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Sample records for net drag reduction

  1. Drag reduction in nature

    Science.gov (United States)

    Bushnell, D. M.; Moore, K. J.

    1991-01-01

    Recent studies on the drag-reducing shapes, structures, and behaviors of swimming and flying animals are reviewed, with an emphasis on potential analogs in vehicle design. Consideration is given to form drag reduction (turbulent flow, vortex generation, mass transfer, and adaptations for body-intersection regions), skin-friction drag reduction (polymers, surfactants, and bubbles as surface 'additives'), reduction of the drag due to lift, drag-reduction studies on porpoises, and drag-reducing animal behavior (e.g., leaping out of the water by porpoises). The need for further research is stressed.

  2. Drag reduction strategies

    Science.gov (United States)

    Hill, D. Christopher

    1994-12-01

    previously a description was given of an active control scheme using wall transpiration that leads to a 15% reduction in surface skin friction beneath a turbulent boundary layer, according to direct numerical simulation. In this research brief further details of that scheme and its variants are given together with some suggestions as to how sensor/actuator arrays could be configured to reduce surface drag. The research which is summarized here was performed during the first half of 1994. This research is motivated by the need to understand better how the dynamics of near-wall turbulent flow can be modified so that skin friction is reduced. The reduction of turbulent skin friction is highly desirable in many engineering applications. Experiments and direct numerical simulations have led to an increased understanding of the cycle of turbulence production and transport in the boundary layer and raised awareness of the possibility of disrupting the process with a subsequent reduction in turbulent skin friction. The implementation of active feedback control in a computational setting is a viable approach for the investigation of the modifications to the flow physics that can be achieved. Bewley et al. and Hill describe how ideas from optimal control theory are employed to give 'sub-optimal' drag reduction schemes. The objectives of the work reported here is to investigate in greater detail the assumptions implicit within such schemes and their limitations. It is also our objective to describe how an array of sensors and actuators could be arranged and interconnected to form a 'smart' surface which has low skin friction.

  3. DRAG REDUCTION WITH SUPERHYDROPHOBIC RIBLETS

    Energy Technology Data Exchange (ETDEWEB)

    Barbier, Charlotte N [ORNL; D' Urso, Brian R [ORNL; Jenner, Elliot [University of Pittsburgh

    2012-01-01

    Samples combining riblets and superhydrophobic surfaces are fabricated at University of Pittsburgh and their drag reduction properties are studied at the Center for Nanophase Materials Sciences (CNMS) in Oak Ridge National Laboratory with a commercial cone-and-plate rheometer. In parallel to the experiments, numerical simulations are performed in order to estimate the slip length at high rotational speed. For each sample, a drag reduction of at least 5% is observed in both laminar and turbulent regime. At low rotational speed, drag reduction up to 30% is observed with a 1 mm deep grooved sample. As the rotational speed increases, a secondary flow develops causing a slight decrease in drag reductions. However, drag reduction above 15% is still observed for the large grooved samples. In the turbulent regime, the 100 microns grooved sample becomes more efficient than the other samples in drag reduction and manages to sustain a drag reduction above 15%. Using the simulations, the slip length of the 100 micron grooved sample is estimated to be slightly above 100 micron in the turbulent regime.

  4. Viscous drag reduction in boundary layers

    Science.gov (United States)

    Bushnell, Dennis M. (Editor); Hefner, Jerry N. (Editor)

    1990-01-01

    The present volume discusses the development status of stability theory for laminar flow control design, applied aspects of laminar-flow technology, transition delays using compliant walls, the application of CFD to skin friction drag-reduction, active-wave control of boundary-layer transitions, and such passive turbulent-drag reduction methods as outer-layer manipulators and complex-curvature concepts. Also treated are such active turbulent drag-reduction technique applications as those pertinent to MHD flow drag reduction, as well as drag reduction in liquid boundary layers by gas injection, drag reduction by means of polymers and surfactants, drag reduction by particle addition, viscous drag reduction via surface mass injection, and interactive wall-turbulence control.

  5. Drag Reduction of Bacterial Cellulose Suspensions

    Directory of Open Access Journals (Sweden)

    Satoshi Ogata

    2011-01-01

    Full Text Available Drag reduction due to bacterial cellulose suspensions with small environmental loading was investigated. Experiments were carried out by measuring the pressure drop in pipe flow. It was found that bacterial cellulose suspensions give rise to drag reduction in the turbulent flow range. We observed a maximum drag reduction ratio of 11% and found that it increased with the concentration of the bacterial cellulose suspension. However, the drag reduction effect decreased in the presence of mechanical shear.

  6. Drag Reduction by Microvortexes in Transverse Microgrooves

    Directory of Open Access Journals (Sweden)

    Bao Wang

    2014-07-01

    Full Text Available A transverse microgrooved surface was employed here to reduce the surface drag force by creating a slippage in bottom layer in turbulent boundary layer. A detailed simulation and experimental investigation on drag reduction by transverse microgrooves were given. The computational fluid dynamics simulation, using RNG k-ε turbulent model, showed that the vortexes were formed in the grooves and they were a main reason for the drag reduction. On the upside of the vortex, the revolving direction was consistent with the main flow, which decreased the flow shear stress by declining the velocity gradient. The experiments were carried out in a high-speed water tunnel with flow velocity varying from 17 to 19 m/s. The experimental results showed that the drag reduction was about 13%. Therefore, the computational and experimental results were cross-checked and consistent with each other to prove that the presented approach achieved effective drag reduction underwater.

  7. Bubble drag reduction requires large bubbles

    CERN Document Server

    Verschoof, Ruben A; Sun, Chao; Lohse, Detlef

    2016-01-01

    In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag reduction in turbulent flow dramatically depends on the bubble size. By adding minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise completely unchanged strongly turbulent Taylor-Couette flow containing bubbles, we dramatically reduce the drag reduction from more than 40% to about 4%, corresponding to the trivial effect of the bubbles on the density and viscosity of the liquid. The reason for this striking behavior is that the addition of surfactants prevents bubble coalescence, leading to much smaller bubbles. Our result demonstrates that bubble deformability is crucial for bubble drag reduction in turbulent flow and opens the door for an optimization of the process.

  8. Drag Reduction by Leidenfrost Vapor Layers

    KAUST Repository

    Vakarelski, Ivan Uriev

    2011-05-23

    We demonstrate and quantify a highly effective drag reduction technique that exploits the Leidenfrost effect to create a continuous and robust lubricating vapor layer on the surface of a heated solid sphere moving in a liquid. Using high-speed video, we show that such vapor layers can reduce the hydrodynamic drag by over 85%. These results appear to approach the ultimate limit of drag reduction possible by different methods based on gas-layer lubrication and can stimulate the development of related energy saving technologies.

  9. On the energy economics of air lubrication drag reduction

    Directory of Open Access Journals (Sweden)

    Simo A. Mäkiharju

    2012-12-01

    Full Text Available Air lubrication techniques for frictional drag reduction on ships have been proposed by numerous researchers since the 19th century. However, these techniques have not been widely adopted as questions persist about their drag reduction performance beyond the laboratory, as well as energy and economic cost-benefit. This paper draws on data from the literature to consider the suitability of air lubrication for large ocean going and U.S. Great Lakes ships, by establishing the basic energy economic calculations and presenting results for a hypothetical air lubricated ship. All the assumptions made in the course of the analysis are clearly stated so that they can be refined when considering application of air lubrication to a specific ship. The analysis suggests that, if successfully implemented, both air layer and partial cavity drag reduction could lead to net energy savings of 10 to 20%, with corresponding reductions in emissions.

  10. Turbulent drag reduction through oscillating discs

    CERN Document Server

    Wise, Daniel J

    2014-01-01

    The changes of a turbulent channel flow subjected to oscillations of wall flush-mounted rigid discs are studied by means of direct numerical simulations. The Reynolds number is $R_\\tau$=$180$, based on the friction velocity of the stationary-wall case and the half channel height. The primary effect of the wall forcing is the sustained reduction of wall-shear stress, which reaches a maximum of 20%. A parametric study on the disc diameter, maximum tip velocity, and oscillation period is presented, with the aim to identify the optimal parameters which guarantee maximum drag reduction and maximum net energy saving, computed by taking into account the power spent to actuate the discs. This may be positive and reaches 6%. The Rosenblat viscous pump flow is used to predict the power spent for disc motion in the turbulent channel flow and to estimate localized and transient regions over the disc surface subjected to the turbulent regenerative braking effect, for which the wall turbulence exerts work on the discs. The...

  11. Drag reduction in riblet-lined pipes

    Energy Technology Data Exchange (ETDEWEB)

    Enyutin, G.V.; Lashkov, Yu.A.; Samoilova, N.V.

    1995-07-01

    The possibilities of reducing the drag in pipes with a circular cross section by lining them with riblets have been investigated experimentally for developed turbulent air flow. The maximum drag reduction of 6-7% in the riblet-lined as compared with the smooth pipe was obtained for a dimensionless riblet pitch, expressed in law-of-the-wall parameters, s{sup +} = 14-18.

  12. Frictional drag reduction by bubble injection

    Science.gov (United States)

    Murai, Yuichi

    2014-07-01

    The injection of gas bubbles into a turbulent boundary layer of a liquid phase has multiple different impacts on the original flow structure. Frictional drag reduction is a phenomenon resulting from their combined effects. This explains why a number of different void-drag reduction relationships have been reported to date, while early works pursued a simple universal mechanism. In the last 15 years, a series of precisely designed experimentations has led to the conclusion that the frictional drag reduction by bubble injection has multiple manifestations dependent on bubble size and flow speed. The phenomena are classified into several regimes of two-phase interaction mechanisms. Each regime has inherent physics of bubbly liquid, highlighted by keywords such as bubbly mixture rheology, the spectral response of bubbles in turbulence, buoyancy-dominated bubble behavior, and gas cavity breakup. Among the regimes, bubbles in some selected situations lose the drag reduction effect owing to extra momentum transfer promoted by their active motions. This separates engineers into two communities: those studying small bubbles for high-speed flow applications and those studying large bubbles for low-speed flow applications. This article reviews the roles of bubbles in drag reduction, which have been revealed from fundamental studies of simplified flow geometries and from development of measurement techniques that resolve the inner layer structure of bubble-mixed turbulent boundary layers.

  13. Active aerodynamic drag reduction on morphable cylinders

    Science.gov (United States)

    Guttag, M.; Reis, P. M.

    2017-12-01

    We study a mechanism for active aerodynamic drag reduction on morphable grooved cylinders, whose topography can be modified pneumatically. Our design is inspired by the morphology of the Saguaro cactus (Carnegiea gigantea), which possesses an array of axial grooves, thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. Our analog experimental samples comprise a spoked rigid skeleton with axial cavities, covered by a stretched elastomeric film. Decreasing the inner pressure of the sample produces axial grooves, whose depth can be accurately varied, on demand. First, we characterize the relation between groove depth and pneumatic loading through a combination of precision mechanical experiments and finite element simulations. Second, wind tunnel tests are used to measure the aerodynamic drag coefficient (as a function of Reynolds number) of the grooved samples, with different levels of periodicity and groove depths. We focus specifically on the drag crisis and systematically measure the associated minimum drag coefficient and the critical Reynolds number at which it occurs. The results are in agreement with the classic literature of rough cylinders, albeit with an unprecedented level of precision and resolution in varying topography using a single sample. Finally, we leverage the morphable nature of our system to dynamically reduce drag for varying aerodynamic loading conditions. We demonstrate that actively controlling the groove depth yields a drag coefficient that decreases monotonically with Reynolds number and is significantly lower than the fixed sample counterparts. These findings open the possibility for the drag reduction of grooved cylinders to be operated over a wide range of flow conditions.

  14. Drag Reduction by Laminar Flow Control

    Directory of Open Access Journals (Sweden)

    Nils Beck

    2018-01-01

    Full Text Available The Energy System Transition in Aviation research project of the Aeronautics Research Center Niedersachsen (NFL searches for potentially game-changing technologies to reduce the carbon footprint of aviation by promoting and enabling new propulsion and drag reduction technologies. The greatest potential for aerodynamic drag reduction is seen in laminar flow control by boundary layer suction. While most of the research so far has been on partial laminarization by application of Natural Laminar Flow (NLF and Hybrid Laminar Flow Control (HLFC to wings, complete laminarization of wings, tails and fuselages promises much higher gains. The potential drag reduction and suction requirements, including the necessary compressor power, are calculated on component level using a flow solver with viscid/inviscid coupling and a 3D Reynolds-Averaged Navier-Stokes (RANS solver. The effect on total aircraft drag is estimated for a state-of-the-art mid-range aircraft configuration using preliminary aircraft design methods, showing that total cruise drag can be halved compared to today’s turbulent aircraft.

  15. Innovative Flow Control Concepts for Drag Reduction

    Science.gov (United States)

    Lin, John C.; Whalen, Edward A.; Eppink, Jenna L.; Siochi, Emilie J.; Alexander, Michael G.; Andino, Marlyn Y.

    2016-01-01

    This paper highlights the technology development of two flow control concepts for aircraft drag reduction. The NASA Environmentally Responsible Aviation (ERA) project worked with Boeing to demonstrate these two concepts on a specially outfitted Boeing 757 ecoDemonstrator during the spring of 2015. The first flow control concept used Active Flow Control (AFC) to delay flow separation on a highly deflected rudder and increase the side force that it generates. This may enable a smaller vertical tail to provide the control authority needed in the event of an engine failure during takeoff and landing, while still operating in a conventional manner over the rest of the flight envelope. Thirty-one sweeping jet AFC actuators were installed and successfully flight-tested on the vertical tail of the 757 ecoDemonstrator. Pilot feedback, flow cone visualization, and analysis of the flight test data confirmed that the AFC is effective, as a smoother flight and enhanced rudder control authority were reported. The second flow control concept is the Insect Accretion Mitigation (IAM) innovation where surfaces were engineered to mitigate insect residue adhesion on a wing's leading edge. This is necessary because something as small as an insect residue on the leading edge of a laminar flow wing design can cause turbulent wedges that interrupt laminar flow, resulting in an increase in drag and fuel use. Several non-stick coatings were developed by NASA and applied to panels that were mounted on the leading edge of the wing of the 757 ecoDemonstrator. The performance of the coated surfaces was measured and validated by the reduction in the number of bug adhesions relative to uncoated control panels flown simultaneously. Both flow control concepts (i.e., sweeping jet actuators and non-stick coatings) for drag reduction were the culmination of several years of development, from wind tunnel tests to flight tests, and produced valuable data for the advancement of modern aircraft designs

  16. Effects of Polymer Parameters on Drag Reduction.

    Science.gov (United States)

    Safieddine, Abbas Mohammad

    The effects of polymer parameters on fluid drag reduction using polyethylene oxide (PEO), polyacrylamide (PAM), guar gum (GG) and hydroxyethyl cellulose (HEC) were investigated. Due to the unavailability of high molecular weight (MW) water-soluble polymers having narrow molecular weight distribution (MWD), an aqueous preparative size exclusion chromatography (SEC) system capable of fractionating over wide MW ranges was constructed. An online low shear viscometer, coupled to the SEC, measured the instantaneous intrinsic viscosity of the eluting polymer solution and, therefore, served as a MW detector since Mark-Houwink "K" and "a" values for all four polymers were known. With the aid of the viscometer, the SEC system was calibrated. The preparative nature of the chromatography system allowed the collection of large volumes of nearly monodisperse fractions (MWD daltons. Also, the preparative SEC approach allowed drag reduction (DR) experiments using well-characterized, narrowly dispersed polymer solutions under controlled tube flow conditions. Correlations of drag reduction performance with primary polymer parameters (i.e., concentration, intrinsic viscosity ((eta)), volume fraction (c(eta)), number of chain links (N), and combinations thereof) were used to test the validity of several theoretical DR models. Walsh's energy model, as well as the Deborah argument, did not completely account for drag reduction behavior under all experimental conditions. Within each of the flexible or rigid polymer groups, the extensional viscosity model was successful in correlating c(eta) N with DR under all turbulent conditions. However, it failed to account for the differences in chemical structure between the two polymer groups. However, when the cellulosic repeat unit was used instead of the carbon-carbon bond as the chain link for the rigid polymers (GG and HEC), all DR versus c (eta) N curves under all turbulent conditions collapsed into a single function. This has been predicted

  17. Progress in Frictional Drag Reduction Summer 1971 to Summer 1972

    Science.gov (United States)

    1973-01-01

    additives, indicates equally significant drag reduction. One high polymer that shows extreme promise as a drag reducing additive in blood flow is okra ...1972. 9 Lindeman, L. F., "Polymer Injection for Drag Reduction," M.S. thesis , Department of Civil Engineering, Colorado State University, Fort Collins...K.-S., "Measurement of Complex Viscosity in Solutions at Finite Shear Strains," Ph.D. Thesis , University of Missouri - Rolla, 1971. 16 6. Drag

  18. Drag reduction properties of superhydrophobic mesh pipes

    Science.gov (United States)

    Geraldi, Nicasio R.; Dodd, Linzi E.; Xu, Ben B.; Wells, Gary G.; Wood, David; Newton, Michael I.; McHale, Glen

    2017-09-01

    Even with the recent extensive study into superhydrophobic surfaces, the fabrication of such surfaces on the inside walls of a pipe remains challenging. In this work we report a convenient bi-layered pipe design using a thin superhydrophobic metallic mesh formed into a tube, supported inside another pipe. A flow system was constructed to test the fabricated bi-layer pipeline, which allowed for different constant flow rates of water to be passed through the pipe, whilst the differential pressure was measured, from which the drag coefficient (ƒ) and Reynolds numbers (Re) were calculated. Expected values of ƒ were found for smooth glass pipes for the Reynolds number (Re) range 750-10 000, in both the laminar and part of the turbulent regimes. Flow through plain meshes without the superhydrophobic coating were also measured over a similar range (750  pipe of the same diameter. This demonstrates that a superhydrophobic mesh can support a plastron and provide a drag reduction compared to a plain mesh, however, the plastron is progressively destroyed with use and in particular at higher flow rates.

  19. Drag Reduction Using Polysaccharides in a Taylor–Couette Flow

    Directory of Open Access Journals (Sweden)

    Pallavi Bhambri

    2017-12-01

    Full Text Available Three different polysaccharides, aloe vera, Tamarind powder and pineapple fibers, are utilized as drag reducing agents in a turbulent flow. Using a Taylor–Couette setup, consisting of a rotating inner cylinder, for measuring the drag reduction, a range of Reynolds numbers from 4 × 104 to 3 × 105 has been explored in this study. The results are in good agreement with previous studies on polysaccharides conducted in a pipe/channel flow and a maximum drag reduction of 35% has been observed. Further, novel additives such as cellulose nanocrystals (CNC, surfactants and CNC grafted with surfactants are also examined in this study for drag reduction. CNC due to its rigid rod structure reduced the drag by 30%. Surfactant, due to its unique micelle formation showed maximum drag reduction of 80% at low Re. Further, surfactant was grafted on CNC and was examined for drag reduction. However, drag reduction property of surfactant was observed to be significantly reduced after grafting on CNC. The effect of Reynolds number on drag reduction is studied for all the additives investigated in this study.

  20. Bionic Research on Bird Feather for Drag Reduction

    Directory of Open Access Journals (Sweden)

    Beibei Feng

    2015-02-01

    Full Text Available To reduce friction drag with bionic method in a more feasible way, the surface microstructure of bird feather was analyzed attempting to reveal the biologic features responding to skin friction drag reduction. Then comparative bionic surface mimicking bird feather was fabricated through hot-rolling technology for drag reduction. The microriblet film was formed on a PVC substrate through a self-developed hot-rolling equipment. The bionic surface with micron-scale riblets formed spontaneously due to the elastic-plastic deformation of PVC in high temperature and high pressure environment. Comparative experiments between micro-structured bionic surface and smooth surface were performed in a wind tunnel to evaluate the effect of bionic surface on drag reduction, and significant drag reduction efficiency was obtained. Numerical simulation results show that microvortex induced in the solid-gas interface of bionic surface has the effect of shear stress reduction and the small level of an additional pressure drag resulting from pressure distribution deviation on bird feather like surface, hence reducing the skin friction drag significantly. Therefore, with remarkable drag reduction performance and simple fabrication technology, the proposed drag reduction technique shows the promise for practical applications.

  1. Bionic Research on Bird Feather for Drag Reduction

    OpenAIRE

    Beibei Feng; Darong Chen; Jiadao Wang; Xingtuan Yang

    2015-01-01

    To reduce friction drag with bionic method in a more feasible way, the surface microstructure of bird feather was analyzed attempting to reveal the biologic features responding to skin friction drag reduction. Then comparative bionic surface mimicking bird feather was fabricated through hot-rolling technology for drag reduction. The microriblet film was formed on a PVC substrate through a self-developed hot-rolling equipment. The bionic surface with micron-scale riblets formed spontaneously d...

  2. Analysis of Drag Reduction Methods and Mechanisms of Turbulent

    Science.gov (United States)

    Tao, Liu; Jiegang, Mu; Zhengzan, Shi; Peijian, Zhou

    2017-01-01

    Turbulent flow is a difficult issue in fluid dynamics, the rules of which have not been totally revealed up to now. Fluid in turbulent state will result in a greater frictional force, which must consume great energy. Therefore, it is not only an important influence in saving energy and improving energy utilization rate but also an extensive application prospect in many fields, such as ship domain and aerospace. Firstly, bionic drag reduction technology is reviewed and is a hot research issue now, the drag reduction mechanism of body surface structure is analyzed, such as sharks, earthworms, and dolphins. Besides, we make a thorough study of drag reduction characteristics and mechanisms of microgrooved surface and compliant wall. Then, the relevant drag reduction technologies and mechanisms are discussed, focusing on the microbubbles, the vibrant flexible wall, the coating, the polymer drag reduction additives, superhydrophobic surface, jet surface, traveling wave surface drag reduction, and the composite drag reduction methods. Finally, applications and advancements of the drag reduction technology in turbulence are prospected. PMID:29104425

  3. Analysis of Drag Reduction Methods and Mechanisms of Turbulent

    Directory of Open Access Journals (Sweden)

    Gu Yunqing

    2017-01-01

    Full Text Available Turbulent flow is a difficult issue in fluid dynamics, the rules of which have not been totally revealed up to now. Fluid in turbulent state will result in a greater frictional force, which must consume great energy. Therefore, it is not only an important influence in saving energy and improving energy utilization rate but also an extensive application prospect in many fields, such as ship domain and aerospace. Firstly, bionic drag reduction technology is reviewed and is a hot research issue now, the drag reduction mechanism of body surface structure is analyzed, such as sharks, earthworms, and dolphins. Besides, we make a thorough study of drag reduction characteristics and mechanisms of microgrooved surface and compliant wall. Then, the relevant drag reduction technologies and mechanisms are discussed, focusing on the microbubbles, the vibrant flexible wall, the coating, the polymer drag reduction additives, superhydrophobic surface, jet surface, traveling wave surface drag reduction, and the composite drag reduction methods. Finally, applications and advancements of the drag reduction technology in turbulence are prospected.

  4. Parameters of Drag Reducing Polymers and Drag Reduction Performance in Single-Phase Water Flow

    Directory of Open Access Journals (Sweden)

    A. Abubakar

    2014-07-01

    Full Text Available This study presents experimental investigation about the effect of polymer parameters on the performance of the drag reducing polymers in single-phase water flowing in a horizontal pipe of 30.6 mm ID. Master solutions (1000 ppm of ten high-molecular weight polymers were injected at different flow rates to achieve polymer concentrations in the range of 2–40 ppm in the test section. The drag reduction increased with polymer concentration up to 10 ppm, above which it reached a plateau value. While the drag reduction at the plateau value increases with polymer molecular weight, the maximum drag reduction was not affected by the increase in polymer charge density up to 13%. For instance, the maximum drag reduction for anionic polymers with molecular weight 6–8 million Da. and charge density between 5 and 13% was around 60%, which decreased to around 38% for the polymer with charge density of 25%. Ionic polymers provided more drag reduction than nonionic ones. The overall conclusion is that drag reduction depends on polymer ability to form intermolecular associations and/or its flexibility, which can be enhanced by increasing molecular weight, decreasing charge density, and selecting smaller side groups in the main polymer backbone.

  5. Turbulent Taylor-Couette flow over riblets: drag reduction and the effect of bulk fluid rotation

    Science.gov (United States)

    Greidanus, A. J.; Delfos, R.; Tokgoz, S.; Westerweel, J.

    2015-05-01

    A Taylor-Couette facility was used to measure the drag reduction of a riblet surface on the inner cylinder. The drag on the surfaces of the inner and outer cylinders is determined from the measured torque when the cylinders are in exact counter-rotation. The three velocity components in the instantaneous flow field were obtained by tomographic PIV and indicate that the friction coefficients are strongly influenced by the flow regimes and structures. The riblet surface changes the friction at the inner-cylinder wall, which generates an average bulk fluid rotation. A simple model is proposed to distinguish drag changes due to the rotation effect and the riblet effect, as a function of the measured drag change and shear Reynolds number . An uncorrected maximum drag reduction of 5.3 % was found at that corresponds to riblet spacing Reynolds number . For these conditions, the model predicts an azimuthal bulk velocity shift of 1.4 %, which is confirmed by PIV measurements. This shift indicates a drag change due to a rotation effect of -1.9 %, resulting in a net maximum drag reduction of 3.4 %. The results correspond well with earlier reported results and demonstrate that the Taylor-Couette facility is a suitable and accurate measurement tool to characterize the drag performance of surfaces.

  6. Drag Reduction Properties of Nanofluids in Microchannels

    Directory of Open Access Journals (Sweden)

    H.A. Abdulbari

    2015-12-01

    Full Text Available An experimental investigation of the drag reduction (DR individualities in different sized micro channels was carried out with nanopowder additives (NAs (bismuth(III oxide, iron(II/III oxide, silica, and titanium(IV oxide water suspensions/fluids. The primary objective was to evaluate the effects of various concentrations of NAs with different microchannel sizes (50, 100, and 200 µm on the pressure drop of a system in a single phase. A critical concentration was observed with all the NAs, above which increasing the concentration was not effective. Based on the experimental results, the optimum DR percentages were calculated. The optimum percentages were found to be as follows: bismuth III oxides: ~65% DR, 200 ppm and a microchannel size of 100 µm; iron II/III oxides: ~57% DR, 300 ppm, and a microchannel size of 50 µm; titanium IV oxides: ~57% DR, 200 ppm, and a microchannel size of 50 µm, and silica: 55% DR, 200 ppm, and a microchannel size of 50 µm.

  7. Drag reduction of a miniature boat with superhydrophobic grille bottom

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    C. G. Jiang

    2011-09-01

    Full Text Available Water strider can slide on water surface with a very small drag force using its long superhydrophobic legs. Inspired by the water strider legs, we report here a novel design of superhydrophobic grille structure for drag reduction. A miniature boat covered with a superhydrophobic grille at the bottom is fabricated and compared with a normal boat with flat bottom in the same size, and a significant drag reduction is obtained by the former. Experiments also reveal that the grille structure exhibits a remarkable loading capacity supplied by the water surface tension. It is found that the optimal design of such a miniature boat with a considerable loading capacity and a small drag can be realized through controlling the length and the spacing of the grilles. This study shows a new idea to reduce the fluid drag in microfluidics, micro electromechanical system and other engineering areas.

  8. Experimental study of drag reduction in flumes and spillway tunnels

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    Ying-kui Wang

    2010-06-01

    Full Text Available Experiments in an open flume model and spillway tunnel model were carried out using drag reduction techniques. Two drag reduction techniques were adopted in the experiments: polymer addition and coating. The drag reduction effect of a polyacrylamide (PAM solution and dimethyl silicone oil coating were studied in the flume model experiments, and the results were analyzed. Experiments were then carried out with a model of the Xiluodu Hydropower Station, the second largest dam in China. In order to reduce the resistance, the spillway tunnels were internally coated with dimethyl silicone oil. This is the first time that these drag reduction techniques have been applied to so large a hydraulic model. The experimental results show that the coating technique can effectively increase flood discharge. The outlet velocity and the jet trajectory distance are also increased, which enhances the energy dissipation of the spillway tunnel.

  9. Navier slip model of drag reduction by Leidenfrost vapor layers

    KAUST Repository

    Berry, Joseph D.

    2017-10-17

    Recent experiments found that a hot solid sphere that is able to sustain a stable Leidenfrost vapor layer in a liquid exhibits significant drag reduction during free fall. The variation of the drag coefficient with Reynolds number deviates substantially from the characteristic drag crisis behavior at high Reynolds numbers. Measurements based on liquids of different viscosities show that the onset of the drag crisis depends on the viscosity ratio of the vapor to the liquid. Here we attempt to characterize the complexity of the Leidenfrost vapor layer with respect to its variable thickness and possible vapor circulation within, in terms of the Navier slip model that is defined by a slip length. Such a model can facilitate tangential flow and thereby alter the behavior of the boundary layer. Direct numerical and large eddy simulations of flow past a sphere at moderate to high Reynolds numbers (102≤Re≤4×104) are employed to quantify comparisons with experimental results, including the drag coefficient and the form of the downstream wake on the sphere. This provides a simple one parameter characterization of the drag reduction phenomenon due to a stable vapor layer that envelops a solid body.

  10. Navier slip model of drag reduction by Leidenfrost vapor layers

    Science.gov (United States)

    Berry, Joseph D.; Vakarelski, Ivan U.; Chan, Derek Y. C.; Thoroddsen, Sigurdur T.

    2017-10-01

    Recent experiments found that a hot solid sphere that is able to sustain a stable Leidenfrost vapor layer in a liquid exhibits significant drag reduction during free fall. The variation of the drag coefficient with Reynolds number deviates substantially from the characteristic drag crisis behavior at high Reynolds numbers. Measurements based on liquids of different viscosities show that the onset of the drag crisis depends on the viscosity ratio of the vapor to the liquid. Here we attempt to characterize the complexity of the Leidenfrost vapor layer with respect to its variable thickness and possible vapor circulation within, in terms of the Navier slip model that is defined by a slip length. Such a model can facilitate tangential flow and thereby alter the behavior of the boundary layer. Direct numerical and large eddy simulations of flow past a sphere at moderate to high Reynolds numbers (1 02≤Re≤4 ×1 04) are employed to quantify comparisons with experimental results, including the drag coefficient and the form of the downstream wake on the sphere. This provides a simple one parameter characterization of the drag reduction phenomenon due to a stable vapor layer that envelops a solid body.

  11. Drag reduction capability of uniform blowing in supersonic wall-bounded turbulent flows

    Science.gov (United States)

    Kametani, Yukinori; Kotake, Ayane; Fukagata, Koji; Tokugawa, Naoko

    2017-12-01

    Drag reduction capability of uniform blowing in supersonic turbulent boundary layers is investigated by means of direct numerical simulation of channel flows with uniform blowing on one side and suction on the other. The bulk Reynolds number based on the bulk density, the bulk mean velocity, the channel half-width, and the viscosity on the wall is set to Reb=3000 . The bulk Mach number is set at 0.8 and 1.5 to investigate a subsonic and a supersonic condition, respectively. The amplitude of the blowing or suction is set to be 0.1%, 0.3%, or 0.5% of the bulk mass flow rate. At both Mach numbers, modifications of the mean streamwise velocity profiles with blowing and suction are found to be similar to those in an incompressible turbulent channel flow: The skin friction is reduced on the blowing side, while it is increased on the suction side. As for the drag reducing effect of blowing, the drag reduction rate and net-energy saving rate are hardly affected by the Mach number, while the control gain is increased with the increase of Mach number due to the increased density near the wall. The compressibility effect of drag reduction and enhancement is also examined using the physical decomposition of the skin friction drag. A noticeable Mach number effect is found only for the contribution terms containing the viscosity, which is increased by the increased temperature.

  12. Numerical analysis of drag and lift reduction of square cylinder

    Directory of Open Access Journals (Sweden)

    Prasenjit Dey

    2015-12-01

    Full Text Available Flow around an extended triangular solid (thorn attached to a square cylinder is investigated numerically. The numerical analysis is carried out at low Reynolds number, Re = 100 & 180 for different non-dimensional thorn lengths (l΄ = 0. 2, 0.4 & 0.6, different inclination angles (θ = 5°, 10°, 15° and 20° and two different thorn positions. It is found that drag and lift reduction can be achieved by attaching the thorn on a square cylinder. It is observed that the fluctuation of the drag force as well as the lift force is reduced and there is a comparatively large variation of drag and lift when the thorn is placed at the front stagnation point instead of placing at rear stagnation point. The reduction of drag and lift coefficient are directly proportional to thorn length and thorn inclination angle. It is found that the drag and lift are minimized by 16% & 46% for Re = 100 respectively, and 22% & 60% for Re = 180 compared to a square model (without thorn.

  13. Experimental investigation of drag reduction by forward facing high ...

    Indian Academy of Sciences (India)

    Josyula et al. 2001; Hayashi & Asoy 2003; Balla Venukumar et al 2006). Drag reduction by counterflowing supersonic jet for a 60. ◦ apex angle blunt cone is investigated in the HST2 shock tunnel at a flow Mach number of 8. Some of the results ...

  14. Experimental investigation of drag reduction by forward facing high ...

    Indian Academy of Sciences (India)

    ... a matter of great design concern. Preliminary experimental results for the drag reduction by a forward-facing supersonic air jet for a 60° apex-angle blunt cone at a flow Mach number of 8 are presented in this paper. The measurements are carried out using an accelerometer-based balance system in the hypersonic shock ...

  15. Recent Progress in Polymer Drag Reduction

    Science.gov (United States)

    1974-10-01

    polysaccharides as friction-reducing agents were reported [121; a linseed-gum extract gave approximately the rame friction-reduan« performance as the...polymers is the natural polysaccharide okra [37], which has the advantage of good compatibility with blood, having been used as a blood plasma...substitute. In pulsile flow, okra gives a good friction-reduction effect, extending to Reynolds numbers below the normal transition for Newtonian fluids

  16. Geometry Mediated Drag Reduction in Taylor-Couette Flows

    Science.gov (United States)

    Raayai, Shabnam; McKinley, Gareth

    2015-11-01

    Micro-scale ribbed surfaces have been shown to be able to modify surface properties such as skin friction on both natural and fabricated surfaces. Previous experiments have shown that ribbed surfaces can reduce skin friction in turbulent flow by up to 4-8% in the presence of zero or mild pressure gradients. Our previous computations have shown a substantial reduction in skin friction using micro-scaled ribs of sinusoidal form in high Reynolds number laminar boundary layer flow. The mechanism of this reduction is purely viscous, through a geometrically-controlled retardation of the flow in the grooves of the surface. The drag reduction achieved depends on the ratio of the amplitude to the wavelength of the surface features and can be presented as a function of the wavelength expressed in dimensionless wall units. Here we extend this work, both experimentally and numerically, to consider the effect of similar ribs on steady viscous flow between concentric cylinders (Taylor-Couette flow). For the experimental work, the inner rotating cylinder (rotor) is machined with stream-wise V-groove structures and experiments are performed with fluids of different viscosity to compare the measured frictional torques to the corresponding values on a smooth flat rotor as a measure of drag reduction. The numerical work is performed using the OpenFOAM®open source software to compare the results and understand the physical mechanisms underlying this drag reduction phenomenon.

  17. Frictional Drag Reduction by Bubbles in Taylor-Couette Flow

    Science.gov (United States)

    Murai, Yuichi; Oiwa, Hiroshi; Takeda, Yasushi

    2006-11-01

    Frictional drag reduction provided with small bubbles is investigated experimentally using a Couette-Taylor flow system, i.e. shear flow between concentric cylinders. Torque and bubble behavior are measured up to Re=4500 when air bubbles are injected constantly and rise through the cells. Silicone oil is used for avoiding uncertain interfacial property of bubbles as well as for keeping nearly mono-sized bubbles. We assess the effect of drag reduction with two types of evaluation factors, i.e. sensitivity and power gain. The sensitivity exceeds unity at Redrag is reduced more than the drop of mixture density. This originates from accumulation of bubbles into the rotating inner cylinder, which is little affected by turbulence. The power gain, which is defined by drag reduction power per bubble injection power, takes the highest value of O(10) at higher Re numbers around 2500. The image processing measurement finds this reason to be disappearance of azimuthal waves when the organized bubbles distribution transits from toroidal to spiral modes. Moreover, the axial spacing of bubble clouds expands during the transition, enforcing the reduction of momentum exchange.

  18. Drag reduction in silica nanochannels induced by graphitic wall coatings

    DEFF Research Database (Denmark)

    Wagemann, Enrique; Walther, Jens Honore; Zambrano, Harvey

    Transport of water in hydrophilic nanopores is of significant technological and scientific interest. Water flow through hydrophilic nanochannelsis known to experience enormous hydraulic resistance. Therefore, drag reduction is essential for the development of highly efficient nanofluidic devices....... In this work, we propose the use of graphitic materials as wall coatings in hydrophilic silica nanopores. Specifically, by conducting atomistic simulations, we investigate the flow inside slit and cylindrical silica channels with walls coated with graphene (GE) layers and carbonnanotubes (CNTs), respectively...... in the nanochannels. The influence of channel size is investigated by systematically varying channel heights and nanopore diameters. In particular, we present the computed water density and velocity profiles, volumetric flow rates, slip lengths and flow enhancements, to clearly demonstrate the drag reduction...

  19. Numerical study on aerodynamic drag reduction of passenger cars

    OpenAIRE

    Sanchez Martinez, Javier

    2015-01-01

    The scope of this work is to identify potential improvements on Passenger cars Aerodynimcs (Drag reduction and Downforce increase) to help to minimize fuel consumption and hence reduce exhaust emisions. The Ahmed body (Bluff body) is representative of a passenger car under aerodynamical point of view. A lot of studies and literature exists as far as test reports of the Ahmed body on wind tunel tests. This work can be divided onto 2 steps. First step is to perform qualitative numerical simulat...

  20. Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity.

    Science.gov (United States)

    Bhushan, Bharat

    2011-01-01

    The emerging field of biomimetics allows one to mimic biology or nature to develop nanomaterials, nanodevices, and processes which provide desirable properties. Hierarchical structures with dimensions of features ranging from the macroscale to the nanoscale are extremely common in nature and possess properties of interest. There are a large number of objects including bacteria, plants, land and aquatic animals, and seashells with properties of commercial interest. Certain plant leaves, such as lotus (Nelumbo nucifera) leaves, are known to be superhydrophobic and self-cleaning due to the hierarchical surface roughness and presence of a wax layer. In addition to a self-cleaning effect, these surfaces with a high contact angle and low contact angle hysteresis also exhibit low adhesion and drag reduction for fluid flow. An aquatic animal, such as a shark, is another model from nature for the reduction of drag in fluid flow. The artificial surfaces inspired from the shark skin and lotus leaf have been created, and in this article the influence of structure on drag reduction efficiency is reviewed. Biomimetic-inspired oleophobic surfaces can be used to prevent contamination of the underwater parts of ships by biological and organic contaminants, including oil. The article also reviews the wetting behavior of oil droplets on various superoleophobic surfaces created in the lab.

  1. Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity

    Directory of Open Access Journals (Sweden)

    Bharat Bhushan

    2011-02-01

    Full Text Available The emerging field of biomimetics allows one to mimic biology or nature to develop nanomaterials, nanodevices, and processes which provide desirable properties. Hierarchical structures with dimensions of features ranging from the macroscale to the nanoscale are extremely common in nature and possess properties of interest. There are a large number of objects including bacteria, plants, land and aquatic animals, and seashells with properties of commercial interest. Certain plant leaves, such as lotus (Nelumbo nucifera leaves, are known to be superhydrophobic and self-cleaning due to the hierarchical surface roughness and presence of a wax layer. In addition to a self-cleaning effect, these surfaces with a high contact angle and low contact angle hysteresis also exhibit low adhesion and drag reduction for fluid flow. An aquatic animal, such as a shark, is another model from nature for the reduction of drag in fluid flow. The artificial surfaces inspired from the shark skin and lotus leaf have been created, and in this article the influence of structure on drag reduction efficiency is reviewed. Biomimetic-inspired oleophobic surfaces can be used to prevent contamination of the underwater parts of ships by biological and organic contaminants, including oil. The article also reviews the wetting behavior of oil droplets on various superoleophobic surfaces created in the lab.

  2. 5th Drag Reduction in Engineering Flows Meeting

    CERN Document Server

    1991-01-01

    The European Drag Reduction Meeting has been held on 15th and 16th November 1990 in London. This was the fifth of the annual European meetings on drag reduction in engineering flows. The main objective of this meeting was to discuss up-to-date results of drag reduction research carried out in Europe. The organiser has adopted the philosophy of discussing the yesterday's results rather than the last year's results. No written material has therefore been requested for the meeting. It was only after the meeting the submission of papers was requested to the participants, from which 16 papers were selected for this proceedings volume. The meeting has attracted a record number of participants with a total of 52 researchers from seven European countries, U. K. , France, Germany, the Netherlands, Italy, Switzerland and U. S. S. R. as well as from Japan, Canada and Australia. The subjects covered in this proceedings volume include riblets, LEBUs (Large Eddy Break-Up device), surface roughness, compliant surfaces and p...

  3. Drag reduction using wrinkled surfaces in high Reynolds number laminar boundary layer flows

    Science.gov (United States)

    Raayai-Ardakani, Shabnam; McKinley, Gareth H.

    2017-09-01

    Inspired by the design of the ribbed structure of shark skin, passive drag reduction methods using stream-wise riblet surfaces have previously been developed and tested over a wide range of flow conditions. Such textures aligned in the flow direction have been shown to be able to reduce skin friction drag by 4%-8%. Here, we explore the effects of periodic sinusoidal riblet surfaces aligned in the flow direction (also known as a "wrinkled" texture) on the evolution of a laminar boundary layer flow. Using numerical analysis with the open source Computational Fluid Dynamics solver OpenFOAM, boundary layer flow over sinusoidal wrinkled plates with a range of wavelength to plate length ratios ( λ / L ), aspect ratios ( 2 A / λ ), and inlet velocities are examined. It is shown that in the laminar boundary layer regime, the riblets are able to retard the viscous flow inside the grooves creating a cushion of stagnant fluid that the high-speed fluid above can partially slide over, thus reducing the shear stress inside the grooves and the total integrated viscous drag force on the plate. Additionally, we explore how the boundary layer thickness, local average shear stress distribution, and total drag force on the wrinkled plate vary with the aspect ratio of the riblets as well as the length of the plate. We show that riblets with an aspect ratio of close to unity lead to the highest reduction in the total drag, and that because of the interplay between the local stress distribution on the plate and stream-wise evolution of the boundary layer the plate has to exceed a critical length to give a net decrease in the total drag force.

  4. Boundary layer thickness effect on boattail drag. [wind tunnel tests for drag reduction

    Science.gov (United States)

    Blaha, B. J.; Chamberlin, R.; Bober, L. J.

    1976-01-01

    A combined experimental and analytical program has been conducted at the NASA Lewis Research Center, to investigate the effects of boundary layer changes on the flow over high angle boattail nozzles. The tests were run on an isolated axisymmetric sting mounted model. Various boattail geometries were investigated at high subsonic speeds over a range of boundary layer thicknesses. In general, boundary layer effects were small at speeds up to Mach 0.8. However, at higher speeds significant regions of separated flow were present on the boattail. When separation was present large reductions in boattail drag resulted with increasing boundary layer thickness. The analysis predicts both of these trends.

  5. 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.

  6. Roles of size and kinematics in drag reduction for two tandem flexible foils

    Science.gov (United States)

    Chao, Li-Ming; Zhang, Dong; Pan, Guang

    2017-11-01

    The effect of size and kinematics difference between two tandem flexible foils on drag reduction have been numerically studied. Compared with single foil, it is found that the kinematics difference between two foils would not play a significant role in reducing drag, while the size difference between two foils significantly affects the drag reduction in this two foil system. For leading foil, it always enjoys drag reduction and the highest drag reduction can be observed at bigger size difference and gap distance between two foil as 22%. For trailing foil, it suffers drag increase when the gap distance between two foils is smaller, while it enjoys drag decrease when the size difference between two foils is bigger enough. The hydrodynamic interaction between such actively undulated foils also has been uncovered and used to explain the mechanisms of drag reduction.

  7. Front-crawl stroke-coordination and symmetry: a comparison between timing and net drag force protocols.

    Science.gov (United States)

    Formosa, Danielle P; Sayers, Mark G L; Burkett, Brendan

    2013-01-01

    This study compared stroke-coordination and symmetry using traditional timing methods and net drag force profiles. Twenty elite front-crawl swimmers Federation Internationale de Natation (FINA ranking 908 ± 59) were tested to identify the influence of both gender and breathing. A total of six randomised free-swimming trials were conducted: (i) three breathing, (ii) three non-breathing. Net drag forces were measured using an assisted towing device and the magnitude and location of minimum and maximum was determined to create a stroke symmetry index. Within the breathing condition, there were significant differences between the two symmetry index methods. Using the timing index, all 10 female participants, and seven males, illustrated symmetrical timing. For the net drag force profile, only three females and zero males exhibited a symmetrical minimum net drag force; and only four females and two males demonstrated a symmetrical maximum net drag force index. No differences existed within the non-breathing condition. There was a small (5.2%) difference in the location of maximum net drag force, when stratifying by gender. During the breathing condition, gender also influenced the percentage of overlap for the breathing stroke by 25.2%, and 14.6 % for the non-breathing stroke. A combination of the traditional timing based and net drag force based profile can guide future swimming technique intervention strategies.

  8. Synthetic Effect of Vivid Shark Skin and Polymer Additive on Drag Reduction Reinforcement

    Directory of Open Access Journals (Sweden)

    Huawei Chen

    2014-06-01

    Full Text Available Natural shark skin has a well-demonstrated drag reduction function, which is mainly owing to its microscopic structure and mucus on the body surface. In order to improve drag reduction, it is necessary to integrate microscopic drag reduction structure and drag reduction agent. In this study, two hybrid approaches to synthetically combine vivid shark skin and polymer additive, namely, long-chain grafting and controllable polymer diffusion, were proposed and attempted to mimic such hierarchical topography of shark skin without waste of polymer additive. Grafting mechanism and optimization of diffusion port were investigated to improve the efficiency of the polymer additive. Superior drag reduction effects were validated, and the combined effect was also clarified through comparison between drag reduction experiments.

  9. REVIEW OF PASSIVE DRAG REDUCTION TECHNIQUES FOR BLUFF ROAD VEHICLES

    Directory of Open Access Journals (Sweden)

    Alaman Altaf

    2014-05-01

    Full Text Available ABSTRACT:This paper presents a review of the techniques used to reduce aerodynamic drag over bluff bodies such as cylinders, spheres, 2D bodies with blunt backs and their application to commercial road vehicles.  The recent research carried out on the drag reduction is presented and categorised. A new classification of the techniques is introduced and major contributions under them are shown. It can be concluded that there is not much work done with realistic 3D bluff bodies, especially using passive methods.ABSTRAK: Kertas kerja ini membentangkan kaji selidik semula teknik yang digunakan untuk mengurangkan seret aerodinamik ke atas jasad tubir seperti silinder, sfera, jasad 2D dengan belakang tumpul dan aplikasinya terhadap kenderaan jalan raya komersial. Pengurangan seretan dibentangkan dan dikategorikan dengan kajian terkini. Klasifikasi teknik terkini diperkenalkan dan sumbangan utamanya diperbentangkan.  Secara kesimpulannya terdapat banyak tugasan yang tidak yang dapat dijalankan dengan menggunakan jasad tubir 3D sebenar, terutamanya dengan penggunaan kaedah pasif.

  10. Drag reduction of a rapid vehicle in supercavitating flow

    Directory of Open Access Journals (Sweden)

    D. Yang

    2017-01-01

    Full Text Available Supercavitation is one of the most attractive technologies to achieve high speed for underwater vehicles. However, the multiphase flow with high-speed around the supercavitating vehicle (SCV is difficult to simulate accurately. In this paper, we use modified the turbulent viscosity formula in the Standard K-Epsilon (SKE turbulent model to simulate the supercavitating flow. The numerical results of flow over several typical cavitators are in agreement with the experimental data and theoretical prediction. In the last part, a flying SCV was studied by unsteady numerical simulation. The selected computation setup corresponds to an outdoor supercavitating experiment. Only very limited experimental data was recorded due to the difficulties under the circumstance of high-speed underwater condition. However, the numerical simulation recovers the whole scenario, the results are qualitatively reasonable by comparing to the experimental observations. The drag reduction capacity of supercavitation is evaluated by comparing with a moving vehicle launching at the same speed but without supercavitation. The results show that the supercavitation reduces the drag of the vehicle dramatically.

  11. The research on the drag reduction of a transport aircraft with upswept afterbody using long fins

    Science.gov (United States)

    2016-03-30

    software FLUENT using pressure based coupled solver. The advection term is discretized by second order upwind scheme. The SST k-ω two equation...Undergraduate Student Paper Postgraduate Student Paper The research on the drag reduction of a transport aircraft with upswept afterbody using...height, location and yaw angle of the fins are the sensitive factors of drag reduction . Drag reduction of 21 counts is achieved in wind tunnel test

  12. Drag Reduction for Turbulent Boundary Layer Flows Using an Oscillating Wall

    National Research Council Canada - National Science Library

    Bogard, David

    2000-01-01

    This research program used experimental measurements and computational simulations to study the drag reduction, and the resulting effects on turbulence structure, for a turbulent wall flow subjected...

  13. Fluid Mechanics, Drag Reduction and Advanced Configuration Aeronautics

    Science.gov (United States)

    Bushnell, Dennis M.

    2000-01-01

    This paper discusses Advanced Aircraft configurational approaches across the speed range, which are either enabled, or greatly enhanced, by clever Flow Control. Configurations considered include Channel Wings with circulation control for VTOL (but non-hovering) operation with high cruise speed, strut-braced CTOL transports with wingtip engines and extensive ('natural') laminar flow control, a midwing double fuselage CTOL approach utilizing several synergistic methods for drag-due-to-lift reduction, a supersonic strut-braced configuration with order of twice the L/D of current approaches and a very advanced, highly engine flow-path-integrated hypersonic cruise machine. This paper indicates both the promise of synergistic flow control approaches as enablers for 'Revolutions' in aircraft performance and fluid mechanic 'areas of ignorance' which impede their realization and provide 'target-rich' opportunities for Fluids Research.

  14. Drag reduction and improvement of material transport in creeping films

    Energy Technology Data Exchange (ETDEWEB)

    Scholle, M.; Rund, A.; Aksel, N. [University of Bayreuth, Department of Applied Mechanics and Fluid Dynamics, Bayreuth (Germany)

    2006-01-01

    It is widely accepted that for bodies in turbulent flows a reduction of skin friction can be reached if the surface of the body is provided with small ridges aligned in the local flow direction. This surprising and counterintuitive phenomenon is called the shark-skin effect, motivated from the dermal surface morphology of sharks. In the present article we examine the possibility of resistance reduction due to a rippled surface topography in Stokes flow. We especially analyse the influence of wall riblets perpendicular to the flow direction on the mean transport velocity in gravity-driven creeping film flows following the idea that eddies generated in the valleys of the riblets act like fluid roller bearings and hence may reduce drag. Using a theoretical treatment of the Stokes equations with complex function theory, parameter studies with varying flow rate, bottom amplitude and bottom shape are presented. For the given bottom shapes the maximum enhancement of transport velocity is found by optimising the film thickness. (orig.)

  15. The Effect of Sodium Hydroxide on Drag Reduction using a Biopolymer.

    Directory of Open Access Journals (Sweden)

    Singh Harvin Kaur A/P Gurchran

    2014-07-01

    Full Text Available Drag reduction is observed as reduced frictional pressure losses under turbulent flow conditions and hence, substantially increases the flowrate of the fluid. Practical application includes water flooding system, pipeline transport and drainage system. Drag reduction agent, such as polymers, can be introduced to increase the flowrate of water flowing, reducing the water accumulation in the system and subsequently lesser possibility of heavy flooding. Currently used polymer as drag reduction agents is carboxymethylcellulose, to name one. This is a synthetic polymer which will seep into the ground and further harm our environment in excessive use of accumulation. A more environmentally-friendly drag reduction agent, such as the polymer derived from natural sources or biopolymer, is then required for such purpose. As opposed to the synthetic polymers, the potential of biopolymers as drag reduction agents, especially those derived from a local plant source, are not extensively explored. The drag reduction of a polymer produced from a local plant source within the turbulent regime will be explored and assessed in this study using a rheometer where a reduced a torque produced can be perceived as a reduction of drag. The cellulose powder was converted to carboxymethylcellulose (CMC by etherification process using sodium monochloroacetate and sodium hydroxide. The carboxymethylation reaction then was optimized against concentration of NaOH. The research is structured to focus on producing the biopolymer and also assess the drag reduction ability of the biopolymer produced against concentration of sodium hydroxide.

  16. Effect of Polymer Type and Mixing of Polymers on Drag Reduction in Turbulent Pipe Flow

    Directory of Open Access Journals (Sweden)

    Salam Hadi Hussein

    2017-05-01

    Full Text Available The paper reports on studies on effect of the type of polymer on drag reduction. The study conducted through circular pipe using Carboxy Methyl Cellulose (CMC, Xanthan gum (XG and their mixing in equal ratios as additives in pipe of diameter 0.0381m. The study covered range of parameters like concentration, mean velocity and angle of inclination of pipe. The maximum drag reduction observed was about 58%, 46% and 46% for the three polymers respectively. It is found that the drag reduction for the mixture is close to the drag reduction for XG polymer. The SPSS program has been used for correlate the data that have been obtained. The drag reduction percentage is correlated in terms of Reynolds number Re, additive concentration C (ppm and angle of inclination of pipe (deg, and the relations obtained is mentioned.

  17. The Reduction in Drag of a Forward-sloping Windshield

    Science.gov (United States)

    Jacobs, Eastman N

    1933-01-01

    This paper gives results of a short investigation of the drag of a forward-sloping closed-cabin windshield. The drag of the windshield in both the original and a final modified form was determined from tests in the variable-density wind tunnel. The final form of the windshield was arrived at by modifying the original as the result of flow observations in the N.A.C.A. smoke tunnel. The investigation studied the utility of the N.A.C.A. smoke tunnel as applied to reducing the drag of objects for which the full dynamic scale could not be approached in the smoke tunnel, but designers should find the results of the flow observations and drag measurements of value. They show that most of the large drag added by the original windshield is eliminated by the modification of the windshield to the final form.

  18. Effect of structure height on the drag reduction performance using rotating disk apparatus

    Science.gov (United States)

    Rashed, Musaab K.; Abdulbari, Hayder A.; Amran Mohd Salleh, Mohamad; Halim Shah Ismail, M.

    2017-02-01

    The drag reduction characteristics in a rotating disk apparatus were investigated by using structured disks with different riblet types and dimensions. Two disk types were fabricated with right angle triangular (RAT) grooves and space v-shape (SV) grooves, with six dimensions for each type. A high-accuracy rotating disk apparatus was fabricated and then used to investigate the turbulent drag reduction characterization of the disk in diesel fuel. In this work, the effects of several parameters are investigated; riblet types, riblet dimensions, and rotational disk speed (rpm) on the drag reduction performance. It was found that the surface structure of the disk reduced the drag, this was clearly seen from the comparison of torque values of smooth and structured disks. Drag reduction for structured disks was higher than that for smooth disks, and SV-grooves showed better drag reduction performance than RAT-grooves. In addition, it was observed that the drag reduction performance increased with decreasing groove height for both groove types. The maximum drag reduction achieved in this study was 37.368% for SV-groove at 1000 rpm, compared with 30% for RAT-groove, at the same rotational speed.

  19. Characterization of the LISA Pathfinder Drag Reduction System

    Science.gov (United States)

    Slutsky, Jacob; LISA Pathfinder Team

    2016-03-01

    The LISA Pathfinder (LPF) mission launched in December 2015 with operations beginning March 2016. LPF is a technology demonstration mission built to prove and fully characterize the performance of the use of drag free test masses as Gravitational Reference Sensors (GRS) for future space based gravitational-wave observatories. As a joint ESA-NASA mission, LPF is comprised of both European and NASA payloads, the LISA Technology Package (LTP) and Disturbance Reduction System (DRS), respectively. DRS includes Colloid Micro-Newton Thruster (CMNT) systems, to precisely maneuver the spacecraft without disturbing the GRS, and a control system that directs spacecraft and test mass actuation. In order to fully characterize DRS/CMNT performance, we have developed a series of experiments, to take place during DRS operations beginning later this year. We have built analysis pipelines, validated on simulated data, to rapidly process experimental data and to identify any performance issues as they occur. European partners have developed the LTP Data Analysis (LTPDA) Matlab extension, and we have adapted and expanded this to DRS missions as the basis of our analysis pipelines. I will discuss the anticipated DRS performance and measurement accuracy, illustrated on simulated data.

  20. Hypersonic wave drag reduction performance of cylinders with repetitive laser energy depositions

    Energy Technology Data Exchange (ETDEWEB)

    Fang, J; Hong, Y J; Li, Q; Huang, H, E-mail: fangjuan314@163.com [Academy of Equipment Command and Technology, Post Box 3380-86, Huairou Dis. Beijing 101416 (China)

    2011-02-01

    It has been widely research that wave drag reduction on hypersonic vehicle by laser energy depositions. Using laser energy to reduce wave drag can improve vehicle performance. A second order accurate scheme based on finite-difference method and domain decomposition of structural grid is used to compute the drag performance of cylinders in a hypersonic flow of Mach number 2 at altitude of 15km with repetitive energy depositions. The effects of frequency on drag reduction are studied. The calculated results show: the recirculation zone is generated due to the interaction between bow shock over the cylinder and blast wave produced by energy deposition, and a virtual spike which is supported by an axis-symmetric recirculation, is formed in front of the cylinder. By increasing the repetitive frequency, the drag is reduced and the oscillation of the drag is decreased; however, the energy efficiency decreases by increasing the frequency.

  1. The Berlin oil channel for drag reduction research

    Science.gov (United States)

    Bechert, D. W.; Hoppe, G.; van der Hoeven, J. G. Th.; Makris, R.

    1992-03-01

    For drag reduction research an oil channel has been designed and built. It is also well suited for investigations on turbulent flow and in particular on the dynamics of the viscous sublayer near the wall. The thickness of the viscous sublayer ( y += 5) can be varied between 1 and 4 mm. Surfaces with longitudinal ribs (“riblets”), which are known to reduce drag, can have fairly large dimensions. The lateral spacing of the ribs can lie between 3 and 10 mm, as compared to about 0.5 mm spacing for conventional wind tunnels. It has been proved by appropriate tests that the oil channel data are completely equivalent to data from other facilities and with other mean flow geometries. However, the shear stress data from the new oil channel are much more accurate than previous data due to a novel differential shear force balance with an accuracy of ±0.2%. In addition to shear stress measurements, velocity fluctuation measurements can be carried out with hot wire or hot film probes. In order to calibrate these probes, a moving sled permits to emulate the flow velocities with the fluid in the channel at rest. A number of additional innovations contribute to the improvement of the measurements, such as, e.g., (i) novel adjustable turbulators to maintain equilibrium turbulence in the channel, (ii) a “bubble trap” to avoid bubbles in the channel at high flow velocities, (iii) a simple method for the precision calibration of manometers, and (iv) the elimination of (Coulomb) friction in ball bearings. This latter fairly general invention is used for the wheels of the calibration unit of the balance. The channel has a cross section of 25 × 85 cm and is 11 m long. It is filled with about 4.5 metric tons of baby oil (white paraffine oil), which is transparent and odorless like water. The kinematic viscosity of the oil is v = 1.2×10-5 m2/s, and the highest (average) velocity is 1.29 m/s. Thus, the Reynolds number range (calculated with the channel width, 0.25 m) lies between

  2. Turbulent Taylor–Couette flow over riblets : Drag reduction and the effect of bulk fluid rotation

    NARCIS (Netherlands)

    Greidanus, A.J.; Delfos, R.; Tokgoz, S.; Westerweel, J.

    2015-01-01

    A Taylor–Couette facility was used to measure the drag reduction of a riblet surface on the inner cylinder. The drag on the surfaces of the inner and outer cylinders is determined from the measured torque when the cylinders are in exact counter-rotation. The three velocity components in the

  3. Drag reduction by herringbone riblet texture in direct numerical simulations of turbulent channel flow

    NARCIS (Netherlands)

    Benschop, H.O.G.; Breugem, W.P.

    2017-01-01

    A bird-feather-inspired herringbone riblet texture was investigated for turbulent drag reduction. The texture consists of blade riblets in a converging/diverging or herringbone pattern with spanwise wavelength Λf. The aim is to quantify the drag change for this texture as compared to a smooth wall

  4. Concentrated energy addition for active drag reduction in hypersonic flow regime

    Science.gov (United States)

    Ashwin Ganesh, M.; John, Bibin

    2018-01-01

    Numerical optimization of hypersonic drag reduction technique based on concentrated energy addition is presented in this study. A reduction in wave drag is realized through concentrated energy addition in the hypersonic flowfield upstream of the blunt body. For the exhaustive optimization presented in this study, an in-house high precision inviscid flow solver has been developed. Studies focused on the identification of "optimum energy addition location" have revealed the existence of multiple minimum drag points. The wave drag coefficient is observed to drop from 0.85 to 0.45 when 50 Watts of energy is added to an energy bubble of 1 mm radius located at 74.7 mm upstream of the stagnation point. A direct proportionality has been identified between energy bubble size and wave drag coefficient. Dependence of drag coefficient on the upstream added energy magnitude is also revealed. Of the observed multiple minimum drag points, the energy deposition point (EDP) that offers minimum wave drag just after a sharp drop in drag is proposed as the most optimum energy addition location.

  5. Drag reduction by microbubbles in turbulent flows: the limit of minute bubbles.

    Science.gov (United States)

    L'vov, Victor S; Pomyalov, Anna; Procaccia, Itamar; Tiberkevich, Vasil

    2005-05-06

    Drag reduction by microbubbles is a promising engineering method for improving ship performance. A fundamental theory of the phenomenon is lacking, however, making actual design quite haphazard. We offer here a theory of drag reduction by microbubbles in the limit of very small bubbles, when the effect of the bubbles is mainly to normalize the density and the viscosity of the carrier fluid. The theory culminates with a prediction of the degree of drag reduction given the concentration profile of the bubbles. Comparisons with experiments are discussed and the road ahead is sketched.

  6. Skin friction drag reduction in turbulent flow using spanwise traveling surface waves

    Science.gov (United States)

    Musgrave, Patrick F.; Tarazaga, Pablo A.

    2017-04-01

    A major technological driver in current aircraft and other vehicles is the improvement of fuel efficiency. One way to increase the efficiency is to reduce the skin friction drag on these vehicles. This experimental study presents an active drag reduction technique which decreases the skin friction using spanwise traveling waves. A novel method is introduced for generating traveling waves which is low-profile, non-intrusive, and operates under various flow conditions. This wave generation method is discussed and the resulting traveling waves are presented. These waves are then tested in a low-speed wind tunnel to determine their drag reduction potential. To calculate the drag reduction, the momentum integral method is applied to turbulent boundary layer data collected using a pitot tube and traversing system. The skin friction coefficients are then calculated and the drag reduction determined. Preliminary results yielded a drag reduction of ≍ 5% for 244Hz traveling waves. Thus, this novel wave generation method possesses the potential to yield an easily implementable, non-invasive drag reduction technology.

  7. Dielectric barrier discharge actuator for vehicle drag reduction at highway speeds

    Directory of Open Access Journals (Sweden)

    Subrata Roy

    2016-02-01

    Full Text Available We propose and demonstrate reduction of aerodynamic drag for a realistic geometry at highway speeds using serpentine dielectric barrier discharge actuators. A comparable linear plasma actuator fails to reduce the drag at these speeds. Experimental data collected for linear and serpentine plasma actuators under quiescent operating conditions show that the serpentine design has profound effect on near wall flow structure and resulting drag. For certain actuator arrangement, the measured drag reduced by over 14% at 26.8 m/s (60 mph and over 10% at 31.3 m/s (70 mph opening up realistic possibility of reasonable energy savings for full scale ground vehicles. In addition, the power consumption data and drag reduction effectiveness for different input signals are also presented.

  8. The Combination of Polymer, Compliant Wall, and Microbubble Drag Reduction Schemes

    Directory of Open Access Journals (Sweden)

    Boris N. Semenov

    2011-01-01

    Full Text Available The promising study of turbulence management by joint use of compliant coatings with other drag reduction means is proposed. Its outlooks are conditioned by different considered factors and confirmed by the first experimental and theoretical results.

  9. Experimental Investigation of Tunnel Discharge Ability by Using Drag Reduction Techniques

    Directory of Open Access Journals (Sweden)

    Ying-kui WANG

    2010-06-01

    Full Text Available The experiments in an open flume model and in the spillway tunnel models were carried out by using drag reduction technique. The drag reduction experiments in open channel model adopted two techniques: polymer addition and coating. The drag reduction effect of polyacrylamide (PAM solution and the dimethyl silicone oil coating were studied by the flume model experiments, and the results were satisfied. Then the experiments were carried out in the model of a Hydropower station, which is the second largest dam in China. In order to reduce the resistance, the spillway tunnel models were coated inside with the dimethyl silicone oil. It is the first time that applying the drag reduction technique in the large hydraulic model. The experimental results show that the coating technique can effectively increase the ability of flood discharge. The outlet velocity and the jet trajectory distance were also increased, which is beneficial to the energy dissipation of the spillway tunnel.

  10. Assessments of Bubble Dynamics Model and Influential Parameters in Microbubble Drag Reduction

    National Research Council Canada - National Science Library

    Skudarnov, P. V; Lin, C. X

    2006-01-01

    .... The effects of mixture density variation, free stream turbulence intensity, free stream velocity, and surface roughness on the microbubble drag reduction were studied using a single phase model based...

  11. Aerodynamic Drag Reduction Apparatus For Wheeled Vehicles In Ground Effect

    Science.gov (United States)

    Ortega, Jason M.; Salari, Kambiz

    2005-12-13

    An apparatus for reducing the aerodynamic drag of a wheeled vehicle in a flowstream, the vehicle having a vehicle body and a wheel assembly supporting the vehicle body. The apparatus includes a baffle assembly adapted to be positioned upstream of the wheel assembly for deflecting airflow away from the wheel assembly so as to reduce the incident pressure on the wheel assembly.

  12. Drag reduction in bubbly Taylor-Couette turbulence

    NARCIS (Netherlands)

    van den Berg, Th.H.; Luther, S.; Lathrop, Daniel P.; Lohse, Detlef

    2005-01-01

    In Taylor-Couette flow the total energy dissipation rate and therefore the drag can be determined by measuring the torque on the system. We do so for Reynolds numbers between Re=7×104 and Re=106 after having injected (i) small bubbles (R=1  mm) up to a volume concentration of α=5% and (ii) buoyant

  13. Drag reduction by applying speedstrips on rowing oars

    NARCIS (Netherlands)

    Kuyt, C. B.; Greidanus, A.J.; Westerweel, J.; Jansen, A.J.

    2016-01-01

    The objective of this study was to determine the advantage of the application of speedstrips to rowing oars for a lightweight single sculler. The research method comprehended three steps: (1) the analysis of the rowing oar movement, (2) the determination of the change in drag and (3) the

  14. Investigation of drag reduction through a flapping mechanism on circular cylinder

    Science.gov (United States)

    Asif, Md. Asafuddoula; Gupta, Avijit Das; Rana, M. D. Juwel; Ahmed, Dewan Hasan

    2016-07-01

    During flapping wing, a bird develops sufficient lift force as well as counteracts drag and increases its speed through different orientations of feathers on the flapping wings. Differently oriented feathers play a significant role in drag reduction during flying of a bird. With an objective to investigate the effect of installation of such flapping mechanism as a mean of drag reduction in case of flow over circular cylinder, this concept has been implemented through installation of continuous and mini flaps, made of MS sheet metal, where flaps are oriented at different angles as like feathers of flapping wings. The experiments are carried out in a subsonic wind tunnel. After validation and comparison with conventional result of drag analysis of a single cylinder, effects of flapping with Reynolds number variation, implementation of different orientations of mini flaps and variation of different interspacing distance between mini flaps are studied to find the most effective angle of attack of drag reduction on the body of circular cylinder. This research show that, installation of continuous flap reduces value of drag co-efficient, CD up to 66%, where as mini flaps are found more effective by reducing it up to 73%. Mini flaps of L/s=6.25, all angled at 30O, at the 30O angular position on the body of circular cylinder has been found the most effective angle of attack for drag reduction in case of flow over circular cylinder.

  15. Aerodynamic Drag Reduction for a Generic Truck Using Geometrically Optimized Rear Cabin Bumps

    Directory of Open Access Journals (Sweden)

    Abdellah Ait Moussa

    2015-01-01

    Full Text Available The continuous surge in gas prices has raised major concerns about vehicle fuel efficiency, and drag reduction devices offer a promising strategy. In this paper, we investigate the mechanisms by which geometrically optimized bumps, placed on the rear end of the cabin roof of a generic truck, reduce aerodynamic drag. The incorporation of these devices requires proper choices of the size, location, and overall geometry. In the following analysis we identify these factors using a novel methodology. The numerical technique combines automatic modeling of the add-ons, computational fluid dynamics and optimization using orthogonal arrays, and probabilistic restarts. Numerical results showed reduction in aerodynamic drag between 6% and 10%.

  16. EXPERIMENTAL STUDY ON THE COLLABORATIVE DRAG REDUCTION PERFORMANCE OF A SURFACTANT SOLUTION IN GROOVED CHANNELS

    Directory of Open Access Journals (Sweden)

    Chonghai Huang

    Full Text Available Abstract Turbulence with a relatively larger vortex is obtained in drag-reducing surfactant solution, which provides an excellent condition for the application of small scale grooves. In this work, the coupling drag reduction performance of surfactant solution and grooves was experimentally investigated to explore the complementary possibility between their drag reduction mechanisms. The cationic surfactant cetyltrimethyl ammonium chloride (CTAC mixed with the counterion salt sodium salicylate (NaSal was experimented in smooth or grooved channel, respectively, at the mass concentrations of 50-150 ppm. It was found that the surfactant solutions gave more effective drag reduction in the grooved channel by the interaction between the "restriction effect" and "peak effect" of grooves. Moreover, the critical temperature and critical Reynolds number of the surfactant solution were smaller in the grooved channel, and the friction factor in the grooved channel increased much more rapidly than that in the smooth channel when Re is larger than a critical value.

  17. Drag reduction by natural polymeric additives in PMDS microchannel: Effect of types of additives

    Directory of Open Access Journals (Sweden)

    Ling Fiona W.M.

    2017-01-01

    Full Text Available Drag reduction technology was used in medical applications to enhance the blood flow in semiclogged blood streams which can be an alternative treatment for atherosclerosis. In this present study, natural polymeric drag reducing additives (DRA was introduced to replace synthetic polymer which has the possibility of bringing side effects to human health. Three different sources, namely okra, aloe vera and hibiscus were utilized to extract the natural polymeric additives which were then tested in custom made microchannel simulating human heart blood vessels. The performance of different types of additives was evaluated using pressure measurements. The maximum drag reduction up to 63.48% is achieved using 300 ppm of hibiscus mucilage at operating pressure of 50 mbar. In this present work, hibiscus showed the best drag reduction performance, giving the highest %FI in most of the cases. This experimental results proved that these natural polymeric additives could be utilized as DRA in enhancing the blood flow in semiclogged blood streams.

  18. The Use of Biobased Surfactant Obtained by Enzymatic Syntheses for Wax Deposition Inhibition and Drag Reduction in Crude Oil Pipelines

    National Research Council Canada - National Science Library

    Zhihua Wang; Xueying Yu; Jiaxu Li; Jigang Wang; Lei Zhang

    2016-01-01

    .... In order to determine the role of drag-reducing surfactant additives in the transportation of crude oils, experiments of wax deposition inhibition and drag reduction of different oil in pipelines...

  19. Verification of drag-reduction capabilities of stiff compliant coatings in air flow at moderate speeds

    Directory of Open Access Journals (Sweden)

    Andrey V. Boiko

    2011-12-01

    Full Text Available Skin frictional drag reduction efficiency of “stiff” compliant coating was investigated in a wind tunnel experiment. Flat plate compliant coating inserts were installed in a wind tunnel and the measurements of skin frictional drag and velocity field were carried out. The compliant coatings with varying viscoelastic properties had been prepared using different composition. In order to optimize the coating thickness, the most important design parameter, the dynamic viscoelastic properties had been determined experimentally. The aging of the materials (variation of their properties during half a year was documented as well. A design procedure proposed by Kulik et al. (2008 was applied to get an optimal value for the coating thickness. Along with the drag measurement using the strain balance, velocity and pressure were measured for different coatings. The compliant coatings with the thickness h = 7mm achieved 4∼5% drag reduction within a velocity range 30∼40 m/s. The drag reduction mechanism of the attenuation of turbulence velocity fluctuations due to the compliant coating was demonstrated. It is envisioned that larger drag reduction effect is obtainable at higher flow velocities for high speed trains and subsonic aircrafts.

  20. Superhydrophobic copper tubes with possible flow enhancement and drag reduction

    OpenAIRE

    Shirtcliffe, NJ; McHale, G; Newton, MI; Zhang, Y.

    2009-01-01

    The transport of a Newtonian liquid through a smooth pipe or tube is dominated by the frictional drag on the liquid against the walls. The resistance to flow against a solid can, however, be reduced by introducing a layer of gas at or near the boundary between the solid and liquid. This can occur by the vaporization of liquid at a surface at a temperature above the Leidenfrost point, by a cushion of air (e.g. below a hovercraft), or by producing bubbles at the interface. These methods require...

  1. Drag and heat flux reduction mechanism of blunted cone with aerodisks

    Science.gov (United States)

    Huang, Wei; Li, Lang-quan; Yan, Li; Zhang, Tian-tian

    2017-09-01

    The major challenge among a number of design requirements for hypersonic vehicles is the reduction of drag and aerodynamic heating. Of all these techniques of drag and heat flux reduction, application of forward facing aerospike conceived in 1950s is an effective and simpler technique to reduce the drag as well as the heat transfer rate for blunt nosed bodies at hypersonic Mach numbers. In this paper, the flow fields around a blunt cone with and without aerodisk flying at hypersonic Mach numbers are computed numerically, and the numerical simulations are conducted by specifying the freestream velocity, static pressure and static temperatures at the inlet of the computational domain with a three-dimensional, steady, Reynolds-averaged Navier-Stokes equation. An aerodisk is attached to the tip of the rod to reduce the drag and heat flux further. The influences of the length of rod and the diameter of aerodisk on the drag and heat flux reduction mechanism are analyzed comprehensively, and eight configurations are taken into consideration in the current study. The obtained results show that for all aerodisks, the reduction in drag of the blunt body is proportional to the extent of the recirculation dead air region. For long rods, the aerodisk is found not that beneficial in reducing the drag, and an aerodisk is more effective than an aerospike. The spike produces a region of recirculation separated flow that shields the blunt-nosed body from the incoming flow, and the recirculation region is formed around the root of the spike up to the reattachment point of the flow at the shoulder of the blunt body. The dynamic pressure in the recirculation area is highly reduced and thus leads to the decrease in drag and heat load on the surface of the blunt body. Because of the reattachment of the shear layer on the shoulder of the blunt body, the pressure near that point becomes large.

  2. Numerical simulation for the influence of injected laser power on plasma drag reduction

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Z; Fang, J [Department of Postgraduates, Academy of Equipment Command and Technology, 3380 Post box, Huairou Beijing 101416 (China); Dou, Z G; Huang, H, E-mail: liuzhun0@gmail.com [Department of Basic Theories, Academy of Equipment Command and Technology, 3380 Post box, Huairou Beijing 101416 (China)

    2011-02-01

    Laser plasma drag reduction is a new method to reduce the wave drag of hypersonic flight. Inject laser power is an important parameter. An appropriate laser power should be chosen when laser power was injected to achieve the best drag reduction effect via the minimum laser power. The effect of inject laser power on the performance of laser plasma drag reduction when incoming flight Mach number is 6.5 and at 30km altitude was simulated numerically. The result indicates that the drag can be effectively reduced by energy injection in the upstream flow. The larger the inject power is, the smaller the drag of the blunt body obtained. The energy injection can also influence the pressure and temperature on the surface of blunt body. When laser energy injected, high pressure region on the surface moves to the back of the hemisphere, the pressure of stagnation point decreased. There are two peaks of temperature on the blunt surface, one is the stagnation point and the other is the high pressure region. Temperature of the surface after high pressure region is lower comparison to the condition that no energy injected.

  3. Buoyancy increase and drag-reduction through a simple superhydrophobic coating.

    Science.gov (United States)

    Hwang, Gi Byoung; Patir, Adnan; Page, Kristopher; Lu, Yao; Allan, Elaine; Parkin, Ivan P

    2017-06-08

    A superhydrophobic paint was fabricated using 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES), TiO 2 nanoparticles and ethanol. The paint has potential for aquatic application of a superhydrophobic coating as it induces increased buoyancy and drag reduction. Buoyance testing showed that the reduction of surface energy by superhydrophobic coating made it feasible that glass, a high density material, was supported by the surface tension of water. In a miniature boat sailing test, it was shown that the low energy surface treatment decreased the adhesion of water molecules to the surface of the boat resulting in a reduction of the drag force. Additionally, a robust superhydrophobic surface was fabricated through layer-by-layer coating using adhesive double side tape and the paint, and after a 100 cm abrasion test with sand paper, the surface still retained its water repellency, enhanced buoyancy and drag reduction.

  4. Drag reductions and the air-water interface stability of superhydrophobic surfaces in rectangular channel flow

    Science.gov (United States)

    Zhang, Jingxian; Yao, Zhaohui; Hao, Pengfei

    2016-11-01

    Flow in a rectangular channel with superhydrophobic (SH) top and bottom walls was investigated experimentally. Different SH surfaces, including hierarchical structured surfaces and surfaces with different micropost sizes (width and spacing) but the same solid fraction, were fabricated and measured. Pressure loss and flow rate in the channel with SH top and bottom walls were measured, with Reynolds number changing from 700 to 4700, and the corresponding friction factor for the SH surface was calculated. The statuses of the air plastron on different SH surfaces were observed during the experiment. In our experiment, compared with the experiment for the smooth surface, drag reductions were observed for all SH surfaces, with the largest drag reduction of 42.2%. It was found that the hierarchy of the microstructure can increase the drag reduction by decreasing the solid fraction and enhancing the stability of the air-water interface. With a fixed solid fraction, the drag reduction decreases as the post size (width and spacing) increases, due to the increasing curvature and instability effects of the air-water interface. A correlation parameter between the contact angle hysteresis, the air-water interface stability, and the drag reduction of the SH surfaces was found.

  5. Drag Reduction of an Airfoil Using Deep Learning

    Science.gov (United States)

    Jiang, Chiyu; Sun, Anzhu; Marcus, Philip

    2017-11-01

    We reduced the drag of a 2D airfoil by starting with a NACA-0012 airfoil and used deep learning methods. We created a database which consists of simulations of 2D external flow over randomly generated shapes. We then developed a machine learning framework for external flow field inference given input shapes. Past work which utilized machine learning in Computational Fluid Dynamics focused on estimations of specific flow parameters, but this work is novel in the inference of entire flow fields. We further showed that learned flow patterns are transferable to cases that share certain similarities. This study illustrates the prospects of deeper integration of data-based modeling into current CFD simulation frameworks for faster flow inference and more accurate flow modeling.

  6. Drag Reduction of a Pipe Flow Using Nata de Coco Suspensions

    Directory of Open Access Journals (Sweden)

    Satoshi Ogata

    2014-08-01

    Full Text Available The addition of drag-reducing agents to reduce pipe friction loss has attracted attention as a method to conserve energy. In addition to reducing drag, these agents are required to have a low environmental load and conserve natural resources. Therefore, naturally occurring biopolymer additives, which are considered to have a low environmental load, have recently received much attention. Here we focused on nata de coco, a type of biopolymer that exhibits low mechanical degradation, and found that it reduced drag by up to 25% at a concentration of 50 ppm. With respect to the drag reduction (DR mechanism, we investigated the relation between DR phenomena and the fiber structure of nata de coco by visualization. As a result, we found that the DR effect appeared only when a network of nata de coco fibers was formed in the suspension. In addition, DR increased as the size of the network of nata de coco fibers increased.

  7. Numerical study of linear feedback control for form-drag reduction

    Science.gov (United States)

    Dahan, Jeremy; Morgans, Aimee

    2012-11-01

    The present work is a numerical investigation of linear system identification and model-based feedback control methods for form-drag reduction. Large-Eddy Simulation (LES) is used to represent the flow over a simple bluff body with a sharp trailing edge, with a turbulent separation. For actuation, two types of perturbations are considered: a model of zero-net-mass-flux slot jets and momentum sources. Pressure measurements distributed over the base of the body provide the sensor information. The first part of the study will focus on the open-loop characterization of the flow. The base pressure field will be studied in relation to the wake dynamics. The effect of key actuation and flow parameters, such as actuation type, actuation location and Reynolds number, will be investigated. A black-box model of the flow response, obtained via system identification, will be examined. The second part will look at the design of robust controllers. It will be shown that uncertainties in the model and inflow conditions can be partially mitigated by the robustness of the controller. The behaviour of the feedback-controlled flow will be compared with the results achievable using open-loop forcing to draw conclusions about the success of the flow response model and the controller synthesis. PhD student in Department of Aeronautics.

  8. Large-scale control strategy for drag reduction in turbulent channel flows

    Science.gov (United States)

    Yao, Jie; Chen, Xi; Thomas, Flint; Hussain, Fazle

    2017-06-01

    In a recent article, Canton et al. [J. Canton et al., Phys. Rev. Fluids 1, 081501(R) (2016), 10.1103/PhysRevFluids.1.081501] reported significant drag reduction in turbulent channel flow by using large-scale, near-wall streamwise swirls following the control strategy of Schoppa and Hussain [W. Schoppa and F. Hussain, Phys. Fluids 10, 1049 (1998), 10.1063/1.869789] for low Reynolds numbers only, but found no drag reduction at high friction Reynolds numbers (Reτ=550 ). Here we show that the lack of drag reduction at high Re observed by Canton et al. is remedied by the proper choice of the large-scale control flow. In this study, we apply near-wall opposed wall-jet forcing to achieve drag reduction at the same (high) Reynolds number where Canton et al. found no drag reduction. The steady excitation is characterized by three control parameters, namely, the wall-jet-forcing amplitude A+, the spanwise spacing Λ+, and the wall jet height yc+ (+ indicates viscous scaling); the primary difference between Schoppa and Hussain's work (also that of Canton et al.) and this Rapid Communication is the emphasis on the explicit choice of yc+ here. We show as an example that with a choice of A+≈0.015 ,Λ+≈1200 , and yc+≈30 the flow control definitely suppresses the wall shear stress at a series of Reynolds numbers, namely, 19 %,14 % , and 12 % drag reductions at Reτ=180 , 395, and 550, respectively. Further study should explore optimization of these parameter values.

  9. Turbulent Flow Enhancement by Polyelectrolyte Additives: Mechanistic Implications for Drag Reduction.

    Science.gov (United States)

    Wagger, David Leonard

    1992-01-01

    The drag reduction phenomenon was experimentally studied in two pipes, of diameters 1.46 and 1.02 cm, using seven polyelectrolytic HPAM additives, with molecular weights from 1 to 20 times 10^6 g/mole and degree of backbone hydrolysis from 8 to 60%, at concentrations from 1 to 1000 wppm, in saline solutions containing from 0.3 to 0.00001 N NaCl. Both laminar and turbulent flow behavior were greatly influenced by salinity-induced changes in the initial conformation of the HPAM additives. Initially collapsed, random-coiling conformations exhibited Newtonian laminar flow and Type-A turbulent drag reduction, while initially extended conformations exhibited shear-thinning in laminar flow and Type-B turbulent drag reduction. The gross-flow physics of Type-B drag reduction were delineated. A characteristic "ladder" structure prevailed, with polymeric regime segments that were roughly parallel to, but shifted upward from, the Prandtl-Karman line. In the polymeric regime, both Type-A fan and Type -B ladder structures were essentially independent of pipe diameter, and were scaled by the wall shear stress. The wall shear stress also scaled degradation during drag reduction. New onset and slope increment correlations were presented for Type-A drag reduction by HPAM additives. In Type-B drag reduction, flow enhancement was found proportional to additive concentration, and the intrinsic slip, Sigma = S^'/(c/M _{rm w}), varied roughly as the third power of backbone chain links N_ {rm bb}. New intrinsic slip and retro-onset correlations were presented for Type-B drag reduction by HPAM additives. Analysis of Type-B literature revealed a wide range of additive efficacies, with specific slips S^'/c from 0.0001 to 4. For the most effective additives, HPAM and asbestos fibers, the additive-pervaded volume fraction per unit flow enhancement, X_{rm v} /S^' ~ 3000, implied that these additives align during drag reduction. The slip ratio R_{rm sc}, which is the relative flow enhancement

  10. Superhydrophobic copper tubes with possible flow enhancement and drag reduction.

    Science.gov (United States)

    Shirtcliffe, Neil J; McHale, Glen; Newton, Michael I; Zhang, Yong

    2009-06-01

    The transport of a Newtonian liquid through a smooth pipe or tube is dominated by the frictional drag on the liquid against the walls. The resistance to flow against a solid can, however, be reduced by introducing a layer of gas at or near the boundary between the solid and liquid. This can occur by the vaporization of liquid at a surface at a temperature above the Leidenfrost point, by a cushion of air (e.g. below a hovercraft), or by producing bubbles at the interface. These methods require a continuous energy input, but a more recent discovery is the possibility of using a superhydrophobic surface. Most reported research uses small sections of lithographically patterned surfaces and rarely considers pressure differences or varying flow rates. In this work we present a method for creating a uniform superhydrophobic nanoribbon layer on the inside of round copper tubes of millimetric internal radius. Two types of experiments are described, with the first involving a simultaneous comparison of four tubes with different surface finishes (as received, as received with hydrophobic coating, nanoribbon, and nanoribbon with a hydrophobic coating) under constant flow rate conditions using water and water-glycerol mixtures. The results show that the superhydrophobic nanoribbon with a hydrophobic coating surface finish allows greater flow at low pressure differences but that the effect disappears as the pressure at the inlet of the tube is increased. The second experiment is a simple visual demonstration of the low-pressure behavior using two nominally identical tubes in terms of length and cross-section, but with one tube possessing a superhydrophobic internal surface finish. In this experiment a reservoir is allowed to feed the two tubes with open ends via a T-piece and it is observed that, once flow commences, it preferentially occurs down the superhydrophobic tube.

  11. Heavy Class Helicopter Fuselage Model Drag Reduction by Active Flow Control Systems

    Science.gov (United States)

    De Gregorio, F.

    2017-08-01

    A comprehensive experimental investigation of helicopter blunt fuselage drag reduction using active flow control is being carried out within the European Clean Sky program. The objective is to demonstrate the capability of several active flow technologies to decrease fuselage drag by alleviating the flow separation occurring in the rear area of some helicopters. The work is performed on a simplified blunt fuselage at model-scale. Two different flow control actuators are considered for evaluation: steady blowing, unsteady blowing (or pulsed jets). Laboratory tests of each individual actuator are first performed to assess their performance and properties. The fuselage model is then equipped with these actuators distributed in 3 slots located on the ramp bottom edge. This paper addresses the promising results obtained during the wind-tunnel campaign, since significant drag reductions are achieved for a wide range of fuselage angles of attack and yaw angles without detriment of the other aerodynamic characteristics.

  12. Drag &Drop, Multiphysics & Neural Net-based Lab-on-Chip Optimization Software Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall objective of this project is to develop a drag and drop, component library (fluidic lego) based, system simulation and optimization software for entire...

  13. The importance of bubble deformability for strong drag reduction in bubbly turbulent Taylor-Couette flow

    NARCIS (Netherlands)

    van Gils, Dennis Paulus Maria; Narezo Guzman, Daniela; Sun, Chao; Lohse, Detlef

    2013-01-01

    Bubbly turbulent Taylor–Couette (TC) flow is globally and locally studied at Reynolds numbers of Re=5×105 to 2×106 with a stationary outer cylinder and a mean bubble diameter around 1 mm. We measure the drag reduction (DR) based on the global dimensional torque as a function of the global gas volume

  14. Drag reduction by the introduction of shear-free surfaces in a ...

    Indian Academy of Sciences (India)

    In this paper, a novel technique for drag reduction in turbulent flows is presented. The technique involves the modification of the large scales of turbulent flows and is a passive approach. The lateral transport of momentum, which is a dominant mechanism in turbulence, is attenuated by the introduction of moving shearfree ...

  15. A New Paradigm for Turbulence Control for Drag Reduction

    Science.gov (United States)

    2017-02-27

    Hussein∗ and Sedat Biringen† Department of Aerospace Engineering Sciences , University of Colorado Boulder, Boulder, Colorado 80309, USA Abstract Direct ...AVAILABILITY STATEMENT 13. SUPPLEMENTARY NOTES 14. ABSTRACT Direct numerical simulations (DNS) of spanwise-rotating turbulent channel flow as well as the...turbulent channel flow using direct numerical simulation (DNS) was also conducted. The reduction of the kinetic energy of large amplitude perturbations

  16. Investigation of Tractor Base Bleeding for Heavy Vehicle Aerodynamic Drag Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, J; Salari, K; Storms, B

    2007-10-25

    One of the main contributors to the aerodynamic drag of a heavy vehicle is tractor-trailer gap drag, which arises when the vehicle operates within a crosswind. Under this operating condition, freestream flow is entrained into the tractor-trailer gap, imparting a momentum exchange to the vehicle and subsequently increasing the aerodynamic drag. While a number of add-on devices, including side extenders, splitter plates, vortex stabilizers, and gap sealers, have been previously tested to alleviate this source of drag, side extenders remain the primary add-on device of choice for reducing tractor-trailer gap drag. However, side extenders are not without maintenance and operational issues. When a heavy vehicle pivots sharply with respect to the trailer, as can occur during loading or unloading operations, the side extenders can become crushed against the trailer. Consequently, fleet operators are forced to incur additional costs to cover the repair or replacement of the damaged side extenders. This issue can be overcome by either shortening the side extenders or by devising an alternative drag reduction concept that can perform just as effectively as side extenders. To explore such a concept, we investigate tractor base bleeding as a means of reducing gap drag. Wind tunnel measurements are made on a 1:20 scale heavy vehicle model at a vehicle width-based Reynolds number of 420,000. The tractor bleeding flow, which is delivered through a porous material embedded within the tractor base, is introduced into the tractor-trailer gap at bleeding coefficients ranging from 0.0-0.018. To determine the performance of tractor base bleeding under more realistic operating conditions, computational fluid dynamics simulations are performed on a full-scale heavy vehicle within a crosswind for bleeding coefficients ranging from 0.0-0.13.

  17. Underwater restoration and retention of gases on superhydrophobic surfaces for drag reduction

    OpenAIRE

    Lee, C.; Kim, CJ

    2011-01-01

    Superhydrophobic (SHPo) surfaces have shown promise for passive drag reduction because their surface structures can hold a lubricating gas film between the solid surface and the liquid in contact with it. However, the types of SHPo surfaces that would produce any meaningful amount of reduction get wet under liquid pressure or at surface defects, both of which are unavoidable in the real world. In this Letter, we solve the above problem by (1) discovering surface structures that allow the rest...

  18. Optimally amplified large-scale streaks and drag reduction in turbulent pipe flow

    Science.gov (United States)

    Willis, Ashley P.; Hwang, Yongyun; Cossu, Carlo

    2010-09-01

    The optimal amplifications of small coherent perturbations within turbulent pipe flow are computed for Reynolds numbers up to one million. Three standard frameworks are considered: the optimal growth of an initial condition, the response to harmonic forcing and the Karhunen-Loève (proper orthogonal decomposition) analysis of the response to stochastic forcing. Similar to analyses of the turbulent plane channel flow and boundary layer, it is found that streaks elongated in the streamwise direction can be greatly amplified from quasistreamwise vortices, despite linear stability of the mean flow profile. The most responsive perturbations are streamwise uniform and, for sufficiently large Reynolds number, the most responsive azimuthal mode is of wave number m=1 . The response of this mode increases with the Reynolds number. A secondary peak, where m corresponds to azimuthal wavelengths λθ+≈70-90 in wall units, also exists in the amplification of initial conditions and in premultiplied response curves for the forced problems. Direct numerical simulations at Re=5300 confirm that the forcing of m=1,2 and m=4 optimal structures results in the large response of coherent large-scale streaks. For moderate amplitudes of the forcing, low-speed streaks become narrower and more energetic, whereas high-speed streaks become more spread. It is further shown that drag reduction can be achieved by forcing steady large-scale structures, as anticipated from earlier investigations. Here the energy balance is calculated. At Re=5300 it is shown that, due to the small power required by the forcing of optimal structures, a net power saving of the order of 10% can be achieved following this approach, which could be relevant for practical applications.

  19. Underwater Restoration and Retention of Gases on Superhydrophobic Surfaces for Drag Reduction

    Science.gov (United States)

    Lee, Choongyeop; Kim, Chang-Jin

    2011-01-01

    Superhydrophobic (SHPo) surfaces have shown promise for passive drag reduction because their surface structures can hold a lubricating gas film between the solid surface and the liquid in contact with it. However, the types of SHPo surfaces that would produce any meaningful amount of reduction get wet under liquid pressure or at surface defects, both of which are unavoidable in the real world. In this Letter, we solve the above problem by (1) discovering surface structures that allow the restoration of a gas blanket from a wetted state while fully immersed underwater and (2) devising a self-controlled gas-generation mechanism that maintains the SHPo condition under high liquid pressures (tested up to 7 atm) as well as in the presence of surface defects, thus removing a fundamental barrier against the implementation of SHPo surfaces for drag reduction.

  20. Drag reduction in reservoir rock surface: Hydrophobic modification by SiO{sub 2} nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Yong-Li, E-mail: yylhill@163.com [College of Chemistry & Chemical Engineering, Xi’an Shiyou University, Xi’an 710065 (China); Cui, Ming-Yue; Jiang, Wei-Dong; He, An-Le; Liang, Chong [Langfang Branch of Research Institute of Petroleum Exploration & Development, Langfang 065007 (China)

    2017-02-28

    Graphical abstract: The micro-nanoscale hierarchical structures at the sandstone core surface are constructed by adsorption of the modified silica nanoparticles, which leads to the effect of drag reduction to improve the low injection rate in ultra-low permeability reservoirs. - Highlights: • A micro-nanoscale hierarchical structure is formed at the reservoir rock surface. • An inversion has happened from hydrophilic into hydrophobic modified by nanofluids. • The effect of drag reduction to improve the low injection rate is realized. • The mechanism of drag reduction induced from the modified core surface was unclosed. - Abstract: Based on the adsorption behavior of modified silica nanoparticles in the sandstone core surface, the hydrophobic surface was constructed, which consists of micro-nanoscale hierarchical structure. This modified core surface presents a property of drag reduction and meets the challenge of high injection pressure and low injection rate in low or ultra-low permeability reservoir. The modification effects on the surface of silica nanoparticles and reservoir cores, mainly concerning hydrophobicity and fine structure, were determined by measurements of contact angle and scanning electron microscopy. Experimental results indicate that after successful modification, the contact angle of silica nanoparticles varies from 19.5° to 141.7°, exhibiting remarkable hydrophobic properties. These modified hydrophobic silica nanoparticles display a good adsorption behavior at the core surface to form micro-nanobinary structure. As for the wettability of these modified core surfaces, a reversal has happened from hydrophilic into hydrophobic and its contact angle increases from 59.1° to 105.9°. The core displacement experiments show that the relative permeability for water has significantly increased by an average of 40.3% via core surface modification, with the effects of reducing injection pressure and improving injection performance of water

  1. Drag reduction and the dynamics of turbulence in simple and complex fluidsa)

    Science.gov (United States)

    Graham, Michael D.

    2014-10-01

    Addition of a small amount of very large polymer molecules or micelle-forming surfactants to a liquid can dramatically reduce the energy dissipation it exhibits in the turbulent flow regime. This rheological drag reduction phenomenon is widely used, for example, in the Alaska pipeline, but it is not well-understood, and no comparable technology exists to reduce turbulent energy consumption in flows of gases, in which polymers or surfactants cannot be dissolved. The most striking feature of this phenomenon is the existence of a so-called maximum drag reduction (MDR) asymptote: for a given geometry and driving force, there is a maximum level of drag reduction that can be achieved through addition of polymers. Changing the concentration, molecular weight or even the chemical structure of the additives has little to no effect on this asymptotic value. This universality is the major puzzle of drag reduction. We describe direct numerical simulations of turbulent minimal channel flow of Newtonian fluids and viscoelastic polymer solutions. Even in the absence of polymers, we show that there are intervals of "hibernating" turbulence that display very low drag as well as many other features of the MDR asymptote observed in polymer solutions. As Weissenberg number increases to moderate values the frequency of these intervals also increases, and a simple theory captures key features of the intermittent dynamics observed in the simulations. At higher Weissenberg number, these intervals are altered - for example, their duration becomes substantially longer and the instantaneous Reynolds shear stress during them becomes very small. Additionally, simulations of "edge states," dynamical trajectories that lie on the boundary between turbulent and laminar flow, display characteristics that are similar to those of hibernating turbulence and thus to the MDR asymptote, again even in the absence of polymer additives. Based on these observations, we propose a tentative unified description

  2. Drag reduction via micro bubble injection in boundary layer of channel flows

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Y.A. [Texas A and M Univ., Dept. of Nuclear Engineering, College Station, Texas (United States)

    2004-07-01

    Full text of publication follows:Methods to reduce the drag in turbulent flows have been carried out for the past several decades. Reducing skin friction has obvious advantages through improvements in fuel economy, range (as in case of commercial ships and aircraft) or in peak speed (desirable in military or racing applications) and for less impact on the environment due to less fuel consumption. Recently, the reduction of turbulent friction between a solid surface and fluid by adding drag reducing additives has received increasing attention for saving power and reducing the pollution. Polymers and surfactants injections, wall oscillations, traveling waves, blowing and suction, and micro-bubble injection are examples among active additives. Riblets are an example of passive techniques to achieve drag reduction. However, a consensus about understanding the mechanism that governs this phenomenon has not been reached. In this paper, an investigation of turbulent structure modification of fully developed channel flow by micro-bubble injection close to the upper wall was studied. Two-dimensional velocity components at Reynolds number of 5128 based on the half height of the channel and bulk velocity were measured. The particle image velocimetry technique was utilized to obtain the two-dimensional velocity fields of the fluid and the micro-bubbles. Micro-bubbles with an average diameter of 30 {mu}m were injected into the buffer layer. Various values of void fractions were used to evaluate the effects of micro-bubbles concentration on the drag reduction. Modifications in the length and time scales were detected by calculating two-point correlation coefficients. Streamline length and time scales were increased. On the contrary, the normal length and time scales were decreased with the increase of the drag reduction. The presence of the micro-bubbles with low local concentration of 4% achieved 40% drag reduction. A decrease in the Reynolds stresses were achieved as the void

  3. Biomimetic structures for fluid drag reduction in laminar and turbulent flows

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Yong Chae; Bhushan, Bharat, E-mail: Bhushan.2@osu.ed [Nanoprobe Laboratory for Bio- and Nanotechnology and Biomimetics (NLB2), Ohio State University, 201 West 19th Avenue, Columbus, OH 43210-1142 (United States)

    2010-01-27

    Biomimetics allows one to mimic nature to develop materials and devices of commercial interest for engineers. Drag reduction in fluid flow is one of the examples found in nature. In this study, nano, micro, and hierarchical structures found in lotus plant surfaces, as well as shark skin replica and a rib patterned surface to simulate shark skin structure were fabricated. Drag reduction efficiency studies on the surfaces were systematically carried out using water flow. An experimental flow channel was used to measure the pressure drop in laminar and turbulent flows, and the trends were explained in terms of the measured and predicted values by using fluid dynamics models. The slip length for various surfaces in laminar flow was also investigated based on the measured pressure drop. For comparison, the pressure drop for various surfaces was also measured using air flow.

  4. Drag reduction effects facilitated by microridges inside the mouthparts of honeybee workers and drones.

    Science.gov (United States)

    Li, Chu-Chu; Wu, Jia-Ning; Yang, Yun-Qiang; Zhu, Ren-Gao; Yan, Shao-Ze

    2016-01-21

    The mouthpart of a honeybee is a natural well-designed micropump that uses a reciprocating glossa through a temporary tube comprising a pair of galeae and labial palpi for loading nectar. The shapes and sizes of mouthparts differ among castes of honeybees, but the diversities of the functional microstructures inside the mouthparts of honeybee workers and drones remain poorly understood. Through scanning electron microscopy, we found the dimensional difference of uniformly distributed microridges on the inner galeae walls of Apis mellifera ligustica workers and drones. Subsequently, we recorded the feeding process of live honeybees by using a specially designed high-speed camera system. Considering the microridges and kinematics of the glossa, we constructed a hydrodynamic model to calculate the friction coefficient of the mouthpart. In addition, we test the drag reduction through the dimensional variations of the microridges on the inner walls of mouthparts. Theoretical estimations of the friction coefficient with respect to dipping frequency show that inner microridges can reduce friction during the feeding process of honeybees. The effects of drag reduction regulated by specific microridges were then compared. The friction coefficients of the workers and drones were found to be 0.011±0.007 (mean±s.d.) and 0.045±0.010, respectively. These results indicate that the mouthparts of workers are more capable of drag reduction compared with those of drones. The difference was analyzed by comparing the foraging behavior of the workers and drones. Workers are equipped with well-developed hypopharyngeal, and their dipping frequency is higher than that of drones. Our research establishes a critical link between microridge dimensions and drag reduction capability during the nectar feeding of honeybees. Our results reveal that microridges inside the mouthparts of honeybee workers and drones reflect the caste-related life cycles of honeybees. Copyright © 2015 Elsevier Ltd

  5. Influence Study of the Viscoelastic Fluids Features in Drag Reduction in Laminar Regime Flow in Pipeline

    OpenAIRE

    Vilalta Guillermo; Silva Mário; Blanco Alejandro

    2016-01-01

    The drag reduction by polymer addition is wide interest in several areas. It has been shown that the polymer addition cushions the dissipative effects in turbulent flows. The main objective of this work is to establish a methodology for the numerical simulation of viscoelastic fluid through internal subroutines implemented in the Fluent code, via UDF. The validation of this methodology is made for the laminar flow regime case in pipeline. To describe the viscoelastic effect, it was used the F...

  6. Riblet drag reduction and the effect of bulk fluid rotation in a fully turbulent Taylor-Couette flow

    NARCIS (Netherlands)

    Greidanus, A.J.; Delfos, R.; Tokgoez, S.; Westerweel, J.

    2015-01-01

    Low drag surfaces are often desired in many industries with applications in open and closed channel flows, such as ship hulls and pipe flows. Drag reduction is a phenomenon that can have substantial energy savings, resulting in ecological and economical benefits. We use a Taylor-Couette facility as

  7. Drag Reduction and Performance Improvement of Hydraulic Torque Converters with Multiple Biological Characteristics

    Science.gov (United States)

    Chunbao, Liu; Changsuo, Liu; Yubo, Zhang

    2016-01-01

    Fish-like, dolphin-like, and bionic nonsmooth surfaces were employed in a hydraulic torque converter to achieve drag reduction and performance improvement, which were aimed at reducing profile loss, impacting loss and friction loss, respectively. YJSW335, a twin turbine torque converter, was bionically designed delicately. The biological characteristics consisted of fish-like blades in all four wheels, dolphin-like structure in the first turbine and the stator, and nonsmooth surfaces in the pump. The prediction performance of bionic YJSW335, obtained by computational fluid dynamics simulation, was improved compared with that of the original model, and then it could be proved that drag reduction had been achieved. The mechanism accounting for drag reduction of three factors was also investigated. After bionic design, the torque ratio and the highest efficiencies of YJSW335 were both advanced, which were very difficult to achieve through traditional design method. Moreover, the highest efficiency of the low speed area and high speed area is 85.65% and 86.32%, respectively. By economic matching analysis of the original and bionic powertrains, the latter can significantly reduce the fuel consumption and improve the operating economy of the loader. PMID:27752220

  8. Air-Induced Drag Reduction at High Reynolds Numbers: Velocity and Void Fraction Profiles

    Science.gov (United States)

    Elbing, Brian; Mäkiharju, Simo; Wiggins, Andrew; Dowling, David; Perlin, Marc; Ceccio, Steven

    2010-11-01

    The injection of air into a turbulent boundary layer forming over a flat plate can reduce the skin friction. With sufficient volumetric fluxes an air layer can separate the solid surface from the flowing liquid, which can produce drag reduction in excess of 80%. Several large scale experiments have been conducted at the US Navy's Large Cavitation Channel on a 12.9 m long flat plate model investigating bubble drag reduction (BDR), air layer drag reduction (ALDR) and the transition between BDR and ALDR. The most recent experiment acquired phase velocities and void fraction profiles at three downstream locations (3.6, 5.9 and 10.6 m downstream from the model leading edge) for a single flow speed (˜6.4 m/s). The profiles were acquired with a combination of electrode point probes, time-of-flight sensors, Pitot tubes and an LDV system. Additional diagnostics included skin-friction sensors and flow-field image visualization. During this experiment the inlet flow was perturbed with vortex generators immediately upstream of the injection location to assess the robustness of the air layer. From these, and prior measurements, computational models can be refined to help assess the viability of ALDR for full-scale ship applications.

  9. Drag Reduction and Performance Improvement of Hydraulic Torque Converters with Multiple Biological Characteristics

    Directory of Open Access Journals (Sweden)

    Liu Chunbao

    2016-01-01

    Full Text Available Fish-like, dolphin-like, and bionic nonsmooth surfaces were employed in a hydraulic torque converter to achieve drag reduction and performance improvement, which were aimed at reducing profile loss, impacting loss and friction loss, respectively. YJSW335, a twin turbine torque converter, was bionically designed delicately. The biological characteristics consisted of fish-like blades in all four wheels, dolphin-like structure in the first turbine and the stator, and nonsmooth surfaces in the pump. The prediction performance of bionic YJSW335, obtained by computational fluid dynamics simulation, was improved compared with that of the original model, and then it could be proved that drag reduction had been achieved. The mechanism accounting for drag reduction of three factors was also investigated. After bionic design, the torque ratio and the highest efficiencies of YJSW335 were both advanced, which were very difficult to achieve through traditional design method. Moreover, the highest efficiency of the low speed area and high speed area is 85.65% and 86.32%, respectively. By economic matching analysis of the original and bionic powertrains, the latter can significantly reduce the fuel consumption and improve the operating economy of the loader.

  10. Drag Reduction and Performance Improvement of Hydraulic Torque Converters with Multiple Biological Characteristics.

    Science.gov (United States)

    Chunbao, Liu; Li, Li; Yulong, Lei; Changsuo, Liu; Yubo, Zhang

    2016-01-01

    Fish-like, dolphin-like, and bionic nonsmooth surfaces were employed in a hydraulic torque converter to achieve drag reduction and performance improvement, which were aimed at reducing profile loss, impacting loss and friction loss, respectively. YJSW335, a twin turbine torque converter, was bionically designed delicately. The biological characteristics consisted of fish-like blades in all four wheels, dolphin-like structure in the first turbine and the stator, and nonsmooth surfaces in the pump. The prediction performance of bionic YJSW335, obtained by computational fluid dynamics simulation, was improved compared with that of the original model, and then it could be proved that drag reduction had been achieved. The mechanism accounting for drag reduction of three factors was also investigated. After bionic design, the torque ratio and the highest efficiencies of YJSW335 were both advanced, which were very difficult to achieve through traditional design method. Moreover, the highest efficiency of the low speed area and high speed area is 85.65% and 86.32%, respectively. By economic matching analysis of the original and bionic powertrains, the latter can significantly reduce the fuel consumption and improve the operating economy of the loader.

  11. Near-hydrophobic-surface flow measurement by micro-3D PTV for evaluation of drag reduction

    Science.gov (United States)

    Ichikawa, Y.; Yamamoto, K.; Yamamoto, M.; Motosuke, M.

    2017-09-01

    This study reports the estimation of drag reduction effect, which is obtained from slip flow measurement in hydrophobic microchannels by direct measurement of near-wall velocity distribution. To reveal laminar drag reduction effect of hydrophobic surfaces, it is necessary to investigate near-microstructured-surface flow. In this study, we employed a hydrophobic surface, which has longitudinal microribs and microgrooves oriented parallel to the water flow direction in a microchannel, and measured a near-microstructured-surface flow by astigmatism particle tracking velocimetry (APTV) that enables to obtain the three-dimensional and three-component velocity profile. From the flow measurement results, the curvature and profile of liquid-gas interfaces formed at the microgrooves were obtained. Additionally, since the APTV has the ability to measure the three-dimensional velocity distribution near interfaces, it is possible to determine the shear stress on the interfaces if the interface position is known. Moreover, the procedure about a numerical simulation, which used the experimental results as a boundary condition was examined, and its verification in terms of the drag reduction effect estimation was conducted by comparing with experimental results.

  12. Effect of Off-Body Laser Discharge on Drag Reduction of Hemisphere Cylinder in Supersonic Flow

    Science.gov (United States)

    Kianvashrad, Nadia; Knight, Doyle; Wilkinson, Stephen P.; Chou, Amanda; Horne, Robert A.; Herring, Gregory C.; Beeler, George B.; Jangda, Moazzam

    2017-01-01

    The interaction of an off-body laser discharge with a hemisphere cylinder in supersonic flow is investigated. The objectives are 1) experimental determination of the drag reduction and energetic efficiency of the laser discharge, and 2) assessment of the capability for accurate simulation of the interaction. The combined computational and experimental study comprises two phases. In the first phase, laser discharge in quiescent air was examined. The temporal behavior of the shock wave formed by the laser discharge was compared between experiment and simulation and good agreement is observed. In the second phase, the interaction of the laser discharge with a hemisphere cylinder was investigated numerically. Details of the pressure drag reduction and the physics of the interaction of the heated region with the bow shock are included. The drag reduction due to this interaction persisted for about five characteristic times where one characteristic time represents the time for the flow to move a distance equal to the hemisphere radius. The energetic efficiency of laser discharge for the case with 50 mJ energy absorbed by the gas is calculated as 3.22.

  13. Bubble deformability is crucial for strong drag reduction in turbulent Taylor-Couette flow

    Science.gov (United States)

    Sun, Chao; Narezo Guzman, Daniela; van Gils, Dennis P. M.; Lohse, Detlef

    2011-11-01

    Bubbly Taylor-Couette flow in the turbulent regime is studied both globally and locally at Reynolds numbers of 5 . 1 ×105 - 2 . 0 ×106 for pure inner cylinder rotation. We measure the drag reduction (DR) based on the global torque for global gas volume fractions (αglobal) up to 4 %, and observe a moderate DR for Re = 5 . 1 ×105 , and a strong DR for Re = 1 . 0 ×106 and 2 . 0 ×106 . Remarkably, more than 40 % of DR is achieved for αglobal = 4 % at Re = 2 . 0 ×106 . We investigate the statistics of the liquid flow velocity, and directly measure the local bubble concentration and Weber number for two Reynolds numbers in different drag reduction regimes, i.e. Re = 1 . 0 ×106 (strong DR) and 5 . 1 ×105 (moderate DR). By combining global and local measurements we reveal that bubble deformability is crucial for strong drag reduction in bubbly turbulent Taylor-Couette flow. This work was financially supported by technology foundation STW in The Netherlands.

  14. Study on drag reduction of turbulent boundary layer over semi-circular riblets using PIV measurement

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.J.; Lee, S.H. [Pohang Institute of Science and Technology, Pohang (Korea)

    1999-04-01

    The near-wall flow structures of turbulent boundary layer over riblets having semi-circular grooves were investigated experimentally for the drag reduction (s{sup +}=25.2) and drag increasing (s{sup +}=40.6) cases. The field of view used for the velocity field measurement was 6.75 x 6.75 mm{sup 2} in physical dimension, containing two grooves. One thousand instantaneous velocity fields over the riblets were extracted for the both cases of drag increase and decrease. For comparison, five hundreds instantaneous velocity fields over a smooth flat plate were also extracted under the same flow conditions. For the drag decreasing case (s{sup +}=25.2), most of the streamwise vortices stay above the riblets, interacting with the riblet tips. The high-speed in-rush flow toward the riblet surface rarely influences the flow inside the riblet valleys submerged in the viscous sublayer. The riblet tips seem to impede the spanwise movement of the longitudinal vortices, causing the secondary vortices to restrict the growth of the streamwise vortices. The turbulent kinetic energy in the riblet valley is sufficiently small to compensate the increased wetted surface area of the riblets. In addition, in the log region, the turbulent energy are small or almost equal to that of a smooth flat plate. For the drag increasing case (s{sup +}=40.6), however, the streamwise vortices move into the riblet valley freely, interacting directly with the riblet inner surface. The penetration of the high-speed in-rush flow on the riblets increases the skin-friction. The turbulent kinetic energy is increased in the riblet valleys and in the outer region compared to that over a flat plate. (author). 7 refs., 10 figs.

  15. Giant Drag Reduction in Complex Fluid Drops on Rough Hydrophobic Surfaces

    Science.gov (United States)

    Luu, Li-Hua; Forterre, Yoël

    2013-05-01

    We describe a new spreading regime during the drop impact of model yield-stress fluids (Carbopol microgel solutions) on rough hydrophobic surfaces, in a range of parameters where classical Newtonian drops usually splash. For large surface roughness and high impact velocity, we observe that the maximal inertial spreading diameter of the drops can be as much as twice larger than on smooth surfaces in the same conditions, corresponding to apparent basal friction reductions of more than 80%. We interpret this large drag reduction using a simple energy balance model and a dynamic slip length that depends on both the surface roughness and the drop’s dynamics.

  16. Transonic Drag Reduction Through Trailing-Edge Blowing on the FAST-MAC Circulation Control Model

    Science.gov (United States)

    Chan, David T.; Jones, Gregory S.; Milholen, William E., II; Goodliff, Scott L.

    2017-01-01

    A third wind tunnel test of the FAST-MAC circulation control semi-span model was completed in the National Transonic Facility at the NASA Langley Research Center where the model was configured for transonic testing of the cruise configuration with 0deg flap detection to determine the potential for transonic drag reduction with the circulation control blowing. The model allowed independent control of four circulation control plenums producing a high momentum jet from a blowing slot near the wing trailing edge that was directed over a 15% chord simple-hinged ap. Recent upgrades to transonic semi-span flow control testing at the NTF have demonstrated an improvement to overall data repeatability, particularly for the drag measurement, that allows for increased confidence in the data results. The static thrust generated by the blowing slot was removed from the wind-on data using force and moment balance data from wind-o thrust tares. This paper discusses the impact of the trailing-edge blowing to the transonic aerodynamics of the FAST-MAC model in the cruise configuration, where at flight Reynolds numbers, the thrust-removed corrected data showed that an overall drag reduction and increased aerodynamic efficiency was realized as a consequence of the blowing.

  17. FUSELAGE SHAPE OPTIMIZATION AIMED AT WING-FUSELAGE CONFIGURATION DRAG REDUCTION AT SUPERSONIC SPEEDS

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available The problem of fuselage shape optimization of the wing-body configuration is considered in the following three formulations. In the first one, the angle of attack is fixed and equal to zero, the wing has a symmetric airfoil, and the fuse- lage is based on circular cross sections. In the second one, the fuselage cross sections are elliptical. In the third one, the angle of attack is varied, the lifting force coefficient is fixed, the wing is preliminary optimized, the fuselage is designed by the cross sections that consist of upper and lower half-ellipses with a possibility of a shift along vertical axis. The configu- ration volume, fuselage length, shape and position of the wing are fixed. The drag coefficient is the objective function. The optimization is carried out by the Indirect Optimization based on Self-Organization (IOSO technology. Aerodynamic coef- ficients are obtained from the solution of the RANS equations with SST turbulence model by the ANSYS CFX software on the structured multiblock meshes. The results obtained by the optimization are compared with the configuration that is de- signed by traditional means. The fuselage of this configuration has a cylindrical part in the area of the wing-fuselage con- nection and nose part of the von Karman’s ogive shape. The solution of the optimization problem in the first formulation reduces drag coefficient at zero angle of attack by approximately 3 %. The use of the fuselage with elliptical cross sections makes it possible to reduce drag coefficient at zero angle of attack by 9 %. The solution of the optimization problem in first two formulations reduces drag coefficient at the wide range of angles of attack. When the lifting coefficient is selected for the third problem formulation as constraint the drag reduction is about 7 %. Additional drag reduction of about 2,5 % is obtained by the use of the fuselage asymmetric relative to the horizontal plane. The optimal fuselage design has a

  18. An Experimental Study of Drag Reduction in a Pipe with Superhydrophobic Coating at Moderate Reynolds Numbers

    Directory of Open Access Journals (Sweden)

    Kuo L.

    2010-06-01

    Full Text Available This paper experimentally investigates drag reduction, durability for operations and effects for preventing microorganism from adhering to the surface when the superhydrophobic coating is applied on a solid surface. The experiments are divided into two parts. In the first part, a pipe flow system was established to measure the drag and to test the durability of the micro-structure of superhydrophobic coating at average speeds varying from 1m/sec to 6m/sec. In the second part, we tested the effect for preventing microorganism from adhering to the surface by putting the coated steel plates into sea water. There are four different superhydrophobic coatings in the present study. The experimental results were compared to those applied by ship paint usually used at CSBC.

  19. Limiting Maximum Drag Reduction Asymptote for the Moment Coefficient of an Enclosed Rotating Disk with Fine Spiral Grooves

    Directory of Open Access Journals (Sweden)

    Budiarso Budiarso

    2010-10-01

    Full Text Available In this study, the limiting maximum drag reduction asymptote for the moment coefficient of an enclosed rotating disk with fine spiral grooves in turbulent flow region were obtained analytically. Analysis which were based on an assumption for a simple parabolic velocity distribution of turbulent pipe flow to represent relative tangential velocity, was carried out using momentum integral equations of the boundary layer. For a certain K- parameter the moment coefficient results agree well with experimental results for maximum drag reduction in an enclosed rotating disk with fine spiral grooves and drag reduction ratio approximately was 15 %. Additionally, the experimental results for drag reduction on a rotating disk can be explained well with the analytical results.

  20. Aeroelastic Modeling of Elastically Shaped Aircraft Concept via Wing Shaping Control for Drag Reduction

    Science.gov (United States)

    Nguyen, Nhan; James Urnes, Sr.

    2012-01-01

    Lightweight aircraft design has received a considerable attention in recent years as a means for improving cruise efficiency. Reducing aircraft weight results in lower lift requirements which directly translate into lower drag, hence reduced engine thrust requirements during cruise. The use of lightweight materials such as advanced composite materials has been adopted by airframe manufacturers in current and future aircraft. Modern lightweight materials can provide less structural rigidity while maintaining load-carrying capacity. As structural flexibility increases, aeroelastic interactions with aerodynamic forces and moments become an increasingly important consideration in aircraft design and aerodynamic performance. Furthermore, aeroelastic interactions with flight dynamics can result in issues with vehicle stability and control. Abstract This paper describes a recent aeroelastic modeling effort for an elastically shaped aircraft concept (ESAC). The aircraft model is based on the rigid-body generic transport model (GTM) originally developed at NASA Langley Research Center. The ESAC distinguishes itself from the GTM in that it is equipped with highly flexible wing structures as a weight reduction design feature. More significantly, the wings are outfitted with a novel control effector concept called variable camber continuous trailing edge (VCCTE) flap system for active control of wing aeroelastic deflections to optimize the local angle of attack of wing sections for improved aerodynamic efficiency through cruise drag reduction and lift enhancement during take-off and landing. The VCCTE flap is a multi-functional and aerodynamically efficient device capable of achieving high lift-to-drag ratios. The flap system is comprised of three chordwise segments that form the variable camber feature of the flap and multiple spanwise segments that form a piecewise continuous trailing edge. By configuring the flap camber and trailing edge shape, drag reduction could be

  1. Drag Reduction of a Turbulent Boundary Layer over an Oscillating Wall and Its Variation with Reynolds Number

    Directory of Open Access Journals (Sweden)

    Martin Skote

    2015-01-01

    Full Text Available Spanwise oscillation applied on the wall under a spatially developing turbulent boundary layer flow is investigated using direct numerical simulation. The temporal wall forcing produces a considerable drag reduction over the region where oscillation occurs. Downstream development of drag reduction is investigated from Reynolds number dependency perspective. An alternative to the previously suggested power-law relation between Reynolds number and peak drag reduction values, which is valid for channel flow as well, is proposed. Considerable deviation in the variation of drag reduction with Reynolds number between different previous investigations of channel flow is found. The shift in velocity profile, which has been used in the past for explaining the diminishing drag reduction at higher Reynolds number for riblets, is investigated. A new predictive formula is derived, replacing the ones found in the literature. Furthermore, unlike for the case of riblets, the shift is varying downstream in the case of wall oscillations, which is a manifestation of the fact that the boundary layer has not reached a new equilibrium over the limited downstream distance in the simulations. Taking this into account, the predictive model agrees well with DNS data. On the other hand, the growth of the boundary layer does not influence the drag reduction prediction.

  2. On the Application of Contour Bumps for Transonic Drag Reduction(Invited)

    Science.gov (United States)

    Milholen, William E., II; Owens, Lewis R.

    2005-01-01

    The effect of discrete contour bumps on reducing the transonic drag at off-design conditions on an airfoil have been examined. The research focused on fully-turbulent flow conditions, at a realistic flight chord Reynolds number of 30 million. State-of-the-art computational fluid dynamics methods were used to design a new baseline airfoil, and a family of fixed contour bumps. The new configurations were experimentally evaluated in the 0.3-m Transonic Cryogenic Tunnel at the NASA Langley Research center, which utilizes an adaptive wall test section to minimize wall interference. The computational study showed that transonic drag reduction, on the order of 12% - 15%, was possible using a surface contour bump to spread a normal shock wave. The computational study also indicated that the divergence drag Mach number was increased for the contour bump applications. Preliminary analysis of the experimental data showed a similar contour bump effect, but this data needed to be further analyzed for residual wall interference corrections.

  3. An Experimental Study of Polymer Drag Reduction and Boundary Layer Diffusion Characteristics for Incompressible Flow Over a Flat Plate.

    Science.gov (United States)

    1979-08-15

    Macromolecular Solutions," Hendon College of Technology, London, 1966. ___, "Turbulence and Drag Reduction With Polymer Additives," Research Bulletin...no. 4, Hendon College of Technology, London, January 1967. White, F. N., "An Analysis of Flat-Plate Drag With Polymer Additives," Journal of... Christoph , G. H., "A Simple Theory for the Two-Diensional Compressible Turbulent Boundary Layer," Transactions of the ASHE, September 1972. White, F. M

  4. Drag reduction of a car model by linear genetic programming control

    Science.gov (United States)

    Li, Ruiying; Noack, Bernd R.; Cordier, Laurent; Borée, Jacques; Harambat, Fabien

    2017-08-01

    We investigate open- and closed-loop active control for aerodynamic drag reduction of a car model. Turbulent flow around a blunt-edged Ahmed body is examined at ReH≈ 3× 105 based on body height. The actuation is performed with pulsed jets at all trailing edges (multiple inputs) combined with a Coanda deflection surface. The flow is monitored with 16 pressure sensors distributed at the rear side (multiple outputs). We apply a recently developed model-free control strategy building on genetic programming in Dracopoulos and Kent (Neural Comput Appl 6:214-228, 1997) and Gautier et al. (J Fluid Mech 770:424-441, 2015). The optimized control laws comprise periodic forcing, multi-frequency forcing and sensor-based feedback including also time-history information feedback and combinations thereof. Key enabler is linear genetic programming (LGP) as powerful regression technique for optimizing the multiple-input multiple-output control laws. The proposed LGP control can select the best open- or closed-loop control in an unsupervised manner. Approximately 33% base pressure recovery associated with 22% drag reduction is achieved in all considered classes of control laws. Intriguingly, the feedback actuation emulates periodic high-frequency forcing. In addition, the control identified automatically the only sensor which listens to high-frequency flow components with good signal to noise ratio. Our control strategy is, in principle, applicable to all multiple actuators and sensors experiments.

  5. Anomalous Drag Reduction and Hydrodynamic Interactions of Nanoparticles in Polymer Nanocomposite Thin Films

    Science.gov (United States)

    Basu, Jaydeep; Begam, Nafisa; Chandran, Sivasurender; Sprung, Michael

    2015-03-01

    One of the central dogma of fluid physics is the no-slip boundary condition whose validity has come under intense scrutiny, especially in the fields of micro and nanofluidics. Although various studies show the violation of the no-slip condition its effect on flow of colloidal particles in viscous media has been rarely explored. Here we report unusually large reduction of effective drag experienced by polymer grafted nanoparticles moving through a highly viscous film of polymer, well above its glass transition temperature. The extent of drag reduction increases with decreasing temperature and polymer film thickness. We also observe apparent divergence of the wave vector dependent hydrodynamic interaction function of these nanoparticles with an anomalous power law exponent of ~ 2 at the lowest temperatures and film thickness. Such strong hydrodynamic interactions are not expected in polymer melts where these interactions are known to be screened to molecular dimensions. We provide evidence for the presence of large hydrodynamic slip at the nanoparticle-polymer interface and demonstrate its tunability with temperature and confinement. Our study suggests novel physics emerging in dynamics nanoparticles due to confinement and interface wettability in thin films of polymer nanocomposites.

  6. Skin-friction Drag Reduction in Turbulent Channel Flow with Idealized Superhydrophobic Walls

    Science.gov (United States)

    Ratsegari, Amirreza; Akhavan, Rayhaneh

    2013-11-01

    Skin-friction drag reduction by super-hydrophobic (SH) surfaces was investigated using Lattice Boltzmann DNS in turbulent channel flow with SH longitudinal microgrooves on both walls. The liquid/gas interfaces in the SH microgrooves were modeled as flat, shear-free surfaces. Drag reductions (DR) ranging from 5 % to 47 % were observed for microgrooves of size 4 base flow wall units. It is shown that in both laminar and turbulent flow, DR scales as DR =Us /Ub + ɛ . In laminar flow, where DR is purely due to surface slip, ɛ = 0 . In turbulent flow, ɛ remains negligible when the slip length is smaller than the thickness of the viscous sublayer. For DR > 40 % , where the effect of surface slip can be felt in the buffer layer, ɛ attains a small non-zero value. Analysis of turbulence statistics and turbulence kinetic energy budgets confirms that outside of a layer of size approximately one slip length from the walls, the turbulence dynamics proceeds as in regular channel flow with no-slip walls.

  7. Onset and universality of turbulent drag reduction in von Karman swirling flow

    Science.gov (United States)

    Burnishev, Yuri; Steinberg, Victor

    2012-10-01

    We report the results of experiments on turbulent drag reduction (TDR) in swirling flow of water and water-sucrose polymer solutions, where Re and Wi as well as polymer concentration ϕ are varied. The friction coefficients Cf and Cp defined through average torque \\bar {\\Gamma } and rms of pressure fluctuations prms for different elasticity El = Wi/Re and ϕ vs. Re/Rec collapse onto universal curves in accord with theory, where Rec is Re at TDR onset. The transition lines to the TDR state, Rec - El and Rec - ϕ, are measured and relevant physics is discussed. Power spectra for Γ and p at Re/Rec > 1 show a drastic reduction of low-frequency noise and the emergence of a peak corresponding to the main vortex frequency in accord with TDR.

  8. Experimental investigation on momentum and drag reduction of Malaysian crop suspensions in closed conduit flow

    Science.gov (United States)

    Ahmed, S. M.; Kazi, S. N.; Khan, G.; Dahari, M.; Zubir, M. N. M.; Ahmad, P.; Montazer, E.

    2017-06-01

    The study of frictional losses in fiber suspension flow is one of the significant scientific interests as the characteristics of suspension flow considerably changes with shear stress, fiber source, and treatments applied on fibers. Pressure drop measurements were obtained for different Malaysian crop fiber suspensions flowing through a closed conduit. The generated data were gathered over a range of flow rates and suspension concentrations. It was found that the magnitude of the pressure drop of the fiber suspensions is dependent on the concentration, characteristics, and fiber source. Considerable drag reduction is obtained for concentration of 0.6 wt. % at high flow rates. Such a reduction of pressure drop at the particular concentrations and the flow rates is interesting and useful as these data can be used for design and optimization of fiber handling equipment and piping systems. Furthermore, the effect of different fibers, fiber properties and flexibility on pressure drop were studied.

  9. Study of Key Non-dimensional Parameters for Wave Drag Reduction with High-Frequency Repetitive Laser Pulse Energy Depositions

    Directory of Open Access Journals (Sweden)

    Qing Zexu

    2016-01-01

    Full Text Available The problem of wave drag reduction with high-frequency repetitive laser pulse energy depositions is multivariable. Three key non-dimensional parameters, non-dimensional energy, non-dimensional depositing position and Mach number, were constructed from a number of original variables by using Buckingham pi theorem. Influences of these non-dimensional parameters on energy deposition performance, namely drag reduction and energy deposition efficiency, were investigated numerically by solving three-dimensional Navier-Stokes equations with an upwind scheme. Optimizing method of non-dimensional energy and non-dimensional depositing position is proposed. Drag reduction and energy deposition efficiency have exponential relationships with non-dimensional energy; Drag reduction and energy deposition efficiency have quadratic relationships with non-dimensional depositing position. Drag reduction has exponential relationship with freestream Mach number and energy deposition efficiency has quadratic relationship with Mach number. Non-dimensional laser energy and non-dimensional depositing position should be optimized synthetically for a given freestream.

  10. Drag reduction in oil flows; Reducao da perda de carga durante o escoamento de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Rocha, Nelson de Oliveira; Carvalho, Carlos Henrique M. de; Ziglio, Claudio Marcos [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas; Noronha, Francisco de Assis; Silva, Aldo Manoel Borburema da [PETROBRAS S.A., Natal, RN (Brazil). Unidade de Negocio RN/CE; Santos, Anderson Oliveira; Rizzo, Rodrigo Gouveia de O.; Sanatana, Marcos Antonio de Oliveira [PETROBRAS S.A., Aracaju, SE (Brazil). Unidade de Negocio SE/AL

    2008-07-01

    The strong world demand for petroleum has increased interest in optimizing the production from mature fields. To do this, it is necessary to use recovery methods that are associated with others that generally use water and/or steam injection, aimed at increasing the production. In parallel with the increase in water production from mature fields, it is evident that there is an increase in viscosity of the liquid phase. This is due to the formation of an emulsion during the lift and flow processes, principally caused by the agitation and shearing, which in turn provoke less oil mobility and high pressure in the production systems. For this reason the oil flow has become a challenge to the production and this is highlighted in the technological innovation scenario in the petroleum industry. Different situations are observed in the production scenario where the following are found: oil production with high BSW, low BSW and /or stable emulsions. The study of the phenomenon to reduce the drag during the turbulent flow, through the injection of polymeric type chemical additives with high molecular weight has been the subject of various surveys over the past few years. The employment of chemical additives containing a drag-reducing agent known as DRA (Drag-Reducing Agents), in turbulent flows, allows for a lower pressure to maintain or to even increase the production capacity. In this study, a mathematic equation of the problem will be presented and the operational methods employed. The performance of different multi functional chemical additives are shown, which are capable of maintaining the flow, either by breaking the emulsion, or by modifying the flow regime, culminating in the reduction of the loss of load during the production flow. (author)

  11. Statistical comparison of coherent structures in fully developed turbulent pipe flow with and without drag reduction

    Science.gov (United States)

    Sogaro, Francesca; Poole, Robert; Dennis, David

    2014-11-01

    High-speed stereoscopic particle image velocimetry has been performed in fully developed turbulent pipe flow at moderate Reynolds numbers with and without a drag-reducing additive (an aqueous solution of high molecular weight polyacrylamide). Three-dimensional large and very large-scale motions (LSM and VLSM) are extracted from the flow fields by a detection algorithm and the characteristics for each case are statistically compared. The results show that the three-dimensional extent of VLSMs in drag reduced (DR) flow appears to increase significantly compared to their Newtonian counterparts. A statistical increase in azimuthal extent of DR VLSM is observed by means of two-point spatial autocorrelation of the streamwise velocity fluctuation in the radial-azimuthal plane. Furthermore, a remarkable increase in length of these structures is observed by three-dimensional two-point spatial autocorrelation. These results are accompanied by an analysis of the swirling strength in the flow field that shows a significant reduction in strength and number of the vortices for the DR flow. The findings suggest that the damping of the small scales due to polymer addition results in the undisturbed development of longer flow structures.

  12. Bio-inspired Gecko Micro-surface for Drag Reduction in Turbulent Flows

    Science.gov (United States)

    Arenas, Isnardo; Carrasquillo, Kenneth; Araya, Guillermo; Castillo, Luciano; Leonardi, Stefano

    2014-11-01

    Direct Numerical Simulations of a turbulent channel flow with a porous wall inspired from the Gecko lizard were performed at Reynolds number of Reτ = 450 . Two superposed fluids were considered. As initial condition, one fluid fills the microfibrillar surface, the interface with the overlying fluid being flat and corresponding to the crests plane. The code is based on a finite difference scheme with a Runge Kutta and fractional step. The porous wall is modeled with the immersed boundary method, while the dynamic of the interface between the two fluids is solved with a level set method. A parametric study has been performed varying the viscosity ratio between the two fluids. Two cases have been considered, with and without surface tension. Without surface tension the microfibrillar wall acts as a rough wall increasing the drag. However, when the surface tension is large enough to maintain the interface stable, the external fluid cannot enter into the porous wall and an effective slip is produced. When the fluid in the porous wall has a viscosity 100 times smaller than that of the overlying fluid, a drag reduction of about 60 % can be observed. In this case, the near wall coherent structures become significantly weaker. The numerical simulations were performed on XSEDE TACC under Grant No. CTS070066. S.L., I.A. and K.C. were supported by ONR MURI grant.

  13. Drag reduction of a 3D bluff body using coherent streamwise streaks

    Science.gov (United States)

    Pujals, G.; Depardon, S.; Cossu, C.

    2010-11-01

    Separation on the rear-end of an Ahmed body is suppressed by means of large-scale coherent streaks forced on the roof of the model. These streaks originate from an array of suitably shaped cylindrical roughness elements and are amplified by the mean shear through the lift-up effect. Interacting with the mean velocity field at leading order, they induce a strong controlled spanwise modulation. The resulting streaky base flow is observed to sustain the adverse pressure gradient since PIV measurements as well as static wall pressure distributions show that the re-circulation bubble completely vanishes. These modifications of the topology of the flow are associated with a substantial drag reduction, which can be of about 10% when the roughness array is optimally placed on the roof of the bluff body.

  14. LEBU drag reduction in high Reynolds number boundary layers. [Large Eddy Break-Up

    Science.gov (United States)

    Anders, J. B.

    1989-01-01

    Conventional and inverted, outer-layer leading-edge breakup devices (LEBUs) were water tunnel tested on an axisymmetric body over the Re number range from 380,000 to 3.8 million. Test results indicate a sharp degradation of the LEBUs' drag-reduction mechanism with increasing Re number. The most likely result of this degradation is a decoupling of the inner and outer scales at higher Re numbers; due to this decoupling, the breakup of the large structures by outer-layer devices has minimal influence on the near-wall, shear-producing scales. This suggests that smaller devices, closer to the walls, may be required for operation at elevated Re numbers.

  15. Drag-Reduction Effectiveness of Riblet Films in Adverse Pressure Gradients

    Science.gov (United States)

    Boomsma, Aaron; Sotiropoulos, Fotis

    2013-11-01

    Riblet films are micro-grooved structures that are widely known to passively reduce skin friction. Past studies have almost solely focused on riblet performance in channel-flows. However, possible applications of riblets include wind turbine blades, gas turbine blades, and other complex bodies that are exposed to non-zero pressure gradient flows--specifically adverse pressure gradients. We use high-resolution large eddy simulations of turbulent flow over three-dimensional riblets under an adverse pressure gradient. We analyze the computed results to quantify drag reduction effectiveness for different riblet shapes and to examine pertinent turbulent structures to gain a fundamental understanding of riblet performance. Supported by the DOE Wind Energy Consortium

  16. Intelligent Control for Drag Reduction on the X-48B Vehicle

    Science.gov (United States)

    Griffin, Brian Joseph; Brown, Nelson Andrew; Yoo, Seung Yeun

    2011-01-01

    This paper focuses on the development of an intelligent control technology for in-flight drag reduction. The system is integrated with and demonstrated on the full X-48B nonlinear simulation. The intelligent control system utilizes a peak-seeking control method implemented with a time-varying Kalman filter. Performance functional coordinate and magnitude measurements, or independent and dependent parameters respectively, are used by the Kalman filter to provide the system with gradient estimates of the designed performance function which is used to drive the system toward a local minimum in a steepestdescent approach. To ensure ease of integration and algorithm performance, a single-input single-output approach was chosen. The framework, specific implementation considerations, simulation results, and flight feasibility issues related to this platform are discussed.

  17. Drag reduction by polyethylene glycol in the tail arterial bed of normotensive and hypertensive rats

    Directory of Open Access Journals (Sweden)

    K.L. Bessa

    2011-08-01

    Full Text Available This study was designed to evaluate the effect of drag reducer polymers (DRP on arteries from normotensive (Wistar and spontaneously hypertensive rats (SHR. Polyethylene glycol (PEG 4000 at 5000 ppm was perfused in the tail arterial bed with (E+ and without endothelium (E- from male, adult Wistar (N = 14 and SHR (N = 13 animals under basal conditions (constant flow at 2.5 mL/min. In these preparations, flow-pressure curves (1.5 to 10 mL/min were constructed before and 1 h after PEG 4000 perfusion. Afterwards, the tail arterial bed was fixed and the internal diameters of the arteries were then measured by microscopy and drag reduction was assessed based on the values of wall shear stress (WSS by computational simulation. In Wistar and SHR groups, perfusion of PEG 4000 significantly reduced pulsatile pressure (Wistar/E+: 17.5 ± 2.8; SHR/E+: 16.3 ± 2.7%, WSS (Wistar/E+: 36; SHR/E+: 40% and the flow-pressure response. The E- reduced the effects of PEG 4000 on arteries from both groups, suggesting that endothelial damage decreased the effect of PEG 4000 as a DRP. Moreover, the effects of PEG 4000 were more pronounced in the tail arterial bed from SHR compared to Wistar rats. In conclusion, these data demonstrated for the first time that PEG 4000 was more effective in reducing the pressure-flow response as well as WSS in the tail arterial bed of hypertensive than of normotensive rats and these effects were amplified by, but not dependent on, endothelial integrity. Thus, these results show an additional mechanism of action of this polymer besides its mechanical effect through the release and/or bioavailability of endothelial factors.

  18. The Use of Biobased Surfactant Obtained by Enzymatic Syntheses for Wax Deposition Inhibition and Drag Reduction in Crude Oil Pipelines

    Directory of Open Access Journals (Sweden)

    Zhihua Wang

    2016-04-01

    Full Text Available Crude oil plays an important role in providing the energy supply of the world, and pipelines have long been recognized as the safest and most efficient means of transporting oil and its products. However, the transportation process also faces the challenges of asphaltene-paraffin structural interactions, pipeline pressure losses and energy consumption. In order to determine the role of drag-reducing surfactant additives in the transportation of crude oils, experiments of wax deposition inhibition and drag reduction of different oil in pipelines with a biobased surfactant obtained by enzymatic syntheses were carried out. The results indicated that heavy oil transportation in the pipeline is remarkably enhanced by creating stable oil-in-water (O/W emulsion with the surfactant additive. The wax appearance temperature (WAT and pour point were modified, and the formation of a space-filling network of interlocking wax crystals was prevented at low temperature by adding a small concentration of the surfactant additive. A maximum viscosity reduction of 70% and a drag reduction of 40% for light crude oil flows in pipelines were obtained with the surfactant additive at a concentration of 100 mg/L. Furthermore, a successful field application of the drag-reducing surfactant in a light crude oil pipeline in Daqing Oilfield was demonstrated. Hence, the use of biobased surfactant obtained by enzymatic syntheses in oil transportation is a potential method to address the current challenges, which could result in a significant energy savings and a considerable reduction of the operating cost.

  19. Prediction of drag reduction performance of actual L-shaped riblets with a modified k-{epsilon} model

    Energy Technology Data Exchange (ETDEWEB)

    Myong, H.K. [Kookmin University, Seoul (Korea, Republic of)

    1998-10-01

    A low-Reynolds-number k-{epsilon} turbulence model is applied to predict drag reduction performance for actual L-shaped (blade-type) riblets with finite-thickness in fully-developed flows between infinite parallel planes. The present turbulence model is a modified version of the Launder & Sharma`s k-{epsilon} model (LS model), in which the gradient production term in {epsilon}-equation is modeled to have only the normal derivative terms. The present predictions for drag reduction behavior such as the maximum drag reduction and effects of riblets on turbulence quantities are in good agreement with both the experiments and the recent DNS results: differences in the mean velocity profile and turbulent quantities are found to be limited to the riblet cavity region. Turbulence quantities are also reduced in drag-reducing configurations. Possible shortcomings in the present model using an isotropic turbulent viscosity are also discussed particularly with reference to the absence of any turbulence-driven secondary motions. (author). 14 refs., 9 figs.

  20. Drag reduction for the combination of spike and counterflow jet on blunt body at high Mach number flow

    Science.gov (United States)

    Eghlima, Z.; Mansour, K.

    2017-04-01

    Drag reduction at high speed flows around blunt bodies is one of the major challenges in the field of aerodynamics. Using of spikes and counterflow jets each of them separately for reducing of drag force is well known. The present work is description of flow field around a hemispherical nose cylinder with a new combination of spike and counterflow jet at free stream of Mach number of 6.The air gas was injected through the nozzle at the nose of the hemispherical model at sonic speed. In this numerical analysis, axisymmetric Reynolds-averaged Navier-Stokes equations was solved by k-ω (SST) turbulence model. The results were validated with experimental results for spiked body without jet condition. Then the results presented for different lengths of spike and different pressures of counterflow jets. The results show a significant reduction in the drag coefficient about 86-90% compared to the spherical cylinder model without jet and spike for practical models (L/D=1.5 and 2). Furthermore also our results indicate that the drag reduction is increased even more with increasing of the length of the spike.

  1. Influence Study of the Viscoelastic Fluids Features in Drag Reduction in Laminar Regime Flow in Pipeline

    Directory of Open Access Journals (Sweden)

    Vilalta Guillermo

    2016-01-01

    Full Text Available The drag reduction by polymer addition is wide interest in several areas. It has been shown that the polymer addition cushions the dissipative effects in turbulent flows. The main objective of this work is to establish a methodology for the numerical simulation of viscoelastic fluid through internal subroutines implemented in the Fluent code, via UDF. The validation of this methodology is made for the laminar flow regime case in pipeline. To describe the viscoelastic effect, it was used the Finitely Extensible Nonlinear Elastic model closing with Peterlin model. To taking in account the viscous effects 50≤Re≤2000 values were used. In addition, for the polymer concentration analysis it was used values which depend on the polymers molecular weight and the solution concentration that ranged from 0≤Cw≤20. The molecular elasticity and extensibility were maintained at constant values. The results showed that the addition of polymers regardless of their molecular weight in laminar flow regime causes no change in power dissipation. This result, which is consistent with the literature, is a significant advance in defining a credible and appropriate methodology to viscoelastic fluid flow study by UDF implementation of constituent models that characterize these fluids.

  2. Drag reduction of a car model by linear genetic programming control

    CERN Document Server

    Li, Ruiying; Cordier, Laurent; Borée, Jacques; Harambat, Fabien; Kaiser, Eurika; Duriez, Thomas

    2016-01-01

    We investigate open- and closed-loop active control for aerodynamic drag reduction of a car model. Turbulent flow around a blunt-edged Ahmed body is examined at $Re_{H}\\approx3\\times10^{5}$ based on body height. The actuation is performed with pulsed jets at all trailing edges combined with a Coanda deflection surface. The flow is monitored with pressure sensors distributed at the rear side. We apply a model-free control strategy building on Dracopoulos & Kent (Neural Comput. & Applic., vol. 6, 1997, pp. 214-228) and Gautier et al. (J. Fluid Mech., vol. 770, 2015, pp. 442-457). The optimized control laws comprise periodic forcing, multi-frequency forcing and sensor-based feedback including also time-history information feedback and combination thereof. Key enabler is linear genetic programming as simple and efficient framework for multiple inputs (actuators) and multiple outputs (sensors). The proposed linear genetic programming control can select the best open- or closed-loop control in an unsupervis...

  3. Numerical Study of the Generic Sports Utility Vehicle Design with a Drag Reduction Add-On Device

    Directory of Open Access Journals (Sweden)

    Shubham Singh

    2014-01-01

    Full Text Available CFD simulations using ANSYS FLUENT 6.3.26 have been performed on a generic SUV design and the settings are validated using the experimental results investigated by Khalighi. Moreover, an add-on inspired by the concept presented by Englar at GTRI for drag reduction has been designed and added to the generic SUV design. CFD results of add-on model and the basic SUV model have been compared for a number of aerodynamic parameters. Also drag coefficient, drag force, mean surface pressure, mean velocities, and Cp values at different locations in the wake have been compared for both models. The main objective of the study is to present a new add-on device which may be used on SUVs for increasing the fuel efficiency of the vehicle. Mean pressure results show an increase in the total base pressure on the SUV after using the device. An overall reduction of 8% in the aerodynamic drag coefficient on the add-on SUV has been investigated analytically in this study.

  4. Effect of riblet shape on turbulent drag reduction; Ranryu masatsu teiko gensho ni oyobosu riblet keijo no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, S.; Takiguchi, K. [Shibaura Institute of Technology, Tokyo (Japan); Uchida, T. [Sanyo Electric Co. Ltd., Osaka (Japan); Yoneyama, T. [Honda Motor Co. Ltd., Tokyo (Japan); Kimura, S. [Tokyo Institute of Technology, Tokyo (Japan)

    2000-02-25

    This paper presents an effect of riblet shape on turbulent drag reduction. The experiment was carried out in an N. P. L. blow-down-type wind tunnel with a working section of 500 mm x 500 mm x 2,000 mm. In order to investigate the details of drag reduction for riblet shape, rib models of scaling up riblets were used in this experiment. The parameters were 5 kinds for the rib model and 7 kinds for the riblet model. The time-mean velocity and skin friction were measured by the Pitot and static pressure tubes and Preston tube respectively. The Reynolds stress was obtained using the data processing system connected to a hot wire anemometer. Consequently it was found that (1) the Reynolds stress and skin friction become smallest near the surface for the rib with the section of an equilateral triangle, and (2) the drag reduction attains maximum for the riblet of V groove with nearly equilateral triangular section. (author)

  5. Fluid drag reduction and efficient self-cleaning with rice leaf and butterfly wing bioinspired surfaces.

    Science.gov (United States)

    Bixler, Gregory D; Bhushan, Bharat

    2013-09-07

    Researchers are continually inspired by living nature to solve complex challenges. For example, unique surface characteristics of rice leaves and butterfly wings combine the shark skin (anisotropic flow leading to low drag) and lotus leaf (superhydrophobic and self-cleaning) effects, producing the so-called rice and butterfly wing effect. In this paper, we present an overview of rice leaf and butterfly wing fluid drag and self-cleaning studies. In addition, we examine two other promising aquatic surfaces in nature known for such properties, including fish scales and shark skin. Morphology, drag, self-cleaning, contact angle, and contact angle hysteresis data are presented to understand the role of wettability, viscosity, and velocity. Liquid repellent coatings are utilized to recreate or combine various effects. Discussion is provided along with conceptual models describing the role of surface structures related to low drag, self-cleaning, and antifouling properties. Modeling provides design guidance when developing novel low drag and self-cleaning surfaces for applications in the medical, marine, and industrial fields.

  6. Drag-Free Performance of the ST7 Disturbance Reduction System Flight Experiment on the LISA Pathfinder

    Science.gov (United States)

    Maghami, Peiman; O'Donnell, James, Jr.; Hsu, Oscar; Ziemer, John; Dunn, Charles

    2017-01-01

    The Space Technology-7 Disturbance Reduction System (DRS) is an experiment package aboard the European Space Agency (ESA) LISA Pathfinder spacecraft. LISA Pathfinder launched from Kourou, French Guiana on December 3, 2015. The DRS is tasked to validate two specific technologies: colloidal micro-Newton thrusters (CMNT) to provide low-noise control capability of the spacecraft, and drag-free control flight. This validation is performed using highly sensitive drag-free sensors, which are provided by the LISA Technology Package of the European Space Agency. The Disturbance Reduction System is required to maintain the spacecrafts position with respect to a free-floating test mass to better than 10nmHz, along its sensitive axis (axis in optical metrology). It also has a goal of limiting the residual accelerations of any of the two test masses to below 30 (1 + [f3 mHz]) fmsHz, over the frequency range of 1 to 30 mHz.This paper briefly describes the design and the expected on-orbit performance of the control system for the two modes wherein the drag-free performance requirements are verified. The on-orbit performance of these modes are then compared to the requirements, as well as to the expected performance, and discussed.

  7. Investigation of drag and heat reduction induced by a novel combinational lateral jet and spike concept in supersonic flows based on conjugate heat transfer approach

    Science.gov (United States)

    Zhu, Liang; Chen, Xiong; Li, Yingkun; Musa, Omer; Zhou, Changsheng

    2018-01-01

    When flying at supersonic or hypersonic speeds through the air, the drag and severe heating have a great impact on the vehicles, thus the drag reduction and thermal protection studies have attracted worldwide attention. In the current study, the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the shear stress transport (SST) k - ω turbulence model have been employed to investigate the flow behavior induced by a novel combinational lateral jet and spike concept in supersonic flows. A coupling conjugate heat transfer (CHT) approach has been applied to investigate the thermal protection, which takes the heat transfer of structure into consideration. After the code was validated by the available experimental results and the gird independency analysis was carried out, the influences of the spike length ratio, lateral jet pressure ratio and lateral jet location on the drag and heat reduction performance are analyzed comprehensively. The obtained results show that a remarkable reduction in the drag and heat flux is achieved when a lateral jet is added to the spike. This implies that the combinational lateral jet and spike concept in supersonic flows have a great benefit to the drag and heat reduction. Both the drag and heat reduction decrease with the increase of the lateral jet pressure ratio, and the heat flux is more sensitive to the lateral jet pressure ratio. The lateral jet should not be located in the bottom of the spike in order to realize better drag and heat reduction performance. The drag and heat flux could be reduced by about 45% by reasonable lateral jet location. The drag decreases with the increase of the spike length ratio whereas the heat flux is affected by the spike length ratio just in a certain range.

  8. Hydrodynamic sensing does not facilitate active drag reduction in the golden shiner (Notemigonus crysoleucas)

    NARCIS (Netherlands)

    McHenry, M. J.; Michel, K. B.; Stewart, W.; Mueller, U. K.

    2010-01-01

    The lateral line system detects water flow, which allows fish to orient their swimming with respect to hydrodynamic cues. However, it is unclear whether this sense plays a role in the control of propulsion. Hydrodynamic theory suggests that fish could reduce drag by coordinating the motion of the

  9. Drag reduction by surface treatment in turbulent Taylor-Couette flow

    NARCIS (Netherlands)

    Greidanus, A.J.; Delfos, R.; Westerweel, J.

    2011-01-01

    We use a Taylor-Couette facility to study the drag reducing effects of commercial surface products at high shear Reynolds numbers (Res) under perfect couter-rotating conditions (riwi=rowo). The correlation between torque contribution of the von Karman flow and shear Reynolds number is investigated.

  10. Turbulence and turbulent drag reduction in swirling flow: Inertial versus viscous forcing

    Science.gov (United States)

    Burnishev, Yuri; Steinberg, Victor

    2015-08-01

    We report unexpected results of a drastic difference in the transition to fully developed turbulent and turbulent drag reduction (TDR) regimes and in their properties in a von Karman swirling flow with counter-rotating disks of water-based polymer solutions for viscous (by smooth disks) as well as inertial (by bladed disks) forcing and by tracking just torque Γ (t ) and pressure p (t ) . For the viscous forcing, just a single TDR regime is found with the transition values of the Reynolds number (Re) Recturb=RecTDR≃(4.8 ±0.2 ) ×105 independent of ϕ , whereas for the inertial forcing two turbulent regimes are revealed. The first transition is to fully developed turbulence, and the second one is to the TDR regime with both Recturb and RecTDR depending on polymer concentration ϕ . Both regimes differ by the values of Cf and Cp, by the scaling exponents of the fundamental turbulent characteristics, by the nonmonotonic dependencies of skewness and flatness of the pressure PDFs on Re, and by the different frequency power spectra of p with the different dependencies of the main vortex peak frequency in the p power spectra on ϕ and Re. Thus our experimental results show the transition to the TDR regime in a von Karman swirling flow for the viscous and inertial forcings in a sharp contrast to the recent experiments [Phys. Fluids 10, 426 (1998), 10.1063/1.869532; Phys. Rev. E 47, R28(R) (1993), 10.1103/PhysRevE.47.R28; and J. Phys.: Condens. Matter 17, S1195 (2005), 10.1088/0953-8984/17/14/008] where the transition to TDR is observed in the same swirling flow with counter-rotating disks only for the viscous forcing. The latter result has led its authors to the wrong conclusion that TDR is a solely boundary effect contrary to the inertial forcing associated with the bulk effect, and this conception is currently rather widely accepted in literature.

  11. The 'W' prawn-trawl with emphasised drag-force transfer to its centre line to reduce overall system drag.

    Directory of Open Access Journals (Sweden)

    Cheslav Balash

    Full Text Available For prawn trawling systems, drag reduction is a high priority as the trawling process is energy intensive. Large benefits have occurred through the use of multiple-net rigs and thin twine in the netting. An additional positive effect of these successful twine-area reduction strategies is the reduced amount of otter board area required to spread the trawl systems, which leads to further drag reduction. The present work investigated the potential of redirecting the drag-strain within a prawn trawl away from the wings and the otter boards to the centre line of the trawl, where top and bottom tongues have been installed, with an aim to minimise the loading/size of the otter boards required to spread the trawl. In the system containing the new 'W' trawl, the drag redirected to the centre-line tongues is transferred forward through a connected sled and towing wires to the trawler. To establish the extent of drag redirection to the centre-line tongues and the relative drag benefits of the new trawl system, conventional and 'W' trawls of 3.65 m headline length were tested firstly over a range of spread ratios in the flume tank, and subsequently at optimum spread ratio in the field. The developed 'W' trawl effectively directed 64% of netting-drag off the wings and onto the centre tongues, which resulted in drag savings in the field of ∼20% for the associated 'W' trawl/otter-board/sled system compared to the traditional trawl/otter-board arrangement in a single trawl or twin rig configuration. Furthermore, based on previously published data, the new trawl when used in a twin rig system is expected to provide approximately 12% drag reduction compared to quad rig. The twin 'W' trawl system also has benefits over quad rig in that a reduced number of cod-end/By-catch Reduction Device units need to be installed and attended each tow.

  12. Modeling the effect of head drag reduction for a cylinder with a protruding disk at high mach numbers

    Science.gov (United States)

    Isaev, S. A.; Baranov, P. A.; Mikhalev, A. N.; Sudakov, A. G.

    2014-11-01

    Various approaches to modeling super- and hypersonic turbulent airflow past cylindrical bodies with a nontraditional nose in the form of a protruding rod-supported disk have been compared. Aeroballistic experiments on a light-gas propulsion setup were combined with wind tunnel tests and numerical simulations using VP2/3 program package based on multiblock computational techniques and a model of shear stress transport with flow-line curvature corrections. The phenomenon of the head and wave drag reduction for the stepped body is analyzed at high Mach numbers (up to 10) and variation of the supporting rod length under conditions of existence of the frontal flow separation zone.

  13. Flow through an Array of Superhydrophopic Pillars: The Role of the Air-Water Interface Shape on Drag Reduction

    Science.gov (United States)

    Kim, Jeong-Hyun; Rothstein, Jonathan

    2016-11-01

    In this study, measurements of the pressure drop and the velocity fields associated with the flow of water through a regular array of superhydrophobic pillars were systematically performed to investigate the role of the air-water interface shape on drag reduction. A microfluidic channel was created with circular and superhydrophobic apple-core-shaped pillars bridging across the entire channel. The apple-core-shaped pillars were designed to trap an air pocket along the side of the pillars. The shape of the interface was systematically modified from concave to convex by changing the static pressure within the microchannel. For superhydrophobic pillars having a circular cross section, D /D0 = 1.0, a drag reduction of 7% and a slip velocity of 20% the average channel velocity along the air-water interface were measured. At large static pressures, the interface was driven into the pillars resulting in a decrease in the effective size of the pillars, an increase in the effective spacing between pillars and a pressure drop reduction of as much as 18% when the interface was compressed to D /D0 = 0.8. At low static pressures, the pressure drop increased significantly even as the slip velocity increased as the expanding air-water interface constricted flow through the array of pillars. This research was supported by the National Science Foundation under Grant CBET-1334962.

  14. Pressure loss in natural gas pipelines: Experimental studies of gas-particle flow, wall roughness and drag reduction

    Energy Technology Data Exchange (ETDEWEB)

    Strupstad, Andre

    2009-05-15

    Laboratory experiments on air-particle flow were performed in a horizontal once-through flow rig, with internal pipe diameters of 24 mm. Reynolds number was 40000 - 180000, temperatures 20 deg. Celsius and pressure below 2 bara. Spherical polystyrene and magnetite particles with mean diameters from 64 mum to 175 mum were used. The pressure loss in the experiments was best expressed in terms of friction factor. Differential pressure drop gave limited information because reduction in this value was due to change in the gas properties during particle injection. The reduction in the differential pressure was due to the increase in the absolute pressure, which resulted in an increased gas density. This increased density, which with an approximately constant gas mass flow, resulted in a lower volume flow, and thereby a lower gas velocity. A lower gas velocity results in a lower differential pressure. A calculation of the friction factors, which increased, showed that these reductions in the differential pressures were not drag reductions. Roughness measurements were made on three types of surfaces with a stylus instrument: 47 epoxy coated steel surfaces as used in natural gas pipelines, 5 plexiglass surfaces used in our flow experiments, and 9 steel surfaces. The roughness profiles obtained were used to calculate amplitude roughness parameters and texture roughness parameters. Theory of gas-particle drag reduction in pipes was reviewed. Turbulence attenuation was a necessary but not a sufficient condition for drag reduction to occur. Small particle diameter was identified as an important condition for achieving drag reduction. Also, relevant parameters for achieving turbulence attenuation were identified, including the Stokes number, ratio between particle diameter and pipe diameter and the particle Reynolds number. In the flow experiments the gas friction factor increased by up to 16 % with injection of particles as compared to particle free flow. The increase depended

  15. Unique fur and skin structure in harbour seals (Phoca vitulina)--thermal insulation, drag reduction, or both?

    Science.gov (United States)

    Erdsack, Nicola; Dehnhardt, Guido; Witt, Martin; Wree, Andreas; Siebert, Ursula; Hanke, Wolf

    2015-03-06

    Vertebrate surface structures, including mammalian skin and hair structures, have undergone various modifications during evolution in accordance with functional specializations. Harbour seals rely on their vibrissal system for orientation and foraging. To maintain tactile sensitivity even at low temperatures, the vibrissal follicles are heated up intensely, which could cause severe heat loss to the environment. We analysed skin samples of different body parts of harbour seals, and expected to see higher hair densities at the vibrissal pads as a way to reduce heat loss. In addition to significantly higher hair densities around the vibrissae than on the rest of the body, we show a unique fur structure of hair bundles consisting of broad guard hairs along with hairs of a new type, smaller than guard hairs but broader than underhairs, which we defined as 'intermediate hairs'. This fur composition has not been reported for any mammal so far and may serve for thermal insulation as well as drag reduction. Furthermore, we describe a scale-like skin structure that also presumably plays a role in drag reduction. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  16. Drag reduction over dolphin skin via the pondermotive forcing of vortex filaments

    Science.gov (United States)

    Lisi, Antony Garrett

    1999-11-01

    The skin of Tursiops Truncatus is corrugated with small, quasi-periodic ridges running circumferentially about the torso. These ridges extend into the turbulent boundary layer and affect the evolution of coherent structures. The development and evolution of coherent structures over a surface is described by the formation and dynamics of vortex filaments. The dynamics of these filaments over a flat, non-ridged surface is determined analytically, as well as through numerical simulation, and found to agree with the observations of coherent structures in the turbulent boundary layer. The calculation of the linearized dynamics of the vortex filament, successful for the dynamics of a filament over a flat surface, is extended and applied to a vortex filament propagating over a periodically ridged surface. The surface ridges induce a rapid parametric forcing of the vortex filament, and alter the filament dynamics significantly. A consideration of the contribution of vortex filament induced flow to energy transport indicates that the behavior of the filament induced by the ridges can directly reduce surface drag by up to 8%. The size, shape, and distribution of cutaneous ridges for Tursiops Truncatus is found to be optimally configured to affect the filament dynamics and reduce surface drag for swimming velocities consistent with observation.

  17. Suction and Blowing Flow Control on Airfoil for Drag Reduction in Subsonic Flow

    Science.gov (United States)

    Baljit, S. S.; Saad, M. R.; Nasib, A. Z.; Sani, A.; Rahman, M. R. A.; Idris, A. C.

    2017-10-01

    Lift force is produced from a pressure difference between the pressures acting in upper and lower surfaces. Therefore, flow becomes detached from the surface of the airfoil at separation point and form vortices. These vortices affect the aerodynamic performance of the airfoil in term of lift and drag coefficient. Therefore, this study is investigating the effect of suction and jet blowing in boundary layer separation control on NACA 0012 airfoil in a subsonic wind tunnel. The experiment examined both methods at the position of 25% of the chord-length of the airfoil at Reynolds number 1.2 × 105. The findings show that suction and jet blowing affect the aerodynamic performance of NACA 0012 airfoil and can be an effective means for boundary layer separation control in subsonic flow.

  18. Shortfin Mako Skin: A Possible Passive Flow Control Mechanism for Drag Reduction

    Science.gov (United States)

    Wheelus, Jennifer; Lang, Amy; Bradshaw, Michael; Motta, Phillip; Habegger, Maria

    2013-11-01

    The shortfin mako is one of the fastest and most agile ocean predators creating the need to minimize its pressure drag by controlling flow separation. One proposed method for flow control is the activation of small teeth-like denticles, on the order of 0.2 mm, that cover the skin of the shark. Biological studies of the shortfin mako skin have shown the passive bristling angle of their denticles to exceed 50 degrees in areas on the flank corresponding to the locations likely to experience separation first. It is proposed that reversing flow, as occurs at the onset of separation in a turbulent boundary layer, would activate denticle bristling and hinder local separation from leading to global separation over the shark. It has been shown on a biomimetic model that bristled denticles create cavities that support the formation of vortices that interact with the boundary layer. This interaction is thought to support momentum exchange and allow the flow to stay attached longer. This experiment focuses on the mechanism that triggers bristling of the real shark skin denticles and further explores the interaction those denticles foster with the boundary layer on a 3D biomimetic model using Digital Particle Image Velocimetry (DPIV). Support for this research by the NSF GRFP is gratefully acknowledged.

  19. Direct numerical simulations of drag reduction in turbulent channel flow over bio-inspired herringbone riblet-texture

    NARCIS (Netherlands)

    Benschop, H.O.G.; Westerweel, J.; Breugem, W.P.

    2015-01-01

    The use of drag reducing surface textures is a promising passive method to reduce fuel consumption. Probably most wellknown is the utilisation of shark-skin inspired ridges or riblets parallel to the mean flow. They can reduce drag up to 10%. Recently another bio-inspired texture based on bird

  20. A computational study of drag reduction and vortex shedding suppression of flow past a square cylinder in presence of small control cylinders

    Directory of Open Access Journals (Sweden)

    Shams-Ul. Islam

    2017-04-01

    Full Text Available This article presents a two-dimensional numerical study of the unsteady laminar flow from a square cylinder in presence of multiple small control cylinders. The cylinders are placed in an unconfined medium at low Reynolds numbers (Re = 100 and 160. Different flow phenomena are captured for the gap spacings (g = s/D, where s is the surface-to-surface distance between the main cylinder and small control cylinders and D is the size of the main cylinder between 0.25 – 3 and angle of attack (θ ranging from 300 to 1800. Numerical calculations are performed by using a lattice Boltzmann method. In this paper, the important flow physics of different observed flow patterns in terms of instantaneous vorticity contours visualization, time-trace analysis of drag and lift coefficients and power spectra analysis of lift coefficient are presented and discussed. Drag reduction and suppression of vortex shedding is also discussed in detail and compared with the available experimental and numerical results qualitatively as well as quantitatively. In addition, the mean drag coefficient, Strouhal number, root-mean-square values of the drag and lift coefficients are determined and compared with a single square cylinder without small control cylinders. We found that the drag is reduced 99.8% and 97.6% for (θ, g = (300, 3 at Re = 100 and 160, respectively.

  1. Net radiative forcing and air quality responses to regional CO emission reductions

    Directory of Open Access Journals (Sweden)

    M. M. Fry

    2013-05-01

    Full Text Available Carbon monoxide (CO emissions influence global and regional air quality and global climate change by affecting atmospheric oxidants and secondary species. We simulate the influence of halving anthropogenic CO emissions globally and individually from 10 regions on surface and tropospheric ozone, methane, and aerosol concentrations using a global chemical transport model (MOZART-4 for the year 2005. Net radiative forcing (RF is then estimated using the GFDL (Geophysical Fluid Dynamics Laboratory standalone radiative transfer model. We estimate that halving global CO emissions decreases global annual average concentrations of surface ozone by 0.45 ppbv, tropospheric methane by 73 ppbv, and global annual net RF by 36.1 mW m−2, nearly equal to the sum of changes from the 10 regional reductions. Global annual net RF per unit change in emissions and the 100 yr global warming potential (GWP100 are estimated as −0.124 mW m−2 (Tg CO−1 and 1.34, respectively, for the global CO reduction, and ranging from −0.115 to −0.131 mW m−2 (Tg CO−1 and 1.26 to 1.44 across 10 regions, with the greatest sensitivities for regions in the tropics. The net RF distributions show widespread cooling corresponding to the O3 and CH4 decreases, and localized positive and negative net RFs due to changes in aerosols. The strongest annual net RF impacts occur within the tropics (28° S–28° N followed by the northern midlatitudes (28° N–60° N, independent of reduction region, while the greatest changes in surface CO and ozone concentrations occur within the reduction region. Some regional reductions strongly influence the air quality in other regions, such as East Asia, which has an impact on US surface ozone that is 93% of that from North America. Changes in the transport of CO and downwind ozone production clearly exceed the direct export of ozone from each reduction region. The small variation in CO GWPs among world regions suggests that future international

  2. Chloroplastic and stomatal aspects of ozone-induced reduction of net photosynthesis in plants

    Energy Technology Data Exchange (ETDEWEB)

    Torsethaugen, Gro

    1998-09-01

    The present thesis relates to ozone-induced reduction of photosynthesis in plants. As a photochemical oxidant O{sub 3} is formed by the interaction of hydrocarbons, nitrogen oxides and oxygen in sunlight. Ozone (O{sub 3}) is the most phytotoxic of all the air pollutants and is known to reduce plant growth and net photosynthesis, cause stomatal closure, induce visible injury, accelerate senescence and induce or inhibit transcription of a variety of genes with a corresponding increase/decrease in protein products. The underlying cellular mechanisms for many of these changes are unknown. Following fields are investigated: Ozone-induced reduction of net photosynthesis; ozone and the photosynthetic apparatus in the chloroplasts; ozone and stomata; ozone effects on plant membranes; protection against ozone injury in plants. 249 refs., 22 figs., 4 tabs.

  3. Fine sediment transport into the hyperturbid lower Ems River : The role of channel deepening and sediment-induced drag reduction

    NARCIS (Netherlands)

    Van Maren, D.S.; Winterwerp, J.C.; Vroom, J.

    2015-01-01

    Deepening of estuarine tidal channels often leads to tidal amplification and increasing fine sediment import. Increasing fine sediment import, in turn, may lower the hydraulic drag (due to a smoother muddy bed and/or sediment-induced damping of turbulence), and therefore, further strengthen tidal

  4. Studies on fluid drag measurement and fluid drag reduction of woman athlete swimming suit; Kyoeiyo mizugi no teiko sokutei ni kansuru kenkyu. Jintai mokei oyobi mizugi no ryutai teiko

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Y. [Mie University, Mie (Japan). Faculty of Engineering; Suzuki, T.; Suzuki, K. [Mie University, Mie (Japan); Kiyokawa, H. [Mizuno Corp., Osaka (Japan)

    1997-12-25

    Sport science progresses step by step in the world. This work is a challenge to develop the athlete woman swimming suit with low fluid drag. To begin with, the fluid drag of the woman swimming suit is very small. It is very difficult to measure the several percent difference in the fluid drag of the swimming suit. Special experimental apparatus is developed to measure the fluid drag, precisely. It can successfully measure the fluid drag of athlete woman swimming suits at the precision 1-2%. As a result, the cloth with low fluid drag is found. It is worked water repellent into every other stripe on the cloth. The cloth is woven of thin threads (polyester 80% and polyurethane 20%). Also, the relationship between fluid drag for the model body and the water depth from the water surface to the model body is investigated in details. 2 refs., 16 figs.

  5. Quantifying the net social benefits of vehicle trip reductions : guidance for customizing the TRIMMS(c) model.

    Science.gov (United States)

    2009-04-01

    This study details the development of a series of enhancements to the Trip Reduction Impacts of : Mobility Management Strategies (TRIMMS) model. TRIMMS allows quantifying the net social : benefits of a wide range of transportation demand management...

  6. Can Switching from Coal to Shale Gas Bring Net Carbon Reductions to China?

    Science.gov (United States)

    Qin, Yue; Edwards, Ryan; Tong, Fan; Mauzerall, Denise L

    2017-03-07

    To increase energy security and reduce emissions of air pollutants and CO2 from coal use, China is attempting to duplicate the rapid development of shale gas that has taken place in the United States. This work builds a framework to estimate the lifecycle greenhouse gas (GHG) emissions from China's shale gas system and compares them with GHG emissions from coal used in the power, residential, and industrial sectors. We find the mean lifecycle carbon footprint of shale gas is about 30-50% lower than that of coal in all sectors under both 20 year and 100 year global warming potentials (GWP20 and GWP100). However, primarily due to large uncertainties in methane leakage, the upper bound estimate of the lifecycle carbon footprint of shale gas in China could be approximately 15-60% higher than that of coal across sectors under GWP20. To ensure net GHG emission reductions when switching from coal to shale gas, we estimate the breakeven methane leakage rates to be approximately 6.0%, 7.7%, and 4.2% in the power, residential, and industrial sectors, respectively, under GWP20. We find shale gas in China has a good chance of delivering air quality and climate cobenefits, particularly when used in the residential sector, with proper methane leakage control.

  7. Coupled Vortex-Lattice Flight Dynamic Model with Aeroelastic Finite-Element Model of Flexible Wing Transport Aircraft with Variable Camber Continuous Trailing Edge Flap for Drag Reduction

    Science.gov (United States)

    Nguyen, Nhan; Ting, Eric; Nguyen, Daniel; Dao, Tung; Trinh, Khanh

    2013-01-01

    This paper presents a coupled vortex-lattice flight dynamic model with an aeroelastic finite-element model to predict dynamic characteristics of a flexible wing transport aircraft. The aircraft model is based on NASA Generic Transport Model (GTM) with representative mass and stiffness properties to achieve a wing tip deflection about twice that of a conventional transport aircraft (10% versus 5%). This flexible wing transport aircraft is referred to as an Elastically Shaped Aircraft Concept (ESAC) which is equipped with a Variable Camber Continuous Trailing Edge Flap (VCCTEF) system for active wing shaping control for drag reduction. A vortex-lattice aerodynamic model of the ESAC is developed and is coupled with an aeroelastic finite-element model via an automated geometry modeler. This coupled model is used to compute static and dynamic aeroelastic solutions. The deflection information from the finite-element model and the vortex-lattice model is used to compute unsteady contributions to the aerodynamic force and moment coefficients. A coupled aeroelastic-longitudinal flight dynamic model is developed by coupling the finite-element model with the rigid-body flight dynamic model of the GTM.

  8. Carbon emission reductions by substitution of improved cookstoves and cattle mosquito nets in a forest-dependent community

    Directory of Open Access Journals (Sweden)

    Somanta Chan

    2015-07-01

    Substitution of conventional cookstoves with improved cookstoves and the use of mosquito nets instead of fuelwood burning could result in using less fuelwood for the same amount of energy needed and thereby result in reduction of carbon emissions and deforestation. To realize this substitution, approximately US$ 15–25 MgCO2−1 is needed depending on discount rates and amounts of emission reduction. Substitution of cookstoves will have direct impacts on the livelihoods of forest-dependent communities and on forest protection. Financial incentives under voluntary and mandatory schemes are needed to materialize this substitution.

  9. Studies on reduction of fluid drag for athlete swimming suit by boundary layer control; Kyoeiyo mizugi ni kansuru kenkyu (kyokaiso seigyo ni yoru mizugi teiko no sakugen ni tsuite)

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Y. [Mie University, Mie (Japan). Faculty of Engineering; Suzuki, T. [Mie University, Mie (Japan); Mori, K. [Mizuno Corp., Osaka (Japan)

    1998-09-25

    Sport science progresses step by step in the world. The paper describes, the first, the relationships between fluid drag for a model of woman swimmer and the flow around it. The flow around the model swimmer is very complicated, and includes, for example, wave, some kinds of vortices, hydraulic jumping and so on. The complicated flows are visualized by the surface tufts method and so on. Second, the possibility of the reduction of fluid drag for a woman athlete swimming suit is challenged. The boundary layer control is applied to reduce the fluid drag. The separation occurs around the breast of a woman swimmer. The separation can be suppressed by the boundary layer control. Many beads are distributed on the breast area of a woman swimming suit. As the result, it is found that the fluid drag for the model swimmer can be reduced in a range of 1.5%--2% by the suit with the boundary layer control, which is carried out by many beads. 2 refs., 12 figs., 3 tabs.

  10. Aircraft Drag Prediction and Reduction

    Science.gov (United States)

    1985-07-01

    that propagate down the wing leading edge along the attachment line. This type of instability can be controlled by proper treatment of the inboard...Advances in Applied Mechanics, %ol. 19. Edited by .hia-Shun Vih , Academic Press, 1979. 29. Coherent Structure of Turbulent Boundary Layers. Editors, C...may therefore be used to estimate it. Although the treatment is mainly restricted to flows in which the boundary layers remain attached over most of

  11. 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

  12. FY2003 Annual Report: DOE Project on Heavy Vehicle Aerodynamic Drag

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-10-24

    Objective: {sm_bullet} Provide guidance to industry in the reduction of aerodynamic drag of heavy truck vehicles. {sm_bullet} Establish a database of experimental, computational, and conceptual design information, and demonstrate potential of new drag-reduction devices.

  13. 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.

  14. Flicking-wire drag tensioner

    Science.gov (United States)

    Dassele, M. A.; Fairall, H.

    1978-01-01

    Wire-drag system improves wire profile and applies consistent drag to wire. Wire drag is continuously adjustable from zero drag to tensile strength of wire. No-sag wire drag is easier to thread than former system and requires minimal downtime for cleaning and maintenance.

  15. Some comments on trim drag

    Science.gov (United States)

    Roskam, J.

    1975-01-01

    A discussion of data of and methods for predicting trim drag is presented. Specifically the following subjects are discussed: (1) economic impact of trim drag; (2) the trim drag problem in propeller driven airplanes and the effect of propeller and nacelle location; (3) theoretical procedures for predicting trim drag; and (4) research needs in the area of trim drag.

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

    Directory of Open Access Journals (Sweden)

    Matthias Bauer

    2016-10-01

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

  17. Some comments on fuselage drag

    Science.gov (United States)

    Roskam, J.

    1975-01-01

    The following areas relating to fuselage drag are considered: (1) fuselage fineness - ratio and why and how this can be selected during preliminary design; (2) windshield drag; (3) skin roughness; and (4) research needs in the area of fuselage drag.

  18. Impact of the Microstructure of Polymer Drag Reducer on Slick-Water Fracturing

    Directory of Open Access Journals (Sweden)

    Zhi-yu Liu

    2017-01-01

    Full Text Available Many studies have focused on the drag reduction performance of slick-water, but the microdrag reduction mechanism remains unclear since the microstructure of the drag reducer and its effect on this mechanism have not been well studied. In this study, the microstructure of the drag reducer in slick-water was effectively characterized by transmission electron microscopy. The viscoelasticity and drag reduction performance of the drag reducer with different microstructures were then investigated. Further, the effects of the microstructure of the drag reducer on the viscoelasticity and drag reduction performance of slick-water were analyzed. The results demonstrated that the viscoelasticity of slick-water is governed by the microstructure of the drag reducer, which exhibits a network structure. In addition, the drag reduction performance is related to the viscoelasticity. At low flow rates, the drag reduction performance is dominantly influenced by viscosity, whereas, at high flow rates, it is governed mainly by elasticity. Furthermore, the drag reducer with a uniformly distributed network structure exhibits the most stable drag reduction performance. This drag reducer was used in a field test and the obtained results were consistent with those of a laboratory experiment.

  19. Reconfiguration parameters for drag of flexible cylindrical elements

    Science.gov (United States)

    John, Chapman; Wilson, Bruce; Gulliver, John

    2015-11-01

    This presentation compares parameters that characterize reconfiguration effects on flow resistance and drag. The drag forces occurring on flexible bluff bodies are different from the drag occurring on rigid bluff bodies due to reconfiguration. Drag force data, collected using a torque sensor in a flume, for simple cylindrical obstructions of the same shape and size but with different flexibility is used to fit drag parameters. The key parameter evaluated is a reference velocity factor u to account for drag reduction due to reconfiguration, similar to a Vogel exponent. Our equations preserves the traditional exponent of the drag relationship, but places a factor onto the drag coefficient for flexible elements, rather than a Vogel exponent arrangement applied to the flow velocity. Additionally we relate the reference velocity factor u to the modulus of elasticity of the material through the Cauchy Number. The use of a reference velocity factor u in place of a Vogel exponent appears viable to account for how the drag forces are altered by reconfiguration. The proposed formulation for drag reduction is more consistently estimated for the range of flexibilities in this study. Unfortunately, the mechanical properties of vegetation are not often readily available for reconfiguration relationships to the elastic modulus of vegetation to be of immediate practical use.

  20. The impact of reduction of doublet well spacing on the Net Present Value and the life time of fluvial Hot Sedimentary Aquifer doublets

    DEFF Research Database (Denmark)

    Willems, C. J. L.; Nick, H. M.; Goense, T.

    2017-01-01

    This paper evaluates the impact of reduction of doublet well spacing, below the current West Netherlands Basin standard of 1000 - 1500 m, on the Net Present Value (NPV) and the life time of fluvial Hot Sedimentary Aquifer (HSA) doublets. First, a sensitivity analysis is used to show the possible ...

  1. The impact of reduction of doublet well spacing on the Net Present Value and the life time of fluvial Hot Sedimentary Aquifer doublets

    NARCIS (Netherlands)

    Willems, C.J.L.; Maghami Nick, Hamidreza M.; Bruhn, D.F.

    This paper evaluates the impact of reduction of doublet well spacing, below the current West Netherlands Basin standard of 1000 to 1500 m, on the Net Present Value (NPV) and the life time of fluvial Hot Sedimentary Aquifer (HSA) doublets. First, a sensitivity analysis is used to show the possible

  2. Hydrodynamic Drag on Streamlined Projectiles and Cavities

    KAUST Repository

    Jetly, Aditya

    2016-04-19

    The air cavity formation resulting from the water-entry of solid objects has been the subject of extensive research due to its application in various fields such as biology, marine vehicles, sports and oil and gas industries. Recently we demonstrated that at certain conditions following the closing of the air cavity formed by the initial impact of a superhydrophobic sphere on a free water surface a stable streamlined shape air cavity can remain attached to the sphere. The formation of superhydrophobic sphere and attached air cavity reaches a steady state during the free fall. In this thesis we further explore this novel phenomenon to quantify the drag on streamlined shape cavities. The drag on the sphere-cavity formation is then compared with the drag on solid projectile which were designed to have self-similar shape to that of the cavity. The solid projectiles of adjustable weight were produced using 3D printing technique. In a set of experiments on the free fall of projectile we determined the variation of projectiles drag coefficient as a function of the projectiles length to diameter ratio and the projectiles specific weight, covering a range of intermediate Reynolds number, Re ~ 104 – 105 which are characteristic for our streamlined cavity experiments. Parallel free fall experiment with sphere attached streamlined air cavity and projectile of the same shape and effective weight clearly demonstrated the drag reduction effect due to the stress-free boundary condition at cavity liquid interface. The streamlined cavity experiments can be used as the upper bound estimate of the drag reduction by air layers naturally sustained on superhydrophobic surfaces in contact with water. In the final part of the thesis we design an experiment to test the drag reduction capacity of robust superhydrophobic coatings deposited on the surface of various model vessels.

  3. Modeling the Metabolism of Arabidopsis thaliana: Application of Network Decomposition and Network Reduction in the Context of Petri Nets.

    Science.gov (United States)

    Koch, Ina; Nöthen, Joachim; Schleiff, Enrico

    2017-01-01

    Motivation:Arabidopsis thaliana is a well-established model system for the analysis of the basic physiological and metabolic pathways of plants. Nevertheless, the system is not yet fully understood, although many mechanisms are described, and information for many processes exists. However, the combination and interpretation of the large amount of biological data remain a big challenge, not only because data sets for metabolic paths are still incomplete. Moreover, they are often inconsistent, because they are coming from different experiments of various scales, regarding, for example, accuracy and/or significance. Here, theoretical modeling is powerful to formulate hypotheses for pathways and the dynamics of the metabolism, even if the biological data are incomplete. To develop reliable mathematical models they have to be proven for consistency. This is still a challenging task because many verification techniques fail already for middle-sized models. Consequently, new methods, like decomposition methods or reduction approaches, are developed to circumvent this problem. Methods: We present a new semi-quantitative mathematical model of the metabolism of Arabidopsis thaliana. We used the Petri net formalism to express the complex reaction system in a mathematically unique manner. To verify the model for correctness and consistency we applied concepts of network decomposition and network reduction such as transition invariants, common transition pairs, and invariant transition pairs. Results: We formulated the core metabolism of Arabidopsis thaliana based on recent knowledge from literature, including the Calvin cycle, glycolysis and citric acid cycle, glyoxylate cycle, urea cycle, sucrose synthesis, and the starch metabolism. By applying network decomposition and reduction techniques at steady-state conditions, we suggest a straightforward mathematical modeling process. We demonstrate that potential steady-state pathways exist, which provide the fixed carbon to nearly

  4. Modeling the Metabolism of Arabidopsis thaliana: Application of Network Decomposition and Network Reduction in the Context of Petri Nets

    Directory of Open Access Journals (Sweden)

    Ina Koch

    2017-06-01

    Full Text Available Motivation:Arabidopsis thaliana is a well-established model system for the analysis of the basic physiological and metabolic pathways of plants. Nevertheless, the system is not yet fully understood, although many mechanisms are described, and information for many processes exists. However, the combination and interpretation of the large amount of biological data remain a big challenge, not only because data sets for metabolic paths are still incomplete. Moreover, they are often inconsistent, because they are coming from different experiments of various scales, regarding, for example, accuracy and/or significance. Here, theoretical modeling is powerful to formulate hypotheses for pathways and the dynamics of the metabolism, even if the biological data are incomplete. To develop reliable mathematical models they have to be proven for consistency. This is still a challenging task because many verification techniques fail already for middle-sized models. Consequently, new methods, like decomposition methods or reduction approaches, are developed to circumvent this problem.Methods: We present a new semi-quantitative mathematical model of the metabolism of Arabidopsis thaliana. We used the Petri net formalism to express the complex reaction system in a mathematically unique manner. To verify the model for correctness and consistency we applied concepts of network decomposition and network reduction such as transition invariants, common transition pairs, and invariant transition pairs.Results: We formulated the core metabolism of Arabidopsis thaliana based on recent knowledge from literature, including the Calvin cycle, glycolysis and citric acid cycle, glyoxylate cycle, urea cycle, sucrose synthesis, and the starch metabolism. By applying network decomposition and reduction techniques at steady-state conditions, we suggest a straightforward mathematical modeling process. We demonstrate that potential steady-state pathways exist, which provide the

  5. That's a Drag: The Effects of Drag Forces

    Directory of Open Access Journals (Sweden)

    Shane Maxemow

    2009-01-01

    Full Text Available Drag is a force that opposes motion due to an object's shape, material, and speed. This project defined what drag force is, derived the governing equation for drag and listed some applications of drag forces. Derivation of the drag equation was achieved using the Buckingham π theorem, a dimensional analysis tool. Lastly, this project explored the problem of how long and how far a dragster takes to stop once its parachute is deployed.

  6. Drag Reducing and Cavitation Resistant Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Pease, Leonard F.

    2016-12-28

    Client, Green Building Systems (GBS), presented PNNL a coating reported to reduce drag and prevent cavitation damage on marine vessels, turbines and pumps. The composition of the coating remains proprietary but has as constituents including silicon oxides, aliphatic carbon chains, and fluorine rich particles. The coating is spray applied to surfaces. Prior GBS testing and experiments suggest reduction of both drag and cavitation on industrial scale propellers, but the underlying mechanism for these effects remains unclear. Yet, the application is compelling because even modest reductions in drag to marine vessels and cavitation to propellers and turbines present a significant economic and environmental opportunity. To discern among possible mechanisms, PNNL considered possible mechanisms with the client, executed multiple experiments, and completed one theoretical analysis (see appendix). The remainder of this report first considers image analysis to gain insight into drag reduction mechanisms and then exposes the coating to cavitation to explore its response to an intensely cavitating environment. Although further efforts may be warranted to confirm mechanisms, this report presents a first investigation into these coatings within the scope and resources of the technology assistance program (TAP).

  7. Rotating cylinder drag balance with application to riblets

    Energy Technology Data Exchange (ETDEWEB)

    Hall, T.; Joseph, D. [Minnesota Univ., Minneapolis, MN (United States). Dept. of Aerospace Engineering and Mechanics

    2000-09-01

    Experimental results are reported and discussed for a rotating cylinder drag balance designed to predict drag reduction by surfaces like riblets. The apparatus functions by measuring the torque applied to the inner cylinder by a fluid, such as water, that is set in motion by the controlled rotation of the outer cylinder. The instrument was validated by calibration for laminar flow and comparison of turbulent flow results to the those of G. I. Taylor. The ability to predict drag reduction was demonstrated by testing 114 m symmetric sawtooth riblets, which gave a maximum reduction of about 5% and an overall drag reduction range of 5

  8. Experiment Evaluation of Skin Friction Drag by Surface Tailoring

    Science.gov (United States)

    Manigandan, S.; Gopal krishna, K.; Gagan Kumar, K.; Gunasekar, P.; Nithya, S.

    2017-08-01

    Reduction of drag is an important role of aerodynamic specialist in real time world. The performance of forward moving object improved when the drag is reduced. Skin friction drag caused when the fluid tending to shear along the surface of the body and it is dependent on energy expenditure. Initial research concluded that nearly 20 to 40% of total drag is skin friction drag, based on flight forward velocity. This means a lot of fuel burned. In this paper we investigate a methodology to reduce the skin friction drag by implementing different kinds of exterior treatments. The ideology inspired from the world fastest moving oceanic creature. Structures are fabricated based on the replica of scales of the oceanic creature. The outer skin of the aerofoil NACA0012 is modified like shark scales. Then it is tested using open type sub sonic wind tunnel. In addition to that, the leading edge thickness effect also studied. The turbulent flow phenomenon is validated at different velocities and compared with numerical results using STAR CCM+. From the plots and graphical results, it is found that the skin friction drag is generated less due to reduction of transverse shear stress present in turbulent flow and skin friction drag depends on boundary layer thickness and on the percentage of chord of flow separation. In addition to this, the result delivers that the ordinary polished surface produces more drag than the modified scales. The outlook of this technology is excrescence for different applications. This open section wind tunnel testing produces 10-15% reduction in drag and can be turn to high values when the experiment is conducted in closed section wind tunnel with real time atmospheric conditions, which can be done as a future work.

  9. Dragging of inertial frames.

    Science.gov (United States)

    Ciufolini, Ignazio

    2007-09-06

    The origin of inertia has intrigued scientists and philosophers for centuries. Inertial frames of reference permeate our daily life. The inertial and centrifugal forces, such as the pull and push that we feel when our vehicle accelerates, brakes and turns, arise because of changes in velocity relative to uniformly moving inertial frames. A classical interpretation ascribed these forces to acceleration relative to some absolute frame independent of the cosmological matter, whereas an opposite view related them to acceleration relative to all the masses and 'fixed stars' in the Universe. An echo and partial realization of the latter idea can be found in Einstein's general theory of relativity, which predicts that a spinning mass will 'drag' inertial frames along with it. Here I review the recent measurements of frame dragging using satellites orbiting Earth.

  10. Experimental study on the wall jet over a riblet surface. ; Measurement of mean and fluctuating velocities and estimation of drag reduction. Riburetto men ni sou hekimen funryu ni kansuru jikkenteki kenkyu. ; Heikin-hendo sokudoba to teiko gensho no hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Yamashita, S. (Gifu Univ., Gifu (Japan). Faculty of Engineering); Hayashimoto, H. (Gifu Univ., Gifu (Japan). Graduate School); Inoue, Y. (Suzuka National College of Technology, Mie (Japan)); Iwakami, Y.

    1994-04-25

    A wall-jet has a wide range of application such as to control of the boundary layer of a wing of an aeroplane, control of temperature of the vanes of a gas turbine and flow inside a fluid control device. This field of flow comprises a wall layer on the wall side having the characteristics of a boundary layer and an outer layer on the external side which is like a free jet, the two layers being separated by a boundary where the flow is at a maximum speed. This study was carried out to clarify the effect of riblets experimentally using as a base jet a wall jet which was one of basic shearing flows. In particular, studied were the degrees of change in the mean and fluctuating velocities near the wall surface and reduction of drag. The following results were obtained. A significant difference was recognized in the vicinity of the wall in the mean velocity distribution between the mean velocities on the riblet surface and on the smooth surface. The fluctuating velocity component in the x direction on the riblet surface decreased by about a maximum of 20% when compared with that on the smooth surface. In contrast, the fluctuating velocity in the y direction and Reynolds shearing stress both on the riblet and smooth surfaces were substantially in agreement with each other within the range of this experiment. 28 refs., 12 figs., 1 tab.

  11. Drag of a D-shaped bluff body under small amplitude harmonic actuation

    Directory of Open Access Journals (Sweden)

    Yaqing Li

    2015-01-01

    Full Text Available Open-loop flow control method was used to affect the development of a turbulent wake behind a D-shaped bluff body. Loud speakers were embedded inside the bluff body to produce two zero-net-mass-flux jets through 2 mm-wide span-wise slots located along the upper and lower edges on the rear wall. The drag forces for different actuation amplitudes (Cμ, the ratio between the momentum of the actuating jets and the moment deficit caused by the bluff body and frequencies (StA were examined. The effects of the phase difference in the two jets (0 and π were also studied. It was found that when Cμ was 0.1%, a drag reduction up to 5% was achieved when the velocities of the two jets varied in phase at a frequency of StA=0.16. When the velocities of the two jets varied π out of phase, significant drag increase was observed.

  12. A Study of Drag Force in Isothermal Bubbly Flow

    Directory of Open Access Journals (Sweden)

    C. Li

    2009-12-01

    Full Text Available Driven by the extensive demands of simulating highly concentrated gas bubbly flows in many engineering fields, numerical studies have been performed to investigate the neighbouring effect of a swarm of bubbles on the interfacial drag forces. In this study, a novel drag coefficient correlation (Simonnet et al., 2007 in terms of local void fraction coupled with the population balance model based on average bubble number density (ABND has been implemented and compared with Ishii-Zuber densely distributed fluid particles drag model. The predicted local radial distributions of three primitive variables: gas void fraction, Sauter mean bubble diameter, and gas velocity, are validated against the experimental data of Hibiki et al. (2001. In general, satisfactory agreements between predicted and measured results are achieved by both drag force models. With additional consideration for closely packed bubbles, the latest coefficient model by Simonnet et al. (2007 shows considerably better performance in capturing the reduction of drag forces incurred by neighbouring bubbles.

  13. Near-Net-Shape Production of Hollow Titanium Alloy Components via Electrochemical Reduction of Metal Oxide Precursors in Molten Salts

    Science.gov (United States)

    Hu, Di; Xiao, Wei; Chen, George Z.

    2013-04-01

    Metal oxide precursors (ca. 90 wt pct Ti, 6 wt pct Al, and 4 wt pct V) were prepared with a hollow structure in various shapes such as a sphere, miniature golf club head, and cup using a one-step solid slip-casting process. The precursors were then electro-deoxidized in molten calcium chloride [3.2 V, 1173 K (900 °C)] against a graphite anode. After 24 hours of electrolysis, the near-net-shape Ti-6Al-4V product maintained its original shape with controlled shrinkage. Oxygen contents in the Ti-6Al-4V components were typically below 2000 ppm. The maximum compressive stress and modulus of electrolytic products obtained in this work were approximately 243 MPa and 14 GPa, respectively, matching with the requirement for medical implants. Further research directions are discussed for mechanical improvement of the products via densification during or after electrolysis. This simple, fast, and energy-efficient near-net-shape manufacturing method could allow titanium alloy components with desired geometries to be prepared directly from a mixture of metal oxides, promising an innovative technology for the low-cost production of titanium alloy components.

  14. Reduction of net primary productivity in southern China caused by abnormal low-temperature freezing in winter of 2008 detected by a remote sensing-driven ecosystem model

    Science.gov (United States)

    Ju, W.; Liu, Y.; Zhou, Y.; Zhu, G.

    2011-12-01

    Terrestrial carbon cycle is an important determinant of global climate change and affected by various factors, including climate, CO2 concentration, atmospheric nitrogen deposition and human activities. Extreme weather events can significantly regulate short-term even long-term carbon exchanges between terrestrial ecosystems and the atmosphere. During the period from the middle January to the middle February 2008, Southern China was seriously hit by abnormal low-temperature freezing, which caused serous damages to forests and crops. However, the reduction of net primary productivity (NPP) of terrestrial ecosystems caused by this extremely abnormal weather event has not been quantitatively investigated. In this study, the Boreal Ecosystem Productivity Simulator (BEPS) model was employed to assess the reduction of NPP in Southern China caused by the abnormal low-temperature freezing. Prior to the regional simulation, the BEPS model was validated using measured NPP in different ecosystems, demonstrating the ability of this model to simulate NPP reliably in China. Then, it was forced using meteorological data interpolated from observations of weather stations and leaf area index inversed from MODIS reflectance data to simulate national wide NPP at a 500 m resolution for the period from 2003 to 2008. The departures of NPP in 2008 from the means during 2003-2007 were used as the indicator of NPP reduction caused by the low-temperature freezing. It was found out that NPP in 2008 decreased significantly in forests of Southern China, especially in Guangdong, Fujian, Zhejiang, Guangxi, Jiangxi, and Hunan Provinces, in which the low-temperature freeing was more serious. The annul reduction of NPP was above 150 g C/m^2/yr in these areas. Key words: Net Primary Productivity, low-temperature freezing, BEPS model, MODIS Correspondence author: Weimin Ju Email:juweimin@nju.edu.cn

  15. Developments in greenhouse gas emissions and net energy use in Danish agriculture - How to achieve substantial CO2 reduction?

    DEFF Research Database (Denmark)

    Dalgaard, Tommy; Olesen, Jørgen E; Petersen, Søren O

    2011-01-01

    emissions in the form of methane, nitrous oxide and carbon dioxide (including carbon sources and sinks, and the impact of energy consumption/bioenergy production) from Danish agriculture in the years 1990–2010. An analysis of possible measures to reduce the GHG emissions indicated that a 50–70% reduction...

  16. Reduction of Net Sulfide Production Rate by Nitrate in Wastewater Bioreactors. Kinetics and Changes in the Microbial Community

    DEFF Research Database (Denmark)

    Villahermosa, Desiree; Corzo, Alfonso; Gonzalez, J M

    2013-01-01

    Nitrate addition stimulated sulfide oxidation by increasing the activity of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB), decreasing the concentration of dissolved H2S in the water phase and, consequently, its release to the atmosphere of a pilot-scale anaerobic bioreactor. The effect...... of four different concentrations of nitrate (0.12, 0.24, 0.50, and 1.00 mM) was investigated for a period of 3 days in relation to sulfide concentration in two bioreactors set up at Guadalete wastewater treatment plant (Jerez de la Frontera, Spain). Physicochemical variables were measured in water and air......, and the activity of bacteria implicated in the sulfur and nitrogen cycles was analyzed in the biofilms and in the water phase of the bioreactors. Biofilms were a net source of sulfide for the water and gas phases (7.22 ± 5.3 μmol s−1) in the absence of nitrate dosing. Addition of nitrate resulted in a quick...

  17. Progress towards a Drag-free SmallSat

    Science.gov (United States)

    Saraf, Shailendhar

    The net force acting on a drag-free satellite is purely gravitational as all other forces, mainly atmospheric drag and solar radiation pressure, are canceled out. In order to achieve this, a free floating reference (test mass) inside the satellite is shielded against all forces but gravity and a system of thrusters is commanded by a control algorithm such that the relative displacement between the reference and the satellite stays constant. The main input to that control algorithm is the output of a sensor which measures the relative displacement between the satellite and the test mass. Internal disturbance forces such as electrostatic or magnetic forces cannot be canceled out his way and have to be minimized by a careful design of the satellite. A drag-free technology package is under development at Stanford since 2004. It includes an optical displacement sensor to measure the relative position of the test mass inside the satellite, a caging mechanism to lock the test mass during launch, a UV LED based charge management system to minimize the effect of electrostatic forces, a thermal enclosure, and the drag-free control algorithms. Possible applications of drag-free satellites in fundamental physics (Gravity Probe B, LISA), geodesy (GOCE), and navigation (TRIAD I). In this presentation we will highlight the progress of the technology development towards a drag-free mission. The planned mission on a SaudiSat bus will demonstrate drag-free technology on a small spacecraft at a fraction of the cost of previous drag-free missions. The target acceleration noise is 10-12 m/sec2. With multiple such satellites a GRACE-like mission with improved sensitivity and potentially improved spatial and temporal resolution can be achieved.

  18. Aerodynamic drag on intermodal railcars

    Science.gov (United States)

    Kinghorn, Philip; Maynes, Daniel

    2014-11-01

    The aerodynamic drag associated with transport of commodities by rail is becoming increasingly important as the cost of diesel fuel increases. This study aims to increase the efficiency of intermodal cargo trains by reducing the aerodynamic drag on the load carrying cars. For intermodal railcars a significant amount of aerodynamic drag is a result of the large distance between loads that often occurs and the resulting pressure drag resulting from the separated flow. In the present study aerodynamic drag data have been obtained through wind tunnel testing on 1/29 scale models to understand the savings that may be realized by judicious modification to the size of the intermodal containers. The experiments were performed in the BYU low speed wind tunnel and the test track utilizes two leading locomotives followed by a set of five articulated well cars with double stacked containers. The drag on a representative mid-train car is measured using an isolated load cell balance and the wind tunnel speed is varied from 20 to 100 mph. We characterize the effect that the gap distance between the containers and the container size has on the aerodynamic drag of this representative rail car and investigate methods to reduce the gap distance.

  19. The effect of netting solidity ratio and inclined angle on the hydrodynamic characteristics of knotless polyethylene netting

    Science.gov (United States)

    Tang, Hao; Hu, Fuxiang; Xu, Liuxiong; Dong, Shuchuang; Zhou, Cheng; Wang, Xuefang

    2017-10-01

    Knotless polyethylene (PE) netting has been widely used in aquaculture cages and fishing gears, especially in Japan. In this study, the hydrodynamic coefficient of six knotless PE netting panels with different solidity ratios were assessed in a flume tank under various attack angles of netting from 0° (parallel to flow) to 90° (perpendicular to flow) and current speeds from 40 cm s-1 to 130 cm s-1. It was found that the drag coefficient was related to Reynolds number, solidity ratio and attack angle of netting. The solidity ratio was positively related with drag coefficient for netting panel perpendicular to flow, whereas when setting the netting panel parallel to the flow the opposite result was obtained. For netting panels placed at an angle to the flow, the lift coefficient reached the maximum at an attack angle of 50° and then decreased as the attack angle further increased. The solidity ratio had a dual influence on drag coefficient of inclined netting panels. Compared to result in the literature, the normal drag coefficient of knotless PE netting measured in this study is larger than that of nylon netting or Dyneema netting.

  20. When superfluids are a drag

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, David C [Los Alamos National Laboratory

    2008-01-01

    The article considers the dramatic phenomenon of seemingly frictionless flow of slow-moving superfluids. Specifically the question of whether an object in a superfluid flow experiences any drag force is addressed. A brief account is given of the history of this problem and it is argued that recent advances in ultracold atomic physics can shed much new light on this problem. The article presents the commonly held notion that sufficiently slow-moving superfluids can flow without drag and also discusses research suggesting that scattering quantum fluctuations might cause drag in a superfluid moving at any speed.

  1. Coulomb drag in quantum circuits.

    Science.gov (United States)

    Levchenko, Alex; Kamenev, Alex

    2008-11-21

    We study the drag effect in a system of two electrically isolated quantum point contacts, coupled by Coulomb interactions. Drag current exhibits maxima as a function of quantum point contacts gate voltages when the latter are tuned to the transitions between quantized conductance plateaus. In the linear regime this behavior is due to enhanced electron-hole asymmetry near an opening of a new conductance channel. In the nonlinear regime the drag current is proportional to the shot noise of the driving circuit, suggesting that the Coulomb drag experiments may be a convenient way to measure the quantum shot noise. Remarkably, the transition to the nonlinear regime may occur at driving voltages substantially smaller than the temperature.

  2. Boundary layer thickness effect on boattail drag

    Science.gov (United States)

    Blaha, B. J.; Chamberlain, R.; Bober, L. J.

    1976-01-01

    A combined experimental and analytical program was conducted to investigate the effects of boundary layer changes on the flow over high angle boattail nozzles. The tests were run on an isolated axisymmetric sting mounted model. Various boattail geometries were investigated at high subsonic speeds over a range of boundary layer thicknesses. In general, boundary layer effects were small at speeds up to Mach 0.8. However, at higher speeds significant regions of separated flow were present on the boattail. When separation was present large reductions in boattail drag resulted with increasing boundary layer thickness. The analysis predicts both of these trends.

  3. Comparing biofouling control treatments for use on aquaculture nets.

    Science.gov (United States)

    Swain, Geoffrey; Shinjo, Nagahiko

    2014-12-02

    Test panels comprised of uncoated, copper coated and silicone coated 7/8'' (22 mm) mesh knitted nylon net were evaluated to compare their properties and the effectiveness to prevent biofouling. This paper describes test procedures that were developed to quantify the performance in terms of antifouling, cleanability, drag and cost. The copper treatment was the most effective at controlling fouling, however, the silicone treated nets were the easiest to clean. The drag forces on the net were a function of twine diameter, twine roughness and fouling. After immersion, the uncoated nets had the most drag followed by the silicone and copper treatments. The cost of applying silicone to nets is high; however, improved formulations may provide a non-toxic alternative to control fouling.

  4. Comparing Biofouling Control Treatments for Use on Aquaculture Nets

    Directory of Open Access Journals (Sweden)

    Geoffrey Swain

    2014-12-01

    Full Text Available Test panels comprised of uncoated, copper coated and silicone coated 7/8'' (22 mm mesh knitted nylon net were evaluated to compare their properties and the effectiveness to prevent biofouling. This paper describes test procedures that were developed to quantify the performance in terms of antifouling, cleanability, drag and cost. The copper treatment was the most effective at controlling fouling, however, the silicone treated nets were the easiest to clean. The drag forces on the net were a function of twine diameter, twine roughness and fouling. After immersion, the uncoated nets had the most drag followed by the silicone and copper treatments. The cost of applying silicone to nets is high; however, improved formulations may provide a non-toxic alternative to control fouling.

  5. DOE Project on Heavy Vehicle Aerodynamic Drag FY 2005 Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    McCallen, R C; Salari, K; Ortega, J; Castellucci, P; Eastwood, C; Paschkewitz, J; Pointer, W D; DeChant, L J; Hassan, B; Browand, F; Radovich, C; Merzel, T; Plocher, D; Ross, J; Storms, B; Heineck, J T; Walker, S; Roy, C J

    2005-11-14

    Class 8 tractor-trailers consume 11-12% of the total US petroleum use. At high way 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; and (2) Establish a database of experimental, computational, and conceptual design information, and demonstrate the potential of new drag-reduction devices.

  6. Drag Moderation by the Melting of an Ice Surface in Contact with Water

    KAUST Repository

    Vakarelski, Ivan Uriev

    2015-07-24

    We report measurements of the effects of a melting ice surface on the hydrodynamic drag of ice-shell-metal-core spheres free falling in water at a Reynolds of number Re∼2×104–3×105 and demonstrate that the melting surface induces the early onset of the drag crisis, thus reducing the hydrodynamic drag by more than 50%. Direct visualization of the flow pattern demonstrates the key role of surface melting. Our observations support the hypothesis that the drag reduction is due to the disturbance of the viscous boundary layer by the mass transfer from the melting ice surface.

  7. An aerodynamic study of scramjet fuel injectors. [effect of injector thickness ratio on aerodynamic drag

    Science.gov (United States)

    Povinelli, L. A.

    1974-01-01

    The aerodynamic drag and fuel distribution patterns of injectors designed for a supersonic combustion ramjet were measured at Mach numbers of 2, 2.5, and 3. The most significant parameter effecting the drag was found to be the injector thickness ratio. A two-fold reduction in the thickness ratio caused a 65 percent decrease in drag. Changing the injector sweep angle a factor of 2 resulted in only a small change in drag. A reversal of injector sweep, from sweepback to sweepforward, did not change the measured drag. Helium gas was injected through the struts to simulate the penetration and spreading patterns of hydrogen. Sampling measurements were made at approximately 2 duct heights downstream of the combustor. The spacing required between fuel injectors was found to be about 10 jet diameters. The effect of gas injection on the measured drag was found to be minor.

  8. Grafted natural polymer as new drag reducing agent: An experimental approach

    Directory of Open Access Journals (Sweden)

    Abdulbari Hayder A.

    2012-01-01

    Full Text Available The present investigation introduces a new natural drag reducing agent which has the ability to improve the flow in pipelines carrying aqueous or hydrocarbon liquids in turbulent flow. Okra (Abelmoschus esculentus mucilage drag reduction performance was tested in water and hydrocarbon (gas-oil media after grafting. The drag reduction test was conducted in a buildup closed loop liquid circulation system consists of two pipes 0.0127 and 0.0381 m Inside Diameter (ID, four testing sections in each pipe (0.5 to 2.0 m, tank, pump and pressure transmitters. Reynolds number (Re, additive concentration and the transported media type (water and gas-oil, were the major drag reduction variables investigated. The experimental results show that, new additive drag reduction ability is high with maximum percentage of drag reduction (%Dr up to 60% was achieved. The experimental results showed that the drag reduction ability increased by increasing the additive concentration. The %Dr was found to increase by increasing the Re by using the water-soluble additive while it was found to decrease by increasing the Re when using the oil-soluble additive. The %Dr was higher in the 0.0381 m ID pipe. Finally, the grafted and natural mucilage showed high resistance to shear forces when circulated continuously for 200 seconds in the closed-loop system.

  9. A framework for understanding drag parameterizations for coral reefs

    Science.gov (United States)

    Rosman, Johanna H.; Hench, James L.

    2011-08-01

    In a hydrodynamic sense, a coral reef is a complex array of obstacles that exerts a net drag force on water moving over the reef. This drag is typically parameterized in ocean circulation models using drag coefficients (CD) or roughness length scales (z0); however, published CD for coral reefs span two orders of magnitude, posing a challenge to predictive modeling. Here we examine the reasons for the large range in reported CD and assess the limitations of using CD and z0 to parameterize drag on reefs. Using a formal framework based on the 3-D spatially averaged momentum equations, we show that CD and z0 are functions of canopy geometry and velocity profile shape. Using an idealized two-layer model, we illustrate that CD can vary by more than an order of magnitude for the same geometry and flow depending on the reference velocity selected and that differences in definition account for much of the range in reported CD values. Roughness length scales z0 are typically used in 3-D circulation models to adjust CD for reference height, but this relies on spatially averaged near-bottom velocity profiles being logarithmic. Measurements from a shallow backreef indicate that z0 determined from fits to point measurements of velocity profiles can be very different from z0 required to parameterize spatially averaged drag. More sophisticated parameterizations for drag and shear stresses are required to simulate 3-D velocity fields over shallow reefs; in the meantime, we urge caution when using published CD and z0 values for coral reefs.

  10. Leidenfrost Vapor Layers Reduce Drag without the Crisis in High Viscosity Liquids

    KAUST Repository

    Vakarelski, Ivan Uriev

    2016-09-08

    The drag coefficient CD of a solid smooth sphere moving in a fluid is known to be only a function of the Reynolds number Re and diminishes rapidly at the drag crisis around Re∼3×105. A Leidenfrost vapor layer on a hot sphere surface can trigger the onset of the drag crisis at a lower Re. By using a range of high viscosity perfluorocarbon liquids, we show that the drag reduction effect can occur over a wide range of Re, from as low as ∼600 to 105. The Navier slip model with a viscosity dependent slip length can fit the observed drag reduction and wake shape. © 2016 American Physical Society.

  11. Net Locality

    DEFF Research Database (Denmark)

    de Souza e Silva, Adriana Araujo; Gordon, Eric

    Provides an introduction to the new theory of Net Locality and the profound effect on individuals and societies when everything is located or locatable. Describes net locality as an emerging form of location awareness central to all aspects of digital media, from mobile phones, to Google Maps...... of emerging technologies, from GeoCities to GPS, Wi-Fi, Wiki Me, and Google Android....

  12. Net Neutrality

    DEFF Research Database (Denmark)

    Savin, Andrej

    2017-01-01

    Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else.......Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else....

  13. Why fibers are better turbulent drag reducing agents than polymers

    Science.gov (United States)

    Boelens, Arnout; Muthukumar, Murugappan

    2016-11-01

    It is typically found in literature that fibers are not as effective as drag reducing agents as polymers. However, for low concentrations, when adding charged polymers to either distilled or salt water, it is found that polymers showing rod-like behavior are better drag reducing agents than polymers showing coil-like behavior. In this study, using hybrid Direct Numerical Simulation with Langevin dynamics, a comparison is performed between polymer and fiber stress tensors in turbulent flow. The stress tensors are found to be similar, suggesting a common drag reducing mechanism in the onset regime. Since fibers do not have an elastic backbone, this must be a viscous effect. Analysis of the viscosity tensor reveals that all terms are negligible, except the off-diagonal shear viscosity associated with rotation. Based on this analysis, we are able to explain why charged polymers showing rod-like behavior are better drag reducing agents than polymers showing coil-like behavior. Additionally, we identify the rotational orientation time as the unifying time scale setting a new time criterion for drag reduction by both flexible polymers and rigid fibers. This research was supported by NSF Grant No. DMR-1404940 and AFOSR Grant No. FA9550-14-1-0164.

  14. Aerodynamic Drag and Gyroscopic Stability

    CERN Document Server

    Courtney, Elya R

    2013-01-01

    This paper describes the effects on aerodynamic drag of rifle bullets as the gyroscopic stability is lowered from 1.3 to 1.0. It is well known that a bullet can tumble for stability less than 1.0. The Sierra Loading Manuals (4th and 5th Editions) have previously reported that ballistic coefficient decreases significantly as gyroscopic stability, Sg, is lowered below 1.3. These observations are further confirmed by the experiments reported here. Measured ballistic coefficients were compared with gyroscopic stabilities computed using the Miller Twist Rule for nearly solid metal bullets with uniform density and computed using the Courtney-Miller formula for plastic-tipped bullets. The experiments reported here also demonstrate a decrease in aerodynamic drag near Sg = 1.23 +/- 0.02. It is hypothesized that this decrease in drag over a narrow band of Sg values is due to a rapid damping of coning motions (precession and nutation). Observation of this drag decrease at a consistent value of Sg demonstrates the relati...

  15. DOE's effort to reduce truck aerodynamic drag through joint experiments and computations.

    Energy Technology Data Exchange (ETDEWEB)

    Salari, Kambiz (Lawrence Livermore National Laboratory); Browand, Fred (University of Southern California); Sreenivas, Kidambi (University of Tennessee, Chattanooga); Pointer, W. David (Argonne National Laboratory); Taylor, Lafayette (University of Tennessee, Chattanooga); Pankajakshan, Ramesh (University of Tennessee, Chattanooga); Whitfield, David (University of Tennessee, Chattanooga); Plocher, Dennis (University of Southern California); Ortega, Jason M. (Lawrence Livermore National Laboratory); Merzel, Tai (University of Southern California); McCallen, Rose (Lawrence Livermore National Laboratory); Walker, Stephen M (NASA Ames Research Center); Heineck, James T (NASA Ames Research Center); Hassan, Basil; Roy, Christopher John (Auburn University); Storms, B. (NASA Ames Research Center); Ross, James (NASA Ames Research Center); Englar, Robert (Georgia Tech Research Institute); Rubel, Mike (Caltech); Leonard, Anthony (Caltech); Radovich, Charles (University of Southern California); Eastwood, Craig (Lawrence Livermore National Laboratory); Paschkewitz, John (Lawrence Livermore National Laboratory); Castellucci, Paul (Lawrence Livermore National Laboratory); DeChant, Lawrence Justin.

    2005-08-01

    Class 8 tractor-trailers are responsible for 11-12% of the total US consumption of petroleum. Overcoming aero drag represents 65% of energy expenditure at highway speeds. Most of the drag results from pressure differences and reducing highway speeds is very effective. The goal is to reduce aerodynamic drag by 25% which would translate to 12% improved fuel economy or 4,200 million gal/year. Objectives are: (1) In support of DOE's mission, provide guidance to industry in the reduction of aerodynamic drag; (2) To shorten and improve design process, establish a database of experimental, computational, and conceptual design information; (3) Demonstrate new drag-reduction techniques; and (4) Get devices on the road. Some accomplishments are: (1) Concepts developed/tested that exceeded 25% drag reduction goal; (2) Insight and guidelines for drag reduction provided to industry through computations and experiments; (3) Joined with industry in getting devices on the road and providing design concepts through virtual modeling and testing; and (4) International recognition achieved through open documentation and database.

  16. Coulomb drag in coherent mesoscopic systems

    DEFF Research Database (Denmark)

    Mortensen, Niels Asger; Flensberg, Karsten; Jauho, Antti-Pekka

    2001-01-01

    , such as the random matrix theory, or by numerical simulations. We show that Coulomb drag is sensitive to localized states, which usual transport measurements do not probe. For chaotic 2D systems we find a vanishing average drag, with a nonzero variance. Disordered 1D wires show a finite drag, with a large variance...

  17. A coating of passively oscillating flexible cilia to reduce drag

    Science.gov (United States)

    Revell, Alistair; Harwood, Adrian; O'Connor, Joseph; Sanchez, Jonathan; Favier, Julien

    2016-11-01

    We present results related to the reduction of wake drag by the coordinated action of a layer of passively oscillating flexible cilia. Inspired by the pop-up of bird feathers, this configuration is shown to self-adapt to the surrounding flow, leading to a stabilization of the wake, a reduction of the mean drag and of lift oscillations. The study is performed using Lattice Boltzmann method, coupled to a recent version of the immersed boundary method. We will present the physical analysis of the coupling between multiple beating cilia and an incoming fluid flow. The modal behaviour of the cilia dynamics will be discussed, as well as their effect on an archetype of unsteady separated boundary layer (first the oscillating channel flow and then the circular cylinder). In the latter case results demonstrate an optimal drag occurs for a particular stiffness, compared to the control case where the same cilia are fixed. It appears that the optimal results are due to a reconfiguration of the elastic coating according to the local vorticity of the flow, and a frequency lock-in, which leads to more stable wake and reduced drag. The structural parameters of the layer will be varied. Results from the PEL-SKIN project: funded by EU Grant #334954.

  18. Atmospheric and oceanic drag on sea ice

    Science.gov (United States)

    Tsamados, M.; Feltham, D. L.

    2012-12-01

    Pressure ridges, keels, floe edges and melt pond edges all introduce discrete obstructions to the flow of the air or ocean over the ice, and are a source of form drag. For typical ice covers the form drag contribution to the total drag is of comparable or greater magnitude to the surface or skin drag. In current climate models form drag is only accounted for by tuning of the air-ice and air-ocean drag coefficients, i.e. by altering the roughness length in a surface drag parameterization. The existing approach of skin drag parameter tuning, while numerically convenient, is poorly constrained by observations and fails to describe correctly the physics associated with the air-ice and ocean-ice drag. Here we combine recent theoretical developments to deduce the total neutral form drag coefficients from the key parameters of the ice cover such as ice concentration, size and area of the ridges and keels, freeboard and floe draft and size of melt ponds. We validate the assumptions of this parameterisation against remote sensing observations from airborne missions (IceBridge) and high resolution satellites. We incorporate the drag coefficients into the sea ice component of a climate model (the CICE model). This stage necessitates that the sea ice characteristics obtained locally from observations are mapped to the averaged sea ice quantities provided by the sea ice model at the larger grid cell length scale. We present results over the Arctic of a stand-alone version of the model and show the influence of the new drag parameterisation on the motion and mass of the ice cover. The new parameterisation allows the drag coefficients to be coupled to the sea ice state and therefore to evolve spatially and temporally. We test the predictions of the model against measured drag coefficients in several regions of the Arctic and find good agreement between model and observations.

  19. RESTful NET

    CERN Document Server

    Flanders, Jon

    2008-01-01

    RESTful .NET is the first book that teaches Windows developers to build RESTful web services using the latest Microsoft tools. Written by Windows Communication Foundation (WFC) expert Jon Flanders, this hands-on tutorial demonstrates how you can use WCF and other components of the .NET 3.5 Framework to build, deploy and use REST-based web services in a variety of application scenarios. RESTful architecture offers a simpler approach to building web services than SOAP, SOA, and the cumbersome WS- stack. And WCF has proven to be a flexible technology for building distributed systems not necessa

  20. Reduction of malaria during pregnancy by permethrin-treated bed nets in an area of intense perennial malaria transmission in western Kenya

    NARCIS (Netherlands)

    ter Kuile, Feiko O.; Terlouw, Dianne J.; Phillips-Howard, Penelope A.; Hawley, William A.; Friedman, Jennifer F.; Kariuki, Simon K.; Shi, Ya Ping; Kolczak, Margarette S.; Lal, Altaf A.; Vulule, John M.; Nahlen, Bernard L.

    2003-01-01

    The impact of insecticide (permethrin)-treated bed nets (ITNs) on malaria in pregnancy was studied in a rural area in western Kenya with intense perennial malaria transmission. All households in 40 of 79 villages were randomized to receive ITNs by January 1997. The ITNs were distributed in control

  1. Petri Nets

    Indian Academy of Sciences (India)

    Associate Professor of. Computer Science and. Automation at the Indian. Institute of Science,. Bangalore. His research interests are broadly in the areas of stochastic modeling and scheduling methodologies for future factories; and object oriented modeling. GENERAL I ARTICLE. Petri Nets. 1. Overview and Foundations.

  2. Petri Nets

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 8. Petri Nets - Overview and Foundations. Y Narahari. General Article Volume 4 Issue 8 August 1999 pp ... Author Affiliations. Y Narahari1. Department ot Computer Science and Automation, Indian Institute of Science, Bangalore 560 012, India.

  3. Leidenfrost vapour layer moderation of the drag crisis and trajectories of superhydrophobic and hydrophilic spheres falling in water

    KAUST Repository

    Vakarelski, Ivan Uriev

    2014-01-01

    We investigate the dynamic effects of a Leidenfrost vapour layer sustained on the surface of heated steel spheres during free fall in water. We find that a stable vapour layer sustained on the textured superhydrophobic surface of spheres falling through 95 °C water can reduce the hydrodynamic drag by up to 75% and stabilize the sphere trajectory for the Reynolds number between 104 and 106, spanning the drag crisis in the absence of the vapour layer. For hydrophilic spheres under the same conditions, the transition to drag reduction and trajectory stability occurs abruptly at a temperature different from the static Leidenfrost point. The observed drag reduction effects are attributed to the disruption of the viscous boundary layer by the vapour layer whose thickness depends on the water temperature. Both the drag reduction and the trajectory stabilization effects are expected to have significant implications for development of sustainable vapour layer based technologies. © the Partner Organisations 2014.

  4. Leidenfrost vapour layer moderation of the drag crisis and trajectories of superhydrophobic and hydrophilic spheres falling in water.

    Science.gov (United States)

    Vakarelski, Ivan U; Chan, Derek Y C; Thoroddsen, Sigurdur T

    2014-08-21

    We investigate the dynamic effects of a Leidenfrost vapour layer sustained on the surface of heated steel spheres during free fall in water. We find that a stable vapour layer sustained on the textured superhydrophobic surface of spheres falling through 95 °C water can reduce the hydrodynamic drag by up to 75% and stabilize the sphere trajectory for the Reynolds number between 10(4) and 10(6), spanning the drag crisis in the absence of the vapour layer. For hydrophilic spheres under the same conditions, the transition to drag reduction and trajectory stability occurs abruptly at a temperature different from the static Leidenfrost point. The observed drag reduction effects are attributed to the disruption of the viscous boundary layer by the vapour layer whose thickness depends on the water temperature. Both the drag reduction and the trajectory stabilization effects are expected to have significant implications for development of sustainable vapour layer based technologies.

  5. Whose drag is it anyway? Drag kings and monarchy in the UK.

    Science.gov (United States)

    Willox, Annabelle

    2002-01-01

    This chapter will show that the term "drag" in drag queen has a different meaning, history and value to the term "drag" in drag king. By exposing this basic, yet fundamental, difference this paper will expose the problems inherent in the assumption of parity between the two forms of drag. An exposition of how camp has been used to comprehend and theorise drag queens will facilitating an understanding of the parasitic interrelationship between camp and drag queen performances, while a critique of "Towards a Butch-Femme Aesthetic," by Sue Ellen Case, will point out the problematic assumptions made about camp when attributed to a cultural location different to the drag queen. By interrogating the historical, cultural and theoretical similarities and differences between drag kings, butches, drag queens and femmes this paper will expose the flawed assumption that camp can be attributed to all of the above without proviso, and hence expose why drag has a fundamentally different contextual meaning for kings and queens. This chapter will conclude by examining the work of both Judith Halberstam and Biddy Martin and the practical examples of drag king and queen performances provided at the UK drag contest held at The Fridge in Brixton, London on 23 June 1999.

  6. Drag and drop display & builder

    Energy Technology Data Exchange (ETDEWEB)

    Bolshakov, Timofei B.; Petrov, Andrey D.; /Fermilab

    2007-12-01

    The Drag and Drop (DnD) Display & Builder is a component-oriented system that allows users to create visual representations of data received from data acquisition systems. It is an upgrade of a Synoptic Display mechanism used at Fermilab since 2002. Components can be graphically arranged and logically interconnected in the web-startable Project Builder. Projects can be either lightweight AJAX- and SVG-based web pages, or they can be started as Java applications. The new version was initiated as a response to discussions between the LHC Controls Group and Fermilab.

  7. Research of low boom and low drag supersonic aircraft design

    Directory of Open Access Journals (Sweden)

    Feng Xiaoqiang

    2014-06-01

    Full Text Available Sonic boom reduction will be an issue of utmost importance in future supersonic transport, due to strong regulations on acoustic nuisance. The paper describes a new multi-objective optimization method for supersonic aircraft design. The method is developed by coupling Seebass–George–Darden (SGD inverse design method and multi-objective genetic algorithm. Based on the method, different codes are developed. Using a computational architecture, a conceptual supersonic aircraft design environment (CSADE is constructed. The architecture of CSADE includes inner optimization level and out optimization level. The low boom configuration is generated in inner optimization level by matching the target equivalent area distribution and actual equivalent area distribution. And low boom/low drag configuration is generated in outer optimization level by using NSGA-II multi-objective genetic algorithm to optimize the control parameters of SGD method and aircraft shape. Two objective functions, low sonic boom and low wave drag, are considered in CSADE. Physically reasonable Pareto solutions are obtained from the present optimization. Some supersonic aircraft configurations are selected from Pareto front and the optimization results indicate that the swept forward wing configuration has benefits in both sonic boom reduction and wave drag reduction. The results are validated by using computational fluid dynamics (CFD analysis.

  8. Dragging cylinders in slow viscous flows

    Science.gov (United States)

    Luca, Elena; Crowdy, Darren

    2015-11-01

    The so-called ``dragging problem'' in slow viscous fluids is an important basic flow with many applications. In two dimensions, the Stokes paradox means there is no solution to the dragging problem for a cylinder in free space. The presence of walls changes this; the solutions exist, but are not easy to find without purely numerical methods. This talk describes new ``transform methods'' that produce convenient, semi-analytical solutions to dragging problems for cylinders in various geometries. We apply the techniques to low-Reynolds-number swimming where dragging problem solutions can be combined with the reciprocal theorem to compute swimmer dynamics in confined domains.

  9. Discovery of riblets in a bird beak (Rynchops) for low fluid drag

    OpenAIRE

    Martin, Samuel; Bhushan, Bharat

    2016-01-01

    Riblet structures found on fast-swimming shark scales, such as those found on a mako shark, have been shown to reduce fluid drag. In previous experimental and modelling studies, riblets have been shown to provide drag reduction by lifting vortices formed in turbulent flow, decreasing overall shear stresses. Skimmer birds (Rynchops) are the only birds to catch fish in flight by flying just above the water surface with a submerged beak to fish for food. Because they need to quickly catch prey, ...

  10. Hydrodynamic Drag Force Measurement Of A Functionalized Surface Exhibiting Superhydrophobic Properties

    Science.gov (United States)

    2016-12-01

    resiliency of this surface treatment . 14. SUBJECT TERMS superhydrophobic, superhydrophilic, Femto-second laser surface processing , skin friction drag...and Y. Kunitake, Frictional drag reduction with air lubricant over a super- water -repellent surface, Journal of Marine Science and Technology , vol...properties being extended to a variety of metallic substrates through the process of ablation due to femto-second laser surface processing (FLSP), it is

  11. An investigation of the transonic viscous drag coefficient for axi-symmetric bodies

    OpenAIRE

    Fan, Yue Sang

    1995-01-01

    Viscous drag in the transonic regime over an axi-symmetric body with a unique aft contour surface is investigated. The forebody is composed of an arbitrary ellipsoid. The unique aft contour surface has been obtained by an exact solution of the small perturbation transonic equation, using guidelines and tools developed at the Naval Postgraduate School. This unique contour allows the delay of shock formation in the aft portion, hence delaying the onset of wave drag which results in a reduction ...

  12. Analysis and design of planar and non-planar wings for induced drag minimization

    Science.gov (United States)

    Mortara, Karl W.; Straussfogel, Dennis M.; Maughmer, Mark D.

    1992-01-01

    The goal of the work reported herein is to develop and validate computational tools to be used for the design of planar and non-planar wing geometries for minimum induced drag. Because of the iterative nature of the design problem, it is important that, in addition to being sufficiently accurate for the problem at hand, these tools need to be reasonably fast and computationally efficient. Toward this end, a method of predicting induced drag in the presence of a free wake has been coupled with a panel method. The induced drag prediction technique is based on the application of the Kutta-Joukowski law at the trailing edge. Until now, the use of this method has not been fully explored and pressure integration and Trefftz-plane calculations favored. As is shown in this report, however, the Kutta-Joukowski method is able to give better results for a given amount of effort than the more commonly used techniques, particularly when relaxed wakes and non-planar wing geometries are considered. Using these methods, it is demonstrated that a reduction in induced drag can be achieved through non-planar wing geometries. It remains to determine what overall drag reductions are possible when the induced drag reduction is traded-off against increased wetted area. With the design methodology that is described herein, such trade studies can be performed in which the non-linear effects of the free wake are taken into account.

  13. Analysis of Zero Reynolds Shear Stress Appearing in Dilute Surfactant Drag-Reducing Flow

    Directory of Open Access Journals (Sweden)

    Weiguo Gu

    2011-01-01

    Full Text Available Dilute surfactant solution of 25 ppm in the two-dimensional channel is investigated experimentally compared with water flow. Particle image velocimetry (PIV system is used to take 2D velocity frames in the streamwise and wall-normal plane. Based on the frames of instantaneous vectors and statistical results, the phenomenon of zero Reynolds shear stress appearing in the drag-reducing flow is discussed. It is found that 25 ppm CTAC solution exhibits the highest drag reduction at Re = 25000 and loses drag reduction completely at Re = 40000. When drag reduction lies in the highest, Reynolds shear stress disappears and reaches zero although the RMS of the velocity fluctuations is not zero. By the categorization in four quadrants, the fluctuations of 25 ppm CTAC solution are distributed in all four quadrants equally at Re = 25000, which indicates that turnaround transportation happens in drag-reducing flow besides Reynolds shear stress transportation. Moreover, the contour distribution of streamwise velocity and the fluctuations suggests that turbulence transportation is depressed in drag-reducing flow. The viscoelasticity is possible to decrease the turbulence transportation and cause the turnaround transportation.

  14. Coulomb drag in the mesoscopic regime

    DEFF Research Database (Denmark)

    Mortensen, N.A.; Flensberg, Karsten; Jauho, Antti-Pekka

    2002-01-01

    We present a theory for Coulomb drag between two mesoscopic systems which expresses the drag in terms of scattering matrices and wave functions. The formalism can be applied to both ballistic and disordered systems and the consequences can be studied either by numerical simulations or analytic...

  15. Vertical variations of coral reef drag forces

    Science.gov (United States)

    Asher, Shai; Niewerth, Stephan; Koll, Katinka; Shavit, Uri; LWI Collaboration; Technion Collaboration

    2017-11-01

    Corals rely on water flow for the supply of nutrients, particles and energy. Therefore, modeling of processes that take place inside the reef, such as respiration and photosynthesis, relies on models that describe the flow and concentration fields. Due to the high spatial heterogeneity of branched coral reefs, depth average models are usually applied. Such an average approach is insufficient when the flow spatial variation inside the reef is of interest. We report on measurements of vertical variations of drag force that are needed for developing 3D flow models. Coral skeletons were densely arranged along a laboratory flume. Two corals were CT-scanned and replaced with horizontally sliced 3D printed replicates. Drag profiles were measured by connecting the slices to costume drag sensors and velocity profiles were measured using a LDV. The measured drag of whole colonies was in excellent agreement with previous studies; however, these studies never showed how drag varies inside the reef. In addition, these distributions of drag force showed an excellent agreement with momentum balance calculations. Based on the results, we propose a new drag model that includes the dispersive stresses, and consequently displays reduced vertical variations of the drag coefficient.

  16. Determination of the surface drag coefficient

    DEFF Research Database (Denmark)

    Mahrt, L.; Vickers, D.; Sun, J.L.

    2001-01-01

    This study examines the dependence of the surface drag coefficient on stability, wind speed, mesoscale modulation of the turbulent flux and method of calculation of the drag coefficient. Data sets over grassland, sparse grass, heather and two forest sites are analyzed. For significantly unstable ...

  17. Coulomb drag in coherent mesoscopic systems

    DEFF Research Database (Denmark)

    Mortensen, Asger; Flensberg, Karsten; Jauho, Antti-Pekka

    2001-01-01

    We present a theory for Coulomb drag between two mesoscopic systems. Our formalism expresses the drag in terms of scattering matrices and wave functions, and its range of validity covers both ballistic and disordered systems. The consequences can be worked out either by analytic means...

  18. Drag coefficient for the air-sea exchange in hurricane conditions

    CERN Document Server

    Golbraikh, E

    2013-01-01

    The physical model is proposed for prediction of the non-monotonic drag coefficient variation with the neutral stability 10-m wind speed, U10. The model is based upon measurements of the foam coverage fraction and characteristic size of foam bubbles with U10, and on the drag coefficient approximation by the linearly weighted averaging over alternating foam-free and foam-covered portions of the ocean surface. The obtained drag coefficient is in fair agreement with that obtained by field measurements of the vertical variation of mean wind speed in Powell et al. (Nature, 2003) which discover reduction of the sea-surface drag with U10 rising to hurricane conditions.

  19. Influence of 15N enrichment on the net isotopic fractionation factor during the reduction of nitrate to nitrous oxide in soil

    DEFF Research Database (Denmark)

    Mathieu, O.; Levegue, J.; Henault, C.

    2007-01-01

    or relatively low (15)N enrichment levels and requires a good knowledge of the isotopic fractionation effect inherent to this biological mechanism. This paper reports the measurement of the net and instantaneous isotopic fractionation factor (alpha(i)(s/p)) during the denitrification of NO(3)(-) to N(2)O over...... a range of (15)N substrate enrichments (0.37 to 1.00 atom% (15)N). At natural abundance level, the isotopic fractionation effect reported falls well within the range of data previously observed. For (15)N-enriched substrate, the value of alpha(i)(s/p) was not constant and decreased from 1.024 to 1......Nitrous oxide, a greenhouse gas, is mainly emitted from soils during the denitrification process. Nitrogen stable-isotope investigations can help to characterise the N(2)O source and N(2)O production mechanisms. The stable-isotope approach is increasingly used with (15)N natural abundance...

  20. Air Drag Effects on the Missile Trajectories

    Directory of Open Access Journals (Sweden)

    F. A. Abd El-Salam

    2011-01-01

    Full Text Available The equations of motion of a missile under the air drag effects are constructed. The modified TD88 is surveyed. Using Lagrange's planetary equations in Gauss form, the perturbations, due to the air drag in the orbital elements, are computed between the eccentric anomalies of the burn out and the reentry points [Ebo,2π−Ebo], respectively. The range equation is expressed as an infinite series in terms of the eccentricity e and the eccentric anomaly E. The different errors in the missile-free range due to the drag perturbations in the missile trajectory are obtained.

  1. Drag and Torque on Locked Screw Propeller

    Directory of Open Access Journals (Sweden)

    Tomasz Tabaczek

    2014-09-01

    Full Text Available Few data on drag and torque on locked propeller towed in water are available in literature. Those data refer to propellers of specific geometry (number of blades, blade area, pitch and skew of blades. The estimation of drag and torque of an arbitrary propeller considered in analysis of ship resistance or propulsion is laborious. The authors collected and reviewed test data available in the literature. Based on collected data there were developed the empirical formulae for estimation of hydrodynamic drag and torque acting on locked screw propeller. Supplementary CFD computations were carried out in order to prove the applicability of the formulae to modern moderately skewed screw propellers.

  2. Reduction of childhood malaria by social marketing of insecticide-treated nets: a case-control study of effectiveness in Malawi.

    Science.gov (United States)

    Mathanga, Don P; Campbell, Carl H; Taylor, Terrie E; Barlow, Robin; Wilson, Mark L

    2005-09-01

    Use of an insecticide-treated net (ITN) is now the central focus for the Roll Back Malaria campaign, and disease-endemic countries have embarked on large-scale ITN distribution programs. We assessed the impact of an ITN social marketing program on clinical malaria in children less than five years of age. A case-control study was undertaken at Ndirande Health Center in the peri-urban area of the city of Blantyre, Malawi. Cases were defined by an axillary temperature > or = 37.5 degrees C or a history of fever within the last 48 hours and a positive blood smear for Plasmodium falciparum. The individual effectiveness of ITN use was 40% (95% confidence interval [CI] = 10-60%) when cases were compared with clinic controls and 50% (95% CI = 0-60%) in comparison with community controls. With ITN coverage of 42%, the community effectiveness of this program was estimated to range from 17% to 21%. This represents 1,480 malaria cases averted by the intervention in a population of 15,000 children. Our results show that the benefits of ITN social marketing programs in reducing malaria are enormous. Targeting the poor could increase those benefits.

  3. Experimental study on the characteristics of ventilated cavitation around an underwater navigating body influenced by turbulent drag-reducing additives

    Science.gov (United States)

    Jiang, ChenXing; Li, FengChen

    2015-09-01

    In this study, a new control strategy for turbulent drag reduction involving ventilated cavitation is proposed. The configurational and hydrodynamic characteristics of ventilated cavities influenced by turbulent drag-reducing additives were experimentally studied in water tunnel. The test model was fixed in the water tunnel by a strut in the aft-part. Aqueous solutions of CTAC/NaSal (cetyltrimethyl ammonium chloride/sodium salicylate) with weight concentrations of 100, 200, 400 and 600 ppm (part per million), respectively, were injected into the ventilated air cavity from the edge of the cavitator with accurate control by an injection pump. The cavity configurations were recorded by a high-speed CCD camera. The hydrodynamic characteristics of the test model were measured by a six-component balance. Experimental results show that, within the presently tested cases, the lengths of cavity influenced by drag-reducing solution are smaller than normal condition (ventilated cavity) in water, but the asymmetry of the cavity is improved. The drag resisted by the test model is reduced dramatically (the maximum drag reduction can reach to 80%) and the re-entrant jet is more complex after the CTAC solution is injected into the cavity. Turbulent drag-reducing additives have the potential in enhancement of supercavitating asymmetry and further drag reduction.

  4. Developments in greenhouse gas emissions and net energy use in Danish agriculture - How to achieve substantial CO{sub 2} reductions?

    Energy Technology Data Exchange (ETDEWEB)

    Dalgaard, T., E-mail: tommy.dalgaard@agrsci.dk [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Olesen, J.E.; Petersen, S.O.; Petersen, B.M.; Jorgensen, U.; Kristensen, T.; Hutchings, N.J. [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Gyldenkaerne, S. [Aarhus University, National Environmental Research Institute, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Hermansen, J.E. [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark)

    2011-11-15

    Greenhouse gas (GHG) emissions from agriculture are a significant contributor to total Danish emissions. Consequently, much effort is currently given to the exploration of potential strategies to reduce agricultural emissions. This paper presents results from a study estimating agricultural GHG emissions in the form of methane, nitrous oxide and carbon dioxide (including carbon sources and sinks, and the impact of energy consumption/bioenergy production) from Danish agriculture in the years 1990-2010. An analysis of possible measures to reduce the GHG emissions indicated that a 50-70% reduction of agricultural emissions by 2050 relative to 1990 is achievable, including mitigation measures in relation to the handling of manure and fertilisers, optimization of animal feeding, cropping practices, and land use changes with more organic farming, afforestation and energy crops. In addition, the bioenergy production may be increased significantly without reducing the food production, whereby Danish agriculture could achieve a positive energy balance. - Highlights: > GHG emissions from Danish agriculture 1990-2010 are calculated, including carbon sequestration. > Effects of measures to further reduce GHG emissions are listed. > Land use scenarios for a substantially reduced GHG emission by 2050 are presented. > A 50-70% reduction of agricultural emissions by 2050 relative to 1990 is achievable. > Via bioenergy production Danish agriculture could achieve a positive energy balance. - Scenario studies of greenhouse gas mitigation measures illustrate the possible realization of CO{sub 2} reductions for Danish agriculture by 2050, sustaining current food production.

  5. Reducing turbulent boundary layer drag by a sustainable thin-air film

    Science.gov (United States)

    Wang, Cong; Jeon, David; Gharib, Morteza

    2017-11-01

    Reduction of hydrodynamic frictional drag through introduction of air bubbles or films at the wall regions has been tried by several groups in the past. The main challenge for these approaches has been to sustain the air bubble or film under high turbulent velocity fluctuations. We will report a novel technique that allows maintaining stable oscillating air films over solid surface in order to obtain large drag reduction effect. Based on our DPIV results, we will present a potential mechanism for the Reynolds stress suppression in the near wall region. This work is supported by the Office of Naval Research under Grant No. N00014-15-1-2479.

  6. Alleviation of fuselage form drag using vortex flows: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Wortman, A.

    1987-09-15

    The concept of using vortex generators to reduce the fuselage form drag of transport aircraft combines the outflow from the plane of symmetry which is induced by the rotational component of the vortex flow with the energization of the boundary layer to reduce the momentum thickness and to delay or eliminate flow separation. This idea was first advanced by the author in 1981. Under a DOE grant, the concept was validated in wind tunnel tests of approximately 1:17 scale models of fuselages of Boeing 747 and Lockheed C-5 aircraft. The search for the minimum drag involved three vortex generator configurations with three sizes of each in six locations clustered in the aft regions of the fuselages at the beginning of the tail upsweep. The local Reynolds number, which is referred to the length of boundary layer run from the nose, was approximately 10{sup 7} so that a fully developed turbulent boundary layer was present. Vortex generator planforms ranged from swept tapered, through swept straight, to swept reverse tapered wings whose semi-spans ranged from 50% to 125% of the local boundary layer thickness. Pitch angles of the vortex generators were varied by inboard actuators under the control of an external proportional digital radio controller. It was found that certain combinations of vortex generator parameters increased drag. However, with certain configurations, locations, and pitch angles of vortex generators, the highest drag reductions were 3% for the 747 and about 6% for the C-5, thus confirming the arguments that effectiveness increases with the rate of upsweep of the tail. Greatest gains in performance are therefore expected on aft loading military transports. 10 refs., 11 figs., 1 tab.

  7. Analytical Ballistic Trajectories with Approximately Linear Drag

    National Research Council Canada - National Science Library

    Giliam J. P. de Carpentier

    2014-01-01

      This paper introduces a practical analytical approximation of projectile trajectories in 2D and 3D roughly based on a linear drag model and explores a variety of different planning algorithms for these trajectories...

  8. Satellite Formation Control Using Atmospheric Drag

    National Research Council Canada - National Science Library

    Hajovsky, Blake B

    2007-01-01

    This study investigates the use of a linear quadratic terminal controller to reconfigure satellite formations using atmospheric drag actuated control while minimizing the loss of energy of the formation...

  9. The physics of orographic gravity wave drag

    Directory of Open Access Journals (Sweden)

    Miguel A C Teixeira

    2014-07-01

    Full Text Available The drag and momentum fluxes produced by gravity waves generated in flow over orography are reviewed, focusing on adiabatic conditions without phase transitions or radiation effects, and steady mean incoming flow. The orographic gravity wave drag is first introduced in its simplest possible form, for inviscid, linearized, non-rotating flow with the Boussinesq and hydrostatic approximations, and constant wind and static stability. Subsequently, the contributions made by previous authors (primarily using theory and numerical simulations to elucidate how the drag is affected by additional physical processes are surveyed. These include the effect of orography anisotropy, vertical wind shear, total and partial critical levels, vertical wave reflection and resonance, non-hydrostatic effects and trapped lee waves, rotation and nonlinearity. Frictional and boundary layer effects are also briefly mentioned. A better understanding of all of these aspects is important for guiding the improvement of drag parametrization schemes.

  10. Solar and Drag Sail Propulsion: From Theory to Mission Implementation

    Science.gov (United States)

    Johnson, Les; Alhorn, Dean; Boudreaux, Mark; Casas, Joe; Stetson, Doug; Young, Roy

    2014-01-01

    , and began its mission after it was ejected from the FASTSAT into Earth orbit, where it remained for several weeks before deorbiting as planned. NASA recently selected two small satellite missions for study as part of the Advanced Exploration Systems (AES) Program, both of which will use solar sails to enable their scientific objectives. Lunar Flashlight, managed by JPL, will search for and map volatiles in permanently shadowed Lunar craters using a solar sail as a gigantic mirror to steer sunlight into the shaded craters. The Near Earth Asteroid (NEA) Scout mission will use the sail as primary propulsion allowing it to survey and image one or more NEA's of interests for possible future human exploration. Both are being studied for possible launch in 2017. The Planetary Society's privately funded LightSail-A and -B cubesat-class spacecraft are nearly complete and scheduled for launch in 2015 and 2016, respectively. MMA Design launched their DragNet deorbit system in November 2013, which will deploy from the STPSat-3 spacecraft as an end of life deorbit system. The University of Surrey is building a suite of cubesat class drag and solar sail systems that will be launched beginning in 2015. As the technology matures, solar sails will increasingly be used to enable science and exploration missions that are currently impossible or prohibitively expensive using traditional chemical and electric rockets. For example, the NASA Heliophysics Decadal Survey identifies no less than three such missions for possible flight before the mid-2020's. Solar and drag sail propulsion technology is no longer merely an interesting theoretical possibility; it has been demonstrated in space and is now a critical technology for science and solar system exploration.

  11. Drag Performance of Twist Morphing MAV Wing

    OpenAIRE

    Ismail N.I.; Zulkifli A.H.; Talib R.J.; Zaini H.; Yusoff H.

    2016-01-01

    Morphing wing is one of latest evolution found on MAV wing. However, due to few design problems such as limited MAV wing size and complicated morphing mechanism, the understanding of its aerodynamic behaviour was not fully explored. In fact, the basic drag distribution induced by a morphing MAV wing is still remained unknown. Thus, present work is carried out to compare the drag performance between a twist morphing wing with membrane and rigid MAV wing design. A quasi-static aeroelastic analy...

  12. The Minimum Induced Drag of Aerofoils

    Science.gov (United States)

    Munk, M. M.

    1979-01-01

    Equations are derived to demonstrate which distribution of lifting elements result in a minimum amount of aerodynamic drag. The lifting elements were arranged (1) in one line, (2) parallel lying in a transverse plane, and (3) in any direction in a transverse plane. It was shown that the distribution of lift which causes the least drag is reduced to the solution of the problem for systems of airfoils which are situated in a plane perpendicular to the direction of flight.

  13. Drag Performance of Twist Morphing MAV Wing

    Directory of Open Access Journals (Sweden)

    Ismail N.I.

    2016-01-01

    Full Text Available Morphing wing is one of latest evolution found on MAV wing. However, due to few design problems such as limited MAV wing size and complicated morphing mechanism, the understanding of its aerodynamic behaviour was not fully explored. In fact, the basic drag distribution induced by a morphing MAV wing is still remained unknown. Thus, present work is carried out to compare the drag performance between a twist morphing wing with membrane and rigid MAV wing design. A quasi-static aeroelastic analysis by using the Ansys-Fluid Structure Interaction (FSI method is utilized in current works to predict the drag performance a twist morphing MAV wing design. Based on the drag pattern study, the results exhibits that the morphing wing has a partial similarities in overall drag pattern with the baseline (membrane and rigid wing. However, based CD analysis, it shows that TM wing induced higher CD magnitude (between 25% to 82% higher than to the baseline wing. In fact, TM wing also induced the largest CD increment (about 20% to 27% among the wings. The visualization on vortex structure revealed that TM wing also produce larger tip vortex structure (compared to baseline wings which presume to promote higher induce drag component and subsequently induce its higher CD performance.

  14. 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.

  15. Drag crisis moderation by thin air layers sustained on superhydrophobic spheres falling in water

    KAUST Repository

    Jetly, Aditya

    2018-01-22

    We investigate the effect of thin air layers naturally sustained on superhydrophobic surfaces on the terminal velocity and drag force of metallic spheres free falling in water. The surface of 20 mm to 60 mm steel or tungsten-carbide spheres is rendered superhydrophobic by a simple coating process that uses commercially available hydrophobic agent. By comparing the free fall of unmodified spheres and superhydrophobic spheres in a 2.5 meters tall water tank, It is demonstrated that even a very thin air layer (~ 1 – 2 μm) that covers the freshly dipped superhydrophobic sphere, can reduce the drag force on the spheres by up to 80 %, at Reynolds numbers 105 - 3×105 , owing to an early drag crisis transition. This study complements prior investigations on the drag reduction efficiency of model gas layers sustained on heated metal spheres falling in liquid by the Leidenfrost effect. The drag reduction effects are expected to have significant implication for the development of sustainable air-layer-based energy saving technologies.

  16. Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity

    OpenAIRE

    Bharat Bhushan

    2011-01-01

    Summary The emerging field of biomimetics allows one to mimic biology or nature to develop nanomaterials, nanodevices, and processes which provide desirable properties. Hierarchical structures with dimensions of features ranging from the macroscale to the nanoscale are extremely common in nature and possess properties of interest. There are a large number of objects including bacteria, plants, land and aquatic animals, and seashells with properties of commercial interest. Certain plant leaves...

  17. Development of a Plasma Injector for Supersonic Drag Reduction Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Methods to reduce the turbulent viscous skin friction stand out as paramount to increasing the energy efficiency, and therefore the aerodynamic efficiency of...

  18. Integrating UAS Flocking Operations with Formation Drag Reduction

    Science.gov (United States)

    2014-03-01

    Captain, USAF Approved: //SIGNED// 24 Feb 2014 John M. Colombi, Ph. D. ( Chairman ) Date //SIGNED// 24 Feb 2014 David R...efficiency bonus and decreased workload. While significant research has also been done into the increased efficiency gained by taking advantage of...requires the flock to orbit around a fixed point on the ground at a small radius, which can be approximated by flying a square pattern, 55 the wake

  19. Injection of Drag Reducing Additives Into Turbulent Water Flows. Mixing Experiments and Newtonian Burst Frequency.

    Science.gov (United States)

    1987-04-01

    Heterogeneous drag reduction in turbulent pipe flow. The Influence of Polymer Additives on Velocity and Temperature Fields, B. Gampert , ed., Springer-Verlag...Temperature Fields, B. Gampert , ed., Springer-Verlag, Berlin. Kim, H.T., S.J. Kline and W.C. Reynolds, 1971. The production of turbulence near a smooth

  20. Altitude-Wind-Tunnel Investigation of the 19B-2, 19B-8, and 19XB-1 Jet Propulsion Engines. 3; Performance and Windmilling Drag Characteristics

    Science.gov (United States)

    Fleming, WIlliam A.; Dietz, Robert O., Jr.

    1957-01-01

    The performance characteristics of the 19B-8 and 19XB-1 turbojet engines and the windmilling-drag characteristics of the 19B-6 engine were determined in the Cleveland altitude wind tunnel. The investigations were conducted on the 19B-8 engine at simulated altitudes from 5000 to 25,000 feet with various free-stream ram-pressure ratios and on the 19XB--1 engine at simulated altitudes from 5000 to 30,000 feet with approximately static free-stream conditions. Data for these two engines are presented to show the effect of altitude, free-stream ram-pressure ratio, and tail-pipe-nozzle area on engine performance. A 21-percent reduction in tail-pipe-nozzle area of the 19B-8 engine increased the let thrust 43 percent the net thrust 72 percent, and the fuel consumption 64 percent. An increase in free-stream ram-pressure ratio raised the jet thrust and the air flow and lowered the net thrust throughout the entire range of engine speeds for the 19B-8 engine. At similar operating conditions, the corrected jet thrust and corrected air flow were approximately the same for both engines, and the corrected specific fuel consumption based on jet thrust was lower for the 19XB-1 engine than for the 19B-8 engine. The thrust and air-flow data obtained with both engines at various altitudes for a given free-stream rampressure ratio were generalized to standard sea-level atmospheric conditions. The performance parameters involving fuel consumption generalized only at high engine speeds at simulated altitudes as high as 15,000 feet. The windmilling drag of the 19B-8 engine increased rapidly as the airspeed was increased.

  1. Plasmon drag effect in metal nanostructures

    Science.gov (United States)

    Noginova, N.; Rono, V.; Bezares, F. J.; Caldwell, J. D.

    2013-11-01

    In order to better understand the mechanism of the photon drag effect in plasmonic nanostructures, photo-induced electric signals have been studied in gold and silver films and various plasmonic nanostructures. The spectral dependence of the effect points to the primary role of individual localized plasmon resonances in the photo-induced electromotive force (emf) generation responsible for the photon drag effect. We demonstrate the potential to engineer both the magnitude and polarity of the emf with nanoscale geometry and provide a simple model based on the intrinsic nonlinearity of metal in defining this effect.

  2. ASTROPHYSICS: Neutron Stars Imply Relativity's a Drag.

    Science.gov (United States)

    Schilling, G

    2000-09-01

    A new finding, based on x-rays from distant neutron stars, could be the first clear evidence of a weird relativistic effect called frame dragging, in which a heavy chunk of spinning matter wrenches the space-time around it like an eggbeater. Using data from NASA's Rossi X-ray Timing Explorer, three astronomers in Amsterdam found circumstantial evidence for frame dragging in the flickering of three neutron stars in binary systems. They announced their results in the 1 September issue of The Astrophysical Journal.

  3. New drag laws for flapping flight

    Science.gov (United States)

    Agre, Natalie; Zhang, Jun; Ristroph, Leif

    2014-11-01

    Classical aerodynamic theory predicts that a steadily-moving wing experiences fluid forces proportional to the square of its speed. For bird and insect flight, however, there is currently no model for how drag is affected by flapping motions of the wings. By considering simple wings driven to oscillate while progressing through the air, we discover that flapping significantly changes the magnitude of drag and fundamentally alters its scaling with speed. These measurements motivate a new aerodynamic force law that could help to understand the free-flight dynamics, control, and stability of insects and flapping-wing robots.

  4. Correlated Coulomb drag in capacitively coupled quantum-dot structures

    DEFF Research Database (Denmark)

    Kaasbjerg, Kristen; Jauho, Antti-Pekka

    2016-01-01

    We study theoretically Coulomb drag in capacitively coupled quantum dots (CQDs) -- a biasdriven dot coupled to an unbiased dot where transport is due to Coulomb mediated energy transfer drag. To this end, we introduce a master-equation approach which accounts for higher-order tunneling (cotunneling......) processes as well as energy-dependent lead couplings, and identify a mesoscopic Coulomb drag mechanism driven by nonlocal multi-electron cotunneling processes. Our theory establishes the conditions for a nonzero drag as well as the direction of the drag current in terms of microscopic system parameters...... on Coulomb drag in CQD systems....

  5. Effect of plasma actuator and splitter plate on drag coefficient of a circular cylinder

    Directory of Open Access Journals (Sweden)

    Akbıyık Hürrem

    2016-01-01

    Full Text Available In this paper, an experimental study on flow control around a circular cylinder with splitter plate and plasma actuator is investigated. The study is performed in wind tunnel for Reynolds numbers at 4000 and 8000. The wake region of circular cylinder with a splitter plate is analyzed at different angles between 0 and 180 degrees. In this the study, not only plasma actuators are activated but also splitter plate is placed behind the cylinder. A couple electrodes are mounted on circular cylinder at ±90 degrees. Also, flow visualization is achieved by using smoke wire method. Drag coefficient of the circular cylinder with splitter plate and the plasma actuator are obtained for different angles and compared with the plain circular cylinder. While attack angle is 0 degree, drag coefficient is decreased about 20% by using the splitter plate behind the circular cylinder. However, when the plasma actuators are activated, the improvement of the drag reduction is measured to be 50%.

  6. Experimental and Numerical Study of Water Entry Supercavity Influenced by Turbulent Drag-Reducing Additives

    Directory of Open Access Journals (Sweden)

    Chen-Xing Jiang

    2014-04-01

    Full Text Available The configurational and dynamic characteristics of water entry supercavities influenced by turbulent drag-reducing additives were studied through supercavitating projectile approach, experimentally and numerically. The projectile was projected vertically into water and aqueous solution of CTAC with weight concentrations of 100, 500, and 1000 ppm, respectively, using a pneumatic nail gun. The trajectories of the projectile and the supercavity configuration were recorded by a high-speed CCD camera. Besides, water entry supercavities in water and CTAC solution were numerically simulated based on unsteady RANS scheme, together with application of VOF multiphase model. The Cross viscosity model was adopted to represent the fluid property of CTAC solution. It was obtained that the numerical simulation results are in consistence with experimental data. Numerical and experimental results all show that the length and diameter of supercavity in drag-reducing solution are larger than those in water, and the drag coefficient is smaller than that in water; the maintaining time of supercavity is longer in solution as well. The surface tension plays an important role in maintaining the cavity. Turbulent drag-reducing additives have the potential in enhancement of supercavitation and drag reduction.

  7. Granular drag and the kinetics of jamming

    Science.gov (United States)

    Brzinski, Theodore A., III

    The first part of this thesis focuses on the study of the force exerted by a granular packing on an intruder. During impact, this force can be described by the linear combination of an inertial drag and a rate-independent frictional force that is proportional to depth. We measure the torque acting on a rod rotated perpendicular to its axis in a granular bed at steady state, and demonstrate that the resisting force is of the same form, though smaller. We then alter the hydrostatic loading on the bed by generating a homogenized airflow through the bed, and show that for horizontal motion the frictional force is due to friction acting at gravity-loaded contacts. Next we directly measure the force acting on quasistatically, vertically lowered intruders under two sets of varied conditions. First we vary the shape of the projectile in order to alter the fraction of the projectile surface that moves parallel vs perpendicular to the medium, and find that the frictional force acts primarily normal to the intruder surface. Second, we alter the hydrostatic loading as above, and confirm that gravity-loading of the grains sets the magnitude of the resisting force for quasi-static vertical motion as well. Finally, we consider the case of impact onto wet grains. We conduct conventional impact experiments wherein a spherical projectile impacts onto a granular packing with a known impact speed. We vary the liquid, impact speed, and degree of saturation, and find that the penetration depth is decreased for all wetting fractions, and that the penetration depth has a non-monotonic dependence on liquid saturation. In the fully saturated case, we recover the same scaling of penetration depth with geometry, impact speed and packing density as in the dry case, though the penetrations are shallower, suggesting a hydrodynamic contribution to the net stopping force. The second part of this thesis focuses on the kinetics of the jamming transition. In particular, we observe a dispersion of

  8. Design of Low Drag Bluff Road Vehicles

    NARCIS (Netherlands)

    Van Raemdonck, G.M.R.

    2012-01-01

    Low drag bluff road vehicle design can be obtained effectively and efficiently with a three phase approach that uses numerical simulations, scaled wind tunnel experiments and full-scale road testing. By applying this generalised method, SideWings were developed for an improved trailer underbody flow

  9. Measurements of drag and flow over biofilm

    Science.gov (United States)

    Hartenberger, Joel; Gose, James W.; Perlin, Marc; Ceccio, Steven L.

    2017-11-01

    Microbial `slime' biofilms detrimentally affect the performance of every day systems from medical devices to large ocean-going vessels. In flow applications, the presence of biofilm typically results in a drag increase and may alter the turbulence in the adjacent boundary layer. Recent studies emphasize the severity of the drag penalty associated with soft biofouling and suggest potential mechanisms underlying the increase; yet, fundamental questions remain-such as the role played by compliance and the contribution of form drag to the overall resistance experienced by a fouled system. Experiments conducted on live biofilm and 3D printed rigid replicas in the Skin-Friction Flow Facility at the University of Michigan seek to examine these factors. The hydrodynamic performance of the biofilms grown on test panels was evaluated through pressure drop measurements as well as conventional and microscale PIV. High-resolution, 3D rigid replicas of select cases were generated via additive manufacturing using surface profiles obtained from a laser scanning system. Drag and flow measurements will be presented along with details of the growth process and the surface profile characterization method.

  10. Judicial civil procedure dragging out in Kosovo

    Directory of Open Access Journals (Sweden)

    Rrustem Qehaja

    2016-03-01

    Full Text Available This article tends to deal with one of the most worrying issues in the judicial system of Kosovo the problem of judicial civil procedure dragging out. The article analyses the reasons of these dragging outs of the judicial civil procedure focusing on the context of one of the basic procedural principles in civil procedure-the principle of economy or efficiency in the courts. Dragging out of civil procedure in Kosovo has put in question not only the basic principles of civil procedure, but it also challenges the general principles related to human rights and freedoms sanctioned not only by the highest legal act of the country, but also with international treaties. The article tends to give a reflection to the most important reasons that effect and influence in these dragging outs of civil procedure, as well as, at the same time aims to give the necessary alternatives to pass through them by identifying dilemmas within the judicial practice. As a result, the motives of this scientific paper are exactly focused at the same time on identifying the dilemmas, as well as presenting ideas, to overstep them, including the judicial practice of the European Court of Human Rights on Article 6 of the European Convention on Human Rights, by which it is given the possibility to offering people efficient and within a reasonable time legal protection of their rights before national courts. For these reasons, the paper elaborates this issue based on both, the legal theory and judicial practice.

  11. Coulomb drag in the mesoscopic regime

    DEFF Research Database (Denmark)

    Mortensen, N. Asger; Flensberg, Karsten; Jauho, Antti-Pekka

    2002-01-01

    We present a theory for Coulomb drug between two mesoscopic systems which expresses the drag in terms of scattering matrices and wave functions. The formalism can be applied to both ballistic and disordered systems and the consequences can be studied either by numerical simulations or analytic...

  12. Factors associated with mosquito net use by individuals in households owning nets in Ethiopia

    Directory of Open Access Journals (Sweden)

    Graves Patricia M

    2011-12-01

    and young adults in rural areas, are crucial areas for intervention to ensure maximum net use and consequent reduction of malaria transmission.

  13. NA-NET numerical analysis net

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science]|[Oak Ridge National Lab., TN (United States); Rosener, B. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science

    1991-12-01

    This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host ``na-net.ornl.gov`` at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message ``send index`` to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user`s perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.

  14. NA-NET numerical analysis net

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science Oak Ridge National Lab., TN (United States)); Rosener, B. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science)

    1991-12-01

    This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host na-net.ornl.gov'' at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message send index'' to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user's perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.

  15. On the wind speed reduction in the center of large clusters of wind turbines

    DEFF Research Database (Denmark)

    Frandsen, Sten Tronæs

    1992-01-01

    of the wind speed assuming the wind turbines effectively act as roughness elements. The model makes use of similarities to so-called canopy flows, where the surface drag and the drag on individual obstacles are added to form the total drag. Results are compared with existing models for reduction of efficiency...

  16. 14 CFR 25.697 - Lift and drag devices, controls.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Lift and drag devices, controls. 25.697....697 Lift and drag devices, controls. (a) Each lift device control must be designed so that the pilots....101(d). Lift and drag devices must maintain the selected positions, except for movement produced by an...

  17. Drag Analysis from PIV Data in Speed Sports

    NARCIS (Netherlands)

    Terra, W.; Sciacchitano, A.; Scarano, F.

    2016-01-01

    Aerodynamic drag is computed from velocity measurements obtained with particle image velocimetry (PIV). This allows determining the drag force in combination with the visualization of the flow structures responsible for drag generation. Two experiments are conducted to illustrate the working

  18. Army Net Zero Prove Out. Army Net Zero Training Report

    Science.gov (United States)

    2014-11-20

    sensors were strategically placed throughout the installation by magnetically attaching them to water main valve stems. The sensors check sound...Recycle Wrap  Substitutes for Packaging Materials  Re-Use of Textiles and Linens  Setting Printers to Double-Sided Printing Net Zero Waste...can effectively achieve source reduction. Clean and Re-Use Shop Rags - Shop rags represent a large textile waste stream at many installations. As a

  19. Modification of Flow Structure Over a Van Model By Suction Flow Control to Reduce Aerodynamics Drag

    Directory of Open Access Journals (Sweden)

    Harinaldi Harinaldi

    2012-05-01

    Full Text Available Automobile aerodynamic studies are typically undertaken to improve safety and increase fuel efficiency as well as to  find new innovation in automobile technology to deal with the problem of energy crisis and global warming. Some car companies have the objective to develop control solutions that enable to reduce the aerodynamic drag of vehicle and  significant modification progress is still possible by reducing the mass, rolling friction or aerodynamic drag. Some flow  control method provides the possibility to modify the flow separation to reduce the development of the swirling structures around the vehicle. In this study, a family van is modeled with a modified form of Ahmed's body by changing the orientation of the flow from its original form (modified/reversed Ahmed body. This model is equipped with a suction on the rear side to comprehensively examine the pressure field modifications that occur. The investigation combines computational and experimental work. Computational approach used  a commercial software with standard k-epsilon flow turbulence model, and the objectives was  to determine the characteristics of the flow field and aerodynamic drag reduction that occurred in the test model. Experimental approach used load cell in order to validate the aerodynamic drag reduction obtained by computational approach. The results show that the application of a suction in the rear part of the van model give the effect of reducing the wake and the vortex formation. Futhermore, aerodynamic drag reduction close to 13.86% for the computational approach and 16.32% for the experimental have been obtained.

  20. Net Ecosystem Carbon Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Net Ecosystem Carbon Flux is defined as the year-over-year change in Total Ecosystem Carbon Stock, or the net rate of carbon exchange between an ecosystem and the...

  1. Delta method, an empirical drag buildup technique

    Science.gov (United States)

    Feagin, R. C.; Morrison, W. D.

    1978-01-01

    An empirical drag correlation technique was developed from analysis of 19 subsonic and supersonic military aircraft and 15 advanced or supercritical airfoil configurations which can be applied in conceptual and advanced aircraft design activities. The Delta Method may be used for estimating the clean wing drag polar for cruise and maneuver conditions up to buffet onset, and to approximately Mach 2.0. This technique incorporates a unique capability of predicting the off-design performance of advanced or supercritical airfoil sections. The buffet onset limit may also be estimated. The method is applicable to wind tunnel models as well as to full scale configurations. This technique has been converted into a computer code for use on the IBM 360 and CDC 7600 computer facilities at NASA AMES. Results obtained using this method to predict known aircraft characteristics are good and agreement can be obtained within a degree of accuracy judged to be sufficient for the initial processes of preliminary design.

  2. Switchable and Tunable Aerodynamic Drag on Cylinders

    Science.gov (United States)

    Guttag, Mark; Lopéz Jiménez, Francisco; Upadhyaya, Priyank; Kumar, Shanmugam; Reis, Pedro

    We report results on the performance of Smart Morphable Surfaces (Smporhs) that can be mounted onto cylindrical structures to actively reduce their aerodynamic drag. Our system comprises of an elastomeric thin shell with a series of carefully designed subsurface cavities that, once depressurized, lead to a dramatic deformation of the surface topography, on demand. Our design is inspired by the morphology of the giant cactus (Carnegiea gigantea) which possesses an array of axial grooves, thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. We perform systematic wind tunnel tests on cylinders covered with our Smorphs and characterize their aerodynamic performance. The switchable and tunable nature of our system offers substantial advantages for aerodynamic performance when compared to static topographies, due to their operation over a wider range of flow conditions.

  3. Stokes’ and Lamb's viscous drag laws

    Science.gov (United States)

    Eames, I.; Klettner, C. A.

    2017-03-01

    Since Galileo used his pulse to measure the time period of a swinging chandelier in the 17th century, pendulums have fascinated scientists. It was not until Stokes' (1851 Camb. Phil. Soc. 9 8-106) (whose interest was spurred by the pendulur time pieces of the mid 19th century) treatise on viscous flow that a theoretical framework for the drag on a sphere at low Reynolds number was laid down. Stokes' famous drag law has been used to determine two fundamental physical constants—the charge on an electron and Avogadro's constant—and has been used in theories which have won three Nobel prizes. Considering its illustrious history it is then not surprising that the flow past a sphere and its two-dimensional analog, the flow past a cylinder, form the starting point of teaching flow past a rigid body in undergraduate level fluid mechanics courses. Usually starting with the two-dimensional potential flow past a cylinder, students progress to the three-dimensional potential flow past a sphere. However, when the viscous flow past rigid bodies is taught, the three-dimensional example of a sphere is first introduced, and followed by (but not often), the two-dimensional viscous flow past a cylinder. The reason why viscous flow past a cylinder is generally not taught is because it is usually explained from an asymptotic analysis perspective. In fact, this added mathematical complexity is why the drag on a cylinder was only solved in 1911, 60 years after the drag on a sphere. In this note, we show that the viscous flow past a cylinder can be explained without the need to introduce any asymptotic analysis while still capturing all the physical insight of this classic fluid mechanics problem.

  4. Drag and Drop API v HTML5

    OpenAIRE

    BARABÁŠ, Vít

    2013-01-01

    The work (the bachelor´s thesis) deals with a new way of web application management via the "drag and drop" technique in the HTML5 programming language. The work is divided into two parts. The first part consists of DND API description in HTML5. The support analysis within common web browsers is included as a part of this description. The second, practical part of the thesis focuses on a concept and the following realisation of a photogallery using DND API.

  5. MEASUREMENT OF WIND DRAG FORCES ON TREES

    OpenAIRE

    Hiroyoshi, SHI-IGAI; Toru, Maruyama; Professor, Institute of Engineering Mechanics, University of Tsukuba; Engineer, Nissei Jushi Kogyo

    1988-01-01

    Trees have a lot of effects on soil conservation at mountainous regions. However, they often trigger land slides or mud avalanches if they cannot resist against strong winds, since the fallen trees may dam up mud and water and that natural dam eventually collapses, which triggers landslides. We developed a technique to estimate the total mass of trees in vivo and evaluated the wind force which acts on trees under natural conditions. The evaluated wind drag coefficients of trees whose height i...

  6. Optimal Projectile Shapes for Minimum Total Drag

    Science.gov (United States)

    1977-05-01

    distribltion UnlciI. I?, DIST RIBUION STATEMENT (0I the 4betrAVI M.4f*4 #A Dilo &O 1C It it*,ent~ Ifea He1.lot) ill SUPPLEMENTARY 40166 It. KtY WORDS...Exterior Ballistics Division. Released by: It. A. NIFMANN. Head Warf are Analysis Department Ui TABLE OF CONTENTS ACKNOWLED.IGUEMENT...I ANALYSIS ........................................... 2 DRAG..........................................- OP’TIMIZATION MI’TH

  7. Effect of wearing a swimsuit on hydrodynamic drag of swimmer

    Directory of Open Access Journals (Sweden)

    Daniel Almeida Marinho

    2012-12-01

    Full Text Available The purpose of this study was to analyse the effect of wearing a swimsuit on swimmer's passive drag. A computational fluid dynamics analysis was carried out to determine the hydrodynamic drag of a female swimmer's model (i wearing a standard swimsuit; (ii wearing a last generation swimsuit and; (iii with no swimsuit, wearing light underwear. The three-dimensional surface geometry of a female swimmer's model with different swimsuit/underwear was acquired through standard commercial laser scanner. Passive drag force and drag coefficient were computed with the swimmer in a prone position. Higher hydrodynamic drag values were determined when the swimmer was with no swimsuit in comparison with the situation when the swimmer was wearing a swimsuit. The last generation swimsuit presented lower hydrodynamic drag values, although very similar to standard swimsuit. In conclusion, wearing a swimsuit could positively influence the swimmer's hydrodynamics, especially reducing the pressure drag component.

  8. Drag-Free Control and Drag Force Recovery of Small Satellites

    Science.gov (United States)

    Nguyen, Anh N.; Conklin, John W.

    2017-01-01

    Drag-free satellites provide autonomous precision orbit determination, accurately map the static and time varying components of Earth's mass distribution, aid in our understanding of the fundamental force of gravity, and will ultimately open up a new window to our universe through the detection and observation of gravitational waves. At the heart of this technology is a gravitational reference sensor, which (a) contains and shields a free-floating proof mass from all non-gravitational forces, and (b) precisely measures the position of the test mass inside the sensor. Thus, both test mass and spacecraft follow a pure geodesic in spacetime. By tracking the position of a low Earth orbiting drag-free satellite we can directly determine the detailed shape of geodesics and through analysis, the higher order harmonics of the Earths geopotential. This paper explores two different drag-free control systems on small satellites. The first drag-free control system is a continuously compensated single thruster 3-unit CubeSat with a suspension-free spherical proof-mass. A feedback control system commands the thruster and Attitude and Determination Control System to fly the tender spacecraft with respect to the test mass. The spheres position is sensed with a LED-based differential optical shadow sensor, its electric charge controlled by photoemission using UV LEDs, and the spacecraft position is maintained with respect to the sphere using an ion electrospray propulsion system. This configuration is the most fuel-efficient drag-free system possible today. The second drag-free control system is an electro-statically suspended cubical proof-mass that is operated with a low duty cycle, limiting suspension force noise over brief, known time intervals on a small GRACE-II -like satellite. The readout is performed using a laser interferometer, which is immune to the dynamic range limitations of voltage references. This system eliminates the need for a thruster, enabling drag

  9. Professional Enterprise NET

    CERN Document Server

    Arking, Jon

    2010-01-01

    Comprehensive coverage to help experienced .NET developers create flexible, extensible enterprise application code If you're an experienced Microsoft .NET developer, you'll find in this book a road map to the latest enterprise development methodologies. It covers the tools you will use in addition to Visual Studio, including Spring.NET and nUnit, and applies to development with ASP.NET, C#, VB, Office (VBA), and database. You will find comprehensive coverage of the tools and practices that professional .NET developers need to master in order to build enterprise more flexible, testable, and ext

  10. Numerical Characterisation of Active Drag and Lift Control for a Circular Cylinder in Cross-Flow

    Directory of Open Access Journals (Sweden)

    Philip McDonald

    2017-11-01

    Full Text Available Synthetic jet actuators have shown promise to control drag and lift for a bluff body in cross-flow. Using unsteady RANS CFD modelling, a significant modification of the drag coefficient for a circular cylinder in cross-flow at R e = 3900 is achieved by varying the actuation frequency. The variation in actuation frequency corresponds to a range in Stokes number of 2.4 < S t o < 6.4. The trends in drag coefficient modification largely agree with the findings of past publications, achieving a maximum drag reduction at S t o = 4.9 for a fixed jet Reynolds number of the synthetic jet of R e U ¯ o = 12. A decrease in the adverse pressure gradient near the jet orifice correlated with a momentum increase in the viscous sublayer and stronger vortical structures at the rear of the cylinder. In these same conditions, a decrease in turbulence intensity was observed in the far field wake, which is a relevant finding in the context of wind and tidal turbine arrays.

  11. Self-determined shapes and velocities of giant near-zero drag gas cavities

    KAUST Repository

    Vakarelski, Ivan Uriev

    2017-09-09

    Minimizing the retarding force on a solid moving in liquid is the canonical problem in the quest for energy saving by friction and drag reduction. For an ideal object that cannot sustain any shear stress on its surface, theory predicts that drag force will fall to zero as its speed becomes large. However, experimental verification of this prediction has been challenging. We report the construction of a class of self-determined streamlined structures with this free-slip surface, made up of a teardrop-shaped giant gas cavity that completely encloses a metal sphere. This stable gas cavity is formed around the sphere as it plunges at a sufficiently high speed into the liquid in a deep tank, provided that the sphere is either heated initially to above the Leidenfrost temperature of the liquid or rendered superhydrophobic in water at room temperature. These sphere-in-cavity structures have residual drag coefficients that are typically less than Embedded Image those of solid objects of the same dimensions, which indicates that they experienced very small drag forces. The self-determined shapes of the gas cavities are shown to be consistent with the Bernoulli equation of potential flow applied on the cavity surface. The cavity fall velocity is not arbitrary but is uniquely predicted by the sphere density and cavity volume, so larger cavities have higher characteristic velocities.

  12. An investigation of the linear mechanisms in polymer drag-reduced turbulence using resolvent analysis

    Science.gov (United States)

    McMullen, Ryan; McKeon, Beverley

    2017-11-01

    It is well-known that small amounts of high-molecular weight polymers can drastically reduce turbulent drag in a liquid (Toms, 1948). Furthermore, recent work has shown that studying polymers in turbulence can shed light on the nature of the self-sustaining mechanisms of wall turbulence (White and Mungal, 2008; Graham, 2014). The focus of this talk is an investigation of the linear mechanisms at play in polymer drag-reduced turbulent channel flow. The resolvent framework introduced by McKeon and Sharma (2010) for Newtonian turbulence is extended to the viscoelastic case in order to study the most-amplified velocity and polymer stretching modes, explored in the case of creeping flow by Jovanović and coworkers (Jovanović and Kumar, 2010; Lieu et al., 2013). Particular attention is given to the role of critical layers, which have been shown to be important in the dynamics of Newtonian turbulence (McKeon and Sharma, 2010). Additionally, comparisons will be made with the lower branch of the P4 family of exact coherent states, which closely reproduce statistical features of polymer drag-reduced turbulence close to maximum drag reduction (Park and Graham, 2015). The support of the Dow Corporation is gratefully acknowledged.

  13. Gravitational Capture of Asteroids by Gas Drag

    Directory of Open Access Journals (Sweden)

    E. Vieira Neto

    2009-01-01

    captured by the planet got its velocity reduced and could been trapped as an irregular satellite. It is well known that, depending on the time scale of the gas envelope, an asteroid will spiral and collide with the planet. So, we simulate the passage of the asteroid in the gas envelope with its density decreasing along the time. Using this approach, we found effective captures, and have a better understanding of the whole process. Finally, we conclude that the origin of the irregular satellites cannot be attributed to the gas drag capture mechanism alone.

  14. WaveNet

    Science.gov (United States)

    2015-10-30

    Coastal Inlets Research Program WaveNet WaveNet is a web-based, Graphical-User-Interface ( GUI ) data management tool developed for Corps coastal...generates tabular and graphical information for project planning and design documents. The WaveNet is a web-based GUI designed to provide users with a...data from different sources, and employs a combination of Fortran, Python and Matlab codes to process and analyze data for USACE applications

  15. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt

    1991-01-01

    This paper describes how Coloured Petri Nets (CP-nets) have been developed — from being a promising theoretical model to being a full-fledged language for the design, specification, simulation, validation and implementation of large software systems (and other systems in which human beings and...... use of CP-nets — because it means that the function representation and the translations (which are a bit mathematically complex) no longer are parts of the basic definition of CP-nets. Instead they are parts of the invariant method (which anyway demands considerable mathematical skills...

  16. Game Coloured Petri Nets

    DEFF Research Database (Denmark)

    Westergaard, Michael

    2006-01-01

    This paper introduces the notion of game coloured Petri nets. This allows the modeler to explicitly model what parts of the model comprise the modeled system and what parts are the environment of the modeled system. We give the formal definition of game coloured Petri nets, a means of reachability...... analysis of this net class, and an application of game coloured Petri nets to automatically generate easy-to-understand visualizations of the model by exploiting the knowledge that some parts of the model are not interesting from a visualization perspective (i.e. they are part of the environment...

  17. Programming NET Web Services

    CERN Document Server

    Ferrara, Alex

    2007-01-01

    Web services are poised to become a key technology for a wide range of Internet-enabled applications, spanning everything from straight B2B systems to mobile devices and proprietary in-house software. While there are several tools and platforms that can be used for building web services, developers are finding a powerful tool in Microsoft's .NET Framework and Visual Studio .NET. Designed from scratch to support the development of web services, the .NET Framework simplifies the process--programmers find that tasks that took an hour using the SOAP Toolkit take just minutes. Programming .NET

  18. Annotating Coloured Petri Nets

    DEFF Research Database (Denmark)

    Lindstrøm, Bo; Wells, Lisa Marie

    2002-01-01

    -net. An example of such auxiliary information is a counter which is associated with a token to be able to do performance analysis. Modifying colour sets and arc inscriptions in a CP-net to support a specific use may lead to creation of several slightly different CP-nets – only to support the different uses...... a method which makes it possible to associate auxiliary information, called annotations, with tokens without modifying the colour sets of the CP-net. Annotations are pieces of information that are not essential for determining the behaviour of the system being modelled, but are rather added to support...

  19. Pressure loss reduction in hydrogen pipelines by surface restructuring

    Energy Technology Data Exchange (ETDEWEB)

    Peet, Y.; Sagaut, P. [Insitut Jean Le Rond d' Alembert, UMR CNRS 7190, Universite Pierre et Marie Curie - Paris 6, 4 place Jussieu - case 162, F-75252 Paris Cedex 5 (France); Charron, Y. [IFP- Institut Francais du Petrole, Rueil Malmaison Cedex, 92852 (France)

    2009-11-15

    This paper concerns the reduction of pressure losses during pipeline hydrogen transportation, as the cost of hydrogen compression is a significant obstacle for efficient hydrogen pumping on a large-scale basis. The use of organized micro-structures on pipeline walls is proposed to obtain lower values of pressure losses with respect to smooth walls. Three-dimensional micro-structures of a sinusoidal shape are investigated as potentially more efficient counterparts to conventional two-dimensional structures (riblets) developed in aerospace industry. Aerodynamic performance of three-dimensional structures is investigated computationally in terms of both skin friction and pressure drag, two constituents of the total drag. Three-dimensional structures are shown to provide larger total drag reduction than two-dimensional structures for some range of geometrical parameters (14.5% versus 11%). Parametric dependence of both pressure and skin friction drag on structure geometry is analyzed, and an optimum configuration maximizing the total drag reduction is proposed. (author)

  20. Air Flows in Gravity Sewers - Determination of Wastewater Drag Coefficient

    DEFF Research Database (Denmark)

    Bentzen, Thomas Ruby; Østertoft, Kristian; Vollertsen, Jes

    2016-01-01

    surface drags were found by log-law models of the velocity distribution in turbulent flows to fit velocity profiles measured from the water surface and by integrating the water surface drags along the wetted perimeter, mean water surface drags were found and a measure of the water surface drag coefficient...... of the study shows that by integrating the top/side wall shear stresses the log-law models for the air velocity distribution along the unwetted perimeter resulted in a good agreement with the friction forces calculated by use of the Colebrook-White formula for hydraulic smooth pipes. Secondly, the water...

  1. On the backreaction of frame dragging

    CERN Document Server

    Herdeiro, Carlos A R; Warnick, Claude M

    2009-01-01

    The backreaction on black holes due to dragging heavy, rather than test, objects is discussed. As a case study, a regular black Saturn system where the central black hole has vanishing intrinsic angular momentum, J^{BH}=0, is considered. It is shown that there is a correlation between the sign of two response functions. One is interpreted as a moment of inertia of the black ring in the black Saturn system. The other measures the variation of the black ring horizon angular velocity with the central black hole mass, for fixed ring mass and angular momentum. The two different phases defined by these response functions collapse, for small central black hole mass, to the thin and fat ring phases. In the fat phase, the zero area limit of the black Saturn ring has reduced spin j^2>1, which is related to the behaviour of the ring angular velocity. Using the `gravitomagnetic clock effect', for which a universality property is exhibited, it is shown that frame dragging measured by an asymptotic observer decreases, in b...

  2. Net zero water

    CSIR Research Space (South Africa)

    Lindeque, M

    2013-01-01

    Full Text Available Is it possible to develop a building that uses a net zero amount of water? In recent years it has become evident that it is possible to have buildings that use a net zero amount of electricity. This is possible when the building is taken off...

  3. SolNet

    DEFF Research Database (Denmark)

    Jordan, Ulrike; Vajen, Klaus; Bales, Chris

    2014-01-01

    SolNet, founded in 2006, is the first coordinated International PhD education program on Solar Thermal Engineering. The SolNet network is coordinated by the Institute of Thermal Engineering at Kassel University, Germany. The network offers PhD courses on solar heating and cooling, conference...

  4. Kunstige neurale net

    DEFF Research Database (Denmark)

    Hørning, Annette

    1994-01-01

    Artiklen beskæftiger sig med muligheden for at anvende kunstige neurale net i forbindelse med datamatisk procession af naturligt sprog, specielt automatisk talegenkendelse.......Artiklen beskæftiger sig med muligheden for at anvende kunstige neurale net i forbindelse med datamatisk procession af naturligt sprog, specielt automatisk talegenkendelse....

  5. Compliant wall-turbulent skin-friction reduction research

    Science.gov (United States)

    Fischer, M. C.; Weinstein, L. M.; Bushnell, D. M.; Ash, R. L.

    1975-01-01

    Previous compliant-wall experiments successful in reducing skin-friction drag probably have had a (unplanned) membrane resonance at a favorable frequency, amplitude, wave shape, length, and speed. The most probable drag reduction mechanism involves a direct coupling between the fluid and the moving wall when the wall natural resonance frequencies are near the fundamental turbulent burst frequency. Local skin-friction reductions of 61% were measured with mylar/PVC plastisol compliant surfaces. These reductions were observed only at certain flow conditions, indicating that changing tunnel total temperature may have altered the substrate dynamic modulus, damping, and coupled mylar tension. Apparently, the coupled membrane/substrate must be excited in compatible narrow-band natural frequency modes. An accelerated effort is required to develop practical durable compliant surfaces optimized for maximum drag reduction. Application of compliant walls to other transportation modes appears feasible with liquid flows offering the greatest skin-friction drag reduction potential.

  6. Spin-transfer mechanism for magnon-drag thermopower

    NARCIS (Netherlands)

    Lucassen, M.E.|info:eu-repo/dai/nl/314406913; Wong, C.H.; Duine, R.A.|info:eu-repo/dai/nl/304830127; Tserkovnyak, Y.

    2011-01-01

    We point out a relation between the dissipative spin-transfer-torque parameter β and the contribution of magnon drag to the thermoelectric power in conducting ferromagnets. Using this result, we estimate β in iron at low temperatures, where magnon drag is believed to be the dominant contribution to

  7. 14 CFR 25.699 - Lift and drag device indicator.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Lift and drag device indicator. 25.699 Section 25.699 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION....699 Lift and drag device indicator. (a) There must be means to indicate to the pilots the position of...

  8. Dancing droplets: Contact angle, drag, and confinement

    Science.gov (United States)

    Benusiglio, Adrien; Cira, Nate; Prakash, Manu

    2015-11-01

    When deposited on a clean glass slide, a mixture of water and propylene glycol forms a droplet of given contact angle, when both pure liquids spread. (Cira, Benusiglio, Prakash: Nature, 2015). The droplet is stabilized by a gradient of surface tension due to evaporation that induces a Marangoni flow from the border to the apex of the droplets. The apparent contact angle of the droplets depends on both their composition and the external humidity as captured by simple models. These droplets present remarkable properties such as lack of a large pinning force. We discuss the drag on these droplets as a function of various parameters. We show theoretical and experimental results of how various confinement geometries change the vapor gradient and the dynamics of droplet attraction.

  9. LISA Pathfinder as a drag-free accelerometer powered thrust stand

    Science.gov (United States)

    Slutsky, Jacob; LISA Pathfinder Team

    2017-01-01

    The LISA Pathfinder (LPF) mission, launched to demonstrate technology for a future gravitational wave observatory in space, began in March 2016. ESA led, LPF is comprised of both European and NASA payloads, the LISA Technology Package (LTP) and Disturbance Reduction System (DRS), respectively. The LTP includes the two highest precision drag free accelerometers ever flown, as well as a high precision interferometer. DRS provides the Colloid Micro-Newton Thruster (CMNT) system, required to precisely maneuver the spacecraft. Additionally, DRS includes a complete Dynamic Control System (DCS) that maintains the drag free flight. While the LTP mission uses the residual of the differential acceleration between the accelerometers, each individual sensor provides an unparalleled measure of the full six-dimensional spacecraft motion. This talk will discuss the DRS experiments performed, and how this sensor data is analyzed to characterize the noise and performance of the CMNTs.

  10. Mars entry guidance based on an adaptive reference drag profile

    Science.gov (United States)

    Liang, Zixuan; Duan, Guangfei; Ren, Zhang

    2017-08-01

    The conventional Mars entry tracks a fixed reference drag profile (FRDP). To improve the landing precision, a novel guidance approach that utilizes an adaptive reference drag profile (ARDP) is presented. The entry flight is divided into two phases. For each phase, a family of drag profiles corresponding to various trajectory lengths is planned. Two update windows are investigated for the reference drag profile. At each window, the ARDP is selected online from the profile database according to the actual range-to-go. The tracking law for the selected drag profile is designed based on the feedback linearization. Guidance approaches using the ARDP and the FRDP are then tested and compared. Simulation results demonstrate that the proposed ARDP approach achieves much higher guidance precision than the conventional FRDP approach.

  11. Pro NET Best Practices

    CERN Document Server

    Ritchie, Stephen D

    2011-01-01

    Pro .NET Best Practices is a practical reference to the best practices that you can apply to your .NET projects today. You will learn standards, techniques, and conventions that are sharply focused, realistic and helpful for achieving results, steering clear of unproven, idealistic, and impractical recommendations. Pro .NET Best Practices covers a broad range of practices and principles that development experts agree are the right ways to develop software, which includes continuous integration, automated testing, automated deployment, and code analysis. Whether the solution is from a free and

  12. Getting to Net Zero

    Energy Technology Data Exchange (ETDEWEB)

    2016-09-01

    The technology necessary to build net zero energy buildings (NZEBs) is ready and available today, however, building to net zero energy performance levels can be challenging. Energy efficiency measures, onsite energy generation resources, load matching and grid interaction, climatic factors, and local policies vary from location to location and require unique methods of constructing NZEBs. It is recommended that Components start looking into how to construct and operate NZEBs now as there is a learning curve to net zero construction and FY 2020 is just around the corner.

  13. Instant Lucene.NET

    CERN Document Server

    Heydt, Michael

    2013-01-01

    Filled with practical, step-by-step instructions and clear explanations for the most important and useful tasks. A step-by-step guide that helps you to index, search, and retrieve unstructured data with the help of Lucene.NET.Instant Lucene.NET How-to is essential for developers new to Lucene and Lucene.NET who are looking to get an immediate foundational understanding of how to use the library in their application. It's assumed you have programming experience in C# already, but not that you have experience with search techniques such as information retrieval theory (although there will be a l

  14. Aerodynamic drag modeling of alpine skiers performing giant slalom turns.

    Science.gov (United States)

    Meyer, Frédéric; Le Pelley, David; Borrani, Fabio

    2012-06-01

    Aerodynamic drag plays an important role in performance for athletes practicing sports that involve high-velocity motions. In giant slalom, the skier is continuously changing his/her body posture, and this affects the energy dissipated in aerodynamic drag. It is therefore important to quantify this energy to understand the dynamic behavior of the skier. The aims of this study were to model the aerodynamic drag of alpine skiers in giant slalom simulated conditions and to apply these models in a field experiment to estimate energy dissipated through aerodynamic drag. The aerodynamic characteristics of 15 recreational male and female skiers were measured in a wind tunnel while holding nine different skiing-specific postures. The drag and the frontal area were recorded simultaneously for each posture. Four generalized and two individualized models of the drag coefficient were built, using different sets of parameters. These models were subsequently applied in a field study designed to compare the aerodynamic energy losses between a dynamic and a compact skiing technique. The generalized models estimated aerodynamic drag with an accuracy of between 11.00% and 14.28%, and the individualized models estimated aerodynamic drag with an accuracy between 4.52% and 5.30%. The individualized model used for the field study showed that using a dynamic technique led to 10% more aerodynamic drag energy loss than using a compact technique. The individualized models were capable of discriminating different techniques performed by advanced skiers and seemed more accurate than the generalized models. The models presented here offer a simple yet accurate method to estimate the aerodynamic drag acting upon alpine skiers while rapidly moving through the range of positions typical to turning technique.

  15. Bag-breakup control of surface drag in hurricanes

    Science.gov (United States)

    Troitskaya, Yuliya; Zilitinkevich, Sergej; Kandaurov, Alexander; Ermakova, Olga; Kozlov, Dmitry; Sergeev, Daniil

    2016-04-01

    Air-sea interaction at extreme winds is of special interest now in connection with the problem of the sea surface drag reduction at the wind speed exceeding 30-35 m/s. This phenomenon predicted by Emanuel (1995) and confirmed by a number of field (e.g., Powell, et al, 2003) and laboratory (Donelan et al, 2004) experiments still waits its physical explanation. Several papers attributed the drag reduction to spume droplets - spray turning off the crests of breaking waves (e.g., Kudryavtsev, Makin, 2011, Bao, et al, 2011). The fluxes associated with the spray are determined by the rate of droplet production at the surface quantified by the sea spray generation function (SSGF), defined as the number of spray particles of radius r produced from the unit area of water surface in unit time. However, the mechanism of spume droplets' formation is unknown and empirical estimates of SSGF varied over six orders of magnitude; therefore, the production rate of large sea spray droplets is not adequately described and there are significant uncertainties in estimations of exchange processes in hurricanes. Herewith, it is unknown what is air-sea interface and how water is fragmented to spray at hurricane wind. Using high-speed video, we observed mechanisms of production of spume droplets at strong winds by high-speed video filming, investigated statistics and compared their efficiency. Experiments showed, that the generation of the spume droplets near the wave crest is caused by the following events: bursting of submerged bubbles, generation and breakup of "projections" and "bag breakup". Statistical analysis of results of these experiments showed that the main mechanism of spray-generation is attributed to "bag-breakup mechanism", namely, inflating and consequent blowing of short-lived, sail-like pieces of the water-surface film. Using high-speed video, we show that at hurricane winds the main mechanism of spray production is attributed to "bag-breakup", namely, inflating and

  16. Net Zero Energy Buildings

    DEFF Research Database (Denmark)

    Marszal, Anna Joanna; Bourrelle, Julien S.; Musall, Eike

    2010-01-01

    and identify possible renewable energy supply options which may be considered in calculations. Finally, the gap between the methodology proposed by each organisation and their respective national building code is assessed; providing an overview of the possible changes building codes will need to undergo......The international cooperation project IEA SHC Task 40 / ECBCS Annex 52 “Towards Net Zero Energy Solar Buildings”, attempts to develop a common understanding and to set up the basis for an international definition framework of Net Zero Energy Buildings (Net ZEBs). The understanding of such buildings...... parameters used in the calculations are discussed and the various renewable supply options considered in the methodologies are summarised graphically. Thus, the paper helps to understand different existing approaches to calculate energy balance in Net ZEBs, highlights the importance of variables selection...

  17. PhysioNet

    Data.gov (United States)

    U.S. Department of Health & Human Services — The PhysioNet Resource is intended to stimulate current research and new investigations in the study of complex biomedical and physiologic signals. It offers free...

  18. NetSig

    DEFF Research Database (Denmark)

    Horn, Heiko; Lawrence, Michael S; Chouinard, Candace R

    2018-01-01

    Methods that integrate molecular network information and tumor genome data could complement gene-based statistical tests to identify likely new cancer genes; but such approaches are challenging to validate at scale, and their predictive value remains unclear. We developed a robust statistic (Net......Sig) that integrates protein interaction networks with data from 4,742 tumor exomes. NetSig can accurately classify known driver genes in 60% of tested tumor types and predicts 62 new driver candidates. Using a quantitative experimental framework to determine in vivo tumorigenic potential in mice, we found that Net......Sig candidates induce tumors at rates that are comparable to those of known oncogenes and are ten-fold higher than those of random genes. By reanalyzing nine tumor-inducing NetSig candidates in 242 patients with oncogene-negative lung adenocarcinomas, we find that two (AKT2 and TFDP2) are significantly amplified...

  19. TideNet

    Science.gov (United States)

    2015-10-30

    query tide data sources in a desired geographic region of USA and its territories (Figure 1). Users can select a tide data source through the Google Map ...select data sources according to the desired geographic region. It uses the Google Map interface to display data from different sources. Recent...Coastal Inlets Research Program TideNet The TideNet is a web-based Graphical User Interface (GUI) that provides users with GIS mapping tools to

  20. Building Neural Net Software

    OpenAIRE

    Neto, João Pedro; Costa, José Félix

    1999-01-01

    In a recent paper [Neto et al. 97] we showed that programming languages can be translated on recurrent (analog, rational weighted) neural nets. The goal was not efficiency but simplicity. Indeed we used a number-theoretic approach to machine programming, where (integer) numbers were coded in a unary fashion, introducing a exponential slow down in the computations, with respect to a two-symbol tape Turing machine. Implementation of programming languages in neural nets turns to be not only theo...

  1. Interaction Nets in Russian

    OpenAIRE

    Salikhmetov, Anton

    2013-01-01

    Draft translation to Russian of Chapter 7, Interaction-Based Models of Computation, from Models of Computation: An Introduction to Computability Theory by Maribel Fernandez. "In this chapter, we study interaction nets, a model of computation that can be seen as a representative of a class of models based on the notion of 'computation as interaction'. Interaction nets are a graphical model of computation devised by Yves Lafont in 1990 as a generalisation of the proof structures of linear logic...

  2. Programming NET 35

    CERN Document Server

    Liberty, Jesse

    2009-01-01

    Bestselling author Jesse Liberty and industry expert Alex Horovitz uncover the common threads that unite the .NET 3.5 technologies, so you can benefit from the best practices and architectural patterns baked into the new Microsoft frameworks. The book offers a Grand Tour" of .NET 3.5 that describes how the principal technologies can be used together, with Ajax, to build modern n-tier and service-oriented applications. "

  3. Approximation methods for stochastic petri nets

    Science.gov (United States)

    Jungnitz, Hauke Joerg

    1992-01-01

    Stochastic Marked Graphs are a concurrent decision free formalism provided with a powerful synchronization mechanism generalizing conventional Fork Join Queueing Networks. In some particular cases the analysis of the throughput can be done analytically. Otherwise the analysis suffers from the classical state explosion problem. Embedded in the divide and conquer paradigm, approximation techniques are introduced for the analysis of stochastic marked graphs and Macroplace/Macrotransition-nets (MPMT-nets), a new subclass introduced herein. MPMT-nets are a subclass of Petri nets that allow limited choice, concurrency and sharing of resources. The modeling power of MPMT is much larger than that of marked graphs, e.g., MPMT-nets can model manufacturing flow lines with unreliable machines and dataflow graphs where choice and synchronization occur. The basic idea leads to the notion of a cut to split the original net system into two subnets. The cuts lead to two aggregated net systems where one of the subnets is reduced to a single transition. A further reduction leads to a basic skeleton. The generalization of the idea leads to multiple cuts, where single cuts can be applied recursively leading to a hierarchical decomposition. Based on the decomposition, a response time approximation technique for the performance analysis is introduced. Also, delay equivalence, which has previously been introduced in the context of marked graphs by Woodside et al., Marie's method and flow equivalent aggregation are applied to the aggregated net systems. The experimental results show that response time approximation converges quickly and shows reasonable accuracy in most cases. The convergence of Marie's method and flow equivalent aggregation are applied to the aggregated net systems. The experimental results show that response time approximation converges quickly and shows reasonable accuracy in most cases. The convergence of Marie's is slower, but the accuracy is generally better. Delay

  4. Characterization of aerodynamic drag force on single particles: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kale, S.R.

    1987-10-01

    An electrodynamic balance was used to measure the drag coefficient and also to record the size and shape of spheres, and coal and oil shale particles (100 ..mu..m to 200 ..mu..m in size). The electrodynamic balance consisted of a central, and two end electrodes. The resulting electric field stably suspended a charged particle. A suspended particle, back illuminated by a light emitting diode, was viewed by a video camera. The image was analyzed for particle position control and was calibrated to give the diameter of spheres, or the area equivalent diameter of nonspherical particles. The drag coefficient was calculated from the air velocity and the dc voltage required to keep the particle at the balance center. The particle Reynolds number varied from 0.2 to 13. Three particles each of coal and oil shale were captured and photographed by a scanning electron microscope and the motion of all the particles was recorded on video tape. Drag coefficient vs Reynolds number data for spheres agreed well with correlations. Data for thirteen particles each of coal and oil shale indicated a power law relationship between drag coefficient and Reynolds number. All these particles exhibited higher drag than spheres and were also observed to rotate. The rotation, however, did not affect the drag coefficient. The choice of characteristic dimension affects the drag characteristics of oil shale more strongly than for coal, owing to the flake-like shape of oil shale. 38 figs., 5 tabs.

  5. An Implementation of Nested Pattern Matching in Interaction Nets

    Directory of Open Access Journals (Sweden)

    Abubakar Hassan

    2010-03-01

    Full Text Available Reduction rules in interaction nets are constrained to pattern match exactly one argument at a time. Consequently, a programmer has to introduce auxiliary rules to perform more sophisticated matches. In this paper, we describe the design and implementation of a system for interaction nets which allows nested pattern matching on interaction rules. We achieve a system that provides convenient ways to express interaction net programs without defining auxiliary rules.

  6. Gas Drag on a Rotating Body with Gravity

    OpenAIRE

    Hidenori, TAKEDA; Yoshitsugu, NAKAGAWA; Department of Aeronautics and Astronautics, Faculty of Engineering Kyoto University; Department of Earth and Planetary Sciences, Faculty of Science Kobe University

    2000-01-01

    In growth processes of planetesimals and protoplanets, the gas drag on them plays important roles. It is interesting to study the gas flows around rotating celestial bodies with gravity, and it is important to evaluate the gas drag on those bodies from the viewpoint of planetary cosmogony. In order to understand the effects of the rotation and the gravity of such bodies on the gas drag and also to observe lift and torque, we performed three-dimensional numerical simulations for the flows arou...

  7. Surface modification of clutch plates to reduce disengaged drag torque

    Science.gov (United States)

    Aphale, Chinar R.

    2005-11-01

    Viscous drag torque in disengaged clutches is a significant source of power loss in modern transportation. The main way to reduce this drag torque is to introduce air between the plates when disengaged without reducing the transmission fluid flow eventually needed for reengagement. Six different groove patterns are tested experimentally to determine which have the lowest drag characteristics. Our computations using Fluent showed that the contact angle made by oil with the stationary plate is critical in determining aeration initiation. Experiments coating the stationary plate with an oleophobic substance like Teflon, confirmed these simulations. We will show torque comparisons and visualization through a quartz disk acting as one of the clutch plates.

  8. Frictional drag between quantum wells mediated by phonon exchange

    DEFF Research Database (Denmark)

    Bønsager, M.C.; Flensberg, Karsten; Hu, Ben Yu-Kuang

    1998-01-01

    lattice imperfections or electronic excitations is accounted for. In the case of GaAs quantum wells, we find that for a phonon mean free path l(ph) smaller than a critical value, imperfection scattering dominates and the drag rate varies as ln(l(ph)/d) over many orders of magnitude of the layer separation......We use the Kubo formalism to evaluate the contribution of acoustic-phonon exchange to the frictional drag between nearby two-dimensional electron systems. In the case of free phonons, we find a divergent drag rate (tau(D)(-l)). However, tau(D)(-l) becomes finite when phonon scattering from either...

  9. Drag force scaling for penetration into granular media.

    Science.gov (United States)

    Katsuragi, Hiroaki; Durian, Douglas J

    2013-05-01

    Impact dynamics is measured for spherical and cylindrical projectiles of many different densities dropped onto a variety non-cohesive granular media. The results are analyzed in terms of the material-dependent scaling of the inertial and frictional drag contributions to the total stopping force. The inertial drag force scales similar to that in fluids, except that it depends on the internal friction coefficient. The frictional drag force scales as the square-root of the density of granular medium and projectile, and hence cannot be explained by the combination of granular hydrostatic pressure and Coulomb friction law. The combined results provide an explanation for the previously observed penetration depth scaling.

  10. Reducing the pressure drag of a D-shaped bluff body using linear feedback control

    Science.gov (United States)

    Dalla Longa, L.; Morgans, A. S.; Dahan, J. A.

    2017-12-01

    The pressure drag of blunt bluff bodies is highly relevant in many practical applications, including to the aerodynamic drag of road vehicles. This paper presents theory revealing that a mean drag reduction can be achieved by manipulating wake flow fluctuations. A linear feedback control strategy then exploits this idea, targeting attenuation of the spatially integrated base (back face) pressure fluctuations. Large-eddy simulations of the flow over a D-shaped blunt bluff body are used as a test-bed for this control strategy. The flow response to synthetic jet actuation is characterised using system identification, and controller design is via shaping of the frequency response to achieve fluctuation attenuation. The designed controller successfully attenuates integrated base pressure fluctuations, increasing the time-averaged pressure on the body base by 38%. The effect on the flow field is to push the roll-up of vortices further downstream and increase the extent of the recirculation bubble. This control approach uses only body-mounted sensing/actuation and input-output model identification, meaning that it could be applied experimentally.

  11. Gravitational quadrupolar coupling and center of gravity: application for Drag-Free Satellites

    Science.gov (United States)

    Guilherme, M. S.; Theil, S.

    The motivation of this work is the refinement of modelling of a Drag-Free Satellite DFS for improvement of the disturbance reduction system a so called Drag-Free Control DFC and for the improvement of the data analysis Drag-Free Satellites are missions on fundamental physics as well as geodesy They measure accelerations on a very small scale Especially for the satellites planned for fundamental physics the level of acceleration to be measured is in the range of 10e-15 to 10e-18 m s 2 Because of that any disturbance and misalignment should be modelled Due to the gravity gradient for most extended bodies the center of gravity deviates from the center of mass This results in a gravity gradient torque on satellites as well as on the test masses which depends on the attitude with respect to the gravity gradient In addition the gravity force is also attitude dependent This paper describes this gravity gradient force acting on arbitrary bodies for higher orders of the inertia moments It shows also the influence of the quadrupolar gravitational coupling to the Earth gravity field An equation is developed that determines the center of gravity in the body frame It provides a visualization of the deviation of the center of gravity from the center of mass In order to evaluate the significance of this effects values are computed for several fundamental physicals missions e g GRAVITY PROBE B and STEP

  12. Inflight Performance of Cassini Reaction Wheel Bearing Drag in 1997-2013

    Science.gov (United States)

    Lee, Allan Y.; Wang, Eric K.

    2013-01-01

    As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended missions through September 2017. Cassini is a three-axis stabilized spacecraft. It uses reaction wheels to achieve high level of spacecraft pointing stability that is needed during imaging operations of several science instruments. The Cassini flight software makes in-flight estimates of reaction wheel bearing drag torque and made them available to the mission operations team. These telemetry data are being trended for the purpose of monitoring the long-term health of the reaction wheel bearings. Anomalous drag torque signatures observed over the past 15 years are described in this paper. One of these anomalous drag conditions is bearing cage instability that appeared (and disappeared) spontaneously and unpredictably. Cage instability is an uncontrolled vibratory motion of the bearing cage that can produce high-impact forces internal to the bearing that will cause intermittent and erratic torque transients. Characteristics of the observed cage instabilities and other drag torque "spikes" are described in this paper. In day-to-day operations, the reaction wheels' rates must be neither too high nor too low. To protect against operating the wheels in any undesirable conditions (such as prolonged low spin rate operations), a ground software tool named Reaction Wheel Bias Optimization Tool (RBOT) was developed for the management of the wheels. Disciplined and long-term use of this ground software has led to significant reduction in the daily consumption rate of the wheels' low spin rate dwell time. Flight experience on the use of this ground software tool as well as other lessons learned on the management of Cassini reaction wheels is given in this paper.

  13. Turbulent and Transitional Modeling of Drag on Oceanographic Measurement Devices

    Directory of Open Access Journals (Sweden)

    J. P. Abraham

    2012-01-01

    Full Text Available Computational fluid dynamic techniques have been applied to the determination of drag on oceanographic devices (expendable bathythermographs. Such devices, which are used to monitor changes in ocean heat content, provide information that is dependent on their drag coefficient. Inaccuracies in drag calculations can impact the estimation of ocean heating associated with global warming. Traditionally, ocean-heating information was based on experimental correlations which related the depth of the device to the fall time. The relation of time-depth is provided by a fall-rate equation (FRE. It is known that FRE depths are reasonably accurate for ocean environments that match the experiments from which the correlations were developed. For other situations, use of the FRE may lead to depth errors that preclude XBTs as accurate oceanographic devices. Here, a CFD approach has been taken which provides drag coefficients that are used to predict depths independent of an FRE.

  14. Dizziness Can Be a Drag: Coping with Balance Disorders

    Science.gov (United States)

    ... Issues Subscribe August 2012 Print this issue Dizziness Can Be a Drag Coping with Balance Disorders Send ... enough to send them to a doctor. Dizziness can range from feeling lightheaded to woozy to disoriented. ...

  15. Drag force and jet propulsion investigation of a swimming squid

    Directory of Open Access Journals (Sweden)

    Tabatabaei Mahdi

    2015-01-01

    Full Text Available In this study, CAD model of a squid was obtained by taking computer tomography images of a real squid. The model later placed into a computational domain to calculate drag force and performance of jet propulsion. The drag study was performed on the CAD model so that drag force subjected to real squid was revealed at squid’s different swimming speeds and comparison has been made with other underwater creatures (e.g., a dolphin, sea lion and penguin. The drag coefficient (referenced to total wetted surface area of squid is 0.0042 at Reynolds number 1.6x106 that is a %4.5 difference from Gentoo penguin. Besides, jet flow of squid was simulated to observe the flow region generated in the 2D domain utilizing dynamic mesh method to mimic the movement of squid’s mantle cavity.

  16. Drag Force in a Gas Fluidized Granular Bed

    Science.gov (United States)

    Brzinski, T. A.; Durian, D. J.

    2008-03-01

    We use a rheometer to measure the torque acting on a rotating bar in a bed of gas-fluidized glass beads. We vary rotation rate from .001-10rps, vary depth from 1-10 cm, and increase the fluidizing gas flow from no flow well into the fluidized regime. We observe that at high rotation rates the drag is roughly proportional to velocity squared. At low rates we can rescale the measured torque by depth, and observe a collapse of the data. These results agree with the predictions of a granular drag force model which has proven effective in predicting granular impact dynamics. The model consists of an inertial drag term, which is depth-independent and scales as velocity squared, and a frictional drag term, which is independent of rate and varies linearly with depth. We find, as expected, that while the frictional term is airflow-dependent the inertial term is uncoupled from the fluidization.

  17. Shell selection of hermit crabs is influenced by fluid drag

    Science.gov (United States)

    Casillas, Barbara; Ledesma, Rene; Alcaraz, Guillermina; Zenit, Roberto

    2010-11-01

    The flow around gastropod shells used by hermit crabs (Calcinus californiensis) was visualized experimentally. These crabs choose their shells according to many factors; we found that the choice of shell (shape and weight) is directly related to the drag caused over them by the exposure to wave action. Tests were conducted in a wind tunnel to investigate flow differences for shells of various shapes. A particle image velocimetry (PIV) system was used to visualize the flow field. The images above show the flow field around two types of shells (Thais speciosa and Nerita scabircosta) for Reynolds numbers of O(10^5). Using a control volume analysis, the drag coefficient was inferred. Several shell geometries, orientations and mean flow velocities were tested. In this talk, the flow and drag force will be shown for the different arrangements. A discussion of the relation between drag and shape will be presented.

  18. La plataforma .NET

    OpenAIRE

    Fornas Estrada, Miquel

    2008-01-01

    L'aparició de la plataforma .NET Framework ha suposat un canvi molt important en la forma de crear i distribuir aplicacions, degut a que incorpora una sèrie d'innovacions tècniques i productives que simplifiquen molt les tasques necessàries per desenvolupar un projecte. La aparición de la plataforma. NET Framework ha supuesto un cambio muy importante en la forma de crear y distribuir aplicaciones, debido a que incorpora una serie de innovaciones técnicas y productivas que simplifican mucho...

  19. Biological Petri Nets

    CERN Document Server

    Wingender, E

    2011-01-01

    It was suggested some years ago that Petri nets might be well suited to modeling metabolic networks, overcoming some of the limitations encountered by the use of systems employing ODEs (ordinary differential equations). Much work has been done since then which confirms this and demonstrates the usefulness of this concept for systems biology. Petri net technology is not only intuitively understood by scientists trained in the life sciences, it also has a robust mathematical foundation and provides the required degree of flexibility. As a result it appears to be a very promising approach to mode

  20. Frame dragging in black hole-pulsar binaries

    OpenAIRE

    Wex, N.

    1999-01-01

    The discovery of frame-dragging effects in binary pulsar timing experiments requires a compact companion with sufficiently large spin. A pulsar orbiting a fast rotating black hole could provide an appropriate test system. In this paper we address questions concerning the identification of a black hole companion in such a system, the measurability of the frame dragging caused by the rotation of the black hole, and the measurability of the quadrupole moment, which would prove the presence of a ...

  1. Sensitivity analysis of factors affecting torque and drag modelling

    OpenAIRE

    Hashmi, Muhammad Jahanzeb

    2014-01-01

    Master's thesis in Petroleum engineering *KAR OK KONF 2016* As the modern day extended reached wells are getting longer and more complex, the torque and drag is one of the restraining aspects for achieving the target depth. Torque and drag becomes a precarious issue, for example it can be difficult to land the long completion string. Therefore, understanding the friction in the wellbore and how it affects hook load and torque is essential for well path design in planning phase as well ...

  2. Drag force in a charged N = 4 SYM plasma

    Energy Technology Data Exchange (ETDEWEB)

    Caceres, Elena [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima (Mexico); Gueijosa, Alberto [Departamento de Fisica de Altas Energias, Instituto de Ciencias Nucleares, Universidad Autonoma de Mexico, Apdo. Postal 70-543, D.F. 04510 (Mexico)

    2006-11-15

    Following recent developments, we employ the AdS/CFT correspondence to determine the drag force exerted on an external quark that moves through an N = 4 super-Yang-Mills plasma with a non-zero R-charge density (or, equivalently, a non-zero chemical potential). We find that the drag force is larger than in the case where the plasma is neutral, but the dependence on the charge is non-monotonic.

  3. Experimental investigation of frictional resistance reduction with air layer on the hull bottom of a ship

    Directory of Open Access Journals (Sweden)

    Jinho Jang

    2014-06-01

    Full Text Available In an effort to cope with recent high oil price and global warming, developments of air lubricated ships have been pursued to reduce greenhouse gas emissions and to save fuel costs by reducing the frictional resistance. In this study, reduction in the frictional resistance by air lubrication with air layers generated on the lower surface of a flat plate was investigated experimentally in the large water tunnel of SSMB. The generated air layers were observed, and changes in the local frictional drag were measured at various flow rates of injected air. The results indicated that air lubrication with air layers might be useful in reducing the frictional resistance at specific conditions of air injection. Accordingly, resistance and self-propulsion tests for a 66K DWT bulk carrier were carried out in the towing tank of SSMB to estimate the expected net power savings.

  4. Aerodynamic drag of modern soccer balls.

    Science.gov (United States)

    Asai, Takeshi; Seo, Kazuya

    2013-12-01

    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 a wind tunnel test and ball trajectory simulations, this study shows that the aerodynamic resistance of the new 32-panel soccer ball is larger in the high-speed region and lower in the middle-speed region than that of the previous 14- and 8-panel balls. The critical Reynolds number of the Roteiro, Teamgeist II, Jabulani, and Tango 12 was ~2.2 × 10(5) (drag coefficient, C d  ≈ 0.12), ~2.8 × 10(5) (C d  ≈ 0.13), ~3.3 × 10(5) (C d  ≈ 0.13), and ~2.4 × 10(5) (C d  ≈ 0.15), respectively. The flight trajectory simulation suggested that the Tango 12, one of the newest soccer balls, has less air resistance in the medium-speed region than the Jabulani and can thus easily acquire large initial velocity in this region. It is considered that the critical Reynolds number of a soccer ball, as considered within the scope of this experiment, depends on the extended total distance of the panel bonds rather than the small designs on the panel surfaces.

  5. Petri Nets-Applications

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 9. Petri Nets - Applications. Y Narahari. General Article Volume 4 Issue 9 September 1999 pp 44-52. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/004/09/0044-0052. Author Affiliations. Y Narahari ...

  6. Safety nets or straitjackets?

    DEFF Research Database (Denmark)

    Ilsøe, Anna

    2012-01-01

    Does regulation of working hours at national and sector level impose straitjackets, or offer safety nets to employees seeking working time flexibility? This article compares legislation and collective agreements in the metal industries of Denmark, Germany and the USA. The industry has historically...

  7. Coloured Petri Nets

    CERN Document Server

    Jensen, Kurt

    2009-01-01

    Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. This book introduces the constructs of the CPN modelling language and presents the related analysis methods. It provides a comprehensive road map for the practical use of CPN.

  8. Boom Booom Net Radio

    DEFF Research Database (Denmark)

    Grimshaw, Mark Nicholas; Yong, Louisa; Dobie, Ian

    1999-01-01

    of an existing Internet radio station; Boom Booom Net Radio. Whilst necessity dictates some use of technology-related terminology, wherever possible we have endeavoured to keep such jargon to a minimum and to either explain it in the text or to provide further explanation in the appended glossary....

  9. Game Theory .net.

    Science.gov (United States)

    Shor, Mikhael

    2003-01-01

    States making game theory relevant and accessible to students is challenging. Describes the primary goal of GameTheory.net is to provide interactive teaching tools. Indicates the site strives to unite educators from economics, political and computer science, and ecology by providing a repository of lecture notes and tests for courses using…

  10. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kristensen, Lars Michael

    Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism...

  11. Experimental evaluation of the drag torque, drag force and Magnus force acting on a rotating prolate spheroid

    OpenAIRE

    Lukerchenko, Nikolay

    2010-01-01

    The drag torque, drag force and Magnus force acting on a spheroid rotating around its axis of symmetry and moving perpendicularly to this axis in initially quiescent water were studied using experimental data and numerical simulation. The prolate spheroid with ratio of the axes 4/3 was speeded up in special device, which ensured the required rotational and translational velocity in the given plane. A video system was used to record the spheroid motion in water. Using the video records the sph...

  12. Experimental investigation of drag force, Magnus force and drag torque acting on rough sphere moving in calm water

    OpenAIRE

    Lukerchenko, Nikolay

    2010-01-01

    The paper describes the results of experiments with a rotating golf ball moving quasi-steadily in calm water. The motion of the ball was recorded on a digital video camera. The dimensionless drag force, Magnus force, and drag torque coefficients were determined from the comparison of the calculated translational and angular velocities and trajectory with experimental ones for the rough particle. The proper value of the correction coefficients were established from condition of the best fittin...

  13. Token-passing Optimal Reduction with Embedded Read-back

    Directory of Open Access Journals (Sweden)

    Anton Salikhmetov

    2016-09-01

    Full Text Available We introduce a new interaction net implementation of optimal reduction for the pure untyped lambda calculus. Unlike others, our implementation allows to reach normal form regardless of the interaction net reduction strategy using the approach of so-called token-passing nets and a non-deterministic extension for interaction nets. Another new feature is the read-back mechanism implemented without leaving the formalism of interaction nets.

  14. A concept design of three rudders-shaped like body in columns for low-drag USV

    Science.gov (United States)

    Azzeri, M. N.; Adnan, F. A.; Adi, M.; Zain, M. Z. Md

    2016-06-01

    This paper presented a new design for the unmanned surface vessel (USV) platform with a self-manoeuvring system which is capable of collecting the same data as a hydrography boat. This platform was designed with three hulls that were placed in triangle position. The hulls designed were in the form of rudders-shape and were vertically placed as a slender body shape using NACA 64-0012 profile. This provides the USV with low-drag characteristic. The application of stability and resistance theories investigated the effect of the configuration position of the three hulls for this platform. The results revealed that a larger configuration distance between the three hulls will lead to a reduction in resistance and the platform will be in highly stable condition. The relationships derived from these findings should produce a stable and low-drag platform to accomplish the design concept of three rudders-shaped like body in columns for low-drag USV. This concept may help us to accomplish the design requirements that are related to low-drag and minimum power operation.

  15. Nation Drag: Uses of the Exotic

    Directory of Open Access Journals (Sweden)

    Micol Seigel

    2009-02-01

    Full Text Available In Uneven Encounters, the forthcoming book from which this article is excerpted, Micol Seigel chronicles the exchange of popular culture between Brazil and the United States in the years between the World Wars, and she demonstrates how that exchange affected ideas of race and nation in both countries. From Americans interpreting advertisements for Brazilian coffee or dancing the Brazilian maxixe, to Rio musicians embracing the “foreign” qualities of jazz, Seigel traces a lively, cultural back-and-forth. Along the way, she shows how race and nation are constructed together, by both non-elites and elites, and gleaned from global cultural and intellectual currents as well as local, regional, and national ones. Seigel explores the circulation of images of Brazilian coffee and of maxixe in the United States during the period just after the imperial expansions of the early twentieth century. Exoticist interpretations structured North Americans’ paradoxical sense of self as productive “consumer citizens.” Some people, however, could not simply assume the privileges of citizenship. In their struggles against racism, Afro-descended citizens living in the cities of Rio de Janeiro, São Paulo, New York, and Chicago encountered images and notions of each other, and found them useful. Seigel introduces readers to cosmopolitan Afro-Brazilians and African Americans who rarely traveled far but who absorbed ideas from abroad nonetheless. African American vaudeville artists saw the utility of pretending to “be” Brazilian to cross the color line on stage. Putting on “nation drag,” they passed not from one race to another but out of familiar racial categories entirely. Afro-Brazilian journalists reported intensively on foreign, particularly North American, news and eventually entered into conversation with the U.S. black press in a collaborative but still conflictual dialogue. Seigel suggests that projects comparing U.S. and Brazilian racial

  16. Food Safety Nets:

    OpenAIRE

    Haggblade, Steven; Diallo, Boubacar; Staatz, John; Theriault, Veronique; Traoré, Abdramane

    2013-01-01

    Food and social safety nets have a history as long as human civilization. In hunter gatherer societies, food sharing is pervasive. Group members who prove unlucky in the short run, hunting or foraging, receive food from other households in anticipation of reciprocal consideration at a later time (Smith 1988). With the emergence of the first large sedentary civilizations in the Middle East, administrative systems developed specifically around food storage and distribution. The ancient Egyptian...

  17. Net technical assessment

    OpenAIRE

    Wegmann, David G.

    1989-01-01

    Approved for public release; distribution is unlimited. The present and near term military balance of power between the U.S. and the Soviet Union can be expressed in a variety of net assessments. One can examine the strategic nuclear balance, the conventional balance in Europe, the maritime balance, and many others. Such assessments are essential not only for policy making but for arms control purposes and future force structure planning. However, to project the future military balance, on...

  18. Using WordNet for Building WordNets

    CERN Document Server

    Farreres, X; Farreres, Xavier; Rodriguez, Horacio; Rigau, German

    1998-01-01

    This paper summarises a set of methodologies and techniques for the fast construction of multilingual WordNets. The English WordNet is used in this approach as a backbone for Catalan and Spanish WordNets and as a lexical knowledge resource for several subtasks.

  19. A Conventional Liner Acoustic/Drag Interaction Benchmark Database

    Science.gov (United States)

    Howerton, Brian M.; Jones, Michael G.

    2017-01-01

    The aerodynamic drag of acoustic liners has become a significant topic in the design of such for aircraft noise applications. In order to evaluate the benefits of concepts designed to reduce liner drag, it is necessary to establish the baseline performance of liners employing the typical design features of conventional configurations. This paper details a set of experiments in the NASA Langley Grazing Flow Impedance Tube to quantify the relative drag of a number of perforate-over-honeycomb liner configurations at flow speeds of M=0.3 and 0.5. These conventional liners are investigated to determine their resistance factors using a static pressure drop approach. Comparison of the resistance factors gives a relative measurement of liner drag. For these same flow conditions, acoustic measurements are performed with tonal excitation from 400 to 3000 Hz at source sound pressure levels of 140 and 150 dB. Educed impedance and attenuation spectra are used to determine the interaction between acoustic performance and drag.

  20. The Overall Drag Losses For A Combination of Bodies

    Directory of Open Access Journals (Sweden)

    Sabah Al-Janabi

    2013-05-01

    Full Text Available The objective of this work is to obtain better understanding of the flow over a combination of bluff bodies in close enough proximity to strongly interact with each other. This interaction is often beneficial in that the drag of the overall system is reduced. Proto-types for this problem come from tractor- trailer and missiles, and from various add-on devices designed to reduce their drag. Thus, an experimental investigation was carried out by placing  conical frontal bodies having a base diameter of 0.65 cylinder diameter with different vertex angles (30°, 50°, 70°, and 90°. It was found that, the bluffer cone with 90° vertex angle gives the best minimum drag, which is 31% lower than the drag of the isolated cylinder. Also an interesting phenomenon was observed in that, the minimum drags for all combinations are obtained at the same gap ratio (i.e.at g/d2= 0.365.

  1. Creating drag and lift curves from soccer trajectories

    Science.gov (United States)

    Goff, John Eric; Kelley, John; Hobson, Chad M.; Seo, Kazuya; Asai, Takeshi; Choppin, S. B.

    2017-07-01

    Trajectory analysis is an alternative to using wind tunnels to measure a soccer ball’s aerodynamic properties. It has advantages over wind tunnel testing such as being more representative of game play. However, previous work has not presented a method that produces complete, speed-dependent drag and lift coefficients. Four high-speed cameras in stereo-calibrated pairs were used to measure the spatial co-ordinates for 29 separate soccer trajectories. Those trajectories span a range of launch speeds from 9.3 to 29.9 m s-1. That range encompasses low-speed laminar flow of air over a soccer ball, through the drag crises where air flow is both laminar and turbulent, and up to high-speed turbulent air flow. Results from trajectory analysis were combined to give speed-dependent drag and lift coefficient curves for the entire range of speeds found in the 29 trajectories. The average root mean square error between the measured and modelled trajectory was 0.028 m horizontally and 0.034 m vertically. The drag and lift crises can be observed in the plots of drag and lift coefficients respectively.

  2. Proof nets for lingusitic analysis

    NARCIS (Netherlands)

    Moot, R.C.A.

    2002-01-01

    This book investigates the possible linguistic applications of proof nets, redundancy free representations of proofs, which were introduced by Girard for linear logic. We will adapt the notion of proof net to allow the formulation of a proof net calculus which is soundand complete for the

  3. Teaching Tennis for Net Success.

    Science.gov (United States)

    Young, Bryce

    1989-01-01

    A program for teaching tennis to beginners, NET (Net Easy Teaching) is described. The program addresses three common needs shared by tennis students: active involvement in hitting the ball, clearing the net, and positive reinforcement. A sample lesson plan is included. (IAH)

  4. Net4Care Ecosystem Website

    DEFF Research Database (Denmark)

    Christensen, Henrik Bærbak; Hansen, Klaus Marius; Rasmussen, Morten

    2012-01-01

    is a tele-monitoring scenario in which Net4Care clients are deployed in a gateway in private homes. Medical devices then connect to these gateways and transmit their observations to a Net4Care server. In turn the Net4Care server creates valid clinical HL7 documents, stores them in a national XDS repository...

  5. Separability of drag and thrust in undulatory animals and machines

    CERN Document Server

    Bale, Rahul; Neveln, Izaak D; Bhalla, Amneet Pal Singh; MacIver, Malcolm A; Patankar, Neelesh A

    2014-01-01

    For nearly a century, researchers have tried to understand the swimming of aquatic animals in terms of a balance between the forward thrust from swimming movements and drag on the body. Prior approaches have failed to provide a separation of these two forces for undulatory swimmers such as lamprey and eels, where most parts of the body are simultaneously generating drag and thrust. We nonetheless show that this separation is possible, and delineate its fundamental basis in undulatory swimmers. Our approach unifies a vast diversity of undulatory aquatic animals (anguilliform, sub-carangiform, gymnotiform, bal- istiform, rajiform) and provides design principles for highly agile bioinspired underwater vehicles. This approach has practical utility within biology as well as engineering. It is a predictive tool for use in understanding the role of the mechanics of movement in the evolutionary emergence of morphological features relating to locomotion. For example, we demonstrate that the drag-thrust separation fram...

  6. Acoustic Liner Drag: Measurements on Novel Facesheet Perforate Geometries

    Science.gov (United States)

    Howerton, Brian M.; Jones, Michael G.

    2016-01-01

    Interest in characterization of the aerodynamic drag of acoustic liners has increased in the past several years. This paper details experiments in the NASA Langley Grazing Flow Impedance Tube to quantify the relative drag of several perforate-over-honeycomb liner configurations at flow speeds of centerline flow Mach number equals 0.3 and 0.5. Various perforate geometries and orientations are investigated to determine their resistance factors using a static pressure drop approach. Comparison of these resistance factors gives a relative measurement of liner drag. For these same flow conditions, acoustic measurements are performed with tonal excitation from 400 to 3000 hertz at source sound pressure levels of 140 and 150 decibels. Educed impedance and attenuation spectra are used to determine the impact of variations in perforate geometry on acoustic performance.

  7. Development of a Two-fluid Drag Law for Clustered Particles using Direct Numerical Simulation and Validation through Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Gokaltun, Seckin [Florida International Univ., Miami, FL (United States); Munroe, Norman [Florida International Univ., Miami, FL (United States); Subramaniam, Shankar [Iowa State Univ., Ames, IA (United States)

    2014-12-31

    This study presents a new drag model, based on the cohesive inter-particle forces, implemented in the MFIX code. This new drag model combines an existing standard model in MFIX with a particle-based drag model based on a switching principle. Switches between the models in the computational domain occur where strong particle-to-particle cohesion potential is detected. Three versions of the new model were obtained by using one standard drag model in each version. Later, performance of each version was compared against available experimental data for a fluidized bed, published in the literature and used extensively by other researchers for validation purposes. In our analysis of the results, we first observed that standard models used in this research were incapable of producing closely matching results. Then, we showed for a simple case that a threshold is needed to be set on the solid volume fraction. This modification was applied to avoid non-physical results for the clustering predictions, when governing equation of the solid granular temperate was solved. Later, we used our hybrid technique and observed the capability of our approach in improving the numerical results significantly; however, improvement of the results depended on the threshold of the cohesive index, which was used in the switching procedure. Our results showed that small values of the threshold for the cohesive index could result in significant reduction of the computational error for all the versions of the proposed drag model. In addition, we redesigned an existing circulating fluidized bed (CFB) test facility in order to create validation cases for clustering regime of Geldart A type particles.

  8. Aero-acoustics of Drag Generating Swirling Exhaust Flows

    Science.gov (United States)

    Shah, P. N.; Mobed, D.; Spakovszky, Z. S.; Brooks, T. F.; Humphreys, W. M. Jr.

    2007-01-01

    Aircraft on approach in high-drag and high-lift configuration create unsteady flow structures which inherently generate noise. For devices such as flaps, spoilers and the undercarriage there is a strong correlation between overall noise and drag such that, in the quest for quieter aircraft, one challenge is to generate drag at low noise levels. This paper presents a rigorous aero-acoustic assessment of a novel drag concept. The idea is that a swirling exhaust flow can yield a steady, and thus relatively quiet, streamwise vortex which is supported by a radial pressure gradient responsible for pressure drag. Flows with swirl are naturally limited by instabilities such as vortex breakdown. The paper presents a first aero-acoustic assessment of ram pressure driven swirling exhaust flows and their associated instabilities. The technical approach combines an in-depth aerodynamic analysis, plausibility arguments to qualitatively describe the nature of acoustic sources, and detailed, quantitative acoustic measurements using a medium aperture directional microphone array in combination with a previously established Deconvolution Approach for Mapping of Acoustic Sources (DAMAS). A model scale engine nacelle with stationary swirl vanes was designed and tested in the NASA Langley Quiet Flow Facility at a full-scale approach Mach number of 0.17. The analysis shows that the acoustic signature is comprised of quadrupole-type turbulent mixing noise of the swirling core flow and scattering noise from vane boundary layers and turbulent eddies of the burst vortex structure near sharp edges. The exposed edges are the nacelle and pylon trailing edge and the centerbody supporting the vanes. For the highest stable swirl angle setting a nacelle area based drag coefficient of 0.8 was achieved with a full-scale Overall Sound Pressure Level (OASPL) of about 40dBA at the ICAO approach certification point.

  9. Master Robotic Net

    Directory of Open Access Journals (Sweden)

    Vladimir Lipunov

    2010-01-01

    Full Text Available The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19-20. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovae (including SNIa, search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System, and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes.

  10. Art/Net/Work

    DEFF Research Database (Denmark)

    Andersen, Christian Ulrik; Lindstrøm, Hanne

    2006-01-01

    The seminar Art|Net|Work deals with two important changes in our culture. On one side, the network has become essential in the latest technological development. The Internet has entered a new phase, Web 2.0, including the occurrence of as ‘Wiki’s’, ‘Peer-2-Peer’ distribution, user controlled...... the praxis of the artist. We see different kinds of interventions and activism (including ‘hacktivism’) using the network as a way of questioning the invisible rules that govern public and semi-public spaces. Who ‘owns’ them? What kind of social relationships do they generate? On what principle...

  11. Locus of the apices of projectile trajectories under constant drag

    Science.gov (United States)

    Hernández-Saldaña, H.

    2017-11-01

    Using the hodograph method, we present an analytical solution for projectile coplanar motion under constant drag, parametrised by the velocity angle. We find the locus formed by the apices of the projectile trajectories, and discuss its implementation for the motion of a particle on an inclined plane in presence of Coulomb friction. The range and time of flight are obtained numerically, and we find that the optimal launching angle is smaller than in the drag-free case. This is a good example of a problem with constant dissipation of energy that includes curvature; it is appropriate for intermediate courses of mechanics.

  12. Intershell resistance in multiwall carbon nanotubes: A Coulomb drag study

    DEFF Research Database (Denmark)

    Lunde, Anders Mathias; Flensborg, Karsten; Jauho, Antti-Pekka

    2005-01-01

    We calculate the intershell resistance R-21 in a multiwall carbon nanotube as a function of temperature T and Fermi level epsilon(F) (e.g., a gate voltage), varying the chirality of the inner and outer tubes. This is done in a so-called Coulomb drag setup, where a current I-1 in one shell induces...... effects for the Coulomb drag between different tubes due to selection rules combined with mismatching of wave vector and crystal angular momentum conservation near the Fermi level. This gives rise to orders of magnitude changes in R-21 and even the sign of R-21 can change depending on the chirality...

  13. Helminth.net: expansions to Nematode.net and an introduction to Trematode.net

    Science.gov (United States)

    Martin, John; Rosa, Bruce A.; Ozersky, Philip; Hallsworth-Pepin, Kymberlie; Zhang, Xu; Bhonagiri-Palsikar, Veena; Tyagi, Rahul; Wang, Qi; Choi, Young-Jun; Gao, Xin; McNulty, Samantha N.; Brindley, Paul J.; Mitreva, Makedonka

    2015-01-01

    Helminth.net (http://www.helminth.net) is the new moniker for a collection of databases: Nematode.net and Trematode.net. Within this collection we provide services and resources for parasitic roundworms (nematodes) and flatworms (trematodes), collectively known as helminths. For over a decade we have provided resources for studying nematodes via our veteran site Nematode.net (http://nematode.net). In this article, (i) we provide an update on the expansions of Nematode.net that hosts omics data from 84 species and provides advanced search tools to the broad scientific community so that data can be mined in a useful and user-friendly manner and (ii) we introduce Trematode.net, a site dedicated to the dissemination of data from flukes, flatworm parasites of the class Trematoda, phylum Platyhelminthes. Trematode.net is an independent component of Helminth.net and currently hosts data from 16 species, with information ranging from genomic, functional genomic data, enzymatic pathway utilization to microbiome changes associated with helminth infections. The databases’ interface, with a sophisticated query engine as a backbone, is intended to allow users to search for multi-factorial combinations of species’ omics properties. This report describes updates to Nematode.net since its last description in NAR, 2012, and also introduces and presents its new sibling site, Trematode.net. PMID:25392426

  14. NETS FOR PEACH PROTECTED CULTIVATION

    Directory of Open Access Journals (Sweden)

    Evelia Schettini

    2012-06-01

    Full Text Available The aim of this paper was to investigate the radiometric properties of coloured nets used to protect a peach cultivation. The modifications of the solar spectral distribution, mainly in the R and FR wavelength band, influence plant photomorphogenesis by means of the phytochrome and cryptochrome. The phytochrome response is characterized in terms of radiation rate in the red wavelengths (R, 600-700 nm to that in the farred radiation (FR, 700-800 nm, i.e. the R/FR ratio. The effects of the blue radiation (B, 400-500 nm is investigated by the ratio between the blue radiation and the far-red radiation, i.e. the B/FR ratio. A BLUE net, a RED net, a YELLOW net, a PEARL net, a GREY net and a NEUTRAL net were tested in Bari (Italy, latitude 41° 05’ N. Peach trees were located in pots inside the greenhouses and in open field. The growth of the trees cultivated in open field was lower in comparison to the growth of the trees grown under the nets. The RED, PEARL, YELLOW and GREY nets increased the growth of the trees more than the other nets. The nets positively influenced the fruit characteristics, such as fruit weight and flesh firmness.

  15. Shape optimization of active and passive drag-reducing devices on a D-shaped bluff body

    CERN Document Server

    Semaan, Richard

    2016-01-01

    Shape optimization of an active and a passive drag-reducing device on a two-dimensional D-shaped bluff body is performed. The two devices are: Coanda actuator, and randomly-shaped trailing-edge flap. The optimization sequence is performed by coupling the genetic algorithm software DAKOTA to the mesh generator Pointwise and to the CFD solver OpenFOAM. For the the active device the cost functional is the power ratio, whereas for the passive device it is the drag coefficient. The optimization leads to total power savings of $\\approx 70\\%$ for the optimal Coanda actuator, and a 40\\% drag reduction for the optimal flap. This reduction is mainly achieved through streamlining the base flow and suppressing the vortex shedding. The addition of either an active or a passive device creates two additional smaller recirculation regions in the base cavity that shifts the larger recirculation region away from the body and increases the base pressure. The results are validated against more refined URANS simulations for selec...

  16. May 2003 Working Group Meeting on Heavy Vehicle Aerodynamic Drag: Presentations and Summary of Comments and Conclusions

    Energy Technology Data Exchange (ETDEWEB)

    McCallen, R; Salari, K; Ortega, J; Browand, F; Hammache, M; Hsu, T Y; Arcas, D; Leoard, A; Chatelain, P; Rubel, M; Roy, C; DeChant, L; Hassan, B; Ross, J; Satran, D; Walker, S; Heineck, J T; Englar, R; Pointer, D; Sofu, T

    2003-05-01

    A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at Lawrence Livermore National Laboratory on May 29-30, 2003. The purpose of the meeting was to present and discuss suggested guidance and direction for the design of drag reduction devices determined from experimental and computational studies. Representatives from the Department of Energy (DOE)/Office of Energy Efficiency and Renewable Energy/Office of FreedomCAR & Vehicle Technologies, Lawrence Livermore National Laboratory (LLNL), Sandia National Laboratories (SNL), NASA Ames Research Center (NASA), University of Southern California (USC), California Institute of Technology (Caltech), Georgia Tech Research Institute (GTRI), Argonne National Laboratory (ANL), Clarkson University, and PACCAR participated in the meeting. This report contains the technical presentations (viewgraphs) delivered at the Meeting, briefly summarizes the comments and conclusions, provides some highlighted items, and outlines the future action items.

  17. March 2001 Working Group Meeting on Heavy Vehicle Aerodynamic Drag: Presentations and Summary of Comments and Conclusions

    Energy Technology Data Exchange (ETDEWEB)

    Greenman, R; Dunn, T; Owens, J; Laskowski, G; Flowers, D; Browand, F; Knight, A; Hammache, M; Leoard, A; Rubel, M; Salari, K; Rutledge, W; Ross, J; Satran, D; Heineck, J T; Walker, S; Driver, D; Storms, B

    2001-05-14

    A Working Group Meeting on Heavy Vehicle Aerodynamic Drag was held at Lawrence Livermore National Laboratory on March 28 and 29, 2001. The purpose of the meeting was to present and discuss technical details on the experimental and computational work in progress and future project plans. Due to the large participation from industry and other research organizations, a large portion of the meeting (all of the first day and part of the second day) was devoted to the presentation and discussion of industry's perspective and work being done by other organizations on the demonstration of commercial software and the demonstration of a drag reduction device. This report contains the technical presentations (viewgraphs) delivered at the Meeting, briefly summarizes the comments and conclusions, and outlines the future action items.

  18. The equivalency between logic Petri workflow nets and workflow nets.

    Science.gov (United States)

    Wang, Jing; Yu, ShuXia; Du, YuYue

    2015-01-01

    Logic Petri nets (LPNs) can describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. Logic Petri workflow nets (LPWNs) are proposed based on LPNs in this paper. Process mining is regarded as an important bridge between modeling and analysis of data mining and business process. Workflow nets (WF-nets) are the extension to Petri nets (PNs), and have successfully been used to process mining. Some shortcomings cannot be avoided in process mining, such as duplicate tasks, invisible tasks, and the noise of logs. The online shop in electronic commerce in this paper is modeled to prove the equivalence between LPWNs and WF-nets, and advantages of LPWNs are presented.

  19. Drag and lift forces on particles in a rotating flow

    NARCIS (Netherlands)

    Bluemink, J.J.; Lohse, Detlef; Prosperetti, Andrea; van Wijngaarden, L.; van Wijngaarden, L.

    2010-01-01

    A freely rotating sphere in a solid-body rotating flow is experimentally investigated. When the sphere is buoyant, it reaches an equilibrium position from which drag and lift coefficients are determined over a wide range of particle Reynolds numbers (2 ≤ Re ≤ 1060). The wake behind the sphere is

  20. Drag power kite with very high lift coefficient

    NARCIS (Netherlands)

    Bauer, F.; Kennel, R.M.; Hackl, C.M.; Campagnolo, F.; Patt, M.; Schmehl, R.

    2018-01-01

    As an alternative to conventional wind turbines, this study considered kites with onboard wind turbines driven by a high airspeed due to crosswind flight (“drag power”). The hypothesis of this study was, that if the kite's lift coefficient is maximized, then the power, energy yield, allowed costs

  1. Drag force and surface roughness measurements on freshwater biofouled surfaces.

    Science.gov (United States)

    Andrewartha, J; Perkins, K; Sargison, J; Osborn, J; Walker, G; Henderson, A; Hallegraeff, G

    2010-05-01

    The detrimental effect of biofilms on skin friction for near wall flows is well known. The diatom genera Gomphonema and Tabellaria dominated the biofilm mat in the freshwater open channels of the Tarraleah Hydropower Scheme in Tasmania, Australia. A multi-faceted approach was adopted to investigate the drag penalty for biofouled 1.0 m x 0.6 m test plates which incorporated species identification, drag measurement in a recirculating water tunnel and surface characterisation using close-range photogrammetry. Increases in total drag coefficient of up to 99% were measured over clean surface values for biofouled test plates incubated under flow conditions in a hydropower canal. The effective roughness of the biofouled surfaces was found to be larger than the physical roughness; the additional energy dissipation was caused in part by the vibration of the biofilms in three-dimensions under flow conditions. The data indicate that there was a roughly linear relationship between the maximum peak-to-valley height of a biofilm and the total drag coefficient.

  2. Towards unified drag laws for inertial flow through fibrous materials

    NARCIS (Netherlands)

    Yazdchi, K.; Luding, Stefan

    2012-01-01

    We give a comprehensive survey of published experimental, numerical and theoretical work on the drag law correlations for fluidized beds and flow through porous media, together with an attempt of systematization. Ranges of validity as well as limitations of commonly used relations (i.e. the Ergun

  3. Single Gradientless Light Beam Drags Particles as Tractor Beams

    DEFF Research Database (Denmark)

    Novitsky, Andrey; Qiu, Cheng-Wei; Wang, Haifeng

    2011-01-01

    is the strong nonparaxiality of the light beam, which contributes to the pulling force owing to momentum conservation. The nonparaxiality of the Bessel beam can be manipulated to possess a dragging force along both the radial longitudinal directions, i.e., a "tractor beam" with stable trajectories is achieved...

  4. Separability of drag and thrust in undulatory animals and machines

    Science.gov (United States)

    Bale, Rahul; Shirgaonkar, Anup A.; Neveln, Izaak D.; Bhalla, Amneet Pal Singh; Maciver, Malcolm A.; Patankar, Neelesh A.

    2014-12-01

    For nearly a century, researchers have tried to understand the swimming of aquatic animals in terms of a balance between the forward thrust from swimming movements and drag on the body. Prior approaches have failed to provide a separation of these two forces for undulatory swimmers such as lamprey and eels, where most parts of the body are simultaneously generating drag and thrust. We nonetheless show that this separation is possible, and delineate its fundamental basis in undulatory swimmers. Our approach unifies a vast diversity of undulatory aquatic animals (anguilliform, sub-carangiform, gymnotiform, bal-istiform, rajiform) and provides design principles for highly agile bioinspired underwater vehicles. This approach has practical utility within biology as well as engineering. It is a predictive tool for use in understanding the role of the mechanics of movement in the evolutionary emergence of morphological features relating to locomotion. For example, we demonstrate that the drag-thrust separation framework helps to predict the observed height of the ribbon fin of electric knifefish, a diverse group of neotropical fish which are an important model system in sensory neurobiology. We also show how drag-thrust separation leads to models that can predict the swimming velocity of an organism or a robotic vehicle.

  5. The compressibility rule for drag of airfoil noses

    Science.gov (United States)

    Jones, R. T.; Vandyke, M. D.

    1976-01-01

    It is shown that the drag of any semi-infinite airfoil section in purely subsonic inviscid flow follows precisely the Prandtl-Glauert compressibility rule. The result for the parabola has application to leading edge corrections in thin airfoil theory.

  6. 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.

  7. Plasmon-mediated Coulomb drag between graphene waveguides

    DEFF Research Database (Denmark)

    Shylau, Artsem A.; Jauho, Antti-Pekka

    2014-01-01

    We analyze theoretically charge transport in Coulomb coupled graphene waveguides (GWGs). The GWGs are defined using antidot lattices, and the lateral geometry bypasses many technological challenges of earlier designs. The drag resistivity ρD, which is a measure of the many-particle interactions...

  8. 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…

  9. Drag force in a cold or hot granular medium

    Science.gov (United States)

    Seguin, A.; Gondret, P.

    2017-09-01

    We measure experimentally and analyze the resisting force exerted by a bidimensional packing of small disks on a larger intruder disk dragged horizontally at constant velocity V0. Depending on the vibration level of the packing that leads to a granular "cold" or "hot" packing, two force regimes are observed. At low vibration level ("cold" granular medium), the drag force F does not depend on V0, whereas for high vibrations ("hot" granular medium), the drag force increases linearly with V0. Both regimes can be understood by the balance of two "granular temperatures" that can be defined in the system: a bulk temperature Tb imposed by the external vibration to the overall packing and a local temperature T0 induced by the own motion of the intruder disk in its vicinity. All experimental data obtained for different sizes and velocities of the intruder disk are shown to be governed by the temperature ratio T0/Tb . A critical velocity V0 c, above which the system switches from "hot" to "cold," can be obtained in this frame. Finally, we discuss how these two "viscous" regimes should be followed by an inertial regime where the drag force F should increase as V0 2 at high enough velocity values, for V0 greater than a critical value V0 i corresponding to high enough Reynolds or Froude number.

  10. Energy-Saving Melting and Revert Reduction Technology (E-SMARRT): Use of Laser Engineered Net Shaping for Rapid Manufacturing of Dies with Protective Coatings and Improved Thermal Management

    Energy Technology Data Exchange (ETDEWEB)

    Brevick, Jerald R. [Ohio State University

    2014-06-13

    retained as the exterior layer of the tooling, while commercially pure copper was chosen for the interior structure of the tooling. The tooling was fabricated by traditional machining of the copper substrate, and H13 powder was deposited on the copper via the Laser Engineered Net Shape (LENSTM) process. The H13 deposition layer was then final machined by traditional methods. Two tooling components were designed and fabricated; a thermal fatigue test specimen, and a core for a commercial aluminum high pressure die casting tool. The bimetallic thermal fatigue specimen demonstrated promising performance during testing, and the test results were used to improve the design and LENS TM deposition methods for subsequent manufacture of the commercial core. Results of the thermal finite element analysis for the thermal fatigue test specimen indicate that it has the ability to lose heat to the internal water cooling passages, and to external spray cooling, significantly faster than a monolithic H13 thermal fatigue sample. The commercial core is currently in the final stages of fabrication, and will be evaluated in an actual production environment at Shiloh Die casting. In this research, the feasibility of designing and fabricating copper/H13 bimetallic die casting tooling via LENS TM processing, for the purpose of improving die casting process efficiency, is demonstrated.

  11. Optimizing sampling design to deal with mist-net avoidance in Amazonian birds and bats.

    Directory of Open Access Journals (Sweden)

    João Tiago Marques

    Full Text Available Mist netting is a widely used technique to sample bird and bat assemblages. However, captures often decline with time because animals learn and avoid the locations of nets. This avoidance or net shyness can substantially decrease sampling efficiency. We quantified the day-to-day decline in captures of Amazonian birds and bats with mist nets set at the same location for four consecutive days. We also evaluated how net avoidance influences the efficiency of surveys under different logistic scenarios using re-sampling techniques. Net avoidance caused substantial declines in bird and bat captures, although more accentuated in the latter. Most of the decline occurred between the first and second days of netting: 28% in birds and 47% in bats. Captures of commoner species were more affected. The numbers of species detected also declined. Moving nets daily to minimize the avoidance effect increased captures by 30% in birds and 70% in bats. However, moving the location of nets may cause a reduction in netting time and captures. When moving the nets caused the loss of one netting day it was no longer advantageous to move the nets frequently. In bird surveys that could even decrease the number of individuals captured and species detected. Net avoidance can greatly affect sampling efficiency but adjustments in survey design can minimize this. Whenever nets can be moved without losing netting time and the objective is to capture many individuals, they should be moved daily. If the main objective is to survey species present then nets should still be moved for bats, but not for birds. However, if relocating nets causes a significant loss of netting time, moving them to reduce effects of shyness will not improve sampling efficiency in either group. Overall, our findings can improve the design of mist netting sampling strategies in other tropical areas.

  12. Optimizing sampling design to deal with mist-net avoidance in Amazonian birds and bats.

    Science.gov (United States)

    Marques, João Tiago; Ramos Pereira, Maria J; Marques, Tiago A; Santos, Carlos David; Santana, Joana; Beja, Pedro; Palmeirim, Jorge M

    2013-01-01

    Mist netting is a widely used technique to sample bird and bat assemblages. However, captures often decline with time because animals learn and avoid the locations of nets. This avoidance or net shyness can substantially decrease sampling efficiency. We quantified the day-to-day decline in captures of Amazonian birds and bats with mist nets set at the same location for four consecutive days. We also evaluated how net avoidance influences the efficiency of surveys under different logistic scenarios using re-sampling techniques. Net avoidance caused substantial declines in bird and bat captures, although more accentuated in the latter. Most of the decline occurred between the first and second days of netting: 28% in birds and 47% in bats. Captures of commoner species were more affected. The numbers of species detected also declined. Moving nets daily to minimize the avoidance effect increased captures by 30% in birds and 70% in bats. However, moving the location of nets may cause a reduction in netting time and captures. When moving the nets caused the loss of one netting day it was no longer advantageous to move the nets frequently. In bird surveys that could even decrease the number of individuals captured and species detected. Net avoidance can greatly affect sampling efficiency but adjustments in survey design can minimize this. Whenever nets can be moved without losing netting time and the objective is to capture many individuals, they should be moved daily. If the main objective is to survey species present then nets should still be moved for bats, but not for birds. However, if relocating nets causes a significant loss of netting time, moving them to reduce effects of shyness will not improve sampling efficiency in either group. Overall, our findings can improve the design of mist netting sampling strategies in other tropical areas.

  13. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kristensen, Lars Michael

    studies that illustrate the practical use of CPN modelling and validation for design, specification, simulation, verification and implementation in various application domains. Their presentation primarily aims at readers interested in the practical use of CPN. Thus all concepts and constructs are first......Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism...... and the immense number of possible execution sequences. In this textbook, Jensen and Kristensen introduce the constructs of the CPN modelling language and present the related analysis methods in detail. They also provide a comprehensive road map for the practical use of CPN by showcasing selected industrial case...

  14. Reducing drag of a commuter train, using engine exhaust momentum

    Science.gov (United States)

    Ha, Dong Keun

    The objective of this thesis was to perform numerical investigations of two different methods of injecting fluid momentum into the air flow above a commuter train to reduce its drag. Based on previous aerodynamic modifications of heavy duty trucks in improving fuel efficiency, two structural modifications were designed and applied to a Metrolink Services commuter train in the Los Angeles (LA) County area to reduce its drag and subsequently improve fuel efficiency. The first modification was an L-shaped channel, added to the exhaust cooling fan above the locomotive roof to divert and align the exhaust gases in the axial direction. The second modification was adding an airfoil shaped lid over the L-shape channel, to minimize the drag of the perturbed structure, and thus reduce the overall drag. The computational fluid dynamic (CFD) software CCM+ from CD-Adapco with the ?-? turbulence model was used for the simulations. A single train set which consists of three vehicles: one locomotive, one trailer car and one cab car were used. All the vehicles were modeled based on the standard Metrolink fleet train size. The wind speed was at 90 miles per hour (mph), which is the maximum speed for the Orange County Metrolink line. Air was used as the exhaust gas in the simulation. The temperature of the exhausting air emitting out of the cooling fan on the roof was 150 F and the average fan speed was 120 mph. Results showed that with the addition of the lid, momentum injection results in reduced flow separation and pressure recovery behind the locomotive, which reduces the overall drag by at least 30%.

  15. Particle drag history in a subcritical post-shock flow - data analysis method and uncertainty

    Science.gov (United States)

    Ding, Liuyang; Bordoloi, Ankur; Adrian, Ronald; Prestridge, Kathy; Arizona State University Team; Los Alamos National Laboratory Team

    2017-11-01

    A novel data analysis method for measuring particle drag in an 8-pulse particle tracking velocimetry-accelerometry (PTVA) experiment is described. We represented the particle drag history, CD(t) , using polynomials up to the third order. An analytical model for continuous particle position history was derived by integrating an equation relating CD(t) with particle velocity and acceleration. The coefficients of CD(t) were then calculated by fitting the position history model to eight measured particle locations in the sense of least squares. A preliminary test with experimental data showed that the new method yielded physically more reasonable particle velocity and acceleration history compared to conventionally adopted polynomial fitting. To fully assess and optimize the performance of the new method, we performed a PTVA simulation by assuming a ground truth of particle motion based on an ensemble of experimental data. The results indicated a significant reduction in the RMS error of CD. We also found that for particle locating noise between 0.1 and 3 pixels, a range encountered in our experiment, the lowest RMS error was achieved by using the quadratic CD(t) model. Furthermore, we will also discuss the optimization of the pulse timing configuration.

  16. Modeling complex flow structures and drag around a submerged plant of varied posture

    Science.gov (United States)

    Boothroyd, Richard J.; Hardy, Richard J.; Warburton, Jeff; Marjoribanks, Timothy I.

    2017-04-01

    Although vegetation is present in many rivers, the bulk of past work concerned with modeling the influence of vegetation on flow has considered vegetation to be morphologically simple and has generally neglected the complexity of natural plants. Here we report on a combined flume and numerical model experiment which incorporates time-averaged plant posture, collected through terrestrial laser scanning, into a computational fluid dynamics model to predict flow around a submerged riparian plant. For three depth-limited flow conditions (Reynolds number = 65,000-110,000), plant dynamics were recorded through high-definition video imagery, and the numerical model was validated against flow velocities collected with an acoustic Doppler velocimeter. The plant morphology shows an 18% reduction in plant height and a 14% increase in plant length, compressing and reducing the volumetric canopy morphology as the Reynolds number increases. Plant shear layer turbulence is dominated by Kelvin-Helmholtz type vortices generated through shear instability, the frequency of which is estimated to be between 0.20 and 0.30 Hz, increasing with Reynolds number. These results demonstrate the significant effect that the complex morphology of natural plants has on in-stream drag, and allow a physically determined, species-dependent drag coefficient to be calculated. Given the importance of vegetation in river corridor management, the approach developed here demonstrates the necessity to account for plant motion when calculating vegetative resistance.

  17. 76 FR 34859 - Safety Zone; Augusta Southern Nationals Drag Boat Race, Savannah River, Augusta, GA

    Science.gov (United States)

    2011-06-15

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Augusta Southern Nationals Drag Boat Race... during the Augusta Southern Nationals Drag Boat Race. The Augusta Southern Nationals Drag Boat Race will consist of a series of high-speed boat races. The event is scheduled to take place from Thursday, July 14...

  18. Acceleration Noise Considerations for Drag-free Satellite Geodesy Missions

    Science.gov (United States)

    Hong, S. H.; Conklin, J. W.

    2016-12-01

    The GRACE mission, which launched in 2002, opened a new era of satellite geodesy by providing monthly mass variation solutions with spatial resolution of less than 200 km. GRACE proved the usefulness of a low-low satellite-to-satellite tracking formation. Analysis of the GRACE data showed that the K-Band ranging system, which is used to measure the range between the two satellites, is the limiting factor for the precision of the solution. Consequently, the GRACE-FO mission, schedule for launch in 2017, will continue the work of GRACE, but will also test a new, higher precision laser ranging interferometer compared with the K-Band ranging system. Beyond GRACE-FO, drag-free systems are being considered for satellite geodesy missions. GOCE tested a drag-free attitude control system with a gravity gradiometer and showed improvements in the acceleration noise compensation compared to the electrostatic accelerometers used in GRACE. However, a full drag-free control system with a gravitational reference sensor has not yet been applied to satellite geodesy missions. More recently, this type of drag-free system was used in LISA Pathfinder, launched in 2016, with an acceleration noise performance two orders of magnitude better than that of GOCE. We explore the effects of drag-free performance in satellite geodesy missions similar to GRACE-FO by applying three different residual acceleration noises from actual space missions: GRACE, GOCE and LISA Pathfinder. Our solutions are limited to degree 60 spherical harmonic coefficients with biweekly time resolution. Our analysis shows that a drag-free system with acceleration noise performance comparable to GOCE and LISA-Pathfinder would greatly improve the accuracy of gravity solutions. In addition to these results, we also present the covariance shaping process used in the estimation. In the future, we plan to use actual acceleration noise data measured using the UF torsion pendulum. This apparatus is a ground facility at

  19. Multi-Objective Flight Control for Drag Minimization and Load Alleviation of High-Aspect Ratio Flexible Wing Aircraft

    Science.gov (United States)

    Nguyen, Nhan; Ting, Eric; Chaparro, Daniel; Drew, Michael; Swei, Sean

    2017-01-01

    As aircraft wings become much more flexible due to the use of light-weight composites material, adverse aerodynamics at off-design performance can result from changes in wing shapes due to aeroelastic deflections. Increased drag, hence increased fuel burn, is a potential consequence. Without means for aeroelastic compensation, the benefit of weight reduction from the use of light-weight material could be offset by less optimal aerodynamic performance at off-design flight conditions. Performance Adaptive Aeroelastic Wing (PAAW) technology can potentially address these technical challenges for future flexible wing transports. PAAW technology leverages multi-disciplinary solutions to maximize the aerodynamic performance payoff of future adaptive wing design, while addressing simultaneously operational constraints that can prevent the optimal aerodynamic performance from being realized. These operational constraints include reduced flutter margins, increased airframe responses to gust and maneuver loads, pilot handling qualities, and ride qualities. All of these constraints while seeking the optimal aerodynamic performance present themselves as a multi-objective flight control problem. The paper presents a multi-objective flight control approach based on a drag-cognizant optimal control method. A concept of virtual control, which was previously introduced, is implemented to address the pair-wise flap motion constraints imposed by the elastomer material. This method is shown to be able to satisfy the constraints. Real-time drag minimization control is considered to be an important consideration for PAAW technology. Drag minimization control has many technical challenges such as sensing and control. An initial outline of a real-time drag minimization control has already been developed and will be further investigated in the future. A simulation study of a multi-objective flight control for a flight path angle command with aeroelastic mode suppression and drag

  20. Linear Logic on Petri Nets

    DEFF Research Database (Denmark)

    Engberg, Uffe Henrik; Winskel, Glynn

    This article shows how individual Petri nets form models of Girard's intuitionistic linear logic. It explores questions of expressiveness and completeness of linear logic with respect to this interpretation. An aim is to use Petri nets to give an understanding of linear logic and give some apprai...

  1. Reference Guide Microsoft.NET

    NARCIS (Netherlands)

    Zee M van der; Verspaij GJ; Rosbergen S; IMP; NMD

    2003-01-01

    Developers, administrators and managers can get more understanding of the .NET technology with this report. They can also make better choices how to use this technology. The report describes the results and conclusions of a study of the usability for the RIVM of this new generation .NET development

  2. Net neutrality and audiovisual services

    NARCIS (Netherlands)

    van Eijk, N.; Nikoltchev, S.

    2011-01-01

    Net neutrality is high on the European agenda. New regulations for the communication sector provide a legal framework for net neutrality and need to be implemented on both a European and a national level. The key element is not just about blocking or slowing down traffic across communication

  3. Experimental Investigation of the Fresnel Drag Effect in RF Coaxial Cables

    Directory of Open Access Journals (Sweden)

    Brotherton D.

    2011-01-01

    Full Text Available An experiment that confirms the Fresnel drag formalism in RF coaxial cables is reported. The Fresnel "drag" in bulk dielectrics and in optical fibers has previously been well established. An explanation for this formalism is given, and it is shown that there is no actual drag phenomenon, rather that the Fresnel drag effect is merely the consequence of a simplified description of EM scattering within a dielectric in motion wrt the dynamical 3-space. The Fresnel drag effect plays a critical role in the design of various light-speed anisotropy detectors.

  4. A Small Universal Petri Net

    Directory of Open Access Journals (Sweden)

    Dmitry A. Zaitsev

    2013-09-01

    Full Text Available A universal deterministic inhibitor Petri net with 14 places, 29 transitions and 138 arcs was constructed via simulation of Neary and Woods' weakly universal Turing machine with 2 states and 4 symbols; the total time complexity is exponential in the running time of their weak machine. To simulate the blank words of the weakly universal Turing machine, a couple of dedicated transitions insert their codes when reaching edges of the working zone. To complete a chain of a given Petri net encoding to be executed by the universal Petri net, a translation of a bi-tag system into a Turing machine was constructed. The constructed Petri net is universal in the standard sense; a weaker form of universality for Petri nets was not introduced in this work.

  5. Drag of the cytosol as a transport mechanism in neurons.

    Science.gov (United States)

    Mussel, Matan; Zeevy, Keren; Diamant, Haim; Nevo, Uri

    2014-06-17

    Axonal transport is typically divided into two components, which can be distinguished by their mean velocity. The fast component includes steady trafficking of different organelles and vesicles actively transported by motor proteins. The slow component comprises nonmembranous materials that undergo infrequent bidirectional motion. The underlying mechanism of slow axonal transport has been under debate during the past three decades. We propose a simple displacement mechanism that may be central for the distribution of molecules not carried by vesicles. It relies on the cytoplasmic drag induced by organelle movement and readily accounts for key experimental observations pertaining to slow-component transport. The induced cytoplasmic drag is predicted to depend mainly on the distribution of microtubules in the axon and the organelle transport rate. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  6. Measuring the Effects of Lift and Drag on Projectile Motion

    Science.gov (United States)

    Cross, Rod

    2012-01-01

    The trajectory of a projectile through the air is affected both by gravity and by aerodynamic forces. The latter forces can conveniently be ignored in many situations, even when they are comparatively large. For example, if a 145-g, 74-mm diameter baseball is pitched at 40 ms[superscript -1] (89.5 mph), it experiences a drag force of about 1.5 N.…

  7. Mechanisms of Active Aerodynamic Load Reduction on a Rotorcraft Fuselage With Rotor Effects

    Science.gov (United States)

    Schaeffler, Norman W.; Allan, Brian G.; Jenkins, Luther N.; Yao, Chung-Sheng; Bartram, Scott M.; Mace, W. Derry; Wong, Oliver D.; Tanner, Philip E.

    2016-01-01

    The reduction of the aerodynamic load that acts on a generic rotorcraft fuselage by the application of active flow control was investigated in a wind tunnel test conducted on an approximately 1/3-scale powered rotorcraft model simulating forward flight. The aerodynamic mechanisms that make these reductions, in both the drag and the download, possible were examined in detail through the use of the measured surface pressure distribution on the fuselage, velocity field measurements made in the wake directly behind the ramp of the fuselage and computational simulations. The fuselage tested was the ROBIN-mod7, which was equipped with a series of eight slots located on the ramp section through which flow control excitation was introduced. These slots were arranged in a U-shaped pattern located slightly downstream of the baseline separation line and parallel to it. The flow control excitation took the form of either synthetic jets, also known as zero-net-mass-flux blowing, and steady blowing. The same set of slots were used for both types of excitation. The differences between the two excitation types and between flow control excitation from different combinations of slots were examined. The flow control is shown to alter the size of the wake and its trajectory relative to the ramp and the tailboom and it is these changes to the wake that result in a reduction in the aerodynamic load.

  8. Preparation of Nano-Scale Biopolymer Extracted from Coconut Residue and Its Performance as Drag Reducing Agent (DRA

    Directory of Open Access Journals (Sweden)

    Hasan Muhammad Luqman Bin

    2017-01-01

    Full Text Available Drag or frictional force is defined as force that acts opposite to the object’s relative motion through a fluid which then will cause frictional pressure loss in the pipeline. Drag Reducing Agent (DRA is used to solve this issue and most of the DRAs are synthetic polymers but has some environmental issues. Therefore for this study, biopolymer known as Coconut Residue (CR is selected as the candidate to replace synthetic polymers DRA. The objective of this study is to evaluate the effectiveness of Nano-scale biopolymer DRA on the application of water injection system. Carboxymethyl cellulose (CMC is extracted by synthesizing the cellulose extracted from CR under the alkali-catalyzed reaction using monochloroacetic acid. The synthesize process is held in controlled condition whereby the concentration of NaOH is kept at 60%wt, 60 °C temperature and the reaction time is 4 hours. For every 25 g of dried CR used, the mass of synthesized CMC yield is at an average of 23.8 g. The synthesized CMC is then grinded in controlled parameters using the ball milling machine to get the Nano-scale size. The particle size obtained from this is 43.32 Nm which is in range of Nano size. This study proved that Nano-size CMC has higher percentage of drag reduction (%DR and flow increase (%FI if compared to normal-size CMC when tested in high and low flow rate; 44% to 48% increase in %DR and %FI when tested in low flow rate, and 16% to 18% increase in %DR and %FI when tested in high flow rate. The success of this research shows that Nano-scale DRA can be considered to be used to have better performance in reducing drag.

  9. The influence of numerical models on determining the drag coefficient

    Directory of Open Access Journals (Sweden)

    Dobeš Josef

    2014-03-01

    Full Text Available The paper deals with numerical modelling of body aerodynamic drag coefficient in the transition from laminar to turbulent flow regimes, where the selection of a suitable numerical model is problematic. On the basic problem of flow around a simple body – sphere selected computational models are tested. The values obtained by numerical simulations of drag coefficients of each model are compared with the graph of dependency of the drag coefficient vs. Reynolds number for a sphere. Next the dependency of Strouhal number vs. Reynolds number is evaluated, where the vortex shedding frequency values for given speed are obtained numerically and experimentally and then the values are compared for each numerical model and experiment. The aim is to specify trends for the selection of appropriate numerical model for flow around bodies problem in which the precise description of the flow field around the obstacle is used to define the acoustic noise source. Numerical modelling is performed by finite volume method using CFD code.

  10. Frame-dragging Effect in Strong Gravity Regime

    CERN Document Server

    Chakraborty, Chandrachur

    2016-01-01

    The exact frame-dragging (or Lense-Thirring (LT) precession) rates for Kerr, Kerr-Taub-NUT (KTN) and Taub-NUT spacetimes have been derived. Remarkably, in the case of the `zero angular momentum' Taub-NUT spacetime, the frame-dragging effect is shown not to vanish, when considered for spinning test gyroscope. In the case of the interior of the pulsars, the exact frame-dragging rate monotonically decreases from the center to the surface along the pole and but it shows an `anomaly' along the equator. Moving from the equator to the pole, it is observed that this `anomaly' disappears after crossing a critical angle. The `same' anomaly can also be found in the KTN spacetime. The resemblance of the anomalous LT precessions in the KTN spacetimes and the spacetime of the pulsars could be used to identify a role of Taub-NUT solutions in the astrophysical observations or equivalently, a signature of the existence of NUT charge in the pulsars.

  11. Protein crystallization image classification with elastic net

    Science.gov (United States)

    Hung, Jeffrey; Collins, John; Weldetsion, Mehari; Newland, Oliver; Chiang, Eric; Guerrero, Steve; Okada, Kazunori

    2014-03-01

    Protein crystallization plays a crucial role in pharmaceutical research by supporting the investigation of a protein's molecular structure through X-ray diffraction of its crystal. Due to the rare occurrence of crystals, images must be manually inspected, a laborious process. We develop a solution incorporating a regularized, logistic regression model for automatically evaluating these images. Standard image features, such as shape context, Gabor filters and Fourier transforms, are first extracted to represent the heterogeneous appearance of our images. Then the proposed solution utilizes Elastic Net to select relevant features. Its L1-regularization mitigates the effects of our large dataset, and its L2- regularization ensures proper operation when the feature number exceeds the sample number. A two-tier cascade classifier based on naïve Bayes and random forest algorithms categorized the images. In order to validate the proposed method, we experimentally compare it with naïve Bayes, linear discriminant analysis, random forest, and their two-tier cascade classifiers, by 10-fold cross validation. Our experimental results demonstrate a 3-category accuracy of 74%, outperforming other models. In addition, Elastic Net better reduces the false negatives responsible for a high, domain specific risk. To the best of our knowledge, this is the first attempt to apply Elastic Net to classifying protein crystallization images. Performance measured on a large pharmaceutical dataset also fared well in comparison with those presented in the previous studies, while the reduction of the high-risk false negatives is promising.

  12. A Comparison of Experimental and Analytical Procedures to Measure Passive Drag in Human Swimming.

    Directory of Open Access Journals (Sweden)

    Tiago M Barbosa

    Full Text Available The aim of this study was to compare the swimming hydrodynamics assessed with experimental and analytical procedures, as well as, to learn about the relative contributions of the friction drag and pressure drag to total passive drag. Sixty young talented swimmers (30 boys and 30 girls with 13.59±0.77 and 12.61±0.07 years-old, respectively were assessed. Passive drag was assessed with inverse dynamics of the gliding decay speed. The theoretical modeling included a set of analytical procedures based on naval architecture adapted to human swimming. Linear regression models between experimental and analytical procedures showed a high correlation for both passive drag (Dp = 0.777*Df+pr; R2 = 0.90; R2a = 0.90; SEE = 8.528; P<0.001 and passive drag coefficient (CDp = 1.918*CDf+pr; R2 = 0.96; R2a = 0.96; SEE = 0.029; P<0.001. On average the difference between methods was -7.002N (95%CI: -40.480; 26.475 for the passive drag and 0.127 (95%CI: 0.007; 0.247 for the passive drag coefficient. The partial contribution of friction drag and pressure drag to total passive drag was 14.12±9.33% and 85.88±9.33%, respectively. As a conclusion, there is a strong relationship between the passive drag and passive drag coefficient assessed with experimental and analytical procedures. The analytical method is a novel, feasible and valid way to gather insight about one's passive drag during training and competition. Analytical methods can be selected not only to perform race analysis during official competitions but also to monitor the swimmer's status on regular basis during training sessions without disrupting or time-consuming procedures.

  13. Impact of atmospheric and oceanic form drag parameterization on simulations of Arctic sea ice

    Science.gov (United States)

    Tsamados, Michel; Feltham, Daniel L.; Schroeder, David. F.; Farrell, Sinead L.; Kurtz, Nathan T.; Laxon, Seymour W.

    2013-04-01

    Pressure ridges, keels, floe edges and melt pond edges all introduce discrete obstructions to the flow of the air or ocean over the ice, and are a source of form drag. For typical ice covers the form drag contribution to the total drag is of comparable or greater magnitude to the surface or skin drag. In current climate models form drag is only accounted for by tuning of the air-ice and air-ocean drag coefficients, i.e. by altering the roughness length in a surface drag parameterization. The existing approach of skin drag parameter tuning, while numerically convenient, is poorly constrained by observations and fails to describe correctly the physics associated with the air-ice and ocean-ice drag. Here we combine recent theoretical developments to deduce the total neutral form drag coefficients from the key parameters of the ice cover such as ice concentration, size and area of the ridges and keels, freeboard and floe draft and size of melt ponds. We incorporate the drag coefficients into the sea ice component of a climate model (the CICE model). This stage necessitates that the sea ice characteristics obtained locally from observations are mapped to the averaged sea ice quantities provided by the sea ice model at the larger grid cell length scale. We present results over the Arctic of a stand-alone version of the model and show the influence of the new drag parameterization on the motion and mass of the ice cover. The new parameterization allows the drag coefficients to be coupled to the sea ice state and therefore to evolve spatially and temporally. We test the predictions of the model against measured drag coefficients in several regions of the Arctic and find good agreement between model and observations.

  14. High-level Petri Nets

    DEFF Research Database (Denmark)

    High-level Petri nets are now widely used in both theoretical analysis and practical modelling of concurrent systems. The main reason for the success of this class of net models is that they make it possible to obtain much more succinct and manageable descriptions than can be obtained by means...... of low-level Petri nets - while, on the other hand, they still offer a wide range of analysis methods and tools. The step from low-level nets to high-level nets can be compared to the step from assembly languages to modern programming languages with an elaborated type concept. In low-level nets...... there is only one kind of token and this means that the state of a place is described by an integer (and in many cases even by a boolean). In high-level nets each token can carry a complex information/data - which, e.g., may describe the entire state of a process or a data base. Today most practical...

  15. Air-ice drag coefficients in the western Weddell Sea: 2. A model based on form drag and drifting snow

    Science.gov (United States)

    Andreas, Edgar L.

    1995-03-01

    In part 1 (Andreas and Claffey, this issue) we observed some characteristics of the neutral stability air-ice drag coefficient at a reference height of 10 m (CDN10) that had not been documented before. Our main conclusion was that wind-driven snow continually alters the sea ice surface; the resulting snowdrifts determine how large CDN10 is. In particular, part 1 reported three observations that I would like to explain. (1) CDN10 is near 1.5×10-3 when the wind is well aligned with the drifted snow. (2) CDN10 is near 2.5×10-3 when the wind makes a large angle with the dominant orientation of the snowdrifts. (3) CDN10 can increase by 20% if, after being well aligned with the drift patterns, the mean wind direction shifts by as little as 20°. To investigate this behavior of CDN10 here I adapt a model developed by Raupach (1992) that partitions the total surface stress into contributions from form drag and skin friction. An essential part of this development was extending Raupach's model to the more complex geometry of sastrugi-like roughness elements. Assuming that 10-cm high sastrugi cover 15% of the surface, this physically based model reproduces the three main observations listed above. Thus the model seems to include the basic physics of air-ice momentum exchange. The main conclusion from this modeling is that 10-cm, sastrugilike snowdrifts, rather than pressure ridges, sustain most of the form drag over compact sea ice in the western Weddell Sea. Secondly, the modeling suggests that skin friction accounts for about 60% of the surface stress when the wind is well aligned with the sastrugi; but when the wind is not well aligned, form drag accounts for about 80% of the stress. The sastrugi are thus quite effective in streamlining the surface.

  16. Pro asynchronous programming with .NET

    CERN Document Server

    Blewett, Richard; Ltd, Rock Solid Knowledge

    2014-01-01

    Pro Asynchronous Programming with .NET teaches the essential skill of asynchronous programming in .NET. It answers critical questions in .NET application development, such as: how do I keep my program responding at all times to keep my users happy how do I make the most of the available hardware how can I improve performanceIn the modern world, users expect more and more from their applications and devices, and multi-core hardware has the potential to provide it. But it takes carefully crafted code to turn that potential into responsive, scalable applications.With Pro Asynchronous Programming

  17. Conformal Nets II: Conformal Blocks

    Science.gov (United States)

    Bartels, Arthur; Douglas, Christopher L.; Henriques, André

    2017-08-01

    Conformal nets provide a mathematical formalism for conformal field theory. Associated to a conformal net with finite index, we give a construction of the `bundle of conformal blocks', a representation of the mapping class groupoid of closed topological surfaces into the category of finite-dimensional projective Hilbert spaces. We also construct infinite-dimensional spaces of conformal blocks for topological surfaces with smooth boundary. We prove that the conformal blocks satisfy a factorization formula for gluing surfaces along circles, and an analogous formula for gluing surfaces along intervals. We use this interval factorization property to give a new proof of the modularity of the category of representations of a conformal net.

  18. Micro-holes for fuel savings: Lasers reduce drag; Mit Mikroloechern sparsam fliegen: Laser verringern den Luftwiderstand

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1999-07-01

    Research engineers at DaimlerChrysler Aerospace Airbus have developed a new technology which may result in 16 percent fuel savings in big aeroplanes. The aeroplane skin is perforated using laser technology, and the surface air is sucked off for a drastic reduction of drag. [German] Forscher von DaimlerChrysler Aerospace Airbus haben jetzt eine neue Technik entwickelt, mit der sie in Zukunft den Treibstoffverbrauch von grossen Flugzeugen um rund 16 Prozent reduzieren koennten. Der Trick dabei: Mit Lasern perforieren sie die Flugzeughaut, saugen die Luft an deren Oberflaeche ab und senken so drastisch den Luftwiderstand. (orig.)

  19. No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1

    Science.gov (United States)

    Argus, Donald F.; Gordon, Richard G.

    1991-01-01

    NNR-NUVEL1 is presented which is a model of plate velocities relative to the unique reference frame defined by requiring no-net-rotation of the lithosphere while constraining relative plate velocities to equal those in global plate motion model NUVEL-1 (DeMets et al., 1990). In NNR-NUVEL1, the Pacific plate rotates in a right-handed sense relative to the no-net-rotation reference frame at 0.67 deg/m.y. about 63 deg S, 107 deg E. At Hawaii the Pacific plate moves relative to the no-net-rotation reference frame at 70 mm/yr, which is 25 mm/yr slower than the Pacific plate moves relative to the hotspots. Differences between NNR-NUVEL1 and HS2-NUVEL1 are described. The no-net-rotation reference frame differs significantly from the hotspot reference frame. If the difference between reference frames is caused by motion of the hotspots relative to a mean-mantle reference frame, then hotspots beneath the Pacific plate move with coherent motion towards the east-southeast. Alternatively, the difference between reference frames can show that the uniform drag, no-net-torque reference frame, which is kinematically equivalent to the no-net-rotation reference frame, is based on a dynamically incorrect premise.

  20. No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1

    Science.gov (United States)

    Argus, Donald F.; Gordon, Richard G.

    1991-11-01

    NNR-NUVEL1 is presented which is a model of plate velocities relative to the unique reference frame defined by requiring no-net-rotation of the lithosphere while constraining relative plate velocities to equal those in global plate motion model NUVEL-1 (DeMets et al., 1990). In NNR-NUVEL1, the Pacific plate rotates in a right-handed sense relative to the no-net-rotation reference frame at 0.67 deg/m.y. about 63 deg S, 107 deg E. At Hawaii the Pacific plate moves relative to the no-net-rotation reference frame at 70 mm/yr, which is 25 mm/yr slower than the Pacific plate moves relative to the hotspots. Differences between NNR-NUVEL1 and HS2-NUVEL1 are described. The no-net-rotation reference frame differs significantly from the hotspot reference frame. If the difference between reference frames is caused by motion of the hotspots relative to a mean-mantle reference frame, then hotspots beneath the Pacific plate move with coherent motion towards the east-southeast. Alternatively, the difference between reference frames can show that the uniform drag, no-net-torque reference frame, which is kinematically equivalent to the no-net-rotation reference frame, is based on a dynamically incorrect premise.

  1. Lift, Drag and Flow-field Measurements around a Single-degree-of-freedom Toy Ornithopter

    Science.gov (United States)

    Chavez Alarcon, Ramiro; Balakumar, B. J.; Allen, James

    2010-11-01

    The aerodynamics of a flight-worthy toy ornithopter under laminar inflow conditions are studied using a combination of load cell, flow visualization, high speed camera and PIV experiments. All the experiments were performed in the large wind tunnel facility at New Mexico State University, with the exception of a free flight test of the model. Measurements from a six-axis load cell were used to capture the variation of the lift and drag forces at various angles of attack, flapping frequencies and free-speed velocities. Smoke visualization is used to clearly demonstrate that the momentum flux in the downward direction during downstroke exceeds the upward momentum flux during upstroke due to the flexion of the wing and its angle of attack. This net surplus creates the lift in such ornithopter designs despite the stroke symmetry. PIV measurements are then performed at suitable locations to identify flow structures around the wing at various spanwise locations. A control volume analysis is performed to compare the momentum deficit in the wake to the load cell measurements.

  2. 10 CFR 300.7 - Net emission reductions.

    Science.gov (United States)

    2010-01-01

    ... the likely direct and indirect effects of the actions taken to reduce greenhouse gas emissions. (d... DEPARTMENT OF ENERGY CLIMATE CHANGE VOLUNTARY GREENHOUSE GAS REPORTING PROGRAM: GENERAL GUIDELINES § 300.7... gases listed in the definition of “greenhouse gases” in § 300.2 are eligible for registration. (b...

  3. Petri Net Tool Overview 1986

    DEFF Research Database (Denmark)

    Jensen, Kurt; Feldbrugge, Frits

    1987-01-01

    This paper provides an overview of the characteristics of all currently available net based tools. It is a compilation of information provided by tool authors or contact persons. A concise one page overview is provided as well....

  4. Understanding Net Zero Energy Buildings

    DEFF Research Database (Denmark)

    Salom, Jaume; Widén, Joakim; Candanedo, José

    2011-01-01

    Although several alternative definitions exist, a Net-Zero Energy Building (Net ZEB) can be succinctly described as a grid-connected building that generates as much energy as it uses over a year. The “net-zero” balance is attained by applying energy conservation and efficiency measures...... and by incorporating renewable energy systems. While based on annual balances, a complete description of a Net ZEB requires examining the system at smaller time-scales. This assessment should address: (a) the relationship between power generation and building loads and (b) the resulting interaction with the power grid....... This paper presents and categorizes quantitative indicators suitable to describe both aspects of the building’s performance. These indicators, named LMGI - Load Matching and Grid Interaction indicators, are easily quantifiable and could complement the output variables of existing building simulation tools...

  5. PolicyNet Publication System

    Data.gov (United States)

    Social Security Administration — The PolicyNet Publication System project will merge the Oracle-based Policy Repository (POMS) and the SQL-Server CAMP system (MSOM) into a new system with an Oracle...

  6. KM3NeT

    CERN Multimedia

    KM3NeT is a large scale next-generation neutrino telescope located in the deep waters of the Mediterranean Sea, optimized for the discovery of galactic neutrino sources emitting in the TeV energy region.

  7. Net Neutrality: Background and Issues

    National Research Council Canada - National Science Library

    Gilroy, Angele A

    2006-01-01

    .... The move to place restrictions on the owners of the networks that compose and provide access to the Internet, to ensure equal access and nondiscriminatory treatment, is referred to as "net neutrality...

  8. Wingtip Vortices and Free Shear Layer Interaction in the Vicinity of Maximum Lift to Drag Ratio Lift Condition

    Science.gov (United States)

    Memon, Muhammad Omar

    identified. Improved understanding of this relationship could be extended not only to improve aircraft performance through the reduction of lift induced drag, but also to air vehicle performance in off-design cruise conditions.

  9. Petri Nets in Cryptographic Protocols

    DEFF Research Database (Denmark)

    Crazzolara, Federico; Winskel, Glynn

    2001-01-01

    A process language for security protocols is presented together with a semantics in terms of sets of events. The denotation of process is a set of events, and as each event specifies a set of pre and postconditions, this denotation can be viewed as a Petri net. By means of an example we illustrate...... how the Petri-net semantics can be used to prove security properties....

  10. The Economics of Net Neutrality

    OpenAIRE

    Hahn, Robert W.; Wallsten, Scott

    2006-01-01

    This essay examines the economics of "net neutrality" and broadband Internet access. We argue that mandating net neutrality would be likely to reduce economic welfare. Instead, the government should focus on creating competition in the broadband market by liberalizing more spectrum and reducing entry barriers created by certain local regulations. In cases where a broadband provider can exercise market power the government should use its antitrust enforcement authority to police anticompetitiv...

  11. A Mission-Adaptive Variable Camber Flap Control System to Optimize High Lift and Cruise Lift-to-Drag Ratios of Future N+3 Transport Aircraft

    Science.gov (United States)

    Urnes, James, Sr.; Nguyen, Nhan; Ippolito, Corey; Totah, Joseph; Trinh, Khanh; Ting, Eric

    2013-01-01

    Boeing and NASA are conducting a joint study program to design a wing flap system that will provide mission-adaptive lift and drag performance for future transport aircraft having light-weight, flexible wings. This Variable Camber Continuous Trailing Edge Flap (VCCTEF) system offers a lighter-weight lift control system having two performance objectives: (1) an efficient high lift capability for take-off and landing, and (2) reduction in cruise drag through control of the twist shape of the flexible wing. This control system during cruise will command varying flap settings along the span of the wing in order to establish an optimum wing twist for the current gross weight and cruise flight condition, and continue to change the wing twist as the aircraft changes gross weight and cruise conditions for each mission segment. Design weight of the flap control system is being minimized through use of light-weight shape memory alloy (SMA) actuation augmented with electric actuators. The VCCTEF program is developing better lift and drag performance of flexible wing transports with the further benefits of lighter-weight actuation and less drag using the variable camber shape of the flap.

  12. An Exploratory Investigation of the Effects of a Thin Plastic Film Cover on the Profile Drag of an Aircraft Wing Panel

    Science.gov (United States)

    Beasley, W. D.; Mcghee, R. J.

    1977-01-01

    Exploratory wind tunnel tests were conducted on a large chord aircraft wing panel to evaluate the potential for drag reduction resulting from the application of a thin plastic film cover. The tests were conducted at a Mach number of 0.15 over a Reynolds number range from about 7 x 10 to the 6th power to 63 x 10 to the 6th power.

  13. 26 CFR 1.904(f)-3 - Allocation of net operating losses and net capital losses.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 9 2010-04-01 2010-04-01 false Allocation of net operating losses and net....904(f)-3 Allocation of net operating losses and net capital losses. For rules relating to the allocation of net operating losses and net capital losses, see § 1.904(g)-3T. ...

  14. 29 CFR 4204.13 - Net income and net tangible assets tests.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false Net income and net tangible assets tests. 4204.13 Section....13 Net income and net tangible assets tests. (a) General. The criteria under this section are that either— (1) Net income test. The purchaser's average net income after taxes for its three most recent...

  15. Resistive Heating and Ion Drag in Saturn's Thermosphere

    Science.gov (United States)

    Vriesema, Jess William; Koskinen, Tommi; Yelle, Roger V.

    2017-10-01

    One of the most puzzling observations of the jovian planets is that the thermospheres of Jupiter, Saturn, Uranus and Neptune are all several times hotter than solar heating can account for (Strobel and Smith 1973; Yelle and Miller 2004; Muller-Wodarg et al. 2006). On Saturn, resistive heating appears sufficient to explain these temperatures in auroral regions, but the particular mechanism(s) responsible for heating the lower latitudes remains unclear. The most commonly proposed heating mechanisms are breaking gravity waves and auroral heating at the poles followed by redistribution of energy to mid-and low latitudes. Both of these energy sources are potentially important but also come with significant problems. Wave heating would have to be continuous and global to produce consistently elevated temperatures and the strong Coriolis forces coupled with polar ion drag appear to hinder redistribution of auroral energy (see Strobel et al. 2016 for review). Here we explore an alternative: wind-driven electrodynamics that can alter circulation and produce substantial heating outside of the auroral region. Smith (2013) showed this in-situ mechanism to be potentially significant in Jupiter’s thermosphere. We present new results from an axisymmetric, steady-state model that calculates resistive (Joule) heating rates through rigorous solutions of the electrodynamic equations for the coupled neutral atmosphere and ionosphere of Saturn. At present, we assume a dipole magnetic field and neglect any contributions from the magnetosphere. We use ion mixing ratios from the model of Kim et al. (2014) and the observed temperature-pressure profile from Koskinen et al. (2015) to calculate the generalized conductivity tensor as described by Koskinen et al. (2014). We calculate the current density under the assumption that it has no divergence and use it to calculate the resistive heating rates and ion drag. Our results suggest that resistive heating and ion drag at low latitudes likely

  16. Collisions and drag in debris discs with eccentric parent belts

    Science.gov (United States)

    Löhne, T.; Krivov, A. V.; Kirchschlager, F.; Sende, J. A.; Wolf, S.

    2017-08-01

    Context. High-resolution images of circumstellar debris discs reveal off-centred rings that indicate past or ongoing perturbation, possibly caused by secular gravitational interaction with unseen stellar or substellar companions. The purely dynamical aspects of this departure from radial symmetry are well understood. However, the observed dust is subject to additional forces and effects, most notably collisions and drag. Aims: To complement the studies of dynamics, we therefore aim to understand how the addition of collisional evolution and drag forces creates new asymmetries and strengthens or overrides existing ones. Methods: We augmented our existing numerical code Analysis of Collisional Evolution (ACE) by an azimuthal dimension, the longitude of periapse. A set of fiducial discs with global eccentricities ranging from 0 to 0.4 was evolved over gigayear timescales. Size distribution and spatial variation of dust were analysed and interpreted. We discuss the basic impact of belt eccentricity on spectral energy distributions and images. Results: We find features imposed on characteristic timescales. First, radiation pressure defines size cut-offs that differ between periapse and apoapse, resulting in an asymmetric halo. The differences in size distribution make the observable asymmetry of the halo depend on wavelength. Second, collisional equilibrium prefers smaller grains on the apastron side of the parent belt, reducing the effect of pericentre glow and the overall asymmetry. Third, Poynting-Robertson drag fills the region interior to an eccentric belt such that the apastron side is more tenuous. Interpretation and prediction of the appearance in scattered light is problematic when spatial and size distribution are coupled.

  17. Experimental analysis for aerodynamic drag of the electric locomotives

    Directory of Open Access Journals (Sweden)

    Ioan SEBESAN

    2013-09-01

    Full Text Available The purpose of this paper is to make a comparative analysis on the influence of the aerodynamic drag, in case of the electric rail vehicles for a series of situations encountered in exploitation. The article presents experimental results obtained following a geometric modelling at scale 1: 12, on a modular model for the electric locomotives LE 060EA 5100kW and LE-MA 060 TransMontana 6000kW. Tests were made at INCAS (National Institute for Aerospace Research “ElieCarafoli” in the subsonic wind tunnel.

  18. Measurements of drag and lift on smooth balls in flight

    Science.gov (United States)

    Cross, Rod; Lindsey, Crawford

    2017-07-01

    Measurements are presented on the drag and lift coefficients for three relatively smooth balls launched in air and tracked with two cameras separated horizontally by 6.4 m. The ball spin was varied in order to investigate whether the Magnus force would increase or decrease when the ball spin was increased. For one ball, the Magnus force increased. For another ball, the Magnus force decreased almost to zero after reaching a maximum. For the third ball, the Magnus force was negative at low ball spins and positive at high ball spins. For one of the balls, the ball spin increased with time as it travelled through the air.

  19. Ad/dressing the nation: drag and authenticity in post-apartheid South Africa.

    Science.gov (United States)

    Spruill, Jennifer

    2004-01-01

    This paper examines a style of drag in South Africa that features "traditional African" clothing. In a region in which homosexuality is denigrated as a colonial, European import and "unAfrican," the meaning of "traditional drag" is deeply inflected by the question of cultural authenticity. This dragging practice fits within a distinctly post-colonial production of tradition and its self-conscious display--in the form of attire--of a decidedly "gay" one. Traditional drag also responds to ongoing politics within and between lesbian and gay communities about racial "representivity" and "transformation." The paper focuses on displays of traditional drag at Johannesburg's Gay and Lesbian Pride Parade but also explores the complex politics of publicity and address suggested by varying contexts in which traditional dress and drag are mobilized.

  20. Drag Identification & Reduction Technology (DIRECT) for Elastically Shaped Air Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA and Boeing Phantom Works have been working on the Elastically Shaped Future Vehicle Concept (ESFVC) and have shown that aircraft with elastically shaped wings...

  1. Aerodynamic Drag Reduction Technologies Testing of Heavy-Duty Vocational Vehicles and a Dry Van Trailer

    Energy Technology Data Exchange (ETDEWEB)

    Ragatz, Adam [National Renewable Energy Lab. (NREL), Golden, CO (United States); Thornton, Matthew [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-10-01

    This study focused on two accepted methods for quantifying the benefit of aerodynamic improvement technologies on vocational vehicles: the coastdown technique, and on-road constant speed fuel economy measurements. Both techniques have their advantages. Coastdown tests are conducted over a wide range in speed and allow the rolling resistance and aerodynamic components of road load force to be separated. This in turn allows for the change in road load and fuel economy to be estimated at any speed, as well as over transient cycles. The on-road fuel economy measurements only supply one lumped result, applicable at the specific test speed, but are a direct measurement of fuel usage and are therefore used in this study as a check on the observed coastdown results. Resulting coefficients were then used to populate a vehicle model and simulate expected annual fuel savings over real-world vocational drive cycles.

  2. Fabrication Development and Flow Testing of Underwater Superhydrophobic Films for Drag Reduction

    Science.gov (United States)

    2017-03-21

    characterization 3.1 Develop shear sensor for direct measurement of skin friction 3.2 Characterize developed surfaces using in-house water tunnel 3.3 Prepare...sensor for direct measurement of skin friction • In development stage, many different SHPo surfaces need to be evaluated • Manufacturing of the many...Task 2: Develop scalable fabrication of self-sustainable SHPo film 2.1 Develop whole-Teflon hot embossing for optimized passive surface 2.2 Develop

  3. Ultra fast laser machined hydrophobic stainless ateel surface for drag reduction in laminar flows

    NARCIS (Netherlands)

    Jagdheesh, R.; Pathiraj, B.; Martin, A.G.; Del Cerro, D.A.; Lammertink, R.G.H.; Lohse, D.; Huis in 't Veld, A.J.; Römer, G.R.B.E.

    2010-01-01

    Hydrophobic surfaces have attracted much attention due to their potential in microfluidics, lab on chip devices and as functional surfaces for the automotive and aerospace industry. The combination of a dual scale roughness with an inherent low-surface-energy coating material is the pre-requisite

  4. Study of Viscosity and Friction Factor of Nano Drilling Fluids along with Torque and Drag Reduction

    OpenAIRE

    Irfan, Yasir

    2016-01-01

    Master's thesis in Petroleum engineering Energy industries have been taking advantages from the recent developments of nanotechnology. Several revolutionary changes can be made in drilling industry with the help of nanotechnology. It has a capability to produce such nanomaterials that can bring benefit to the industry in various manners such as improving the quality of mud cake, decreasing the frictional resistance in the well, minimizing the risk of pipe sticking, establishing borehole s...

  5. High Reynolds Number Micro-Bubble and Polymer Drag Reduction Experiments

    Science.gov (United States)

    2008-01-01

    test model. Appendix A: Smooth-Flat-Plate Turbulent Boundary Layer Measurements at High Reynolds Number Ghanem F. Oweis’, Eric S. Winkel’, James M...a 15’-full-angle triangular wedge of 0.6- m length that was terminated at 25 mm thickness with 400 bevel angle. This asymmetric trailing edge design

  6. Copolymers for Drag Reduction in Marie Propulsion: New Molecular Structures with Enhanced Effectiveness

    Science.gov (United States)

    1991-05-31

    monomer. Sodium dodecyl sulfate was the surfactant in this acknowledged. 573 References 1. McCormick, C. L. and Johnson, C. B. PMSE , 55, 366 (1986). 2...Preprints, 30(2), 348 (1989). 4. Valint, P. L., Jr.; Bock, J. and Schulz, D. N. PMSE , 482 (1987). 5. McCormick, C. L. and Blackmon, K P. J. Polym. Si. Polym...constant shear rate of 4. Ezzell, S. A.; and McCormick, C. L., Polym. Prepr., 30(2), 6 sc’. 340 (1989). 5. Peer, W. J., PMSE , 57, 492 (1987). AM-APS

  7. Friction Drag Reduction Using Superhydrophobic Surface in High Reynolds Number Turbulent Flow

    Science.gov (United States)

    2017-12-25

    decided, as part of the overall research strategy on SLIPS surfaces, and with the advice and consultation of the Program Manager Dr. Ki...Aizenberg); Innovators Under 35, MIT Technology Review 2014 (Wong); DARPA Young Faculty Award 2014 (Wong); NSF CAREER Award 2014 (Wong

  8. Drag reduction by air release promotes fast ascent in jumping emperor penguins—a novel hypothesis

    DEFF Research Database (Denmark)

    Davenport, J.; Hughes, R.N.; Shorten, M

    2011-01-01

    To jump out of water onto sea ice, emperor penguins must achieve sufficient underwater speed to overcome the influence of gravity when they leave the water. The relevant combination of density and kinematic viscosity of air is much lower than for water. Injection of air into boundary layers (‘air...

  9. Copolymers for Drag Reduction in Marine Propulsion: New Molecular Structures with Enhanced Effectiveness

    Science.gov (United States)

    1992-05-31

    Avaiabihity - Avail ’ , , Dist So:... A. Papers Submitted to Refereed Journals ’Water-Soluble Copolymers. 26. Fluorescence Probe Studies of...Sodium I-Pyrenesulfouate (7).Amer meoves intocpcte nti tdi rvdsa literature methods was modified for the preparation of sodium fluorecence label for...but, though fluorescence probes and labels have been used to importantly, is readily solubilized by sodium dodecyl study organization, we know of no

  10. Torque and Drag Friction Model: Implemented Friction Factor Dependency of Temperature

    OpenAIRE

    Brekke, Alexander

    2016-01-01

    Master's thesis in Petroleum engineering We investigated the friction factor dependency of temperature. “Friction factor” is a parameter in the calculations of torque and drag. Increased well reach is dependent on accurate torque and drag modeling. We proposed that the friction factor can be dependent on temperature other than linear approximations as studied by Kaarstad et al. [2009]. The results was implemented in the work of Aadnoy [2006] torque and drag 3D model. The local friction fac...

  11. Experimental Investigation of the Fresnel Drag Effect in RF Coaxial Cables

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2011-01-01

    Full Text Available An experiment that confirms the Fresnel drag formalism in RF coaxial cables is re- ported. The Fresnel ‘drag’ in bulk dielectrics and in optical fibers has previously been well established. An explanation for this formalism is given, and it is shown that there is no actual drag phenomenon, rather that the Fresnel drag effect is merely the conse- quence of a simplified description of EM scattering within a dielectric in motion wrt the dynamical 3-space. The Fresnel drag effect plays a critical role in the design of various light-speed anisotropy detectors.

  12. Modelling of Structural Loads in Drag Augmented Space Debris Removal Concepts

    DEFF Research Database (Denmark)

    Kristensen, Anders Schmidt; Nikolajsen, Jan Ánike; Lauridsen, Peter Riddersholm

    2017-01-01

    A Self-deployable Deorbiting Space Structure (SDSS) is used for drag augmented space debris removal. A highly flexible frame allows for a folding of the structure by bifurcation. This research models the structural loads during the deployment and unfolding of the drag sail in Low Earth Orbit (LEO......). The Spacecraft travels with 7.8 km/s at deployment. As the drag sail unfolds instantaneously the structure must withstand the loads from the unfolding and the drag. Thermal loads are included in the FEA as the temperature varies from -80°C to +80°C during deorbit. The results are used to verify the structural...

  13. Horseshoe Drag in Three-dimensional Globally Isothermal Disks

    Science.gov (United States)

    Masset, F. S.; Benítez-Llambay, P.

    2016-01-01

    We study the horseshoe dynamics of a low-mass planet in a three-dimensional, globally isothermal, inviscid disk. We find, as reported in previous work, that the boundaries of the horseshoe region (separatrix sheets) have cylindrical symmetry about the disk’s rotation axis. We interpret this feature as arising from the fact that the whole separatrix sheets have a unique value of Bernoulli’s constant, and that this constant does not depend on altitude, but only on the cylindrical radius, in barotropic disks. We next derive an expression for the torque exerted by the horseshoe region on the planet, or horseshoe drag. Potential vorticity is not materially conserved as in two-dimensional flows, but it obeys a slightly more general conservation law (Ertel’s theorem) that allows an expression for the horseshoe drag identical to the expression in a two-dimensional disk to be obtained. Our results are illustrated and validated by three-dimensional numerical simulations. The horseshoe region is found to be slightly narrower than previously extrapolated from two-dimensional analyses with a suitable softening length of the potential. We discuss the implications of our results for the saturation of the corotation torque, and the possible connection to the flow at the Bondi scale, which the present analysis does not resolve.

  14. Riblets show most promise for reducing drag in pipelines

    Energy Technology Data Exchange (ETDEWEB)

    May, R. [HR Wallingford, Oxfordshire (United Kingdom)

    1996-08-01

    Flow resistance in pipes and conduits is a fundamental factor governing the design of any pipeline system and the economics of its operation. If the hydraulic resistance can be reduced, savings can be made in the size of pipes used, in pumping costs or in the gradients at which gravity pipes need to be laid. According to the well-established Colebrook-White equation, the drag exerted by pipe walls consists of two components: that due to the viscosity of the fluid, which tends to dominate at low velocity; and that due to the surface texture of walls which is dominant at high velocity. For this reason, most manufacturers aim to maximize the flow capacity of their pipes by producing the smoothest possible surface finish consistent with the materials and manufacturing techniques being used. The paper describes hydraulic roughness in pipes and reducing drag resistance with the use of riblets, which are small, longitudinal grooves formed on the internal walls of the pipe.

  15. Incorporating modelled subglacial hydrology into inversions for basal drag

    Directory of Open Access Journals (Sweden)

    C. P. Koziol

    2017-12-01

    Full Text Available A key challenge in modelling coupled ice-flow–subglacial hydrology is initializing the state and parameters of the system. We address this problem by presenting a workflow for initializing these values at the start of a summer melt season. The workflow depends on running a subglacial hydrology model for the winter season, when the system is not forced by meltwater inputs, and ice velocities can be assumed constant. Key parameters of the winter run of the subglacial hydrology model are determined from an initial inversion for basal drag using a linear sliding law. The state of the subglacial hydrology model at the end of winter is incorporated into an inversion of basal drag using a non-linear sliding law which is a function of water pressure. We demonstrate this procedure in the Russell Glacier area and compare the output of the linear sliding law with two non-linear sliding laws. Additionally, we compare the modelled winter hydrological state to radar observations and find that it is in line with summer rather than winter observations.

  16. Gliding flight: drag and torque of a hawk and a falcon with straight and turned heads, and a lower value for the parasite drag coefficient.

    Science.gov (United States)

    Tucker, V A

    2000-12-01

    Raptors - falcons, hawks and eagles in this study - such as peregrine falcons (Falco peregrinus) that attack distant prey from high-speed dives face a paradox. Anatomical and behavioral measurements show that raptors of many species must turn their heads approximately 40 degrees to one side to see the prey straight ahead with maximum visual acuity, yet turning the head would presumably slow their diving speed by increasing aerodynamic drag. This paper investigates the aerodynamic drag part of this paradox by measuring the drag and torque on wingless model bodies of a peregrine falcon and a red-tailed hawk (Buteo jamaicensis) with straight and turned heads in a wind tunnel at a speed of 11.7 m s(-)(1). With a turned head, drag increased more than 50 %, and torque developed that tended to yaw the model towards the direction in which the head pointed. Mathematical models for the drag required to prevent yawing showed that the total drag could plausibly more than double with head-turning. Thus, the presumption about increased drag in the paradox is correct. The relationships between drag, head angle and torque developed here are prerequisites to the explanation of how a raptor could avoid the paradox by holding its head straight and flying along a spiral path that keeps its line of sight for maximum acuity pointed sideways at the prey. Although the spiral path to the prey is longer than the straight path, the raptor's higher speed can theoretically compensate for the difference in distances; and wild peregrines do indeed approach prey by flying along curved paths that resemble spirals. In addition to providing data that explain the paradox, this paper reports the lowest drag coefficients yet measured for raptor bodies (0.11 for the peregrine and 0.12 for the red-tailed hawk) when the body models with straight heads were set to pitch and yaw angles for minimum drag. These values are markedly lower than value of the parasite drag coefficient (C(D,par)) of 0.18 previously

  17. Effect of windshield shape of a pilot's canopy on the drag of an NACA RM-2 drag research model in flight at transonic speeds

    Science.gov (United States)

    ALEXANDER SIDNEY R

    1948-01-01

    Results of flight tests of an NACA RM-2 drag research model equipped with a pilot's canopy having a vee windshield are presented for a Mach number range from 0.75 to 1.43. Comparison is made with test results of a similar canopy having a flat windshield. The vee-windshield canopy produced lower drag-coefficient values than the flat-windshield canopy for Mach numbers from 0.85 to about 1.2. From M - 1.2 to 1.4 both canopies produced the same drag coefficient.

  18. September 2002 Working Group Meeting on Heavy Vehicle Aerodynamic Drag: Presentations and Summary of Comments and Conclusions

    Energy Technology Data Exchange (ETDEWEB)

    McCallen, R

    2002-09-01

    report. Sid Diamond of DOE discussed the reorganization of the Office of Energy Efficiency and Renewable Energy and that the Office of Heavy Vehicle Technology is now part of the Office of FreedomCAR & Vehicle Technologies. Sid reviewed the FY03 budget and provided information on some plans for FY04. The soon to be posted DOE request for proposals from industry for projects related to parasitic energy losses was discussed. A minimum of 50% cost share by industry will be required and the proposal must be submitted by industry. Collaborative efforts in aerodynamic drag with members of the DOE consortium are encouraged. Sid also mentioned interest in aerodynamic drag contribution due to wheel wells and underbody flow. Sid also mentioned his continued interest in the application of our computational and experimental expertise to the area of locomotive and railcar aerodynamics for the reduction of drag effects and thus, the reduction of fuel consumption by trains. In summary, the technical presentations at the meeting included a review of experimental results and plans by GTRI, USC, and NASA Ames, the computational results from LLNL and SNL for the integrated tractor-trailer benchmark geometry called the Ground Transportation System (GTS) model, and by LLNL for the tractor-trailer gap and trailer wake flow, and turbulence model development and benchmark simulations being investigated by Caltech. USC is also investigating an acoustic drag reduction device that has been named ''Mozart'', GTRI continues their investigation of a blowing device, and LLNL presented their ideas for 2 new base drag reduction devices. ANL presented their plans for a DOE supported Cooperative Research and Development Agreement (CRADA) with Paccar Truck Company utilizing commercial software tools to simulate the flow and drag for an actual tractor and showed the results of some preliminary griding attempts. The attendees also had the opportunity to tour the 12-ft pressure wind tunnel

  19. TimeNET Optimization Environment

    Directory of Open Access Journals (Sweden)

    Christoph Bodenstein

    2015-12-01

    Full Text Available In this paper a novel tool for simulation-based optimization and design-space exploration of Stochastic Colored Petri nets (SCPN is introduced. The working title of this tool is TimeNET Optimization Environment (TOE. Targeted users of this tool are people modeling complex systems with SCPNs in TimeNET who want to find parameter sets that are optimal for a certain performance measure (fitness function. It allows users to create and simulate sets of SCPNs and to run different optimization algorithms based on parameter variation. The development of this tool was motivated by the need to automate and speed up tests of heuristic optimization algorithms to be applied for SCPN optimization. A result caching mechanism is used to avoid recalculations.

  20. Implementing NetScaler VPX

    CERN Document Server

    Sandbu, Marius

    2014-01-01

    An easy-to-follow guide with detailed step-by step-instructions on how to implement the different key components in NetScaler, with real-world examples and sample scenarios.If you are a Citrix or network administrator who needs to implement NetScaler in your virtual environment to gain an insight on its functionality, this book is ideal for you. A basic understanding of networking and familiarity with some of the different Citrix products such as XenApp or XenDesktop is a prerequisite.

  1. Net4Care PHMR Library

    DEFF Research Database (Denmark)

    2014-01-01

    The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the SimpleClinicalDocument......The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the Simple...

  2. Pro DLR in NET 4

    CERN Document Server

    Wu, Chaur

    2011-01-01

    Microsoft's Dynamic Language Runtime (DLR) is a platform for running dynamic languages such as Ruby and Python on an equal footing with compiled languages such as C#. Furthermore, the runtime is the foundation for many useful software design and architecture techniques you can apply as you develop your .NET applications. Pro DLR in .NET 4 introduces you to the DLR, showing how you can use it to write software that combines dynamic and static languages, letting you choose the right tool for the job. You will learn the core DLR components such as LINQ expressions, call sites, binders, and dynami

  3. Hierarchies in Coloured Petri Nets

    DEFF Research Database (Denmark)

    Huber, Peter; Jensen, Kurt; Shapiro, Robert M.

    1991-01-01

    The paper shows how to extend Coloured Petri Nets with a hierarchy concept. The paper proposes five different hierarchy constructs, which allow the analyst to structure large CP-nets as a set of interrelated subnets (called pages). The paper discusses the properties of the proposed hierarchy...... constructs, and it illustrates them by means of two examples. The hierarchy constructs can be used for theoretical considerations, but their main use is to describe and analyse large real-world systems. All of the hierarchy constructs are supported by the editing and analysis facilities in the CPN Palette...

  4. Time Resolved PIV Investigation on the Skin Friction Reduction Mechanism of Outer-Layer Vertical Blades Array

    Directory of Open Access Journals (Sweden)

    Seong Hyeon Park

    2015-02-01

    Full Text Available The drag reducing efficiency of the outer-layer vertical blades, which were first devised by Hutchins (2003, have been demonstrated by the recent towing tank measurements. From the drag measurement of flat plate with various vertical blades arrays by Park et al. (2011, a maximum 9.6% of reduction of total drag was achieved. The scale of blade geometry is found to be weakly correlated with outer variable of boundary layer. The drag reduction of 2.8% has been also confirmed by the model ship test by An et al. (2014. With a view to enabling the identification of drag reduction mechanism of the outer-layer vertical blades, detailed flow field measurements have been performed using 2D time resolved PIV in this study. It is found that the skin friction reduction effect is varied according to the spanwise position, with 2.73% and 7.95% drag reduction in the blade plane and the blade-in-between plane, respectively. The influence of vertical blades array upon the characteristics of the turbulent coherent structures was analyzed by POD method. It is observed that the vortical structures are cut and deformed by blades array and the skin frictional reduction is closely associated with the subsequent evolution of turbulent structures.

  5. Efficacy of the Olyset Duo net against insecticide-resistant mosquito vectors of malaria.

    Science.gov (United States)

    Ngufor, Corine; N'Guessan, Raphael; Fagbohoun, Josias; Todjinou, Damien; Odjo, Abibath; Malone, David; Ismail, Hanafy; Akogbeto, Martin; Rowland, Mark

    2016-09-14

    Olyset Duo is a new long-lasting insecticidal net treated with permethrin (a pyrethroid) and pyriproxyfen, an insect growth regulator that disrupts the maturation of oocytes in mosquitoes exposed to the net. We tested the Olyset Duo net against pyrethroid-resistant Anopheles gambiae mosquitoes, which transmit malaria parasites, in laboratory bioassays and in a trial in Benin using experimental huts that closely resemble local habitations. Host-seeking mosquitoes that entered to feed were free to contact the occupied nets and were collected the next morning from exit traps. Surviving blood-fed mosquitoes were observed for effects on reproduction. Control nets were treated with pyrethroid only or pyriproxyfen only, and nets were tested unwashed and after 20 standardized washes. The Olyset Duo net showed improved efficacy and wash resistance relative to the pyrethroid-treated net in terms of mosquito mortality and prevention of blood feeding. The production of offspring among surviving blood-fed A. gambiae in the hut trial was reduced by the pyriproxyfen-treated net and the Olyset Duo net both before washing (90 and 71% reduction, respectively) and after washing (38 and 43% reduction, respectively). The degree of reproductive suppression in the hut trial was predicted by laboratory tunnel tests but not by cone bioassays. The overall reduction in reproductive rate of A. gambiae with the Olyset Duo net in the trial was 94% with no washing and 78% after 20 washes. The Olyset Duo net has the potential to provide community control of mosquito populations and reduce malaria transmission in areas of high insecticide resistance. Copyright © 2016, American Association for the Advancement of Science.

  6. Surface pressure drag for hydrostatic two-layer flow over axisymmetric mountains

    Energy Technology Data Exchange (ETDEWEB)

    Leutbecher, M.

    2000-07-01

    The effect of partial reflections on surface pressure drag is investigated for hydrostatic gravity waves in two-layer flow with piecewise constant buoyancy frequency. The variation of normalized surface pressure drag with interface height is analyzed for axisymmetric mountains. The results are compared with the familiar solution for infinitely long ridges. The drag for the two-layer flow is normalized with the drag of one-layer flow, which has the buoyancy frequency of the lower layer. An analytical expression for the normalized drag of axisymmetric mountains is derived from linear theory of steady flow. Additionally, two-layer flow over finite-height axisymmetric mountains is simulated numerically for flow with higher stability in the upper layer. The temporal evolution of the surface pressure drag is examined in a series of experiments with different interface and mountain heights. The focus is on the linear regime and the nonlinear regime of nonbreaking gravity waves. The dispersion of gravity waves in flow over isolated mountains prevents that the entire wave spectrum is in resonance at the same interface height, which is the case in hydrostatic flow over infinitely long ridges. In consequence, the oscillation of the normalized drag with interface height is smaller for axisymmetric mountains than for infinitely long ridges. However, even for a reflection coefficient as low as 1/3 the drag of an axisymmetric mountain can be amplified by 50% and reduced by 40%. The nonlinear drag becomes steady in the numerical experiments in which no wave breaking occurs. The steady state nonlinear drag agrees quite well with the prediction of linear theory if the linear drag is computed for a slightly lowered interface. (orig.)

  7. Surface drag over the snow surface of the Antarctic Plateau. 1. Factors controlling surface drag over the Katabatic wind region

    Science.gov (United States)

    Inoue, Jiro

    1989-02-01

    The drag coefficient of the snow surface over the Antarctic Plateau is evaluated through direct measurement of Reynolds stress on the Mizuho Plateau, East Antarctica, in the austral summer. The estimated roughness height (Z0) varies from 10-l to 10-4 cm, even under near-neutral conditions. Large shear stress appears in light wind, followed by increased turbulent intensity. In the katabatic wind region of the plateau, Z0 shows symmetric changes with wind direction. The average value of Z0 in the smoothest direction is 0.0004 cm, which is the minimum value previously reported, and it increases to 0.015 cm for 40° rotation of wind direction toward the roughest direction. The directional dependence of Z0 is similar at three stations located nearly 100 km apart. Unlike the results of Jackson and Carroll at the south pole, the smoothest direction deviates 20° from the mean sastrugi axes and agrees with the direction of the prevailing high wind. The 4-m neutral drag coefficient is estimated to be 0.8 × 10-3 for the smoothest direction and 1.5 × 10-3 for the roughest direction. The effect of snow drift is unimportant. A generalized discussion of the results is given in a companion paper.

  8. Flat Plate Reduction in a Water Tunnel Using Riblets

    Science.gov (United States)

    1987-05-01

    Cononue onreee dnaessey end defyy blod numbr) FIEL / 9 GROUP SUB.GROUP Drag reduction /inTurbulent boundary layer // Streamwie microgroove surface...and its leading edge were separately constructed from type 302 stainless steel. The flat plate is 19.0mm thick and -.0.58m wide. with an Overall

  9. D.NET case study

    International Development Research Centre (IDRC) Digital Library (Canada)

    lremy

    developing products, marketing tools and building capacity of the grass root telecentre workers. D.Net recognized that it had several ideas worth developing into small interventions that would make big differences, but resource constraints were a barrier for scaling-up these initiatives. More demands, limited resources.

  10. Surgery for GEP-NETs

    DEFF Research Database (Denmark)

    Knigge, Ulrich; Hansen, Carsten Palnæs

    2012-01-01

    Surgery is the only treatment that may cure the patient with gastroentero-pancreatic (GEP) neuroendocrine tumours (NET) and neuroendocrine carcinomas (NEC) and should always be considered as first line treatment if R0/R1 resection can be achieved. The surgical and interventional procedures for GEP...

  11. Net Neutrality in the Netherlands

    NARCIS (Netherlands)

    van Eijk, N.

    2014-01-01

    The Netherlands is among the first countries that have put specific net neutrality standards in place. The decision to implement specific regulation was influenced by at least three factors. The first was the prevailing social and academic debate, partly due to developments in the United States. The

  12. Complexity Metrics for Workflow Nets

    DEFF Research Database (Denmark)

    Lassen, Kristian Bisgaard; van der Aalst, Wil M.P.

    2009-01-01

    Process modeling languages such as EPCs, BPMN, flow charts, UML activity diagrams, Petri nets, etc.\\ are used to model business processes and to configure process-aware information systems. It is known that users have problems understanding these diagrams. In fact, even process engineers and system...

  13. A framework for quantifying net benefits of alternative prognostic models

    DEFF Research Database (Denmark)

    Rapsomaniki, Eleni; White, Ian R; Wood, Angela M

    2012-01-01

    New prognostic models are traditionally evaluated using measures of discrimination and risk reclassification, but these do not take full account of the clinical and health economic context. We propose a framework for comparing prognostic models by quantifying the public health impact (net benefit......) of the treatment decisions they support, assuming a set of predetermined clinical treatment guidelines. The change in net benefit is more clinically interpretable than changes in traditional measures and can be used in full health economic evaluations of prognostic models used for screening and allocating risk...... reduction interventions. We extend previous work in this area by quantifying net benefits in life years, thus linking prognostic performance to health economic measures; by taking full account of the occurrence of events over time; and by considering estimation and cross-validation in a multiple...

  14. Modelling of Structural Loads in Drag Augmented Space Debris Removal Concepts

    DEFF Research Database (Denmark)

    Kristensen, Anders Schmidt; Nikolajsen, Jan Ánike; Lauridsen, Peter Riddersholm

    2017-01-01

    A Self-deployable Deorbiting Space Structure (SDSS) is used for drag augmented space debris removal. A highly flexible frame allows for a folding of the structure by bifurcation. This research models the structural loads during the deployment and unfolding of the drag sail in Low Earth Orbit (LEO...

  15. 76 FR 52263 - Special Local Regulation for Marine Events; Mattaponi Madness Drag Boat Race, Mattaponi River...

    Science.gov (United States)

    2011-08-22

    ... Madness Drag Boat Race, Mattaponi River, Wakema, VA AGENCY: Coast Guard, DHS. ACTION: Temporary Final rule. SUMMARY: The Coast Guard will establish special local regulations during the Mattaponi Madness Drag ] Boat Event, a series of power boat races to be held on the waters of the Mattaponi River, near Wakema...

  16. Factors affecting dustcake drag in a hot-gas filter system collecting coal gasification ash

    Energy Technology Data Exchange (ETDEWEB)

    Dahlin, R.S.; Landham, E.C. [Power Systems Development Facility, Wilsonville, AL (United States)

    2008-01-15

    This paper discusses the use of laboratory drag measurements and filter operating data to analyze factors affecting dustcake flow resistance in a hot-gas filter at the Power Systems Development Facility (PSDF). The hot-gas filter is a Siemens-Westinghouse two-tier candle filter system that is collecting coal gasification ash from a KBR Transport Gasifier. Operating experience with this system has shown that the flow resistance of the dustcake is responsible for most of the pressure drop across the hot-gas filter, and the pressure drop varies substantially with the type of coal being gasified and the operating conditions of the gasifier and filter systems. To analyze factors affecting dustcake drag, samples of gasification ash from various coals and various operating conditions were resuspended in a laboratory test apparatus, and the drag was measured as the dust was collected on a sintered metal filter. The lab-measured drag values were compared to actual values of transient drag determined from the increase in pressure drop, the inlet dust loading, and the face velocity in the hot-gas filter. After correcting the lab drag data to hot-gas filter conditions, good agreement was achieved between the lab measurements and the hot-gas filter transient drag values. Both types of measurements showed that drag was strongly influenced by coal type and carbon content.

  17. Stratified flow over complex topography: A model study of the bottom drag and associated mixing

    Science.gov (United States)

    Seim, Knut S.; Fer, Ilker; Avlesen, Helge

    2012-02-01

    The flow of stratified fluid over complex topography may lead to a significant drag on the fluid, exerted by the bottom obstacles. Using a 2-m resolution, three-dimensional, non-hydrostatic numerical ocean model, the drag and associated mixing on a stratified flow over real, 1-m resolution topography (interpolated to model resolution) is studied. With a typical mountain height of 12 m in 174 m water and buoyancy frequencies ranging from 0.6×10-2s-1 to 1.2×10-2s-1, resolving the topographic features leads to extensive drag exerted on the flow manifested through three different processes: (i) gravity wave drag, (ii) aerodynamic or blocked flow drag, and (iii) hydraulic drag. A parameterization of the internal wave drag based on linear, two-dimensional, hydrostatic wave solutions provides satisfactory results in terms of the turbulent kinetic energy levels. The depth of the layer where the vertical momentum flux is deposited, however, is underestimated, leading to an overestimated gravity wave drag in the layer.

  18. Electron and phonon drag in thermoelectric transport through coherent molecular conductors

    DEFF Research Database (Denmark)

    Lü, Jing-Tao; Wang, Jian-Sheng; Hedegård, Per

    2016-01-01

    there are at least two phonon degrees of freedom. After deriving expressions for the linear drag coefficients, obeying the Onsager relation, we further investigate their effect on nonequilibrium transport. We show that the drag effect is closely related to two other phenomena: (1) adiabatic charge pumping through...

  19. Aerodynamic drag of transiting objects by large-scale tomographic-PIV

    NARCIS (Netherlands)

    Terra, W.; Sciacchitano, A.; Scarano, F.

    Experiments are conducted that obtain the aerodynamic drag of a sphere towed within a rectangular duct from PIV. The drag force is obtained invoking the time-average momentum equation within a control volume in a frame of reference moving with the object. The sphere with 0.1 m diameter is towed at

  20. Coulomb Drag as a Probe of Coupled Plasmon Modes in Parallel Quantum Wells

    DEFF Research Database (Denmark)

    Flensberg, Karsten; Hu, Ben Yu-Kuang

    1994-01-01

    parameters. The acoustic mode causes a sharp upturn in the scaled drag rate with increasing temperature at T≈0.2TF. Other experimental signatures of the plasmon-dominated drag rate are a d-3 dependence on the well separation d and a peak as a function of relative densities at matched Fermi velocities....

  1. Experimental Study of Drag Resistance using a Laboratory Scale Rotary Set-Up

    DEFF Research Database (Denmark)

    Erik Weinell, Claus; Olsen, Kenneth N.; Christoffersen, Martin W.

    2003-01-01

    This work covers an experimental study of the drag resistance of different painted surfaces and simulated large-scale irregularities, viz. dry spraying, weld seams, barnacle fouling and paint remains. A laboratory scale rotary set-up was used to determine the drag resistance, and the surface...

  2. Lateral-drag Casimir forces induced by anisotropy

    CERN Document Server

    Nefedov, Igor S

    2016-01-01

    We predict the existence of lateral drag forces near the flat surface of an absorbing slab of an anisotropic material. The forces originate from the fluctuations of the electromagnetic field, when the anisotropy axis of the material forms a certain angle with the surface. In this situation, the spatial spectra of the fluctuating electromagnetic fields becomes asymmetric, different for positive and negative transverse wave vectors components. Differently from the case of van der Waals interactions in which the forward-backward symmetry is broken due to the particle movement or in quantum noncontact friction where it is caused by the mutual motion of the bodies, in our case the lateral motion results merely from the anisotropy of the slab. This new effect, of particular significance in hyperbolic materials, could be used for the manipulation of nanoparticles.

  3. Thermal design of AOTV heatshields for a conical drag brake

    Science.gov (United States)

    Pitts, W. C.; Murbach, M. S.

    1985-01-01

    Results are presented from an on-going study of the thermal performance of thermal protection systems for a conical drag brake type AOTV. Three types of heatshield are considered: rigid ceramic insulation, flexible ceramic blankets, and ceramic cloths. The results for the rigid insulation apply to other types of AOTV as well. Charts are presented in parametric form so that they may be applied to a variety of missions and vehicle configurations. The parameters considered include: braking maneuver heat flux and total heat load, heatshield material and thickness, heatshield thermal mass and conductivity, absorptivity and emissivity of surfaces, thermal mass of support structure, and radiation transmission through thin heatshields. Results of temperature calculations presented show trends with and sensitivities to these parameters. The emphasis is on providing information that will be useful in estimating the minimum required mass of these heatshield materials.

  4. Thermal design of AOTV heatshields for a conical drag brake

    Science.gov (United States)

    Pitts, W. C.; Murbach, M. S.

    1985-06-01

    Results are presented from an on-going study of the thermal performance of thermal protection systems for a conical drag brake type AOTV. Three types of heatshield are considered: rigid ceramic insulation, flexible ceramic blankets, and ceramic cloths. The results for the rigid insulation apply to other types of AOTV as well. Charts are presented in parametric form so that they may be applied to a variety of missions and vehicle configurations. The parameters considered include: braking maneuver heat flux and total heat load, heatshield material and thickness, heatshield thermal mass and conductivity, absorptivity and emissivity of surfaces, thermal mass of support structure, and radiation transmission through thin heatshields. Results of temperature calculations presented show trends with and sensitivities to these parameters. The emphasis is on providing information that will be useful in estimating the minimum required mass of these heatshield materials.

  5. Position sensors for LISA drag-free control

    CERN Document Server

    Weber, W J; Dolesi, R; Fontana, G; Hüller, M; Vitale, S

    2002-01-01

    The extreme level of isolation from stray forces required for LISA makes the development of 'drag-free control' technologies essential to the mission. We report here on the progress in the development of a capacitive, six degree-of-freedom, position sensor designed to meet the required low levels of position read-out noise (1 nm Hz sup - sup 1 sup / sup 2) and stray force noise (3x10 sup - sup 1 sup 5 N Hz sup - sup 1 sup / sup 2) across the LISA bandwidth of 0.1 mHz to 0.1 Hz. In this paper we briefly discuss sensor design and expected performance before presenting preliminary noise measurements made with a prototype sensor.

  6. Intertial Frame Dragging in an Acoustic Analogue spacetime

    CERN Document Server

    Chakraborty, Chandrachur; Majumdar, Parthasarathi

    2015-01-01

    We report an incipient exploration of the Lense-Thirring precession effect in a rotating {\\it acoustic analogue black hole} spacetime. An exact formula is deduced for the precession frequency of a gyroscope due to inertial frame dragging, close to the ergosphere of a `Draining Bathtub' acoustic spacetime which has been studied extensively for acoustic Hawking radiation of phonons and also for `superresonance'. The formula is verified by embedding the two dimensional spatial (acoustic) geometry into a three dimensional one where the similarity with standard Lense-Thirring precession results within a strong gravity framework is well known. Prospects of experimental detection of this new `fixed-metric' effect in acoustic geometries, are briefly discussed.

  7. Ontogeny of lift and drag production in ground birds.

    Science.gov (United States)

    Heers, Ashley M; Tobalske, Bret W; Dial, Kenneth P

    2011-03-01

    The juvenile period is often a crucial interval for selective pressure on locomotor ability. Although flight is central to avian biology, little is known about factors that limit flight performance during development. To improve understanding of flight ontogeny, we used a propeller (revolving wing) model to test how wing shape and feather structure influence aerodynamic performance during development in the precocial chukar partridge (Alectoris chukar, 4 to >100 days post hatching). We spun wings in mid-downstroke posture and measured lift (L) and drag (D) using a force plate upon which the propeller assembly was mounted. Our findings demonstrate a clear relationship between feather morphology and aerodynamic performance. Independent of size and velocity, older wings with stiffer and more asymmetrical feathers, high numbers of barbicels and a high degree of overlap between barbules generate greater L and L:D ratios than younger wings with flexible, relatively symmetrical and less cohesive feathers. The gradual transition from immature feathers and drag-based performance to more mature feathers and lift-based performance appears to coincide with ontogenetic transitions in locomotor capacity. Younger birds engage in behaviors that require little aerodynamic force and that allow D to contribute to weight support, whereas older birds may expand their behavioral repertoire by flapping with higher tip velocities and generating greater L. Incipient wings are, therefore, uniquely but immediately functional and provide flight-incapable juveniles with access to three-dimensional environments and refugia. Such access may have conferred selective advantages to theropods with protowings during the evolution of avian flight.

  8. Capture of Planetesimals by Gas Drag from Circumplanetary Disks

    Science.gov (United States)

    Fujita, Tetsuya; Ohtsuki, K.; Tanigawa, T.

    2012-10-01

    The regular satellites of the giant planets (e.g. Galilean satellites) have nearly circular and coplanar prograde orbits, and are thought to have formed by accretion of solid particles in the circumplanetary disk. Because a significant amount of gas and solids are likely to be supplied to growing giant planets through the circumplanetary disk, the amount of solid material in circumplanetary disks is important not only for satellite formation but also for the growth and the origin of the heavy element content of giant planets. Solid particles smaller than meter-scale are strongly coupled with the gas flow from the protoplanetary disk and delivered into the disk with the gas. On the other hand, trajectories of large planetesimals are decoupled from the gas. When these large planetesimals approach a growing giant planet, their orbits can be perturbed by gas drag from the circumplanetary disk depending on their size and random velocity, and some of them would be captured by the disk. In the present work, we examine orbital evolution of planetesimals approaching a growing giant planet with a circumplanetary disks by integrating Hill’s equation including the gas drag term. We assume that the gas in the disk rotates in circular orbits around the planet. We found that the condition for capture of planetesimals approaching in the prograde direction (i.e., trajectory in the same direction as the circular motion of the gas) is different from that for those approaching in the retrograde trajectories. We obtained analytic expressions for energy dissipation, critical approach distance from the planet for capture, and capture probability for prograde and retrograde orbits in the coplanar case. We will discuss results of orbital integration for capture rates, including the cases of inclined orbits of planetesimals.

  9. Caught in the Net: Perineuronal Nets and Addiction

    Directory of Open Access Journals (Sweden)

    Megan Slaker

    2016-01-01

    Full Text Available Exposure to drugs of abuse induces plasticity in the brain and creates persistent drug-related memories. These changes in plasticity and persistent drug memories are believed to produce aberrant motivation and reinforcement contributing to addiction. Most studies have explored the effect drugs of abuse have on pre- and postsynaptic cells and astrocytes; however, more recently, attention has shifted to explore the effect these drugs have on the extracellular matrix (ECM. Within the ECM are unique structures arranged in a net-like manner, surrounding a subset of neurons called perineuronal nets (PNNs. This review focuses on drug-induced changes in PNNs, the molecules that regulate PNNs, and the expression of PNNs within brain circuitry mediating motivation, reward, and reinforcement as it pertains to addiction.

  10. Oseen's correction to stokes drag on axially symmetric arbitrary particle in transverse flow: A new approach

    Directory of Open Access Journals (Sweden)

    Srivastava Deepak Kumar

    2014-01-01

    Full Text Available In this paper, Oseen’s correction to Stokes drag experienced by axially symmetric particle placed in a uniform stream perpendicular to axis of symmetry(i.e. transverse flow is obtained. For this, the linear relationship between axial and transverse Stokes drag is utilized to extend the Brenner’s formula for axial flow to transverse flow. General expression of Oseen’s correction to Stokes drag on axially symmetric particle placed in transverse flow is found to be new. This general expression is applied to some known axially symmetric bodies and obtained values of Oseen’s drag, up to first order terms in Reynolds number ‘R’, are also claimed to be new and never exist in the literature. Numerical values of Oseen drag are also evaluated and their variations with respect to Reynolds number, eccentricity and deformation parameter are depicted in figures and compared with some known values. Some important applications are also highlighted.

  11. Importance of Variable Density and Non-Boussinesq Effects on the Drag of Spherical Particles

    Science.gov (United States)

    Ganguli, Swetava; Lele, Sanjiva

    2017-11-01

    What are the forces that act on a particle as it moves in a fluid? How do they change in the presence of significant heat transfer from the particle, a variable density fluid or gravity? Last year, using particle-resolved simulations we quantified these effects on a single spherical particle and on particles in periodic lattices when O(10-3) 50%) in the absolute drag are observed as λ approaches unity. Oppenheimer, et al. (2016) [1] have proposed a theoretical formula for the drag of a heated sphere at extremely low Re. We show that when Re >O(10), inertial effects completely dominate the drag while when Re zero volumetric dilation rate. In the limit of λ approaching 0 (Stokes' limit), the drag modification can also be captured as a correction to Stokes' drag using a suitable scaling based on the dilation rate. Stanford University - Predictive Science Academic Alliance Program (PSSAP II).

  12. Supervisor control strategy of synchronizer for wet DCT based on online estimation of clutch drag torque

    Science.gov (United States)

    Lu, Tongli; Li, Hongkui; Zhang, Jianwu; Hao, Hongtao

    2016-01-01

    The objective of this paper is to improve the performance of the synchronizer control strategy by considering the effect of clutch drag torque. The research of synchronization process in wet dual clutch transmission is performed in this paper. The significant effect of clutch drag torque is analyzed by adding a complex clutch drag torque module to synchronizer model. This paper focuses on the development of original estimation method of clutch drag torque. The estimation method offers an effective way to obtain accurate clutch drag torque, and it is applied to develop a new supervisor control strategy. Results have demonstrated that the estimation method has satisfied efficiency and accuracy and the control strategy improves the performance of the synchronizer mechanism significantly.

  13. Remarks about the apparent increasing of the drag coefficient on flexible submarine cables

    Energy Technology Data Exchange (ETDEWEB)

    Marichal, D. [Ecole Centrale de Nantes, 44 (France)

    2004-07-01

    A lot of elongated flexible underwater structures (towing and mooring cables, trawl lines, oil risers...) are used in exploitation of sea resources. All theoretical calculations require to know the hydrodynamic forces acting on these structures (especially the drag coefficient). It was usually assumed that the drag coefficient of a cylindrical element is a constant and takes the value of 1.2 as a rigid cylinder at the typical Reynolds numbers. But, if the cylindrical structure has transverse vibrations - as it is usual for submarine cables -, an important increase of the drag coefficient seems to appear Our purpose is to show that the first explanation of the drag coefficient increase comes partly from the problem formulation. It is usual to think that the towing speed is very important compared with the transverse motion velocity. But, in fact, the drag results in the combination of the normal component of the flow and this transverse motion velocity. (author)

  14. Influence of hydrodynamic stress on the frictional drag of biofouling communities.

    Science.gov (United States)

    Hunsucker, J Travis; Hunsucker, Kelli Z; Gardner, Harrison; Swain, Geoffrey

    2016-11-01

    The role of hydrodynamic wall shear stresses on the development of the fouling community structure and resulting frictional drag were examined using a commercially available fouling release coating. Immersed test panels were exposed to three different hydrodynamic treatments, one static and two dynamic (corresponding to an estimated wall shear stress of 7.0  and 25.5 Pa). The drag of the panels was measured in a hydrodynamic test chamber at discrete time intervals over 35 days. The fouling community composition on the static panels was significantly different from the organisms observed on the dynamic panels. Despite different fouling community composition, the drag forces measured on the panels were very similar. This suggests that the frictional drag of low form and soft fouling communities are similar and that there may be a stepwise increase in frictional drag associated with the presence of mature calcareous organisms.

  15. Army Net Zero Prove Out. Net Zero Waste Best Practices

    Science.gov (United States)

    2014-11-20

    Anaerobic Digesters – Although anaerobic digestion is not a new technology and has been used on a large-scale basis in wastewater treatment , the...technology and has been used on a large-scale basis in wastewater treatment , the use of the technology should be demonstrated with other...approaches can be used for cardboard and cellulose -based packaging materials. This approach is in line with the Net Zero Waste hierarchy in terms of

  16. Drag Effect of Kompsat-1 During Strong Solar and Geomagnetic Activity

    Directory of Open Access Journals (Sweden)

    J. Park

    2007-06-01

    Full Text Available In this paper, we analyze the orbital variation of the KOrea Multi-Purpose SATellite-1(KOMPSAT-1 in a strong space environment due to satellite drag by solar and geomagnetic activities. The satellite drag usually occurs slowly, but becomes serious satellite drag when the space environment suddenly changes via strong solar activity like a big flare eruption or coronal mass ejections(CMEs. Especially, KOMPSAT-1 as a low earth orbit satellite has a distinct increase of the drag acceleration by the variations of atmospheric friction. We consider factors of solar activity to have serious effects on the satellite drag from two points of view. One is an effect of high energy radiation when the flare occurs in the Sun. This radiation heats and expands the upper atmosphere of the Earth as the number of neutral particles is suddenly increased. The other is an effect of Joule and precipitating particle heating caused by current of plasma and precipitation of particles during geomagnetic storms by CMEs. It also affects the density of neutral particles by heating the upper atmosphere. We investigate the satellite drag acceleration associated with the two factors for five events selected based on solar and geomagnetic data from 2001 to 2002. The major results can be summarized as follows. First, the drag acceleration started to increase with solar EUV radiation with the best cross-correlation (r = 0.92 for 1 day delayed F10.7. Second, the drag acceleration and Dst index have similar patterns when the geomagnetic storm is dominant and the drag acceleration abruptly increases during the strong geomagnetic storm. Third, the background variation of the drag accelerations is governed by the solar radiation, while their short term (less than a day variations is governed by geomagnetic storms.

  17. SpectralNET – an application for spectral graph analysis and visualization

    Directory of Open Access Journals (Sweden)

    Schreiber Stuart L

    2005-10-01

    Full Text Available Abstract Background Graph theory provides a computational framework for modeling a variety of datasets including those emerging from genomics, proteomics, and chemical genetics. Networks of genes, proteins, small molecules, or other objects of study can be represented as graphs of nodes (vertices and interactions (edges that can carry different weights. SpectralNET is a flexible application for analyzing and visualizing these biological and chemical networks. Results Available both as a standalone .NET executable and as an ASP.NET web application, SpectralNET was designed specifically with the analysis of graph-theoretic metrics in mind, a computational task not easily accessible using currently available applications. Users can choose either to upload a network for analysis using a variety of input formats, or to have SpectralNET generate an idealized random network for comparison to a real-world dataset. Whichever graph-generation method is used, SpectralNET displays detailed information about each connected component of the graph, including graphs of degree distribution, clustering coefficient by degree, and average distance by degree. In addition, extensive information about the selected vertex is shown, including degree, clustering coefficient, various distance metrics, and the corresponding components of the adjacency, Laplacian, and normalized Laplacian eigenvectors. SpectralNET also displays several graph visualizations, including a linear dimensionality reduction for uploaded datasets (Principal Components Analysis and a non-linear dimensionality reduction that provides an elegant view of global graph structure (Laplacian eigenvectors. Conclusion SpectralNET provides an easily accessible means of analyzing graph-theoretic metrics for data modeling and dimensionality reduction. SpectralNET is publicly available as both a .NET application and an ASP.NET web application from http://chembank.broad.harvard.edu/resources/. Source code is

  18. SpectralNET--an application for spectral graph analysis and visualization.

    Science.gov (United States)

    Forman, Joshua J; Clemons, Paul A; Schreiber, Stuart L; Haggarty, Stephen J

    2005-10-19

    Graph theory provides a computational framework for modeling a variety of datasets including those emerging from genomics, proteomics, and chemical genetics. Networks of genes, proteins, small molecules, or other objects of study can be represented as graphs of nodes (vertices) and interactions (edges) that can carry different weights. SpectralNET is a flexible application for analyzing and visualizing these biological and chemical networks. Available both as a standalone .NET executable and as an ASP.NET web application, SpectralNET was designed specifically with the analysis of graph-theoretic metrics in mind, a computational task not easily accessible using currently available applications. Users can choose either to upload a network for analysis using a variety of input formats, or to have SpectralNET generate an idealized random network for comparison to a real-world dataset. Whichever graph-generation method is used, SpectralNET displays detailed information about each connected component of the graph, including graphs of degree distribution, clustering coefficient by degree, and average distance by degree. In addition, extensive information about the selected vertex is shown, including degree, clustering coefficient, various distance metrics, and the corresponding components of the adjacency, Laplacian, and normalized Laplacian eigenvectors. SpectralNET also displays several graph visualizations, including a linear dimensionality reduction for uploaded datasets (Principal Components Analysis) and a non-linear dimensionality reduction that provides an elegant view of global graph structure (Laplacian eigenvectors). SpectralNET provides an easily accessible means of analyzing graph-theoretic metrics for data modeling and dimensionality reduction. SpectralNET is publicly available as both a .NET application and an ASP.NET web application from http://chembank.broad.harvard.edu/resources/. Source code is available upon request.

  19. The Role of Anode Manufacturing Processes in Net Carbon Consumption

    Directory of Open Access Journals (Sweden)

    Khalil Khaji

    2016-05-01

    Full Text Available Carbon anodes are consumed in electrolysis cells during aluminum production. Carbon consumption in pre-bake anode cells is 400–450 kg C/t Al, considerably higher than the theoretical consumption of 334 kg C/t Al. This excess carbon consumption is partly due to the anode manufacturing processes. Net carbon consumption over the last three years at Emirates Aluminium (EMAL, also known as Emirates Global Aluminium (EGA Al Taweelah was analyzed with respect to anode manufacturing processes/parameters. The analysis indicates a relationship between net carbon consumption and many manufacturing processes, including anode desulfurization during anode baking. Anode desulfurization appears to increase the reaction surface area, thereby helping the Boudouard reaction between carbon and carbon dioxide in the electrolysis zone, as well as reducing the presence of sulfur which could inhibit this reaction. This paper presents correlations noted between anode manufacturing parameters and baked anode properties, and their impact on the net carbon consumption in electrolytic pots. Anode reactivities affect the carbon consumption in the pots during the electrolysis of alumina. Pitch content in anodes, impurities in anodes, and anode desulfurization during baking were studied to find their influence on anode reactivities. The understanding gained through this analysis helped reduce net carbon consumption by adjusting manufacturing processes. For an aluminum smelter producing one million tonnes of aluminum per year, the annual savings could be as much as US $0.45 million for every kg reduction in net carbon consumption.

  20. HANPP Collection: Human Appropriation of Net Primary Productivity as a Percentage of Net Primary Productivity

    Data.gov (United States)

    National Aeronautics and Space Administration — The Human Appropriation of Net Primary Productivity (HANPP) as a Percentage of Net Primary Productivity (NPP) portion of the Human Appropriation of Net Primary...