiyoryuchu ni okeru edge girder keishiki no kuriki tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Nomura, T. [Obayashi Corp., Tokyo (Japan)

    1999-01-10

    In recent years, the construction of long-span bridges is on the increase. Prestressed concrete cable-stayed bridges are dynamically very efficient structures of relatively low cost that blend in well with the landscape. Maintenance is also easy. Consequently, the adoption of edge box girders for cable-stayed bridges is increasing worldwide, but problems related to the aerodynamic stability of the structure have emerged. The aerodynamic stability of edge box girders for a prestressed concrete cable-stayed bridge was investigated under uniform flow conditions by conducting several wind tunnel experiments. As a result, the section of the bridge deck was optimized to prevent torsional flutter within an angle of attack varying from -5 to +5 degrees. It is therefore possible to guarantee the aerodynamic stability of long-span prestressed concrete cable-stayed bridges. (author)

  3. Aerodynamic Performance and Static Stability and Control of Flat-Top Hypersonic Gliders at Mach Numbers from 0.6 to 18

    Science.gov (United States)

    Syvertson, Clarence A; Gloria, Hermilo R; Sarabia, Michael F

    1958-01-01

    A study is made of aerodynamic performance and static stability and control at hypersonic speeds. In a first part of the study, the effect of interference lift is investigated by tests of asymmetric models having conical fuselages and arrow plan-form wings. The fuselage of the asymmetric model is located entirely beneath the wing and has a semicircular cross section. The fuselage of the symmetric model was centrally located and has a circular cross section. Results are obtained for Mach numbers from 3 to 12 in part by application of the hypersonic similarity rule. These results show a maximum effect of interference on lift-drag ratio occurring at Mach number of 5, the Mach number at which the asymmetric model was designed to exploit favorable lift interference. At this Mach number, the asymmetric model is indicated to have a lift-drag ratio 11 percent higher than the symmetric model and 15 percent higher than the asymmetric model when inverted. These differences decrease to a few percent at a Mach number of 12. In the course of this part of the study, the accuracy to the hypersonic similarity rule applied to wing-body combinations is demonstrated with experimental results. These results indicate that the rule may prove useful for determining the aerodynamic characteristics of slender configurations at Mach numbers higher than those for which test equipment is really available. In a second part of the study, the aerodynamic performance and static stability and control characteristics of a hypersonic glider are investigated in somewhat greater detail. Results for Mach numbers from 3 to 18 for performance and 0.6 to 12 for stability and control are obtained by standard text techniques, by application of the hypersonic stability rule, and/or by use of helium as a test medium. Lift-drag ratios of about 5 for Mach numbers up to 18 are shown to be obtainable. The glider studied is shown to have acceptable longitudinal and directional stability characteristics through the

  4. Unsteady aerodynamics modeling for flight dynamics application

    Institute of Scientific and Technical Information of China (English)

    Qing Wang; Kai-Feng He; Wei-Qi Qian; Tian-Jiao Zhang; Yan-Qing Cheng; Kai-Yuan Wu

    2012-01-01

    In view of engineering application,it is practicable to decompose the aerodynamics into three components:the static aerodynamics,the aerodynamic increment due to steady rotations,and the aerodynamic increment due to unsteady separated and vortical flow.The first and the second components can be presented in conventional forms,while the third is described using a one-order differential equation and a radial-basis-function (RBF) network. For an aircraft configuration,the mathematical models of 6-component aerodynamic coefficients are set up from the wind tunnel test data of pitch,yaw,roll,and coupled yawroll large-amplitude oscillations.The flight dynamics of an aircraft is studied by the bifurcation analysis technique in the case of quasi-steady aerodynamics and unsteady aerodynamics,respectively.The results show that:(1) unsteady aerodynamics has no effect upon the existence of trim points,but affects their stability; (2) unsteady aerodynamics has great effects upon the existence,stability,and amplitudes of periodic solutions; and (3) unsteady aerodynamics changes the stable regions of trim points obviously.Furthermore,the dynamic responses of the aircraft to elevator deflections are inspected.It is shown that the unsteady aerodynamics is beneficial to dynamic stability for the present aircraft.Finally,the effects of unsteady aerodynamics on the post-stall maneuverability are analyzed by numerical simulation.

  5. 77 FR 17323 - Special Conditions: XtremeAir GmbH, XA42; Acrobatic Category Aerodynamic Stability

    Science.gov (United States)

    2012-03-26

    ... maintain a 3 degree angle of descent. (D) In place of 14 CFR part 23, Sec. 23.177, Static directional and... unusual design feature associated with its static stability. This airplane can perform at the highest...: April 25, 2012. FOR FURTHER INFORMATION CONTACT: Mr. Ross Schaller, Federal Aviation...

  6. NASP aerodynamics

    Science.gov (United States)

    Whitehead, Allen H., Jr.

    1989-01-01

    This paper discusses the critical aerodynamic technologies needed to support the development of a class of aircraft represented by the National Aero-Space Plane (NASP). The air-breathing, single-stage-to-orbit mission presents a severe challenge to all of the aeronautical disciplines and demands an extension of the state-of-the-art in each technology area. While the largest risk areas are probably advanced materials and the development of the scramjet engine, there remains a host of design issues and technology problems in aerodynamics, aerothermodynamics, and propulsion integration. The paper presents an overview of the most significant propulsion integration problems, and defines the most critical fluid flow phenomena that must be evaluated, defined, and predicted for the class of aircraft represented by the Aero-Space Plane.

  7. Missile Aerodynamics

    Science.gov (United States)

    1979-02-01

    Me 2 L~e coefficient de frottement CI est gnralement n~glig6. L’approximation est justifige par le fait que, qf , nul au recollement, est partout...be costly in terms of time and money. One should aim for a situation where an error of, say, 10% in estimating an aerodynamic coefficient or...constructing tables of forces and moments, or their coefficients , as functions of variables such as inci- dence angle, roll angle, speed and altitude, and

  8. Aerodynamics, aeroelasticity, and stability of hang gliders. Experimental results. [Ames 7- by 10-ft wind tunnel tests

    Science.gov (United States)

    Kroo, I. M.

    1981-01-01

    One-fifth-scale models of three basic ultralight glider designs were constructed to simulate the elastic properties of full scale gliders and were tested at Reynolds numbers close to full scale values. Twenty-four minor modifications were made to the basic configurations in order to evaluate the effects of twist, reflex, dihedral, and various stability enhancement devices. Longitudinal and lateral data were obtained at several speeds through an angle of attack range of -30 deg to +45 deg with sideslip angles of up to 20 deg. The importance of vertical center of gravity displacement is discussed. Lateral data indicate that effective dihedral is lost at low angles of attack for nearly all of the configurations tested. Drag data suggest that lift-dependent viscous drag is a large part of the glider's total drag as is expected for thin, cambered sections at these relatively low Reynolds numbers.

  9. Natural aerodynamics

    CERN Document Server

    Scorer, R S

    1958-01-01

    Natural Aerodynamics focuses on the mathematics of any problem in air motion.This book discusses the general form of the law of fluid motion, relationship between pressure and wind, production of vortex filaments, and conduction of vorticity by viscosity. The flow at moderate Reynolds numbers, turbulence in a stably stratified fluid, natural exploitation of atmospheric thermals, and plumes in turbulent crosswinds are also elaborated. This text likewise considers the waves produced by thermals, transformation of thin layer clouds, method of small perturbations, and dangers of extra-polation.Thi

  10. 变体平尾翼型气动外形设计方法%Airfoil Aerodynamic Optimization Method of Morphing Horizontal Stabilizer

    Institute of Scientific and Technical Information of China (English)

    杜厦; 昂海松

    2012-01-01

    A morphing airfoil instead of traditional horizontal stabilizer and control elements is proposed in order to make the aircraft keep the optimal lift/drag ratio during flight attitude controlling. Bornstein polynomial with order "n" is used to describe the airfoil configuration. A set of airfoil that can provide a minimum drag coefficient at different lift coefficient in a confirmed flight environment is obtained by aerodynamic optimization simulation using the genetic algorithm. It is proved that the morphing airfoil can provide a smaller drag coefficient than the traditional control element do when the same lift coefficient is provided. The relationship between shape control parameters and lift is fitted according to the optimized airfoil. A set of example is used to verify the morphing regularity.%为了使飞机在控制飞行姿态时仍然能保持最优升阻比,提出了一种通过改变翼型形状来代替传统控制舵面采控制飞机俯仰的方法.采用伯恩斯坦多项式对机翼的翼型进行数学建模,并采用遗传算法通过空气动力学仿真对翼型进行优化得到一组在一定飞行环境下、产生附加阻力最小且随升力系数变化的翼型形状.通过对比证明在提供相同升力的情况下,变体翼比传统的控制舵面产生更小的附加阻力.根据翼型形状和升力系数的变化采用数据拟合的方法得到翼型形状控制参数随升力变化的规律.通过算例对变化规律的验证表明其可以用来作为飞行姿态控制的翼型形状变化依据.

  11. Advanced Topics in Aerodynamics

    DEFF Research Database (Denmark)

    Filippone, Antonino

    1999-01-01

    "Advanced Topics in Aerodynamics" is a comprehensive electronic guide to aerodynamics,computational fluid dynamics, aeronautics, aerospace propulsion systems, design and relatedtechnology. We report data, tables, graphics, sketches,examples, results, photos, technical andscientific literature...

  12. 隧道内超车瞬态气动稳定性影响的数值仿真研究%Numerical simulation of aerodynamic stability influence of overtaking vehicles in tunnel

    Institute of Scientific and Technical Information of China (English)

    贺桂敏; 谷正气; 杨滨徽; 龚旭; 孙露

    2012-01-01

    Taking into account the traffic safety, the factors of influencing the straight driving ability and handling stability of the overtaking vehicles in tunnels were considered. From the view of aerodynamic, two real scale vehicle models inside a tunnel were taken as the research object, and with sliding interface and moving mesh technique provided by STAk-CD software, the 3-D transient external flow field around the two vehicles passing each other was simulated. Considering of the influence factors of aerodynamic stability, the following conditions were selected to compare and analyze: two different kinds of lateral distance between overtaking vehicles and the same relative speed, the same lateral distance between overtaking vehicles and three different relative speeds. The aerodynamic changes of the overtaken vehicle are more dramatic, the change trends in the four kinds of conditions all present the sine curve, the change magnitude is particularly evident in Condition I and Condition II, and the straight driving ability and the handling stability are relatively poor. The overtaking process has a relatively small influence on the external flow field of the overtaking vehicle, so the aerodynamic changes are not obvious.%从行车安全方面考虑影响隧道内超车车辆直线行驶性能和操纵稳定性能的因素.从空气动力学角度,以某轿车实车缩比模型为研究对象,采用滑移交界面和动网格技术和STAR-CD软件对隧道内2辆车超车过程的外流场进行瞬态数值模拟.考虑到影响气动力稳定性的因素,选取隧道内2种不同侧向间距(2辆车之间)同种相对车速及同种侧向间距3种不同相对车速4种工况进行对比分析.仿真结果表明:超车过程中被超车的气动力变化更为剧烈,各种工况下的变化趋势都呈类正弦曲线,工况Ⅰ和工况Ⅱ的变化幅度尤为明显,直线行驶性能和操纵稳定性能相对较差;而超车过程对主超车流场影响相对较

  13. INTEGRATED AERODYNAMIC MEASUREMENTS

    NARCIS (Netherlands)

    SCHUTTE, HK

    1992-01-01

    The myoelastic-aerodynamic model of phonation implies that aerodynamic factors are crucial to the evaluation of voice function, Subglottal pressure and mean flow rate represent the vocal power source. If they can be related to the magnitude of the radiated sound power, they may provide an index of v

  14. Reinforced aerodynamic profile

    DEFF Research Database (Denmark)

    2010-01-01

    The present invention relates to the prevention of deformations in an aerodynamic profile caused by lack of resistance to the bending moment forces that are created when such a profile is loaded in operation. More specifically, the invention relates to a reinforcing element inside an aerodynamic...

  15. A stability analysis of a modified version of the chi-square ratio statistic: implications for equivalence testing of aerodynamic particle size distribution.

    Science.gov (United States)

    Weber, Benjamin; Hochhaus, Guenther; Adams, Wallace; Lionberger, Robert; Li, Bing; Tsong, Yi; Lee, Sau L

    2013-01-01

    Demonstration of equivalence in aerodynamic particle size distribution (APSD; e.g., by comparing cascade impactor (CI) profiles) constitutes one of key in vitro tests for supporting bioequivalence between test (T) and reference (R) orally inhaled drug products (OIDPs). A chi-square ratio statistic (CSRS) was previously proposed for equivalence testing of CI profiles. However, it was reported that the CSRS could not consistently discriminate between equivalent and inequivalent CI profiles. The objective of the overall project was to develop a robust and sensitive methodology for assessing equivalence of APSD profiles of T and R OIDPs. We propose here a modified version of the CSRS (mCSRS) and evaluated systematically its behavior when T and R CI profiles were identical. Different scenarios comprising CI profiles with different number of deposition sites and shapes were generated by Monte-Carlo simulation. For each scenario, the mCSRS was applied to 20,000 independent sets of 30 T and 30 R CI profiles that were identical. Different metrics (including mean and median) of the distribution of 900 mCSRSs (30 T × 30 R) were then evaluated for their suitability as a test statistic (i.e., independent of the number of sites and shape of the CI profile) for APSD equivalence testing. The median of the distribution of 900 mCSRSs (MmCSRS) was one regardless of the number of sites and shape of the CI profile. Hence, the MmCSRS is a robust metric for CI profile equivalence testing when T and R CI profiles are identical and potentially useful for APSD equivalence testing.

  16. Aerodynamics of magnetic levitation (MAGLEV) trains

    Science.gov (United States)

    Schetz, Joseph A.; Marchman, James F., III

    1996-01-01

    High-speed (500 kph) trains using magnetic forces for levitation, propulsion and control offer many advantages for the nation and a good opportunity for the aerospace community to apply 'high tech' methods to the domestic sector. One area of many that will need advanced research is the aerodynamics of such MAGLEV (Magnetic Levitation) vehicles. There are important issues with regard to wind tunnel testing and the application of CFD to these devices. This talk will deal with the aerodynamic design of MAGLEV vehicles with emphasis on wind tunnel testing. The moving track facility designed and constructed in the 6 ft. Stability Wind Tunnel at Virginia Tech will be described. Test results for a variety of MAGLEV vehicle configurations will be presented. The last topic to be discussed is a Multi-disciplinary Design approach that is being applied to MAGLEV vehicle configuration design including aerodynamics, structures, manufacturability and life-cycle cost.

  17. Aerodynamic Shutoff Valve

    Science.gov (United States)

    Horstman, Raymond H.

    1992-01-01

    Aerodynamic flow achieved by adding fixed fairings to butterfly valve. When valve fully open, fairings align with butterfly and reduce wake. Butterfly free to turn, so valve can be closed, while fairings remain fixed. Design reduces turbulence in flow of air in internal suction system. Valve aids in development of improved porous-surface boundary-layer control system to reduce aerodynamic drag. Applications primarily aerospace. System adapted to boundary-layer control on high-speed land vehicles.

  18. Research of the aerostatic and aerodynamic stability of super long-span cable-stayed bridges%超大跨度斜拉桥空气静力和动力稳定性研究

    Institute of Scientific and Technical Information of China (English)

    张新军; 孙海凌

    2014-01-01

    With the increase of span length,the cable-stayed bridge tends to be a more slen-der structural system,and consequently the wind stability becomes an important problem for its design and construction. Three-dimensional nonlinear aerostatic and aerodynamic stability anal-ysis of long-span bridges is used to investigate the aerostatic and aerodynamic stability of a su-per long-span cable-stayed bridge with main span of 1 400 m,and the results are compared with those of a suspension bridge with the similar main span,and considering from the aspect of wind stability,the availability of using the cable-stayed bridge in super long-span bridges whose main span exceeds 1 000 m is discussed. In addition,parametric analysis on the aerostat-ic and aerodynamic stability of super long-span cable-stayed bridges is conducted including the depth and width of the girder,structure style of the tower,the tower’s height-to-span ratio,the ratio of side span to main span,the auxiliary piers in the side span and the anchorage system of stay cables etc,and the key design parameters are pointed out,and also their reasonable values are proposed. The results show that as compared to the suspension bridge with the same main span,the cable-stayed bridge has greater structural stiffness,and becomes more stable under the static and dynamic wind action,and consequently becomes a favorable structural system for super long-span bridges whose main span exceeds 1 000 m;the super long-span cable-stayed bridge becomes more aerostatically and aerodynamically stable under the cases that the girder depth is increased,the girder width is decreased,the inverse Y-shaped tower is used,the tow-er’s height is increased,the side span is shortened,the auxiliary piers are installed in side span and the stayed cables are partially earth-anchored.%随着斜拉桥跨度的持续增长,结构更趋于轻柔,风作用下的结构稳定性已成为超千米主跨斜拉桥设计和研究的重要问题。采用

  19. Aerodynamics of Race Cars

    Science.gov (United States)

    Katz, Joseph

    2006-01-01

    Race car performance depends on elements such as the engine, tires, suspension, road, aerodynamics, and of course the driver. In recent years, however, vehicle aerodynamics gained increased attention, mainly due to the utilization of the negative lift (downforce) principle, yielding several important performance improvements. This review briefly explains the significance of the aerodynamic downforce and how it improves race car performance. After this short introduction various methods to generate downforce such as inverted wings, diffusers, and vortex generators are discussed. Due to the complex geometry of these vehicles, the aerodynamic interaction between the various body components is significant, resulting in vortex flows and lifting surface shapes unlike traditional airplane wings. Typical design tools such as wind tunnel testing, computational fluid dynamics, and track testing, and their relevance to race car development, are discussed as well. In spite of the tremendous progress of these design tools (due to better instrumentation, communication, and computational power), the fluid dynamic phenomenon is still highly nonlinear, and predicting the effect of a particular modification is not always trouble free. Several examples covering a wide range of vehicle shapes (e.g., from stock cars to open-wheel race cars) are presented to demonstrate this nonlinear nature of the flow field.

  20. Cable Aerodynamic Control

    DEFF Research Database (Denmark)

    Kleissl, Kenneth

    to a categorization of the different control technics together with an identification of two key mechanisms for reduction of the design drag force. During this project extensive experimental work examining the aerodynamics of the currently used cable surface modifications together with new innovative proposals have...

  1. Aerodynamically shaped vortex generators

    DEFF Research Database (Denmark)

    Hansen, Martin Otto Laver; Velte, Clara Marika; Øye, Stig;

    2016-01-01

    An aerodynamically shaped vortex generator has been proposed, manufactured and tested in a wind tunnel. The effect on the overall performance when applied on a thick airfoil is an increased lift to drag ratio compared with standard vortex generators. Copyright © 2015 John Wiley & Sons, Ltd....

  2. The influence of aerodynamic coefficients on the elements of classic projectile paths

    Directory of Open Access Journals (Sweden)

    Damir D. Jerković

    2011-04-01

    Full Text Available The article deals with the results of the research on the influence of aerodynamic coefficient values on the trajectory elements and the stability parameters of classic axisymmetric projectiles. It presents the characteristic functions of aerodynamic coefficients with regard to aerodynamic parameters and the projectile body shape. The trajectory elements of the model of classic axisymmetric projectiles and the analyses of their changes were presented with respect to the aerodynamic coefficient values. Introduction Classic axisymmetric projectiles fly through atmosphere using muzzle velocity as initial energy resource, so the aerodynamic force and moment have the most significant influence on the motion of projectiles. The aerodynamic force and moment components represented as aerodynamic coefficients depend on motion velocity i. e. flow velocity, the flow features produced by projectile shape and position in the flow, and angular velocity (rate of the body. The functional dependence of aerodynamic coefficients on certain influential parameters, such as angle of attack and angular velocity components is expressed by the derivative of aerodynamic coefficients. The determination of aerodynamic coefficients and derivatives enables complete definition of the aerodynamic force and moment acting on the classic projectile. The projectile motion problem is considered in relation to defining the projectile stability parameters and the conditions under which the stability occurs. The comparative analyses of aerodynamic coefficient values obtained by numerical methods, semi empirical calculations and experimental research give preliminary evaluation of the quality of the determined values. The flight simulation of the motion of a classic axisymetric projectile, which has the shape defined by the aerodynamic coefficient values, enables the comparative analyses of the trajectory elements and stability characteristics. The model of the classic projectile

  3. Aerodynamic Leidenfrost effect

    Science.gov (United States)

    Gauthier, Anaïs; Bird, James C.; Clanet, Christophe; Quéré, David

    2016-12-01

    When deposited on a plate moving quickly enough, any liquid can levitate as it does when it is volatile on a very hot solid (Leidenfrost effect). In the aerodynamic Leidenfrost situation, air gets inserted between the liquid and the moving solid, a situation that we analyze. We observe two types of entrainment. (i) The thickness of the air gap is found to increase with the plate speed, which is interpreted in the Landau-Levich-Derjaguin frame: Air is dynamically dragged along the surface and its thickness results from a balance between capillary and viscous effects. (ii) Air set in motion by the plate exerts a force on the levitating liquid. We discuss the magnitude of this aerodynamic force and show that it can be exploited to control the liquid and even to drive it against gravity.

  4. Computational electromagnetic-aerodynamics

    CERN Document Server

    Shang, Joseph J S

    2016-01-01

    Presents numerical algorithms, procedures, and techniques required to solve engineering problems relating to the interactions between electromagnetic fields, fluid flow, and interdisciplinary technology for aerodynamics, electromagnetics, chemical-physics kinetics, and plasmadynamics This book addresses modeling and simulation science and technology for studying ionized gas phenomena in engineering applications. Computational Electromagnetic-Aerodynamics is organized into ten chapters. Chapter one to three introduce the fundamental concepts of plasmadynamics, chemical-physics of ionization, classical magnetohydrodynamics, and their extensions to plasma-based flow control actuators, high-speed flows of interplanetary re-entry, and ion thrusters in space exploration. Chapter four to six explain numerical algorithms and procedures for solving Maxwell’s equation in the time domain for computational electromagnetics, plasma wave propagation, and the time-dependent c mpressible Navier-Stokes equation for aerodyn...

  5. Hypervelocity Aerodynamics and Control

    Science.gov (United States)

    1990-06-06

    Report: Hypervelocity Aerodynamics and Control 12. PERSONAL AUTHOR(S) T. C. Adamson, Jr. and R. IA. Howe 13a. TYPE OF REPORT 13b. TIME COVERED 14. DATE...6] pulse applied. If the Mxyz system as shown is Fig. 3 r 3. , is used, then we have R21= k costo -t4 ksin yot 1 6r= ro 1 (4) -- (6k 2 - 5 -30k 2 sin

  6. Aerodynamic data of space vehicles

    CERN Document Server

    Weiland, Claus

    2014-01-01

    The capacity and quality of the atmospheric flight performance of space flight vehicles is characterized by their aerodynamic data bases. A complete aerodynamic data base would encompass the coefficients of the static longitudinal and lateral motions and the related dynamic coefficients. In this book the aerodynamics of 27 vehicles are considered. Only a few of them did really fly. Therefore the aerodynamic data bases are often not complete, in particular when the projects or programs were more or less abruptly stopped, often due to political decisions. Configurational design studies or the development of demonstrators usually happen with reduced or incomplete aerodynamic data sets. Therefore some data sets base just on the application of one of the following tools: semi-empirical design methods, wind tunnel tests, numerical simulations. In so far a high percentage of the data presented is incomplete and would have to be verified. Flight mechanics needs the aerodynamic coefficients as function of a lot of var...

  7. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  8. Investigates on Aerodynamic Characteristics of Projectile with Triangular Cross Section

    Institute of Scientific and Technical Information of China (English)

    YI Wen-jun; WANG Zhong-yuan; LI Yan; QIAN Ji-sheng

    2009-01-01

    The aerodynamic characteristics of projectiles with triangular and circular cross sections are investigated respectively by use of free-flight experiment. Processed the experiment data, curves of flight velocity variation and nutation of both projectiles are obtained, based on the curves, their aerodynamic force and moment coefficients are found out by data fitting, and their aerodynamic performances are compared and analyzed. Results show that the projectile with triangular cross section has smaller resistance, higher lift-drag ratio, better static stability, higher stability capability and more excellent maneuverability than those of the projectile with circular cross section, therefore it can be used in the guided projectiles; under lower rotation speed, the triangular section projectile has greater Magnus moment leading to bigger projectile distribution.

  9. Aerodynamics of wind turbines

    CERN Document Server

    Hansen, Martin O L

    2015-01-01

    Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its third edition, it has been substantially updated with respect to structural dynamics and control. The new control chapter now includes details on how to design a classical pitch and torque regulator to control rotational speed and power, while the section on structural dynamics has been extended with a simplified mechanical system explaining the phenomena of forward and backward whirling modes. Readers will also benefit from a new chapter on Vertical Axis W

  10. The Aerodynamic Plane Table

    Science.gov (United States)

    Zahm, A F

    1924-01-01

    This report gives the description and the use of a specially designed aerodynamic plane table. For the accurate and expeditious geometrical measurement of models in an aerodynamic laboratory, and for miscellaneous truing operations, there is frequent need for a specially equipped plan table. For example, one may have to measure truly to 0.001 inch the offsets of an airfoil at many parts of its surface. Or the offsets of a strut, airship hull, or other carefully formed figure may require exact calipering. Again, a complete airplane model may have to be adjusted for correct incidence at all parts of its surfaces or verified in those parts for conformance to specifications. Such work, if but occasional, may be done on a planing or milling machine; but if frequent, justifies the provision of a special table. For this reason it was found desirable in 1918 to make the table described in this report and to equip it with such gauges and measures as the work should require.

  11. Aerodynamics of sports balls

    Science.gov (United States)

    Mehta, R. D.

    1985-01-01

    Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.

  12. Discrete vortex method simulations of aerodynamic admittance in bridge aerodynamics

    DEFF Research Database (Denmark)

    Rasmussen, Johannes Tophøj; Hejlesen, Mads Mølholm; Larsen, Allan;

    , and to determine aerodynamic forces and the corresponding flutter limit. A simulation of the three-dimensional bridge responseto turbulent wind is carried out by quasi steady theory by modelling the bridge girder as a line like structure [2], applying the aerodynamic load coefficients found from the current version...... of DVMFLOW in a strip wise fashion. Neglecting the aerodynamic admittance, i.e. the correlation of the instantaneous lift force to the turbulent fluctuations in the vertical velocities, leads to higher response to high frequency atmospheric turbulence than would be obtained from wind tunnel tests....

  13. Introduction to transonic aerodynamics

    CERN Document Server

    Vos, Roelof

    2015-01-01

    Written to teach students the nature of transonic flow and its mathematical foundation, this book offers a much-needed introduction to transonic aerodynamics. The authors present a quantitative and qualitative assessment of subsonic, supersonic, and transonic flow around bodies in two and three dimensions. The book reviews the governing equations and explores their applications and limitations as employed in modeling and computational fluid dynamics.  Some concepts, such as shock and expansion theory, are examined from a numerical perspective. Others, including shock-boundary-layer interaction, are discussed from a qualitative point of view. The book includes 60 examples and more than 200 practice problems. The authors also offer analytical methods such as Method of Characteristics (MOC) that allow readers to practice with the subject matter.  The result is a wealth of insight into transonic flow phenomena and their impact on aircraft design, including compressibility effects, shock and expansion waves, sho...

  14. Aerodynamics of Small Vehicles

    Science.gov (United States)

    Mueller, Thomas J.

    In this review we describe the aerodynamic problems that must be addressed in order to design a successful small aerial vehicle. The effects of Reynolds number and aspect ratio (AR) on the design and performance of fixed-wing vehicles are described. The boundary-layer behavior on airfoils is especially important in the design of vehicles in this flight regime. The results of a number of experimental boundary-layer studies, including the influence of laminar separation bubbles, are discussed. Several examples of small unmanned aerial vehicles (UAVs) in this regime are described. Also, a brief survey of analytical models for oscillating and flapping-wing propulsion is presented. These range from the earliest examples where quasi-steady, attached flow is assumed, to those that account for the unsteady shed vortex wake as well as flow separation and aeroelastic behavior of a flapping wing. Experiments that complemented the analysis and led to the design of a successful ornithopter are also described.

  15. Aerodynamics of wind turbines

    DEFF Research Database (Denmark)

    Hansen, Martin Otto Laver

    Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its third edition, it has been substantially updated with respect to structural dynamics and control. The new control chapter now includes details on how to design...... Turbines (VAWT). Topics covered include increasing mass flow through the turbine, performance at low and high wind speeds, assessment of the extreme conditions under which the turbine will perform and the theory for calculating the lifetime of the turbine. The classical Blade Element Momentum method...... is also covered, as are eigenmodes and the dynamic behaviour of a turbine. The book describes the effects of the dynamics and how this can be modelled in an aeroelastic code, which is widely used in the design and verification of modern wind turbines. Furthermore, it examines how to calculate...

  16. Wind Turbines Wake Aerodynamics

    DEFF Research Database (Denmark)

    Vermeer, L.; Sørensen, Jens Nørkær; Crespo, A.

    2003-01-01

    The aerodynamics of horizontal axis wind turbine wakes is studied. The contents is directed towards the physics of power extraction by wind turbines and reviews both the near and the far wake region. For the near wake, the survey is restricted to uniform, steady and parallel flow conditions......, thereby excluding wind shear, wind speed and rotor setting changes and yawed conditions. The emphasis is put on measurements in controlled conditions.For the far wake, the survey focusses on both single turbines and wind farm effects, and the experimental and numerical work are reviewed; the main interest...... is to study how the far wake decays downstream, in order to estimate the effect produced in downstream turbines.The article is further restricted to horizontal axis wind turbines and excludes all other types of turbines....

  17. Ornithopter flight stabilization

    Science.gov (United States)

    Dietl, John M.; Garcia, Ephrahim

    2007-04-01

    The quasi-steady aerodynamics model and the vehicle dynamics model of ornithopter flight are explained, and numerical methods are described to capture limit cycle behavior in ornithopter flight. The Floquet method is used to determine stability in forward flight, and a linear discrete-time state-space model is developed. This is used to calculate stabilizing and disturbance-rejecting controllers.

  18. Naval Aerodynamics Test Facility (NATF)

    Data.gov (United States)

    Federal Laboratory Consortium — The NATF specializes in Aerodynamics testing of scaled and fullsized Naval models, research into flow physics found on US Navy planes and ships, aerosol testing and...

  19. Computational aerodynamics and artificial intelligence

    Science.gov (United States)

    Mehta, U. B.; Kutler, P.

    1984-01-01

    The general principles of artificial intelligence are reviewed and speculations are made concerning how knowledge based systems can accelerate the process of acquiring new knowledge in aerodynamics, how computational fluid dynamics may use expert systems, and how expert systems may speed the design and development process. In addition, the anatomy of an idealized expert system called AERODYNAMICIST is discussed. Resource requirements for using artificial intelligence in computational fluid dynamics and aerodynamics are examined. Three main conclusions are presented. First, there are two related aspects of computational aerodynamics: reasoning and calculating. Second, a substantial portion of reasoning can be achieved with artificial intelligence. It offers the opportunity of using computers as reasoning machines to set the stage for efficient calculating. Third, expert systems are likely to be new assets of institutions involved in aeronautics for various tasks of computational aerodynamics.

  20. Research on the Aerodynamic Lift of Vehicle Windshield Wiper

    Directory of Open Access Journals (Sweden)

    Gu Zhengqi

    2016-01-01

    Full Text Available Currently, research on the aerodynamic lift of vehicle windshield wipers is confined to the steady results, and there are very few test results. In the face of this truth, a wind tunnel test is conducted by using the Multipoint Film Force Test System (MFF. In this test, the aerodynamic lift of four kinds of wiper is measured at different wind speeds and different rotation angles. And then, relevant steady-state numerical simulations are accomplished and the mechanism of the aerodynamic lift is analyzed. Furthermore, combined with dynamic meshing and user-defined functions (UDF, transient aerodynamic characteristics of wipers are obtained through numerical simulations. It is found that the aerodynamic lift takes great effect on the stability of wipers, and there is maximum value of the lift near a certain wind speed and rotation angle. The lift force when wipers are rotating with the free stream is less than steady, and the force when rotating against the free stream is greater than steady.

  1. Aerodynamic and aerothermodynamic analysis of space mission vehicles

    CERN Document Server

    Viviani, Antonio

    2015-01-01

    Presenting an up-to-date view on the most important space vehicle configurations, this book contains detailed analyses for several different type of space mission profiles while considering important factors such as aerodynamic loads, aerodynamic heating, vehicle stability and landing characteristics. With that in mind, the authors provide a detailed overview on different state-of-the-art themes of hypersonic aerodynamics and aerothermodynamics, and consider different space vehicle shapes useful for different space mission objectives. These include: ·        Crew Return Vehicle (CRV) ·        Crew Exploration Vehicle (CEV) ·        Sample Return Vehicle (SRV) ·        Flying Test Bed (FTB). Throughout Aerodynamic and Aerothermodynamic Analysis of Space Mission Vehicles many examples are given, with detailed computations and results for the aerodynamics and aerothermodynamics of all such configurations. Moreover, a final chapter on future launchers is provided and an Appendix on...

  2. Introduction to wind turbine aerodynamics

    CERN Document Server

    Schaffarczyk, Alois Peter

    2014-01-01

    Wind-Turbine Aerodynamics is a self-contained textbook which shows how to come from the basics of fluid mechanics to modern wind turbine blade design. It presents a fundamentals of fluid dynamics and inflow conditions, and gives a extensive introduction into theories describing the aerodynamics of wind turbines. After introducing experiments the book applies the knowledge to explore the impact on blade design.The book is an introduction for professionals and students of very varying levels.

  3. Aerodynamics of badminton shuttlecocks

    Science.gov (United States)

    Verma, Aekaansh; Desai, Ajinkya; Mittal, Sanjay

    2013-08-01

    A computational study is carried out to understand the aerodynamics of shuttlecocks used in the sport of badminton. The speed of the shuttlecock considered is in the range of 25-50 m/s. The relative contribution of various parts of the shuttlecock to the overall drag is studied. It is found that the feathers, and the net in the case of a synthetic shuttlecock, contribute the maximum. The gaps, in the lower section of the skirt, play a major role in entraining the surrounding fluid and causing a difference between the pressure inside and outside the skirt. This pressure difference leads to drag. This is confirmed via computations for a shuttlecock with no gaps. The synthetic shuttle experiences more drag than the feather model. Unlike the synthetic model, the feather shuttlecock is associated with a swirling flow towards the end of the skirt. The effect of the twist angle of the feathers on the drag as well as the flow has also been studied.

  4. Introduction. Computational aerodynamics.

    Science.gov (United States)

    Tucker, Paul G

    2007-10-15

    The wide range of uses of computational fluid dynamics (CFD) for aircraft design is discussed along with its role in dealing with the environmental impact of flight. Enabling technologies, such as grid generation and turbulence models, are also considered along with flow/turbulence control. The large eddy simulation, Reynolds-averaged Navier-Stokes and hybrid turbulence modelling approaches are contrasted. The CFD prediction of numerous jet configurations occurring in aerospace are discussed along with aeroelasticity for aeroengine and external aerodynamics, design optimization, unsteady flow modelling and aeroengine internal and external flows. It is concluded that there is a lack of detailed measurements (for both canonical and complex geometry flows) to provide validation and even, in some cases, basic understanding of flow physics. Not surprisingly, turbulence modelling is still the weak link along with, as ever, a pressing need for improved (in terms of robustness, speed and accuracy) solver technology, grid generation and geometry handling. Hence, CFD, as a truly predictive and creative design tool, seems a long way off. Meanwhile, extreme practitioner expertise is still required and the triad of computation, measurement and analytic solution must be judiciously used.

  5. Discrete vortex method simulations of aerodynamic admittance in bridge aerodynamics

    DEFF Research Database (Denmark)

    Rasmussen, Johannes Tophøj; Hejlesen, Mads Mølholm; Larsen, Allan

    , and to determine aerodynamic forces and the corresponding flutter limit. A simulation of the three-dimensional bridge responseto turbulent wind is carried out by quasi steady theory by modelling the bridge girder as a line like structure [2], applying the aerodynamic load coefficients found from the current version...... of DVMFLOW in a strip wise fashion. Neglecting the aerodynamic admittance, i.e. the correlation of the instantaneous lift force to the turbulent fluctuations in the vertical velocities, leads to higher response to high frequency atmospheric turbulence than would be obtained from wind tunnel tests....... In the present work we have extended the laminar oncoming flow in DVMFLOW to a turbulent one, modelled by seeding the upstream flow with vortex particles synthesized from prescribed atmospheric turbulence velocity spectra [3] . The discrete spectrum is sampled from the continuous spectrum subject to a lower cutoff...

  6. Numerical and Experimental Investigations on the Aerodynamic Characteristic of Three Typical Passenger Vehicles

    Directory of Open Access Journals (Sweden)

    yiping wang

    2014-01-01

    Full Text Available The numerical simulation and wind tunnel experiment were employed to investigate the aerodynamic characteristics of three typical rear shapes: fastback, notchback and squareback. The object was to investigate the sensibility of aerodynamic characteristic to the rear shape, and provide more comprehensive experimental data as a reference to validate the numerical simulation. In the wind tunnel experiments, the aerodynamic six components of the three models with the yaw angles range from -15 and 15 were measured. The realizable k-ε model was employed to compute the aerodynamic drag, lift and surface pressure distribution at a zero yaw angle. In order to improve the calculation efficiency and accuracy, a hybrid Tetrahedron-Hexahedron-Pentahedral-Prism mesh strategy was used to discretize the computational domain. The computational results showed a good agreement with the experimental data and the results revealed that different rear shapes would induce very different aerodynamic characteristic, and it was difficult to determine the best shape. For example, the fastback would obtain very low aerodynamic drag, but it would induce positive lift which was not conducive to stability at high speed, and it also would induce bad crosswind stability. In order to reveal the internal connection between the aerodynamic drag and wake vortices, the turbulent kinetic, recirculation length, position of vortex core and velocity profile in the wake were investigated by numerical simulation and PIV experiment.

  7. Fundamentals of modern unsteady aerodynamics

    CERN Document Server

    Gülçat, Ülgen

    2016-01-01

    In this book, the author introduces the concept of unsteady aerodynamics and its underlying principles. He provides the readers with a comprehensive review of the fundamental physics of free and forced unsteadiness, the terminology and basic equations of aerodynamics ranging from incompressible flow to hypersonics. The book also covers modern topics related to the developments made in recent years, especially in relation to wing flapping for propulsion. The book is written for graduate and senior year undergraduate students in aerodynamics and also serves as a reference for experienced researchers. Each chapter includes ample examples, questions, problems and relevant references.   The treatment of these modern topics has been completely revised end expanded for the new edition. It now includes new numerical examples, a section on the ground effect, and state-space representation.

  8. Aerodynamic challenges in span length of suspension bridges

    Institute of Scientific and Technical Information of China (English)

    XIANG Haifan; GE Yaojun

    2007-01-01

    The potential requirement of extreme bridge spans is firstly discussed according to horizontal clearances for navigation and economical construction of deep-water foundation. To ensure the technological feasibility of suspen- sion bridges with longer spans, the Static estimation of feasi- ble span length is then made based on current material strength and weight of cables and deck. After the performances of the countermeasures for raising the aerodynamic stability are reviewed, a trial design of a 5 000 m suspension bridge, which is estimated as a reasonable limitation of span length, is finally conducted to respond to the tomorrow's challenge in span length of suspension bridges with the particular aspects, including dynamic stiffness, aerodynamic flutter and aerostatic stability.

  9. The influence of the elastic vibration of the carrier to the aerodynamics of the external store in air-launch-to-orbit process

    Science.gov (United States)

    Yang, Lei; Ye, Zheng-Yin; Wu, Jie

    2016-11-01

    The separation between the carrier and store is one of the most important and difficult phases in Air-launch-to-orbit technology. Based on the previous researches, the interference aerodynamic forces of the store caused by the carrier are obvious in the earlier time during the separation. And the interference aerodynamics will be more complex when considering the elastic deformation of the carrier. Focusing on the conditions that in the earlier time during the separation, the steady and unsteady interference aerodynamic forces of the store are calculated at different angle of attacks and relative distances between the carrier and store. During the calculation, the elastic vibrations of the carrier are considered. According to the cause of formations of the interference aerodynamics, the interference aerodynamic forces of the store are divided into several components. The relative magnitude, change rule, sphere of influence and mechanism of interference aerodynamic forces components of the store are analyzed quantitatively. When the relative distance between the carrier and store is small, the interference aerodynamic forces caused by the elastic vibration of the carrier is about half of the total aerodynamic forces of the store. And as the relative distance increases, the value of interference aerodynamic forces decrease. When the relative distance is larger than twice the mean aerodynamic chord of the carrier, the values of interference aerodynamic forces of the store can be ignored. Besides, under the influence of the steady interference aerodynamic forces, the lift characteristics of the store are worse and the static stability margin is poorer.

  10. Engineering models in wind energy aerodynamics: Development, implementation and analysis using dedicated aerodynamic measurements

    NARCIS (Netherlands)

    Schepers, J.G.

    2012-01-01

    The subject of aerodynamics is of major importance for the successful deployment of wind energy. As a matter of fact there are two aerodynamic areas in the wind energy technology: Rotor aerodynamics and wind farm aerodynamics. The first subject considers the flow around the rotor and the second subj

  11. Rotor/body aerodynamic interactions

    Science.gov (United States)

    Betzina, M. D.; Smith, C. A.; Shinoda, P.

    1985-01-01

    A wind tunnel investigation was conducted in which independent, steady state aerodynamic forces and moments were measured on a 2.24 m diam. two bladed helicopter rotor and on several different bodies. The mutual interaction effects for variations in velocity, thrust, tip-path-plane angle of attack, body angle of attack, rotor/body position, and body geometry were determined. The results show that the body longitudinal aerodynamic characteristics are significantly affected by the presence of a rotor and hub, and that the hub interference may be a major part of such interaction. The effects of the body on the rotor performance are presented.

  12. Aerodynamics Research Revolutionizes Truck Design

    Science.gov (United States)

    2008-01-01

    During the 1970s and 1980s, researchers at Dryden Flight Research Center conducted numerous tests to refine the shape of trucks to reduce aerodynamic drag and improved efficiency. During the 1980s and 1990s, a team based at Langley Research Center explored controlling drag and the flow of air around a moving body. Aeroserve Technologies Ltd., of Ottawa, Canada, with its subsidiary, Airtab LLC, in Loveland, Colorado, applied the research from Dryden and Langley to the development of the Airtab vortex generator. Airtabs create two counter-rotating vortices to reduce wind resistance and aerodynamic drag of trucks, trailers, recreational vehicles, and many other vehicles.

  13. The aerodynamics of wind turbines

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær; Mikkelsen, Robert Flemming; Troldborg, Niels

    2013-01-01

    In the paper we present state-of-the-art of research in wind turbine aerodynamics. We start be giving a brief historical review and a survey over aerodynamic research in wind energy. Next, we focus on some recent research results obtained by our wind energy group at Department of Mechanical...... Engineering at DTU. In particular, we show some new results on the classical problem of the ideal rotor and present a series of new results from an on-going research project dealing with the modelling and simulation of turbulent flow structures in the wake behind wind turbines....

  14. Aerodynamics and flight performance of flapping wing micro air vehicles

    Science.gov (United States)

    Silin, Dmytro

    Research efforts in this dissertation address aerodynamics and flight performance of flapping wing aircraft (ornithopters). Flapping wing aerodynamics was studied for various wing sizes, flapping frequencies, airspeeds, and angles of attack. Tested wings possessed both camber and dihedral. Experimental results were analyzed in the framework of momentum theory. Aerodynamic coefficients and Reynolds number are defined using a reference velocity as a vector sum of a freestream velocity and a strokeaveraged wingtip velocity. No abrupt stall was observed in flapping wings for the angle of attack up to vertical. If was found that in the presence of a freestream lift of a flapping wing in vertical position is higher than the propulsive thrust. Camber and dihedral increased both lift and thrust. Lift-curve slope, and maximum lift coefficient increased with Reynolds number. Performance model of an ornithopter was developed. Parametric studies of steady level flight of ornithopters with, and without a tail were performed. A model was proposed to account for wing-sizing effects during hover. Three micro ornithopter designs were presented. Ornithopter flight testing and data-logging was performed using a telemetry acquisition system, as well as motion capture technology. The ability of ornithopter for a sustained flight and a presence of passive aerodynamic stability were shown. Flight data were compared with performance simulations. Close agreement in terms of airspeed and flapping frequency was observed.

  15. Aerodynamic design via control theory

    Science.gov (United States)

    Jameson, Antony

    1988-01-01

    The question of how to modify aerodynamic design in order to improve performance is addressed. Representative examples are given to demonstrate the computational feasibility of using control theory for such a purpose. An introduction and historical survey of the subject is included.

  16. POEMS in Newton's Aerodynamic Frustum

    Science.gov (United States)

    Sampedro, Jaime Cruz; Tetlalmatzi-Montiel, Margarita

    2010-01-01

    The golden mean is often naively seen as a sign of optimal beauty but rarely does it arise as the solution of a true optimization problem. In this article we present such a problem, demonstrating a close relationship between the golden mean and a special case of Newton's aerodynamical problem for the frustum of a cone. Then, we exhibit a parallel…

  17. Analysis and modeling of unsteady aerodynamics with application to wind turbine blade vibration at standstill conditions

    DEFF Research Database (Denmark)

    Skrzypinski, Witold Robert

    Wind turbine blade vibrations at standstill conditions were investigated in the present work. These included vortex-induced and stall-induced vibrations. Thus, it was investigated whether the stand still vibrations are vortex-induced, stall-induced or a combination of both types. The work comprised...... limits. The motivation for it was that the standard aerodynamics existing in state-of-the-art aeroelastic codes is effectively quasi-steady in deep stall. If such an assumption was incorrect, these codes could predict stall-induced vibrations inaccurately. The main conclusion drawn from these analyzes...... was that even a relatively low amount of temporal lag in the aerodynamic response may significantly increase the aerodynamic damping and therefore influence the aeroelastic stability limits, relative to quasisteady aerodynamic response. Two- and three-dimensional CFD computations included non-moving, prescribed...

  18. Studies on aerodynamic interferences between the components of transport airplane using unstructured Navier-Stokes simulations

    Energy Technology Data Exchange (ETDEWEB)

    Wang, G.; Ye, Z. [Northwestern Polytechnical Univ., National Key Lab. of Aerodynamic Design and Research, Xi' an (China)]. E-mail: wanggang@nwpu.edu.cn; yezy@nwpu.edu.cn

    2005-07-01

    It is well known that the aerodynamic interference flows widely exist between the components of conventional transport airplane, for example, the wing-fuselage juncture flow, wing-pylon-nacelle flow and tail-fuselage juncture flow. The main characteristic of these aerodynamic interferences is flow separation, which will increase the drag, reduce the lift and cause adverse influence on the stability and controllability of the airplane. Therefore, the modern civil transport designers should do their best to eliminate negative effects of aerodynamic interferences, which demands that the aerodynamic interferences between the aircraft components should be predicted and analyzed accurately. Today's CFD techniques provide us powerful and efficient analysis tools to achieve this objective. In this paper, computational investigations of the interferences between transport aircraft components have been carried out by using a viscous flow solver based on mixed element type unstructured meshes. (author)

  19. Simulating Magneto-Aerodynamic Actuator

    Science.gov (United States)

    2007-12-20

    2005. 19. Boeuf, J.P., Lagmich, Y., Callegari, Th., and Pitchford , L.C., Electro- hydrodynamic Force and Acceleration in Surface Discharge, AIAA 2006...Plasmadynamics and Laser Award, 2004 AFRL Point of Contact Dr. Donald B. Paul , AFRL/VA WPAFB, OH 937-255-7329, met weekly. Dr. Alan Garscadden, AFRL/PR...validating database for numerical simulation of magneto-aerodynamic actuator for hypersonic flow control. Points of contact at the AFRL/VA are Dr. D. Paul

  20. Aerodynamic Heating in Hypersonic Boundary Layers:\\ Role of Dilatational Waves

    CERN Document Server

    Zhu, Yiding; Wu, Jiezhi; Chen, Shiyi; Lee, Cunbiao; Gad-el-Hak, Mohamed

    2016-01-01

    The evolution of multi-mode instabilities in a hypersonic boundary layer and their effects on aerodynamic heating are investigated. Experiments are conducted in a Mach 6 wind tunnel using Rayleigh-scattering flow visualization, fast-response pressure sensors, fluorescent temperature-sensitive paint (TSP), and particle image velocimetry (PIV). Calculations are also performed based on both parabolized stability equations (PSE) and direct numerical simulations (DNS). It is found that second-mode dilatational waves, accompanied by high-frequency alternating fluid compression and expansion, produce intense aerodynamic heating in a small region that rapidly heats the fluid passing through it. As a result, the surface temperature rapidly increases and results in an overshoot over the nominal transitional value. When the dilatation waves decay downstream, the surface temperature decreases gradually until transition is completed. A theoretical analysis is provided to interpret the temperature distribution affected by ...

  1. Aerodynamics Laboratory Facilities, Equipment, and Capabilities

    Data.gov (United States)

    Federal Laboratory Consortium — The following facilities, equipment, and capabilities are available in the Aerodynamics Laboratory Facilities and Equipment (1) Subsonic, open-jet wind tunnel with...

  2. Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) project will focus on the development and demonstration of hypersonic inflatable aeroshell technologies...

  3. Review paper on wind turbine aerodynamics

    DEFF Research Database (Denmark)

    Hansen, Martin Otto Laver; Aagaard Madsen, Helge

    2011-01-01

    The paper describes the development and description of the aerodynamic models used to estimate the aerodynamic loads on wind turbine constructions. This includes a status of the capabilities of computation fluid dynamics and the need for reliable airfoil data for the simpler engineering models....... Also a discussion of the use of passive and active aerodynamic devices is included such as, e.g., Vortex Generators and distributed active flaps. Finally the problem of wakes in wind farms is addressed and a section of the likely future development of aerodynamic models for wind turbines is included...

  4. Aerodynamic Aspects of Wind Energy Conversion

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær

    2011-01-01

    This article reviews the most important aerodynamic research topics in the field of wind energy. Wind turbine aerodynamics concerns the modeling and prediction of aerodynamic forces, such as performance predictions of wind farms, and the design of specific parts of wind turbines, such as rotor......-blade geometry. The basics of the blade-element momentum theory are presented along with guidelines for the construction of airfoil data. Various theories for aerodynamically optimum rotors are discussed, and recent results on classical models are presented. State-of-the-art advanced numerical simulation tools...

  5. Numerical study on the aerodynamic performance and safe running of high-speed trains in sandstorms

    Institute of Scientific and Technical Information of China (English)

    Hong-bing XIONG; Wen-guang YU; Da-wei CHEN; Xue-ming SHAO

    2011-01-01

    The influence of sandstorms on train aerodynamic performance and safe running was studied in response to the frequent occurrence of sandstorm weather in north China.An Eulerian two-phase model in the computational fluid dynamic (CFD) software FLUENT,validated with published data,was used to solve the gas-solid multiphase flow of a sandstorm around a train.The train aerodynamic performance under different sandstorm levels and no sand conditions was then simulated.Results showed that in sandstorm weather,the drag,lift,side forces and overturning moment increase by variable degrees.Based on a numerical analysis of aerodynamic characteristics,an equation of train stability was also derived using the theory of moment balance from the view of dynamics.A recommended speed limit of a train under different sandstorm levels was calculated based on the stability analysis.

  6. Aerodynamic Design Methodology for Blended Wing Body Transport

    Institute of Scientific and Technical Information of China (English)

    LI Peifeng; ZHANG Binqian; CHEN Yingchun; YUAN Changsheng; LIN Yu

    2012-01-01

    This paper puts forward a design idea for blended wing body (BWB).The idea is described as that cruise point,maximum lift to drag point and pitch trim point are in the same flight attitude.According to this design idea,design objectives and constraints are defined.By applying low and high fidelity aerodynamic analysis tools,BWB aerodynamic design methodology is established by the combination of optimization design and inverse design methods.High lift to drag ratio,pitch trim and acceptable buffet margin can be achieved by this design methodology.For 300-passenger BWB configuration based on static stability design,as compared with initial configuration,the maximum lift to drag ratio and pitch trim are achieved at cruise condition,zero lift pitching moment is positive,and buffet characteristics is well.Fuel burn of 300-passenger BWB configuration is also significantly reduced as compared with conventional civil transports.Because aerodynamic design is carried out under the constraints of BWB design requirements,the design configuration fulfills the demands for interior layout and provides a solid foundation for continuous work.

  7. Biomimetic Approach for Accurate, Real-Time Aerodynamic Coefficients Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Aerodynamic and structural reliability and efficiency depends critically on the ability to accurately assess the aerodynamic loads and moments for each lifting...

  8. Migration on Wings Aerodynamics and Energetics

    CERN Document Server

    Kantha, Lakshmi

    2012-01-01

    This book is an effort to explore the technical aspects associated with bird flight and migration on wings. After a short introduction on the birds migration, the book reviews the aerodynamics and Energetics of Flight and presents the calculation of the Migration Range. In addition, the authors explains aerodynamics of the formation flight and finally introduces great flight diagrams.

  9. Aerodynamic seal assemblies for turbo-machinery

    Energy Technology Data Exchange (ETDEWEB)

    Bidkar, Rahul Anil; Wolfe, Christopher; Fang, Biao

    2015-09-29

    The present application provides an aerodynamic seal assembly for use with a turbo-machine. The aerodynamic seal assembly may include a number of springs, a shoe connected to the springs, and a secondary seal positioned about the springs and the shoe.

  10. Aerodynamics of wind turbines emerging topics

    CERN Document Server

    Amano, R S

    2014-01-01

    Focusing on Aerodynamics of Wind Turbines with topics ranging from Fundamental to Application of horizontal axis wind turbines, this book presents advanced topics including: Basic Theory for Wind turbine Blade Aerodynamics, Computational Methods, and Special Structural Reinforcement Technique for Wind Turbine Blades.

  11. Leading Edge Device Aerodynamic Optimization

    Directory of Open Access Journals (Sweden)

    Marius Gabriel COJOCARU

    2015-12-01

    Full Text Available Leading edge devices are conventionally used as aerodynamic devices that enhance performances during landing and in some cases during takeoff. The need to increase the efficiency of the aircrafts has brought the idea of maintaining as much as possible a laminar flow over the wings. This is possible only when the leading edge of the wings is free from contamination, therefore using the leading edge devices with the additional role of shielding during takeoff. Such a device based on the Krueger flap design is aerodynamically analyzed and optimized. The optimization comprises three steps: first, the positioning of the flap such that the shielding criterion is kept, second, the analysis of the flap size and third, the optimization of the flap shape. The first step is subject of a gradient based optimization process of the position described by two parameters, the position along the line and the deflection angle. For the third step the Adjoint method is used to gain insight on the shape of the Krueger flap that will extend the most the stall limit. All these steps have been numerically performed using Ansys Fluent and the results are presented for the optimized shape in comparison with the baseline configuration.

  12. Perching aerodynamics and trajectory optimization

    Science.gov (United States)

    Wickenheiser, Adam; Garcia, Ephrahim

    2007-04-01

    Advances in smart materials, actuators, and control architecture have enabled new flight capabilities for aircraft. Perching is one such capability, described as a vertical landing maneuver using in-flight shape reconfiguration in lieu of high thrust generation. A morphing, perching aircraft design is presented that is capable of post stall flight and very slow landing on a vertical platform. A comprehensive model of the aircraft's aerodynamics, with special regard to nonlinear affects such as flow separation and dynamic stall, is discussed. Trajectory optimization using nonlinear programming techniques is employed to show the effects that morphing and nonlinear aerodynamics have on the maneuver. These effects are shown to decrease the initial height and distance required to initiate the maneuver, reduce the bounds on the trajectory, and decrease the required thrust for the maneuver. Perching trajectories comparing morphing versus fixed-configuration and stalled versus un-stalled aircraft are presented. It is demonstrated that a vertical landing is possible in the absence of high thrust if post-stall flight capabilities and vehicle reconfiguration are utilized.

  13. A Study of Aerodynamics in Kevlar-Wall Test Sections

    OpenAIRE

    Brown, Kenneth Alexander

    2014-01-01

    This study is undertaken to characterize the aerodynamic behavior of Kevlar-wall test sections and specifically those containing two-dimensional, lifting models. The performance of the Kevlar-wall test section can be evaluated against the standard of the hard-wall test section, which in the case of the Stability Wind Tunnel (SWT) at Virginia Tech can be alternately installed or replaced by the Kevlar-wall test section. As a first step towards the evaluation of the Kevlar-wall test section aer...

  14. Rudolf Hermann, wind tunnels and aerodynamics

    Science.gov (United States)

    Lundquist, Charles A.; Coleman, Anne M.

    2008-04-01

    Rudolf Hermann was born on December 15, 1904 in Leipzig, Germany. He studied at the University of Leipzig and at the Aachen Institute of Technology. His involvement with wind tunnels began in 1934 when Professor Carl Wieselsberger engaged him to work at Aachen on the development of a supersonic wind tunnel. On January 6, 1936, Dr. Wernher von Braun visited Dr. Hermann to arrange for use of the Aachen supersonic wind tunnel for Army problems. On April 1, 1937, Dr. Hermann became Director of the Supersonic Wind Tunnel at the Army installation at Peenemunde. Results from the Aachen and Peenemunde wind tunnels were crucial in achieving aerodynamic stability for the A-4 rocket, later designated as the V-2. Plans to build a Mach 10 'hypersonic' wind tunnel facility at Kochel were accelerated after the Allied air raid on Peenemunde on August 17, 1943. Dr. Hermann was director of the new facility. Ignoring destruction orders from Hitler as WWII approached an end in Europe, Dr. Hermann and his associates hid documents and preserved wind tunnel components that were acquired by the advancing American forces. Dr. Hermann became a consultant to the Air Force at its Wright Field in November 1945. In 1951, he was named professor of Aeronautical Engineering at the University of Minnesota. In 1962, Dr. Hermann became the first Director of the Research Institute at the University of Alabama in Huntsville (UAH), a position he held until he retired in 1970.

  15. On the Dynamic Stability of a Missile

    Directory of Open Access Journals (Sweden)

    K.C. Sharma

    1977-01-01

    Full Text Available The P-method given by Parks and Pritchard has been used to discuss the stability behaviour of a missile in free flight. General stability criteria for aerodynamic stabilisation have been obtained for slowly varying coefficients. The effect of pressure gradient on the stability of a coasting rocket has been explicitly examined. It is observed that the positive Magnus moment parameter ensures stability whereas a negative moment parameter would enhance the requirements of a larger stability margin.

  16. Stability of Rocket Flight during Burning

    Directory of Open Access Journals (Sweden)

    T. N. Srivastava

    1967-10-01

    Full Text Available Stability of the rocket motion during burning is discussed taking into consideration gravity, aerodynamic forces and torques. Conditions for stabilizing the rocket motion are investigated. Analysis for initial and final phases of burning is given separately. Stability regions of the projected motions on two dimensional co-ordinate planes are obtained and thereby stability region of the actual motion is derived. Stability diagrams illustrate statically and dynamically stable and unstable regions.

  17. Entry dynamics of space shuttle orbiter with longitudinal stability and control uncertainties at supersonic and hypersonic speeds

    Science.gov (United States)

    Stone, H. W.; Powell, R. W.

    1977-01-01

    A six-degree-of-freedom simulation analysis was conducted to examine the effects of longitudinal static aerodynamic stability and control uncertainties on the performance of the space shuttle orbiter automatic (no manual inputs) entry guidance and control systems. To establish the acceptable boundaries, the static aerodynamic characteristics were varied either by applying a multiplier to the aerodynamic parameter or by adding an increment. With either of two previously identified control system modifications included, the acceptable longitudinal aerodynamic boundaries were determined.

  18. Understanding and Exploiting Wind Tunnels with Porous Flexible Walls for Aerodynamic Measurement

    OpenAIRE

    Brown, Kenneth Alexander

    2016-01-01

    The aerodynamic behavior of wind tunnels with porous, flexible walls formed from tensioned Kevlar has been characterized and new measurement techniques in such wind tunnels explored. The objective is to bring the aerodynamic capabilities of so-called Kevlar-wall test sections in-line with those of traditional solid-wall test sections. The primary facility used for this purpose is the 1.85-m by 1.85-m Stability Wind Tunnel at Virginia Tech, and supporting data is provided by the 2-m by 2-m L...

  19. On cup anemometer rotor aerodynamics.

    Science.gov (United States)

    Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio

    2012-01-01

    The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.

  20. Aerodynamic research on tipvane windturbines

    Science.gov (United States)

    Vanbussel, G. J. W.; Vanholten, T.; Vankuik, G. A. M.

    1982-09-01

    Tipvanes are small auxiliary wings mounted at the tips of windturbine blades in such a way that a diffuser effect is generated, resulting in a mass flow augmentation through the turbine disc. For predicting aerodynamic loads on the tipvane wind turbine, the acceleration potential is used and an expansion method is applied. In its simplest form, this method can essentially be classified as a lifting line approach, however, with a proper choice of the basis load distributions of the lifting line, the numerical integration of the pressurefield becomes one dimensional. the integration of the other variable can be performed analytically. The complete analytical expression for the pressure field consists of two series of basic pressure fields. One series is related to the basic load distributions over the turbineblade, and the other series to the basic load distribution over the tipvane.

  1. Rarefaction Effects in Hypersonic Aerodynamics

    Science.gov (United States)

    Riabov, Vladimir V.

    2011-05-01

    The Direct Simulation Monte-Carlo (DSMC) technique is used for numerical analysis of rarefied-gas hypersonic flows near a blunt plate, wedge, two side-by-side plates, disk, torus, and rotating cylinder. The role of various similarity parameters (Knudsen and Mach numbers, geometrical and temperature factors, specific heat ratios, and others) in aerodynamics of the probes is studied. Important kinetic effects that are specific for the transition flow regime have been found: non-monotonic lift and drag of plates, strong repulsive force between side-by-side plates and cylinders, dependence of drag on torus radii ratio, and the reverse Magnus effect on the lift of a rotating cylinder. The numerical results are in a good agreement with experimental data, which were obtained in a vacuum chamber at low and moderate Knudsen numbers from 0.01 to 10.

  2. Aerodynamic seals for rotary machine

    Energy Technology Data Exchange (ETDEWEB)

    Bidkar, Rahul Anil; Cirri, Massimiliano; Thatte, Azam Mihir; Williams, John Robert

    2016-02-09

    An aerodynamic seal assembly for a rotary machine includes multiple sealing device segments disposed circumferentially intermediate to a stationary housing and a rotor. Each of the segments includes a shoe plate with a forward-shoe section and an aft-shoe section having multiple labyrinth teeth therebetween facing the rotor. The sealing device segment also includes multiple flexures connected to the shoe plate and to a top interface element, wherein the multiple flexures are configured to allow the high pressure fluid to occupy a forward cavity and the low pressure fluid to occupy an aft cavity. Further, the sealing device segments include a secondary seal attached to the top interface element at one first end and positioned about the flexures and the shoe plate at one second end.

  3. On Cup Anemometer Rotor Aerodynamics

    Directory of Open Access Journals (Sweden)

    Santiago Pindado

    2012-05-01

    Full Text Available The influence of anemometer rotor shape parameters, such as the cups’ front area or their center rotation radius on the anemometer’s performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal, tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups’ center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor’s cup.

  4. Investigation of lateral-directional aerodynamic parameters identification method for fly-by-wire passenger airliners

    Institute of Scientific and Technical Information of China (English)

    Wu Zhao; Wang Lixin; Lin Jiaming; Ai Junqiang

    2014-01-01

    A new identification method is proposed to solve the problem of the influence on the loaded excitation signals brought by high feedback gain augmentation in lateral-directional aerody-namic parameters identification of fly-by-wire (FBW) passenger airliners. Taking for example an FBW passenger airliner model with directional relaxed-static-stability, through analysis of its signal energy distribution and airframe frequency response, a new method is proposed for signal type selec-tion, signal parameters design, and the appropriate frequency relationship between the aileron and rudder excitation signals. A simulation validation is presented of the FBW passenger airliner’s lat-eral-directional aerodynamic parameters identification. The validation result demonstrates that the designed signal can excite the lateral-directional motion mode of the FBW passenger airliner ade-quately and persistently. Meanwhile, the relative errors of aerodynamic parameters are less than 5%.

  5. Aerodynamic Efficiency Enhancements for Air Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The need for aerodynamics-based efficiency enhancements for air vehicles is presented. Concepts are presented for morphing aircraft, to enable the aircraft to...

  6. Prediction of Unsteady Transonic Aerodynamics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An accurate prediction of aero-elastic effects depends on an accurate prediction of the unsteady aerodynamic forces. Perhaps the most difficult speed regime is...

  7. Aerodynamic Efficiency Enhancements for Air Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The need for aerodynamics-based efficiency enhancements for air vehicles is presented. The results of the Phase I investigation of concepts for morphing aircraft are...

  8. Aerodynamic flight control to increase payload capability of future launch vehicles

    Science.gov (United States)

    Cochran, John E., Jr.; Cheng, Y.-M.; Leleux, Todd; Bigelow, Scott; Hasbrook, William

    1993-01-01

    In this report, we provide some examples of French, Russian, Chinese, and Japanese launch vehicles that have utilized fins in their designs. Next, the aerodynamic design of the fins is considered in Section 3. Some comments on basic static stability and control theory are followed by a brief description of an aerodynamic characteristics prediction code that was used to estimate the characteristics of a modified NLS 1.5 Stage vehicle. Alternative fin designs are proposed and some estimated aerodynamic characteristics presented and discussed. Also included in Section 3 is a discussion of possible methods of enhancement of the aerodynamic efficiency of fins, such as vortex generators and jet flaps. We consider the construction of fins for launch vehicles in Section 4 and offer an assessment of the state-of-the-art in the use of composites for aerodynamic control surfaces on high speed vehicles. We also comment on the use of smart materials for launch vehicle fins. The dynamic stability and control of a launch vehicle that utilizes both thrust vector control (engine nozzle gimballing) and movable fins is the subject addressed in Section 5. We give a short derivation of equations of motion for a launch vehicle moving in a vertical plane above a spherical earth, discuss the use of a gravity-turn nominal trajectory, and give the form of the period equations linearized about such a nominal. We then consider feedback control of vehicle attitude using both engine gimballing and fin deflection. Conclusions are stated and recommendations made in Section 6. An appendix contains aerodynamic data in tabular and graphical formats.

  9. Aerodynamic drag of modern soccer balls

    OpenAIRE

    Asai, Takeshi; SEO, KAZUYA

    2013-01-01

    Soccer balls such as the Adidas Roteiro that have been used in soccer tournaments thus far had 32 pentagonal and hexagonal panels. Recently, the Adidas Teamgeist II and Adidas Jabulani, respectively having 14 and 8 panels, have been used at tournaments; the aerodynamic characteristics of these balls have not yet been verified. Now, the Adidas Tango 12, having 32 panels, has been developed for use at tournaments; therefore, it is necessary to understand its aerodynamic characteristics. Through...

  10. The Aerodynamics of High Speed Aerial Weapons

    OpenAIRE

    Prince, Simon A.

    1999-01-01

    The focus of this work is the investigation of the complex compressible flow phenomena associated with high speed aerial weapons. A three dimen- sional multiblock finite volume flow solver was developed with the aim of studying the aerodynamics of missile configurations and their component structures. The first component of the study involved the aerodynamic investigation of the isolated components used in the design of conventional missile config- urations. The computati...

  11. Spacecraft aerodynamics and trajectory simulation during aerobraking

    Institute of Scientific and Technical Information of China (English)

    Wen-pu ZHANG; Bo HAN; Cheng-yi ZHANG

    2010-01-01

    This paper uses a direct simulation Monte Carlo(DSMC)approach to simulate rarefied aerodynamic characteristics during the aerobraking process of the NASA Mars Global Surveyor(MGS)spacecraft.The research focuses on the flowfield and aerodynamic characteristics distribution under various free stream densities.The variation regularity of aerodynamic coefficients is analyzed.The paper also develops an aerodynamics-aeroheating-trajectory integrative simulation model to preliminarily calculate the aerobraking orbit transfer by combining the DSMC technique and the classical kinematics theory.The results show that the effect of the planetary atmospheric density,the spacecraft yaw,and the pitch attitudes on the spacecraft aerodynamics is significant.The numerical results are in good agreement with the existing results reported in the literature.The aerodynamics-aeroheating-trajectory integrative simulation model can simulate the orbit tran,sfer in the complete aerobraking mission.The current results of the spacecraft trajectory show that the aerobraking maneuvers have good performance of attitude control.

  12. Skylon Aerodynamics and SABRE Plumes

    Science.gov (United States)

    Mehta, Unmeel; Afosmis, Michael; Bowles, Jeffrey; Pandya, Shishir

    2015-01-01

    An independent partial assessment is provided of the technical viability of the Skylon aerospace plane concept, developed by Reaction Engines Limited (REL). The objectives are to verify REL's engineering estimates of airframe aerodynamics during powered flight and to assess the impact of Synergetic Air-Breathing Rocket Engine (SABRE) plumes on the aft fuselage. Pressure lift and drag coefficients derived from simulations conducted with Euler equations for unpowered flight compare very well with those REL computed with engineering methods. The REL coefficients for powered flight are increasingly less acceptable as the freestream Mach number is increased beyond 8.5, because the engineering estimates did not account for the increasing favorable (in terms of drag and lift coefficients) effect of underexpanded rocket engine plumes on the aft fuselage. At Mach numbers greater than 8.5, the thermal environment around the aft fuselage is a known unknown-a potential design and/or performance risk issue. The adverse effects of shock waves on the aft fuselage and plumeinduced flow separation are other potential risks. The development of an operational reusable launcher from the Skylon concept necessitates the judicious use of a combination of engineering methods, advanced methods based on required physics or analytical fidelity, test data, and independent assessments.

  13. Aerodynamic Analysis of Morphing Blades

    Science.gov (United States)

    Harris, Caleb; Macphee, David; Carlisle, Madeline

    2016-11-01

    Interest in morphing blades has grown with applications for wind turbines and other aerodynamic blades. This passive control method has advantages over active control methods such as lower manufacturing and upkeep costs. This study has investigated the lift and drag forces on individual blades with experimental and computational analysis. The goal has been to show that these blades delay stall and provide larger lift-to-drag ratios at various angles of attack. Rigid and flexible airfoils were cast from polyurethane and silicone respectively, then lift and drag forces were collected from a load cell during 2-D testing in a wind tunnel. Experimental data was used to validate computational models in OpenFOAM. A finite volume fluid-structure-interaction solver was used to model the flexible blade in fluid flow. Preliminary results indicate delay in stall and larger lift-to-drag ratios by maintaining more optimal angles of attack when flexing. Funding from NSF REU site Grant EEC 1358991 is greatly appreciated.

  14. Modeling Powered Aerodynamics for the Orion Launch Abort Vehicle Aerodynamic Database

    Science.gov (United States)

    Chan, David T.; Walker, Eric L.; Robinson, Philip E.; Wilson, Thomas M.

    2011-01-01

    Modeling the aerodynamics of the Orion Launch Abort Vehicle (LAV) has presented many technical challenges to the developers of the Orion aerodynamic database. During a launch abort event, the aerodynamic environment around the LAV is very complex as multiple solid rocket plumes interact with each other and the vehicle. It is further complicated by vehicle separation events such as between the LAV and the launch vehicle stack or between the launch abort tower and the crew module. The aerodynamic database for the LAV was developed mainly from wind tunnel tests involving powered jet simulations of the rocket exhaust plumes, supported by computational fluid dynamic simulations. However, limitations in both methods have made it difficult to properly capture the aerodynamics of the LAV in experimental and numerical simulations. These limitations have also influenced decisions regarding the modeling and structure of the aerodynamic database for the LAV and led to compromises and creative solutions. Two database modeling approaches are presented in this paper (incremental aerodynamics and total aerodynamics), with examples showing strengths and weaknesses of each approach. In addition, the unique problems presented to the database developers by the large data space required for modeling a launch abort event illustrate the complexities of working with multi-dimensional data.

  15. Discrete vortex method simulations of the aerodynamic admittance in bridge aerodynamics

    DEFF Research Database (Denmark)

    Rasmussen, Johannes Tophøj; Hejlesen, Mads Mølholm; Larsen, Allan;

    2010-01-01

    We present a novel method for the simulation of the aerodynamic admittance in bluff body aerodynamics. The method introduces a model for describing oncoming turbulence in two-dimensional discrete vortex method simulations by seeding the upstream flow with vortex particles. The turbulence...

  16. Aerodynamics and combustion of axial swirlers

    Science.gov (United States)

    Fu, Yongqiang

    A multipoint lean direct injection (LDI) concept was introduced recently in non-premixed combustion to obtain both low NOx emissions and good combustion stability. In this concept, a key feature is the injection of finely atomized fuel into the high-swirling airflow at the combustor dome that provides a homogenous, lean fuel-air mixture. In order to achieve the fine atomization and mixing of the fuel and air quickly and uniformly, a good swirler design should be studied. The focus of this dissertation is to investigate the aerodynamics and combustion of the swirling flow field in a multipoint Lean Direct Injector combustor. A helical axial-vaned swirler with a short internal convergent-divergent venturi was used. Swirlers with various vane angles and fuel nozzle insertion lengths have been designed. Three non-dimensional parameter effects on non-reacting, swirling flow field were studied: swirler number, confinement ratio and Reynolds number. Spray and combustion characteristics on the single swirler were studied to understand the mechanism of fuel-air mixing in this special configuration. Multi-swirler interactions were studied by measuring the confined flow field of a multipoint swirler array with different configurations. Two different swirler arrangements were investigated experimentally, which include a co-swirling array and a counter-swirling array. In order to increase the range of stability of multipoint LDI combustors, an improved design were also conducted. The results show that the degree of swirl and the level of confinement have a clear impact on the mean and turbulent flow fields. The swirling flow fields may also change significantly with the addition of a variety of simulated fuel nozzle insertion lengths. The swirler with short insertion has the stronger swirling flow as compared with the long insertion swirler. Reynolds numbers, with range of current study, will not alter mean and turbulent properties of generated flows. The reaction of the spray

  17. Numerical Investigation of Aerodynamic Performance and Loads of a Novel Dual Rotor Wind Turbine

    Directory of Open Access Journals (Sweden)

    Behnam Moghadassian

    2016-07-01

    Full Text Available The objective of this paper is to numerically investigate the effects of the atmospheric boundary layer on the aerodynamic performance and loads of a novel dual-rotor wind turbine (DRWT. Large eddy simulations are carried out with the turbines operating in the atmospheric boundary layer (ABL and in a uniform inflow. Two stability conditions corresponding to neutral and slightly stable atmospheres are investigated. The turbines are modeled using the actuator line method where the rotor blades are modeled as body forces. Comparisons are drawn between the DRWT and a comparable conventional single-rotor wind turbine (SRWT to assess changes in aerodynamic efficiency and loads, as well as wake mixing and momentum and kinetic energy entrainment into the turbine wake layer. The results show that the DRWT improves isolated turbine aerodynamic performance by about 5%–6%. The DRWT also enhances turbulent axial momentum entrainment by about 3.3 %. The highest entrainment is observed in the neutral stability case when the turbulence in the ABL is moderately high. Aerodynamic loads for the DRWT, measured as out-of-plane blade root bending moment, are marginally reduced. Spectral analyses of ABL cases show peaks in unsteady loads at the rotor passing frequency and its harmonics for both rotors of the DRWT.

  18. In vivo recording of aerodynamic force with an aerodynamic force platform

    CERN Document Server

    Lentink, David; Ingersoll, Rivers

    2014-01-01

    Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on tethered experiments with robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here we demonstrate a new aerodynamic force platform (AFP) for nonintrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is ...

  19. Bat flight: aerodynamics, kinematics and flight morphology.

    Science.gov (United States)

    Hedenström, Anders; Johansson, L Christoffer

    2015-03-01

    Bats evolved the ability of powered flight more than 50 million years ago. The modern bat is an efficient flyer and recent research on bat flight has revealed many intriguing facts. By using particle image velocimetry to visualize wake vortices, both the magnitude and time-history of aerodynamic forces can be estimated. At most speeds the downstroke generates both lift and thrust, whereas the function of the upstroke changes with forward flight speed. At hovering and slow speed bats use a leading edge vortex to enhance the lift beyond that allowed by steady aerodynamics and an inverted wing during the upstroke to further aid weight support. The bat wing and its skeleton exhibit many features and control mechanisms that are presumed to improve flight performance. Whereas bats appear aerodynamically less efficient than birds when it comes to cruising flight, they have the edge over birds when it comes to manoeuvring. There is a direct relationship between kinematics and the aerodynamic performance, but there is still a lack of knowledge about how (and if) the bat controls the movements and shape (planform and camber) of the wing. Considering the relatively few bat species whose aerodynamic tracks have been characterized, there is scope for new discoveries and a need to study species representing more extreme positions in the bat morphospace.

  20. Aerodynamic Control of a Pitching Airfoil by Distributed Bleed Actuation

    Science.gov (United States)

    Kearney, John; Glezer, Ari

    2013-11-01

    The aerodynamic forces and moments on a dynamically pitching 2-D airfoil model are controlled in wind tunnel experiments using distributed active bleed. Bleed flow on the suction surface downstream of the leading edge is driven by pressure differences across the airfoil and is regulated by low-power louver actuators. The bleed interacts with cross flows to effect time-dependent variations of the vorticity flux and thereby alters the local flow attachment, resulting in significant changes in pre- and post-stall lift and pitching moment (over 50% increase in baseline post-stall lift). The flow field over the airfoil is measured using high-speed (2000 fps) PIV, resolving the dynamics and characteristic time-scales of production and advection of vorticity concentrations that are associated with transient variations in the aerodynamic forces and moments. In particular, it is shown that the actuation improves the lift hysteresis and pitch stability during the oscillatory pitching by altering the evolution of the dynamic stall vortex and the ensuing flow attachment during the downstroke. Supported by the Rotorcraft Center (VLRCOE) at Georgia Tech.

  1. Wing Warping and Its Impact on Aerodynamic Efficiency

    Science.gov (United States)

    Loh, Ben; Jacob, Jamey

    2007-11-01

    Inflatable wings have been demonstrated in many applications such as UAVs, airships, and missile stabilization surfaces. A major concern presented by the use of an inflatable wing has been the lack of traditional roll control surfaces. This leaves the designer with several options in order to have control about the roll axis. Since inflatable wings have a semi-flexible structure, wing warping is the obvious solution to this problem. The current method is to attach servos and control linkages to external surface of the wing that results in variation of profile chamber and angle of attack from leading edge or trailing edge deflection. Designs using internal muscles will also be discussed. This creates a lift differential between the half-spans, resulting in a roll moment. The trailing edge on the other half-span can also be deflected in the opposite direction to increase the roll moment as well as to reduce roll-yaw coupling. Comparisons show that higher L/D ratios are possible than using traditional control surfaces. An additional benefit is the ability to perform symmetric warping to achieve optimum aerodynamic performance. Via warping alone, an arbitrary span can be warped such that it has the same aerodynamic characteristics as an elliptical planform. Comparisons between lifting line theory and test results will be presented.

  2. Aerodynamic Modeling and Parameter Estimation from QAR Data of an Airplane Approaching a High-altitude Airport

    Institute of Scientific and Technical Information of China (English)

    WANG Qing; WU Kaiyuan; ZHANG Tianjiao; KONG Yi'nan; QIAN Weiqi

    2012-01-01

    Aerodynamic modeling and parameter estimation from quick accesses recorder (QAR) data is an important technical way to analyze the effects of highland weather conditions upon aerodynamic characteristics of airplane.It is also an essential content of flight accident analysis.The related techniques are developed in the present paper,including the geometric method for angle of attack and sideslip angle estimation,the extended Kalman filter associated with modified Bryson-Frazier smoother (EKF-MBF) method for aerodynamic coefficient identification,the radial basis function (RBF) neural network method for aerodynamic modeling,and the Delta method for stability/control derivative estimation.As an application example,the QAR data of a civil airplane approaching a high-altitude airport are processed and the aerodynamic coefficient and derivative estimates are obtained.The estimation results are reasonable,which shows that the developed techniques are feasible.The causes for the distribution of aerodynamic derivative estimates are analyzed.Accordingly,several measures to improve estimation accuracy are put forward.

  3. Entry dynamics of space shuttle orbiter with lateral-directional stability and control uncertainties at supersonic and hypersonic speeds

    Science.gov (United States)

    Stone, H. W.; Powell, R. W.

    1977-01-01

    A six-degree-of-freedom simulation analysis was conducted to examine the effects of the lateral-directional static aerodynamic stability and control uncertainties on the performance of the automatic (no manual inputs) entry-guidance and control systems of the space shuttle orbiter. To establish the acceptable boundaries of the uncertainties, the static aerodynamic characteristics were varied either by applying a multiplier to the aerodynamic parameter or by adding an increment. Control-system modifications were identified that decrease the sensitivity to off-nominal aerodynamics. With these modifications, the acceptable aerodynamic boundaries were determined.

  4. Influence of Icing on Bridge Cable Aerodynamics

    DEFF Research Database (Denmark)

    Koss, Holger; Frej Henningsen, Jesper; Olsen, Idar

    2013-01-01

    In recent years the relevance of ice accretion for wind-induced vibration of structural bridge cables has been recognised and became a subject of research in bridge engineering. Full-scale monitoring and observation indicate that light precipitation at moderate low temperatures between zero and -5......°C may lead to large amplitude vibrations of bridge cables under wind action. For the prediction of aerodynamic instability quasi-steady models have been developed estimating the cable response magnitude based on structural properties and aerodynamic force coefficients for drag, lift and torsion....... The determination of these force coefficients require a proper simulation of the ice layer occurring under the specific climatic conditions, favouring real ice accretion over simplified artificial reproduction. The work presented in this paper was performed to study the influence of ice accretion on the aerodynamic...

  5. Aerodynamic Jump for Long Rod Penetrators

    Directory of Open Access Journals (Sweden)

    Mark L. Bundy

    2000-04-01

    Full Text Available Aerodynamic jump for a non-spinning kinetic energy penetrator is neither a discontinuous change in the ,direction of motion at the origin of free night, nor is it the converse, i.e. a cumulativer~direc4on over a domain of infinite extent. Rather aerodynamic jump, for such a projectile, is a localised redirection of the centre of gravity motion, caused ~ the force of lift due to yaw over ther4latively short region from entry into free flight until the yaw reaches its first maximum. The primary objective of this paper is to provide answtfrs to the questions like what is aerodynamic jump, what liauses it, !lnd wh~t aspects df the flight trajectory does it refer to, or account for .

  6. Photogrammetry of a Hypersonic Inflatable Aerodynamic Decelerator

    Science.gov (United States)

    Kushner, Laura Kathryn; Littell, Justin D.; Cassell, Alan M.

    2013-01-01

    In 2012, two large-scale models of a Hypersonic Inflatable Aerodynamic decelerator were tested in the National Full-Scale Aerodynamic Complex at NASA Ames Research Center. One of the objectives of this test was to measure model deflections under aerodynamic loading that approximated expected flight conditions. The measurements were acquired using stereo photogrammetry. Four pairs of stereo cameras were mounted inside the NFAC test section, each imaging a particular section of the HIAD. The views were then stitched together post-test to create a surface deformation profile. The data from the photogram- metry system will largely be used for comparisons to and refinement of Fluid Structure Interaction models. This paper describes how a commercial photogrammetry system was adapted to make the measurements and presents some preliminary results.

  7. A note on stability of motion of a projectile

    Indian Academy of Sciences (India)

    S D Naik

    2001-08-01

    A projectile is stabilised using either gyroscopic or aerodynamic stability. But subcalibre projectiles with sabot have both spin and fins. Separate stability criteria are researched generally for each type of projectile. In this paper a stability criterion which can be used for all such bodies has been developed through the Liapunov second method.

  8. Prediction of aerodynamic performance for MEXICO rotor

    DEFF Research Database (Denmark)

    Hong, Zedong; Yang, Hua; Xu, Haoran

    2013-01-01

    The aerodynamic performance of the MEXICO (Model EXperiments In Controlled cOnditions) rotor at five tunnel wind speeds is predicted by making use of BEM and CFD methods, respectively, using commercial MATLAB and CFD software. Due to the pressure differences on both sides of the blade, the tip...... the reliability of the MEXICO data. Second, the SST turbulence model can better capture the flow separation on the blade and has high aerodynamic performance prediction accuracy for a horizontal axis wind turbine in axial inflow conditions. Finally, the comparisons of the axial and tangential forces as well...

  9. Aerodynamic Jump for Long Rod Penetrators

    OpenAIRE

    Mark L. Bundy

    2000-01-01

    Aerodynamic jump for a non-spinning kinetic energy penetrator is neither a discontinuous change in the ,direction of motion at the origin of free night, nor is it the converse, i.e. a cumulativer~direc4on over a domain of infinite extent. Rather aerodynamic jump, for such a projectile, is a localised redirection of the centre of gravity motion, caused ~ the force of lift due to yaw over ther4latively short region from entry into free flight until the yaw reaches its first maximum. The primary...

  10. Estimation of nonlinear aerodynamic derivatives of a variable geometry fighter aircraft from flight data

    Science.gov (United States)

    Ramachandran, S.; Wells, W. R.

    1974-01-01

    This paper is concerned with the estimation of stability and control parameters of a high performance fighter aircraft from data obtained from high angle of attack flight. The estimation process utilizes a maximum likelihood algorithm derived for the case of a nonlinear aerodynamic force and moment model. The aircraft used was a high speed variable sweep heavy weight fighter with twin vertical tails. Comparisons of results from the nonlinear analysis are made with linear theory and wind tunnel results when available.

  11. Experimental Analysis of Aerodynamic Aspects of Sport Utility Vehicle

    Directory of Open Access Journals (Sweden)

    DINESH Y DHANDE

    2013-07-01

    Full Text Available In an era fuel efficiency has become topic of discussion not only among the scholar researchers but also common men. As rapid and continuous increase in prizes of fuels consumers are going for most fuel efficient vehicles. By aerodynamic styling of vehicle one can not only improve the fuel efficiency but also ensure better stability and good handling characteristics of vehicles at higher speed especially on highways. The paper describes assessment of drag force (Fd and drag coefficient (Cd by conventional wind tunnel method. Theexperimental calculations were performed on subsonic wind tunnel having test section of 100cm x 30cm x 30 cm. Exact replica of model of sports utility vehicle (suv on reduced scale 1:32 is used to for experimentation to calculate Fd and Cd.

  12. SOFIA Closed- and Open-Door Aerodynamic Analyses

    Science.gov (United States)

    Cumming, Stephen; Frederick, Mike; Smith, Mark

    2012-01-01

    Work to evaluate the aerodynamic characteristics and the cavity acoustic environment of the SOFIA (Stratospheric Observatory for Infrared Astronomy) airplane has been completed. The airplane has been evaluated in its closed-door configuration, as well as several open-door configurations. Work performed included: acoustic analysis tool development, cavity acoustic evaluation, stability and control parameter estimation, air data calibration, and external flow evaluation. Qualitative airflow data were obtained during the closed- and open-door flights using tufts on the aft portion of the fuselage. Video was taken from a chase plane. This video was analyzed for various flight conditions, and general flow descriptions of the aft fuselage of the 747SP were developed for the different closed and open door configurations.

  13. External Aerodynamics Simulations in a Rotating Frame of Reference

    Directory of Open Access Journals (Sweden)

    Filomena Cariglino

    2014-01-01

    Full Text Available This paper presents the development of a tool integrated in the UNS3D code, proprietary of Alenia Aermacchi, for the simulation of external aerodynamic flow in a rotating reference frame, with the main objective of predicting propeller-aircraft integration effects. The equations in a rotating frame of reference have been formulated in terms of the absolute velocity components; in this way, the artificial dissipation needed for convergence is lessened, as the Coriolis source term is only introduced in the momentum equation. An Explicit Algebraic Reynolds Stress turbulence model is used. The first assessment of effectiveness of this method is made computing stability derivatives of a NACA 0012 airfoil. Finally, steady Navier-Stokes and Euler simulations of a four-blade single-rotating propeller are presented, demonstrating the efficiency of the chosen approach in terms of computational cost.

  14. Two cases of aerodynamic adjustment of sastrugi

    Directory of Open Access Journals (Sweden)

    C. Amory

    2015-11-01

    Full Text Available In polar regions, sastrugi are a direct manifestation of wind driven snow and form the main surface roughness elements. In turn, sastrugi influence the local wind field and associated aeolian snow mass fluxes. Little attention has been paid to these feedback processes, mainly because of experimental difficulties, and, as a result most polar atmospheric models currently ignore sastrugi. More accurate quantification of the influence of sastrugi remains a major challenge. In the present study, wind profiles and aeolian snow mass fluxes were analyzed jointly on a sastrugi covered snowfield in Antarctica. Neutral stability 10 m air-snow drag coefficients CDN10 were computed from six level wind speed profiles collected in Adélie Land during austral winter 2013. The aeolian snow mass flux in the first meter above the surface of the snow was also measured using a windborne snow acoustic sensor. This paper focuses on two cases during which sastrugi responses to shifts in wind direction were evidenced by variations in snow mass flux and drag coefficients. Using this dataset, it was shown that (i the timescale of sastrugi aerodynamic adjustment can be as short as 3 h for friction velocities of 1 m s−1 or above and during strong windborne snow conditions, (ii CDN10 values were in the range of 1.3–1.5 × 103 when the wind was well aligned with the sastrugi and increased to 3 × 103 or higher when the wind only shifted 20–30°, (iii CDN10 can increase (to 120 % and the aeolian snow mass flux can decrease (to 80 % in response to a shift in wind direction, and (iv knowing CDN10 is not sufficient to estimate the erosion flux that results from drag partitioning at the surface because CDN10 includes the contribution of the sastrugi form drag. These results not only support the existence of feedback mechanisms linking sastrugi, aeolian particle transport and surface drag properties over snow surface but also provide orders of magnitude, although further

  15. AERODYNAMICS OF WING TIP SAILS

    Directory of Open Access Journals (Sweden)

    MUSHTAK AL-ATABI

    2006-06-01

    Full Text Available Observers have always been fascinated by soaring birds. An interesting feature of these birds is the existence of few feathers extending from the tip of the wing. In this paper, small lifting surfaces were fitted to the tip of a NACA0012 wing in a fashion similar to that of wing tip feathers. Experimental measurements of induced drag, longitudinal static stability and trailing vortex structure were obtained.The tests showed that adding wing tip surfaces (sails decreased the induced drag factor and increased the longitudinal static stability. Results identified two discrete appositely rotated tip vortices and showed the ability of wing tip surfaces to break them down and to diffuse them.

  16. Flexible Launch Vehicle Stability Analysis Using Steady and Unsteady Computational Fluid Dynamics

    Science.gov (United States)

    Bartels, Robert E.

    2012-01-01

    Launch vehicles frequently experience a reduced stability margin through the transonic Mach number range. This reduced stability margin can be caused by the aerodynamic undamping one of the lower-frequency flexible or rigid body modes. Analysis of the behavior of a flexible vehicle is routinely performed with quasi-steady aerodynamic line loads derived from steady rigid aerodynamics. However, a quasi-steady aeroelastic stability analysis can be unconservative at the critical Mach numbers, where experiment or unsteady computational aeroelastic analysis show a reduced or even negative aerodynamic damping.Amethod of enhancing the quasi-steady aeroelastic stability analysis of a launch vehicle with unsteady aerodynamics is developed that uses unsteady computational fluid dynamics to compute the response of selected lower-frequency modes. The response is contained in a time history of the vehicle line loads. A proper orthogonal decomposition of the unsteady aerodynamic line-load response is used to reduce the scale of data volume and system identification is used to derive the aerodynamic stiffness, damping, and mass matrices. The results are compared with the damping and frequency computed from unsteady computational aeroelasticity and from a quasi-steady analysis. The results show that incorporating unsteady aerodynamics in this way brings the enhanced quasi-steady aeroelastic stability analysis into close agreement with the unsteady computational aeroelastic results.

  17. LINEAR AND NONLINEAR AERODYNAMIC THEORY OF INTERACTION BETWEEN FLEXIBLE LONG STRUCTURE AND WIND

    Institute of Scientific and Technical Information of China (English)

    徐旭; 曹志远

    2001-01-01

    In light of the characteristics of the interactions between flexible structure and wind in three directions, and based on the rational mechanical section-model of structure, a new aerodynamic force model is accepted, i. e. the coefficients of three component forces are the functions of the instantaneous attack angle and rotational speed Ci = Ci(β(t),θ),(i = D, L, M). So, a new method to formulate the linear and nonlinear aerodynamic items of wind and structure interacting has been put forward in accordance with "strip theory"and modified "quasi-static theory ", and then the linear and nonlinear coupled theory of super-slender structure for civil engineering analyzing are converged in one model. For the linear aerodynamic-force parts, the semi-analytical expressions of the items so-called "flutter derivatives" corresponding to the one in the classic equations have been given here,and so have the nonlinear parts. The study of the stability of nonlinear aerodynamic-coupled torsional vibration of the old Tacoma bridge shows that the form and results of the nonlinear control equation in rotational direction are in agreement with that of V. F. Bohm's.

  18. Transitory Control of the Aerodynamic Loads on an Airfoil in Dynamic Pitch and Plunge

    Science.gov (United States)

    Tan, Yuehan; Crittenden, Thomas; Glezer, Ari

    2016-11-01

    Transitory control and regulation of trapped vorticity concentrations are exploited in wind tunnel experiments for control of the aerodynamic loads on an airfoil moving in time-periodic 2-DOF (pitch and plunge) beyond the dynamic stall margin. Actuation is effected using a spanwise array of integrated miniature chemical (combustion based) high-impulse actuators that are triggered intermittently relative to the airfoil's motion. Each actuation pulse has sufficient control authority to alter the global aerodynamic performance throughout the motion cycle on a characteristic time scale that is an order of magnitude shorter than the airfoil's convective time scale. The effects of the actuation on the aerodynamic characteristics of the airfoil are assessed using time-dependent measurements of the lift force and pitching moment coupled with time-resolved particle image velocimetry that is acquired phased-locked to the motion of the airfoil. It is shown that the aerodynamic loads can be significantly altered using actuation programs based on multiple actuation pulses during the time-periodic pitch/plunge cycle. Superposition of such actuation programs leads to enhancement of cycle lift and pitch stability, and reduced cycle hysteresis and peak pitching moment. Supported by GT-VLRCOE.

  19. Flutter Derivatives Identification and Aerodynamic Performance of an Optimized Multibox Bridge Deck

    Directory of Open Access Journals (Sweden)

    Zhida Wang

    2016-01-01

    Full Text Available The bridge deck sections used for long-span suspension bridges have evolved through the years, from the compact box deck girders geometrical configurations to twin-box and three-box bridge decks sections. The latest generation of split and multiple-box bridge decks proved to have better aerodynamic behavior; thus further optimization methods are sought for such geometrical configurations. A new type of multibox bridge deck, consisting of four aerodynamically shaped deck boxes, two side decks for the traffic lanes and two middle decks for the railway traffic, connected between them by stabilizing beams, was tested in the wind tunnel for identifying the flutter derivatives and to verify the aerodynamic performance of the proposed multibox deck. Aerodynamic static force coefficients were measured for the multibox bridge deck model, scaled 1 : 80, for Reynolds numbers up to 5.1 × 105, under angles of attack between −8° and 8°. Iterative Least Squares (ILS method was employed for identifying the flutter derivatives of the multibox bridge deck model, based on the results obtained from the free vibration tests and based on the frequency analysis the critical flutter wind speed for the corresponding prototype of the multibox bridge was estimated at 188 m/s.

  20. Aerodynamic analysis of an isolated vehicle wheel

    Science.gov (United States)

    Leśniewicz, P.; Kulak, M.; Karczewski, M.

    2014-08-01

    Increasing fuel prices force the manufacturers to look into all aspects of car aerodynamics including wheels, tyres and rims in order to minimize their drag. By diminishing the aerodynamic drag of vehicle the fuel consumption will decrease, while driving safety and comfort will improve. In order to properly illustrate the impact of a rotating wheel aerodynamics on the car body, precise analysis of an isolated wheel should be performed beforehand. In order to represent wheel rotation in contact with the ground, presented CFD simulations included Moving Wall boundary as well as Multiple Reference Frame should be performed. Sliding mesh approach is favoured but too costly at the moment. Global and local flow quantities obtained during simulations were compared to an experiment in order to assess the validity of the numerical model. Results of investigation illustrates dependency between type of simulation and coefficients (drag and lift). MRF approach proved to be a better solution giving result closer to experiment. Investigation of the model with contact area between the wheel and the ground helps to illustrate the impact of rotating wheel aerodynamics on the car body.

  1. Efficient Global Aerodynamic Modeling from Flight Data

    Science.gov (United States)

    Morelli, Eugene A.

    2012-01-01

    A method for identifying global aerodynamic models from flight data in an efficient manner is explained and demonstrated. A novel experiment design technique was used to obtain dynamic flight data over a range of flight conditions with a single flight maneuver. Multivariate polynomials and polynomial splines were used with orthogonalization techniques and statistical modeling metrics to synthesize global nonlinear aerodynamic models directly and completely from flight data alone. Simulation data and flight data from a subscale twin-engine jet transport aircraft were used to demonstrate the techniques. Results showed that global multivariate nonlinear aerodynamic dependencies could be accurately identified using flight data from a single maneuver. Flight-derived global aerodynamic model structures, model parameter estimates, and associated uncertainties were provided for all six nondimensional force and moment coefficients for the test aircraft. These models were combined with a propulsion model identified from engine ground test data to produce a high-fidelity nonlinear flight simulation very efficiently. Prediction testing using a multi-axis maneuver showed that the identified global model accurately predicted aircraft responses.

  2. IEA joint action. Aerodynamics of wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Maribo Pedersen, B. [ed.

    1997-12-31

    In the period 1992-1997 the IEA Annex XIV `Field Rotor Aerodynamics` was carried out. Within its framework 5 institutes from 4 different countries participated in performing detailed aerodynamic measurements on full-scale wind turbines. The Annex was successfully completed and resulted in a unique database of aerodynamic measurements. The database is stored on an ECN disc (available through ftp) and on a CD-ROM. It is expected that this base will be used extensively in the development and validation of new aerodynamic models. Nevertheless at the end of IEA Annex XIV, it was recommended to perform a new IEA Annex due to the following reasons: In Annex XIV several data exchange rounds appeared to be necessary before a satisfactory result was achieved. This is due to the huge amount of data which had to be supplied, by which a thorough inspection of all data is very difficult and very time consuming; Most experimental facilities are still operational and new, very useful, measurements are expected in the near future; The definition of angle of attack and dynamic pressure in the rotating environment is less straightforward than in the wind tunnel. The conclusion from Annex XIV was that the uncertainty which results from these different definitions is still too large and more investigation in this field is required. (EG)

  3. Continuous Aerodynamic Modelling of Entry Shapes

    NARCIS (Netherlands)

    Dirkx, D.; Mooij, E.

    2011-01-01

    During the conceptual design phase of a re-entry vehicle, the vehicle shape can be varied and its impact on performance evaluated. To this end, the continuous modeling of the aerodynamic characteristics as a function of the shape is useful in exploring the full design space. Local inclination method

  4. In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds.

    Science.gov (United States)

    Lentink, David; Haselsteiner, Andreas F; Ingersoll, Rivers

    2015-03-06

    Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo. These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing.

  5. Aerodynamic shape optimization using control theory

    Science.gov (United States)

    Reuther, James

    1996-01-01

    Aerodynamic shape design has long persisted as a difficult scientific challenge due its highly nonlinear flow physics and daunting geometric complexity. However, with the emergence of Computational Fluid Dynamics (CFD) it has become possible to make accurate predictions of flows which are not dominated by viscous effects. It is thus worthwhile to explore the extension of CFD methods for flow analysis to the treatment of aerodynamic shape design. Two new aerodynamic shape design methods are developed which combine existing CFD technology, optimal control theory, and numerical optimization techniques. Flow analysis methods for the potential flow equation and the Euler equations form the basis of the two respective design methods. In each case, optimal control theory is used to derive the adjoint differential equations, the solution of which provides the necessary gradient information to a numerical optimization method much more efficiently then by conventional finite differencing. Each technique uses a quasi-Newton numerical optimization algorithm to drive an aerodynamic objective function toward a minimum. An analytic grid perturbation method is developed to modify body fitted meshes to accommodate shape changes during the design process. Both Hicks-Henne perturbation functions and B-spline control points are explored as suitable design variables. The new methods prove to be computationally efficient and robust, and can be used for practical airfoil design including geometric and aerodynamic constraints. Objective functions are chosen to allow both inverse design to a target pressure distribution and wave drag minimization. Several design cases are presented for each method illustrating its practicality and efficiency. These include non-lifting and lifting airfoils operating at both subsonic and transonic conditions.

  6. Wind turbines. Unsteady aerodynamics and inflow noise

    Energy Technology Data Exchange (ETDEWEB)

    Riget Broe, B.

    2009-12-15

    Aerodynamical noise from wind turbines due to atmospheric turbulence has the highest emphasis in semi-empirical models. However it is an open question whether inflow noise has a high emphasis. This illustrates the need to investigate and improve the semi-empirical model for noise due to atmospheric turbulence. Three different aerodynamical models are investigated in order to estimate the lift fluctuations due to unsteady aerodynamics. Two of these models are investigated to find the unsteady lift distribution or pressure difference as function of chordwise position on the aerofoil. An acoustic model is investigated using a model for the lift distribution as input. The two models for lift distribution are used in the acoustic model. One of the models for lift distribution is for completely anisotropic turbulence and the other for perfectly isotropic turbulence, and so is also the corresponding models for the lift fluctuations derived from the models for lift distribution. The models for lift distribution and lift are compared with pressure data which are obtained by microphones placed flush with the surface of an aerofoil. The pressure data are from two experiments in a wind tunnel, one experiment with a NACA0015 profile and a second with a NACA63415 profile. The turbulence is measured by a triple wired hotwire instrument in the experiment with a NACA0015 profile. Comparison of the aerodynamical models with data shows that the models capture the general characteristics of the measurements, but the data are hampered by background noise from the fan propellers in the wind tunnel. The measurements are in between the completely anisotropic turbulent model and the perfectly isotropic turbulent model. This indicates that the models capture the aerodynamics well. Thus the measurements suggest that the noise due to atmospheric turbulence can be described and modeled by the two models for lift distribution. It was not possible to test the acoustical model by the measurements

  7. Aerodynamic Simulation of the MARINTEK Braceless Semisubmersible Wave Tank Tests

    Science.gov (United States)

    Stewart, Gordon; Muskulus, Michael

    2016-09-01

    Model scale experiments of floating offshore wind turbines are important for both platform design for the industry as well as numerical model validation for the research community. An important consideration in the wave tank testing of offshore wind turbines are scaling effects, especially the tension between accurate scaling of both hydrodynamic and aerodynamic forces. The recent MARINTEK braceless semisubmersible wave tank experiment utilizes a novel aerodynamic force actuator to decouple the scaling of the aerodynamic forces. This actuator consists of an array of motors that pull on cables to provide aerodynamic forces that are calculated by a blade-element momentum code in real time as the experiment is conducted. This type of system has the advantage of supplying realistically scaled aerodynamic forces that include dynamic forces from platform motion, but does not provide the insights into the accuracy of the aerodynamic models that an actual model-scale rotor could provide. The modeling of this system presents an interesting challenge, as there are two ways to simulate the aerodynamics; either by using the turbulent wind fields as inputs to the aerodynamic model of the design code, or by surpassing the aerodynamic model and using the forces applied to the experimental turbine as direct inputs to the simulation. This paper investigates the best practices of modeling this type of novel aerodynamic actuator using a modified wind turbine simulation tool, and demonstrates that bypassing the dynamic aerodynamics solver of design codes can lead to erroneous results.

  8. The Torsional Vibration of Turbo Axis Induced by Unsteady Aerodynamic Force on Rotor blade

    Institute of Scientific and Technical Information of China (English)

    ChenZuoyi; WuXiaofeng

    1998-01-01

    An algorithm for computing the 3-D oscillating flow field of the balde passage under the torsional vibration of the rotor is applied to analyze the stability in turbomachines.The induced flow field responding to blade vibration is computed by Oscillating Fluid Mechanics Method and parametric Polynomial Method.After getting the solution of the unsteady flow field,the work done by the unsteay aerodynamic force acting on the blade can be obtained.The negative or positive work is the criterion of the aeroelastic stability.Numerical results indicate that there are instabilities of the torsional vibration in some frequency bands.

  9. Computation of the stability derivatives via CFD and the sensitivity equations

    Institute of Scientific and Technical Information of China (English)

    Guo-Dong Lei; Yu-Xin Ren

    2011-01-01

    The method to calculate the aerodynamic stability derivates of aircrafts by using the sensitivity equations is extended to flows with shock waves in this paper. Using the newly developed second-order ceil-centered finite volume scheme on the unstructured-grid, the unsteady Euler equations and sensitivity equations are solved simultaneously in a non-inertial frame of reference, so that the aerodynamic stability derivatives can be calculated for aircrafts with complex geometries. Based on the numerical results, behavior of the aerodynamic sensitivity parameters near the shock wave is discussed. Furthermore, the stability derivatives are analyzed for supersonic and hypersonic flows. The numerical results of the stability derivatives are found in good agreement with theoretical results for supersonic flows, and variations of the aerodynamic force and moment predicted by the stability derivatives are very close to those obtained by CFD simulation for both supersonic and hypersonic flows.

  10. Numerical Calculation of Effect of Elastic Deformation on Aerodynamic Characteristics of a Rocket

    Directory of Open Access Journals (Sweden)

    Laith K. Abbas

    2014-01-01

    Full Text Available The application and workflow of Computational Fluid Dynamics (CFD/Computational Structure Dynamics (CSD on solving the static aeroelastic problem of a slender rocket are introduced. To predict static aeroelastic behavior accurately, two-way coupling and inertia relief methods are used to calculate the static deformations and aerodynamic characteristics of the deformed rocket. The aerodynamic coefficients of rigid rocket are computed firstly and compared with the experimental data, which verified the accuracy of CFD output. The results of the analysis for elastic rocket in the nonspinning and spinning states are compared with the rigid ones. The results highlight that the rocket deformation aspects are decided by the normal force distribution along the rocket length. Rocket deformation becomes larger with increasing the flight angle of attack. Drag and lift force coefficients decrease and pitching moment coefficients increase due to rocket deformations, center of pressure location forwards, and stability of the rockets decreases. Accordingly, the flight trajectory may be affected by the change of these aerodynamic coefficients and stability.

  11. Aerosol printing of colloidal nanocrystals by aerodynamic focusing

    Science.gov (United States)

    Qi, Lejun

    Colloidal semiconductor nanocrystals, or quantum dots, have shown promise as the active material in electronic and optoelectronic applications, because of their high quantum yield, narrow spectral emission band, size-tunable bandgap, chemical stability, and easy processibility. Meanwhile, it is still challenging to print patterns of nanocrystal films with desired linewidth and thickness, which is a critical step in fabrication of nanocrystal-based devices. In this thesis, a direct-write method of colloidal semiconductor nanocrystals has been developed. Like other direct-write techniques, this aerosol based method simplifies printing process and reduces the manufacturing cost, as it avoids mask screening, lithography, and pre-patterning of the substrate. Moreover, the aerosol printing with aerodynamic lenses needs neither microscale nozzles nor sheath gases, and is able to incorporate into the vacuum systems currently used in microelectronic fabrication. This thesis research presents systematic efforts to develop an aerosol-based method to directly write patterns of semiconductor nanocrystals from colloidal dispersions by aerodynamic focusing. First, the synthesized colloidal nanocrystals in hexane were nebulized into compact and spherical agglomerates suspending in the carrier gas. The details about the impact dynamics of individual aerosolized nanocrystal agglomerates were investigated. As building blocks of printed nanocrystal films, the agglomerate exhibited cohesive and granular behaviors during impact deformation on the substrate. The strength of cohesion between nanocrystals in the agglomerates could be adjusted by tuning the number concentration of colloidal nanocrystal dispersion. Second, ultrathin films of nanocrystals were obtained by printing monodisperse nanocrystal agglomerates. As the result of the granular property of nanocrystal agglomerates, it was found that the thickness of deposited agglomerates strongly depended on the size of agglomerates. A

  12. Investigation of Aerodynamic Interference of Double Deck Bridges

    Energy Technology Data Exchange (ETDEWEB)

    Sitek, M. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division. Transportation Research and Analysis Computing Center (TRACC); Bojanowski, C. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division. Transportation Research and Analysis Computing Center (TRACC); Lottes, S. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division. Transportation Research and Analysis Computing Center (TRACC)

    2016-05-01

    Construction of a twin bridge can be a cost effective and minimally disruptive way to increase capacity when an existing bridge is not near the end of its service life. With ever growing vehicular traffic, when demand approaches the capacity of many existing roads and bridges. Remodeling a structure with an insufficient number of lanes can be a good solution in case of smaller and less busy bridges. Closing down or reducing traffic on crossings of greater importance for the construction period, however, can result in major delays and revenue loss for commerce and transportation as well as increasing the traffic load on alternate route bridges. Multiple-deck bridges may be the answer to this issue. A parallel deck can be built next to the existing one, without reducing the flow. Additionally, a new bridge can be designed as a twin or multi-deck structure. Several such structures have been built throughout the United States, among them: - The New NY Bridge Project - the Tappan Zee Hudson River Crossing, - SR-182 Columbia River Bridge, - The Thaddeus Kosciusko Bridge (I-87), - The Allegheny River Bridge, Pennsylvania, which carries I76, - Fred Hartman Bridge, TX, see Figure 1.2. With a growing number of double deck bridges, additional, more detailed, studies on the interaction of such bridge pairs in windy conditions appears appropriate. Aerodynamic interference effects should be examined to assure the aerodynamic stability of both bridges. There are many studies on aerodynamic response of single deck bridges, but the literature on double-deck structures is not extensive. The experimental results from wind tunnels are still limited in number, as a parametric study is required, they can be very time consuming. Literature review shows that some investigation of the effects of gap-width and angle of wind incidence has been done. Most of the CFD computational studies that have been done were limited to 2D simulations. Therefore, it is desirable to investigate twin decks

  13. Aerodynamics of Rotor Blades for Quadrotors

    CERN Document Server

    Bangura, Moses; Naldi, Roberto; Mahony, Robert

    2016-01-01

    In this report, we present the theory on aerodynamics of quadrotors using the well established momentum and blade element theories. From a robotics perspective, the theoretical development of the models for thrust and horizontal forces and torque (therefore power) are carried out in the body fixed frame of the quadrotor. Using momentum theory, we propose and model the existence of a horizontal force along with its associated power. Given the limitations associated with momentum theory and the inadequacy of the theory to account for the different powers represented in a proposed bond graph lead to the use of blade element theory. Using this theory, models are then developed for the different quadrotor rotor geometries and aerodynamic properties including the optimum hovering rotor used on the majority of quadrotors. Though this rotor is proven to be the most optimum rotor, we show that geometric variations are necessary for manufacturing of the blades. The geometric variations are also dictated by a desired th...

  14. ANALYTICAL METHODS FOR CALCULATING FAN AERODYNAMICS

    Directory of Open Access Journals (Sweden)

    Jan Dostal

    2015-12-01

    Full Text Available This paper presents results obtained between 2010 and 2014 in the field of fan aerodynamics at the Department of Composite Technology at the VZLÚ aerospace research and experimental institute in Prague – Letnany. The need for rapid and accurate methods for the preliminary design of blade machinery led to the creation of a mathematical model based on the basic laws of turbomachine aerodynamics. The mathematical model, the derivation of which is briefly described below, has been encoded in a computer programme, which enables the theoretical characteristics of a fan of the designed geometry to be determined rapidly. The validity of the mathematical model is assessed continuously by measuring model fans in the measuring unit, which was developed and manufactured specifically for this purpose. The paper also presents a comparison between measured characteristics and characteristics determined by the mathematical model as the basis for a discussion on possible causes of measured deviations and calculation deviations.

  15. Aerodynamic Design of a Tailless Aeroplan

    Directory of Open Access Journals (Sweden)

    J. Friedl

    2001-01-01

    Full Text Available The paper presents an aerodynamic analysis of a one-seat ultralight (UL tailless aeroplane named L2k, with a very complicated layout. In the first part, an autostable airfoil with a low moment coefficient was chosen as a base for this problem. This airfoil was refined and modified to satisfy the design requirements. The computed aerodynamic characteristics of the airfoils for different Reynolds numbers (Re were compared with available experimental data. XFOIL code was used to perform the computations. In the second part, a computation of wing characteristics was carried out. All calculated cases were chosen as points on the manoeuvring and gust envelope. The vortex lattice method was used with consideration of fuselage and winglets for very complicated wing geometry. The PMW computer program developed at IAE was used to perform the computations. The computed results were subsequently used for structural and strength analysis and design.

  16. Aerodynamic control with passively pitching wings

    Science.gov (United States)

    Gravish, Nick; Wood, Robert

    Flapping wings may pitch passively under aerodynamic and inertial loads. Such passive pitching is observed in flapping wing insect and robot flight. The effect of passive wing pitch on the control dynamics of flapping wing flight are unexplored. Here we demonstrate in simulation and experiment the critical role wing pitching plays in yaw control of a flapping wing robot. We study yaw torque generation by a flapping wing allowed to passively rotate in the pitch axis through a rotational spring. Yaw torque is generated through alternating fast and slow upstroke and and downstroke. Yaw torque sensitively depends on both the rotational spring force law and spring stiffness, and at a critical spring stiffness a bifurcation in the yaw torque control relationship occurs. Simulation and experiment reveal the dynamics of this bifurcation and demonstrate that anomalous yaw torque from passively pitching wings is the result of aerodynamic and inertial coupling between the pitching and stroke-plane dynamics.

  17. CFD research, parallel computation and aerodynamic optimization

    Science.gov (United States)

    Ryan, James S.

    1995-01-01

    Over five years of research in Computational Fluid Dynamics and its applications are covered in this report. Using CFD as an established tool, aerodynamic optimization on parallel architectures is explored. The objective of this work is to provide better tools to vehicle designers. Submarine design requires accurate force and moment calculations in flow with thick boundary layers and large separated vortices. Low noise production is critical, so flow into the propulsor region must be predicted accurately. The High Speed Civil Transport (HSCT) has been the subject of recent work. This vehicle is to be a passenger vehicle with the capability of cutting overseas flight times by more than half. A successful design must surpass the performance of comparable planes. Fuel economy, other operational costs, environmental impact, and range must all be improved substantially. For all these reasons, improved design tools are required, and these tools must eventually integrate optimization, external aerodynamics, propulsion, structures, heat transfer and other disciplines.

  18. Vortical sources of aerodynamic force and moment

    Science.gov (United States)

    Wu, J. Z.; Wu, J. M.

    1989-01-01

    It is shown that the aerodynamic force and moment can be expressed in terms of vorticity distribution (and entropy variation for compressible flow) on near wake plane, or in terms of boundary vorticity flux on the body surface. Thus the vortical sources of lift and drag are clearly identified, which is the real physical basis of optimal aerodynamic design. Moreover, these sources are highly compact, hence allowing one to concentrate on key local regions of the configuration, which have dominating effect to the lift and drag. A detail knowledge of the vortical low requires measuring or calculating the vorticity and dilatation field, which is however still a challenging task. Nevertheless, this type of formulation has some unique advantages; and how to set up a well-posed problem, in particular how to establish vorticity-dilatation boundary conditions, is addressed.

  19. Particle Methods in Bluff Body Aerodynamics

    DEFF Research Database (Denmark)

    Rasmussen, Johannes Tophøj

    Fluid-structure interaction is studied numerically in academics and the industry. Shear computational power alone is insufficient to accurately resolve the complex dynamics of high Reynolds number fluid flow. Therefore the development of more efficient and applicable computational algorithms...... is important. This dissertation focuses on the use of vortex particle methods and computational efficiency. The work is divided into three parts. A novel method for the simulation of the aerodynamic admittance in bluff body aerodynamics is presented. The method involves a model for describing oncoming...... turbulence in two-dimensional discrete vortex method simulations by seeding the upstream flow with vortex particles. The turbulence is generated prior to the simulations and is based on analytic spectral densities of the atmospheric turbulence and a coherence function defining the spatial correlation...

  20. Mimicking the humpback whale: An aerodynamic perspective

    Science.gov (United States)

    Aftab, S. M. A.; Razak, N. A.; Mohd Rafie, A. S.; Ahmad, K. A.

    2016-07-01

    This comprehensive review aims to provide a critical overview of the work on tubercles in the past decade. The humpback whale is of interest to aerodynamic/hydrodynamic researchers, as it performs manoeuvres that baffle the imagination. Researchers have attributed these capabilities to the presence of lumps, known as tubercles, on the leading edge of the flipper. Tubercles generate a unique flow control mechanism, offering the humpback exceptional manoeuverability. Experimental and numerical studies have shown that the flow pattern over the tubercle wing is quite different from conventional wings. Research on the Tubercle Leading Edge (TLE) concept has helped to clarify aerodynamic issues such as flow separation, tonal noise and dynamic stall. TLE shows increased lift by delaying and restricting spanwise separation. A summary of studies on different airfoils and reported improvement in performance is outlined. The major contributions and limitations of previous work are also reported.

  1. Integrated structural-aerodynamic design optimization

    Science.gov (United States)

    Haftka, R. T.; Kao, P. J.; Grossman, B.; Polen, D.; Sobieszczanski-Sobieski, J.

    1988-01-01

    This paper focuses on the processes of simultaneous aerodynamic and structural wing design as a prototype for design integration, with emphasis on the major difficulty associated with multidisciplinary design optimization processes, their enormous computational costs. Methods are presented for reducing this computational burden through the development of efficient methods for cross-sensitivity calculations and the implementation of approximate optimization procedures. Utilizing a modular sensitivity analysis approach, it is shown that the sensitivities can be computed without the expensive calculation of the derivatives of the aerodynamic influence coefficient matrix, and the derivatives of the structural flexibility matrix. The same process is used to efficiently evaluate the sensitivities of the wing divergence constraint, which should be particularly useful, not only in problems of complete integrated aircraft design, but also in aeroelastic tailoring applications.

  2. Nash equilibrium and multi criterion aerodynamic optimization

    Science.gov (United States)

    Tang, Zhili; Zhang, Lianhe

    2016-06-01

    Game theory and its particular Nash Equilibrium (NE) are gaining importance in solving Multi Criterion Optimization (MCO) in engineering problems over the past decade. The solution of a MCO problem can be viewed as a NE under the concept of competitive games. This paper surveyed/proposed four efficient algorithms for calculating a NE of a MCO problem. Existence and equivalence of the solution are analyzed and proved in the paper based on fixed point theorem. Specific virtual symmetric Nash game is also presented to set up an optimization strategy for single objective optimization problems. Two numerical examples are presented to verify proposed algorithms. One is mathematical functions' optimization to illustrate detailed numerical procedures of algorithms, the other is aerodynamic drag reduction of civil transport wing fuselage configuration by using virtual game. The successful application validates efficiency of algorithms in solving complex aerodynamic optimization problem.

  3. Aerodynamic design of the National Rotor Testbed.

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, Christopher Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-10-01

    A new wind turbine blade has been designed for the National Rotor Testbed (NRT) project and for future experiments at the Scaled Wind Farm Technology (SWiFT) facility with a specific focus on scaled wakes. This report shows the aerodynamic design of new blades that can produce a wake that has similitude to utility scale blades despite the difference in size and location in the atmospheric boundary layer. Dimensionless quantities circulation, induction, thrust coefficient, and tip-speed-ratio were kept equal between rotor scales in region 2 of operation. The new NRT design matched the aerodynamic quantities of the most common wind turbine in the United States, the GE 1.5sle turbine with 37c model blades. The NRT blade design is presented along with its performance subject to the winds at SWiFT. The design requirements determined by the SWiFT experimental test campaign are shown to be met.

  4. Unsteady Aerodynamic Flow Control of Moving Platforms

    Science.gov (United States)

    2014-05-29

    This error will arguably be diminished further with the future tuning of the PID controller that implements the motor commands. III.3.3 Aerodynamic...model is still aligned with the flow or ‘fine tune ’ the SMA power if it needs a minor realignment. III.1.2 Centered Static Model Prior to examining...8217 fluidic control. In addition, a PID controller is developed to effect ’closed loop’ fluidic control with optimally timed synthetic jet operation

  5. Conformable M3 Microsystems for Aerodynamic Control

    Science.gov (United States)

    2007-11-02

    we have fabricated sensors, actuators, and electronics all on the same chip. Control: • A CMOS control circuit has been designed and sent to MOSIS ...macro aerodynamic devices. (3) After the chip from MOSIS is fabricated, it will be tested to confirm that it works as designed. (4) The process and...identify the separation point from the outputs of shear stress sensors and drive the corresponding actuators. The layout has been sent to MOSIS for

  6. Special Course on Aerodynamic Characteristics of Controls

    Science.gov (United States)

    1983-07-01

    Munich, 1973. £913 PINES, S. Aerodynamic flutter derivatives for an oscillating finite DUGUNDJI , J. thin wing in supersonic flow. JAS 23, p. 693, 1955... topology asso- ciated with forebody blowing about a slender cone model. 6-3 A.2 BACKGROUND A. 2.1 Forebody Flowfields at High Angles of Attack It is...spin. since the driving side force is produced by the vortex in the closest proximity to the surface.) The topology of the asymmetric vortex

  7. Compressor performance aerodynamics for the user

    CERN Document Server

    Gresh, Theodore

    2001-01-01

    Compressor Performance is a reference book and CD-ROM for compressor design engineers and compressor maintenance engineers, as well as engineering students. The book covers the full spectrum of information needed for an individual to select, operate, test and maintain axial or centrifugal compressors. It includes basic aerodynamic theory to provide the user with the ""how's"" and ""why's"" of compressor design. Maintenance engineers will especially appreciate the troubleshooting guidelines offered. Includes many example problems and reference data such as gas propert

  8. Aerodynamic sound of flow in corrugated tubes

    OpenAIRE

    2009-01-01

    Aerodynamic sound emitted by flow through a finite length duct with corrugated inner surface is experimentally investigated. As the mechanism of sound generating oscillation, so far popular 'cavity-tone' mechanism was definitely denied. The principal reason is: With corrugation of helical geometry, no characteristic sound came on, while a pair of a nozzle edge and a leading edge both of which are helical, with constant distance, made essentially as loud sound as a pair of normal edges. Other ...

  9. Aerodynamic Benchmarking of the Deepwind Design

    DEFF Research Database (Denmark)

    Bedona, Gabriele; Schmidt Paulsen, Uwe; Aagaard Madsen, Helge;

    2015-01-01

    The aerodynamic benchmarking for the DeepWind rotor is conducted comparing different rotor geometries and solutions and keeping the comparison as fair as possible. The objective for the benchmarking is to find the most suitable configuration in order to maximize the power production and minimize...... NACA airfoil family. (C) 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license...

  10. Vortices and Vortical Structures in Internal Aerodynamics

    Institute of Scientific and Technical Information of China (English)

    RudolfDvorak

    1997-01-01

    The paper aims at summarizing the author's recent phenomenological study of the origin,development and identification of vortical structures in internal aerodynamics.A connection between evolution of these structures and flow separation in closed curved channels is also discussed.It has been shown that in real fluids the individual vortex cores very sonn lose their identity and merge into a new dissipative structure,the properties of which still have to be defined.

  11. The Theoretical Research for the Rotor/Fuselage Unsteady Aerodynamic Interaction Problem

    Directory of Open Access Journals (Sweden)

    Liu Dawei

    2016-07-01

    Full Text Available Based on coupled unsteady panel/free-wake method, a universal analysis model was established, which provides a good prediction for the rotor/fuselage unsteady aerodynamic interaction. Considering the deficiencies of the traditional time-marching rotor free-wake algorithms, notably on stability and efficiency, the CB3D algorithm with 3rd-order accuracy is proposed. For solving the problem that part of the wake vortices may penetrate the fuselage, a “material line” rectification method with 3rd-order accuracy is proposed. An analysis for the model accuracy was then conducted to validate the accuracy of the new model, and a comparison against the available experimental data is performed. The simulated results show a good agreement with these experimental data. With the new model, several simulations are conducted for the typical rotor/fuselage aerodynamic interaction, and the results are analyzed.

  12. FY 2004 Annual Report: DOE Project on Heavy Vehicle Aerodynamic Drag

    Energy Technology Data Exchange (ETDEWEB)

    McCallen, R C; Salari, K; Ortega, J; Castellucci, P; Eastwood, C; Whittaker, K; DeChant, L J; Roy, C J; Payne, J L; Hassan, B; Pointer, W D; Browand, F; Hammache, M; Hsu, T; Ross, J; Satran, D; Heineck, J T; Walker, S; Yaste, D; Englar, R; Leonard, A; Rubel, M; Chatelain, P

    2004-11-18

    The objective of this report is: (1) Provide guidance to industry in the reduction of aerodynamic drag of heavy truck vehicles; and (2) Establish a database of experimental, computational, and conceptual design information, and demonstrate potential of new drag-reduction devices. The approaches used were: (1) Develop and demonstrate the ability to simulate and analyze aerodynamic flow around heavy truck vehicles using existing and advanced computational fluid dynamics (CFD) tools; (2) Through an extensive experimental effort, generate an experimental data base for code validation; (3) Using experimental data base, validate computations; (4) Provide industry with design guidance and insight into flow phenomena from experiments and computations; and (5) Investigate aero devices (e.g., base flaps, tractor-trailer gap stabilizer, underbody skirts and wedges, blowing and acoustic devices), provide industry with conceptual designs of drag reducing devices, and demonstrate the full-scale fuel economy potential of these devices.

  13. MATLAB Stability and Control Toolbox Trim and Static Stability Module

    Science.gov (United States)

    Kenny, Sean P.; Crespo, Luis

    2012-01-01

    MATLAB Stability and Control Toolbox (MASCOT) utilizes geometric, aerodynamic, and inertial inputs to calculate air vehicle stability in a variety of critical flight conditions. The code is based on fundamental, non-linear equations of motion and is able to translate results into a qualitative, graphical scale useful to the non-expert. MASCOT was created to provide the conceptual aircraft designer accurate predictions of air vehicle stability and control characteristics. The code takes as input mass property data in the form of an inertia tensor, aerodynamic loading data, and propulsion (i.e. thrust) loading data. Using fundamental nonlinear equations of motion, MASCOT then calculates vehicle trim and static stability data for the desired flight condition(s). Available flight conditions include six horizontal and six landing rotation conditions with varying options for engine out, crosswind, and sideslip, plus three take-off rotation conditions. Results are displayed through a unique graphical interface developed to provide the non-stability and control expert conceptual design engineer a qualitative scale indicating whether the vehicle has acceptable, marginal, or unacceptable static stability characteristics. If desired, the user can also examine the detailed, quantitative results.

  14. Aerodynamics of a rigid curved kite wing

    CERN Document Server

    Maneia, Gianmauro; Tordella, Daniela; Iovieno, Michele

    2013-01-01

    A preliminary numerical study on the aerodynamics of a kite wing for high altitude wind power generators is proposed. Tethered kites are a key element of an innovative wind energy technology, which aims to capture energy from the wind at higher altitudes than conventional wind towers. We present the results obtained from three-dimensional finite volume numerical simulations of the steady air flow past a three-dimensional curved rectangular kite wing (aspect ratio equal to 3.2, Reynolds number equal to 3x10^6). Two angles of incidence -- a standard incidence for the flight of a tethered airfoil (6{\\deg}) and an incidence close to the stall (18{\\deg}) -- were considered. The simulations were performed by solving the Reynolds Averaged Navier-Stokes flow model using the industrial STAR-CCM+ code. The overall aerodynamic characteristics of the kite wing were determined and compared to the aerodynamic characteristics of the flat rectangular non twisted wing with an identical aspect ratio and section (Clark Y profil...

  15. 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.

  16. Noise aspects at aerodynamic blade optimisation projects

    Energy Technology Data Exchange (ETDEWEB)

    Schepers, J.G. [Netherlands Energy Research Foundation, Petten (Netherlands)

    1997-12-31

    This paper shows an example of an aerodynamic blade optimisation, using the program PVOPT. PVOPT calculates the optimal wind turbine blade geometry such that the maximum energy yield is obtained. Using the aerodynamic optimal blade design as a basis, the possibilities of noise reduction are investigated. The aerodynamic optimised geometry from PVOPT is the `real` optimum (up to the latest decimal). The most important conclusion from this study is, that it is worthwhile to investigate the behaviour of the objective function (in the present case the energy yield) around the optimum: If the optimum is flat, there is a possibility to apply modifications to the optimum configuration with only a limited loss in energy yield. It is obvious that the modified configurations emits a different (and possibly lower) noise level. In the BLADOPT program (the successor of PVOPT) it will be possible to quantify the noise level and hence to assess the reduced noise emission more thoroughly. At present the most promising approaches for noise reduction are believed to be a reduction of the rotor speed (if at all possible), and a reduction of the tip angle by means of low lift profiles, or decreased twist at the outboard stations. These modifications were possible without a significant loss in energy yield. (LN)

  17. Performance and Stability Analysis of a Shrouded-Fan UAV

    CERN Document Server

    de Divitiis, Nicola

    2009-01-01

    This paper deals with the estimation of the performance and stability for a shrouded-fan unmanned rotorcraft whose mission profile also prescribes the flight in ground effect. The not so simple estimation of the aerodynamic coefficients and of the thrust in the various situations makes the performance calculation and the stability analysis difficult tasks. This is due to the strong interaction between the fan flow and shroud that causes quite different flow structures about the airframe depending on flight conditions. A further difficulty is related to the ground effect which produces substantial modifications in the rotor thrust and aerodynamic coefficients. To evaluate performance and stability, two models have been developed. One determines the aerodynamic coefficients of the shroud, whereas the other one calculates thrust and moment of the rotors system. Both models take into account the mutual interference between fan flow and fuselage and ground effect. Performance and stability are then discussed with ...

  18. Feasibility study of a novel method for real-time aerodynamic coefficient estimation

    Science.gov (United States)

    Gurbacki, Phillip M.

    In this work, a feasibility study of a novel technique for the real-time identification of uncertain nonlinear aircraft aerodynamic coefficients has been conducted. The major objective of this paper is to investigate the feasibility of a system for parameter identification in a real-time flight environment. This system should be able to calculate aerodynamic coefficients and derivative information using typical pilot inputs while ensuring robust, stable, and rapid convergence. The parameter estimator investigated is based upon the nonlinear sliding mode control schema; one of the main advantages of the sliding mode estimator is the ability to guarantee a stable and robust convergence. Stable convergence is ensured by choosing a sliding surface and function that satisfies the Lyapunov stability criteria. After a proper sliding surface has been chosen, the nonlinear equations of motion for an F-16 aircraft are substituted into the sliding surface yielding an estimator capable of identifying a single aircraft parameter. Multiple sliding surfaces are then developed for each of the different flight parameters that will be identified. Sliding surfaces and parameter estimators have been developed and simulated for the pitching moment, lift force, and drag force coefficients of the F-16 aircraft. Comparing the estimated coefficients with the reference coefficients shows rapid and stable convergence for a variety of pilot inputs. Starting with simple doublet and sin wave commands, and followed by more complicated continuous pilot inputs, estimated aerodynamic coefficients have been shown to match the actual coefficients with a high degree of accuracy. This estimator is also shown to be superior to model reference or adaptive estimators, it is able to handle positive and negative estimated parameters and control inputs along with guaranteeing Lyapunov stability during convergence. Accurately estimating these aerodynamic parameters in real-time during a flight is essential

  19. AERODYNAMIC BEHAVIOR AIRCRAFT CAUSED BY RESIDUAL STRAIN WINGS

    Directory of Open Access Journals (Sweden)

    Sergiy Ishchenko

    2011-03-01

    Full Text Available Abstract. The influence of residual strain on the airframe aerodynamic characteristics of aircraft wasconsidered. The possibility of estimation of changes in deformation of airframe using data of leveling wasshown. The method of estimating the change of aerodynamic characteristics caused by the influence ofresidual strain airframe was proposed. Technique can be used in the operation and overhaul of aircraft withlarge operating time.Keywords: aerodynamic characteristics, residual strain construction asymmetric moments, thedistribution of circulation, the scheme of leveling, trigonometric series.

  20. AERODYNAMIC BEHAVIOR AIRCRAFT CAUSED BY RESIDUAL STRAIN WINGS

    OpenAIRE

    Ishchenko, Sergiy; Tofil, Arkadiush

    2011-01-01

    Abstract. The influence of residual strain on the airframe aerodynamic characteristics of aircraft wasconsidered. The possibility of estimation of changes in deformation of airframe using data of leveling wasshown. The method of estimating the change of aerodynamic characteristics caused by the influence ofresidual strain airframe was proposed. Technique can be used in the operation and overhaul of aircraft withlarge operating time.Keywords: aerodynamic characteristics, residual strain constr...

  1. The aerodynamic and structural study of flapping wing vehicles

    OpenAIRE

    2013-01-01

    This thesis reports on the aerodynamic and structural study carried out on flapping wings and flapping vehicles. Theoretical and experimental investigation of aerodynamic forces acting on flapping wings in simple harmonic oscillations is undertaken in order to help conduct and optimize the aerodynamic and structural design of flapping wing vehicles. The research is focused on the large scale ornithopter design of similar size and configuration to a hang glider. By means of Theodorsen’s th...

  2. System Identification of a Vortex Lattice Aerodynamic Model

    Science.gov (United States)

    Juang, Jer-Nan; Kholodar, Denis; Dowell, Earl H.

    2001-01-01

    The state-space presentation of an aerodynamic vortex model is considered from a classical and system identification perspective. Using an aerodynamic vortex model as a numerical simulator of a wing tunnel experiment, both full state and limited state data or measurements are considered. Two possible approaches for system identification are presented and modal controllability and observability are also considered. The theory then is applied to the system identification of a flow over an aerodynamic delta wing and typical results are presented.

  3. A climatology of formation conditions for aerodynamic contrails

    Directory of Open Access Journals (Sweden)

    K. Gierens

    2013-06-01

    Full Text Available Aerodynamic contrails are defined in this paper as line shaped ice clouds caused by aerodynamically triggered cooling over the wings of an aircraft in cruise which become visible immediately at the trailing edge of the wing or close to it. Effects at low altitudes like condensation to liquid droplets and their potential heterogeneous freezing are excluded from our definition. We study atmospheric conditions that allow formation of aerodynamic contrails. These conditions are stated and then applied to atmospheric data, first to a special case where an aerodynamic contrail was actually observed and then to a full year of global reanalysis data. We show where, when (seasonal variation, and how frequently (probability aerodynamic contrails can form, and how this relates to actual patterns of air traffic. We study the formation of persistent aerodynamic contrails as well. Finally we check whether aerodynamic and exhaust contrails can coexist in the atmosphere. We show that visible aerodynamic contrails are possible only in an altitude range between roughly 540 and 250 hPa, and that the ambient temperature is the most important parameter, not the relative humidity. Finally we give an argument for our believe that currently aerodynamic contrails have a much smaller climate effect than exhaust contrails, which may however change in future with more air traffic in the tropics.

  4. Aerodynamic instability of a cylinder with thin ice accretion

    DEFF Research Database (Denmark)

    Gjelstrup, Henrik; Georgakis, Christos

    2009-01-01

    prototyping. Next, a series of static wind tunnel tests were undertaken to determine the aerodynamic force coefficients of the rapidly prototyped hanger sectional model. Finally the aerodynamic force coefficients (drag, lift and moment), found from the static wind tunnel tests, were used to determine...... the potential for aerodynamic instability of the hanger through application of the quasi-steady theory developed by Gjelstrup et al. [9-10]. The application of the theoretical model yield regions of expected aerodynamic instability in which the observed vibrations of the Great Belt East Bridge hangers lie....

  5. Aerodynamic Modeling with Heterogeneous Data Assimilation and Uncertainty Quantification Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Clear Science Corp. proposes to develop an aerodynamic modeling tool that assimilates data from different sources and facilitates uncertainty quantification. The...

  6. Experimental Aerodynamic Facilities of the Aerodynamics Research and Concepts Assistance Section

    Science.gov (United States)

    1983-02-01

    liquid droplets and other aerodynamic bodies which are sensitive to support interference and motion cross coupling effects. Rapid and accurate...AESD Wright-Patterson AFB, OH 45433 HQ AFSC/SDZ ATTN: CPT D. Rledlger Andrews AFB, MD 20334 HQ, AFSC/SDNE Andrews AFB, MD 20334 HQ, AFSC/ SGB

  7. A climatology of formation conditions for aerodynamic contrails

    Directory of Open Access Journals (Sweden)

    K. Gierens

    2013-11-01

    Full Text Available Aircraft at cruise levels can cause two kinds of contrails, the well known exhaust contrails and the less well-known aerodynamic contrails. While the possible climate impact of exhaust contrails has been studied for many years, research on aerodynamic contrails began only a few years ago and nothing is known about a possible contribution of these ice clouds to climate impact. In order to make progress in this respect, we first need a climatology of their formation conditions and this is given in the present paper. Aerodynamic contrails are defined here as line shaped ice clouds caused by aerodynamically triggered cooling over the wings of an aircraft in cruise which become visible immediately at the trailing edge of the wing or close to it. Effects at low altitudes like condensation to liquid droplets and their potential heterogeneous freezing are excluded from our definition. We study atmospheric conditions that allow formation of aerodynamic contrails. These conditions are stated and then applied to atmospheric data: first to a special case where an aerodynamic contrail was actually observed and then to a full year of global reanalysis data. We show where, when (seasonal variation, and how frequently (probability aerodynamic contrails can form, and how this relates to actual patterns of air traffic. We study the formation of persistent aerodynamic contrails as well. Furthermore, we check whether aerodynamic and exhaust contrails can coexist in the atmosphere. We show that visible aerodynamic contrails are possible only in an altitude range between roughly 540 and 250 hPa, and that the ambient temperature is the most important parameter, not the relative humidity. Finally, we argue that currently aerodynamic contrails have a much smaller climate effect than exhaust contrails, which may however change in future with more air traffic in the tropics.

  8. Aerodynamics of High-Speed Trains

    Science.gov (United States)

    Schetz, Joseph A.

    This review highlights the differences between the aerodynamics of high-speed trains and other types of transportation vehicles. The emphasis is on modern, high-speed trains, including magnetic levitation (Maglev) trains. Some of the key differences are derived from the fact that trains operate near the ground or a track, have much greater length-to-diameter ratios than other vehicles, pass close to each other and to trackside structures, are more subject to crosswinds, and operate in tunnels with entry and exit events. The coverage includes experimental techniques and results and analytical and numerical methods, concentrating on the most recent information available.

  9. Aerodynamic Modelling and Optimization of Axial Fans

    DEFF Research Database (Denmark)

    Sørensen, Dan Nørtoft

    A numerically efficient mathematical model for the aerodynamics oflow speed axial fans of the arbitrary vortex flow type has been developed.The model is based on a blade-element principle, whereby therotor is divided into a number of annular streamtubes.For each of these streamtubes relations...... for velocity, pressure andradial position are derived from the conservationlaws for mass, tangential momentum and energy.The resulting system of equations is non-linear and, dueto mass conservation and pressure equilibrium far downstream of the rotor,strongly coupled.The equations are solved using the Newton...

  10. Aerodynamic Optimization of a Winglet Design

    Directory of Open Access Journals (Sweden)

    Yahiaoui T.

    2013-04-01

    Full Text Available In the present study, an experimental study is presented for a flow around an isolated wing equipped by a winglet and profiled with Naca 0012. Several cases of winglets were tested according to the angle ß: 0°, 55°, 65°and 75°. For all these cases at a velocity of 20, 30 and 40 meters per second, wind tunnel tests are performed and compared for different angles of incidence. It is observed that the aerodynamic performance of the winglet with β= 55° differ favorably for positive angle of incidence compared for other cases.

  11. Fluidization technologies: Aerodynamic principles and process engineering.

    Science.gov (United States)

    Dixit, Rahul; Puthli, Shivanand

    2009-11-01

    The concept of fluidization has been adapted to different unit processes of pharmaceutical product development. Till date a lot of improvements have been made in the engineering design to achieve superior process performance. This review is focused on the fundamental principles of aerodynamics and hydrodynamics associated with the fluidization technologies. Fluid-bed coating, fluidized bed granulation, rotor processing, hot melt granulation, electrostatic coating, supercritical fluid based fluidized bed technology are highlighted. Developments in the design of processing equipments have been explicitly elucidated. This article also discusses processing problems from the operator's perspective along with latest developments in the application of these principles.

  12. Aerodynamic Size Classification of Glass Fibers.

    Science.gov (United States)

    Laosmaa, Pekka J. J.

    The objective of this research was to examine a technique by which fibers may be aerodynamically classified by diameter and/or length. In this study a system for fiber preparation and generation as well as an in situ fiber classifier were constructed and evaluated. A recently developed technique, the size classification of particles by opposing jets, was modified. The research set-up consisted of (1) a vibrating bed fiber generator, which also functioned as a preselector, (2) an opposing-jet classifier equipped with electrodes and high voltage power supplies to create fiber-aligning electric fields inside the classifier and (3) an optoelectric fiber sensor to measure the concentration and length of fibers. The classified fibers were also collected on filters for the counting and dimensional analysis of the fibers. Some flow instability problems were found during the initial tests of the classifier. They were attributed to random flow fluctuations in the nozzles caused by very small perturbations upstream of the nozzles. Within a critical range of flow Reynolds numbers the flow becomes "intermittent", i.e. it alternates in time between being laminar and turbulent in a random sequence. Small disturbances upstream of the point of consideration can "trigger" the changes from laminar to turbulent flow and the initial disturbance may be "amplified", sending a turbulent flash through the flow system. The classifier performed well with test aerosols after the nozzle flowrate had been decreased to correspond to a lower and less critical Reynolds number and after some modifications had been made to smooth the flow inside the classifier inlet chambers. The cut-off of test aerosols was sharp, but the loss of particles greater than 2.5 (mu)m in aerodynamic diameter was unsatisfactorily high. The classifier was able to classify fibers by aerodynamic diameter, but not as predicted through calculations. The results were difficult to interpret because of the high loss of fibers

  13. Variable volume combustor with aerodynamic support struts

    Energy Technology Data Exchange (ETDEWEB)

    Ostebee, Heath Michael; Johnson, Thomas Edward; Stewart, Jason Thurman; Keener, Christopher Paul

    2017-03-07

    The present application provides a combustor for use with a gas turbine engine. The combustor may include a number of micro-mixer fuel nozzles and a fuel injection system for providing a flow of fuel to the micro-mixer fuel nozzles. The fuel injection system may include a number of support struts supporting the fuel nozzles and providing the flow of fuel therethrough. The support struts may include an aerodynamic contoured shape so as to distribute evenly a flow of air to the micro-mixer fuel nozzles.

  14. Aerodynamically forced vibration analysis of turbomachines

    Science.gov (United States)

    Elchuri, V.; Pamidi, P. R.

    1987-01-01

    An account is given of theoretical considerations for the determination of turbomachine response under aerodynamic excitation, as in the cases of advanced turboprop rotors with highly swept blades and axial flow compressors. Dynamic response is characterized in terms of the normal modal coordinates of tuned rotating cyclic structures for both rigid and flexible hubs/disks. Implementation of the scheme is in NASTRAN; coriolis and centripetal accelerations are included, together with differential stiffness effects. Analytically predicted vibratory stresses for the blades of two different advanced turboprops are compared to those determined by wind tunnel tests conducted by NASA-Lewis.

  15. Aerodynamic noise emission from turbulent shear layers.

    Science.gov (United States)

    Pao, S. P.

    1973-01-01

    The Phillips (1960) convected wave equation is employed in this paper to study aerodynamic noise emission processes in subsonic and supersonic shear layers. The wave equation in three spatial dimensions is first reduced to an ordinary differential equation by Fourier transformation and then solved via the WKBJ method. Three typical solutions are required for discussions in this paper. The current results are different from the classical conclusions. The effects of refraction, convection, Mach-number dependence and temperature dependence of turbulent noise emission are analyzed in the light of solutions to the Phillips equation.

  16. Numerical investigation on the aerodynamic characteristics of high-speed train under turbulent crosswind

    Institute of Scientific and Technical Information of China (English)

    Mulugeta Biadgo Asress; Jelena Svorcan

    2014-01-01

    Increasing velocity combined with decreasing mass of modern high-speed trains poses a question about the influence of strong crosswinds on its aerodynamics. Strong crosswinds may affect the running stability of high-speed trains via the amplified aerodynamic forces and moments. In this study, a simulation of turbulent crosswind flows over the leading and end cars of ICE-2 high-speed train was performed at different yaw angles in static and moving ground case scenarios. Since the train aerodynamic problems are closely associated with the flows occurring around train, the flow around the train was considered as incompressible and was obtained by solving the incom-pressible form of the unsteady Reynolds-averaged Navier–Stokes (RANS) equations combined with the realizable k-epsilon turbulence model. Important aerodynamic coef-ficients such as the side force and rolling moment coeffi-cients were calculated for yaw angles ranging from-30? to 60? and compared with the results obtained from wind tunnel test. The dependence of the flow structure on yaw angle was also presented. The nature of the flow field and its structure depicted by contours of velocity magnitude and streamline patterns along the train’s cross-section were presented for different yaw angles. In addition, the pressure coefficient around the circumference of the train at dif-ferent locations along its length was computed for yaw angles of 30? and 60?. The computed aerodynamic coef-ficient outcomes using the realizable k-epsilon turbulence model were in good agreement with the wind tunnel data. Both the side force coefficient and rolling moment coeffi-cients increase steadily with yaw angle till about 50? before starting to exhibit an asymptotic behavior. Contours of velocity magnitude were also computed at different cross-sections of the train along its length for different yaw angles. The result showed that magnitude of rotating vortex in the lee ward side increased with increasing yaw angle, which

  17. Modeling the Aerodynamics and Performances of a Historic Airplane: the Spanish

    Directory of Open Access Journals (Sweden)

    A. González-Betes

    2003-01-01

    Full Text Available The process of modeling the aerodynamics and performances of a historic airplane is very similar to the conceptual and preliminary design phases of a new plane, with the advantage of knowing the configuration and that the airplane was airworthy; thus it is unnecessary to outline and assess many different alternatives. However, the drag polar, the real performances, stability features, etc, are still unknown. For various reasons (in particular because of two World Wars, or the Civil War in the Spanish case most details of many historical airplanes have been lost.In the present research work, the situation is as follows. In June 1933 the "Cuatro Vientos", a Spanish-built Bréguet XIX Super TR, flew non-stop from Seville to Cuba; a distance of 7500 km (about 4100 nautical miles in around 40 hours. A few days later, in a far less complicated stage between Havana and Mexico, the airplane was lost with its occupants to a storm in the Yucatan peninsula.The modeling considered in this paper starts by addressing the aerodynamic modifications introduced in the airplane for the extremely long flight. Then, with the help of old and present day aerodynamic data and methods the drag polar is estimated. The available engine data is completed and extrapolated to obtain information on power and fuel consumption. Finally, all this data is integrated to provide a reliable and technically sound reproduction of the Seville-Cuba flight.

  18. Coupled Analysis of Unsteady Aerodynamics and Vehicle Motion of a Passenger Car in Crosswind Condition

    Directory of Open Access Journals (Sweden)

    T. M. Huang

    2017-01-01

    Full Text Available High-speed passenger car requires a lighter weight for improving power performance and reducing fuel consumption; a car with higher-speed and lighter weight will lead to the passenger car more sensitive to the crosswind, which will affect the stability and drivability of the passenger car. This study employs the fully-coupled method to investigate a passenger car subjected “1-cos” crosswind with consideration of the vehicle motion. Large eddy simulation (LES and dynamic mesh is adopted to investigate the unsteady aerodynamic, and the vehicle is treated as a three-freedom-system and driver’s control is considered to investigate the vehicle dynamic. The one-way simulation and quasi-steady simulation are also conducted to compare with the fully-coupled simulation. The results of the three simulation methods show large difference. The peak value of the lateral displacement in fully-coupled simulation is the smallest between the three simulation approaches. While the change of aerodynamic loads and vehicle motion in fully-coupled simulation is more complicated than in one-way and quasi-steady simulation. These results clearly indicate the significance of including of the unsteady aerodynamic loads in passenger car moving analysis.

  19. Effect of tip geometry and tip clearance on aerodynamic performance of a linear compressor cascade

    Institute of Scientific and Technical Information of China (English)

    Zhong Jingjun; Han Shaobing; Lu Huawei; Kan Xiaoxu

    2013-01-01

    The tip leakage flow between a blade and a casing wall has a strong impact on compressor pressure rise capability,efficiency,and stability.Consequently,there is a strong motivation to look for means to minimize its impact on performance.This paper presents the potential of passive tip leakage flow control to increase the aerodynamic performance of highly loaded compressor blades.Experimental investigations on a linear compressor cascade equipped with blade winglets mounted to the blade tips have been carried out.Results for a variation of the tip clearance and the winglet geometry are presented.Current results indicate that the use of proper tip winglets in a compressor cascade can positively affect the local aerodynamic field by weakening the tip leakage vortex.Results also show that the suction-side winglets are aerodynamically superior to the pressure-side or combined winglets.The suction-side winglets are capable of reducing the exit total pressure loss associated with the tip leakage flow and the passage secondary flow to a significant degree.

  20. Influence of anisotropic piezoelectric actuators on wing aerodynamic forces

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Changing the shape of an airfoil to enhance overall aircraft performance has always been a goal of aircraft designers. Using smart material to reshape the wing can improve aerodynamic performance. The influence of anisotropic effects of piezoelectric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated. Test verification was conducted.

  1. Influence of anisotropic piezoelectric actuators on wing aerodynamic forces

    Institute of Scientific and Technical Information of China (English)

    GUAN De; LI Min; LI Wei; WANG MingChun

    2008-01-01

    Changing the shape of an airfoil to enhance overall aircraft performance has always been s goal of aircraft designers.Using smart material to reshape the wing can improve aerodynamic performance.The influence of anisotropic effects of piezo-electric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated.Test verification was conducted.

  2. Exploring the Aerodynamic Drag of a Moving Cyclist

    Science.gov (United States)

    Theilmann, Florian; Reinhard, Christopher

    2016-01-01

    Although the physics of cycling itself is a complex mixture of aerodynamics, physiology, mechanics, and heuristics, using cycling as a context for teaching physics has a tradition of certainly more than 30 years. Here, a possible feature is the discussion of the noticeable resistant forces such as aerodynamic drag and the associated power…

  3. Experimental Investigation of Aerodynamic Instability of Iced Bridge Cable Sections

    DEFF Research Database (Denmark)

    Koss, Holger; Lund, Mia Schou Møller

    2013-01-01

    of bridge cables under wind action. This paper describes the experimental simulation of ice accretion on a real bridge cable sheet HDPE tube segment (diameter 160mm) and its effect on the aerodynamic load. Furthermore, aerodynamic instability will be estimated with quasi-steady theory using the determined...

  4. Mathematical modeling of the aerodynamic characteristics in flight dynamics

    Science.gov (United States)

    Tobak, M.; Chapman, G. T.; Schiff, L. B.

    1984-01-01

    Basic concepts involved in the mathematical modeling of the aerodynamic response of an aircraft to arbitrary maneuvers are reviewed. The original formulation of an aerodynamic response in terms of nonlinear functionals is shown to be compatible with a derivation based on the use of nonlinear functional expansions. Extensions of the analysis through its natural connection with ideas from bifurcation theory are indicated.

  5. State of the art in wind turbine aerodynamics and aeroelasticity

    DEFF Research Database (Denmark)

    Hansen, Martin Otto Laver; Sørensen, Jens Nørkær; Voutsinas, S

    2006-01-01

    A comprehensive review of wind turbine aeroelasticity is given. The aerodynamic part starts with the simple aerodynamic Blade Element Momentum Method and ends with giving a review of the work done applying CFD on wind turbine rotors. In between is explained some methods of intermediate complexity...

  6. Wind Tunnel Experimental Investigation on the Aerodynamic Characteristics of the Multifin Rockets and Missiles

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The transonic-supersonic wind tunnel experiment on the aerodynamics of the rockets and missiles that have four, six, eight flat or wrap-around fins is introduced. The experimental results show, while M∞<2.0, with the increase of the fins' number, the derivative of lift coefficient is increasing, the pressure center is shifting backwards, and the longitudinal static stability is augmenting. On the contrary, while the Mach number exceeds a certain supersonic value, the aerodynamic effectiveness of the eight-fin missiles would be lower than that of the six-fin missiles. For the low speed short-range missiles, by adopting six, eight or ten flat fins configuration, the lift effectiveness can be greatly increased, the pressure center can be shifted backwards, the static and dynamic stability can be obviously enhanced. For the high speed long-range large rockets and missiles launched from multi-tube launcher, the configuration adopting more than six fins can not be useful for increasing the stability but would make the rolling rate instable during the flight.

  7. Aeroassist flight experiment aerodynamics and aerothermodynamics

    Science.gov (United States)

    Brewer, Edwin B.

    1989-01-01

    The problem is to determine the transitional flow aerodynamics and aerothermodynamics, including the base flow characteristics, of the Aeroassist Flight Experiment (AFE). The justification for the computational fluid dynamic (CFD) Application stems from MSFC's system integration responsibility for the AFE. To insure that the AFE objectives are met, MSFC must understand the limitations and uncertainties of the design data. Perhaps the only method capable of handling the complex physics of the rarefied high energy AFE trajectory is Bird's Direct Simulation Monte Carlo (DSMC) technique. The 3-D code used in this analysis is applicable only to the AFE geometry. It uses the Variable Hard Sphere (VHS) collision model and five specie chemistry model available from Langley Research Center. The code is benchmarked against the AFE flight data and used as an Aeroassisted Space Transfer Vehicle (ASTV) design tool. The code is being used to understand the AFE flow field and verify or modify existing design data. Continued application to lower altitudes is testing the capability of the Numerical Aerodynamic Simulation Facility (NASF) to handle 3-D DSMC and its practicality as an ASTV/AFE design tool.

  8. Aerodynamic Design of a Locomotive Fairing

    Science.gov (United States)

    Stucki, Chad; Maynes, Daniel

    2016-11-01

    Rising fuel cost has motivated increased fuel efficiency of freight trains. At cruising speed, the largest contributing factor to the fuel consumption is the aerodynamic drag. As a result of air stagnation at the front of the train and substantial flow separation behind, the leading locomotive and trailing railcar experience greater drag than intermediate cars. This work introduces the design of streamlined nose fairings to be attached to freight locomotives as a means of reducing the leading locomotive drag. The aerodynamic performance of each fairing design is modeled using a commercial CFD software package. The K-epsilon turbulence model is used, and fluid properties are equivalent to atmospheric air at standard conditions. A selection of isolated screening studies are performed, and a multidimensional regression is used to predict optimal-performing fairing designs. Between screening studies, careful examination of the flow field is performed to inspire subsequent fairing designs. Results are presented for 250 different nose fairings. The best performing fairing geometry predicts a nominal drag reduction of 17% on the lead locomotive in a train set. This drag reduction is expected to result in nearly 1% fuel savings for the entire train.

  9. Influence of ribs on train aerodynamic performances

    Institute of Scientific and Technical Information of China (English)

    MIAO Xiu-juan; GAO Guang-jun

    2015-01-01

    The influence of ribs on the train aerodynamic performance was computed using detached eddy simulation (DES), and the transient iteration was solved by the dual-time step lower-upper symmetric Gauss-Seidel (LU-SGS) method. The results show that the ribs installed on the roof have a great effect on the train aerodynamic performance. Compared with trains without ribs, the lift force coefficient of the train with convex ribs changes from negative to positive, while the side force coefficient increases by 110% and 88%, respectively. Due to the combined effect of the lift force and side force, the overturning moment of the train with convex ribs and cutting ribs increases by 140% and 106%, respectively. There is larger negative pressure on the roof of the train without ribs than that with ribs. The ribs on the train would disturb the flow structure and contribute to the air separation, so the separation starts from the roof, while there is no air separation on the roof of the train without ribs. The ribs can also slow down the flow speed above the roof and make the air easily sucked back to the train surface. The vortices at the leeward side of the train without ribs are small and messy compared with those of the train with convex or cutting ribs.

  10. Cricket Ball Aerodynamics: Myth Versus Science

    Science.gov (United States)

    Mehta, Rabindra D.; Koga, Demmis J. (Technical Monitor)

    2000-01-01

    Aerodynamics plays a prominent role in the flight of a cricket ball released by a bowler. The main interest is in the fact that the ball can follow a curved flight path that is not always under the control of the bowler. ne basic aerodynamic principles responsible for the nonlinear flight or "swing" of a cricket ball were identified several years ago and many papers have been published on the subject. In the last 20 years or so, several experimental investigations have been conducted on cricket ball swing, which revealed the amount of attainable swing, and the parameters that affect it. A general overview of these findings is presented with emphasis on the concept of late swing and the effects of meteorological conditions on swing. In addition, the relatively new concept of "reverse" swing, how it can be achieved in practice and the role in it of ball "tampering", are discussed in detail. A discussion of the "white" cricket ball used in last year's World Cup, which supposedly possesses different swing properties compared to a conventional red ball, is also presented.

  11. THERMAL STRESS IN METEOROIDS BY AERODYNAMIC HEATING

    Institute of Scientific and Technical Information of China (English)

    Chi-YuKing

    2003-01-01

    Thermal stress in meteoroids by aerodynamic heating is calculated for the ideal case of an isotropic,homogeneous,elastic sphere being heated at the surface with a constant heattransfer coefficient. Given enough time,the tensile stress in the interior of the meteoroid can be as high as 10 kb. This stress value is greater than estimated tensile strengths of meteoroids and the aerodynamic compression they encounter. Significant thermal stress(1 kb) can develop quickly (within a few tens of seconds) in a small(radius<10 cm) stony meteoroid and a somewhat large(radius<l m)metallic meteoroid,and thus may cause tensile fracture to initiate in the meteotoid's interior. Fracture by thermal stress may have contributed to such observations as the existence of dust particles in upper atmosphere,the breakup of meteoroids at relatively low altitudes, the angular shape of meteorites and their wide scattering in a strewn field,and the explosive features of impact craters. In large meteoroids that require longer heating for thermal stress to fully develop, its effect is probably insignificant. The calculated stress values may be upper limits for real meteoroids which suffer melting and ablation at the surface.

  12. THERMAL STRESS IN METEOROIDS BY AERODYNAMIC HEATING

    Institute of Scientific and Technical Information of China (English)

    Chi-Yu King

    2003-01-01

    Thermal stress in meteoroids by aerodynamic heating is calculated for the ideal case of an isotropic,homogeneous,elastic sphere being heated at the surface with a constant heattransfer coefficient. Given enough time, the tensile stress in the interior of the meteoroid can be as high as 10 kb. This stress value is greater than estimated tensile strengths of meteoroids and the aerodynamic compression they encounter. Significant thermal stress(1 kb) can develop quickly within a few tens of seconds) in a small(radius<10 cm) stony meteoroid and a somewhat large radius<l m)metallic meteoroid,and thus may cause tensile fracture to initiate in the meteotoid's interior. Fracture by thermal stress may have contributed to such observations as the existence of dust particles in upper atmosphere,the breakup of meteoroids at relatively low altitudes, the angular shape of meteorites and their wide scattering in a strewn field,and the explosive features of impact craters. In large meteoroids that require longer heating for thermal stress to fully develop,its effect is probably insignificant. The calculated stress values may be upper limits for real meteoroids which suffer melting and ablation at the surface.

  13. WECS Incompressible Complex Configuration Aerodynamics (WICCA)

    Energy Technology Data Exchange (ETDEWEB)

    Preuss, R.; Morino, L.

    1976-05-01

    A finite-element method for determining the aerodynamic loading on rotors is presented. The report describes the development of the formulation for the steady state and numerical results for horizontal axis windmills. It is based on a general theory for uncompressible potential aerodynamics for complex configurations in a rotating frame of reference. If a rotor is rotating at constant angular velocity and is directed along a uniform wind distribution, the problem may be solved in the steady state for a frame of reference rotating with the rotor. A computer program (WICCA) has been designed to incorporate the method, and results compare favorably with an existing lifting surface formation. The program has been modified to include the hub for analysis. Further modifications are planned to study the effect of the coning angle, chord length distribution, blade pitch angle distribution, and airfoil section. The method may also be applied to unsteady flow problems such as non-uniform wind distributions (windmills in shear winds). The appendices contain graphs, the verification of expressions for the indefinite doublet and source integrals, proof of far wake, and hub geometry.

  14. Redesigned rotor for a highly loaded, 1800 ft/sec tip speed compressor fan stage 1: Aerodynamic and mechanical design

    Science.gov (United States)

    Halle, J. E.; Ruschak, J. T.

    1975-01-01

    A highly loaded, high tip-speed fan rotor was designed with multiple-circular-arc airfoil sections as a replacement for a marginally successful rotor which had precompression airfoil sections. The substitution of airfoil sections was the only aerodynamic change. Structural design of the redesigned rotor blade was guided by successful experience with the original blade. Calculated stress levels and stability parameters for the redesigned rotor are within limits demonstrated in tests of the original rotor.

  15. Stability versus Maneuverability in Hovering Flight

    CERN Document Server

    Huang, Yangyang; Kanso, Eva

    2014-01-01

    Insects and birds are often faced by opposing requirements for agile and stable flight. Here, we explore the interplay between aerodynamic effort, maneuverability, and stability in a model system that consists of a $\\Lambda$-shaped flyer hovering in a vertically oscillating airflow. We determine effective conditions that lead to periodic hovering in terms of two parameters: the flyer's shape (opening angle) and the effort (flow acceleration) needed to keep the flyer aloft. We find optimal shapes that minimize effort. We then examine hovering stability and observe a transition from unstable, yet maneuverable, to stable hovering. Interestingly, this transition occurs at post-optimal shapes, that is, at increased aerodynamic effort. These results have profound implications on the interplay between stability and maneuverability in live organisms as well as on the design of man-made air vehicles.

  16. Evaluation of Ares-I Control System Robustness to Uncertain Aerodynamics and Flex Dynamics

    Science.gov (United States)

    Jang, Jiann-Woei; VanTassel, Chris; Bedrossian, Nazareth; Hall, Charles; Spanos, Pol

    2008-01-01

    This paper discusses the application of robust control theory to evaluate robustness of the Ares-I control systems. Three techniques for estimating upper and lower bounds of uncertain parameters which yield stable closed-loop response are used here: (1) Monte Carlo analysis, (2) mu analysis, and (3) characteristic frequency response analysis. All three methods are used to evaluate stability envelopes of the Ares-I control systems with uncertain aerodynamics and flex dynamics. The results show that characteristic frequency response analysis is the most effective of these methods for assessing robustness.

  17. Free wake analysis of wind turbine aerodynamics. Wind energy conversion. ASRL-TR-184-14

    Energy Technology Data Exchange (ETDEWEB)

    Gohard, J.C.

    1978-09-01

    The underlying theory is presented for determining blade and rotor/tower vibration and dynamic stability characteristics as well as the basic dynamic (as opposed to aerodynamic) operating loads. Starting with a simple concept of equivalent hinged rotors, the equations of motion for the blade including pitch, flap and lag motions are developed. The nonlinear equations are derived first and linearized about a finite displacement of the blade out of the plane of rotation. This is important since wind turbines tend to operate at relatively high coning angles. The effect of distributed flexibility, as opposed to the equivalent hinge concept, is then discussed.

  18. Drones for aerodynamic and structural testing /DAST/ - A status report

    Science.gov (United States)

    Murrow, H. N.; Eckstrom, C. V.

    1978-01-01

    A program for providing research data on aerodynamic loads and active control systems on wings with supercritical airfoils in the transonic speed range is described. Analytical development, wind tunnel tests, and flight tests are included. A Firebee II target drone vehicle has been modified for use as a flight test facility. The program currently includes flight experiments on two aeroelastic research wings. The primary purpose of the first flight experiment is to demonstrate an active control system for flutter suppression on a transport-type wing. Design and fabrication of the wing are complete and after installing research instrumentation and the flutter suppression system, flight testing is expected to begin in early 1979. The experiment on the second research wing - a fuel-conservative transport type - is to demonstrate multiple active control systems including flutter suppression, maneuver load alleviation, gust load alleviation, and reduce static stability. Of special importance for this second experiment is the development and validation of integrated design methods which include the benefits of active controls in the structural design.

  19. Study of aerodynamical and mechanical behaviours of Savonius rotor

    Energy Technology Data Exchange (ETDEWEB)

    Aouachria, Z. [Hadj Lakhdar Univ., Batna (Algeria). Applied Energetic Physic Laboratory

    2007-07-01

    Although the efficiency of a Savonius rotor is not as high conventional propeller-type and Darrieus wind turbines, it has the advantage of simple construction; acceptance of wind from various directions, thereby eliminating the need for reorientation; high starting torque; and, relatively low operating speed. These advantages outweigh its low efficiency and make it an ideal economic source to meet small-scale power requirements. The instantaneous pressure field on the blades surface was determined in order to analyze the flow around a Savonius rotor. A two dimensional analysis was used to determine the aerodynamic strengths, which led to underline the Magnus effect and to vibrations on the rotor. An anti-vibratory system was also proposed to stabilize or avoid these vibrations. The drag and lift coefficients were found to be in good agreement with results reported in literature. This study identified an inversion lift effect on a Savonius rotor, which closely resembled the Reynolds number, particularly in the peripheral speed coefficient values. It was shown that the machine does not move in accordance with the Magnus effect. 22 refs., 1 tab., 9 figs.

  20. STUDY ON AERODYNAMIC CHARACTERISTICS OF VAN-BODY TRUCKS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The aerodynamic characteristics of the van-body truck were studied by means of theoretical analysis, numerical simulation and wind tunnel experiments. The concept of critical length was presented for the van-body truck in wind tunnel experiments, the proper critical Reynolds number was found and the effects of ground parameters in ground effect simulation on the aerodynamic measurements were examined. It shows that two structure parameters, van height and the gap between the cab and the van, can obviously influence the aerodynamic characteristics, and the additional aerodynamic devices, the wind deflector and the vortex regulator in the rear, can considerably reduce the aerodynamic drag of the van-body truck. Numerical simulations provided rich information of the flow fields around the van-body trucks.

  1. Aerodynamic study on wing and tail small UAV without runways

    Science.gov (United States)

    Soetanto, Maria F.; R., Randy; Alfan M., R.; Dzaldi

    2016-06-01

    This paper consists of the design and analysis of the aerodynamics of the profiles of wing and tail of a Small Unmanned Aerial Vehicle (UAV). UAV is a remote-controlled aircraft that can carry cameras, sensors and even weapons on an area that needed aerial photography or aerial video [1]. The aim of this small UAV is for used in situations where manned flight is considered too risky or difficult, such as fire fighting or surveillance, while the term 'small means the design of this UAV has to be relatively small and portable so that peoples are able to carry it during their operations [CASR Part 101.240: it is a UAV which is has a launch mass greater than 100 grams but less than 100 kilograms] [2]. Computational Fluid Dynamic (CFD) method was used to analyze the fluid flow characteristics around the aerofoil's profiles, such as the lift generation for each angle of attack and longitudinal stability caused by vortex generation on trailing edge. Based on the analysis and calculation process, Clark-Y MOD with aspect ratio, AR = 4.28 and taper ratio, λ = 0.65 was chosen as the wing aerofoil and SD 8020 with AR = 4.8 and λ = 0.5 was chosen as the horizontal tail, while SD 8020 with AR = 1.58 and λ = 0.5 was chosen as the vertical tail. The lift and drag forces generated for wing and tail surfaces can be determined from the Fluent 6.3 simulation. Results showed that until angle of attack of 6 degrees, the formation of flow separation is still going on behind the trailing edge, and the stall condition occurs at 14 degrees angle of attack which is characterized by the occurrence of flow separation at leading edge, with a maximum lift coefficient (Cl) obtained = 1.56. The results of flight tests show that this small UAV has successfully maneuvered to fly, such as take off, some acrobatics when cruising and landing smoothly, which means that the calculation and analysis of aerodynamic aerofoil's profile used on the wing and tail of the Small UAV were able to be validated.

  2. A generalized solution of elasto-aerodynamic lubrication for aerodynamic compliant foil bearings

    Institute of Scientific and Technical Information of China (English)

    YU; Lie; QI; Shemiao; GENG; Haipeng

    2005-01-01

    Although aerodynamic compliant foil bearings are successfully applied in a number of turbo-machineries, theoretical researches on the modeling, performance prediction of compliant foil bearings and the dynamic analysis of the related rotor system seem still far behind the experimental investigation because of structural complexity of the foil bearings. A generalized solution of the elasto-aerodynamic lubrication is presented in this paper by introducing both static and dynamic deformations of foils and solving gas-lubricated Reynolds equations with deformation equations simultaneously. The solution can be used for the calculation of dynamic stiffness and damping, as well as the prediction of static performances of foil bearings. Systematical theories and methods are also presented for the purpose of the prediction of dynamic behavior of a rotor system equipped with foil bearings.

  3. Ares I Aerodynamic Testing at the Boeing Polysonic Wind Tunnel

    Science.gov (United States)

    Pinier, Jeremy T.; Niskey, Charles J.; Hanke, Jeremy L.; Tomek, William G.

    2011-01-01

    Throughout three full design analysis cycles, the Ares I project within the Constellation program has consistently relied on the Boeing Polysonic Wind Tunnel (PSWT) for aerodynamic testing of the subsonic, transonic and supersonic portions of the atmospheric flight envelope (Mach=0.5 to 4.5). Each design cycle required the development of aerodynamic databases for the 6 degree-of-freedom (DOF) forces and moments, as well as distributed line-loads databases covering the full range of Mach number, total angle-of-attack, and aerodynamic roll angle. The high fidelity data collected in this facility has been consistent with the data collected in NASA Langley s Unitary Plan Wind Tunnel (UPWT) at the overlapping condition ofMach=1.6. Much insight into the aerodynamic behavior of the launch vehicle during all phases of flight was gained through wind tunnel testing. Important knowledge pertaining to slender launch vehicle aerodynamics in particular was accumulated. In conducting these wind tunnel tests and developing experimental aerodynamic databases, some challenges were encountered and are reported as lessons learned in this paper for the benefit of future crew launch vehicle aerodynamic developments.

  4. Multiprocessing on supercomputers for computational aerodynamics

    Science.gov (United States)

    Yarrow, Maurice; Mehta, Unmeel B.

    1991-01-01

    Little use is made of multiple processors available on current supercomputers (computers with a theoretical peak performance capability equal to 100 MFLOPS or more) to improve turnaround time in computational aerodynamics. The productivity of a computer user is directly related to this turnaround time. In a time-sharing environment, such improvement in this speed is achieved when multiple processors are used efficiently to execute an algorithm. The concept of multiple instructions and multiple data (MIMD) is applied through multitasking via a strategy that requires relatively minor modifications to an existing code for a single processor. This approach maps the available memory to multiple processors, exploiting the C-Fortran-Unix interface. The existing code is mapped without the need for developing a new algorithm. The procedure for building a code utilizing this approach is automated with the Unix stream editor.

  5. Methods of reducing vehicle aerodynamic drag

    Energy Technology Data Exchange (ETDEWEB)

    Sirenko V.; Rohatgi U.

    2012-07-08

    A small scale model (length 1710 mm) of General Motor SUV was built and tested in the wind tunnel for expected wind conditions and road clearance. Two passive devices, rear screen which is plate behind the car and rear fairing where the end of the car is aerodynamically extended, were incorporated in the model and tested in the wind tunnel for different wind conditions. The conclusion is that rear screen could reduce drag up to 6.5% and rear fairing can reduce the drag by 26%. There were additional tests for front edging and rear vortex generators. The results for drag reduction were mixed. It should be noted that there are aesthetic and practical considerations that may allow only partial implementation of these or any drag reduction options.

  6. Aerodynamics of advanced axial-flow turbomachinery

    Science.gov (United States)

    Serovy, G. K.; Kavanagh, P.; Kiishi, T. H.

    1980-01-01

    A multi-task research program on aerodynamic problems in advanced axial-flow turbomachine configurations was carried out at Iowa State University. The elements of this program were intended to contribute directly to the improvement of compressor, fan, and turbine design methods. Experimental efforts in intra-passage flow pattern measurements, unsteady blade row interaction, and control of secondary flow are included, along with computational work on inviscid-viscous interaction blade passage flow techniques. This final report summarizes the results of this program and indicates directions which might be taken in following up these results in future work. In a separate task a study was made of existing turbomachinery research programs and facilities in universities located in the United States. Some potentially significant research topics are discussed which might be successfully attacked in the university atmosphere.

  7. WECS incompressible Lifting Surface Aerodynamics (WILSA)

    Energy Technology Data Exchange (ETDEWEB)

    Suciu, E.; Morino, L.

    1976-05-01

    A method is described for computing the distribution for a zero-thickness horizontal axis windmill, as well as for obtaining the power coefficient. The problem is formulated in terms of velocity potential, and the study deals with a nonlinear finite-element lifting-surface analysis of horizontal-axis windmills in a steady incompressible, inviscid, irrotational flow, with a prescribed helicoidal wake. A zero-order-finite-element analysis is used with a straight-vortex line wake. The correct wake geometry is obtained and the pressure coefficient calculated using both linearized and nonlinear forms of the Bernoulli Theorem. The numerical results compare well with those obtained with Windmill Incompressible Complex Configuration Aerodynamics (WICCA), a computer program for solving the same problem which uses a completely different integral equation. A number of suggestions are offered to improve the model presented.

  8. Wind Turbines: Unsteady Aerodynamics and Inflow Noise

    DEFF Research Database (Denmark)

    Broe, Brian Riget

    ; and Graham, J. M. R.: 1970, Lifting surface theory for the problem of an arbitrarily yawed sinusoidal gust incident on a thin aerofoil in incompressible flow). Two of these models are investigated to find the unsteady lift distribution or pressure difference as function of chordwise position on the aerofoil...... (Sears, W. R.: 1941; and Graham, J. M. R.: 1970). An acoustic model is investigated using a model for the lift distribution as input (Amiet, R. K.: 1975, Acoustic radiation from an airfoil in a turbulent stream). The two models for lift distribution are used in the acoustic model. One of the models...... and the perfectly isotropic turbulent model. This indicates that the models capture the aerodynamics well. Thus the measurements suggest that the noise due to atmospheric turbulence can be described and modeled by the two models for lift distribution. It was not possible to test the acoustical model...

  9. Aerodynamic levitation : an approach to microgravity.

    Energy Technology Data Exchange (ETDEWEB)

    Glorieux, B.; Saboungi, M.-L.; Millot, F.; Enderby, J.; Rifflet, J.-C.

    2000-12-05

    Measurements of the thermophysical and structural properties of liquid materials at high temperature have undergone considerable development in the past few years. Following improvements in electromagnetic levitation, aerodynamic levitation associated with laser heating has shown promise for assessing properties of different molten materials (metals, oxides, and semiconductors), preserving sample purity over a wide range of temperatures and under different gas environments. The density, surface tension and viscosity are measured with a high-speed video camera and an image analysis system. Results on nickel and alumina show that small droplets can be considered in the first approximation to be under microgravity conditions. Using a non-invasive contactless technique recently developed to measure electrical conductivity, results have been extended to variety of materials ranging from liquid metals and liquid semiconductors to ionically conducting materials. The advantage of this technique is the feasibility of monitoring changes in transport occurring during phase transitions and in deeply undercooled states.

  10. Aerodynamic Optimization of Micro Aerial Vehicle

    Directory of Open Access Journals (Sweden)

    Siew Ping Yeong

    2016-01-01

    Full Text Available Computational fluid dynamics (CFD study was done on the propeller design of a micro aerial vehicle (quadrotor-typed to optimize its aerodynamic performance via Shear Stress Transport K-Omega (SST k-ω turbulence model. The quadrotor model used was WL-V303 Seeker. The design process started with airfoils selection and followed by the evaluation of drone model in hovering and cruising conditions. To sustain a 400g payload, by Momentum Theory an ideal thrust of 5.4 N should be generated by each rotor of the quadrotor and this resulted in an induced velocity of 7.4 m/s on the propeller during hovering phase, equivalent to Reynolds number of 10403 at 75% of the propeller blade radius. There were 6 propellers investigated at this Reynolds number. Sokolov airfoil which produced the largest lift-to-drag ratio was selected for full drone installation to be compared with the original model (benchmark. The CFD results showed that the Sokolov propeller generated 0.76 N of thrust more than the benchmark propeller at 7750 rpm. Despite generating higher thrust, higher drag was also experienced by the drone installed with Sokolov propellers. This resulted in lower lift-to-drag ratio than the benchmark propellers. It was also discovered that the aerodynamic performance of the drone could be further improved by changing the rotating direction of each rotor. Without making changes on the structural design, the drone performance increased by 39.58% in terms of lift-to-drag ratio by using this method.

  11. Prediction of Hyper-X Stage Separation Aerodynamics Using CFD

    Science.gov (United States)

    Buning, Pieter G.; Wong, Tin-Chee; Dilley, Arthur D.; Pao, Jenn L.

    2000-01-01

    The NASA X-43 "Hyper-X" hypersonic research vehicle will be boosted to a Mach 7 flight test condition mounted on the nose of an Orbital Sciences Pegasus launch vehicle. The separation of the research vehicle from the Pegasus presents some unique aerodynamic problems, for which computational fluid dynamics has played a role in the analysis. This paper describes the use of several CFD methods for investigating the aerodynamics of the research and launch vehicles in close proximity. Specifically addressed are unsteady effects, aerodynamic database extrapolation, and differences between wind tunnel and flight environments.

  12. Center for Computational Wind Turbine Aerodynamics and Atmospheric Turbulence

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær

    2014-01-01

    In order to design and operate a wind farm optimally it is necessary to know in detail how the wind behaves and interacts with the turbines in a farm. This not only requires knowledge about meteorology, turbulence and aerodynamics, but it also requires access to powerful computers and efficient...... software. Center for Computational Wind Turbine Aerodynamics and Atmospheric Turbulence was established in 2010 in order to create a world-leading cross-disciplinary flow center that covers all relevant disciplines within wind farm meteorology and aerodynamics....

  13. Prediction of Aerodynamic Coefficients using Neural Networks for Sparse Data

    Science.gov (United States)

    Rajkumar, T.; Bardina, Jorge; Clancy, Daniel (Technical Monitor)

    2002-01-01

    Basic aerodynamic coefficients are modeled as functions of angles of attack and sideslip with vehicle lateral symmetry and compressibility effects. Most of the aerodynamic parameters can be well-fitted using polynomial functions. In this paper a fast, reliable way of predicting aerodynamic coefficients is produced using a neural network. The training data for the neural network is derived from wind tunnel test and numerical simulations. The coefficients of lift, drag, pitching moment are expressed as a function of alpha (angle of attack) and Mach number. The results produced from preliminary neural network analysis are very good.

  14. Fourier analysis of the aerodynamic behavior of cup anemometers

    Science.gov (United States)

    Pindado, Santiago; Pérez, Imanol; Aguado, Maite

    2013-06-01

    The calibration results (the transfer function) of an anemometer equipped with several cup rotors were analyzed and correlated with the aerodynamic forces measured on the isolated cups in a wind tunnel. The correlation was based on a Fourier analysis of the normal-to-the-cup aerodynamic force. Three different cup shapes were studied: typical conical cups, elliptical cups and porous cups (conical-truncated shape). Results indicated a good correlation between the anemometer factor, K, and the ratio between the first two coefficients in the Fourier series decomposition of the normal-to-the-cup aerodynamic force.

  15. Aerodynamic and Acoustic Flight Test Results for the Stratospheric Observatory for Infrared Astronomy

    Science.gov (United States)

    Cumming, Stephen B.; Cliatt, Larry James; Frederick, Michael A.; Smith, Mark S.

    2013-01-01

    As part of the Stratospheric Observatory for Infrared Astronomy (SOFIA) program, a 747SP airplane was modified to carry a 2.5 meter telescope in the aft section of the fuselage. The resulting airborne observatory allows for observations above 99 percent of the water vapor in the atmosphere. The open cavity created by the modifications had the potential to significantly affect the airplane in the areas of aerodynamics and acoustics. Several series of flight tests were conducted to clear the airplanes operating envelope for astronomical observations, planned to be performed between the altitudes of 39,000 feet and 45,000 feet. The flight tests were successfully completed. Cavity acoustics were below design limits, and the overall acoustic characteristics of the cavity were better than expected. The modification did have some effects on the stability and control of the airplane, but these effects were not significant. Airplane air data systems were not affected by the modifications. This paper describes the methods used to examine the aerodynamics and acoustic data from the flight tests and provides a discussion of the flight test results in the areas of cavity acoustics, stability and control, and air data.

  16. Aerodynamic and Acoustic Flight Test Results and Results for the Stratospheric Observatory for Infrared Astronomy

    Science.gov (United States)

    Cumming, Stephen B.; Smith, Mark S.; Cliatt, Larry J.; Frederick, Michael A.

    2014-01-01

    As part of the Stratospheric Observatory for Infrared Astronomy program, a 747SP airplane was modified to carry a 2.5-m telescope in the aft section of the fuselage. The resulting airborne observatory allows for observations above 99 percent of the water vapor in the atmosphere. The open cavity created by the modifications had the potential to significantly affect the airplane in the areas of aerodynamics and acoustics. Several series of flight tests were conducted to clear the operating envelope of the airplane for astronomical observations, planned to be performed between the altitudes of 35,000 ft and 45,000 ft. The flight tests were successfully completed. Cavity acoustics were below design limits, and the overall acoustic characteristics of the cavity were better than expected. The modification did have some effects on the stability and control of the airplane, but these effects were not significant. Airplane air data systems were not affected by the modifications. This paper describes the methods used to examine the aerodynamics and acoustic data from the flight tests and provides a discussion of the flight-test results in the areas of cavity acoustics, stability and control, and air data.

  17. Control of Pitching Airfoil Aerodynamics by Vorticity Flux Modification using Active Bleed

    Science.gov (United States)

    Kearney, John; Glezer, Ari

    2014-11-01

    Distributed active bleed driven by pressure differences across a pitching airfoil is used to regulate the vorticity flux over the airfoil's surface and thereby to control aerodynamic loads in wind tunnel experiments. The range of pitch angles is varied beyond the static stall margin of the 2-D VR-7 airfoil at reduced pitching rates up to k = 0.42. Bleed is regulated dynamically using piezoelectric louvers between the model's pressure side near the trailing edge and the suction surface near the leading edge. The time-dependent evolution of vorticity concentrations over the airfoil and in the wake during the pitch cycle is investigated using high-speed PIV and the aerodynamic forces and moments are measured using integrated load cells. The timing of the dynamic stall vorticity flux into the near wake and its effect on the flow field are analyzed in the presence and absence of bleed using proper orthogonal decomposition (POD). It is shown that bleed actuation alters the production, accumulation, and advection of vorticity concentrations near the surface with significant effects on the evolution, and, in particular, the timing of dynamic stall vortices. These changes are manifested by alteration of the lift hysteresis and improvement of pitch stability during the cycle, while maintaining cycle-averaged lift to within 5% of the base flow level with significant implications for improvement of the stability of flexible wings and rotor blades. This work is supported by the Rotorcraft Center (VLRCOE) at Georgia Tech.

  18. Physical Insights, Steady Aerodynamic Effects, and a Design Tool for Low-Pressure Turbine Flutter

    Science.gov (United States)

    Waite, Joshua Joseph

    The successful, efficient, and safe turbine design requires a thorough understanding of the underlying physical phenomena. This research investigates the physical understanding and parameters highly correlated to flutter, an aeroelastic instability prevalent among low pressure turbine (LPT) blades in both aircraft engines and power turbines. The modern way of determining whether a certain cascade of LPT blades is susceptible to flutter is through time-expensive computational fluid dynamics (CFD) codes. These codes converge to solution satisfying the Eulerian conservation equations subject to the boundary conditions of a nodal domain consisting fluid and solid wall particles. Most detailed CFD codes are accompanied by cryptic turbulence models, meticulous grid constructions, and elegant boundary condition enforcements all with one goal in mind: determine the sign (and therefore stability) of the aerodynamic damping. The main question being asked by the aeroelastician, "is it positive or negative?'' This type of thought-process eventually gives rise to a black-box effect, leaving physical understanding behind. Therefore, the first part of this research aims to understand and reveal the physics behind LPT flutter in addition to several related topics including acoustic resonance effects. A percentage of this initial numerical investigation is completed using an influence coefficient approach to study the variation the work-per-cycle contributions of neighboring cascade blades to a reference airfoil. The second part of this research introduces new discoveries regarding the relationship between steady aerodynamic loading and negative aerodynamic damping. Using validated CFD codes as computational wind tunnels, a multitude of low-pressure turbine flutter parameters, such as reduced frequency, mode shape, and interblade phase angle, will be scrutinized across various airfoil geometries and steady operating conditions to reach new design guidelines regarding the influence

  19. Performance and Stability of a Winged Vehicle in Ground Effect

    CERN Document Server

    de Divitiis, Nicola

    2009-01-01

    Present work deals with the dynamics of vehicles which intentionally operate in the ground proximity. The dynamics in ground effect is influenced by the vehicle orientation with respect to the ground, since the aerodynamic force and moment coefficients, which in turn depend on height and angle of attack, also vary with the Euler angles. This feature, usually neglected in the applications, can be responsible for sizable variations of the aircraft performance and stability. A further effect, caused by the sink rate, determines unsteadiness that modifies the aerodynamic coefficients. In this work, an analytical formulation is proposed for the force and moment calculation in the presence of the ground and taking the aircraft attitude and sink rate into account. The aerodynamic coefficients are firstly calculated for a representative vehicle and its characteristics in ground effect are investigated. Performance and stability characteristics are then discussed with reference to significant equilibrium conditions, w...

  20. Input Excitation Techniques for Aerodynamic Derivatives Estimation of Highly Augmented Fighter Aircraft

    Directory of Open Access Journals (Sweden)

    N. Shantha Kumar

    1999-07-01

    Full Text Available This paper presents the results of an investigation related to the estimation of lateral-directional aerodynamic derivatives of highly augmented and advanced fighter aircraft from the flight like response data. Different types of pilot inputs are used to generate aircraft response data in the engineer-in-loop flight simulator to determine which input excitation flight provide the most accurate estimates of aircraft stability and control derivatives. Also, MATILABI SIMULINK-based simulation platform is used to generate aircraft response with single-surface excitation to evaluate the usefulness of the method for stability and control derivatives estimation. The maximum likelihood estimation, based on output error utilisation technique is used to estimate the derivatives from the aircraft simulation response data. The results indicate that accuracy of the estimated derivatives improve with persistence excitation and single-surface excitation.

  1. Longitudinal static stability requirements for wing in ground effect vehicle

    Science.gov (United States)

    Yang, Wei; Yang, Zhigang; Collu, Maurizio

    2015-06-01

    The issue of the longitudinal stability of a WIG vehicle has been a very critical design factor since the first experimental WIG vehicle has been built. A series of studies had been performed and focused on the longitudinal stability analysis. However, most studies focused on the longitudinal stability of WIG vehicle in cruise phase, and less is available on the longitudinal static stability requirement of WIG vehicle when hydrodynamics are considered: WIG vehicle usually take off from water. The present work focuses on stability requirement for longitudinal motion from taking off to landing. The model of dynamics for a WIG vehicle was developed taking into account the aerodynamic, hydrostatic and hydrodynamic forces, and then was analyzed. Following with the longitudinal static stability analysis, effect of hydrofoil was discussed. Locations of CG, aerodynamic center in pitch, aerodynamic center in height and hydrodynamic center in heave were illustrated for a stabilized WIG vehicle. The present work will further improve the longitudinal static stability theory for WIG vehicle.

  2. Longitudinal static stability requirements for wing in ground effect vehicle

    Directory of Open Access Journals (Sweden)

    Yang Wei

    2015-06-01

    Full Text Available The issue of the longitudinal stability of a WIG vehicle has been a very critical design factor since the first experimental WIG vehicle has been built. A series of studies had been performed and focused on the longitudinal stability analysis. However, most studies focused on the longitudinal stability of WIG vehicle in cruise phase, and less is available on the longitudinal static stability requirement of WIG vehicle when hydrodynamics are considered: WIG vehicle usually take off from water. The present work focuses on stability requirement for longitudinal motion from taking off to landing. The model of dynamics for a WIG vehicle was developed taking into account the aerodynamic, hydrostatic and hydrodynamic forces, and then was analyzed. Following with the longitudinal static stability analysis, effect of hydrofoil was discussed. Locations of CG, aerodynamic center in pitch, aerodynamic center in height and hydrodynamic center in heave were illustrated for a stabilized WIG vehicle. The present work will further improve the longitudinal static stability theory for WIG vehicle.

  3. High-Fidelity Aerodynamic Design with Transition Prediction Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To enhance aerodynamic design capabilities, Desktop Aeronautics proposes to combine a new sweep/taper integrated-boundary-layer (IBL) code that includes transition...

  4. High-Fidelity Aerodynamic Design with Transition Prediction Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To enhance aerodynamic design capabilities, Desktop Aeronautics proposes to significantly improve upon the integration (performed in Phase 1) of a new sweep/taper...

  5. The Aerodynamics of Heavy Vehicles III : Trucks, Buses and Trains

    CERN Document Server

    Orellano, Alexander

    2016-01-01

    This volume contains papers presented at the International conference “The Aerodynamics of Heavy Vehicles III: Trucks, Buses and Trains” held in Potsdam, Germany, September 12-17, 2010 by Engineering Conferences International (ECI). Leading scientists and engineers from industry, universities and research laboratories, including truck and high-speed train manufacturers and operators were brought together to discuss computer simulation and experimental techniques to be applied for the design of more efficient trucks, buses and high-speed trains in the future.   This conference was the third in the series after Monterey-Pacific Groove in 2002 and Lake Tahoe in 2007.  The presentations address different aspects of train aerodynamics (cross wind effects, underbody flow, tunnel aerodynamics and aeroacoustics, experimental techniques), truck aerodynamics (drag reduction, flow control, experimental and computational techniques) as well as computational fluid dynamics and bluff body, wake and jet flows.

  6. Theoretical and applied aerodynamics and related numerical methods

    CERN Document Server

    Chattot, J J

    2015-01-01

    This book covers classical and modern aerodynamics, theories and related numerical methods, for senior and first-year graduate engineering students, including: -The classical potential (incompressible) flow theories for low speed aerodynamics of thin airfoils and high and low aspect ratio wings. - The linearized theories for compressible subsonic and supersonic aerodynamics. - The nonlinear transonic small disturbance potential flow theory, including supercritical wing sections, the extended transonic area rule with lift effect, transonic lifting line and swept or oblique wings to minimize wave drag. Unsteady flow is also briefly discussed. Numerical simulations based on relaxation mixed-finite difference methods are presented and explained. - Boundary layer theory for all Mach number regimes and viscous/inviscid interaction procedures used in practical aerodynamics calculations. There are also four chapters covering special topics, including wind turbines and propellers, airplane design, flow analogies and h...

  7. The Mechanism of Aerodynamic Hysteresis for Sinusoidally Oscillating Delta Wings

    Institute of Scientific and Technical Information of China (English)

    黄国创; 王玉明; 曹桂兴

    1994-01-01

    An unsteady model of vortex system is developed to simulate the phenomena of aerodynamic hysteresis of sinusoidally oscillating delta wings.The dynamic behavior of leading-edge separation vortices simulated by the present method is in qualitative agreement with that of flow visualization by Gad-el-Hak and Ho.The calculated lift hysteresis loops are in quantitative agreement with the force measurements in the tunnel.The aerodynamic mechanism of the hysteresis phenomena is further investigated by the present method.

  8. Unsteady Low Reynolds Number Aerodynamics for Micro Air Vehicles (MAVs)

    Science.gov (United States)

    2010-05-01

    horizontal model. The first has advantages of placing t he force balance above the water line and thus solving the balance waterproofing i ssues , an d h...ABSTRACT This work introduces the Micro Air Vehicle (MAV) problem from the viewpoint of aerodynamics. Water tunnels are assessed as tools for MAV...aerodynamics. The design, construction and instrumentation of RB’s “Horizontal Free-surface Water Tunnel” is documented. Experiments in steady

  9. Progress in vehicle aerodynamics and thermal management. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Wiedemann, Jochen (ed.) [Stuttgart Univ. (DE). Inst. fuer Kraftfahrwesen und Verbrennungsmotoren (IVK); Forschungsinstitut fuer Kraftfahrwesen und Fahrzeugmotoren (FKFS), Stuttgart (Germany)

    2010-07-01

    Vehicle aerodynamics and thermal management are subjects of increasing importance for automotive development especially regarding the necessity to reduce the energy consumption of the vehicle as well as the need to improve ist comfort. This book is intended for engineers, physicists, and mathematicians who work on vehicle aerodynamics. It is also addressed to people in research organizations, at universities and agencies. It may be of interest to technical journalists and to students. (orig.)

  10. Aerodynamic optimisation of an industrial axial fan blade

    OpenAIRE

    2006-01-01

    Numerical optimisation methods have successfully been used for a variety of aerodynamic design problems over quite a few years. However the application of these methods to the aerodynamic blade shape optimisation of industrial axial fans has received much less attention in the literature probably given the fact that the majority of resources available to develop these automated design approaches is to be found in the aerospace field. This work presents the develo...

  11. Aerodynamics of indirect thrust measurement by the impulse method

    Institute of Scientific and Technical Information of China (English)

    Cheng-Kang Wu; Hai-Xing Wang; Xian Meng; Xi Chen; Wen-Xia Pan

    2011-01-01

    The aerodynamic aspects of indirect thrust measurement by the impulse method have been studied both experimentally and numerically.The underlying basic aerodynamic principle is outlined, the phenomena in subsonic,supersonic and arc-heated jets are explored, and factors affecting the accuracy of the method are studied and discussed.Results show that the impulse method is reliable for indirect thrust measurement if certain basic requirements are met,and a simple guideline for its proper application is given.

  12. Fourier analysis of the aerodynamic behavior of cup anemometers

    OpenAIRE

    Pindado Carrion, Santiago; Pérez Sarasola, Imanol; Aguado Roca, Maite

    2013-01-01

    The calibration results (the transfer function) of an anemometer equipped with several cup rotors were analyzed and correlated with the aerodynamic forces measured on the isolated cups in a wind tunnel. The correlation was based on a Fourier analysis of the normal-to-the-cup aerodynamic force. Three different cup shapes were studied: typical conical cups, elliptical cups and porous cups (conical-truncated shape). Results indicated a good correlation between the anemometer factor, K, and the r...

  13. DOE Project on Heavy Vehicle Aerodynamic Drag

    Energy Technology Data Exchange (ETDEWEB)

    McCallen, R; Salari, K; Ortega, J; Castellucci, P; Pointer, D; Browand, F; Ross, J; Storms, B

    2007-01-04

    Class 8 tractor-trailers consume 11-12% of the total US petroleum use. At highway speeds, 65% of the energy expenditure for a Class 8 truck is in overcoming aerodynamic drag. The project objective is to improve fuel economy of Class 8 tractor-trailers by providing guidance on methods of reducing drag by at least 25%. A 25% reduction in drag would present a 12% improvement in fuel economy at highway speeds, equivalent to about 130 midsize tanker ships per year. Specific goals include: (1) Provide guidance to industry in the reduction of aerodynamic drag of heavy truck vehicles; (2) Develop innovative drag reducing concepts that are operationally and economically sound; and (3) Establish a database of experimental, computational, and conceptual design information, and demonstrate the potential of new drag-reduction devices. The studies described herein provide a demonstration of the applicability of the experience developed in the analysis of the standard configuration of the Generic Conventional Model. The modeling practices and procedures developed in prior efforts have been applied directly to the assessment of new configurations including a variety of geometric modifications and add-on devices. Application to the low-drag 'GTS' configuration of the GCM has confirmed that the error in predicted drag coefficients increases as the relative contribution of the base drag resulting from the vehicle wake to the total drag increases and it is recommended that more advanced turbulence modeling strategies be applied under those circumstances. Application to a commercially-developed boat tail device has confirmed that this restriction does not apply to geometries where the relative contribution of the base drag to the total drag is reduced by modifying the geometry in that region. Application to a modified GCM geometry with an open grille and radiator has confirmed that the underbody flow, while important for underhood cooling, has little impact on the drag

  14. Mechanics and aerodynamics of insect flight control.

    Science.gov (United States)

    Taylor, G K

    2001-11-01

    Insects have evolved sophisticated fight control mechanisms permitting a remarkable range of manoeuvres. Here, I present a qualitative analysis of insect flight control from the perspective of flight mechanics, drawing upon both the neurophysiology and biomechanics literatures. The current literature does not permit a formal, quantitative analysis of flight control, because the aerodynamic force systems that biologists have measured have rarely been complete and the position of the centre of gravity has only been recorded in a few studies. Treating the two best-known insect orders (Diptera and Orthoptera) separately from other insects, I discuss the control mechanisms of different insects in detail. Recent experimental studies suggest that the helicopter model of flight control proposed for Drosophila spp. may be better thought of as a facultative strategy for flight control, rather than the fixed (albeit selected) constraint that it is usually interpreted to be. On the other hand, the so-called 'constant-lift reaction' of locusts appears not to be a reflex for maintaining constant lift at varying angles of attack, as is usually assumed, but rather a mechanism to restore the insect to pitch equilibrium following a disturbance. Differences in the kinematic control mechanisms used by the various insect orders are related to differences in the arrangement of the wings, the construction of the flight motor and the unsteady mechanisms of lift production that are used. Since the evolution of insect flight control is likely to have paralleled the evolutionary refinement of these unsteady aerodynamic mechanisms, taxonomic differences in the kinematics of control could provide an assay of the relative importance of different unsteady mechanisms. Although the control kinematics vary widely between orders, the number of degrees of freedom that different insects can control will always be limited by the number of independent control inputs that they use. Control of the moments

  15. Improved Aerodynamic Analysis for Hybrid Wing Body Conceptual Design Optimization

    Science.gov (United States)

    Gern, Frank H.

    2012-01-01

    This paper provides an overview of ongoing efforts to develop, evaluate, and validate different tools for improved aerodynamic modeling and systems analysis of Hybrid Wing Body (HWB) aircraft configurations. Results are being presented for the evaluation of different aerodynamic tools including panel methods, enhanced panel methods with viscous drag prediction, and computational fluid dynamics. Emphasis is placed on proper prediction of aerodynamic loads for structural sizing as well as viscous drag prediction to develop drag polars for HWB conceptual design optimization. Data from transonic wind tunnel tests at the Arnold Engineering Development Center s 16-Foot Transonic Tunnel was used as a reference data set in order to evaluate the accuracy of the aerodynamic tools. Triangularized surface data and Vehicle Sketch Pad (VSP) models of an X-48B 2% scale wind tunnel model were used to generate input and model files for the different analysis tools. In support of ongoing HWB scaling studies within the NASA Environmentally Responsible Aviation (ERA) program, an improved finite element based structural analysis and weight estimation tool for HWB center bodies is currently under development. Aerodynamic results from these analyses are used to provide additional aerodynamic validation data.

  16. Synergetic Optimization of Missile Shapes for Aerodynamic and Radar Cross-Section Performance Based on Multi- objective Evolutionary Algorithm

    Institute of Scientific and Technical Information of China (English)

    刘洪

    2004-01-01

    A multiple-objective evolutionary algorithm (MOEA) with a new Decision Making (DM) scheme for MOD of conceptual missile shapes was presented, which is contrived to determine suitable tradeoffs from Pareto optimal set using interactive preference articulation. There are two objective functions, to maximize ratio of lift to drag and to minimize radar cross-section (RCS) value. 3D computational electromagnetic solver was used to evaluate RCS, electromagnetic performance. 3D Navier-Stokes flow solver was adopted to evaluate aerodynamic performance. A flight mechanics solver was used to analyze the stability of the missile. Based on the MOEA, a synergetic optimization of missile shapes for aerodynamic and radar cross-section performance is completed. The results show that the proposed approach can be used in more complex optimization case of flight vehicles.

  17. Aerodynamically generated noise by lightning arrester

    Directory of Open Access Journals (Sweden)

    Váchová J.

    2007-10-01

    Full Text Available This paper presents the general solution of aerodynamically generated noise by lightning arrester. Governing equations are presented in form of Lighthill acoustic analogy, as embodied in the Ffowcs Williams-Hawkings (FW-H equation. This equation is based on conservation laws of fluid mechanics rather than on the wave equation. Thus, the FW-H equation is valid even if the integration surface is in nonlinear region. That’s why the FWH method is superior in aeroacoustics. The FW-H method is implemented in program Fluent and the numerical solution is acquired by Fluent code.The general solution of acoustic signal generated by lightning arrester is shown and the results in form of acoustic pressure and frequency spectrum are presented. The verification of accuracy was made by evaluation of Strouhal number. A comparison of Strouhal number for circumfluence of a cylinder and the lightning arrester was done, because the experimental data for cylinder case are known and these solids are supposed to be respectively in shape relation.

  18. IEA joint action. Aerodynamics of wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Maribo Pedersen, B. [ed.

    1997-08-01

    The advances to be made in aerodynamic prediction requires a deeper understanding of the physical processes occurring at the blades, and in the wake, of a wind turbine. This can only come from a continuing process of experimental observation and theoretical analysis. The present symposium presents the opportunity to do this by exchange of data from experiments and simulations, and by discussion of new or modified wake theories. The symposium will consists of a number of presentations by invited speakers and conclude with a summary of the talks and a round-the-table technical discussion. The talks offer the change to present behaviour from full-scale and laboratory experiments that are not explained by existing prediction codes. In addition, presentations are welcome on new modelling techniques or formulations that could make existing codes more accurate, less computationally intensive and easier to use. This symposium is intended to provide a starting point for the formulation of advanced rotor performance methods, which will improve the accuracy of load and performance prediction codes useful to the wind turbine industry. (au)

  19. Unsteady aerodynamic modelling of wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Coton, F.N.; Galbraith, R.A. [Univ. og Glasgow, Dept. of Aerospace Engineering, Glasgow (United Kingdom)

    1997-08-01

    The following current and future work is discussed: Collaborative wind tunnel based PIV project to study wind turbine wake structures in head-on and yawed flow. Prescribed wake model has been embedded in a source panel representation of the wind tunnel walls to allow comparison with experiment; Modelling of tower shadow using high resolution but efficient vortex model in tower shadow domain; Extension of model to yawing flow; Upgrading and tuning of unsteady aerodynamic model for low speed, thick airfoil flows. Glasgow has a considerable collection of low speed dynamic stall data. Currently, the Leishman - Beddoes model is not ideally suited to such flows. For example: Range of stall onset criteria used for dynamic stall prediction including Beddoes. Wide variation of stall onset prediction. Beddoes representation was developed primarily with reference to compressible flows. Analyses of low speed data from Glasgow indicate deficiencies in the current model; Predicted versus measured response during ramp down motion. Modification of the Beddoes representation is required to obtain a fit with the measured data. (EG)

  20. Computational aerodynamics and aeroacoustics for wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Shen, W.Z.

    2009-10-15

    The present thesis consists of 19 selected papers dealing with the development and use of CFD methods for studying the aerodynamics and aero-acoustics of wind turbines. The papers are written in the period from 1997 to 2008 and numbered according to the list in page v. The work consists of two parts: an aerodynamic part based on Computational Fluid Dynamics and an aero-acoustic part based on Computational Aero Acoustics for wind turbines. The main objective of the research was to develop new computational tools and techniques for analysing flows about wind turbines. A few papers deal with applications of Blade Element Momentum (BEM) theory to wind turbines. In most cases the incompressible Navier-Stokes equations in primitive variables (velocity-pressure formulation) are employed as the basic governing equations. However, since fluid mechanical problems essentially are governed by vortex dynamics, it is sometimes advantageous to use the concept of vorticity (defined as the curl of velocity). In vorticity form the Navier-Stokes equations may be formulated in different ways, using a vorticity-stream function formulation, a vorticity-velocity formulation or a vorticity-potential-stream function formulation. In [1] - [3] two different vorticity formulations were developed for 2D and 3D wind turbine flows. In [4] and [5] numerical techniques for avoiding pressure oscillations were developed when solving the velocity-pressure coupling system in the in-house EllipSys2D/3D code. In [6] - [8] different actuator disc techniques combined with CFD are presented. This includes actuator disc, actuator line and actuator surface techniques, which were developed to simulate flows past one or more wind turbines. In [9] and [10] a tip loss correction method that improves the conventional models was developed for use in combination with BEM or actuator/Navier-Stokes computations. A simple and efficient technique for determining the angle of attack for flow past a wind turbine rotor

  1. The aerodynamic signature of running spiders.

    Directory of Open Access Journals (Sweden)

    Jérôme Casas

    Full Text Available Many predators display two foraging modes, an ambush strategy and a cruising mode. These foraging strategies have been classically studied in energetic, biomechanical and ecological terms, without considering the role of signals produced by predators and perceived by prey. Wolf spiders are a typical example; they hunt in leaf litter either using an ambush strategy or by moving at high speed, taking over unwary prey. Air flow upstream of running spiders is a source of information for escaping prey, such as crickets and cockroaches. However, air displacement by running arthropods has not been previously examined. Here we show, using digital particle image velocimetry, that running spiders are highly conspicuous aerodynamically, due to substantial air displacement detectable up to several centimetres in front of them. This study explains the bimodal distribution of spider's foraging modes in terms of sensory ecology and is consistent with the escape distances and speeds of cricket prey. These findings may be relevant to the large and diverse array of arthropod prey-predator interactions in leaf litter.

  2. Kinematics and Aerodynamics of Backward Flying Dragonflies

    Science.gov (United States)

    Bode-Oke, Ayodeji; Zeyghami, Samane; Dong, Haibo

    2015-11-01

    Highly maneuverable insects such as dragonflies have a wide range of flight capabilities; precise hovering, fast body reorientations, sideways flight and backward takeoff are only a few to mention. In this research, we closely examined the kinematics as well as aerodynamics of backward takeoff in dragonflies and compared them to those of forward takeoff. High speed videography and accurate 3D surface reconstruction techniques were employed to extract details of the wing and body motions as well as deformations during both flight modes. While the velocities of both forward and backward flights were similar, the body orientation as well as the wing kinematics showed large differences. Our results indicate that by tilting the stroke plane angle of the wings as well as changing the orientation of the body relative to the flight path, dragonflies control the direction of the flight like a helicopter. In addition, our detailed analysis of the flow in these flights shows important differences in the wake capture phenomena among these flight modes. This work is supported by NSF CBET-1313217.

  3. Measured Aerodynamic Interaction of Two Tiltrotors

    Science.gov (United States)

    Yamauchi, Gloria K.; Wadcock, Alan J.; Derby, Michael R.

    2003-01-01

    The aerodynamic interaction of two model tilrotors in helicopter-mode formation flight is investigated. Three cenarios representing tandem level flight, tandem operations near the ground, and a single tiltrotor operating above thc ground for varying winds are examined. The effect of aircraft separation distance on the thrust and rolling moment of the trailing aircraft with and without the presence of a ground plane are quantified. Without a ground plane, the downwind aircraft experiences a peak rolling moment when the right (left) roto- of the upwind aircraft is laterally aligned with the left (right) rotor of the downwind aircraft. The presence of the ground plane causes the peak rolling moment on the downwind aircraft to occur when the upwind aircraft is further outboard of the downwind aircraft. Ground plane surface flow visualization images obtained using rufts and oil are used to understand mutual interaction between the two aircraft. These data provide guidance in determining tiltrotor flight formations which minimize disturbance to the trailing aircraft.

  4. Hypersonic Inflatable Aerodynamic Decelerator Ground Test Development

    Science.gov (United States)

    Del Corso, Jospeh A.; Hughes, Stephen; Cheatwood, Neil; Johnson, Keith; Calomino, Anthony

    2015-01-01

    Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology readiness levels have been incrementally matured by NASA over the last thirteen years, with most recent support from NASA's Space Technology Mission Directorate (STMD) Game Changing Development Program (GCDP). Recently STMD GCDP has authorized funding and support through fiscal year 2015 (FY15) for continued HIAD ground developments which support a Mars Entry, Descent, and Landing (EDL) study. The Mars study will assess the viability of various EDL architectures to enable a Mars human architecture pathfinder mission planned for mid-2020. At its conclusion in November 2014, NASA's first HIAD ground development effort had demonstrated success with fabricating a 50 W/cm2 modular thermal protection system, a 400 C capable inflatable structure, a 10-meter scale aeroshell manufacturing capability, together with calibrated thermal and structural models. Despite the unquestionable success of the first HIAD ground development effort, it was recognized that additional investment was needed in order to realize the full potential of the HIAD technology capability to enable future flight opportunities. The second HIAD ground development effort will focus on extending performance capability in key technology areas that include thermal protection system, lifting-body structures, inflation systems, flight control, stage transitions, and 15-meter aeroshell scalability. This paper presents an overview of the accomplishments under the baseline HIAD development effort and current plans for a follow-on development effort focused on extending those critical technologies needed to enable a Mars Pathfinder mission.

  5. Unsteady Vibration Aerodynamic Modeling and Evaluation of Dynamic Derivatives Using Computational Fluid Dynamics

    Directory of Open Access Journals (Sweden)

    Xu Liu

    2015-01-01

    Full Text Available Unsteady aerodynamic system modeling is widely used to solve the dynamic stability problems encountering aircraft design. In this paper, single degree-of-freedom (SDF vibration model and forced simple harmonic motion (SHM model for dynamic derivative prediction are developed on the basis of modified Etkin model. In the light of the characteristics of SDF time domain solution, the free vibration identification methods for dynamic stability parameters are extended and applied to the time domain numerical simulation of blunted cone calibration model examples. The dynamic stability parameters by numerical identification are no more than 0.15% deviated from those by experimental simulation, confirming the correctness of SDF vibration model. The acceleration derivatives, rotary derivatives, and combination derivatives of Army-Navy Spinner Rocket are numerically identified by using unsteady N-S equation and solving different SHV patterns. Comparison with the experimental result of Army Ballistic Research Laboratories confirmed the correctness of the SHV model and dynamic derivative identification. The calculation result of forced SHM is better than that by the slender body theory of engineering approximation. SDF vibration model and SHM model for dynamic stability parameters provide a solution to the dynamic stability problem encountering aircraft design.

  6. Rotational accelerations stabilize leading edge vortices on revolving fly wings

    NARCIS (Netherlands)

    Lentink, D.; Dickinson, M.H.

    2009-01-01

    The aerodynamic performance of hovering insects is largely explained by the presence of a stably attached leading edge vortex (LEV) on top of their wings. Although LEVs have been visualized on real, physically modeled, and simulated insects, the physical mechanisms responsible for their stability ar

  7. Aeroelastic Vibrations and Stability in Cyclic Symmetric Domains

    Directory of Open Access Journals (Sweden)

    Bernard Lalanne

    2000-01-01

    wing. In this way, aerodynamic forces may be obtained as general as required, depending on successive time derivatives of degrees of freedom in addition to themselves. Finally, some special cases are given and stability is studied for a cyclic periodic blade assembly, even when mistuning between sectors can occur.

  8. Closed-Loop Flow Control of the Coupled Wake Dynamics and Aerodynamic Loads of a Freely-Pivoting 3-DOF Bluff Body

    Science.gov (United States)

    Lambert, T.; Vukasinovic, B.; Glezer, A.

    2016-11-01

    The motion of an axisymmetric bluff body model that is free to pivot in pitch, yaw, and roll in a uniform stream in response to flow-induced aerodynamic loads is controlled in wind tunnel experiments using fluidic actuation. The model is attached to an upstream, wire-supported short streamwise sting through a low-friction hinge, and each of the support wires is individually-controlled by a servo actuator through an in-line load cell. The aerodynamic loads on the body, and thereby its motion, are controlled through fluidic modification of its aerodynamic coupling to its near wake using four independent aft mounted synthetic jet actuators that effect azimuthally-segmented flow attachment over the model's tail end. The effects of actuation-induced, transitory changes in the model's aerodynamic loads are measured by its motion response using motion tracking, while the coupled evolution of the near-wake is captured by high-speed stereo PIV. Flow control authority is demonstrated by feedback-controlled manipulation of the model's dynamic response, and dynamic mode decomposition (DMD) of the wake is used to characterize changes in the wake structure and stability. It is shown that this flow control approach can modify the stability and damping of the model's motion (e.g., suppression or amplification of its natural oscillations), and impose desired directional attitude. Supported by the ARO.

  9. Development of Pneumatic Aerodynamic Devices to Improve the Performance, Economics, and Safety of Heavy Vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Robert J. Englar

    2000-06-19

    Under contract to the DOE Office of Heavy Vehicle Technologies, the Georgia Tech Research Institute (GTRI) is developing and evaluating pneumatic (blown) aerodynamic devices to improve the performance, economics, stability and safety of operation of Heavy Vehicles. The objective of this program is to apply the pneumatic aerodynamic aircraft technology previously developed and flight-tested by GTRI personnel to the design of an efficient blown tractor-trailer configuration. Recent experimental results obtained by GTRI using blowing have shown drag reductions of 35% on a streamlined automobile wind-tunnel model. Also measured were lift or down-load increases of 100-150% and the ability to control aerodynamic moments about all 3 axes without any moving control surfaces. Similar drag reductions yielded by blowing on bluff afterbody trailers in current US trucking fleet operations are anticipated to reduce yearly fuel consumption by more than 1.2 billion gallons, while even further reduction is possible using pneumatic lift to reduce tire rolling resistance. Conversely, increased drag and down force generated instantaneously by blowing can greatly increase braking characteristics and control in wet/icy weather due to effective ''weight'' increases on the tires. Safety is also enhanced by controlling side loads and moments caused on these Heavy Vehicles by winds, gusts and other vehicles passing. This may also help to eliminate the jack-knifing problem if caused by extreme wind side loads on the trailer. Lastly, reduction of the turbulent wake behind the trailer can reduce splash and spray patterns and rough air being experienced by following vehicles. To be presented by GTRI in this paper will be results developed during the early portion of this effort, including a preliminary systems study, CFD prediction of the blown flowfields, and design of the baseline conventional tractor-trailer model and the pneumatic wind-tunnel model.

  10. Comparison of aerodynamic characteristics of pentagonal and hexagonal shaped bridge decks

    Science.gov (United States)

    Haque, Md. Naimul; Katsuchi, Hiroshi; Yamada, Hitoshi; Nishio, Mayuko

    2016-07-01

    Aerodynamics of the long-span bridge deck should be well understood for an efficient design of the bridge system. For practical bridges various deck shapes are being recommended and adopted, yet not all of their aerodynamic behaviors are well interpreted. In the present study, a numerical investigation was carried out to explore the aerodynamic characteristics of pentagonal and hexagonal shaped bridge decks. A relative comparison of steady state aerodynamic responses was made and the flow field was critically analyzed for better understanding the aerodynamic responses. It was found that the hexagonal shaped bridge deck has better aerodynamic characteristics as compared to the pentagonal shaped bridge deck.

  11. Aerodynamics support of research instrument development

    Science.gov (United States)

    Miller, L. Scott

    1990-01-01

    A new velocimetry system is currently being developed at NASA LaRC. The device, known as a Doppler global velocimeter (DGV), can record three velocity components within a plane simultaneously and in near real time. To make measurements the DGV, like many other velocimetry systems, relies on the scattering of light from numerous small particles in a flow field. The particles or seeds are illuminated by a sheet of laser light and viewed by two CCD cameras. The scattered light from the particles will have a frequency which is a function of the source laser light frequency, the viewing angle, and most importantly the seed velocities. By determining the scattered light intensity the velocity can be measured at all points within the light sheet simultaneously. Upon completion of DGV component construction and initial check out a series of tests in the Basic Aerodynamic Research (wind) Tunnel (BART) are scheduled to verify instrument operation and accuracy. If the results are satisfactory, application of the DGV to flight measurements on the F-18 High Alpha Research Vehicle (HARV) are planned. The DGV verification test in the BART facility will utilize a 75 degree swept delta wing model. A major task undertaken this summer included evaluation of previous results for this model. A specific series of tests matching exactly the previous tests and exploring new DGV capabilities were developed and suggested. Another task undertaken was to study DGV system installation possibilities in the F-18 HARV aircraft. In addition, a simple seeding system modification was developed and utilized to make Particle Imaging Velocimetry (PIV) measurements in the BART facility.

  12. Aerodynamic modelling and optimization of axial fans

    Energy Technology Data Exchange (ETDEWEB)

    Noertoft Soerensen, Dan

    1998-01-01

    A numerically efficient mathematical model for the aerodynamics of low speed axial fans of the arbitrary vortex flow type has been developed. The model is based on a blade-element principle, whereby the rotor is divided into a number of annular stream tubes. For each of these stream tubes relations for velocity, pressure and radial position are derived from the conservation laws for mass, tangential momentum and energy. The equations are solved using the Newton-Raphson methods, and solutions converged to machine accuracy are found at small computing costs. The model has been validated against published measurements on various fan configurations, comprising two rotor-only fan stages, a counter-rotating fan unit and a stator-rotor stator stage. Comparisons of local and integrated properties show that the computed results agree well with the measurements. Optimizations have been performed to maximize the mean value of fan efficiency in a design interval of flow rates, thus designing a fan which operates well over a range of different flow conditions. The optimization scheme was used to investigate the dependence of maximum efficiency on 1: the number of blades, 2: the width of the design interval and 3: the hub radius. The degree of freedom in the choice of design variable and constraints, combined with the design interval concept, provides a valuable design-tool for axial fans. To further investigate the use of design optimization, a model for the vortex shedding noise from the trailing edge of the blades has been incorporated into the optimization scheme. The noise emission from the blades was minimized in a flow rate design point. Optimizations were performed to investigate the dependence of the noise on 1: the number of blades, 2: a constraint imposed on efficiency and 3: the hub radius. The investigations showed, that a significant reduction of noise could be achieved, at the expense of a small reduction in fan efficiency. (EG) 66 refs.

  13. Application Program Interface for the Orion Aerodynamics Database

    Science.gov (United States)

    Robinson, Philip E.; Thompson, James

    2013-01-01

    The Application Programming Interface (API) for the Crew Exploration Vehicle (CEV) Aerodynamic Database has been developed to provide the developers of software an easily implemented, fully self-contained method of accessing the CEV Aerodynamic Database for use in their analysis and simulation tools. The API is programmed in C and provides a series of functions to interact with the database, such as initialization, selecting various options, and calculating the aerodynamic data. No special functions (file read/write, table lookup) are required on the host system other than those included with a standard ANSI C installation. It reads one or more files of aero data tables. Previous releases of aerodynamic databases for space vehicles have only included data tables and a document of the algorithm and equations to combine them for the total aerodynamic forces and moments. This process required each software tool to have a unique implementation of the database code. Errors or omissions in the documentation, or errors in the implementation, led to a lengthy and burdensome process of having to debug each instance of the code. Additionally, input file formats differ for each space vehicle simulation tool, requiring the aero database tables to be reformatted to meet the tool s input file structure requirements. Finally, the capabilities for built-in table lookup routines vary for each simulation tool. Implementation of a new database may require an update to and verification of the table lookup routines. This may be required if the number of dimensions of a data table exceeds the capability of the simulation tools built-in lookup routines. A single software solution was created to provide an aerodynamics software model that could be integrated into other simulation and analysis tools. The highly complex Orion aerodynamics model can then be quickly included in a wide variety of tools. The API code is written in ANSI C for ease of portability to a wide variety of systems. The

  14. Aerodynamic performances of cruise missile flying above local terrain

    Science.gov (United States)

    Ahmad, A.; Saad, M. R.; Che Idris, A.; Rahman, M. R. A.; Sujipto, S.

    2016-10-01

    Cruise missile can be classified as a smart bomb and also Unmanned Aerial Vehicle (UAV) due to its ability to move and manoeuvre by itself without a pilot. Cruise missile flies in constant velocity in cruising stage. Malaysia is one of the consumers of cruise missiles that are imported from other nations, which can have distinct geographic factors including their local terrains compared to Malaysia. Some of the aerodynamic performances of missile such as drag and lift coefficients can be affected by the local geographic conditions in Malaysia, which is different from the origin nation. Therefore, a detailed study must be done to get aerodynamic performance of cruise missiles that operate in Malaysia. The effect of aerodynamic angles such as angle of attack and side slip can be used to investigate the aerodynamic performances of cruise missile. Hence, subsonic wind tunnel testings were conducted to obtain the aerodynamic performances of the missile at various angle of attack and sideslip angles. Smoke visualization was also performed to visualize the behaviour of flow separation. The optimum angle of attack found was at α=21° and side slip, β=10° for optimum pitching and yawing motion of cruise missile.

  15. System Identification and POD Method Applied to Unsteady Aerodynamics

    Science.gov (United States)

    Tang, Deman; Kholodar, Denis; Juang, Jer-Nan; Dowell, Earl H.

    2001-01-01

    The representation of unsteady aerodynamic flow fields in terms of global aerodynamic modes has proven to be a useful method for reducing the size of the aerodynamic model over those representations that use local variables at discrete grid points in the flow field. Eigenmodes and Proper Orthogonal Decomposition (POD) modes have been used for this purpose with good effect. This suggests that system identification models may also be used to represent the aerodynamic flow field. Implicit in the use of a systems identification technique is the notion that a relative small state space model can be useful in describing a dynamical system. The POD model is first used to show that indeed a reduced order model can be obtained from a much larger numerical aerodynamical model (the vortex lattice method is used for illustrative purposes) and the results from the POD and the system identification methods are then compared. For the example considered, the two methods are shown to give comparable results in terms of accuracy and reduced model size. The advantages and limitations of each approach are briefly discussed. Both appear promising and complementary in their characteristics.

  16. 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.

  17. Transition study of 3D aerodynamic configures using improved transport equations modeling

    Institute of Scientific and Technical Information of China (English)

    Xu Jiakuan; Bai Junqiang; Zhang Yang; Qiao Lei

    2016-01-01

    As boundary layer transition plays an important role in aerodynamic drag prediction, the proposal and study of transition prediction methods simulating the complex flow phenomena are prerequisite for aerodynamic design. In this paper, with the application of the linear stability theory based on amplification factor transport transition equations on the two-equation shear stress transport (SST) eddy-viscosity model, a new method, the SST-NTS-NCF model, is yielded. The new amplification factor transport equation for the crossflow instability induced transition is proposed to add to the NTS equation proposed by Coder, which simulates Tollmien–Schlichting wave tran-sition. The turbulent kinetic energy equation is modified by introducing a new source term that sim-ulates the transition process without the intermittency factor equation. Finally, coupled with these two amplification factor transport equations and SST turbulence model, a four-equation transition turbulence model is built. Comparisons between predictions using the new model and wind-tunnel experiments of NACA64(2)A015, NLF(2)-0415 and ONERA-D infinite swept wing and ONERA-M6 swept wing validate the predictive quality of the new SST-NTS-NCF model.

  18. Aerodynamics of the advanced launch system (ALS) propulsion and avionics (P/A) module

    Science.gov (United States)

    Ferguson, Stan; Savage, Dick

    1992-01-01

    This paper discusses the design and testing of candidate Advanced Launch System (ALS) Propulsion and Avionics (P/A) Module configurations. The P/A Module is a key element of future launch systems because it is essential to the recovery and reuse of high-value propulsion and avionics hardware. The ALS approach involves landing of first stage (booster) and/or second stage (core) P/A modules near the launch site to minimize logistics and refurbishment cost. The key issue addressed herein is the aerodynamic design of the P/A module, including the stability characteristics and the lift-to-drag (L/D) performance required to achieve the necessary landing guidance accuracy. The reference P/A module configuration was found to be statically stable for the desired flight regime, to provide adequate L/D for targeting, and to have effective modulation of the L/D performance using a body flap. The hypersonic aerodynamic trends for nose corner radius, boattail angle and body flap deflections were consistent with pretest predictions. However, the levels for the L/D and axial force for hypersonic Mach numbers were overpredicted by impact theories.

  19. Transition study of 3D aerodynamic configures using improved transport equations modeling

    Directory of Open Access Journals (Sweden)

    Xu Jiakuan

    2016-08-01

    Full Text Available As boundary layer transition plays an important role in aerodynamic drag prediction, the proposal and study of transition prediction methods simulating the complex flow phenomena are prerequisite for aerodynamic design. In this paper, with the application of the linear stability theory based on amplification factor transport transition equations on the two-equation shear stress transport (SST eddy-viscosity model, a new method, the SST-NTS-NCF model, is yielded. The new amplification factor transport equation for the crossflow instability induced transition is proposed to add to the NTS equation proposed by Coder, which simulates Tollmien–Schlichting wave transition. The turbulent kinetic energy equation is modified by introducing a new source term that simulates the transition process without the intermittency factor equation. Finally, coupled with these two amplification factor transport equations and SST turbulence model, a four-equation transition turbulence model is built. Comparisons between predictions using the new model and wind-tunnel experiments of NACA64(2A015, NLF(2-0415 and ONERA-D infinite swept wing and ONERA-M6 swept wing validate the predictive quality of the new SST-NTS-NCF model.

  20. Space-Time Fluid-Structure Interaction Computation of Flapping-Wing Aerodynamics

    Science.gov (United States)

    Kostov, Nikolay M.

    We present a sequentially-coupled space-time (ST) computational fluid-structure interaction (FSI) analysis of flapping-wing aerodynamics of a micro aerial vehicle (MAV). The wing motion and deformation data, whether prescribed fully or partially, is from an actual locust, extracted from high-speed, multi-camera video recordings of the locust in a wind tunnel. The core computational FSI technology is based on the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) formulation. This is supplemented with using NURBS basis functions in temporal representation of the wing and mesh motion, and in remeshing. Here we use the version of the DSD/SST formulation derived in conjunction with the variational multiscale (VMS) method, and this version is called "DSD/SST-VMST." The structural mechanics computations are based on the Kirchhoff-Love shell model. The sequential-coupling technique is applicable to some classes of FSI problems, especially those with temporally-periodic behavior. We show that it performs well in FSI computations of the flapping-wing aerodynamics we consider here. In addition to the straight-flight case, we analyze cases where the MAV body has rolling, pitching, or rolling and pitching motion. We study how all these influence the lift and thrust.

  1. Investigation of longitudinal aerodynamic parameters identification method for fly-by-wire passenger airliners

    Institute of Scientific and Technical Information of China (English)

    Wu Zhao; Wang Lixin; Xu Zijian; Tan Xiangsheng

    2013-01-01

    The flight control system of a fly-by-wire (FBW) passenger airliner with a complex frame-work and high feedback gain augmentation would change the original characteristic of a loaded sig-nal and suppress the excitation of an airplane’s pertinent motion modes. Taking a research example of an FBW passenger airliner model with longitudinal relaxed-static-stability, a new method of signal type selection and signal parameter design is proposed, through analysis of signal energy distribution and plane body’s frequency response. According to CCAR60--the Appraisal and Use Regulation of Flight Simulator Device, the simulation validation of the FBW passenger airliner’s longitudinal aerodynamic parameters identification is put forward. The validation result indicates that the designed signal could excite the longitudinal motion mode of the FBW passenger airliner adequately and the multiparameter comparison in simulation meets the objective test request of CCAR60. Meanwhile, the relative errors of aerodynamic parameters are less than 10%.

  2. Active aerodynamic stabilisation of long suspension bridges

    DEFF Research Database (Denmark)

    Nissen, Henrik Ditlev; Sørensen, Paul Haase; Jannerup, Ole Erik

    2004-01-01

    The paper describes the addition of actively controlled appendages (flaps) attached along the length of the bridge deck to dampen wind-induced oscillations in long suppension bridges. A novel approach using control systems methods for the analysis of dynamic stability is presented. In order to ma...

  3. Survey of Army/NASA rotorcraft aeroelastic stability research

    Science.gov (United States)

    Ormiston, Robert A.; Warmbrodt, William G.; Hodges, Dewey H.; Peters, David A.

    1988-01-01

    Theoretical and experimental developments in the aeroelastic and aeromechanical stability of helicopters and tilt-rotor aircraft are addressed. Included are the underlying nonlinear structural mechanics of slender rotating beams, necessary for accurate modeling of elastic cantilever rotor blades, and the development of dynamic inflow, an unsteady aerodynamic theory for low frequency aeroelastic stability applications. Analytical treatment of isolated rotor stability in hover and forward flight, coupled rotor-fuselage stability are considered. Results of parametric investigations of system behavior are presented, and correlations between theoretical results and experimental data from small- and large-scale wind tunnel and flight testing are discussed.

  4. Aerodynamic Interactions Between Contralateral Wings and Between Wings and Body of a Model Insect at Hovering and Small Speed Motions

    Institute of Scientific and Technical Information of China (English)

    LIANG Bin; SUN Mao

    2011-01-01

    In this paper,we study the aerodynamic interactions between the contralateral wings and between the body and wings of a model insect,when the insect is hovering and has various translational and rotational motions,using the method numerically solving the Navier-Stokes equations over moving overset grids.The aerodynamic interactional effects are identified by comparing the results of a complete model insect,the corresponding wing pair,single wing and body without the wings.Horizontal,vertical and lateral translations and roll,pitch and yaw rotations at small speeds are considered.The results indicate that for the motions considered,both the interaction between the contralateral wings and the interaction between the body and wings are weak.The changes in the forces and moments of a wing due to the contralateral wing interaction,of the wings due to the presence of the body,and of the body due to the presence of the wings are generally less than 4.5%.Results show that aerodynamic forces of wings and body can be measured or computed separately in the analysis of flight stability and control of hovering insects.

  5. Does an active adjustment of aerodynamic drag make sense?

    Science.gov (United States)

    Maciejewski, Marek

    2016-09-01

    The article concerns evaluation of the possible impact of the gap between the tractor and semitrailer on the aerodynamic drag coefficient. The aim here is not to adjust this distance depending on the geometrical shape of the tractor and trailer, but depending solely on the speed of articulated vehicle. All the tests have form of numerical simulations. The method of simulation is briefly explained in the article. It considers various issues such as the range and objects of tests as well as the test conditions. The initial (pre-adaptive) and final (after adaptation process) computational meshes have been presented as illustrations. Some of the results have been presented in the form of run chart showing the change of value of aerodynamic drag coefficients in time, for different geometric configurations defined by a clearance gap between the tractor and semitrailer. The basis for a detailed analysis and conclusions were the averaged (in time) aerodynamic drag coefficients as a function of the clearance gap.

  6. Improved blade element momentum theory for wind turbine aerodynamic computations

    DEFF Research Database (Denmark)

    Sun, Zhenye; Chen, Jin; Shen, Wen Zhong;

    2016-01-01

    Blade element momentum (BEM) theory is widely used in aerodynamic performance predictions and design applications for wind turbines. However, the classic BEM method is not quite accurate which often tends to under-predict the aerodynamic forces near root and over-predict its performance near tip....... The reliability of the aerodynamic calculations and design optimizations is greatly reduced due to this problem. To improve the momentum theory, in this paper the influence of pressure drop due to wake rotation and the effect of radial velocity at the rotor disc in the momentum theory are considered. Thus...... the axial induction factor in far downstream is not simply twice of the induction factor at disc. To calculate the performance of wind turbine rotors, the improved momentum theory is considered together with both Glauert's tip correction and Shen's tip correction. Numerical tests have been performed...

  7. AERODYNAMIC AND BLADING DESIGN OF MULTISTAGE AXIAL FLOW COMPRESSORS

    Science.gov (United States)

    Crouse, J. E.

    1994-01-01

    The axial-flow compressor is used for aircraft engines because it has distinct configuration and performance advantages over other compressor types. However, good potential performance is not easily obtained. The designer must be able to model the actual flows well enough to adequately predict aerodynamic performance. This computer program has been developed for computing the aerodynamic design of a multistage axial-flow compressor and, if desired, the associated blading geometry input for internal flow analysis. The aerodynamic solution gives velocity diagrams on selected streamlines of revolution at the blade row edges. The program yields aerodynamic and blading design results that can be directly used by flow and mechanical analysis codes. Two such codes are TSONIC, a blade-to-blade channel flow analysis code (COSMIC program LEW-10977), and MERIDL, a more detailed hub-to-shroud flow analysis code (COSMIC program LEW-12966). The aerodynamic and blading design program can reduce the time and effort required to obtain acceptable multistage axial-flow compressor configurations by generating good initial solutions and by being compatible with available analysis codes. The aerodynamic solution assumes steady, axisymmetric flow so that the problem is reduced to solving the two-dimensional flow field in the meridional plane. The streamline curvature method is used for the iterative aerodynamic solution at stations outside of the blade rows. If a blade design is desired, the blade elements are defined and stacked within the aerodynamic solution iteration. The blade element inlet and outlet angles are established by empirical incidence and deviation angles to the relative flow angles of the velocity diagrams. The blade element centerline is composed of two segments tangentially joined at a transition point. The local blade angle variation of each element can be specified as a fourth-degree polynomial function of path distance. Blade element thickness can also be specified

  8. Aerodynamic Jump: A Short Range View for Long Rod Projectiles

    Directory of Open Access Journals (Sweden)

    Mark Bundy

    2001-01-01

    Full Text Available It is shown that aerodynamic jump for a nonspinning kinetic energy penetrator is not – as conventional definitions may infer – a discontinuous change in the direction of motion at the origin of free flight, nor is it the converse, a cumulative redirection over a domain of infinite extent. Rather, with the aid of an alternative kinematical definition, it is shown that aerodynamic jump for such a projectile is a localized redirection of the center-of-gravity motion, caused by the force of lift due to yaw over the relatively short region from entry into free flight until the yaw reaches its first maximum. A rigorous proof of this statement is provided, but the primary objective of this paper is to provide answers to the questions: what is aerodynamic jump, what does it mean, and what aspects of the flight trajectory does it refer to, or account for.

  9. Effects of ice accretion on the aerodynamics of bridge cables

    DEFF Research Database (Denmark)

    Demartino, C.; Koss, Holger; Georgakis, Christos T.;

    2015-01-01

    Undesirable wind induced vibrations of bridge cables can occur when atmospheric conditions are such to generate ice accretion. This paper contains the results of an extensive investigation of the effects of ice accretion due to in-cloud icing, on the aerodynamic characteristics of bridge hangers...... and stay cables. The aim of this paper is twofold; first, it was investigated the ice accretion process and the final shape of the ice accreted; then the aerodynamics of the ice accreted bridge cables was characterized, and related to the ice shape. Different climatic conditions, i.e. combinations...... of the ice accretions is given in the paper. Only for the bridge hanger case, a short description of the evolution of the ice accretions is given. The aerodynamic force coefficients were then measured with varying yaw angle, angle of attack and wind speed, and are presented and discussed in the paper...

  10. THERMAL AND AERODYNAMIC PERFORMANCES OF THE SUPERSONIC MOTION

    Directory of Open Access Journals (Sweden)

    Dejan P Ninković

    2010-01-01

    Full Text Available Generally speaking, Mach number of 4 can be taken as a boundary value for transition from conditions for supersonic, into the area of hypersonic flow, distinguishing two areas: area of supersonic in which the effects of the aerodynamic heating can be neglected and the area of hypersonic, in which the thermal effects become dominant. This paper presents the effects in static and dynamic areas, as well as presentation of G.R.O.M. software for determination of the values of aerodynamic derivatives, which was developed on the basis of linearized theory of supersonic flow. Validation of developed software was carried out through different types of testing, proving its usefulness for engineering practice in the area of supersonic wing aerodynamic loading calculations, even at high Mach numbers, with dominant thermal effects.

  11. Atmospheric testing of wind turbine trailing edge aerodynamic brakes

    Energy Technology Data Exchange (ETDEWEB)

    Miller, L.S. [Wichita State Univ., KS (United States); Migliore, P.G. [National Renewable Energy Lab., Golden, CO (United States); Quandt, G.A.

    1997-12-31

    An experimental investigation was conducted using an instrumented horizontal-axis wind turbine that incorporated variable span trailing-edge aerodynamic brakes. A primary goal was to directly compare study results with (infinite-span) wind tunnel data and to provide information on how to account for device span effects during turbine design or analysis. Comprehensive measurements were utilized to define effective changes in the aerodynamic coefficients, as a function of angle of attack and control deflection, for three device spans and configurations. Differences in the lift and drag behavior are most pronounced near stall and for device spans of less than 15%. Drag performance is affected only minimally (<70%) for 15% or larger span devices. Interestingly, aerodynamic controls with characteristic vents or openings appear most affected by span reductions and three-dimensional flow.

  12. Investigation of aerodynamic braking devices for wind turbine applications

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, D.A. [R. Lynette & amp; Associates, Seattle, WA (United States)

    1997-04-01

    This report documents the selection and preliminary design of a new aerodynamic braking system for use on the stall-regulated AWT-26/27 wind turbines. The goal was to identify and design a configuration that offered improvements over the existing tip brake used by Advanced Wind Turbines, Inc. (AWT). Although the design objectives and approach of this report are specific to aerodynamic braking of AWT-26/27 turbines, many of the issues addressed in this work are applicable to a wider class of turbines. The performance trends and design choices presented in this report should be of general use to wind turbine designers who are considering alternative aerodynamic braking methods. A literature search was combined with preliminary work on device sizing, loads and mechanical design. Candidate configurations were assessed on their potential for benefits in the areas of cost, weight, aerodynamic noise, reliability and performance under icing conditions. As a result, two configurations were identified for further study: the {open_quotes}spoiler-flap{close_quotes} and the {open_quotes}flip-tip.{close_quotes} Wind tunnel experiments were conducted at Wichita State University to evaluate the performance of the candidate aerodynamic brakes on an airfoil section representative of the AWT-26/27 blades. The wind tunnel data were used to predict the braking effectiveness and deployment characteristics of the candidate devices for a wide range of design parameters. The evaluation was iterative, with mechanical design and structural analysis being conducted in parallel with the braking performance studies. The preliminary estimate of the spoiler-flap system cost was $150 less than the production AWT-26/27 tip vanes. This represents a reduction of approximately 5 % in the cost of the aerodynamic braking system. In view of the preliminary nature of the design, it would be prudent to plan for contingencies in both cost and weight.

  13. Hybrid Vortex Method for the Aerodynamic Analysis of Wind Turbine

    Directory of Open Access Journals (Sweden)

    Hao Hu

    2015-01-01

    Full Text Available The hybrid vortex method, in which vortex panel method is combined with the viscous-vortex particle method (HPVP, was established to model the wind turbine aerodynamic and relevant numerical procedure program was developed to solve flow equations. The panel method was used to calculate the blade surface vortex sheets and the vortex particle method was employed to simulate the blade wake vortices. As a result of numerical calculations on the flow over a wind turbine, the HPVP method shows significant advantages in accuracy and less computation resource consuming. The validation of the aerodynamic parameters against Phase VI wind turbine experimental data is performed, which shows reasonable agreement.

  14. Research on Aerodynamic Noise Reduction for High-Speed Trains

    OpenAIRE

    Yadong Zhang; Jiye Zhang; Tian Li; Liang Zhang; Weihua Zhang

    2016-01-01

    A broadband noise source model based on Lighthill’s acoustic theory was used to perform numerical simulations of the aerodynamic noise sources for a high-speed train. The near-field unsteady flow around a high-speed train was analysed based on a delayed detached-eddy simulation (DDES) using the finite volume method with high-order difference schemes. The far-field aerodynamic noise from a high-speed train was predicted using a computational fluid dynamics (CFD)/Ffowcs Williams-Hawkings (FW-H)...

  15. Efficient optimization of integrated aerodynamic-structural design

    Science.gov (United States)

    Haftka, R. T.; Grossman, B.; Eppard, W. M.; Kao, P. J.; Polen, D. M.

    1989-01-01

    Techniques for reducing the computational complexity of multidisciplinary design optimization (DO) of aerodynamic structures are described and demonstrated. The basic principles of aerodynamic and structural DO are reviewed; the formulation of the combined DO problem is outlined; and particular attention is given to (1) the application of perturbation methods to cross-sensitivity computations and (2) numerical approximation procedures. Trial DOs of a simple sailplane design are presented in tables and graphs and discussed in detail. The IBM 3090 CPU time for the entire integrated DO was reduced from an estimated 10 h to about 6 min.

  16. Aerodynamic Noise An Introduction for Physicists and Engineers

    CERN Document Server

    Bose, Tarit

    2013-01-01

    Aerodynamic Noise extensively covers the theoretical basis and mathematical modeling of sound, especially the undesirable sounds produced by aircraft. This noise could come from an aircraft’s engine—propellers, fans, combustion chamber, jets—or the vehicle itself—external surfaces—or from sonic booms. The majority of the sound produced is due to the motion of air and its interaction with solid boundaries, and this is the main discussion of the book. With problem sets at the end of each chapter, Aerodynamic Noise is ideal for graduate students of mechanical and aerospace engineering. It may also be useful for designers of cars, trains, and wind turbines.

  17. Aerodynamic Jump: A Short Range View for Long Rod Projectiles

    OpenAIRE

    Mark Bundy

    2001-01-01

    It is shown that aerodynamic jump for a nonspinning kinetic energy penetrator is not – as conventional definitions may infer – a discontinuous change in the direction of motion at the origin of free flight, nor is it the converse, a cumulative redirection over a domain of infinite extent. Rather, with the aid of an alternative kinematical definition, it is shown that aerodynamic jump for such a projectile is a localized redirection of the center-of-gravity motion, caused by the force of lift ...

  18. Analysis of broadband aerodynamic noise from VS45

    Energy Technology Data Exchange (ETDEWEB)

    Dundabin, P. [Renewable Energy Systems Ltd., Glasgow, Scotland (United Kingdom)

    1997-12-31

    This paper describes the analysis of acoustic data taken from the VS45 at Kaiser-Wilhelm-Koog. The aim was to investigate the dependence of aerodynamic noise on tip speed and angle of attack. In particular, the dependence of noise in individual third octave bands on these variable is examined. The analysis is divided into 3 sections: data selection, data checks and analysis of broadband nacelle noise; analysis of broadband aerodynamic noise and its sensitivity to tip speed and angle of attack. (LN)

  19. An aerodynamic noise propagation model for wind turbines

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Sørensen, Jens Nørkær; Shen, Wen Zhong

    2005-01-01

    A model based on 2-D sound ray theory for aerodynamic noise propagation from wind turbine rotating blades is introduced. The model includes attenuation factors from geometric spreading, sound directivity of source, air absorption, ground deflection and reflection, as well as effects from temperat......A model based on 2-D sound ray theory for aerodynamic noise propagation from wind turbine rotating blades is introduced. The model includes attenuation factors from geometric spreading, sound directivity of source, air absorption, ground deflection and reflection, as well as effects from...

  20. Aerodynamic Optimization of an Over-the-Wing-Nacelle-Mount Configuration

    OpenAIRE

    Daisuke Sasaki; Kazuhiro Nakahashi

    2011-01-01

    An over-the-wing-nacelle-mount airplane configuration is known to prevent the noise propagation from jet engines toward ground. However, the configuration is assumed to have low aerodynamic efficiency due to the aerodynamic interference effect between a wing and a nacelle. In this paper, aerodynamic design optimization is conducted to improve aerodynamic efficiency to be equivalent to conventional under-the-wing-nacelle-mount configuration. The nacelle and wing geometry are modified to achiev...

  1. Experimental Study of Effects of Tail Wings on Submunition Aerodynamic Characteristics

    Institute of Scientific and Technical Information of China (English)

    王海福; 李向荣

    2004-01-01

    Aimed at the needs of deceleration of submunitions dispensed from the ballistic missile, wind tunnel tests were performed on the submunitions with different tail wing sizes at the Mach number range from 0.7 to 3.0 and the angle of attack range from 0° to 14°. Experimental data about the variance of aerodynamic coefficients with the Mach number and angle of attack were obtained systemically. The effects of the tail wing sizes on the drag coefficients and the center of pressure coefficients were discussed. Analyzed results show the arc tail wings designed are beneficial to both the deceleration effect and static stability. These results are significant to the tail wing design and its applications to the submunitions deceleration.

  2. Using Fractional-order Piλ Dμ Controller for Control of Aerodynamic Missile

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bang-chu; ZHU Ji-hong; PAN Shu-shan; WANG Shao-feng

    2006-01-01

    A new type of PID controller is introduced and some properties are given. The novelty of the proposed controller consists in the extension of derivation and integration order from integer to non-integer order. The PIλDμ controller generally has three advantages when compared to the integerl-order controller: the first is that it has more degrees of freedom in the model; the second is that it has a memory in model, the memory insure the history and its impact to present and future, the third is it ensures the stability of missile. This approach provides a more flexible tuning strategy and therefore an easier achieving of control requirements. Flight dynamic model of an aerodynamic missile is taken into account in implementing the PIλDμ controller. Simulation results show that the PIλDμ controller is not sensitive to the changes of control parameters and the system parameters. Also, the controller has more flexible structure and stronger robustness.

  3. Development of an Innovative Algorithm for Aerodynamics-Structure Interaction Using Lattice Boltzmann Method

    Science.gov (United States)

    Mei, Ren-Wei; Shyy, Wei; Yu, Da-Zhi; Luo, Li-Shi; Rudy, David (Technical Monitor)

    2001-01-01

    The lattice Boltzmann equation (LBE) is a kinetic formulation which offers an alternative computational method capable of solving fluid dynamics for various systems. Major advantages of the method are owing to the fact that the solution for the particle distribution functions is explicit, easy to implement, and the algorithm is natural to parallelize. In this final report, we summarize the works accomplished in the past three years. Since most works have been published, the technical details can be found in the literature. Brief summary will be provided in this report. In this project, a second-order accurate treatment of boundary condition in the LBE method is developed for a curved boundary and tested successfully in various 2-D and 3-D configurations. To evaluate the aerodynamic force on a body in the context of LBE method, several force evaluation schemes have been investigated. A simple momentum exchange method is shown to give reliable and accurate values for the force on a body in both 2-D and 3-D cases. Various 3-D LBE models have been assessed in terms of efficiency, accuracy, and robustness. In general, accurate 3-D results can be obtained using LBE methods. The 3-D 19-bit model is found to be the best one among the 15-bit, 19-bit, and 27-bit LBE models. To achieve desired grid resolution and to accommodate the far field boundary conditions in aerodynamics computations, a multi-block LBE method is developed by dividing the flow field into various blocks each having constant lattice spacing. Substantial contribution to the LBE method is also made through the development of a new, generalized lattice Boltzmann equation constructed in the moment space in order to improve the computational stability, detailed theoretical analysis on the stability, dispersion, and dissipation characteristics of the LBE method, and computational studies of high Reynolds number flows with singular gradients. Finally, a finite difference-based lattice Boltzmann method is

  4. Mechanism of unconventional aerodynamic characteristics of an elliptic airfoil

    Directory of Open Access Journals (Sweden)

    Sun Wei

    2015-06-01

    Full Text Available The aerodynamic characteristics of elliptic airfoil are quite different from the case of conventional airfoil for Reynolds number varying from about 104 to 106. In order to reveal the fundamental mechanism, the unsteady flow around a stationary two-dimensional elliptic airfoil with 16% relative thickness has been simulated using unsteady Reynolds-averaged Navier–Stokes equations and the γ-Reθt‾ transition turbulence model at different angles of attack for flow Reynolds number of 5 × 105. The aerodynamic coefficients and the pressure distribution obtained by computation are in good agreement with experimental data, which indicates that the numerical method works well. Through this study, the mechanism of the unconventional aerodynamic characteristics of airfoil is analyzed and discussed based on the computational predictions coupled with the wind tunnel results. It is considered that the boundary layer transition at the leading edge and the unsteady flow separation vortices at the trailing edge are the causes of the case. Furthermore, a valuable insight into the physics of how the flow behavior affects the elliptic airfoil’s aerodynamics is provided.

  5. A New Aerodynamic Data Dispersion Method for Launch Vehicle Design

    Science.gov (United States)

    Pinier, Jeremy T.

    2011-01-01

    A novel method for implementing aerodynamic data dispersion analysis is herein introduced. A general mathematical approach combined with physical modeling tailored to the aerodynamic quantity of interest enables the generation of more realistically relevant dispersed data and, in turn, more reasonable flight simulation results. The method simultaneously allows for the aerodynamic quantities and their derivatives to be dispersed given a set of non-arbitrary constraints, which stresses the controls model in more ways than with the traditional bias up or down of the nominal data within the uncertainty bounds. The adoption and implementation of this new method within the NASA Ares I Crew Launch Vehicle Project has resulted in significant increases in predicted roll control authority, and lowered the induced risks for flight test operations. One direct impact on launch vehicles is a reduced size for auxiliary control systems, and the possibility of an increased payload. This technique has the potential of being applied to problems in multiple areas where nominal data together with uncertainties are used to produce simulations using Monte Carlo type random sampling methods. It is recommended that a tailored physics-based dispersion model be delivered with any aerodynamic product that includes nominal data and uncertainties, in order to make flight simulations more realistic and allow for leaner spacecraft designs.

  6. Reduced order modeling of steady flows subject to aerodynamic constraints

    DEFF Research Database (Denmark)

    Zimmermann, Ralf; Vendl, Alexander; Goertz, Stefan

    2014-01-01

    A novel reduced-order modeling method based on proper orthogonal decomposition for predicting steady, turbulent flows subject to aerodynamic constraints is introduced. Model-order reduction is achieved by replacing the governing equations of computational fluid dynamics with a nonlinear weighted ...

  7. Laryngeal Aerodynamics Associated with Oral Contraceptive Use: Preliminary Findings

    Science.gov (United States)

    Gorham-Rowan, Mary; Fowler, Linda

    2009-01-01

    The purpose of this study was to examine possible differences in laryngeal aerodynamic measures during connected speech associated with oral contraceptive (OC) use. Eight women taking an OC, and eight others not taking an OC, participated in the study. Three trials of syllable /p[subscript alpha] /repetitions were obtained using a…

  8. The effect of aerodynamic parameters on power output of windmills

    Science.gov (United States)

    Wiesner, W.

    1973-01-01

    Aerodynamic results for a study on windpower generation are reported. Windmill power output is presented in terms that are commonly used in rotary wing analysis, namely, power output as a function of drag developed by the windmill. Effect of tip speed ratio, solidity, twist, wind angle, blade setting and airfoil characteristics are given.

  9. Aerodynamic Experiments on DelFly II: Unsteady Lift Enhancement

    NARCIS (Netherlands)

    De Clercq, K.M.E.; De Kat, R.; Remes, B.; Van Oudheusden, B.W.; Bijl, H.

    2009-01-01

    Particle image velocimetry measurements and simultaneous force measurements have been performed on the DelFly II flapping-wing MAV, to investigate the flow-field behavior and the aerodynamic forces generated. For flapping wing motion it is expected that both the clap and peel mechanism and the occur

  10. Quasi-steady state aerodynamics of the cheetah tail

    Science.gov (United States)

    Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily

    2016-01-01

    ABSTRACT During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities. PMID:27412267

  11. Quasi-steady state aerodynamics of the cheetah tail

    Directory of Open Access Journals (Sweden)

    Amir Patel

    2016-08-01

    Full Text Available During high-speed pursuit of prey, the cheetah (Acinonyx jubatus has been observed to swing its tail while manoeuvring (e.g. turning or braking but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities.

  12. Studying surface glow discharge for application in plasma aerodynamics

    Science.gov (United States)

    Tereshonok, D. V.

    2014-02-01

    Surface glow discharge in nitrogen between two infinite planar electrodes occurring on the same plane has been studied in the framework of a diffusion-drift model. Based on the results of numerical simulations, the plasma structure of this discharge is analyzed and the possibility of using it in plasma aerodynamics is considered.

  13. Innovation in Aerodynamic Design Features of Soviet Missiles

    Science.gov (United States)

    Spearman, M. Leroy

    2006-01-01

    Wind tunnel investigations of some tactical and strategic missile systems developed by the former Soviet Union have been included in the basic missile research programs of the NACA/NASA. Studies of the Soviet missiles sometimes revealed innovative design features that resulted in unusual or unexpected aerodynamic characteristics. In some cases these characteristics have been such that the measured performance of the missile exceeds what might have been predicted. In other cases some unusual design features have been found that would alleviate what might otherwise have been a serious aerodynamic problem. In some designs, what has appeared to be a lack of refinement has proven to be a matter of expediency. It is a purpose of this paper to describe some examples of unusual design features of some Soviet missiles and to illustrate the effectiveness of the design features on the aerodynamic behavior of the missile. The paper draws on the experience of the author who for over 60 years was involved in the aerodynamic wind tunnel testing of aircraft and missiles with the NACA/NASA.

  14. 14 CFR 23.371 - Gyroscopic and aerodynamic loads.

    Science.gov (United States)

    2010-01-01

    ... Flight Loads § 23.371 Gyroscopic and aerodynamic loads. (a) Each engine mount and its supporting... engine mount and its supporting structure must meet the requirements of paragraph (a) of this section and.... (c) For airplanes certificated in the commuter category, each engine mount and its...

  15. Aerodynamic Characteristic of the Active Compliant Trailing Edge Concept

    Science.gov (United States)

    Nie, Rui; Qiu, Jinhao; Ji, Hongli; Li, Dawei

    2016-06-01

    This paper introduces a novel Morphing Wing structure known as the Active Compliant Trailing Edge (ACTE). ACTE structures are designed using the concept of “distributed compliance” and wing skins of ACTE are fabricated from high-strength fiberglass composites laminates. Through the relative sliding between upper and lower wing skins which are connected by a linear guide pairs, the wing is able to achieve a large continuous deformation. In order to present an investigation about aerodynamics and noise characteristics of ACTE, a series of 2D airfoil analyses are established. The aerodynamic characteristics between ACTE and conventional deflection airfoil are analyzed and compared, and the impacts of different ACTE structure design parameters on aerodynamic characteristics are discussed. The airfoils mentioned above include two types (NACA0012 and NACA64A005.92). The computing results demonstrate that: compared with the conventional plane flap airfoil, the morphing wing using ACTE structures has the capability to improve aerodynamic characteristic and flow separation characteristic. In order to study the noise level of ACTE, flow field analysis using LES model is done to provide noise source data, and then the FW-H method is used to get the far field noise levels. The simulation results show that: compared with the conventional flap/aileron airfoil, the ACTE configuration is better to suppress the flow separation and lower the overall sound pressure level.

  16. Passive flow control by membrane wings for aerodynamic benefit

    Science.gov (United States)

    Timpe, Amory; Zhang, Zheng; Hubner, James; Ukeiley, Lawrence

    2013-03-01

    The coupling of passive structural response of flexible membranes with the flow over them can significantly alter the aerodynamic characteristic of simple flat-plate wings. The use of flexible wings is common throughout biological flying systems inspiring many engineers to incorporate them into small engineering flying systems. In many of these systems, the motion of the membrane serves to passively alter the flow over the wing potentially resulting in an aerodynamic benefit. In this study, the aerodynamic loads and the flow field for a rigid flat-plate wing are compared to free trailing-edge membrane wings with two different pre-tensions at a chord-based Reynolds number of approximately 50,000. The membrane was silicon rubber with a scalloped free trailing edge. The analysis presented includes load measurements from a sting balance along with velocity fields and membrane deflections from synchronized, time-resolved particle image velocimetry and digital image correlation. The load measurements demonstrate increased aerodynamic efficiency and lift, while the synchronized flow and membrane measurements show how the membrane motion serves to force the flow. This passive flow control introduced by the membranes motion alters the flows development over the wing and into the wake region demonstrating how, at least for lower angles of attack, the membranes motion drives the flow as opposed to the flow driving the membrane motion.

  17. Plasma Aerodynamic Control Effectors for Improved Wind Turbine Performance

    Energy Technology Data Exchange (ETDEWEB)

    Mehul P. Patel; Srikanth Vasudevan; Robert C. Nelson; Thomas C. Corke

    2008-08-01

    Orbital Research Inc is developing an innovative Plasma Aerodynamic Control Effectors (PACE) technology for improved performance of wind turbines. The PACE system is aimed towards the design of "smart" rotor blades to enhance energy capture and reduce aerodynamic loading and noise using flow-control. The PACE system will provide ability to change aerodynamic loads and pitch distribution across the wind turbine blade without any moving surfaces. Additional benefits of the PACE system include reduced blade structure weight and complexity that should translate into a substantially reduced initial cost. During the Phase I program, the ORI-UND Team demonstrated (proof-of-concept) performance improvements on select rotor blade designs using PACE concepts. Control of both 2-D and 3-D flows were demonstrated. An analytical study was conducted to estimate control requirements for the PACE system to maintain control during wind gusts. Finally, independent laboratory experiments were conducted to identify promising dielectric materials for the plasma actuator, and to examine environmental effects (water and dust) on the plasma actuator operation. The proposed PACE system will be capable of capturing additional energy, and reducing aerodynamic loading and noise on wind turbines. Supplementary benefits from the PACE system include reduced blade structure weight and complexity that translates into reduced initial capital costs.

  18. Quasi-steady state aerodynamics of the cheetah tail.

    Science.gov (United States)

    Patel, Amir; Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily

    2016-08-15

    During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities.

  19. Robust D-Stability Controller Design for a Ducted Fan Unmanned Aerial Vehicle

    Directory of Open Access Journals (Sweden)

    Xiao-lu Ren

    2014-01-01

    Full Text Available This paper deals with the aerodynamic modeling of a small ducted fan UAV and the problem of attitude stabilization when the parameter of the vehicle is varied. The main aerodynamic model of the hovering flight UAV is first presented. Then, an attitude control is designed from a linearization of the dynamic model around the hovering flight, which is based on the H∞ output feedback control theory with D-stability. Simulation results show that such method has good robustness to the attitude system. They can meet the requirements of attitude control and verify further the feasibility of such a control strategy.

  20. Ideal Stabilization

    CERN Document Server

    Nesterenko, Mikhail

    2009-01-01

    We define and explore the concept of ideal stabilization. The program is ideally stabilizing if its every state is legitimate. Ideal stabilization allows the specification designer to prescribe with arbitrary degree of precision not only the fault-free program behavior but also its recovery operation. Specifications may or may not mention all possible states. We identify approaches to designing ideal stabilization to both kinds of specifications. For the first kind, we state the necessary condition for an ideally stabilizing solution. On the basis of this condition we prove that there is no ideally stabilizing solution to the leader election problem. We illustrate the utility of the concept by providing examples of well-known programs and proving them ideally stabilizing. Specifically, we prove ideal stabilization of the conflict manager, the alternator, the propagation of information with feedback and the alternating bit protocol.

  1. Aerodynamic Analysis of Multistage Turbomachinery Flows in Support of Aerodynamic Design

    Science.gov (United States)

    Adamczyk, John J.

    1999-01-01

    This paper summarizes the state of 3D CFD based models of the time average flow field within axial flow multistage turbomachines. Emphasis is placed on models which are compatible with the industrial design environment and those models which offer the potential of providing credible results at both design and off-design operating conditions. The need to develop models which are free of aerodynamic input from semi-empirical design systems is stressed. The accuracy of such models is shown to be dependent upon their ability to account for the unsteady flow environment in multistage turbomachinery. The relevant flow physics associated with some of the unsteady flow processes present in axial flow multistage machinery are presented along with procedures which can be used to account for them in 3D CFD simulations. Sample results are presented for both axial flow compressors and axial flow turbines which help to illustrate the enhanced predictive capabilities afforded by including these procedures in 3D CFD simulations. Finally, suggestions are given for future work on the development of time average flow models.

  2. A note on the stability condition for a spinning shell

    Directory of Open Access Journals (Sweden)

    P. C. Rath

    1959-10-01

    Full Text Available It is proved that in the absence of any cross-Magnus-effects, the motion of a spinning artillery shell is stable if, s>=(v+h/Sup2 (1+gamma/sub2 /4vh. where S is the usual stability factor, gamma, h and gamma/sub2 are factors of certain aerodynamic forces acting on the projectile. The above condition is obtained by applying Fowler's method of approximation to Nielsen and Synge stability conditions. If the cross force due to cross spin be neglected (i.e.gamma/sub2=0, this goes over to the usual Nielsen and Synge condition of stability.

  3. 基于 FSAE 赛车的空气动力学套件设计及 CFD 分析%Design of an Aerodynamic Package for FSAE Racing Car and CFD Analysis

    Institute of Scientific and Technical Information of China (English)

    韩小强; 王洪宇; 侯文彬

    2016-01-01

    在赛车领域,空气动力学研究已经成为各项赛事以及车队之间竞争的焦点。文中通过对 G03C 赛车进行整车空气动力学分析,找出整车造型对空气动力学的影响因素,并根据空气动力学原理设计了一套相匹配的空气动力学套件,包括鼻翼、尾翼及扩散器。对比改装前后赛车的空气力学性能,结果表明,安装空气动力学套件后,产生一定的下压力使得赛车的高速稳定性能得到提升。%In the field of racing cars,air dynamics research has become the focus of competition between the events and teams. For Formula SAE,aerodynamic research is very important.This paper through aerodynamic simulation analysis of G03C racing car, finds out influence aerodynamic factors of the vehicle model,and designs an aerodynamics package for it according to the principle of aerodynamics,including the front wing,rear wing and diffuser.Compared the aerodynamic performance of the car before and after modification,the results show that the increase of pressure makes the car high -speed stability improve under suite aerodynamic pack-age.

  4. Unsteady aerodynamics and flow control for flapping wing flyers

    Science.gov (United States)

    Ho, Steven; Nassef, Hany; Pornsinsirirak, Nick; Tai, Yu-Chong; Ho, Chih-Ming

    2003-11-01

    The creation of micro air vehicles (MAVs) of the same general sizes and weight as natural fliers has spawned renewed interest in flapping wing flight. With a wingspan of approximately 15 cm and a flight speed of a few meters per second, MAVs experience the same low Reynolds number (10 4-10 5) flight conditions as their biological counterparts. In this flow regime, rigid fixed wings drop dramatically in aerodynamic performance while flexible flapping wings gain efficacy and are the preferred propulsion method for small natural fliers. Researchers have long realized that steady-state aerodynamics does not properly capture the physical phenomena or forces present in flapping flight at this scale. Hence, unsteady flow mechanisms must dominate this regime. Furthermore, due to the low flight speeds, any disturbance such as gusts or wind will dramatically change the aerodynamic conditions around the MAV. In response, a suitable feedback control system and actuation technology must be developed so that the wing can maintain its aerodynamic efficiency in this extremely dynamic situation; one where the unsteady separated flow field and wing structure are tightly coupled and interact nonlinearly. For instance, birds and bats control their flexible wings with muscle tissue to successfully deal with rapid changes in the flow environment. Drawing from their example, perhaps MAVs can use lightweight actuators in conjunction with adaptive feedback control to shape the wing and achieve active flow control. This article first reviews the scaling laws and unsteady flow regime constraining both biological and man-made fliers. Then a summary of vortex dominated unsteady aerodynamics follows. Next, aeroelastic coupling and its effect on lift and thrust are discussed. Afterwards, flow control strategies found in nature and devised by man to deal with separated flows are examined. Recent work is also presented in using microelectromechanical systems (MEMS) actuators and angular speed

  5. MASCOT - MATLAB Stability and Control Toolbox

    Science.gov (United States)

    Kenny, Sean; Crespo, Luis

    2011-01-01

    MASCOT software was created to provide the conceptual aircraft designer accurate predictions of air vehicle stability and control characteristics. The code takes as input mass property data in the form of an inertia tensor, aerodynamic loading data, and propulsion (i.e. thrust) loading data. Using fundamental non-linear equations of motion, MASCOT then calculates vehicle trim and static stability data for any desired flight condition. Common predefined flight conditions are included. The predefined flight conditions include six horizontal and six landing rotation conditions with varying options for engine out, crosswind and sideslip, plus three takeoff rotation conditions. Results are displayed through a unique graphical interface developed to provide stability and control information to the conceptual design engineers using a qualitative scale indicating whether the vehicle has acceptable, marginal, or unacceptable static stability characteristics. This software allows the user to prescribe the vehicle s CG location, mass, and inertia tensor so that any loading configuration between empty weight and maximum take-off weight can be analyzed. The required geometric and aerodynamic data as well as mass and inertia properties may be entered directly, passed through data files, or come from external programs such as Vehicle Sketch Pad (VSP). The current version of MASCOT has been tested with VSP used to compute the required data, which is then passed directly into the program. In VSP, the vehicle geometry is created and manipulated. The aerodynamic coefficients, stability and control derivatives, are calculated using VorLax, which is now available directly within VSP. MASCOT has been written exclusively using the technical computing language MATLAB . This innovation is able to bridge the gap between low-fidelity conceptual design and higher-fidelity stability and control analysis. This new tool enables the conceptual design engineer to include detailed static stability

  6. Aerodynamic derivatives for an oblique wing aircraft estimated from flight data by using a maximum likelihood technique

    Science.gov (United States)

    Maine, R. E.

    1978-01-01

    There are several practical problems in using current techniques with five degree of freedom equations to estimate the stability and control derivatives of oblique wing aircraft from flight data. A technique was developed to estimate these derivatives by separating the analysis of the longitudinal and lateral directional motion without neglecting cross coupling effects. Although previously applied to symmetrical aircraft, the technique was not expected to be adequate for oblique wing vehicles. The application of the technique to flight data from a remotely piloted oblique wing aircraft is described. The aircraft instrumentation and data processing were reviewed, with particular emphasis on the digital filtering of the data. A complete set of flight determined stability and control derivative estimates is presented and compared with predictions. The results demonstrated that the relatively simple approach developed was adequate to obtain high quality estimates of the aerodynamic derivatives of such aircraft.

  7. Abort System Using Supersonic Aerodynamic Interaction for Capsule-Type Space Transportation System

    Science.gov (United States)

    小澤, 啓伺; 北村, 圭一; 花井, 勝祥; 三好, 理也; 森, 浩一; 中村, 佳朗

    The space transportation system using capsule/rocket configurations such as Apollo and Soyuz are simple compared with Space Shuttle, and have several merits from the viewpoint of reliability. The capsule/rocket system will take over the Space Shuttle, after it retires in 2010. As the Space Shuttle accidents had been caused by several factors, e.g., aerodynamic interaction of shock waves ahead of its wing, advanced abort systems such as LAS (Launch Abort System) are required for the capsule/rocket system. In the present study, as a baseline configuration, a combination of a cone and a cylinder is employed as a CEV (Crew Exploration Vehicle), which consists of a capsule (LAV: Launch Abort Vehicle) and a rocket (SM: Service Module). By changing the relative position of the two components as well as the profile area of the rocket, their effects on the capsule/rocket aerodynamic interaction and characteristics (drag and pitching moment) are experimentally and numerically investigated at a supersonic speed (M∞ = 3.0). It is found from the results that the clearance have little effects on the flow field for the case of the baseline configuration. The capsule always showed a positive drag (CD = 0.34), which means that thrust is required to overcome the drag. Otherwise the capsule will recontact the rocket. However in the case where the rocket contact area is 2.2 times as large as the capsule profile, more favorable effects were obtained. Especially in the case of a certain clearance (h/D = 0.40), the drag coefficient of the capsule is CD = -0.35, which means that the capsule suffers a thrust force from the aerodynamic interaction. Under this condition, if capsule has a pitch angle with 5 degrees instantaneously, then pitching moment coefficient becomes CMp = -0.41 therefore capsule stabilize. However, in the case of a very small clearance (h/D ∝ 0.00), the flow becomes unsteady involving pulsating shock wave, leading to a potentially risky separation of the capsule.

  8. Stability in hovering ornithopter flight

    Science.gov (United States)

    Dietl, John M.; Garcia, Ephrahim

    2008-03-01

    The quasi-steady aerodynamics model is coupled to a dynamic model of ornithopter flight. Previously, the combined model has been used to calculate forward flight trajectories, each a limit cycle in the vehicle's states. The limit cycle results from the periodic wing beat, producing a periodic force while on the cycle's trajectory. This was accomplished using a multiple shooting algorithm and numerical integration in MATLAB. An analysis of hover, a crucial element to vertical takeoff and landing in adverse conditions, follows. A method to calculate plausible wing flapping motions and control surface deflections for hover is developed, employing the above flight dynamics model. Once a hovering limit cycle trajectory is found, it can be linearized in discrete time and analyzed for stability (by calculating the trajectory's Floquet multipliers a type of discrete-time eigenvalue) are calculated. The dynamic mode shapes are discussed.

  9. FLEXSTAB: A computer program for the prediction of loads and stability and control of flexible aircraft

    Science.gov (United States)

    Perkin, B. R.; Erickson, L. R.

    1976-01-01

    Capabilities of the FLEXSTAB Computer Program System are described and illustrated. Aeroelastic analysis of a wide variety of aircraft configurations is performed. The aerodynamic theory used in FLEXSTAB is applicable to both steady and unsteady, subsonic and supersonic flow for multiple wing-body tail nacelle configurations with a plane of symmetry. For unsteady flow calculations, an unsteady aerodynamic theory is used which is appropriate for the low reduced frequencies associated with aircraft flight dynamics. The aircraft is modeled as either a rigid or flexible structure. The computer trims the aircraft in steady reference flight and computes both static and dynamic stability and control derivatives and the stability behavior about the trim condition. The airplane lifting pressure distribution, aerodynamic and inertia loads and deflected shape are also computed.

  10. Parameterization of gaseous dry deposition in atmospheric chemistry models: Sensitivity to aerodynamic resistance formulations under statically stable conditions

    Science.gov (United States)

    Toyota, Kenjiro; Dastoor, Ashu P.; Ryzhkov, Andrei

    2016-12-01

    Turbulence controls the vertical transfer of momentum, heat and trace constituents in the atmospheric boundary layer. In the lowest 10% of this layer lies the surface boundary layer (SBL) where the vertical fluxes of transferred quantities have been successfully parameterized using the Monin-Obukhov similarity theory in weather forecast, climate and atmospheric chemistry models. However, there is a large degree of empiricism in the stability-correction parameterizations used to formulate eddy diffusivity and aerodynamic resistance particularly under strongly stable ambient conditions. Although the influence of uncertainties in stability-correction parameterizations on eddy diffusivity is actively studied in boundary-layer meteorological modeling, its impact on dry deposition in atmospheric chemistry modeling is not well characterized. In this study, we address this gap by providing the mathematical basis for the relationship between the formulations of vertical surface flux used in meteorological and atmospheric chemistry modeling communities, and by examining the sensitivity of the modeled dry deposition velocities in statically stable SBL to the choice of stability-correction parameterizations used in three operational and/or research environmental models (GEM/GEM-MACH, ECMWF IFS and CMAQ-MM5). Aerodynamic resistances (ra) calculated by the three sets of parameterizations are notably different from each other and are also different from those calculated by a "z-less" scaling formulation under strongly stable conditions (the bulk Richardson number > 0.2). Furthermore, we show that many atmospheric chemistry models calculate ra using formulations which are inconsistent with the derivation of micro-meteorological parameters. Finally, practical implications of the differences in stability-correction algorithms are discussed for the computations of dry deposition velocities of SO2, O3 and reactive bromine compounds for specific cases of stable SBL.

  11. A Practical Method to Estimate the Aerodynamic Coefficients of a Small-Scale Paramotor

    Directory of Open Access Journals (Sweden)

    Razvan-Viorel MIHAI

    2014-12-01

    Full Text Available There are few aircraft other than lighter-than-air vehicles that have the payload carrying capability, short field take-off, and slow speed ranges afforded by a powered parafoil. One very interesting aspect of the powered parafoils or paramotors, is their tendency to fly at a constant airspeed whether it is climbing, descending, or flying straight-and-level. Not only are the aircraft speed stable, but they have pendulum stability as well, due to the mass of the airframe suspended significantly below the canopy. This allows the aircraft to maintain a safe roll attitude and effectively turn in a coordinated manner when the steering pedals are deflected. One of the challenges of flying these aircraft is the necessity of controlling altitude with thrust, and direction with asymmetric drag. The paper presents a practical method to estimate the aerodynamic coefficients of a small-scale paramotor in order to obtain a suitable mathematical model for the aerial vehicle. Thus, a reduced state linear model based on a simplified nonlinear six degree-of-freedom model (6 DOF is described. The autonomous control relies on the paramotor dynamics. And those equations depend on the aerodynamic coefficients. The task in this paper is to record the data of steady state flight regime, and to process it offline. Therefore, the system identification of the small-scale aerial vehicle can be done using the Two-Step Method, resulting an efficient six degree-of-freedom mini-paramotor model. The current work will permit the implementation of the control architecture in order to achieve the autonomous control of the small-scale paramotor through waypoints.

  12. Experimental and Analytical Analysis of Perforated Plate Aerodynamics

    Institute of Scientific and Technical Information of China (English)

    Jürgen Zierep; Rainer Bohning; Piotr Doerffer

    2003-01-01

    Perforated walls and transpiration flow play an important role in aerodynamics due to an increasing interest in application of flow control by means of blowing and/or suction. An experimental study was carried out which has led to the determination of a transpiration flow characteristics in the form of a simple formula that is very useful in modelling such flows. In connection to this relation a method of "aerodynamic porosity" determination has been proposed which is much more reliable than geometric description of the porosity. A theoretical analysis of the flow through a perforation hole was also carried out. The flow was considered as compressible and viscous. The gasdynamic analysis led us to a very similar result to the relation obtained from the experiment. The adequacy of the theoretical result is discussed in respect to the experiment.

  13. Aerodynamics of ski jumping: experiments and CFD simulations

    Energy Technology Data Exchange (ETDEWEB)

    Meile, W.; Reisenberger, E.; Brenn, G. [Graz University of Technology, Institute of Fluid Mechanics and Heat Transfer, Graz (Austria); Mayer, M. [VRVis GmbH, Vienna (Austria); Schmoelzer, B.; Mueller, W. [Medical University of Graz, Department for Biophysics, Graz (Austria)

    2006-12-15

    The aerodynamic behaviour of a model ski jumper is investigated experimentally at full-scale Reynolds numbers and computationally applying a standard RANS code. In particular we focus on the influence of different postures on aerodynamic forces in a wide range of angles of attack. The experimental results proved to be in good agreement with full-scale measurements with athletes in much larger wind tunnels, and form a reliable basis for further predictions of the effects of position changes on the performance. The comparison of CFD results with the experiments shows poor agreement, but enables a clear outline of simulation potentials and limits when accurate predictions of effects from small variations are required. (orig.)

  14. Study on Aerodynamic Design Optimization of Turbomachinery Blades

    Institute of Scientific and Technical Information of China (English)

    Naixing CHEN; Hongwu ZHANG; Weiguang HUANG; Yanji XU

    2005-01-01

    This paper describes the study on aerodynamics design optimization of turbomachinery blading developed by the authors at the Institute of Engineering Thermophysics, Chinese Academy of Sciences, during the recent few years. The present paper describes the aspects mainly on how to use a rapid approach of profiling a 3D blading and of grid generation for computation, a fast and accurate viscous computation method and an appropriate optimization methodology_ including a blade parameterization algorithm to optimize turbomachinery blading aerodynamically. Any blade configuration can be expressed by three curves, they are the camber lines, the thickness distributions and the radial stacking line, and then the blade geometry can be easily parameterized by a number of parameters with three polynomials. A gradient-based parameterization analytical method and a response surface method were applied herein for blade optimization. It was found that the optimization process provides reliable design for turbomachinery with reasonable computing time.

  15. Aircraft Noise Prediction Program theoretical manual: Propeller aerodynamics and noise

    Science.gov (United States)

    Zorumski, W. E. (Editor); Weir, D. S. (Editor)

    1986-01-01

    The prediction sequence used in the aircraft noise prediction program (ANOPP) is described. The elements of the sequence are called program modules. The first group of modules analyzes the propeller geometry, the aerodynamics, including both potential and boundary-layer flow, the propeller performance, and the surface loading distribution. This group of modules is based entirely on aerodynamic strip theory. The next group of modules deals with the first group. Predictions of periodic thickness and loading noise are determined with time-domain methods. Broadband noise is predicted by a semiempirical method. Near-field predictions of fuselage surface pressrues include the effects of boundary layer refraction and scattering. Far-field predictions include atmospheric and ground effects.

  16. Influence of a humidor on the aerodynamics of baseballs

    Science.gov (United States)

    Meyer, Edmund R.; Bohn, John L.

    2008-11-01

    We investigate whether storing baseballs in a controlled humidity environment significantly affects their aerodynamic properties. We measure the change in diameter and weight of baseballs as a function of relative humidity in which the balls are stored. The trajectories of pitched and batted baseballs are modeled to assess the difference between those stored at 30% relative humidity versus 50% relative humidity. We find that a drier baseball will curve slightly more than a humidified one for a given pitch velocity and rotation rate. We also find that aerodynamics alone would add 2ft to the distance a wetter baseball ball is hit. This increased distance is compensated by a 6ft reduction in the batted distance due to the change in the coefficient of restitution of the ball. We discuss consequences of these results for baseball played at Coors Field in Denver, where baseballs have been stored in a humidor at 50% relative humidity since 2002.

  17. Satellite Aerodynamics and Density Determination from Satellite Dynamic Response

    Science.gov (United States)

    Karr, G. R.

    1972-01-01

    The aerodynamic drag and lift properties of a satellite are first expressed as a function of two parameters associated with gas-surface interaction at the satellite surface. The dynamic response of the satellite as it passes through the atmosphere is then expressed as a function of the two gas-surface interaction parameters, the atmospheric density, the satellite velocity, and the satellite orientation to the high speed flow. By proper correlation of the observed dynamic response with the changing angle of attack of the satellite, it is found that the two unknown gas-surface interaction parameters can be determined. Once the gas-surface interaction parameters are known, the aerodynamic properties of the satellite at all angles of attack are also determined.

  18. Parameterization adaption for 3D shape optimization in aerodynamics

    Directory of Open Access Journals (Sweden)

    Badr Abou El Majd

    2013-10-01

    Full Text Available When solving a PDE problem numerically, a certain mesh-refinement process is always implicit, and very classically, mesh adaptivity is a very effective means to accelerate grid convergence. Similarly, when optimizing a shape by means of an explicit geometrical representation, it is natural to seek for an analogous concept of parameterization adaptivity. We propose here an adaptive parameterization for three-dimensional optimum design in aerodynamics by using the so-called “Free-Form Deformation” approach based on 3D tensorial Bézier parameterization. The proposed procedure leads to efficient numerical simulations with highly reduced computational costs.[How to cite this article:  Majd, B.A.. 2014. Parameterization adaption for 3D shape optimization in aerodynamics. International Journal of Science and Engineering, 6(1:61-69. Doi: 10.12777/ijse.6.1.61-69

  19. AERODYNAMIC OPTIMIZATION DESIGN OF LOW ASPECT RATIO TRANSONIC TURBINE STAGE

    Institute of Scientific and Technical Information of China (English)

    SONG Liming; LI Jun; FENG Zhenping

    2006-01-01

    The advanced optimization method named as adaptive range differential evolution (ARDE)is developed. The optimization performance of ARDE is demonstrated using a typical mathematical test and compared with the standard genetic algorithm and differential evolution. Combined with parallel ARDE, surface modeling method and Navier-Stokes solution, a new automatic aerodynamic optimization method is presented. A low aspect ratio transonic turbine stage is optimized for the maximization of the isentropic efficiency with forty-one design variables in total. The coarse-grained parallel strategy is applied to accelerate the design process using 15 CPUs. The isentropic efficiency of the optimum design is 1.6% higher than that of the reference design. The aerodynamic performance of the optimal design is much better than that of the reference design.

  20. Experimental Investigation on Aerodynamic Characteristics of a Paraglider Wing

    Science.gov (United States)

    Mashud, Mohammad; Umemura, Akira

    The fundamental aerodynamic characteristics of a paraglider’s canopy are investigated in wind tunnel experiments using an inflatable cell model designed to represent the dynamic behaviors of each cell comprising the canopy. At attack angles greater than a few degrees, the cell model inflates fully. To characterize its aerodynamic characteristics, we focus our attention on the flow around the inflated cell model at the plane of symmetry of the model. The cross-sectional profile of the inflated cell model, streamline pattern, internal air pressure and external surface pressure distribution are measured at various attack angles in order to identify the function of air intake and to obtain the lift and drag coefficients of the airfoil with an open air intake. The results reveal the mechanism of how the cell inflates into a stable wing shape and bears the buckling force caused by the cables suspending a pay load.

  1. Wing Warping, Roll Control and Aerodynamic Optimization of Inflatable Wings

    Science.gov (United States)

    Simpson, Andrew

    2005-11-01

    The research presents work on aerodynamic control by warping inflatable wings. Inflatable wings are deformable by their nature. Mechanical manipulation of the wing's shape has been demonstrated to alter the performance and control the vehicle in flight by deforming the trailing edge of the wing near the wing tip. Predicting and correlating the forces required in deforming the wings to a particular shape and the deformation generated for a given internal pressure were conducted through the use of photogrammetry. This research focuses on optimizing the roll moments and aerodynamic performance of the vehicle, given the current level of wing warping ability. Predictions from lifting line theory applied to wing shape changes are presented. Comparisons from the experimental results are made with lifting line analysis for wings with arbitrary twist and the solutions are used to determine rolling moment and optimum L/D. Results from flight tests will also be presented.

  2. Improvement in Aerodynamic Characteristics of a Paraglider Wing Canopy

    Science.gov (United States)

    Mashud, Mohammad; Umemura, Akira

    To determine the parameters which can improve the overall performance of a paraglider wing canopy, we have been investigating the fundamental aerodynamic characteristics of an inflatable cell model which is designed to represent the dynamic behaviors of each cell comprising the wing canopy. This paper describes the results of a series of wind tunnel experiments. It is shown that significant drag reduction can be achieved by adopting an appropriately designed shape for the soft cloth comprising the upper surface. A trade-off relationship between the aerodynamic quality (characterized by the lift-to-drag ratio) and structural strength (characterized by the internal air pressure coefficient) of the canopy is also examined in detail.

  3. BTT autopilot design for agile missiles with aerodynamic uncer tainty

    Institute of Scientific and Technical Information of China (English)

    Yueyue Ma; Jie Guo; Shengjing Tang

    2015-01-01

    The approach to the synthesis of autopilot with aerody-namic uncertainty is investigated in order to achieve large maneu-verability of agile missiles. The dynamics of the agile missile with reaction-jet control system (RCS) are presented. Subsequently, the cascade control scheme based on the bank-to-turn (BTT) steering technique is described. To address the aerodynamic un-certainties encountered by the control system, the active distur-bance rejection control (ADRC) method is introduced in the autopi-lot design. Furthermore, a compound control er, using extended state observer (ESO) to online estimate system uncertainties and calculate derivative of command signals, is designed based on dynamic surface control (DSC). Nonlinear simulation results show the feasibility of the proposed approach and validate the robust-ness of the control er with severe unmodeled dynamics.

  4. Aerodynamic Limits on Large Civil Tiltrotor Sizing and Efficiency

    Science.gov (United States)

    Acree, C W., Jr.

    2014-01-01

    The NASA Large Civil Tiltrotor (2nd generation, or LCTR2) has been the reference design for avariety of NASA studies of design optimization, engine and gearbox technology, handling qualities, andother areas, with contributions from NASA Ames, Glenn and Langley Centers, plus academic and industrystudies. Ongoing work includes airfoil design, 3D blade optimization, engine technology studies, andwingrotor aerodynamic interference. The proposed paper will bring the design up to date with the latestresults of such studies, then explore the limits of what aerodynamic improvements might hope toaccomplish. The purpose is two-fold: 1) determine where future technology studies might have the greatestpayoff, and 2) establish a stronger basis of comparison for studies of other vehicle configurations andmissions.

  5. Development of an aerodynamic measurement system for hypersonic rarefied flows.

    Science.gov (United States)

    Ozawa, T; Fujita, K; Suzuki, T

    2015-01-01

    A hypersonic rarefied wind tunnel (HRWT) has lately been developed at Japan Aerospace Exploration Agency in order to improve the prediction of rarefied aerodynamics. Flow characteristics of hypersonic rarefied flows have been investigated experimentally and numerically. By conducting dynamic pressure measurements with pendulous models and pitot pressure measurements, we have probed flow characteristics in the test section. We have also improved understandings of hypersonic rarefied flows by integrating a numerical approach with the HRWT measurement. The development of the integration scheme between HRWT and numerical approach enables us to estimate the hypersonic rarefied flow characteristics as well as the direct measurement of rarefied aerodynamics. Consequently, this wind tunnel is capable of generating 25 mm-core flows with the free stream Mach number greater than 10 and Knudsen number greater than 0.1.

  6. Aerodynamic characteristics research on wide-speed range waverider configuration

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Waverider generated from a given flow field has a high lift-to-drag ratio because of attached bow shock on leading edge. However, leading edge blunt and off-design condition can make bow shock off leading edge and have unfavorable influence on aerodynamic characteristics. So these two problems have always been concerned as important engineering science issues by aeronautical engineering scientists. In this paper, through respectively using low speed and high speed waverider design principles, a wide-speed rang vehicle is designed, which can level takeoff and accelerate to hypersonic speed for cruise. In addition, sharp leading edge is blunted to alleviated aeroheating. Theoretical study and wind tunnel test show that this vehicle has good aerodynamic performance in wide-speed range of subsonic, transonic, supersonic and hypersonic speeds.

  7. Nonlinear, unsteady aerodynamic loads on rectangular and delta wings

    Science.gov (United States)

    Atta, E. H.; Kandil, O. A.; Mook, D. T.; Nayfeh, A. H.

    1977-01-01

    Nonlinear unsteady aerodynamic loads on rectangular and delta wings in an incompressible flow are calculated by using an unsteady vortex-lattice model. Examples include flows past fixed wings in unsteady uniform streams and flows past wings undergoing unsteady motions. The unsteadiness may be due to gusty winds or pitching oscillations. The present technique establishes a reliable approach which can be utilized in the analysis of problems associated with the dynamics and aeroelasticity of wings within a wide range of angles of attack.

  8. Aerodynamic Classification of Swept-Wing Ice Accretion

    Science.gov (United States)

    Diebold, Jeff M.; Broeren, Andy P.; Bragg, Michael B.

    2013-01-01

    The continued design, certification and safe operation of swept-wing airplanes in icing conditions rely on the advancement of computational and experimental simulation methods for higher fidelity results over an increasing range of aircraft configurations and performance, and icing conditions. The current stateof- the-art in icing aerodynamics is mainly built upon a comprehensive understanding of two-dimensional geometries that does not currently exist for fundamentally three-dimensional geometries such as swept wings. The purpose of this report is to describe what is known of iced-swept-wing aerodynamics and to identify the type of research that is required to improve the current understanding. Following the method used in a previous review of iced-airfoil aerodynamics, this report proposes a classification of swept-wing ice accretion into four groups based upon unique flowfield attributes. These four groups are: ice roughness, horn ice, streamwise ice and spanwise-ridge ice. In the case of horn ice it is shown that a further subclassification of "nominally 3D" or "highly 3D" horn ice may be necessary. For all of the proposed ice-shape classifications, relatively little is known about the three-dimensional flowfield and even less about the effect of Reynolds number and Mach number on these flowfields. The classifications and supporting data presented in this report can serve as a starting point as new research explores swept-wing aerodynamics with ice shapes. As further results are available, it is expected that these classifications will need to be updated and revised.

  9. Applications of color graphics to complex aerodynamic analysis

    Science.gov (United States)

    Weston, Robert P.

    1987-01-01

    A variety of uses for color graphics in the display of large sets of complex aerodynamic data in two and three dimensions are summarized. These methods improve the ability of a scientific researcher to interactively review three-dimensional displays of aircraft panel geometries for the purposes of eliminating errors, and allow him to rapidly display an assortment of smooth-shaded, color-coded illustrations for his experimental and computational results.

  10. Application of neural networks to unsteady aerodynamic control

    Science.gov (United States)

    Faller, William E.; Schreck, Scott J.; Luttges, Marvin W.

    1994-01-01

    The problem under consideration in this viewgraph presentation is to understand, predict, and control the fluid mechanics of dynamic maneuvers, unsteady boundary layers, and vortex dominated flows. One solution is the application of neural networks demonstrating closed-loop control. Neural networks offer unique opportunities: simplify modeling of three dimensional, vortex dominated, unsteady separated flow fields; are effective means for controlling unsteady aerodynamics; and address integration of sensors, controllers, and time lags into adaptive control systems.

  11. Aerodynamic investigation of winglets on wind turbine blades using CFD

    OpenAIRE

    Johansen, Jeppe; Sørensen, Niels N.

    2006-01-01

    The present report describes the numerical investigation of the aerodynamics around a wind turbine blade with a winglet using Computational Fluid Dynamics, CFD. Five winglets were investigated with different twist distribution and camber. Four of themwere pointing towards the pressure side (upstream) and one was pointing towards the suction side (downstream). Additionally, a rectangular modification of the original blade tip was designed with the same planform area as the blades with winglets...

  12. Influence of satellite aerodynamics on atmospheric density determination.

    Science.gov (United States)

    Karr, G. R.; Smith, R. E.

    1972-01-01

    Discussion of aerodynamic factors which influence the interpretation of satellite dynamic response. These factors include: (1) the influence of satellite orientation and shape on the drag coefficient; (2) the effect of changes in the gas flow properties with altitude; and (3) the influence of upper atmospheric winds on the interpretation of data. These factors represent the greatest source of error in current data reduction. For this reason, an estimate is made of a possible correction to present density models.

  13. Determining Aerodynamic Loads Based on Optical Deformation Measurements

    Science.gov (United States)

    Liu, Tianshu; Barrows, D. A.; Burner, A. W.; Rhew, R. D.

    2001-01-01

    This paper describes a videogrammetric technique for determining aerodynamic loads based on optical elastic deformation measurements. The data reduction methods are developed to extract the normal force and pitching moment from beam deformation data. The axial force is obtained by measuring the axial translational motion of a movable shaft in a spring/bearing device. Proof-of-concept calibration experiments are conducted to assess the accuracy of this optical technique.

  14. Aerodynamic Effects Of Deicing And Anti-Icing Fluids

    Science.gov (United States)

    Addy, Harold E., Jr.; Runyan, L. James; Zierten, Thomas A.; Hill, Eugene G.

    1994-01-01

    Report presents results of wind-tunnel tests of aerodynamic effects of deicing and anti-icing fluids on airplane wings. Tests conducted on three-dimensional half-model airplane and two-dimensional airfoil model at temperatures ranging from -29 to +10 degrees C. Fluids used included three commercial fluids available for use during 1987-1988 winter season, one discontinued commercial fluid, and eight newer fluids experimental at time of test.

  15. Aerodynamic assessment of humpback whale ventral fin shapes

    OpenAIRE

    2011-01-01

    The ventral fins of the humpback whale (Megaptera novaeangliae) include a bulbous leading edge acting as a natural high-lift device. It has been suggested that application of this concept to wing design may yield advantages over traditional shapes (Miklosovic, et al., 2004). During the course of this project, the aerodynamic performance of whale fin models will be compared with conventional wing shapes. Based on the results of the study new wing design paradigms will be developed to improve t...

  16. Reducing Aerodynamic Drag on Empty Open Cargo Vehicles

    Science.gov (United States)

    Ross, James C.; Storms, Bruce L.; Dzoan, Dan

    2009-01-01

    Some simple structural modifications have been demonstrated to be effective in reducing aerodynamic drag on vehicles that have empty open cargo bays. The basic idea is to break up the airflow in a large open cargo bay by inserting panels to divide the bay into a series of smaller bays. In the case of a coal car, this involves inserting a small number (typically between two and four) of vertical full-depth or partial-depth panels.

  17. Aerodynamic Performance and Turbulence Measurements in a Turbine Vane Cascade

    Science.gov (United States)

    Boyle, Robert J.; Lucci, Barbara L.; Senyitko, Richard G.

    2002-01-01

    Turbine vane aerodynamics were measured in a three vane linear cascade. Surface pressures and blade row losses were obtained over a range of Reynolds and Mach number for three levels of turbulence. Comparisons are made with predictions using a quasi-3D Navier-Stokes analysis. Turbulence intensity measurement were made upstream and downstream of the vane. The purpose of the downstream measurements was to determine how the turbulence was affected by the strong contraction through 75 deg turning.

  18. Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Technology Development Overview

    Science.gov (United States)

    Hughes, Stephen J.; Cheatwood, F. McNeil; Calomino, Anthony M.; Wright, Henry S.; Wusk, Mary E.; Hughes, Monica F.

    2013-01-01

    The successful flight of the Inflatable Reentry Vehicle Experiment (IRVE)-3 has further demonstrated the potential value of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology. This technology development effort is funded by NASA's Space Technology Mission Directorate (STMD) Game Changing Development Program (GCDP). This paper provides an overview of a multi-year HIAD technology development effort, detailing the projects completed to date and the additional testing planned for the future.

  19. Study of the triple-mass Tethered Satellite System under aerodynamic drag and J2 perturbations

    Science.gov (United States)

    Razzaghi, Pourya; Assadian, Nima

    2015-11-01

    The dynamics of multi-tethered satellite formations consisting of three masses are studied in this paper. The triple-mass triple-tethered satellite system is modeled under the low Earth orbit perturbations of drag and Earth's oblateness and its equilibrium conditions are derived. It is modeled as three equal end-masses connected by a uniform-mass straight tether. The lengths of tethers are supposed to be constant and in this manner the angles of the plane consisting the masses are taken as the state variables of the system. The governing equations of motion are derived using Lagrangian approach. The aerodynamic drag perturbation is expressed as an external non-conservative force and the Earth oblateness (J2 perturbation) is considered as a term of potential energy. The equilibrium conditions of this system are found and their stability is investigated through the linear stability theory. Then, the results are verified by using a nonlinear simulation for three types of equilibrium conditions.

  20. High angle of attack aerodynamics subsonic, transonic, and supersonic flows

    CERN Document Server

    Rom, Josef

    1992-01-01

    The aerodynamics of aircraft at high angles of attack is a subject which is being pursued diligently, because the modern agile fighter aircraft and many of the current generation of missiles must perform well at very high incidence, near and beyond stall. However, a comprehensive presentation of the methods and results applicable to the studies of the complex aerodynamics at high angle of attack has not been covered in monographs or textbooks. This book is not the usual textbook in that it goes beyond just presenting the basic theoretical and experimental know-how, since it contains reference material to practical calculation methods and technical and experimental results which can be useful to the practicing aerospace engineers and scientists. It can certainly be used as a text and reference book for graduate courses on subjects related to high angles of attack aerodynamics and for topics related to three-dimensional separation in viscous flow courses. In addition, the book is addressed to the aerodynamicist...

  1. Analysis of aerodynamic noise generated from inclined circular cylinder

    Science.gov (United States)

    Haramoto, Yasutake; Yasuda, Shouji; Matsuzaki, Kazuyoshi; Munekata, Mizue; Ohba, Hideki

    2000-06-01

    Making clear the generation mechanism of fluid dynamic noise is essential to reduce noise deriving from turbomachinery. The analysis of the aerodynamic noise generated from circular cylinder is carried out numerically and experimentally in a low noise wind tunnel. In this study, aerodynamic sound radiated from a circular cylinder in uniform flow is predicted numerically by the following two step method. First, the three-dimensional unsteady incompressible Navier-Stokes equation is solved using the high order accurate upwind scheme. Next, the sound pressure level at the observed point is calculated from the fluctuating surface pressure on the cylinder, based on modified Lighthill-Curl’s equation. It is worth to note that the noise generated from the model is reduced rapidly when it is inclined against the mean flow. In other words, the peak level of the radiated noise decreases rapidly with inclination of the circular cylinder. The simulated SPL for the inclined circular cylinder is compared with the measured value, and good agreement is obtained for the peak spectrum frequency of the sound pressure level and tendency of noise reduction. So we expect that the change of flow structures makes reduction of the aerodynamic noise from the inclined models.

  2. Shape optimization for aerodynamic efficiency and low observability

    Science.gov (United States)

    Vinh, Hoang; Van Dam, C. P.; Dwyer, Harry A.

    1993-01-01

    Field methods based on the finite-difference approximations of the time-domain Maxwell's equations and the potential-flow equation have been developed to solve the multidisciplinary problem of airfoil shaping for aerodynamic efficiency and low radar cross section (RCS). A parametric study and an optimization study employing the two analysis methods are presented to illustrate their combined capabilities. The parametric study shows that for frontal radar illumination, the RCS of an airfoil is independent of the chordwise location of maximum thickness but depends strongly on the maximum thickness, leading-edge radius, and leadingedge shape. In addition, this study shows that the RCS of an airfoil can be reduced without significant effects on its transonic aerodynamic efficiency by reducing the leading-edge radius and/or modifying the shape of the leading edge. The optimization study involves the minimization of wave drag for a non-lifting, symmetrical airfoil with constraints on the airfoil maximum thickness and monostatic RCS. This optimization study shows that the two analysis methods can be used effectively to design aerodynamically efficient airfoils with certain desired RCS characteristics.

  3. Analysis of Aerodynamic Noise Generated from Inclined Circular Cylinder

    Institute of Scientific and Technical Information of China (English)

    YasutakeHaramoto; ShoujiYasuda; 等

    2000-01-01

    Making clear the generation mechanism of fluid dynamic noise is essential to reduce noise deriving from turbomachinery.The analysis of the aerodynamic noise generated from circular cylinder is carried out numerically and experimentally in a low noise wind tunnel.in this study,aerodynamic sound radiated from a circular cylinder in uniform flow is predicted numericaslly by the following two step method,First,the three-dimensional unsteady incompressible Navier-Stokes equation is solved using the high order accurate upwind scheme.Next.the sound pressure level at the observed point is calculated from the fluctuating surface pressure on the cylinder.based on modified Lighthill-Curl's equation.It is worth to note that the noise generated from the model is reduced rapidly when it is inclined against the mean flow.In other works,the Peak level of the radiated noise decreases apidly with inclination of the circular cylinder.The simulated SPL for the inclined circular cylinder is compared with the measured value .and good agreement is obtained for the peak spectrum fequency of the sound pressue level and tendency of noise reduction,So we expect that the change of flow structures makes reduction of the aerodynamic noise from the inclined models.

  4. Size effects on insect hovering aerodynamics: an integrated computational study

    Energy Technology Data Exchange (ETDEWEB)

    Liu, H [Graduate School of Engineering, Chiba University, Chiba, 263-8522 (Japan); Aono, H [Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI48109 (United States)], E-mail: hliu@faculty.chiba-u.jp, E-mail: aonoh@umich.edu

    2009-03-01

    Hovering is a miracle of insects that is observed for all sizes of flying insects. Sizing effect in insect hovering on flapping-wing aerodynamics is of interest to both the micro-air-vehicle (MAV) community and also of importance to comparative morphologists. In this study, we present an integrated computational study of such size effects on insect hovering aerodynamics, which is performed using a biology-inspired dynamic flight simulator that integrates the modelling of realistic wing-body morphology, the modelling of flapping-wing and body kinematics and an in-house Navier-Stokes solver. Results of four typical insect hovering flights including a hawkmoth, a honeybee, a fruit fly and a thrips, over a wide range of Reynolds numbers from O(10{sup 4}) to O(10{sup 1}) are presented, which demonstrate the feasibility of the present integrated computational methods in quantitatively modelling and evaluating the unsteady aerodynamics in insect flapping flight. Our results based on realistically modelling of insect hovering therefore offer an integrated understanding of the near-field vortex dynamics, the far-field wake and downwash structures, and their correlation with the force production in terms of sizing and Reynolds number as well as wing kinematics. Our results not only give an integrated interpretation on the similarity and discrepancy of the near- and far-field vortex structures in insect hovering but also demonstrate that our methods can be an effective tool in the MAVs design.

  5. EBF noise suppression and aerodynamic penalties. [Externally Blown Flaps

    Science.gov (United States)

    Mckinzie, L. J., Jr.

    1978-01-01

    Acoustic tests were conducted at model scale to determine the noise produced in the flyover and sideline planes at reduced separation distances between the nozzle exhaust plane and the flaps of an under-the-wing (UTW) externally blown flap (EBF) configuration in its approach attitude. Tests were also made to determine the noise suppression effectiveness of two types of passive devices which were located on the jet impingement surfaces of the configuration. In addition, static aerodynamic performance data were obtained to evaluate the penalties produced by these suppression devices. Broadband low frequency noise reductions were achieved by reducing the separation distance between the nozzle and flaps. However, mid and high frequency noise was produced which exceeded that of the reference configuration. Two passive noise suppression devices located on the flaps produced moderate to large noise reductions at reduced separation distances. Consideration of the static aerodynamic performance data obtained for the configurations tested suggests that specific broadband noise suppression characteristics may be obtained through a trade-off with aerodynamic performance penalties by the careful selection of suppression devices.

  6. Parameterization of Vegetation Aerodynamic Roughness of Natural Regions Satellite Imagery

    Science.gov (United States)

    Jasinski, Michael F.; Crago, Richard; Stewart, Pamela

    1998-01-01

    Parameterizations of the frontal area index and canopy area index of natural or randomly distributed plants are developed, and applied to the estimation of local aerodynamic roughness using satellite imagery. The formulas are expressed in terms of the subpixel fractional vegetation cover and one non-dimensional geometric parameter that characterizes the plant's shape. Geometrically similar plants and Poisson distributed plant centers are assumed. An appropriate averaging technique to extend satellite pixel-scale estimates to larger scales is provided. The parameterization is applied to the estimation of aerodynamic roughness using satellite imagery for a 2.3 sq km coniferous portion of the Landes Forest near Lubbon, France, during the 1986 HAPEX-Mobilhy Experiment. The canopy area index is estimated first for each pixel in the scene based on previous estimates of fractional cover obtained using Landsat Thematic Mapper imagery. Next, the results are incorporated into Raupach's (1992, 1994) analytical formulas for momentum roughness and zero-plane displacement height. The estimates compare reasonably well to reference values determined from measurements taken during the experiment and to published literature values. The approach offers the potential for estimating regionally variable, vegetation aerodynamic roughness lengths over natural regions using satellite imagery when there exists only limited knowledge of the vegetated surface.

  7. Lifting Wing in Constructing Tall Buildings —Aerodynamic Testing

    Directory of Open Access Journals (Sweden)

    Ian Skelton

    2014-05-01

    Full Text Available This paper builds on previous research by the authors which determined the global state-of-the-art of constructing tall buildings by surveying the most active specialist tall building professionals around the globe. That research identified the effect of wind on tower cranes as a highly ranked, common critical issue in tall building construction. The research reported here presents a design for a “Lifting Wing,” a uniquely designed shroud which potentially allows the lifting of building materials by a tower crane in higher and more unstable wind conditions, thereby reducing delay on the programmed critical path of a tall building. Wind tunnel tests were undertaken to compare the aerodynamic performance of a scale model of a typical “brick-shaped” construction load (replicating a load profile most commonly lifted via a tower crane against the aerodynamic performance of the scale model of the Lifting Wing in a range of wind conditions. The data indicate that the Lifting Wing improves the aerodynamic performance by a factor of up to 50%.

  8. Wind Tunnel Tests on Aerodynamic Characteristics of Advanced Solid Rocket

    Science.gov (United States)

    Kitamura, Keiichi; Fujimoto, Keiichiro; Nonaka, Satoshi; Irikado, Tomoko; Fukuzoe, Moriyasu; Shima, Eiji

    The Advanced Solid Rocket is being developed by JAXA (Japan Aerospace Exploration Agency). Since its configuration has been changed very recently, its aerodynamic characteristics are of great interest of the JAXA Advanced Solid Rocket Team. In this study, we carried out wind tunnel tests on the aerodynamic characteristics of the present configuration for Mach 1.5. Six test cases were conducted with different body configurations, attack angles, and roll angles. A six component balance, oilflow visualization, Schlieren images were used throughout the experiments. It was found that, at zero angle-of-attack, the flow around the body were perturbed and its drag (axial force) characteristics were significantly influenced by protruding body components such as flanges, cable ducts, and attitude control units of SMSJ (Solid Motor Side Jet), while the nozzle had a minor role. With angle-of-attack of five degree, normal force of CNα = 3.50±0.03 was measured along with complex flow features observed in the full-component model; whereas no crossflow separations were induced around the no-protuberance model with CNα = 2.58±0.10. These values were almost constant with respect to the angle-of-attack in both of the cases. Furthermore, presence of roll angle made the flow more complicated, involving interactions of separation vortices. These data provide us with fundamental and important aerodynamic insights of the Advanced Solid Rocket, and they will be utilized as reference data for the corresponding numerical analysis.

  9. The Mechanical Impact of Aerodynamic Stall on Tunnel Ventilation Fans

    Directory of Open Access Journals (Sweden)

    A. G. Sheard

    2012-01-01

    Full Text Available This paper describes work aimed at establishing the ability of a tunnel ventilation fan to operate without risk of mechanical failure in the event of aerodynamic stall. The research establishes the aerodynamic characteristics of a typical tunnel ventilation fan when operated in both stable and stalled aerodynamic conditions, with and without an anti-stall stabilisation ring, with and without a “nonstalling” blade angle and at full, half, and one quarter design speed. It also measures the fan’s peak stress, thus facilitating an analysis of the implications of the experimental results for mechanical design methodology. The paper concludes by presenting three different strategies for tunnel ventilation fan selection in applications where the selected fan will most likely stall. The first strategy selects a fan with a low-blade angle that is nonstalling. The second strategy selects a fan with a high-pressure developing capability. The third strategy selects a fan with a fitted stabilisation ring. Tunnel ventilation system designers each have their favoured fan selection strategy. However, all three strategies can produce system designs within which a tunnel ventilation fan performs reliably in-service. The paper considers the advantages and disadvantages of each selection strategy and considered the strengths and weaknesses of each.

  10. Sensitivity Analysis and Optimization of Aerodynamic Configurations with Blend Surfaces

    Science.gov (United States)

    Thomas, A. M.; Tiwari, S. N.

    1997-01-01

    A novel (geometrical) parametrization procedure using solutions to a suitably chosen fourth order partial differential equation is used to define a class of airplane configurations. Inclusive in this definition are surface grids, volume grids, and grid sensitivity. The general airplane configuration has wing, fuselage, vertical tail and horizontal tail. The design variables are incorporated into the boundary conditions, and the solution is expressed as a Fourier series. The fuselage has circular cross section, and the radius is an algebraic function of four design parameters and an independent computational variable. Volume grids are obtained through an application of the Control Point Form method. A graphic interface software is developed which dynamically changes the surface of the airplane configuration with the change in input design variable. The software is made user friendly and is targeted towards the initial conceptual development of any aerodynamic configurations. Grid sensitivity with respect to surface design parameters and aerodynamic sensitivity coefficients based on potential flow is obtained using an Automatic Differentiation precompiler software tool ADIFOR. Aerodynamic shape optimization of the complete aircraft with twenty four design variables is performed. Unstructured and structured volume grids and Euler solutions are obtained with standard software to demonstrate the feasibility of the new surface definition.

  11. Spacecraft Re-Entry Impact Point Targeting Using Aerodynamic Drag

    Science.gov (United States)

    Omar, Sanny R.; Bevilacqua, Riccardo

    2017-01-01

    The ability to re-enter the atmosphere at a desired location is important for spacecraft containing components that may survive re-entry. While impact point targeting has traditionally been initiated through impulsive burns with chemical thrusters on large vehicles such as the Space Shuttle, and the Soyuz and Apollo capsules, many small spacecraft do not host thrusters and require an alternative means of impact point targeting to ensure that falling debris do not cause harm to persons or property. This paper discusses the use of solely aerodynamic drag force to perform this targeting. It is shown that by deploying and retracting a drag device to vary the ballistic coefficient of the spacecraft, any desired longitude and latitude on the ground can be targeted provided that the maneuvering begins early enough and the latitude is less than the inclination of the orbit. An analytical solution based on perturbations from a numerically propagated trajectory is developed to map the initial state and ballistic coefficient profile of a spacecraft to its impact point. This allows the ballistic coefficient profile necessary to reach a given target point to be rapidly calculated, making it feasible to generate the guidance for the decay trajectory onboard the spacecraft. The ability to target an impact point using aerodynamic drag will enhance the capabilities of small spacecraft and will enable larger space vehicles containing thrusters to save fuel by more effectively leveraging the available aerodynamic drag.

  12. Numerical simulation of the tip aerodynamics and acoustics test

    Science.gov (United States)

    Tejero E, F.; Doerffer, P.; Szulc, O.; Cross, J. L.

    2016-04-01

    The application of an efficient flow control system on helicopter rotor blades may lead to improved aerodynamic performance. Recently, our invention of Rod Vortex Generators (RVGs) has been analyzed for helicopter rotor blades in hover with success. As a step forward, the study has been extended to forward flight conditions. For this reason, a validation of the numerical modelling for a reference helicopter rotor (without flow control) is needed. The article presents a study of the flow-field of the AH-1G helicopter rotor in low-, medium- and high-speed forward flight. The CFD code FLOWer from DLR has proven to be a suitable tool for the aerodynamic analysis of the two-bladed rotor without any artificial wake modelling. It solves the URANS equations with LEA (Linear Explicit Algebraic stress) k-ω model using the chimera overlapping grids technique. Validation of the numerical model uses comparison with the detailed flight test data gathered by Cross J. L. and Watts M. E. during the Tip Aerodynamics and Acoustics Test (TAAT) conducted at NASA in 1981. Satisfactory agreements for all speed regimes and a presence of significant flow separation in high-speed forward flight suggest a possible benefit from the future implementation of RVGs. The numerical results based on the URANS approach are presented not only for a popular, low-speed case commonly used in rotorcraft community for CFD codes validation but preferably for medium- and high-speed test conditions that have not been published to date.

  13. Charged aerodynamics of a Low Earth Orbit cylinder

    Science.gov (United States)

    Capon, C. J.; Brown, M.; Boyce, R. R.

    2016-11-01

    This work investigates the charged aerodynamic interaction of a Low Earth Orbiting (LEO) cylinder with the ionosphere. The ratio of charge to neutral drag force on a 2D LEO cylinder with diffusely reflecting cool walls is derived analytically and compared against self-consistent electrostatic Particle-in-Cell (PIC) simulations. Analytical calculations predict that neglecting charged drag in an O+ dominated LEO plasma with a neutral to ion number density ratio of 102 will cause a 10% over-prediction of O density based on body accelerations when body potential (ɸB) is ≤ -390 V. Above 900 km altitude in LEO, where H+ becomes the dominant ion species, analytical predictions suggest charge drag becomes equivalent to neutral drag for ɸB ≤ -0.75 V. Comparing analytical predictions against PIC simulations in the range of 0 PIC simulations, our in-house 6 degree of freedom orbital propagator saw a reduction in the semi-major axis of a 10 kg satellite at 700 km of 6.9 m/day and 0.98 m/day at 900 km compared that caused purely by neutral drag - 0.67 m/day and 0.056 m/day respectively. Hence, this work provides initial evidence that charged aerodynamics may become significant compared to neutral aerodynamics for high voltage LEO bodies.

  14. Proper Orthogonal Decomposition as Surrogate Model for Aerodynamic Optimization

    Directory of Open Access Journals (Sweden)

    Valentina Dolci

    2016-01-01

    Full Text Available A surrogate model based on the proper orthogonal decomposition is developed in order to enable fast and reliable evaluations of aerodynamic fields. The proposed method is applied to subsonic turbulent flows and the proper orthogonal decomposition is based on an ensemble of high-fidelity computations. For the construction of the ensemble, fractional and full factorial planes together with central composite design-of-experiment strategies are applied. For the continuous representation of the projection coefficients in the parameter space, response surface methods are employed. Three case studies are presented. In the first case, the boundary shape of the problem is deformed and the flow past a backward facing step with variable step slope is studied. In the second case, a two-dimensional flow past a NACA 0012 airfoil is considered and the surrogate model is constructed in the (Mach, angle of attack parameter space. In the last case, the aerodynamic optimization of an automotive shape is considered. The results demonstrate how a reduced-order model based on the proper orthogonal decomposition applied to a small number of high-fidelity solutions can be used to generate aerodynamic data with good accuracy at a low cost.

  15. AEROX: Computer program for transonic aircraft aerodynamics to high angles of attack. Volume 1: Aerodynamic methods and program users' guide

    Science.gov (United States)

    Axelson, J. A.

    1977-01-01

    The AEROX program estimates lift, induced-drag and pitching moments to high angles (typ. 60 deg) for wings and for wingbody combinations with or without an aft horizontal tail. Minimum drag coefficients are not estimated, but may be input for inclusion in the total aerodynamic parameters which are output in listed and plotted formats. The theory, users' guide, test cases, and program listing are presented.

  16. Stability Functions

    CERN Document Server

    Burns, Daniel; Wang, Zuoqin

    2008-01-01

    In this article we discuss the role of stability functions in geometric invariant theory and apply stability function techniques to problems in toric geometry. In particular we show how one can use these techniques to recover results of Burns-Guillemin-Uribe and Shiffman-Tate-Zelditch on asymptotic properties of sections of holomorphic line bundles over toric varieties.

  17. Time domain analysis method for aerodynamic noises from wind turbine blades

    Directory of Open Access Journals (Sweden)

    Hua ZHAO

    2015-04-01

    Full Text Available The issue of the aerodynamic noises from wind turbine blades affecting the surrounding residents life begins to attract researcher's attention. Most of the existing researches are based on CFD software or experimental data fitting method to analyze the aerodynamic noises, so it is difficult to adapt the demand to dynamic analysis of the aerodynamic noises from wind speed variation. In this paper, the operation parameters, the inflow wind speed and the receiver location are considered, and a modified model to calculate aerodynamic noises from wind turbine blades which is based on traditional acoustic formulas is established. The program to calculate the aerodynamic noises from the 2 MW wind turbine blades is compiled using a time-domain analysis method based on the Simulink modular in Matlab software. And the pressure time sequence diagrams of the aerodynamic noises from wind turbine blades are drawn. It has provided a theoretical foundation to develop low noise wind turbine blades.

  18. Integrated design and manufacturing for the high speed civil transport (a combined aerodynamics/propulsion optimization study)

    Science.gov (United States)

    Baecher, Juergen; Bandte, Oliver; DeLaurentis, Dan; Lewis, Kemper; Sicilia, Jose; Soboleski, Craig

    1995-01-01

    This report documents the efforts of a Georgia Tech High Speed Civil Transport (HSCT) aerospace student design team in completing a design methodology demonstration under NASA's Advanced Design Program (ADP). Aerodynamic and propulsion analyses are integrated into the synthesis code FLOPS in order to improve its prediction accuracy. Executing the integrated product and process development (IPPD) methodology proposed at the Aerospace Systems Design Laboratory (ASDL), an improved sizing process is described followed by a combined aero-propulsion optimization, where the objective function, average yield per revenue passenger mile ($/RPM), is constrained by flight stability, noise, approach speed, and field length restrictions. Primary goals include successful demonstration of the application of the response surface methodolgy (RSM) to parameter design, introduction to higher fidelity disciplinary analysis than normally feasible at the conceptual and early preliminary level, and investigations of relationships between aerodynamic and propulsion design parameters and their effect on the objective function, $/RPM. A unique approach to aircraft synthesis is developed in which statistical methods, specifically design of experiments and the RSM, are used to more efficiently search the design space for optimum configurations. In particular, two uses of these techniques are demonstrated. First, response model equations are formed which represent complex analysis in the form of a regression polynomial. Next, a second regression equation is constructed, not for modeling purposes, but instead for the purpose of optimization at the system level. Such an optimization problem with the given tools normally would be difficult due to the need for hard connections between the various complex codes involved. The statistical methodology presents an alternative and is demonstrated via an example of aerodynamic modeling and planform optimization for a HSCT.

  19. Application of CAD/CAE class systems to aerodynamic analysis of electric race cars

    Science.gov (United States)

    Grabowski, L.; Baier, A.; Buchacz, A.; Majzner, M.; Sobek, M.

    2015-11-01

    Aerodynamics is one of the most important factors which influence on every aspect of a design of a car and car driving parameters. The biggest influence aerodynamics has on design of a shape of a race car body, especially when the main objective of the race is the longest distance driven in period of time, which can not be achieved without low energy consumption and low drag of a car. Designing shape of the vehicle body that must generate the lowest possible drag force, without compromising the other parameters of the drive. In the article entitled „Application of CAD/CAE class systems to aerodynamic analysis of electric race cars” are being presented problems solved by computer analysis of cars aerodynamics and free form modelling. Analysis have been subjected to existing race car of a Silesian Greenpower Race Team. On a basis of results of analysis of existence of Kammback aerodynamic effect innovative car body were modeled. Afterwards aerodynamic analysis were performed to verify existence of aerodynamic effect for innovative shape and to recognize aerodynamics parameters of the shape. Analysis results in the values of coefficients and aerodynamic drag forces. The resulting drag forces Fx, drag coefficients Cx(Cd) and aerodynamic factors Cx*A allowed to compare all of the shapes to each other. Pressure distribution, air velocities and streams courses were useful in determining aerodynamic features of analyzed shape. For aerodynamic tests was used Ansys Fluent CFD software. In a paper the ways of surface modeling with usage of Realize Shape module and classic surface modeling were presented. For shapes modeling Siemens NX 9.0 software was used. Obtained results were used to estimation of existing shapes and to make appropriate conclusions.

  20. SFFSTAB: A Computer Program to Calculate the Aerodynamic Stability of a Self-Forging Fragment.

    Science.gov (United States)

    1987-03-01

    7AD-Ai79 857 ffJLfArUf TI PPEPE N T &11/ UNCLASSIFIED F.R S O 19/1 ERL 1a L6 I .25 MICROCOPM RESOLUIUON TESI CHAR’ Dfn n UNCLASSIFIED In ~ ~ IJI...AUTIIOHSI Enter the nsretsl of outhoril as shown on or I J ABSTRACT Enter an abstrfact goi~ii a brefo anti factual is tho doioiinrt Estr last name

  1. Nonlinear Aerodynamic ROM-Structural ROM Methodology for Inflatable Aeroelasticity in Hypersonic Atmospheric Entry Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ZONA Technology proposes to develop an innovative nonlinear structural reduced order model (ROM) - nonlinear aerodynamic ROM methodology for the inflatable...

  2. Integration of an Advanced Cryogenic Electric Propulsion System (ACEPS) to Aerodynamically Efficient Subsonic Transport Aircraft Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal defines innovative aerodynamic concepts and technology goals aimed at vehicle efficiency for future subsonic aircraft in the 2020 ? 2030 timeframe....

  3. The space shuttle ascent vehicle aerodynamic challenges configuration design and data base development

    Science.gov (United States)

    Dill, C. C.; Young, J. C.; Roberts, B. B.; Craig, M. K.; Hamilton, J. T.; Boyle, W. W.

    1985-01-01

    The phase B Space Shuttle systems definition studies resulted in a generic configuration consisting of a delta wing orbiter, and two solid rocket boosters (SRB) attached to an external fuel tank (ET). The initial challenge facing the aerodynamic community was aerodynamically optimizing, within limits, this configuration. As the Shuttle program developed and the sensitivities of the vehicle to aerodynamics were better understood the requirements of the aerodynamic data base grew. Adequately characterizing the vehicle to support the various design studies exploded the size of the data base to proportions that created a data modeling/management challenge for the aerodynamicist. The ascent aerodynamic data base originated primarily from wind tunnel test results. The complexity of the configuration rendered conventional analytic methods of little use. Initial wind tunnel tests provided results which included undesirable effects from model support tructure, inadequate element proximity, and inadequate plume simulation. The challenge to improve the quality of test results by determining the extent of these undesirable effects and subsequently develop testing techniques to eliminate them was imposed on the aerodynamic community. The challenges to the ascent aerodynamics community documented are unique due to the aerodynamic complexity of the Shuttle launch. Never before was such a complex vehicle aerodynamically characterized. The challenges were met with innovative engineering analyses/methodology development and wind tunnel testing techniques.

  4. Aerodynamic load calculation of horizontal axis wind turbine in non-uniform flow

    Energy Technology Data Exchange (ETDEWEB)

    Lupo, E.

    1982-09-01

    An aerodynamic computer program, applicable to upwind rotors, was developed to calculate variable loads on rotor blades due to nonuniform flow. This program takes into account the atmospheric boundary layer, the variation in wind direction, and tower reflection. The aerodynamic analysis is based on a combination of momentum and blade element equations. The aerodynamic conditions and the airloads are for 36 azimuth positions of a rigid blade during its rotation. The inputs of the program are the geometric characteristics of the rotor and blades, the aerodynamic characteristic of the airfoil sections, the wind shear expression, the yaw and tilt angle with wind direction and the rotor-tower diameter ratio for cylindrical towers.

  5. Couplings in Multi-criterion Aerodynamic Optimization Problems Using Adjoint Methods and Game Strategies

    Institute of Scientific and Technical Information of China (English)

    Tang Zhili; Dong Jun

    2009-01-01

    complete and complete decisions of the leader and followers respectively. Several design examples illustrate the efficiency of the coupling algorithms for multi-criterion aerodynamic design optimization problems.

  6. Ensuring Stability

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    "Stable"will be a key word for China’s economy in 2012.That’s the beat set at the annual Central Economic Work Conference held in Beijing on December 12-14,which reviewed this year’s development and mapped out plans for the next year.Policymakers at the conference decided to keep macroeconomic policies stable,seek a stable and relatively fast economic growth,stabilize consumer prices and maintain social stability in 2012.On the basis of stability,the government will transform the development model,deepen reform and improve people’s livelihood.

  7. Hub vortex instability within wind turbine wakes: Effects of wind turbulence, loading conditions, and blade aerodynamics

    Science.gov (United States)

    Ashton, Ryan; Viola, Francesco; Camarri, Simone; Gallaire, Francois; Iungo, Giacomo Valerio

    2016-11-01

    The near wake of wind turbines is characterized by the presence of the hub vortex, which is a coherent vorticity structure generated from the interaction between the root vortices and the boundary layer evolving over the turbine nacelle. By moving downstream, the hub vortex undergoes an instability with growth rate, azimuthal and axial wavenumbers determined by the characteristics of the incoming wind and turbine aerodynamics. Thus, a large variability of the hub vortex instability is expected for wind energy applications with consequent effects on wake downstream evolution, wake interactions within a wind farm, power production, and fatigue loads on turbines invested by wakes generated upstream. In order to predict characteristics of the hub vortex instability for different operating conditions, linear stability analysis is carried out by considering different statistics of the incoming wind turbulence, thrust coefficient, tip speed ratio, and blade lift distribution of a wind turbine. Axial and azimuthal wake velocity fields are modeled through Carton-McWilliams velocity profiles by mimicking the presence of the hub vortex, helicoidal tip vortices, and matching the wind turbine thrust coefficient predicted through the actuator disk model. The linear stability analysis shows that hub vortex instability is strongly affected by the wind turbine loading conditions, and specifically it is promoted by a larger thrust coefficient. A higher load of the wind turbines produces an enhanced axial velocity deficit and, in turn, higher shear in the radial direction of the streamwise velocity. The axial velocity shear within the turbine wake is also the main physical mechanism promoting the hub vortex instability when varying the lift distribution over the blade span for a specific loading condition. Cases with a larger velocity deficit in proximity of the wake center and less aerodynamic load towards the blade tip result to be more unstable. Moreover, wake swirl promotes hub

  8. Experimental Aerodynamic Characteristics of an Oblique Wing for the F-8 OWRA

    Science.gov (United States)

    Kennelly, Robert A., Jr.; Carmichael, Ralph L.; Smith, Stephen C.; Strong, James M.; Kroo, Ilan M.

    1999-01-01

    An experimental investigation was conducted during June-July 1987 in the NASA Ames 11-Foot Transonic Wind Tunnel to study the aerodynamic performance and stability and control characteristics of a 0.087-scale model of an F-8 airplane fitted with an oblique wing. This effort was part of the Oblique Wing Research Aircraft (OWRA) program performed in conjunction with Rockwell International. The Ames-designed, aspect ratio 10.47, tapered wing used specially designed supercritical airfoils with 0.14 thickness/chord ratio at the root and 0.12 at the 85% span location. The wing was tested at two different mounting heights above the fuselage. Performance and longitudinal stability data were obtained at sweep angles of 0deg, 30deg, 45deg, 60deg, and 65deg at Mach numbers ranging from 0.30 to 1.40. Reynolds number varied from 3.1 x 10(exp 6)to 5.2 x 10(exp 6), based on the reference chord length. Angle of attack was varied from -5deg to 18deg. The performance of this wing is compared with that of another oblique wing, designed by Rockwell International, which was tested as part of the same development program. Lateral-directional stability data were obtained for a limited combination of sweep angles and Mach numbers. Sideslip angle was varied from -5deg to +5deg. Landing flap performance was studied, as were the effects of cruise flap deflections to achieve roll trim and tailor wing camber for various flight conditions. Roll-control authority of the flaps and ailerons was measured. A novel, deflected wing tip was evaluated for roll-control authority at high sweep angles.

  9. Stabilizing Niger

    DEFF Research Database (Denmark)

    Hahonou, Eric Komlavi

    international intervention in Niger. Their main objective is to secure their own strategic, economic and political interests by strengthening the Nigerien authorities through direct intervention and capacity building activities. For western states reinforcing state security institutions and stabilizing elite...

  10. Sequentially-coupled space-time FSI analysis of bio-inspired flapping-wing aerodynamics of an MAV

    Science.gov (United States)

    Takizawa, Kenji; Tezduyar, Tayfun E.; Kostov, Nikolay

    2014-08-01

    We present a sequentially-coupled space-time (ST) computational fluid-structure interaction (FSI) analysis of flapping-wing aerodynamics of a micro aerial vehicle (MAV). The wing motion and deformation data, whether prescribed fully or partially, is from an actual locust, extracted from high-speed, multi-camera video recordings of the locust in a wind tunnel. The core computational FSI technology is based on the Deforming-Spatial-Domain/Stabilized ST (DSD/SST) formulation. This is supplemented with using NURBS basis functions in temporal representation of the wing and mesh motion, and in remeshing. Here we use the version of the DSD/SST formulation derived in conjunction with the variational multiscale (VMS) method, and this version is called "DSD/SST-VMST." The structural mechanics computations are based on the Kirchhoff-Love shell model. The sequential-coupling technique is applicable to some classes of FSI problems, especially those with temporally-periodic behavior. We show that it performs well in FSI computations of the flapping-wing aerodynamics we consider here. In addition to the straight-flight case, we analyze cases where the MAV body has rolling, pitching, or rolling and pitching motion. We study how all these influence the lift and thrust.

  11. The mechanics of flight in the hawkmoth Manduca sexta. II. Aerodynamic consequences of kinematic and morphological variation.

    Science.gov (United States)

    Willmott, A P; Ellington, C P

    1997-11-01

    Mean lift coefficients have been calculated for hawkmoth flight at a range of speeds in order to investigate the aerodynamic significance of the kinematic variation which accompanies changes in forward velocity. The coefficients exceed the maximum steady-state value of 0.71 at all except the very fastest speeds, peaking at 2.0 or greater between 1 and 2 ms-1. Unsteady high-lift mechanisms are therefore most important during hovering and slow forward flight. In combination with the wingtip paths relative to the surrounding air, the calculated mean lift coefficients illustrate how the relative contributions of the two halfstrokes to the force balance change with increasing forward speed. Angle of incidence data for fast forward flight suggest that the sense of the circulation is not reversed between the down- and upstrokes, indicating a flight mode qualitatively different from that proposed for lower-speed flight in the hawkmoth and other insects. The mid-downstroke angle of incidence is constant at 30-40 degrees across the speed range. The relationship between power requirements and flight speed is explored; above 5 ms-1, further increases in forward velocity are likely to be constrained by available mechanical power, although problems with thrust generation and flight stability may also be involved. Hawkmoth wing and body morphology, and the differences between males and females, are evaluated in aerodynamic terms. Steady-state force measurements show that the hawkmoth body is amongst the most streamlined for any insect.

  12. Aerodynamics and thermal physics of helicopter ice accretion

    Science.gov (United States)

    Han, Yiqiang

    Ice accretion on aircraft introduces significant loss in airfoil performance. Reduced lift-to- drag ratio reduces the vehicle capability to maintain altitude and also limits its maneuverability. Current ice accretion performance degradation modeling approaches are calibrated only to a limited envelope of liquid water content, impact velocity, temperature, and water droplet size; consequently inaccurate aerodynamic performance degradations are estimated. The reduced ice accretion prediction capabilities in the glaze ice regime are primarily due to a lack of knowledge of surface roughness induced by ice accretion. A comprehensive understanding of the ice roughness effects on airfoil heat transfer, ice accretion shapes, and ultimately aerodynamics performance is critical for the design of ice protection systems. Surface roughness effects on both heat transfer and aerodynamic performance degradation on airfoils have been experimentally evaluated. Novel techniques, such as ice molding and casting methods and transient heat transfer measurement using non-intrusive thermal imaging methods, were developed at the Adverse Environment Rotor Test Stand (AERTS) facility at Penn State. A novel heat transfer scaling method specifically for turbulent flow regime was also conceived. A heat transfer scaling parameter, labeled as Coefficient of Stanton and Reynolds Number (CSR = Stx/Rex --0.2), has been validated against reference data found in the literature for rough flat plates with Reynolds number (Re) up to 1x107, for rough cylinders with Re ranging from 3x104 to 4x106, and for turbine blades with Re from 7.5x105 to 7x106. This is the first time that the effect of Reynolds number is shown to be successfully eliminated on heat transfer magnitudes measured on rough surfaces. Analytical models for ice roughness distribution, heat transfer prediction, and aerodynamics performance degradation due to ice accretion have also been developed. The ice roughness prediction model was

  13. Gyroscopic Stability of Open Tipped Match Style Rifle Bullets

    CERN Document Server

    Courtney, Elya R

    2014-01-01

    Earlier work has produced formulas for predicting stability of rifle bullets of near uniform density and also for plastic-tipped rifle bullets. These formulas have been shown to be accurate to within 5%. However, the original Miller twist formula for metal bullets of near uniform density underestimates the stability of match style open tipped rifle bullets having a significant empty volume in the tip. This paper presents a new formula for accurately estimating the stability of these open tipped match style rifle bullets from parameters easily obtained such as the bullet mass, length, and depth of the empty space in the tip. The formula is tested by measuring the aerodynamic drag vs. predicted stability of several bullets over a range of stabilities.

  14. Aerodynamic Ground Effect in Fruitfly Sized Insect Takeoff.

    Directory of Open Access Journals (Sweden)

    Dmitry Kolomenskiy

    Full Text Available Aerodynamic ground effect in flapping-wing insect flight is of importance to comparative morphologies and of interest to the micro-air-vehicle (MAV community. Recent studies, however, show apparently contradictory results of either some significant extra lift or power savings, or zero ground effect. Here we present a numerical study of fruitfly sized insect takeoff with a specific focus on the significance of leg thrust and wing kinematics. Flapping-wing takeoff is studied using numerical modelling and high performance computing. The aerodynamic forces are calculated using a three-dimensional Navier-Stokes solver based on a pseudo-spectral method with volume penalization. It is coupled with a flight dynamics solver that accounts for the body weight, inertia and the leg thrust, while only having two degrees of freedom: the vertical and the longitudinal horizontal displacement. The natural voluntary takeoff of a fruitfly is considered as reference. The parameters of the model are then varied to explore possible effects of interaction between the flapping-wing model and the ground plane. These modified takeoffs include cases with decreased leg thrust parameter, and/or with periodic wing kinematics, constant body pitch angle. The results show that the ground effect during natural voluntary takeoff is negligible. In the modified takeoffs, when the rate of climb is slow, the difference in the aerodynamic forces due to the interaction with the ground is up to 6%. Surprisingly, depending on the kinematics, the difference is either positive or negative, in contrast to the intuition based on the helicopter theory, which suggests positive excess lift. This effect is attributed to unsteady wing-wake interactions. A similar effect is found during hovering.

  15. Low Speed Aerodynamics of the X-38 CRV

    Science.gov (United States)

    Komerath, N. M.; Funk, R.; Ames, R. G.; Mahalingam, R.; Matos, C.

    1998-01-01

    This project was performed in support of the engineering development of the NASA X-38 Crew Return Vehicle (CRV)system. Wind tunnel experiments were used to visualize various aerodynamic phenomena encountered by the CRV during the final stages of descent and landing. Scale models of the CRV were used to visualize vortex structures above and below the vehicle, and in its wake, and to quantify their trajectories. The effect of flaperon deflection on these structures was studied. The structure and dynamics of the CRV's wake during the drag parachute deployment stage were measured. Regions of high vorticity were identified using surveys conducted in several planes using a vortex meter. Periodic shedding of the vortex sheets from the sides of the CRV was observed using laser sheet videography as the CRV reached high angles of attack during the quasi-steady pitch-up prior to parafoil deployment. Using spectral analysis of hot-film anemometer data, the Strouhal number of these wake fluctuations was found to be 0.14 based on the model span. Phenomena encountered in flight test during parafoil operation were captured in scale-model tests, and a video photogrammetry technique was implemented to obtain parafoil surface shapes during flight in the tunnel. Forces on the parafoil were resolved using tension gages on individual lines. The temporal evolution of the phenomenon of leading edge collapse was captured. Laser velocimetry was used to demonstrate measurement of the porosity of the parafoil surface. From these measurements, several physical explanations have been developed for phenomena observed at various stages of the X-38 development program. Quantitative measurement capabilities have also been demonstrated for continued refinement of the aerodynamic technologies employed in the X-38 project. Detailed results from these studies are given in an AIAA Paper, two slide presentations, and other material which are given on a Web-based archival resource. This is the Digital

  16. Enhanced ground-based vibration testing for aerodynamic environments

    Science.gov (United States)

    Daborn, P. M.; Ind, P. R.; Ewins, D. J.

    2014-12-01

    Typical methods of replicating aerodynamic environments in the laboratory are generally poor. A structure which flies "freely" in its normal operating environment, excited over its entire external surface by aerodynamic forces and in all directions simultaneously, is then subjected to a vibration test in the laboratory whilst rigidly attached to a high impedance shaker and excited by forces applied through a few attachment points and in one direction only. The two environments could hardly be more different. The majority of vibration testing is carried out at commercial establishments and it is understandable that little has been published which demonstrates the limitations with the status quo. The primary objective of this research is to do just that with a view to identifying significant improvements in vibration testing in light of modern technology. In this paper, case studies are presented which highlight some of the limitations with typical vibration tests showing that they can lead to significant overtests, sometimes by many orders of magnitude, with the level of overtest varying considerably across a wide range of frequencies. This research shows that substantial benefits can be gained by "freely" suspending the structure in the laboratory and exciting it with a relatively small number of electrodynamic shakers using Multi-Input-Multi-Output (MIMO) control technology. The shaker configuration can be designed to excite the modes within the bandwidth utilising the inherent amplification of the resonances to achieve the desired response levels. This free-free MIMO vibration test approach is shown to result in substantial benefits that include extremely good replication of the aerodynamic environment and significant savings in time as all axes are excited simultaneously instead of the sequential X, Y and Z testing required with traditional vibration tests. In addition, substantial cost savings can be achieved by replacing some expensive large shaker systems

  17. Study of Aerodynamic Parameters on Different Underling Surfaces

    Institute of Scientific and Technical Information of China (English)

    MAO Yuhao; LIU Shuhua; ZHANG Chenyi; LIU Lichao; LI Jing

    2007-01-01

    Aerodynamic parameters including the zero-plane displacement (d), roughness length (z0), and friction velocity (u*) on the different underlying surfaces of heavy-grazing site, medium-grazing site, light-grazing site, no-grazing site, dune, inter-dune, grassland, rice paddy site, wheat site, soybean site, and maize site have been computed based on the Monin-Obukhov similarity theory by utilizing the micrometeorologically observed data of dune and vegetation in the semi-arid area at Naiman, Inner Mongolia of China, conducted jointly by the Institute of Desert Research, Chinese Academy of Sciences and the National Institute of AgroEnvironmental Sciences of Japan in 1990-1994. And their relationships between wind speed and Richardson number are analyzed. The aerodynamic characteristics of different man-made disturbed grassland ecosystems are also compared. Result shows that the vegetation coverage and the above-ground biomass decrease with the increase in man-made stress of the grassland. The roughness length for different underlying surfaces is closely related to vegetation height, above-ground biomass, and ground surface undulation, and Richardson number Ri is also its influencing factor. The friction velocity varies largely on different underlying surfaces,and it is positively proportional to wind speed and roughness length. The aerodynamic parameters of various times on the same underlying surface are different, too. Above results indicate that grassland and vegetation are of significance in preventing desertification, especially in the arid and semi-arid land ecosystems. And the results of this paper are also important for constructing the land surface physical process as well as regional climate model.

  18. Nonlinear prediction of the aerodynamic loads on lifting surfaces

    Science.gov (United States)

    Kandil, O. A.; Mook, D. T.; Nayfeh, A. H.

    1974-01-01

    A numerical procedure is used to predict the nonlinear aerodynamic characteristics of lifting surfaces of low aspect ratio at high angles of attack for low subsonic Mach numbers. The procedure utilizes a vortex-lattice method and accounts for separation at sharp tips and leading edges. The shapes of the wakes emanating from the edges are predicted, and hence the nonlinear characteristics are calculated. Parallelogram and delta wings are presented as numerical examples. The numerical results are in good agreement with the experimental data.

  19. Evolving aerodynamic airfoils for wind turbines through a genetic algorithm

    Science.gov (United States)

    Hernández, J. J.; Gómez, E.; Grageda, J. I.; Couder, C.; Solís, A.; Hanotel, C. L.; Ledesma, JI

    2017-01-01

    Nowadays, genetic algorithms stand out for airfoil optimisation, due to the virtues of mutation and crossing-over techniques. In this work we propose a genetic algorithm with arithmetic crossover rules. The optimisation criteria are taken to be the maximisation of both aerodynamic efficiency and lift coefficient, while minimising drag coefficient. Such algorithm shows greatly improvements in computational costs, as well as a high performance by obtaining optimised airfoils for Mexico City's specific wind conditions from generic wind turbines designed for higher Reynolds numbers, in few iterations.

  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

    . Experimental measurements consisted of surface pressure data statistics used to infer sectional boundary layer state and to quantify normal force levels. Computed predictions included high-resolution boundary layer topologies and detailed above-surface flow field structures. This synergy was exploited...... 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...

  1. On aerodynamic noise generation from vortex shedding in rotating blades

    Science.gov (United States)

    Martin, B. T.; Bies, D. A.

    1992-06-01

    The interaction of the shed wakes of plates in a cascade with each following plate is investigated in a water tunnel and shown to provide an explanation for an observed very powerful aerodynamic noise source. In particular, the noise generation of an idling circular saw may be explained as due to the interaction of the wake shed by an upstream tooth with the leading edge of the following downstream tooth. When a vortex travelling downstream in the gullet between teeth encounters the leading edge of the downstream tooth it is deflected out of the gullet into the main stream. The associated impulses which the teeth encounter give rise to the radiated noise.

  2. Aerodynamic heating of ballistic missile including the effects of gravity

    Indian Academy of Sciences (India)

    S N Maitra

    2000-10-01

    The aerodynamic heating of a ballistic missile due to only convection is analysed taking into consideration the effects of gravity. The amount of heat transferred to the wetted area and to the nose region has been separately determined, unlike A Miele's treatise without consideration of gravity. The peak heating ratesto the wetted area and to the nose of the missile are also investigated. Finally four numerical examples are cited to estimate the errors, in heat transfers and heating ratesto both wetted area and nose region of the missile, arising out of neglecting the gravitational forces.

  3. Analyze of aerodynamic forces acting on the Siemens Desiro railcar

    Directory of Open Access Journals (Sweden)

    Sorin ARSENE

    2016-06-01

    Full Text Available This paper aims to examine the influence of aerodynamic forces acting on the Siemens Desiro railcar, and the percentage of these forces in the total values of resistance to motion. In this regard the numerical simulation of the airflow is used as a method of analysis. We started from the 3D geometric model at a scale of 1:1 of the vehicle bodywork constructive form. The air flow simulation is performed taking into account the speed limits of the vehicle namely 0 km/ h and 140 km/ h, interval in which eight point values are chosen.

  4. Aerodynamic benchmarking of the DeepWind design

    DEFF Research Database (Denmark)

    Bedon, Gabriele; Schmidt Paulsen, Uwe; Aagaard Madsen, Helge;

    The aerodynamic benchmarking for the DeepWind rotor is conducted comparing different rotor geometries and solutions and keeping the comparison as fair as possible. The objective for the benchmarking is to find the most suitable configuration in order to maximize the power production and minimize...... the blade solicitation and the cost of energy. Different parameters are considered for the benchmarking study. The DeepWind blade is characterized by a shape similar to the Troposkien geometry but asymmetric between the top and bottom parts. The blade shape is considered as a fixed parameter...

  5. Aerodynamic analysis of complex configurations using unstructured grids

    Science.gov (United States)

    Frink, Neal T.; Parikh, Paresh; Pirzadeh, Shahyar

    1991-01-01

    The purpose of this paper is to assess the accuracy and utility of a new unstructured, inviscid, upwind flow solver for the aerodynamic analysis of two aircraft configurations. The two configurations consist of a low-wing transport with nacelle/pylon on and off, and a generic high-speed civil transport. Computations are made at subsonic and transonic Mach numbers for the low-wing transport and at transonic and low-supersonic speeds for the high-speed civil transport. The results include an assessment of grid sensitivity and provide comparisons with experimental data.

  6. An Aerodynamic Investigation of a Forward Swept Wing

    Science.gov (United States)

    1977-12-01

    loads requiring sub- stantial increases in structural weight. With the advent of advanced composites , it is possible to negate these weight penalties...attached flow at higher angles of attack. 59 -. - . -- ~II The use of winglets should-also be considered to determine their effect on the aerodynamic...Advanced Composites , AIAM Paper 76-1009, August, 177T. 5. Lawrence, J.R. Development o± a Half-Span Model Test System For The A FDL-TGF, ContracT F

  7. Wind tunnels as an aerodynamic testing tool in Formula 1

    OpenAIRE

    Martínez Vallés, Carles

    2014-01-01

    This project aims to enable the reader to acquire the necessary knowledge to fully understand the main facts and working principles of modern wind tunnels and their application in F1. In addition one of the goals is to enable the reader to get an insight of the motorsport world, realizing how important aerodynamics are in relation to the global performance and handling of a race car. Throughout the entire project particular emphasis has been made to illustrate the importance of wind tunnels a...

  8. Aerodynamic Optimum Design of Transonic Turbine Cascades Using Genetic Algorithms

    Institute of Scientific and Technical Information of China (English)

    1997-01-01

    This paper presents an aerodynamic optimum design method for transonic turbine cascades based on the Genetic Algorithms coupled to the inviscid flow Euler Solver and the boundary-layer calculation.The Genetic Algorithms control the evolution of a population of cascades towards an optimum design.The fitness value of each string is evaluated using the flow solver.The design procedure has been developed and the behavior of the genetic algorithms has been tested.The objective functions of the design examples are the minimum mean-square deviation between the aimed pressure and computed pressure and the minimum amount of user expertise.

  9. Effect of Moving Surface on NACA 63218 Aerodynamic Performance

    Directory of Open Access Journals (Sweden)

    Yahiaoui Tayeb

    2015-01-01

    Full Text Available The main subject of this work is the numerical study control of flow separation on a NACA 63218 airfoil by using moving surface. Different numerical cases are considered: the first one is the numerical simulation of non-modified airfoil NACA 63218 according at different angle of attack and the second one a set of moving cylinder is placed on leading edge of the airfoil. The rotational velocity of the cylinder is varied to establish the effect of momentum injection on modified airfoil aerodynamic performances. The turbulence is modeled by two equations k-epsilon model.

  10. Wake shape and its effects on aerodynamic characteristics

    Science.gov (United States)

    Emdad, H.; Lan, C. E.

    1986-01-01

    The wake shape under symmetrical flight conditions and its effects on aerodynamic characteristics are examined. In addition, the effect of wake shape in sideslip and discrete vortices such as strake or forebody vortex on lateral characteristics is presented. The present numerical method for airplane configurations, which is based on discretization of the vortex sheet into vortex segments, verified the symmetrical and asymmetrical roll-up process of the trailing vortices. Also, the effect of wing wake on tail planes is calculated. It is concluded that at high lift the assumption of flat wake for longitudinal and lateral-directional characteristics should be reexamined.

  11. A Survey of Theoretical and Experimental Coaxial Rotor Aerodynamic Research

    Science.gov (United States)

    Coleman, Colin P.

    1997-01-01

    The recent appearance of the Kamov Ka-50 helicopter and the application of coaxial rotors to unmanned aerial vehicles have renewed international interest in the coaxial rotor configuration. This report addresses the aerodynamic issues peculiar to coaxial rotors by surveying American, Russian, Japanese, British, and German research. (Herein, 'coaxial rotors' refers to helicopter, not propeller, rotors. The intermeshing rotor system was not investigated.) Issues addressed are separation distance, load sharing between rotors, wake structure, solidity effects, swirl recovery, and the effects of having no tail rotor. A general summary of the coaxial rotor configuration explores the configuration's advantages and applications.

  12. Experimental study on the aerodynamic performance of a Savonius rotor

    Energy Technology Data Exchange (ETDEWEB)

    Fujisawa, Nobuyuki; Gotoh, Futoshi (Gunma Univ., Kiryu (Japan). Dept. of Mechanical Engineering)

    1994-08-01

    The aerodynamic performance of a Savonius rotor has been studied by measuring the pressure distributions on the blade surfaces at various rotor angles and tip-speed ratios. It is found that the pressure distributions on the rotating rotor differ remarkably from those on the still rotor especially on the convex side of the advancing blade, where a low pressure region is formed by the moving wall effect of the blade. The torque and power performances, evaluated by integrating the pressure, are in close agreement with those by the direct torque measurement. The drag and side force performance is also studied.

  13. Variable volume combustor with aerodynamic fuel flanges for nozzle mounting

    Energy Technology Data Exchange (ETDEWEB)

    McConnaughhay, Johnie Franklin; Keener, Christopher Paul; Johnson, Thomas Edward; Ostebee, Heath Michael

    2016-09-20

    The present application provides a combustor for use with a gas turbine engine. The combustor may include a number of micro-mixer fuel nozzles and a fuel injection system for providing a flow of fuel to the micro-mixer fuel nozzles. The fuel injection system may include a number of support struts supporting the fuel nozzles and for providing the flow of fuel therethrough. The fuel injection system also may include a number of aerodynamic fuel flanges connecting the micro-mixer fuel nozzles and the support struts.

  14. Atomic fluorescence study of high temperature aerodynamic levitation

    Science.gov (United States)

    Nordine, P. C.; Schiffman, R. A.; Sethi, D. S.

    1982-01-01

    Ultraviolet laser induced atomic fluorescence has been used to characterize supersonic jet aerodynamic levitation experiments. The levitated specimen was a 0.4 cm sapphire sphere that was separately heated at temperatures up to 2327 K by an infrared laser. The supersonic jet expansion and thermal gradients in the specimen wake were studied by measuring spatial variations in the concentration of atomic Hg added to the levitating argon gas stream. Further applications of atomic fluorescence in containerless experiments, such as ideal gas fluorescence thermometry and containerless process control are discussed.

  15. Improved aerodynamic design of turbomachinery bladings by numerical optimization

    Energy Technology Data Exchange (ETDEWEB)

    Burguburu, St.; Le Pape, A. [Office National d' Etudes et de Recherches Aerospatiales (ONERA), Applied Aerodynamics Dept. 29, 92 - Chatillon (France)

    2003-06-01

    The aerodynamic optimization of a transonic compressor is reported in this paper. The Q3D Navier-Stokes solver COLIBRI is coupled to a gradient-based method (CONMIN) and to a genetic algorithm (GADO). The suction side of a 2-D blade is optimized by using both optimization methods with a significant efficiency improvement. In 3-D, the performance improvement is obtained by modifying the suction surface of a transonic compressor with a Bezier surface and by using the CANARI solver coupled to the gradient method (CONMIN). (authors)

  16. The retrieval of two-dimensional distribution of the earth's surface aerodynamic roughness using SAR image and TM thermal infrared image

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Renhua; WANG; Jinfeng; ZHU; Caiying; SUN; Xiaomin

    2004-01-01

    After having analyzed the requirement on the aerodynamic earth's surface roughness in two-dimensional distribution in the research field of interaction between land surface and atmosphere, this paper presents a new way to calculate the aerodynamic roughness using the earth's surface geometric roughness retrieved from SAR (Synthetic Aperture Radar) and TM thermal infrared image data. On the one hand, the SPM (Small Perturbation Model) was used as a theoretical SAR backscattering model to describe the relationship between the SAR backscattering coefficient and the earth's surface geometric roughness and its dielectric constant retrieved from the physical model between the soil thermal inertia and the soil surface moisture with the simultaneous TM thermal infrared image data and the ground microclimate data. On the basis of the SAR image matching with the TM image, the non-volume scattering surface geometric information was obtained from the SPM model at the TM image pixel scale, and the ground pixel surface's equivalent geometric roughness-height standard RMS (Root Mean Square) was achieved from the geometric information by the transformation of the typical topographic factors. The vegetation (wheat, tree) height retrieved from spectrum model was also transferred into its equivalent geometric roughness. A completely two-dimensional distribution map of the equivalent geometric roughness over the experimental area was produced by the data mosaic technique. On the other hand, according to the atmospheric eddy currents theory, the aerodynamic surface roughness was iterated out with the atmosphere stability correction method using the wind and the temperature profiles data measured at several typical fields such as bare soil field and vegetation field. After having analyzed the effect of surface equivalent geometric roughness together with dynamic and thermodynamic factors on the aerodynamic surface roughness within the working area, this paper first establishes a scale

  17. 折叠机翼展开过程气动特性实验研究%Experimental study of aerodynamic characteristics in floding wings deployment process

    Institute of Scientific and Technical Information of China (English)

    吕胜利; 刘平; 杨广珺; 童小燕

    2013-01-01

    According to the deployment process of high-aspect-ratio UAV floding wings,aerodynamic characteristics is studied on scaled model at different attack angle and different grazing angle for wind tunnel test. Experimental results show that layout of aerodynamic configuration can meet design requirements of cruise,and it has a good stability at vertical and transverse course. Multi-surface combined Fuselage can bring favorable effect on full-aircraft. Characteristic analysis points out the direction of aerodynamic shape optimization. Results can be applied in the research areas of UAV and loiter attack missile.%针对某型无人机大展弦比折叠机翼展开过程,对其缩比模型在不同迎角、不同机翼掠角状态下的气动特性进行了风洞实验.实验结果表明,布局的气动外形满足巡航设计要求,纵向与横航向稳定性较好,多面组合式机身表面可为全机升力带来有利影响,研究结果可在无人机、巡飞导弹等研究领域得到应用.

  18. Numerical study on aerodynamic damping of floating vertical axis wind turbines

    Science.gov (United States)

    Cheng, Zhengshun; Aagaard Madsen, Helge; Gao, Zhen; Moan, Torgeir

    2016-09-01

    Harvesting offshore wind energy resources using floating vertical axis wind turbines (VAWTs) has attracted an increasing interest in recent years. Due to its potential impact on fatigue damage, the aerodynamic damping should be considered in the preliminary design of a floating VAWT based on the frequency domain method. However, currently the study on aerodynamic damping of floating VAWTs is very limited. Due to the essential difference in aerodynamic load characteristics, the aerodynamic damping of a floating VAWT could be different from that of a floating horizontal axis wind turbine (HAWT). In this study, the aerodynamic damping of floating VAWTs was studied in a fully coupled manner, and its influential factors and its effects on the motions, especially the pitch motion, were demonstrated. Three straight-bladed floating VAWTs with identical solidity and with a blade number varying from two to four were considered. The aerodynamic damping under steady and turbulent wind conditions were estimated using fully coupled aero-hydro-servo-elastic time domain simulations. It is found that the aerodynamic damping ratio of the considered floating VAWTs ranges from 1.8% to 5.3%. Moreover, the aerodynamic damping is almost independent of the rotor azimuth angle, and is to some extent sensitive to the blade number.

  19. Some applications of the quasi vortex-lattice method in steady and unsteady aerodynamics

    Science.gov (United States)

    Lan, C. E.

    1976-01-01

    The quasi vortex-lattice method is reviewed and applied to the evaluation of backwash, with applications to ground effect analysis. It is also extended to unsteady aerodynamics, with particular interest in the calculation of unsteady leading-edge suction. Some applications in ornithopter aerodynamics are given.

  20. Integration of CFD and Experimental Results at VKI in Low-Speed Aerodynamic Design

    Science.gov (United States)

    2007-06-01

    erosion in wind tunnel behind the building Today, almost all modern Antartic stations have undergone aerodynamic studies at different stages of design...2] J. Sanz Rodrigo, C. Gorle, J. van Beeck, P. Planquart: Aerodynamic Design of the Princess Elizabeth Antartic Research Station, 17th

  1. The interference aerodynamics caused by the wing elasticity during store separation

    Science.gov (United States)

    Lei, Yang; Zheng-yin, Ye

    2016-04-01

    Air-launch-to-orbit is the technology that has stores carried aloft and launched the store from the plane to the orbit. The separation between the aircraft and store is one of the most important and difficult phases in air-launch-to-orbit technology. There exists strong aerodynamic interference between the aircraft and the store in store separation. When the aspect ratio of the aircraft is large, the elastic deformations of the wing must be considered. The main purpose of this article is to study the influence of the interference aerodynamics caused by the elastic deformations of the wing to the unsteady aerodynamics of the store. By solving the coupled functions of unsteady Navier-Stokes equations, six degrees of freedom dynamic equations and structural dynamic equations simultaneously, the store separation with the elastic deformation of the aircraft considered is simulated numerically. And the interactive aerodynamic forces are analyzed. The study shows that the interference aerodynamics is obvious at earlier time during the separation, and the dominant frequency of the elastic wing determines the aerodynamic forces frequencies of the store. Because of the effect of the interference aerodynamics, the roll angle response and pitch angle response increase. When the store is mounted under the wingtip, the additional aerodynamics caused by the wingtip vortex is obvious, which accelerate the divergence of the lateral force and the lateral-directional attitude angle of the store. This study supports some beneficial conclusions to the engineering application of the air-launch-to-orbit.

  2. Potential impacts of advanced aerodynamic technology on air transportation system productivity

    Science.gov (United States)

    Bushnell, Dennis M. (Editor)

    1994-01-01

    Summaries of a workshop held at NASA Langley Research Center in 1993 to explore the application of advanced aerodynamics to airport productivity improvement are discussed. Sessions included discussions of terminal area productivity problems and advanced aerodynamic technologies for enhanced high lift and reduced noise, emissions, and wake vortex hazard with emphasis upon advanced aircraft configurations and multidisciplinary solution options.

  3. Wind turbine blade vibration at standstill conditions — the effect of imposing lag on the aerodynamic response of an elastically mounted airfoil

    DEFF Research Database (Denmark)

    Skrzypinski, Witold Robert; Gaunaa, Mac

    2015-01-01

    The present study investigated physical phenomena related to stall-induced vibrations potentially existing on wind turbine blades at standstill conditions. The study considered two-dimensional airfoil sections while it omitted three-dimensional effects. In the study, a new engineering-type comput......The present study investigated physical phenomena related to stall-induced vibrations potentially existing on wind turbine blades at standstill conditions. The study considered two-dimensional airfoil sections while it omitted three-dimensional effects. In the study, a new engineering......-type computational model for the aeroelastic response of an elastically mounted airfoil was used to investigate the influence of temporal lag in the aerodynamic response on the aeroelastic stability in deep stall. The study indicated that even a relatively low lag significantly increases the damping of the model...... of the influence of the added mass terms showed that only the pitch-rate and flapwise-acceleration terms have any influence on the stability. An investigation of three different profiles showed that the stability is heavily dependent on the aerodynamic characteristics of the profiles—mainly on the lift...

  4. Aerodynamic properties of six organo-mineral fertiliser particles

    Directory of Open Access Journals (Sweden)

    Marcello Biocca

    2013-09-01

    Full Text Available Agricultural fertilisers are generally applied by means of centrifugal disk spreaders. The machinery, the working conditions and the physical characteristics of fertilizers (including the aerodynamic characteristics of particles may affect the behaviour of particles after the discarding from the spreader. We investigated the aerodynamic properties of organo-mineral fertilisers (a class of slow release fertilisers that are less investigated since they are relatively new in the market using a vertical wind tunnel similar to an elutriator. In the same time, the morphological characteristics of individual fertilizer particles were measured by means of an image analysis procedure. In the study we compare six different fertilisers and we discuss the suitability of the employed methods. The results provide the terminal velocity – Vt – (the velocity value that overcome the gravity force of the particles of the particles, ranging from 8.60 to 9.55 m s-1, and the relationships between Vt and some physical properties (mass, shape, dimensions of the fertilizers. Moreover, the results of field distribution trials show the behaviour of the tested fertilizers during practical use. Such data can contribute to enhance the quality of application of these products in field.

  5. Linear Unsteady Aerodynamic Forces on Vibrating Annular Cascade Blades

    Institute of Scientific and Technical Information of China (English)

    Taketo Nagasaki; Nobuhiko Yamasaki

    2003-01-01

    The paper presents the formulation to compute numerically the unsteady aerodynamic forces on the vibrating annular cascade blades. The formulation is based on the finite volume method. By applying the TVD scheme to the linear unsteady calculations, the precise calculation of the peak of unsteady aerodynamic forces at the shock wave location like the delta function singularity becomes possible without empirical constants. As a further feature of the present paper, results of the present numerical calculation are compared with those of the double lineaxization theory (DLT), which assumes small unsteady and steady disturbances but the unsteady disturbances are much smaller than the steady disturbances. Since DLT requires fax less computational resources than the present numerical calculation, the validation of DLT is quite important from the engineering point of view. Under the conditions of small steady disturbances, a good agreement between these two results is observed, so that the two codes axe cross-validated.The comparison also reveals the limitation on the applicability of DLT.

  6. An aerodynamic performance analysis of a perforated wind turbine blade

    Science.gov (United States)

    Didane, D. H.; Mohd, S.; Subari, Z.; Rosly, N.; Ghafir, M. F. Abdul; Mohd Masrom, M. F.

    2016-11-01

    Wind power is one of the important renewable energy sources. Currently, many researches are focusing on improving the aerodynamic performance of wind turbine blades through simulations and wind tunnel testing. In the present study, the aerodynamic performance of the perforated Eqwin blade (shell type blade) is investigated by using numerical simulation. Three types of slots namely circular, horizontal rectangular and vertical rectangular were evaluated. It was found that the optimum angle of attack for a perforated shell type blade was 12° with maximum Cl/Cd value of 6.420. In general, for all the perforated blade cases, Cl/Cd tended to decrease as the slot size increased except for the circular slot with 5 mm diameter. This was due to the disturbance of the airflow in lower side region which passed through the bigger slot size. Among the modified slots; the circular slot with diameter of 5 mm would be the best slot configuration that can be considered for blade fabrication. The Cl/Cd obtained was 6.46 which is about 5% more than the value of the reference blade. Moreover, the introduced slot would also reduce the overall weight of the blade by 1.3%.

  7. Test section configuration for aerodynamic testing in shock tubes

    Science.gov (United States)

    Cook, W. J.; Presley, L. L.; Chapman, G. T.

    1980-01-01

    This paper presents results of a study of the test section configuration required to minimize or alleviate interference effects on model flow produced by the presence of test section walls in the aerodynamic testing of two dimensional transonic airfoils in a shock tube. Tests at a nominal Mach number of 0.85 and a chord Reynolds number of 2,000,000 were carried out by means of schlieren photography and pressure measurements for several symmetric airfoil profiles using shock tube test sections with unmodified straight walls, contoured walls, and slotted walls with adjacent chambers. Results were compared with corresponding results from conventional wind tunnel tests of the airfoils. Results for the straight wall tests show major airfoil flow distortions. Results from contoured wall tests and those performed using a slotted wall test section developed in this study exhibit essential agreement with wind tunnel results. The collective results show that test sections for aerodynamic testing can be designed for shock tubes that will alleviate wall interference effects.

  8. Preliminary measurements of aerodynamic damping of a transonic compressor rotor

    Science.gov (United States)

    Crawley, E. F.; Kerrebrock, J. L.; Dugundji, J.

    1980-01-01

    The aeroelastic behavior of a transonic compressor rotor operated in the MIT Blowdown Compressor Facility has been examined by means of piezoelectric motion sensors at the base of each of the 23 blades. Excitation has been observed due to rotating stall, due to an incipient flutter, and due to the facility startup transient. A method has been found for determining the aerodynamic damping force by modal analysis of the blade motion. Application of this technique to the example of excitation by rotating stall has led to the conclusions that the blade loading decreases in the stall cell, and that the damping force on the blades in the clean flow is in phase with blade velocity but opposite it in sign, leading to a logarithmic decrement of 0.2. This method of force derivation has quite general applicability as it requires only blade motion data such as are routinely acquired with strain gages. It is argued that models are needed for aerodynamic damping which focus on the effects of near neighbors of a given blade, since flutter often results in large response of isolated blades or small groups of blades.

  9. Unsteady aerodynamics of membrane wings with adaptive compliance

    Science.gov (United States)

    Kiser, Jillian; Breuer, Kenneth

    2016-11-01

    Membrane wings are known to provide superior aerodynamic performance at low Reynolds numbers (Re =104 -105), primarily due to passive shape adaptation to flow conditions. In addition to this passive deformation, active control of the fluid-structure interaction and resultant aerodynamic properties can be achieved through the use of dielectric elastomer actuators as the wing membrane material. When actuated, membrane pretension is decreased and wing camber increases. Additionally, actuation at resonance frequencies allows additional control over wing camber. We present results using synchronized (i) time-resolved particle image velocimetry (PIV) to resolve the flow field, (ii) 3D direct linear transformation (DLT) to recover membrane shape, (iii) lift/drag/torque measurements and (iv) near-wake hot wire anemometry measurements to characterize the fluid-structure interactions. Particular attention is paid to cases in which the vortex shedding frequency, the membrane resonance, and the actuation frequency coincide. In quantitatively examining both flow field and membrane shape at a range of actuation frequencies and vortex shedding frequencies, this work seeks to find actuation parameters that allow for active control of boundary layer separation over a range of flow conditions. Also at Naval Undersea Warfare Center, Division Newport.

  10. Advanced Aerodynamic Technologies for Future Green Regional Aircraft

    Directory of Open Access Journals (Sweden)

    Catalin NAE

    2014-04-01

    Full Text Available Future Green Regional Aircraft (GRA will operate over airports located in the neighborhood of densely populated areas, with high frequency of takeoff/ landing events and, hence, strongly contribute to community noise and gaseous emissions. These issues currently limit further growth of traffic operated by regional airliners which, in the next future, will have to face even more stringent environmental normative worldwide and therefore re-designed to incorporate advanced active aerodynamic technologies. The new concept behind GRA is based on several mainstream technologies: airframe low-noise (LN, aerodynamic load control (LC and load alleviation (LA. These technologies integrate relevant concepts for hybrid and natural laminar flow (HLC/NLF wing, active control of wing movables and aeroelastic tailoring for LC/LA functions, passive means (micro-riblets for turbulent flow drag reduction, innovative gapless architectures (droop nose, morphing flap beside conventional high-lift devices (HLDs, active flow control through synthetic jets, low-noise solutions applied to HLDs (liners, fences, and to fuselage-mounted main and nose landing gears (bay/doors acoustic treatments, fairings, wheels hub cap. The paper deals with the technological readiness level (TRL assessment of the most promising technologies and overall integration in the new generation of GRA, as a highly optimized configuration able to meet requirements for FlighPath 2050.

  11. Aerodynamic interaction between forewing and hindwing of a hovering dragonfly

    Science.gov (United States)

    Hu, Zheng; Deng, Xin-Yan

    2014-12-01

    The phase change between the forewing and hindwing is a distinct feature that sets dragonfly apart from other insects. In this paper, we investigated the aerodynamic effects of varying forewing-hindwing phase difference with a 60° inclined stroke plane during hovering flight. Force measurements on a pair of mechanical wing models showed that in-phase flight enhanced the forewing lift by 17% and the hindwing lift was reduced at most phase differences. The total lift of both wings was also reduced at most phase differences and only increased at a phase range around in-phase. The results may explain the commonly observed behavior of the dragonfly where 0° is employed in acceleration. We further investigated the wing-wing interaction mechanism using the digital particle image velocimetry (PIV) system, and found that the forewing generated a downwash flow which is responsible for the lift reduction on the hindwing. On the other hand, an upwash flow resulted from the leading edge vortex of the hindwing helps to enhance lift on the forewing. The results suggest that the dragonflies alter the phase differences to control timing of the occurrence of flow interactions to achieve certain aerodynamic effects.

  12. Time Series Vegetation Aerodynamic Roughness Fields Estimated from MODIS Observations

    Science.gov (United States)

    Borak, Jordan S.; Jasinski, Michael F.; Crago, Richard D.

    2005-01-01

    Most land surface models used today require estimates of aerodynamic roughness length in order to characterize momentum transfer between the surface and atmosphere. The most common method of prescribing roughness is through the use of empirical look-up tables based solely on land cover class. Theoretical approaches that employ satellite-based estimates of canopy density present an attractive alternative to current look-up table approaches based on vegetation cover type that do not account for within-class variability and are oftentimes simplistic with respect to temporal variability. The current research applies Raupach s formulation of momentum aerodynamic roughness to MODIS data on a regional scale in order to estimate seasonally variable roughness and zero-plane displacement height fields using bulk land cover parameters estimated by [Jasinski, M.F., Borak, J., Crago, R., 2005. Bulk surface momentum parameters for satellite-derived vegetation fields. Agric. For. Meteorol. 133, 55-68]. Results indicate promising advances over look-up approaches with respect to characterization of vegetation roughness variability in land surface and atmospheric circulation models.

  13. Aerodynamic control in compressible flow using microwave driven discharges

    Science.gov (United States)

    McAndrew, Brendan

    A new aerodynamic control scheme based on heating of the free stream flow is developed. The design, construction, and operation of a unique small scale wind tunnel to perform experiments involving this control scheme is detailed. Free stream heating is achieved by means of microwave driven discharges, and the resulting flow perturbations are used to alter the pressure distribution around a model in the flow. The experimental facility is also designed to allow the injection of an electron beam into the free stream for control of the discharge. Appropriate models for the fluid flow and discharge physics are developed, and comparisons of calculations based on those models are made with experimental results. The calculations have also been used to explore trends in parameters beyond the range possible in the experiments. The results of this work have been (1) the development of an operating facility capable of supporting free stream heat addition experiments in supersonic flow, (2) the development of a compatible instrumented model designed to make lift and drag measurements in a low pressure, high electrical noise environment, (3) a theoretical model to predict the change in breakdown threshold in the presence of an electron beam or other source of ionization, and (4) successful demonstration of aerodynamic control using free stream heat addition.

  14. An aerodynamic study on flexed blades for VAWT applications

    Science.gov (United States)

    Micallef, Daniel; Farrugia, Russell; Sant, Tonio; Mollicone, Pierluigi

    2014-12-01

    There is renewed interest in aerodynamics research of VAWT rotors. Lift type, Darrieus designs sometimes use flexed blades to have an 'egg-beater shape' with an optimum Troposkien geometry to minimize the structural stress on the blades. While straight bladed VAWTs have been investigated in depth through both measurements and numerical modelling, the aerodynamics of flexed blades has not been researched with the same level of detail. Two major effects may have a substantial impact on blade performance. First, flexing at the equator causes relatively strong trailing vorticity to be released. Secondly, the blade performance at each station along the blade is influenced by self-induced velocities due to bound vorticity. The latter is not present in a straight bladed configuration. The aim of this research is to investigate these effects in relation to an innovative 4kW wind turbine concept being developed in collaboration with industry known as a self-adjusting VAWT (or SATVAWT). The approach used in this study is based on experimental and numerical work. A lifting line free-wake vortex model was developed. Wind tunnel power and hot-wire velocity measurements were performed on a scaled down, 60cm high, three bladed model in a closed wind tunnel. Results show a substantial axial wake induction at the equator resulting in a lower power generation at this position. This induction increases with increasing degree of flexure. The self-induced velocities caused by blade bound vorticity at a particular station was found to be relatively small.

  15. Design, aerodynamics and autonomy of the DelFly.

    Science.gov (United States)

    de Croon, G C H E; Groen, M A; De Wagter, C; Remes, B; Ruijsink, R; van Oudheusden, B W

    2012-06-01

    One of the major challenges in robotics is to develop a fly-like robot that can autonomously fly around in unknown environments. In this paper, we discuss the current state of the DelFly project, in which we follow a top-down approach to ever smaller and more autonomous ornithopters. The presented findings concerning the design, aerodynamics and autonomy of the DelFly illustrate some of the properties of the top-down approach, which allows the identification and resolution of issues that also play a role at smaller scales. A parametric variation of the wing stiffener layout produced a 5% more power-efficient wing. An experimental aerodynamic investigation revealed that this could be associated with an improved stiffness of the wing, while further providing evidence of the vortex development during the flap cycle. The presented experiments resulted in an improvement in the generated lift, allowing the inclusion of a yaw rate gyro, pressure sensor and microcontroller onboard the DelFly. The autonomy of the DelFly is expanded by achieving (1) an improved turning logic to obtain better vision-based obstacle avoidance performance in environments with varying texture and (2) successful onboard height control based on the pressure sensor.

  16. Introduction to Generalized Functions with Applications in Aerodynamics and Aeroacoustics

    Science.gov (United States)

    Farassat, F.

    1994-01-01

    Generalized functions have many applications in science and engineering. One useful aspect is that discontinuous functions can be handled as easily as continuous or differentiable functions and provide a powerful tool in formulating and solving many problems of aerodynamics and acoustics. Furthermore, generalized function theory elucidates and unifies many ad hoc mathematical approaches used by engineers and scientists. We define generalized functions as continuous linear functionals on the space of infinitely differentiable functions with compact support, then introduce the concept of generalized differentiation. Generalized differentiation is the most important concept in generalized function theory and the applications we present utilize mainly this concept. First, some results of classical analysis, are derived with the generalized function theory. Other applications of the generalized function theory in aerodynamics discussed here are the derivations of general transport theorems for deriving governing equations of fluid mechanics, the interpretation of the finite part of divergent integrals, the derivation of the Oswatitsch integral equation of transonic flow, and the analysis of velocity field discontinuities as sources of vorticity. Applications in aeroacoustics include the derivation of the Kirchhoff formula for moving surfaces, the noise from moving surfaces, and shock noise source strength based on the Ffowcs Williams-Hawkings equation.

  17. Effect of flapping trajectories on the dragonfly aerodynamics

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effects of translational, figure-eight and double-figure-eight flapping trajectories on the dragonfly aerodynamics were numerically studied by solving the Navier-Stokes equations. There is a common characteristic regarding the lift/drag force coefficients that the downstroke flapping provides the lift forces while the upstroke flapping creates the thrust forces for different flapping trajectories. The maximum lift force coefficient exceeds five for the translational trajectory. It is greater than six for the figure-eight and double-figure-eight flapping trajectories, which is sufficiently larger than unity under the steady state flight condition. The ellipse and double-figure-eight flapping trajectories yield the decrease of the lift force, while the figure-eight flapping trajectory yields higher lift force as well as the thrust force than the translational flapping one. During the insect flight, the wing flapping status should be changed instantaneously to satisfy various requirements. Study of the flapping trajectories on the insect aerodynamics is helpful for the design of the Micro-air-vehicles (MAVs).

  18. Screening of the aerodynamic and biophysical properties of barley malt

    Science.gov (United States)

    Ghodsvali, Alireza; Farzaneh, Vahid; Bakhshabadi, Hamid; Zare, Zahra; Karami, Zahra; Mokhtarian, Mohsen; Carvalho, Isabel. S.

    2016-10-01

    An understanding of the aerodynamic and biophysical properties of barley malt is necessary for the appropriate design of equipment for the handling, shipping, dehydration, grading, sorting and warehousing of this strategic crop. Malting is a complex biotechnological process that includes steeping; germination and finally, the dehydration of cereal grains under controlled temperature and humidity conditions. In this investigation, the biophysical properties of barley malt were predicted using two models of artificial neural networks as well as response surface methodology. Stepping time and germination time were selected as the independent variables and 1 000 kernel weight, kernel density and terminal velocity were selected as the dependent variables (responses). The obtained outcomes showed that the artificial neural network model, with a logarithmic sigmoid activation function, presents more precise results than the response surface model in the prediction of the aerodynamic and biophysical properties of produced barley malt. This model presented the best result with 8 nodes in the hidden layer and significant correlation coefficient values of 0.783, 0.767 and 0.991 were obtained for responses one thousand kernel weight, kernel density, and terminal velocity, respectively. The outcomes indicated that this novel technique could be successfully applied in quantitative and qualitative monitoring within the malting process.

  19. 高超声速巡航飞行器纵向气动特性分析%Longitudinal Aerodynamic Characteristics Analysis of Hypersonic Cruise Vehicle

    Institute of Scientific and Technical Information of China (English)

    邢永刚; 唐硕

    2011-01-01

    The airframe integrated nature of the scramjet engine with airbreathing hypersonic cruise vehicle (HCV) results in a strong couplings between aerodynamics and propulsive system. The couplings have an effect on vehicle aerodynamic performance, stability and control. Aiming at the effects, the model of airframe integrated scramjet engine has been developed and aero-propulsion interface separated. Based on the forgoing work,longitudinal aerodynamic characteristics of HCV inlet open, scramjet engine powered and unpowered have been computed separately. Simulation reveals the couplings between aerodynamics and propulsive system and the effect on vehicle characteristics.%吸气式高超声速巡航飞行器机身/发动机一体化特性使得气动一推进系统之间存在强的耦合作用,这种耦合影响着飞行器气动性能、稳定性和控制.针对耦合对飞行器特性的影响,建立了机身一发动机一体化模型,并进行了气动-推进界面划分.在此基础上,分别计算了高超声速巡航飞行器在进气道打开,发动机不工作以及进气道打开,发动机工作两种状态下的纵向气动特性.仿真结果揭示了高超声速巡航飞行器气动一推进系统之间的耦合以及耦合作用对飞行器气动性能、稳定性的影响.

  20. Three-dimensional simulation of slip-streaming in vehicle aerodynamics

    Science.gov (United States)

    Mitra, Saurav

    2013-11-01

    Simulation of slip-streaming in vehicle aerodynamics is computationally challenging. To resolve turbulent wakes, and estimate drag between two co-linear vehicles with less number of computational cells requires advanced techniques. In this study, the variation of drag reduction and increase arising due to different inter-spacing between two Ahmed vehicles bodies (canonical vehicle geometry with 30° slant back angle) are presented. The computational fluid dynamics solver CONVERGE was used, for its automatic mesh refinement (AMR) capabilities. AMR is based on the second derivative of shear and normal components of velocity gradients and was used to resolve the flow around geometric features such as the frontal area, the slant back, etc. Steady-state density-based solver is used where each cell has its own pseudo time-step based on the local numerical stability criterion. The RNG k- ɛ turbulence model was used to model turbulence. The non-dimensional inter-spacing based on vehicle length, was varied from 0.1 to 2.0. The largest grid size used here was 0.04 m and the smallest was 0.005 m to resolve the turbulent wake which is characterized by a strong vortex system, longitudinal counter-rotating vortices arising from the slant back.

  1. Numerical Investigation of Bending-Body Projectile Aerodynamics for Maneuver Control

    Science.gov (United States)

    Youn, Eric; Silton, Sidra

    2015-11-01

    Precision munitions are an active area of research for the U.S. Army. Canard-control actuators have historically been the primary mechanism used to maneuver fin-stabilized, gun-launched munitions. Canards are small, fin-like control surfaces mounted at the forward section of the munition to provide the pitching moment necessary to rotate the body in the freestream flow. The additional lift force due to the rotated body and the canards then alters the flight path toward the intended target. As velocity and maneuverability requirements continue to increase, investigation of other maneuver mechanisms becomes necessary. One option for a projectile with a large length-to-diameter ratio (L/D) is a bending-body design, which imparts a curvature to the projectile body along its axis. This investigation uses full Navier-Stokes computational fluid dynamics simulations to evaluate the effectiveness of an 8-degree bent nose tip on an 8-degree bent forward section of an L/D =10 projectile. The aerodynamic control effectiveness of the bending-body concept is compared to that of a standard L/D =10 straight-body projectile as well as that of the same projectile with traditional canards. All simulations were performed at supersonic velocities between Mach 2-4.

  2. A Synthesis of Hybrid RANS/LES CFD Results for F-16XL Aircraft Aerodynamics

    Science.gov (United States)

    Luckring, James M.; Park, Michael A.; Hitzel, Stephan M.; Jirasek, Adam; Lofthouse, Andrew J.; Morton, Scott A.; McDaniel, David R.; Rizzi, Arthur M.

    2015-01-01

    A synthesis is presented of recent numerical predictions for the F-16XL aircraft flow fields and aerodynamics. The computational results were all performed with hybrid RANS/LES formulations, with an emphasis on unsteady flows and subsequent aerodynamics, and results from five computational methods are included. The work was focused on one particular low-speed, high angle-of-attack flight test condition, and comparisons against flight-test data are included. This work represents the third coordinated effort using the F-16XL aircraft, and a unique flight-test data set, to advance our knowledge of slender airframe aerodynamics as well as our capability for predicting these aerodynamics with advanced CFD formulations. The prior efforts were identified as Cranked Arrow Wing Aerodynamics Project International, with the acronyms CAWAPI and CAWAPI-2. All information in this paper is in the public domain.

  3. Numerical Computations of Transonic Critical AerodynamicBehavior of a Realistic Artillery Projectile

    Directory of Open Access Journals (Sweden)

    Ahmed F. M. Kridi

    2009-01-01

    Full Text Available The determination of aerodynamic coefficients by shell designers is a critical step in the development of any projectile design. Of particular interest is the determination of the aerodynamic coefficients at transonic speeds. It is in this speed regime that the critical aerodynamic behavior occurs and a rapid change in the aerodynamic coefficients is observed. Two-dimensional, transonic, flow field computations over projectiles have been made using Euler equations which were used for solution with no special treatment required. In this work a solution algorithm is based on finite difference MacCormack’s technique for solving mixed subsonic-supersonic flow problem. Details of the asymmetrically located shock waves on the projectiles have been determined. Computed surface pressures have been compared with experimental data and are found to be in good agreement. The pitching moment coefficient, determined from the computed flow fields, shows the critical aerodynamic behavior observed in free flights.

  4. Performance of streamlined bridge decks in relation to the aerodynamics of a flat plate

    DEFF Research Database (Denmark)

    Larose, Guy; Livesey, Flora M.

    1997-01-01

    The aerodynamics of three modern bridge decks are compared to the aerodynamics of a 16:1 flat plate. The comparisons are made on the basis of the analytical evaluation of the performance of each cross-section to the buffeting action of the wind. In general, the closed-box girders studied in this ...... in this paper showed buffeting responses similar to a flat plate with the exception of the multi-box girder which performed much better aerodynamically.......The aerodynamics of three modern bridge decks are compared to the aerodynamics of a 16:1 flat plate. The comparisons are made on the basis of the analytical evaluation of the performance of each cross-section to the buffeting action of the wind. In general, the closed-box girders studied...

  5. Aerodynamic Optimization of an Over-the-Wing-Nacelle-Mount Configuration

    Directory of Open Access Journals (Sweden)

    Daisuke Sasaki

    2011-01-01

    Full Text Available An over-the-wing-nacelle-mount airplane configuration is known to prevent the noise propagation from jet engines toward ground. However, the configuration is assumed to have low aerodynamic efficiency due to the aerodynamic interference effect between a wing and a nacelle. In this paper, aerodynamic design optimization is conducted to improve aerodynamic efficiency to be equivalent to conventional under-the-wing-nacelle-mount configuration. The nacelle and wing geometry are modified to achieve high lift-to-drag ratio, and the optimal geometry is compared with a conventional configuration. Pylon shape is also modified to reduce aerodynamic interference effect. The final wing-fuselage-nacelle model is compared with the DLR F6 model to discuss the potential of Over-the-Wing-Nacelle-Mount geometry for an environmental-friendly future aircraft.

  6. Nonpotential aerodynamics for windmills in shear wind, semi-annual report

    Energy Technology Data Exchange (ETDEWEB)

    Morino, L.

    1975-01-01

    A theoretical formulation is completed and extended to unsteady flows for analysis of lifting-surface Wind Energy Conversion Systems (WECS) aerodynamics. Its formulation is underway. A numerical formulation of Windmill Incompressible Lifting Surface Aerodynamics (WIlSA) is completed. This program is a modification of the program for Incompressible Lifting Surface aerodynamics. WILSA is completed, debugged, and exercised, and the results are detailed in an attachment. The power coefficient is presented as a function of angular speed. The theoretical formulation for the complex-configuration aerodynamic analysis of WECS includes the unsteadiness of the vorticity in the wake. A numerical formulation of the complex program, Windmill Incompressible Complex Configuration Aerodynamics (WICCA), is completed, debugged, and exercised and the results are presented in an attachment. Modification of WICCA for inclusion of the hub is completed and debugged. A completed preliminary simple formulation for inclusion of the boundary layer effects is provided.

  7. Numerical study on aerodynamic damping of floating vertical axis wind turbines

    DEFF Research Database (Denmark)

    Cheng, Zhengshun; Aagaard Madsen, Helge; Gao, Zhen;

    2016-01-01

    Harvesting offshore wind energy resources using floating vertical axis wind turbines (VAWTs) has attracted an increasing interest in recent years. Due to its potential impact on fatigue damage, the aerodynamic damping should be considered in the preliminary design of a floating VAWT based...... on the frequency domain method. However, currently the study on aerodynamic damping of floating VAWTs is very limited. Due to the essential difference in aerodynamic load characteristics, the aerodynamic damping of a floating VAWT could be different from that of a floating horizontal axis wind turbine (HAWT......). In this study, the aerodynamic damping of floating VAWTs was studied in a fully coupled manner, and its influential factors and its effects on the motions, especially the pitch motion, were demonstrated. Three straight-bladed floating VAWTs with identical solidity and with a blade number varying from two...

  8. PARALLEL STABILIZATION

    Institute of Scientific and Technical Information of China (English)

    J.L.LIONS

    1999-01-01

    A new algorithm for the stabilization of (possibly turbulent, chaotic) distributed systems, governed by linear or non linear systems of equations is presented. The SPA (Stabilization Parallel Algorithm) is based on a systematic parallel decomposition of the problem (related to arbitrarily overlapping decomposition of domains) and on a penalty argument. SPA is presented here for the case of linear parabolic equations: with distrjbuted or boundary control. It extends to practically all linear and non linear evolution equations, as it will be presented in several other publications.

  9. Macroeconomic stability

    DEFF Research Database (Denmark)

    Jespersen, Jesper

    2004-01-01

    It is demonstrated that full employment and sustainable development not necessarily are conflicting goals. On the other hand macroeconomic stability cannot be obtained without a deliberate labour sharing policy and a shift in the composition of private consumption away from traditional material...

  10. Stability investigation of an airfoil section with active flap control

    DEFF Research Database (Denmark)

    Bergami, Leonardo; Gaunaa, Mac

    2010-01-01

    This work presents a method to determine flutter and divergence instability limits for a two-dimensional (2-D) airfoil section fitted with an actively controlled trailing edge flap. This flap consists of a deformable trailing edge, which deformation is governed by control algorithms based...... for fatigue load alleviation. The structural model of the 2-D airfoil section contains three degrees of freedom: heave translation, pitch rotation and flap deflection. A potential flow model provides the aerodynamic forces and their distribution. The unsteady aerodynamics are described using an indicial...... function approximation. Stability of the full aeroservoelastic system is determined through eigenvalue analysis by state-space formulation of the indicial approximation. Validation is carried out against an implementation of the recursive method by Theodorsen and Garrick for flexure-torsion-aileron flutter...

  11. What can be learned from birds for achieving directional stability without a fin

    Science.gov (United States)

    Sachs, Gottfried

    2012-11-01

    Flight mechanics characteristics concerning static and dynamic directional stability in birds are subject of this treatment. It is shown how directional stability is influenced by the elements of the aerodynamic configuration (wing, body, horizontal tail) where issues of static stability in terms of a restoring moment capability are dealt with. A modern and efficient aerodynamic method for modeling the fluid flow around complex geometries and for computing forces and moments with high precision was used to obtain results on the stability characteristics. Concerning a quantitative as-sessment of directional stability characteristics, rotary dynamics with respect to the yaw axis are considered. For this purpose, the frequency of the dutch roll is regarded as an appropriate measure of dynamic directional stability. With ref-erence to aircraft experience, requirements on adequate restoring characteristics in the yaw axis are used. In an expanded treatment of dynamic directional stability, coupling effects between the yaw and roll axes are also considered. It turns out that these can yield a significant contribution to dynamic directional stability. Based on the derived results, it is shown that aerial vehicles the mass of which is comparable with that of birds can have adequate dynamic directional sta-bility characteristics in terms of an appropriate dutch roll frequency level without needing a fin.

  12. The influence of flight style on the aerodynamic properties of avian wings as fixed lifting surfaces

    Directory of Open Access Journals (Sweden)

    John J. Lees

    2016-10-01

    Full Text Available The diversity of wing morphologies in birds reflects their variety of flight styles and the associated aerodynamic and inertial requirements. Although the aerodynamics underlying wing morphology can be informed by aeronautical research, important differences exist between planes and birds. In particular, birds operate at lower, transitional Reynolds numbers than do most aircraft. To date, few quantitative studies have investigated the aerodynamic performance of avian wings as fixed lifting surfaces and none have focused upon the differences between wings from different flight style groups. Dried wings from 10 bird species representing three distinct flight style groups were mounted on a force/torque sensor within a wind tunnel in order to test the hypothesis that wing morphologies associated with different flight styles exhibit different aerodynamic properties. Morphological differences manifested primarily as differences in drag rather than lift. Maximum lift coefficients did not differ between groups, whereas minimum drag coefficients were lowest in undulating flyers (Corvids. The lift to drag ratios were lower than in conventional aerofoils and data from free-flying soaring species; particularly in high frequency, flapping flyers (Anseriformes, which do not rely heavily on glide performance. The results illustrate important aerodynamic differences between the wings of different flight style groups that cannot be explained solely by simple wing-shape measures. Taken at face value, the results also suggest that wing-shape is linked principally to changes in aerodynamic drag, but, of course, it is aerodynamics during flapping and not gliding that is likely to be the primary driver.

  13. The influence of flight style on the aerodynamic properties of avian wings as fixed lifting surfaces

    Science.gov (United States)

    Dimitriadis, Grigorios; Nudds, Robert L.

    2016-01-01

    The diversity of wing morphologies in birds reflects their variety of flight styles and the associated aerodynamic and inertial requirements. Although the aerodynamics underlying wing morphology can be informed by aeronautical research, important differences exist between planes and birds. In particular, birds operate at lower, transitional Reynolds numbers than do most aircraft. To date, few quantitative studies have investigated the aerodynamic performance of avian wings as fixed lifting surfaces and none have focused upon the differences between wings from different flight style groups. Dried wings from 10 bird species representing three distinct flight style groups were mounted on a force/torque sensor within a wind tunnel in order to test the hypothesis that wing morphologies associated with different flight styles exhibit different aerodynamic properties. Morphological differences manifested primarily as differences in drag rather than lift. Maximum lift coefficients did not differ between groups, whereas minimum drag coefficients were lowest in undulating flyers (Corvids). The lift to drag ratios were lower than in conventional aerofoils and data from free-flying soaring species; particularly in high frequency, flapping flyers (Anseriformes), which do not rely heavily on glide performance. The results illustrate important aerodynamic differences between the wings of different flight style groups that cannot be explained solely by simple wing-shape measures. Taken at face value, the results also suggest that wing-shape is linked principally to changes in aerodynamic drag, but, of course, it is aerodynamics during flapping and not gliding that is likely to be the primary driver.

  14. Sparse polynomial surrogates for aerodynamic computations with random inputs

    CERN Document Server

    Savin, Eric; Peter, Jacques

    2015-01-01

    This paper deals with some of the methodologies used to construct polynomial surrogate models based on generalized polynomial chaos (gPC) expansions for applications to uncertainty quantification (UQ) in aerodynamic computations. A core ingredient in gPC expansions is the choice of a dedicated sampling strategy, so as to define the most significant scenarios to be considered for the construction of such metamodels. A desirable feature of the proposed rules shall be their ability to handle several random inputs simultaneously. Methods to identify the relative "importance" of those variables or uncertain data shall be ideally considered as well. The present work is more particularly dedicated to the development of sampling strategies based on sparsity principles. Sparse multi-dimensional cubature rules based on general one-dimensional Gauss-Jacobi-type quadratures are first addressed. These sets are non nested, but they are well adapted to the probability density functions with compact support for the random in...

  15. Numerical study on aerodynamic heat of hypersonic flight

    Directory of Open Access Journals (Sweden)

    Huang Haiming

    2016-01-01

    Full Text Available Accurate prediction of the shock wave has a significant effect on the development of space transportation vehicle or exploration missions. Taking Lobb sphere as the example, the aerodynamic heat of hypersonic flight in different Mach numbers is simulated by the finite volume method. Chemical reactions and non-equilibrium heat are taken into account in this paper, where convective flux of the space term adopts the Roe format, and discretization of the time term is achieved by backward Euler algorithm. The numerical results reveal that thick mesh can lead to accurate prediction, and the thickness of the shock wave decreases as grid number increases. Furthermore, most of kinetic energy converts into internal energy crossing the shock wave.

  16. Computational Hypersonic Aerodynamics with Emphasis on Earth Reentry Capsules

    Directory of Open Access Journals (Sweden)

    Mihai Leonida NICULESCU

    2016-09-01

    Full Text Available The temperature in the front region of a hypersonic vehicle nose can be extremely high, for example, reaching approximately 11 000 K at a Mach number of 36 (Apollo reentry due to the bow shock wave. In this case, accurate prediction of temperature behind the shock wave is necessary in order to precisely estimate the wall heat flux. A better prediction of wall heat flux leads to smaller safety coefficient for thermal shield of space reentry vehicle; therefore, the size of thermal shield decreases and the payload could increase. However, the accurate prediction of temperature behind the bow shock wave implies the use of a precise chemical model whose partial differential equations are added to Navier-Stokes equations. This second order partial differential system is very difficult to be numerically integrated. For this reason, the present paper deals with the computational hypersonic aerodynamics with chemical reactions with the aim of supporting Earth reentry capsule design.

  17. Scientific visualization in computational aerodynamics at NASA Ames Research Center

    Science.gov (United States)

    Bancroft, Gordon V.; Plessel, Todd; Merritt, Fergus; Walatka, Pamela P.; Watson, Val

    1989-01-01

    The visualization methods used in computational fluid dynamics research at the NASA-Ames Numerical Aerodynamic Simulation facility are examined, including postprocessing, tracking, and steering methods. The visualization requirements of the facility's three-dimensional graphical workstation are outlined and the types hardware and software used to meet these requirements are discussed. The main features of the facility's current and next-generation workstations are listed. Emphasis is given to postprocessing techniques, such as dynamic interactive viewing on the workstation and recording and playback on videodisk, tape, and 16-mm film. Postprocessing software packages are described, including a three-dimensional plotter, a surface modeler, a graphical animation system, a flow analysis software toolkit, and a real-time interactive particle-tracer.

  18. Instrumentation Development for Large Scale Hypersonic Inflatable Aerodynamic Decelerator Characterization

    Science.gov (United States)

    Swanson, Gregory T.; Cassell, Alan M.

    2011-01-01

    Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology is currently being considered for multiple atmospheric entry applications as the limitations of traditional entry vehicles have been reached. The Inflatable Re-entry Vehicle Experiment (IRVE) has successfully demonstrated this technology as a viable candidate with a 3.0 m diameter vehicle sub-orbital flight. To further this technology, large scale HIADs (6.0 8.5 m) must be developed and tested. To characterize the performance of large scale HIAD technology new instrumentation concepts must be developed to accommodate the flexible nature inflatable aeroshell. Many of the concepts that are under consideration for the HIAD FY12 subsonic wind tunnel test series are discussed below.

  19. Aerodynamics of a single-degree-of-freedom toy ornithopter

    Science.gov (United States)

    Chavez Alarcon, Ramiro; Balakumar, B. J.; Allen, James J.

    2009-11-01

    The flow field around a flight-worthy toy ornithopter is investigated using PIV diagnostics in combination with load cells to understand the aerodynamics during nominally steady flight and turning. Phase-locked measurements of the wake and inflow are performed using an automated PIV system around the flapping wings of the ornithopter with the ornithopter fixed to a load-cell inside a 1.3m x 1.2m wind tunnel test section. The mildly oscillating free flight of the ornithopter is compared to the wake measurements to understand the causes of the unsteadiness. Further, the modulation of the wake that causes the turning motion of the ornithopter is explained using the wake structure measurements.

  20. International Symposium on Recent Advances in Aerodynamics and Acoustics

    CERN Document Server

    Smith, Charles

    1986-01-01

    The Joint Institute for Aeronautics and Acoustics at Stanford University was established in October 1973 to provide an academic environment for long-term cooperative research between Stanford and NASA Ames Research Center. Since its establishment, the Institute has conducted theoretical and experimental work in the areas of aerodynamics, acoustics, fluid mechanics, flight dynamics, guidance and control, and human factors. This research has involved Stanford faculty, research associates, graduate students, and many distinguished visitors in collaborative efforts with the research staff of NASA Ames Research Center. The occasion of the Institute's tenth anniversary was used to reflect back on where that research has brought us, and to consider where our endeavors should be directed next. Thus, an International Symposium was held to review recent advances in the fields relevant to the activities of the Institute and to discuss the areas of research to be undertaken in the future. This anniversary was also chosen...

  1. Instability of water jet: Aerodynamically induced acoustic and capillary waves

    Science.gov (United States)

    Broman, Göran I.; Rudenko, Oleg V.

    2012-09-01

    High-speed water jet cutting has important industrial applications. To further improve the cutting performance it is critical to understand the theory behind the onset of instability of the jet. In this paper, instability of a water jet flowing out from a nozzle into ambient air is studied. Capillary forces and compressibility of the liquid caused by gas bubbles are taken into account, since these factors have shown to be important in previous experimental studies. A new dispersion equation, generalizing the analogous Rayleigh equation, is derived. It is shown how instability develops because of aerodynamic forces that appear at the streamlining of an initial irregularity of the equilibrium shape of the cross-section of the jet and how instability increases with increased concentration of gas bubbles. It is also shown how resonance phenomena are responsible for strong instability. On the basis of the theoretical explanations given, conditions for stable operation are indicated.

  2. Genetic Algorithms Applied to Multi-Objective Aerodynamic Shape Optimization

    Science.gov (United States)

    Holst, Terry L.

    2005-01-01

    A genetic algorithm approach suitable for solving multi-objective problems is described and evaluated using a series of aerodynamic shape optimization problems. Several new features including two variations of a binning selection algorithm and a gene-space transformation procedure are included. The genetic algorithm is suitable for finding Pareto optimal solutions in search spaces that are defined by any number of genes and that contain any number of local extrema. A new masking array capability is included allowing any gene or gene subset to be eliminated as decision variables from the design space. This allows determination of the effect of a single gene or gene subset on the Pareto optimal solution. Results indicate that the genetic algorithm optimization approach is flexible in application and reliable. The binning selection algorithms generally provide Pareto front quality enhancements and moderate convergence efficiency improvements for most of the problems solved.

  3. The Aerodynamics of Deforming Wings at Low Reynolds Number

    Science.gov (United States)

    Medina, Albert

    Flapping flight has gained much attention in the past decade driven by the desire to understand capabilities observed in nature and the desire to develop agile small-scale aerial vehicles. Advancing our current understanding of unsteady aerodynamics is an essential component in the development of micro-air vehicles (MAV) intended to utilize flight mechanics akin to insect flight. Thus the efforts undertaken that of bio-mimicry. The complexities of insect wing motion are dissected and simplified to more tractable problems to elucidate the fundamentals of unsteady aerodynamics in biologically inspired kinematics. The MAV's fruition would satisfy long established needs in both the military and civilian sectors. Although recent studies have provided great insight into the lift generating mechanisms of flapping wings the deflection response of such wings remains poorly understood. This dissertation numerically and experimentally investigates the aerodynamic performance of passively and actively deflected wings in hover and rotary kinematics. Flexibility is distilled to discrete lines of flexion which acknowledging major flexion lines in insect wings to be the primary avenue for deformation. Of primary concern is the development of the leading-edge vortex (LEV), a high circulation region of low pressure above the wing to which much of the wing's lift generation is attributed. Two-dimensional simulations of wings with chord-wise flexibility in a freestream reveal a lift generating mechanism unavailable to rigid wings with origins in vortical symmetry breaking. The inclusion of flexibility in translating wings accelerated from rest revealed the formation time of the initial LEV was very weakly dependent on the flexible stiffness of the wing, maintaining a universal time scale of four to five chords of travel before shedding. The frequency of oscillatory shedding of the leading and trailing-edge vortices that develops after the initial vortex shedding was shown to be

  4. Small, high pressure ratio compressor: Aerodynamic and mechanical design

    Science.gov (United States)

    Bryce, C. A.; Erwin, J. R.; Perrone, G. L.; Nelson, E. L.; Tu, R. K.; Bosco, A.

    1973-01-01

    The Small, High-Pressure-Ratio Compressor Program was directed toward the analysis, design, and fabrication of a centrifugal compressor providing a 6:1 pressure ratio and an airflow rate of 2.0 pounds per second. The program consists of preliminary design, detailed areodynamic design, mechanical design, and mechanical acceptance tests. The preliminary design evaluate radial- and backward-curved blades, tandem bladed impellers, impeller-and diffuser-passage boundary-layer control, and vane, pipe, and multiple-stage diffusers. Based on this evaluation, a configuration was selected for detailed aerodynamic and mechanical design. Mechanical acceptance test was performed to demonstrate that mechanical design objectives of the research package were met.

  5. Influence of a humidor on the aerodynamics of baseballs

    CERN Document Server

    Meyer, Edmund

    2007-01-01

    We investigate whether storing baseballs in a controlled humidity environment significantly affects their aerodynamic properties. To do this, we measure the change in diameter and mass of baseballs as a function of relative humidity (RH). We then model trajectories for pitched and batted baseballs to assess the difference between those stored at 30% RH versus 50% RH. The results show that a drier baseball may be expected to curve slightly more than a humidified one, and that the drier ball will also likely travel slightly less far when batted. We discuss consequences of these results for baseball played at Coors Field in Denver, where baseballs have been stored in a humidor at 50% RH since 2002.

  6. Aerodynamic analysis of flapping foils using volume grid deformation code

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Jin Hwan [Seoul National University, Seoul (Korea, Republic of); Kim, Jee Woong; Park, Soo Hyung; Byun, Do Young [Konkuk University, Seoul (Korea, Republic of)

    2009-06-15

    Nature-inspired flapping foils have attracted interest for their high thrust efficiency, but the large motions of their boundaries need to be considered. It is challenging to develop robust, efficient grid deformation algorithms appropriate for the large motions in three dimensions. In this paper, a volume grid deformation code is developed based on finite macro-element and transfinite interpolation, which successfully interfaces to a structured multi-block Navier-Stokes code. A suitable condition that generates the macro-elements with efficiency and improves the robustness of grid regularity is presented as well. As demonstrated by an airfoil with various motions related to flapping, the numerical results of aerodynamic forces by the developed method are shown to be in good agreement with those of an experimental data or a previous numerical solution

  7. A Computational Model for Rotor-Fuselage Interactional Aerodynamics

    Science.gov (United States)

    Boyd, D. Douglas, Jr.; Barnwell, Richard W.; Gorton, Susan Althoff

    2000-01-01

    A novel unsteady rotor-fuselage interactional aerodynamics model has been developed. This model loosely couples a Generalized Dynamic Wake Theory (GDWT) to a thin-layer Navier-Stokes solution procedure. This coupling is achieved using an unsteady pressure jump boundary condition in the Navier-Stokes model. The new unsteady pressure jump boundary condition models each rotor blade as a moving pressure jump which travels around the rotor azimuth and is applied between two adjacent planes in a cylindrical, non-rotating grid. Comparisons are made between measured and predicted time-averaged and time-accurate rotor inflow ratios. Additional comparisons are made between measured and predicted unsteady surface pressures on the top centerline and sides of the fuselage.

  8. Aerodynamics of thrust vectoring by Navier-Stokes solutions

    Science.gov (United States)

    Tseng, Jing-Biau; Lan, C. Edward

    1991-01-01

    Induced aerodynamics from thrust vectoring are investigated by a computational fluid dynamic method. A thin-layer Reynolds-averaged Navier-Stokes code with multiblock capability is used. Jet properties are specified on the nozzle exit plane to simulate the jet momentum. Results for a rectangular jet in a cross flow are compared with data to verify the code. Further verification of the calculation is made by comparing the numerical results with transonic data for a wing-body combination. Additional calculations were performed to elucidate the following thrust vectoring effects: the thrust vectoring effect on shock and expansion waves, induced effects on nearby surfaces, and the thrust vectoring effect on the leading edge vortex.

  9. Survey of research on unsteady aerodynamic loading of delta wings

    Science.gov (United States)

    Ashley, H.; Vaneck, T.; Katz, J.; Jarrah, M. A.

    1991-01-01

    For aeronautical applications, there has been recent interest in accurately determining the aerodynamic forces and moments experienced by low-aspect-ratio wings performing transient maneuvers which go to angles of attack as high as 90 deg. Focusing on the delta planform with sharp leading edges, the paper surveys experimental and theoretical investigations dealing with the associated unsteady flow phenomena. For maximum angles above a value between 30 and 40 deg, flow details and airloads are dominated by hysteresis in the 'bursting' instability of intense vortices which emanate from the leading edge. As examples of relevant test results, force and moment histories are presented for a model series with aspect ratios 1, 1.5 and 2. Influences of key parameters are discussed, notably those which measure unsteadiness. Comparisons are given with two theories: a paneling approximation that cannot capture bursting but clarifies other unsteady influences, and a simplified estimation scheme which uses measured bursting data.

  10. Aerodynamic Heat-Power Engine Operating on a Closed Cycle

    Science.gov (United States)

    Ackeret, J.; Keller, D. C.

    1942-01-01

    Hot-air engines with dynamic compressors and turbines offer new prospects of success through utilization of units of high efficiencies and through the employment of modern materials of great strength at high temperature. Particular consideration is given to an aerodynamic prime mover operating on a closed circuit and heated externally. Increase of the pressure level of the circulating air permits a great increase of limit load of the unit. This also affords a possibility of regulation for which the internal efficiency of the unit changes but slightly. The effect of pressure and temperature losses is investigated. A general discussion is given of the experimental installation operating at the Escher Wyss plant in Zurich for a considerable time at high temperatures.

  11. Aerodynamic performance prediction of Darrieus-type wind turbines

    Directory of Open Access Journals (Sweden)

    Ion NILĂ

    2010-06-01

    Full Text Available The prediction of Darrieus wind turbine aerodynamic performances provides the necessarydesign and operational data base related to the wind potential. In this sense it provides the type ofturbine suitable to the area where it is to be installed. Two calculation methods are analyzed for arotor with straight blades. The first one is a global method that allows an assessment of the turbinenominal power by a brief calculation. This method leads to an overestimation of performances. Thesecond is the calculation method of the gust factor and momentum which deals with the pale as beingcomposed of different elements that don’t influence each other. This method, developed based on thetheory of the turbine blades, leads to values close to the statistical data obtained experimentally. Thevalues obtained by the calculation method of gust factor - momentum led to the concept of a Darrieusturbine, which will be tested for different wind values in the INCAS subsonic wind tunnel.

  12. Aerodynamic investigation of winglets on wind turbine blades using CFD

    DEFF Research Database (Denmark)

    Johansen, Jeppe; Sørensen, Niels N.

    2006-01-01

    The present report describes the numerical investigation of the aerodynamics around a wind turbine blade with a winglet using Computational Fluid Dynamics, CFD. Five winglets were investigated with different twist distribution and camber. Four of them were pointing towards the pressure side...... (upstream) and one was pointing towards the suction side (downstream). Additionally, a rectangular modification of the original blade tip was designed with the same planform area as the blades with winglets. Results show that adding a winglet to the existing blade increase the force distribution...... on the outer approx 14 % of the blade leading to increased produced power of around 0.6% to 1.4% for wind speeds larger than 6 m/s. This has to be compared to the increase in thrust of around 1.0% to 1.6%. Pointing the winglet downstream increases the power production even further. The effect of sweep and cant...

  13. Team Software Development for Aerothermodynamic and Aerodynamic Analysis and Design

    Science.gov (United States)

    Alexandrov, N.; Atkins, H. L.; Bibb, K. L.; Biedron, R. T.; Carpenter, M. H.; Gnoffo, P. A.; Hammond, D. P.; Jones, W. T.; Kleb, W. L.; Lee-Rausch, E. M.

    2003-01-01

    A collaborative approach to software development is described. The approach employs the agile development techniques: project retrospectives, Scrum status meetings, and elements of Extreme Programming to efficiently develop a cohesive and extensible software suite. The software product under development is a fluid dynamics simulator for performing aerodynamic and aerothermodynamic analysis and design. The functionality of the software product is achieved both through the merging, with substantial rewrite, of separate legacy codes and the authorship of new routines. Examples of rapid implementation of new functionality demonstrate the benefits obtained with this agile software development process. The appendix contains a discussion of coding issues encountered while porting legacy Fortran 77 code to Fortran 95, software design principles, and a Fortran 95 coding standard.

  14. A Rapid Aerodynamic Design Procedure Based on Artificial Neural Networks

    Science.gov (United States)

    Rai, Man Mohan

    2001-01-01

    An aerodynamic design procedure that uses neural networks to model the functional behavior of the objective function in design space has been developed. This method incorporates several improvements to an earlier method that employed a strategy called parameter-based partitioning of the design space in order to reduce the computational costs associated with design optimization. As with the earlier method, the current method uses a sequence of response surfaces to traverse the design space in search of the optimal solution. The new method yields significant reductions in computational costs by using composite response surfaces with better generalization capabilities and by exploiting synergies between the optimization method and the simulation codes used to generate the training data. These reductions in design optimization costs are demonstrated for a turbine airfoil design study where a generic shape is evolved into an optimal airfoil.

  15. Subsonic potential aerodynamics for complex configurations - A general theory

    Science.gov (United States)

    Morino, L.; Kuo, C.-C.

    1974-01-01

    A general theory of subsonic potential aerodynamic flow around a lifting body having arbitrary shape and motion is presented. By using the Green function method, an integral representation for the velocity potential is obtained for both supersonic and subsonic flow. Under the small perturbation assumption, the potential at any point in the field depends only upon the values of the potential and its normal derivative on the surface of the body. On the surface of the body, this representation reduces to an integro-differential equation relating the potential and its normal derivative (which is known from the boundary conditions) on the surface. The theory is applied to finite-thickness wings in subsonic steady and oscillatory flows.

  16. Finding the Force -- Consistent Particle Seeding for Satellite Aerodynamics

    CERN Document Server

    Parham, J Brent

    2013-01-01

    When calculating satellite trajectories in low-earth orbit, engineers need to adequately estimate aerodynamic forces. But to this day, obtaining the drag acting on the complicated shapes of modern spacecraft suffers from many sources of error. While part of the problem is the uncertain density in the upper atmosphere, this works focuses on improving the modeling of interacting rarified gases and satellite surfaces. The only numerical approach that currently captures effects in this flow regime---like self-shadowing and multiple molecular reflections---is known as test-particle Monte Carlo. This method executes a ray-tracing algorithm to follow particles that pass through a control volume containing the spacecraft and accumulates the momentum transfer to the body surfaces. Statistical fluctuations inherent in the approach demand particle numbers in the order of millions, often making this scheme too costly to be practical. This work presents a parallel test-particle Monte Carlo method that takes advantage of b...

  17. A parallel finite-difference method for computational aerodynamics

    Science.gov (United States)

    Swisshelm, Julie M.

    1989-01-01

    A finite-difference scheme for solving complex three-dimensional aerodynamic flow on parallel-processing supercomputers is presented. The method consists of a basic flow solver with multigrid convergence acceleration, embedded grid refinements, and a zonal equation scheme. Multitasking and vectorization have been incorporated into the algorithm. Results obtained include multiprocessed flow simulations from the Cray X-MP and Cray-2. Speedups as high as 3.3 for the two-dimensional case and 3.5 for segments of the three-dimensional case have been achieved on the Cray-2. The entire solver attained a factor of 2.7 improvement over its unitasked version on the Cray-2. The performance of the parallel algorithm on each machine is analyzed.

  18. Estimation of unsteady aerodynamic forces using pointwise velocity data

    CERN Document Server

    Gómez, F; Blackburn, H M

    2016-01-01

    A novel method to estimate unsteady aerodynamic force coefficients from pointwise velocity measurements is presented. The methodology is based on a resolvent-based reduced-order model which requires the mean flow to obtain physical flow structures and pointwise measurement to calibrate their amplitudes. A computationally-affordable time-stepping methodology to obtain resolvent modes in non-trivial flow domains is introduced and compared to previous existing matrix-free and matrix-forming strategies. The technique is applied to the unsteady flow around an inclined square cylinder at low Reynolds number. The potential of the methodology is demonstrated through good agreement between the fluctuating pressure distribution on the cylinder and the temporal evolution of the unsteady lift and drag coefficients predicted by the model and those computed by direct numerical simulation.

  19. Application of surrogate-based global optimization to aerodynamic design

    CERN Document Server

    Pérez, Esther

    2016-01-01

    Aerodynamic design, like many other engineering applications, is increasingly relying on computational power. The growing need for multi-disciplinarity and high fidelity in design optimization for industrial applications requires a huge number of repeated simulations in order to find an optimal design candidate. The main drawback is that each simulation can be computationally expensive – this becomes an even bigger issue when used within parametric studies, automated search or optimization loops, which typically may require thousands of analysis evaluations. The core issue of a design-optimization problem is the search process involved. However, when facing complex problems, the high-dimensionality of the design space and the high-multi-modality of the target functions cannot be tackled with standard techniques. In recent years, global optimization using meta-models has been widely applied to design exploration in order to rapidly investigate the design space and find sub-optimal solutions. Indeed, surrogat...

  20. Advanced multistage turbine blade aerodynamics, performance, cooling, and heat transfer

    Energy Technology Data Exchange (ETDEWEB)

    Fleeter, S.; Lawless, P.B. [Purdue Univ., West Lafayette, IN (United States)

    1995-10-01

    The gas turbine has the potential for power production at the highest possible efficiency. The challenge is to ensure that gas turbines operate at the optimum efficiency so as to use the least fuel and produce minimum emissions. A key component to meeting this challenge is the turbine. Turbine performance, both aerodynamics and heat transfer, is one of the barrier advanced gas turbine development technologies. This is a result of the complex, highly three-dimensional and unsteady flow phenomena in the turbine. Improved turbine aerodynamic performance has been achieved with three-dimensional highly-loaded airfoil designs, accomplished utilizing Euler or Navier-Stokes Computational Fluid Dynamics (CFD) codes. These design codes consider steady flow through isolated blade rows. Thus they do not account for unsteady flow effects. However, unsteady flow effects have a significant impact on performance. Also, CFD codes predict the complete flow field. The experimental verification of these codes has traditionally been accomplished with point data - not corresponding plane field measurements. Thus, although advanced CFD predictions of the highly complex and three-dimensional turbine flow fields are available, corresponding data are not. To improve the design capability for high temperature turbines, a detailed understanding of the highly unsteady and three-dimensional flow through multi-stage turbines is necessary. Thus, unique data are required which quantify the unsteady three-dimensional flow through multi-stage turbine blade rows, including the effect of the film coolant flow. This requires experiments in appropriate research facilities in which complete flow field data, not only point measurements, are obtained and analyzed. Also, as design CFD codes do not account for unsteady flow effects, the next logical challenge and the current thrust in CFD code development is multiple-stage analyses that account for the interactions between neighboring blade rows.

  1. Thermal lift generation and drag reduction in rarefied aerodynamics

    Science.gov (United States)

    Pekardan, Cem; Alexeenko, Alina

    2016-11-01

    With the advent of the new technologies in low pressure environments such as Hyperloop and helicopters designed for Martian applications, understanding the aerodynamic behavior of airfoils in rarefied environments are becoming more crucial. In this paper, verification of rarefied ES-BGK solver and ideas such as prediction of the thermally induced lift and drag reduction in rarefied aerodynamics are investigated. Validation of the rarefied ES-BGK solver with Runge-Kutta discontinous Galerkin method with experiments in transonic regime with a Reynolds number of 73 showed that ES-BGK solver is the most suitable solver in near slip transonic regime. For the quantification of lift generation, A NACA 0012 airfoil is studied with a high temperature surface on the bottom for the lift creation for different Knudsen numbers. It was seen that for lower velocities, continuum solver under predicts the lift generation when the Knudsen number is 0.00129 due to local velocity gradients reaching slip regime although lift coefficient is higher with the Boltzmann ES-BGK solutions. In the second part, the feasibility of using thermal transpiration for drag reduction is studied. Initial study in drag reduction includes an application of a thermal gradient at the upper surface of a NACA 0012 airfoil near trailing edge at a 12-degree angle of attack and 5 Pa pressure. It was seen that drag is reduced by 4 percent and vortex shedding frequency is reduced due to asymmetry introduced in the flow due to temperature gradient causing reverse flow due to thermal transpiration phenomena.

  2. Global Design Optimization for Aerodynamics and Rocket Propulsion Components

    Science.gov (United States)

    Shyy, Wei; Papila, Nilay; Vaidyanathan, Rajkumar; Tucker, Kevin; Turner, James E. (Technical Monitor)

    2000-01-01

    Modern computational and experimental tools for aerodynamics and propulsion applications have matured to a stage where they can provide substantial insight into engineering processes involving fluid flows, and can be fruitfully utilized to help improve the design of practical devices. In particular, rapid and continuous development in aerospace engineering demands that new design concepts be regularly proposed to meet goals for increased performance, robustness and safety while concurrently decreasing cost. To date, the majority of the effort in design optimization of fluid dynamics has relied on gradient-based search algorithms. Global optimization methods can utilize the information collected from various sources and by different tools. These methods offer multi-criterion optimization, handle the existence of multiple design points and trade-offs via insight into the entire design space, can easily perform tasks in parallel, and are often effective in filtering the noise intrinsic to numerical and experimental data. However, a successful application of the global optimization method needs to address issues related to data requirements with an increase in the number of design variables, and methods for predicting the model performance. In this article, we review recent progress made in establishing suitable global optimization techniques employing neural network and polynomial-based response surface methodologies. Issues addressed include techniques for construction of the response surface, design of experiment techniques for supplying information in an economical manner, optimization procedures and multi-level techniques, and assessment of relative performance between polynomials and neural networks. Examples drawn from wing aerodynamics, turbulent diffuser flows, gas-gas injectors, and supersonic turbines are employed to help demonstrate the issues involved in an engineering design context. Both the usefulness of the existing knowledge to aid current design

  3. A study of the use of experimental stability derivatives in the calculation of the lateral disturbed motions of a swept-wing airplane and comparison with flight results

    Science.gov (United States)

    Bird, John D; Jaquet, Byron M

    1951-01-01

    An investigation was made to determine the accuracy with which the lateral flight motions of a swept-wing airplane could be predicted from experimental stability derivatives, determined in the 6-foot-diameter rolling-flow test section and 6 by 6-foot curved-flow test section of the Langley stability tunnel. In addition, determination of the significance of including the nonlinear aerodynamic effects of sideslip in the calculations of the motions was desired. All experimental aerodynamic data necessary for prediction of the lateral flight motions are presented along with a number of comparisons between flight and calculated motions caused by rudder and aileron disturbances.

  4. Analysis of detailed aerodynamic field measurements using results from an aeroelastic code

    Energy Technology Data Exchange (ETDEWEB)

    Schepers, J.G. [Energy Research Centre, Petten (Netherlands); Feigl, L. [Ecotecnia S. coop.c.l. (Spain); Rooij, R. van; Bruining, A. [Delft Univ. of Technology (Netherlands)

    2004-07-01

    In this article an analysis is given of aerodynamic field measurements on wind turbine blades. The analysis starts with a consistency check on the measurements, by relating the measured local aerodynamic segment forces to the overall rotor loads. It is found that the results are very consistent. Moreover, a comparison is made between measured results and results calculated from an aeroelastic code. On the basis of this comparison, the aerodynamic modelling in the aeroelastic code could be improved. This holds in particular for the modelling of 3D stall effects, not only on the lift but also on the drag, and for the modelling of tip effects (author)

  5. Aerodynamic optimization of 3D wing based on iSIGHT

    Institute of Scientific and Technical Information of China (English)

    YIN Bo; XU Dian; AN Yi-ran; CHEN Yao-song

    2008-01-01

    A method for combining the CFD software, Fluent, with the iSIGHT design platform is presented to optimize a three-dimensional wing to ameliorate its aerodynamics performance. In the optimization design, two kinds of genetic algorithms, the Neighborhood Cultivation Genetic Algorithm (NCGA) and the Non-dominated Sorting Genetic Algorithm (NSGAII), are employed and the Navier-Stoke (N-S) equations are adopted to derive the aerodynamics functions of the 3D wing. The aerodynamic performance of the optimized wing has been significantly improved, which shows that the approach can be extended and employed in other cases.

  6. Aerodynamic coefficients of plain and helically filleted twin circular cylinders for varying wind angles of attack

    DEFF Research Database (Denmark)

    Acampora, Antonio; Georgakis, Christos T.

    2013-01-01

    Moderate vibrations continue to be recorded on the Øresund Bridge twin-stay cables. System identification techniques have been applied to investigate the aerodynamic characteristics of the cables based on ambient vibration measurements. As might be expected, the measured aerodynamic damping ratios...... vary from those estimated through use of aerodynamic coefficients of single circular cylinders, as reported in literature. To address this issue, wind tunnel tests were performed on a 1:2.3 scale section model of the Øresund Bridge cables, with and without the presence of helical fillets. In this paper...

  7. Finding optimum airfoil shape to get maximum aerodynamic efficiency for a wind turbine

    Science.gov (United States)

    Sogukpinar, Haci; Bozkurt, Ismail

    2017-02-01

    In this study, aerodynamic performances of S-series wind turbine airfoil of S 825 are investigated to find optimum angle of attack. Aerodynamic performances calculations are carried out by utilization of a Computational Fluid Dynamics (CFD) method withstand finite capacity approximation by using Reynolds-Averaged-Navier Stokes (RANS) theorem. The lift and pressure coefficients, lift to drag ratio of airfoil S 825 are analyzed with SST turbulence model then obtained results crosscheck with wind tunnel data to verify the precision of computational Fluid Dynamics (CFD) approximation. The comparison indicates that SST turbulence model used in this study can predict aerodynamics properties of wind blade.

  8. Physical and Numerical Simulation of Aerodynamics of Cyclone Heating Device with Distributed Gas Input

    Directory of Open Access Journals (Sweden)

    E. N. Saburov

    2010-01-01

    Full Text Available The paper presents results of physical and numerical simulation of aerodynamics of a cyclone heating device. Calculation models of axial and radial flow motions at various outlet diameters and also cyclone flow motion trajectory have been developed in the paper. The paper considers and compares experimental and calculated distributions of tangential and axial component of full flow rate. The comparison of numerical and physical experimental results has revealed good prospects concerning usage of CFX ®10.0 programming complex for simulation of aerodynamics of cyclone heating devices and further improvement of methodologies and their aerodynamic calculation. 

  9. Full-scale measurements of aerodynamic induction in a rotor plane

    Science.gov (United States)

    Larsen, Gunner Chr; Hansen, Kurt S.

    2014-12-01

    Reliable modelling of aerodynamic induction is imperative for successful prediction of wind turbine loads and wind turbine dynamics when based on state-of- the-art aeroelastic tools. Full-scale LiDAR based wind speed measurements, with high temporal and spatial resolution, have been conducted in the rotor plane of an operating 2MW/80m wind turbine to perform detailed analysis the aerodynamic induction. The experimental setup, analyses of the spatial structure of the aerodynamic induction and subsequent comparisons with numerical predictions, using the HAWC2 aerolastic code, are presented.

  10. Full-scale measurements of aerodynamic induction in a rotor plane

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.; Hansen, Kurt Schaldemose

    2014-01-01

    in the rotor plane of an operating 2MW/80m wind turbine to perform detailed analysis the aerodynamic induction. The experimental setup, analyses of the spatial structure of the aerodynamic induction and subsequent comparisons with numerical predictions, using the HAWC2 aerolastic code, are presented.......Reliable modelling of aerodynamic induction is imperative for successful prediction of wind turbine loads and wind turbine dynamics when based on state-of- the-art aeroelastic tools. Full-scale LiDAR based wind speed measurements, with high temporal and spatial resolution, have been conducted...

  11. Experimental and analytical research on the aerodynamics of wind driven turbines. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Rohrbach, C.; Wainauski, H.; Worobel, R.

    1977-12-01

    This aerodynamic research program was aimed at providing a reliable, comprehensive data base on a series of wind turbine models covering a broad range of the prime aerodynamic and geometric variables. Such data obtained under controlled laboratory conditions on turbines designed by the same method, of the same size, and tested in the same wind tunnel had not been available in the literature. Moreover, this research program was further aimed at providing a basis for evaluating the adequacy of existing wind turbine aerodynamic design and performance methodology, for assessing the potential of recent advanced theories and for providing a basis for further method development and refinement.

  12. Aerodynamic map for soft and hard hypersonic level flight in near space

    Institute of Scientific and Technical Information of China (English)

    Ruifeng Hu; Ziniu Wu; Zhe Wu; Xiaoxin Wang; Zhongwei Tian

    2009-01-01

    In this note, we design a velocity-altitude map for hypersonic level flight in near space of altitude 20-100 km. This map displays aerodynamic-related parameters associated with near space level flight, schematically or quantitatively. Various physical conditions for the near-space level flight are then characterized, including laminar or turbulent flow, rarefaction or continuous flow, aerodynamic heating, as well as conditions for sustaining level flight with and without orbital effect. This map allows one to identify conditions to have soft flight or hard flight, and this identification would be helpful for making correct planning on detailed studies of aerodynamics or making initial design of near space vehicles.

  13. Simultaneous Excitation of Multiple-Input Multiple-Output CFD-Based Unsteady Aerodynamic Systems

    Science.gov (United States)

    Silva, Walter A.

    2008-01-01

    A significant improvement to the development of CFD-based unsteady aerodynamic reduced-order models (ROMs) is presented. This improvement involves the simultaneous excitation of the structural modes of the CFD-based unsteady aerodynamic system that enables the computation of the unsteady aerodynamic state-space model using a single CFD execution, independent of the number of structural modes. Four different types of inputs are presented that can be used for the simultaneous excitation of the structural modes. Results are presented for a flexible, supersonic semi-span configuration using the CFL3Dv6.4 code.

  14. Benchmarking aerodynamic prediction of unsteady rotor aerodynamics of active flaps on wind turbine blades using ranging fidelity tools

    Science.gov (United States)

    Barlas, Thanasis; Jost, Eva; Pirrung, Georg; Tsiantas, Theofanis; Riziotis, Vasilis; Navalkar, Sachin T.; Lutz, Thorsten; van Wingerden, Jan-Willem

    2016-09-01

    Simulations of a stiff rotor configuration of the DTU 10MW Reference Wind Turbine are performed in order to assess the impact of prescribed flap motion on the aerodynamic loads on a blade sectional and rotor integral level. Results of the engineering models used by DTU (HAWC2), TUDelft (Bladed) and NTUA (hGAST) are compared to the CFD predictions of USTUTT-IAG (FLOWer). Results show fairly good comparison in terms of axial loading, while alignment of tangential and drag-related forces across the numerical codes needs to be improved, together with unsteady corrections associated with rotor wake dynamics. The use of a new wake model in HAWC2 shows considerable accuracy improvements.

  15. Longitudinal dynamic stability of a shuttle vehicle.

    Science.gov (United States)

    Vinh, N. X.; Laitone, E. V.

    1972-01-01

    Analytical study of the longitudinal dynamic stability of a nonrolling, lifting vehicle gliding at hypersonic speeds. The analysis applies to shuttle vehicles designed for operating up to the rim of a planetary atmosphere. A general nondimensional time transformation is introduced to derive a unified second-order linear differential equation for the angle of attack, valid for all types of reentry of a general type of vehicle. The stability of motion is discussed for two fundamental regimes of flight that are based on widely different assumptions. For near ballistic entry along a straight line trajectory, the equation reduces to a confluent hypergeometric equation, the solution of which can be expressed in terms of Whittaker's function. Using a theorem in the theory of stability of differential equations, criteria for damped oscillations are derived. It is shown that the aerodynamic criteria for stability are the same as for the case of ballistic entry. In addition, for each vehicle configuration, and specified planetary atmosphere, there exists an altitude range where the angle of attack frequency is nearly equal to the orbital frequency causing instability in pitch. This resonance instability is due to the ellipticity of the orbit. Criteria for eccentricity instability are derived.

  16. High angle of attack: Forebody flow physics and design emphasizing directional stability

    Science.gov (United States)

    Ravi, R.

    A framework for understanding the fundamental physics of flowfields over forebody type shapes at low speed, high angle of attack conditions with special emphasis on sideslip has been established. Computational Fluid Dynamics (CFD) has been used to study flowfieids over experimentally investigated forebodies: the Lamont tangent-ogive forebody, the F-5A forebody and the Erickson chine forebody. A modified version of a current advanced code, CFL3D, was used to solve the Euler and thin-layer Navier-Stokes equations. The Navier-Stokes equations used a form of the Baldwin-Lomax turbulence model modified to account for massive crossflow separation. Using the insight provided by the solutions obtained using CFD, together with comparison with limited available data, the aerodynamics of forebodies with positive directional stability has been revealed. An unconventional way of presenting the results is used to illustrate how a positive contribution to directional stability arises. Based on this new understanding, a parametric study was then conducted to determine which shapes promote a positive contribution to directional stability. The effect of cross-sectional shape on directional stability was found to be very significant. Broad chine-shaped cross-sections were found to promote directional stability. Also, directional stability is improved if the chine is placed closer to the top of the cross-section. Planform shapes also played an important role in determining the forebody directional stability characteristics. This initial parametric study has been used to propose some guidelines for aerodynamic design to promote positive directional stability.

  17. Dynamics and Adaptive Control for Stability Recovery of Damaged Aircraft

    Science.gov (United States)

    Nguyen, Nhan; Krishnakumar, Kalmanje; Kaneshige, John; Nespeca, Pascal

    2006-01-01

    This paper presents a recent study of a damaged generic transport model as part of a NASA research project to investigate adaptive control methods for stability recovery of damaged aircraft operating in off-nominal flight conditions under damage and or failures. Aerodynamic modeling of damage effects is performed using an aerodynamic code to assess changes in the stability and control derivatives of a generic transport aircraft. Certain types of damage such as damage to one of the wings or horizontal stabilizers can cause the aircraft to become asymmetric, thus resulting in a coupling between the longitudinal and lateral motions. Flight dynamics for a general asymmetric aircraft is derived to account for changes in the center of gravity that can compromise the stability of the damaged aircraft. An iterative trim analysis for the translational motion is developed to refine the trim procedure by accounting for the effects of the control surface deflection. A hybrid direct-indirect neural network, adaptive flight control is proposed as an adaptive law for stabilizing the rotational motion of the damaged aircraft. The indirect adaptation is designed to estimate the plant dynamics of the damaged aircraft in conjunction with the direct adaptation that computes the control augmentation. Two approaches are presented 1) an adaptive law derived from the Lyapunov stability theory to ensure that the signals are bounded, and 2) a recursive least-square method for parameter identification. A hardware-in-the-loop simulation is conducted and demonstrates the effectiveness of the direct neural network adaptive flight control in the stability recovery of the damaged aircraft. A preliminary simulation of the hybrid adaptive flight control has been performed and initial data have shown the effectiveness of the proposed hybrid approach. Future work will include further investigations and high-fidelity simulations of the proposed hybrid adaptive Bight control approach.

  18. Effects of relaxed static longitudinal stability on a single-stage-to-orbit vehicle design

    Science.gov (United States)

    Freeman, D. C., Jr.; Wilhite, A. W.

    1979-01-01

    The effects of relaxing longitudinal stability requirements on single stage to orbit space vehicles is studied. A comparison of the mass and performance characteristics of two vehicles, one designed for positive levels of longitudinal stability and the other designed with relaxed stability requirements in a computer aided design process is presented. Both vehicles, required to meet the same mission characteristics are described. Wind tunnel tests, conducted over a Mach number range from 0.3 to 4.63 to verify estimated aerodynamic characteristics, are discussed.

  19. Design and Execution of the Hypersonic Inflatable Aerodynamic Decelerator Large-Article Wind Tunnel Experiment

    Science.gov (United States)

    Cassell, Alan M.

    2013-01-01

    The testing of 3- and 6-meter diameter Hypersonic Inflatable Aerodynamic Decelerator (HIAD) test articles was completed in the National Full-Scale Aerodynamics Complex 40 ft x 80 ft Wind Tunnel test section. Both models were stacked tori, constructed as 60 degree half-angle sphere cones. The 3-meter HIAD was tested in two configurations. The first 3-meter configuration utilized an instrumented flexible aerodynamic skin covering the inflatable aeroshell surface, while the second configuration employed a flight-like flexible thermal protection system. The 6-meter HIAD was tested in two structural configurations (with and without an aft-mounted stiffening torus near the shoulder), both utilizing an instrumented aerodynamic skin.

  20. Aerodynamic Study about an Automotive Vehicle with Capacity for Only One Occupan

    Directory of Open Access Journals (Sweden)

    Almeida R.A

    2016-04-01

    Full Text Available The presented study describes the aerodynamic behavior of a compact, single occupant, automotive vehicle. To optimize the aerodynamic characteristics of this vehicle, a flow dynamics study was conducted using a virtual model. The outer surfaces of the vehicle body were designed using Computer Aided Design (CAD tools and its aerodynamic performance simulated virtually using Computational Fluid Dynamics (CFD software. Parameters such as pressure coefficient (Cp, coefficient of friction (Cf and graphical analysis of the streamlines were used to understand the flow dynamics and propose recommendations aimed at improving the coefficient of drag (Cd. The identification of interaction points between the fluid and the flow structure was the primary focus of study to develop these propositions. The study of phenomena linked to the characteristics of the model presented here, allowed the identification of design features that should be avoided to generate improved aerodynamic performance