aerodynamics and heat transfer
Directory of Open Access Journals (Sweden)
J. N. Rajadas
1998-01-01
Full Text Available A multidisciplinary optimization procedure, with the integration of aerodynamic and heat transfer criteria, has been developed for the design of gas turbine blades. Two different optimization formulations have been used. In the first formulation, the maximum temperature in the blade section is chosen as the objective function to be minimized. An upper bound constraint is imposed on the blade average temperature and a lower bound constraint is imposed on the blade tangential force coefficient. In the second formulation, the blade average and maximum temperatures are chosen as objective functions. In both formulations, bounds are imposed on the velocity gradients at several points along the surface of the airfoil to eliminate leading edge velocity spikes which deteriorate aerodynamic performance. Shape optimization is performed using the blade external and coolant path geometric parameters as design variables. Aerodynamic analysis is performed using a panel code. Heat transfer analysis is performed using the finite element method. A gradient based procedure in conjunction with an approximate analysis technique is used for optimization. The results obtained using both optimization techniques are compared with a reference geometry. Both techniques yield significant improvements with the multiobjective formulation resulting in slightly superior design.
THERMAL STRESS IN METEOROIDS BY AERODYNAMIC HEATING
Institute of Scientific and Technical Information of China (English)
Chi-Yu King
2003-01-01
Thermal stress in meteoroids by aerodynamic heating is calculated for the ideal case of an isotropic,homogeneous,elastic sphere being heated at the surface with a constant heattransfer coefficient. Given enough time, the tensile stress in the interior of the meteoroid can be as high as 10 kb. This stress value is greater than estimated tensile strengths of meteoroids and the aerodynamic compression they encounter. Significant thermal stress(1 kb) can develop quickly within a few tens of seconds) in a small(radius＜10 cm) stony meteoroid and a somewhat large radius＜l m)metallic meteoroid,and thus may cause tensile fracture to initiate in the meteotoid's interior. Fracture by thermal stress may have contributed to such observations as the existence of dust particles in upper atmosphere,the breakup of meteoroids at relatively low altitudes, the angular shape of meteorites and their wide scattering in a strewn field,and the explosive features of impact craters. In large meteoroids that require longer heating for thermal stress to fully develop,its effect is probably insignificant. The calculated stress values may be upper limits for real meteoroids which suffer melting and ablation at the surface.
THERMAL STRESS IN METEOROIDS BY AERODYNAMIC HEATING
Institute of Scientific and Technical Information of China (English)
Chi-YuKing
2003-01-01
Thermal stress in meteoroids by aerodynamic heating is calculated for the ideal case of an isotropic,homogeneous,elastic sphere being heated at the surface with a constant heattransfer coefficient. Given enough time,the tensile stress in the interior of the meteoroid can be as high as 10 kb. This stress value is greater than estimated tensile strengths of meteoroids and the aerodynamic compression they encounter. Significant thermal stress(1 kb) can develop quickly (within a few tens of seconds) in a small(radius＜10 cm) stony meteoroid and a somewhat large(radius＜l m)metallic meteoroid,and thus may cause tensile fracture to initiate in the meteotoid's interior. Fracture by thermal stress may have contributed to such observations as the existence of dust particles in upper atmosphere,the breakup of meteoroids at relatively low altitudes, the angular shape of meteorites and their wide scattering in a strewn field,and the explosive features of impact craters. In large meteoroids that require longer heating for thermal stress to fully develop, its effect is probably insignificant. The calculated stress values may be upper limits for real meteoroids which suffer melting and ablation at the surface.
Turbine stage aerodynamics and heat transfer prediction
Griffin, Lisa W.; Mcconnaughey, H. V.
1989-01-01
A numerical study of the aerodynamic and thermal environment associated with axial turbine stages is presented. Computations were performed using a modification of the unsteady NASA Ames viscous code, ROTOR1, and an improved version of the NASA Lewis steady inviscid cascade system MERIDL-TSONIC coupled with boundary layer codes BLAYER and STAN5. Two different turbine stages were analyzed: the first stage of the United Technologies Research Center Large Scale Rotating Rig (LSRR) and the first stage of the Space Shuttle Main Engine (SSME) high pressure fuel turbopump turbine. The time-averaged airfoil midspan pressure and heat transfer profiles were predicted for numerous thermal boundary conditions including adiabatic wall, prescribed surface temperature, and prescribed heat flux. Computed solutions are compared with each other and with experimental data in the case of the LSRR calculations. Modified ROTOR1 predictions of unsteady pressure envelopes and instantaneous contour plots are also presented for the SSME geometry. Relative merits of the two computational approaches are discussed.
Aerodynamic heating of ballistic missile including the effects of gravity
Indian Academy of Sciences (India)
S N Maitra
2000-10-01
The aerodynamic heating of a ballistic missile due to only convection is analysed taking into consideration the effects of gravity. The amount of heat transferred to the wetted area and to the nose region has been separately determined, unlike A Miele's treatise without consideration of gravity. The peak heating ratesto the wetted area and to the nose of the missile are also investigated. Finally four numerical examples are cited to estimate the errors, in heat transfers and heating ratesto both wetted area and nose region of the missile, arising out of neglecting the gravitational forces.
Aerodynamic Heating in Hypersonic Boundary Layers:\\ Role of Dilatational Waves
Zhu, Yiding; Wu, Jiezhi; Chen, Shiyi; Lee, Cunbiao; Gad-el-Hak, Mohamed
2016-01-01
The evolution of multi-mode instabilities in a hypersonic boundary layer and their effects on aerodynamic heating are investigated. Experiments are conducted in a Mach 6 wind tunnel using Rayleigh-scattering flow visualization, fast-response pressure sensors, fluorescent temperature-sensitive paint (TSP), and particle image velocimetry (PIV). Calculations are also performed based on both parabolized stability equations (PSE) and direct numerical simulations (DNS). It is found that second-mode dilatational waves, accompanied by high-frequency alternating fluid compression and expansion, produce intense aerodynamic heating in a small region that rapidly heats the fluid passing through it. As a result, the surface temperature rapidly increases and results in an overshoot over the nominal transitional value. When the dilatation waves decay downstream, the surface temperature decreases gradually until transition is completed. A theoretical analysis is provided to interpret the temperature distribution affected by ...
Numerical study on aerodynamic heat of hypersonic flight
Directory of Open Access Journals (Sweden)
Huang Haiming
2016-01-01
Full Text Available Accurate prediction of the shock wave has a significant effect on the development of space transportation vehicle or exploration missions. Taking Lobb sphere as the example, the aerodynamic heat of hypersonic flight in different Mach numbers is simulated by the finite volume method. Chemical reactions and non-equilibrium heat are taken into account in this paper, where convective flux of the space term adopts the Roe format, and discretization of the time term is achieved by backward Euler algorithm. The numerical results reveal that thick mesh can lead to accurate prediction, and the thickness of the shock wave decreases as grid number increases. Furthermore, most of kinetic energy converts into internal energy crossing the shock wave.
Advanced multistage turbine blade aerodynamics, performance, cooling, and heat transfer
Energy Technology Data Exchange (ETDEWEB)
Fleeter, S.; Lawless, P.B. [Purdue Univ., West Lafayette, IN (United States)
1995-10-01
The gas turbine has the potential for power production at the highest possible efficiency. The challenge is to ensure that gas turbines operate at the optimum efficiency so as to use the least fuel and produce minimum emissions. A key component to meeting this challenge is the turbine. Turbine performance, both aerodynamics and heat transfer, is one of the barrier advanced gas turbine development technologies. This is a result of the complex, highly three-dimensional and unsteady flow phenomena in the turbine. Improved turbine aerodynamic performance has been achieved with three-dimensional highly-loaded airfoil designs, accomplished utilizing Euler or Navier-Stokes Computational Fluid Dynamics (CFD) codes. These design codes consider steady flow through isolated blade rows. Thus they do not account for unsteady flow effects. However, unsteady flow effects have a significant impact on performance. Also, CFD codes predict the complete flow field. The experimental verification of these codes has traditionally been accomplished with point data - not corresponding plane field measurements. Thus, although advanced CFD predictions of the highly complex and three-dimensional turbine flow fields are available, corresponding data are not. To improve the design capability for high temperature turbines, a detailed understanding of the highly unsteady and three-dimensional flow through multi-stage turbines is necessary. Thus, unique data are required which quantify the unsteady three-dimensional flow through multi-stage turbine blade rows, including the effect of the film coolant flow. This requires experiments in appropriate research facilities in which complete flow field data, not only point measurements, are obtained and analyzed. Also, as design CFD codes do not account for unsteady flow effects, the next logical challenge and the current thrust in CFD code development is multiple-stage analyses that account for the interactions between neighboring blade rows.
Evaluating parameterizations of aerodynamic resistance to heat transfer using field measurements
Directory of Open Access Journals (Sweden)
Shaomin Liu
2007-01-01
Full Text Available Parameterizations of aerodynamic resistance to heat and water transfer have a significant impact on the accuracy of models of land – atmosphere interactions and of estimated surface fluxes using spectro-radiometric data collected from aircrafts and satellites. We have used measurements from an eddy correlation system to derive the aerodynamic resistance to heat transfer over a bare soil surface as well as over a maize canopy. Diurnal variations of aerodynamic resistance have been analyzed. The results showed that the diurnal variation of aerodynamic resistance during daytime (07:00 h–18:00 h was significant for both the bare soil surface and the maize canopy although the range of variation was limited. Based on the measurements made by the eddy correlation system, a comprehensive evaluation of eight popularly used parameterization schemes of aerodynamic resistance was carried out. The roughness length for heat transfer is a crucial parameter in the estimation of aerodynamic resistance to heat transfer and can neither be taken as a constant nor be neglected. Comparing with the measurements, the parameterizations by Choudhury et al. (1986, Viney (1991, Yang et al. (2001 and the modified forms of Verma et al. (1976 and Mahrt and Ek (1984 by inclusion of roughness length for heat transfer gave good agreements with the measurements, while the parameterizations by Hatfield et al. (1983 and Xie (1988 showed larger errors even though the roughness length for heat transfer has been taken into account.
Flow and Convective Heat Transfer of Cylinder Misaligned from Aerodynamic Axis of Cyclone Flow
Directory of Open Access Journals (Sweden)
I. L. Leukhin
2008-01-01
Full Text Available The paper provides and analyzes results of experimental investigations on physical specific features of hydrodynamics and convective heat transfer of a cyclone flow with a group of round cylinders located symmetrically relative to its aerodynamic axis, calculative equations for average and local heat transfer factors at characteristic sections of cylinder surface.
Institute of Scientific and Technical Information of China (English)
Jin-Ling Luo; Hong-Lin Kang; Jian Li; Wu-Ye Dai
2011-01-01
Numerical simulation methods of aerodynamic heating were compared by considering the influence of numerical schemes and turbulence models, and attempting to investigate the applicability of numerical simulation methods on predicting heat flux in engineering applications. For some typical cases provided with detailed experimental data, four spatial schemes and four turbulence models were adopted to calculate surface heat flux. By analyzing and comparing,some influencing regularities of numerical schemes and turbulence models on calculating heat flux had been acquired. It is clear that AUSM+-up scheme with rapid compressibilitymodified high Reynolds number k-ω model should be appropriate for calculating heat flux. The numerical methods selected as preference above were applied to calculate the heat flux of a 3-D complex geometry in high speed turbulent flows. The results indicated that numerical simulation can capture the complex flow phenomena and reveal the mechanism of aerodynamic heating. Especially, the numerical result of the heat flux at the stagnation point of the wedge was well in agreement with the prediction of Kemp-Riddel formula, and the surface heat flux distribution was consistent with experiment results, which implied that numerical simulation can be introduced to predict heat flux in engineering applications.
Aerodynamic levitation and laser heating: Applications at synchrotron and neutron sources
Energy Technology Data Exchange (ETDEWEB)
Hennet, L.; Pozdnyakova, I.; Drewitt, J.W.E.; Leydier, M.; Brassamin, S.; Zanghi, D.; Magazu, S.; Price, D.L. [CEMHTI and University of Orleans, 45071 Orleans Cedex 02 (France); Cristiglio, V.; Kozaily, J.; Fischer, H.E.; Cuello, G.J.; Koza, M. [ILL, BP. 156, 38042 Grenoble Cedex 09 (France); Bytchkov, A. [ESRF, BP. 220, 38043 Grenoble Cedex 09 (France); Thiaudiere, D. [Synchrotron SOLEIL, BP. 48, 91192 Gif-sur-Yvette Cedex (France); Gruner, S. [Institute of Physics, Chemnitz UT, 09107 Chemnitz (Germany); Greaves, G.N. [IMAPS, University of Wales, Aberystwyth, SY23 3BZ (United Kingdom)
2011-05-15
Aerodynamic levitation is an effective way to suspend samples which can be heated with CO{sub 2} lasers. The advantages of this container-less technique are the simplicity and compactness of the device, making it possible to integrate it easily in different kinds of experiments. In addition, all types of materials can be used, including metals and oxides. The integration of aerodynamic levitation at synchrotron and neutron sources provides powerful tools to study the structure and dynamics of molten materials. We present here an overview of the existing techniques (electromagnetic levitation, electrostatic levitation, single-axis acoustic levitation, and aerodynamic levitation) and of the developments made at the CEMHTI in Orleans, as well as a few examples of experimental results already obtained. (authors)
Advanced turbine cooling, heat transfer, and aerodynamic studies
Energy Technology Data Exchange (ETDEWEB)
Je-Chin Han; Schobeiri, M.T. [Texas A& M Univ., College Station, TX (United States)
1995-10-01
The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect on Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.
Directory of Open Access Journals (Sweden)
J. H. Lee
2012-11-01
Full Text Available Aerodynamic roughness height (Z_{om} is a key parameter required in several land surface hydrological models, since errors in heat flux estimation are largely dependent on optimization of this input. Despite its significance, it remains an uncertain parameter which is not readily determined. This is mostly because of non-linear relationship in Monin-Obukhov similarity (MOS equations and uncertainty of vertical characteristic of vegetation in a large scale. Previous studies often determined aerodynamic roughness using a minimization of cost function over MOS relationship or linear regression over it, traditional wind profile method, or remotely sensed vegetation index. However, these are complicated procedures that require a high accuracy for several other related parameters embedded in serveral equations including MOS. In order to simplify this procedure and reduce the number of parameters in need, this study suggests a new approach to extract aerodynamic roughness parameter from single or two heat flux measurements analyzed via Ensemble Kalman Filter (EnKF that affords non-linearity. So far, to our knowledge, no previous study has applied EnKF to aerodynamic roughness estimation, while the majority of data assimilation study have paid attention to updates of other land surface state variables such as soil moisture or land surface temperature. The approach of this study was applied to grassland in semi-arid Tibetan Plateau and maize on moderately wet condition in Italy. It was demonstrated that aerodynamic roughness parameter can be inversely tracked from heat flux EnKF final analysis. The aerodynamic roughness height estimated in this approach was consistent with eddy covariance method and literature value. Through a calibration of this parameter, this adjusted the sensible heat previously overestimated and latent heat flux previously underestimated by the original Surface Energy Balance System (SEBS model. It was considered that
Veraar, R.G.
2009-01-01
To enable direct experimental duplication of the inflight heat flux distribution on supersonic and hypersonic vehicles, an aerodynamic heating scaling technique has been developed. The scaling technique is based on the analytical equations for convective heat transfer for laminar and turbulent bound
Shape optimization of turbine blades with the integration of aerodynamics and heat transfer
Directory of Open Access Journals (Sweden)
Rajadas J. N.
1998-01-01
Full Text Available A multidisciplinary optimization procedure, with the integration of aerodynamic and heat transfer criteria, has been developed for the design of gas turbine blades. Two different optimization formulations have been used. In the first formulation, the maximum temperature in the blade section is chosen as the objective function to be minimized. An upper bound constraint is imposed on the blade average temperature and a lower bound constraint is imposed on the blade tangential force coefficient. In the second formulation, the blade average and maximum temperatures are chosen as objective functions. In both formulations, bounds are imposed on the velocity gradients at several points along the surface of the airfoil to eliminate leading edge velocity spikes which deteriorate aerodynamic performance. Shape optimization is performed using the blade external and coolant path geometric parameters as design variables. Aerodynamic analysis is performed using a panel code. Heat transfer analysis is performed using the finite element method. A gradient based procedure in conjunction with an approximate analysis technique is used for optimization. The results obtained using both optimization techniques are compared with a reference geometry. Both techniques yield significant improvements with the multiobjective formulation resulting in slightly superior design.
Comparison of Various Supersonic Turbine Tip Designs to Minimize Aerodynamic Loss and Tip Heating
Shyam, Vikram; Ameri, Ali
2012-01-01
The rotor tips of axial turbines experience high heat flux and are the cause of aerodynamic losses due to tip clearance flows, and in the case of supersonic tips, shocks. As stage loadings increase, the flow in the tip gap approaches and exceeds sonic conditions. This introduces effects such as shock-boundary layer interactions and choked flow that are not observed for subsonic tip flows that have been studied extensively in literature. This work simulates the tip clearance flow for a flat tip, a diverging tip gap and several contoured tips to assess the possibility of minimizing tip heat flux while maintaining a constant massflow from the pressure side to the suction side of the rotor, through the tip clearance. The Computational Fluid Dynamics (CFD) code GlennHT was used for the simulations. Due to the strong favorable pressure gradients the simulations assumed laminar conditions in the tip gap. The nominal tip gap width to height ratio for this study is 6.0. The Reynolds number of the flow is 2.4 x 10(exp 5) based on nominal tip width and exit velocity. A wavy wall design was found to reduce heat flux by 5 percent but suffered from an additional 6 percent in aerodynamic loss coefficient. Conventional tip recesses are found to perform far worse than a flat tip due to severe shock heating. Overall, the baseline flat tip was the second best performer. A diverging converging tip gap with a hole was found to be the best choice. Average tip heat flux was reduced by 37 percent and aerodynamic losses were cut by over 6 percent.
Modeling and Simulation of Radiative Compressible Flows in Aerodynamic Heating Arc-Jet Facility
Bensassi, Khalil; Laguna, Alejandro A.; Lani, Andrea; Mansour, Nagi N.
2016-01-01
Numerical simulations of an arc heated flow inside NASA's 20 [MW] Aerodynamics heating facility (AHF) are performed in order to investigate the three-dimensional swirling flow and the current distribution inside the wind tunnel. The plasma is considered in Local Thermodynamics Equilibrium(LTE) and is composed of Air-Argon gas mixture. The governing equations are the Navier-Stokes equations that include source terms corresponding to Joule heating and radiative cooling. The former is obtained by solving an electric potential equation, while the latter is calculated using an innovative massively parallel ray-tracing algorithm. The fully coupled system is closed by the thermodynamics relations and transport properties which are obtained from Chapman-Enskog method. A novel strategy was developed in order to enable the flow solver and the radiation calculation to be preformed independently and simultaneously using a different number of processors. Drastic reduction in the computational cost was achieved using this strategy. Details on the numerical methods used for space discretization, time integration and ray-tracing algorithm will be presented. The effect of the radiative cooling on the dynamics of the flow will be investigated. The complete set of equations were implemented within the COOLFluiD Framework. Fig. 1 shows the geometry of the Anode and part of the constrictor of the Aerodynamics heating facility (AHF). Fig. 2 shows the velocity field distribution along (x-y) plane and the streamline in (z-y) plane.
Prediction of the aerodynamic environment and heat transfer for rotor-stator configurations
Griffin, L. W.; McConnaughey, H. V.
1989-06-01
A numerical study of the aerodynamic and thermal environment associated with axial turbine stages is presented. Computations were performed using a modification of the unsteady viscous code, ROTORI, and an improved version of the steady inviscid cascade system, MERIDL-TSONIC, coupled with boundary layer codes, BLAYER and STAN5. Two different turbine stages were analyzed: the first stage of the United Technologies Research Center Large Scale Rotating Rig (LSRR) and the first stage of the Space Shuttle Main Engine (SSME) high pressure fuel turbopump turbine. The time-averaged airfoil midspan pressure and heat transfer profiles were predicted for numerous thermal boundary conditions including adiabatic wall, prescribed surface temperature, and prescribed heat flux. Computed solutions are compared with each other and with experimental data in the case of the LSRR calculations. Modified ROTORI predictions of unsteady pressure envelopes and instantaneous contour plots are also presented. Relative merits of the two computational approaches are discussed.
Convective heat transfer and experimental icing aerodynamics of wind turbine blades
Wang, Xin
The total worldwide base of installed wind energy peak capacity reached 94 GW by the end of 2007, including 1846 MW in Canada. Wind turbine systems are being installed throughout Canada and often in mountains and cold weather regions, due to their high wind energy potential. Harsh cold weather climates, involving turbulence, gusts, icing and lightning strikes in these regions, affect wind turbine performance. Ice accretion and irregular shedding during turbine operation lead to load imbalances, often causing the turbine to shut off. They create excessive turbine vibration and may change the natural frequency of blades as well as promote higher fatigue loads and increase the bending moment of blades. Icing also affects the tower structure by increasing stresses, due to increased loads from ice accretion. This can lead to structural failures, especially when coupled to strong wind loads. Icing also affects the reliability of anemometers, thereby leading to inaccurate wind speed measurements and resulting in resource estimation errors. Icing issues can directly impact personnel safety, due to falling and projected ice. It is therefore important to expand research on wind turbines operating in cold climate areas. This study presents an experimental investigation including three important fundamental aspects: (1) heat transfer characteristics of the airfoil with and without liquid water content (LWC) at varying angles of attack; (2) energy losses of wind energy while a wind turbine is operating under icing conditions; and (3) aerodynamic characteristics of an airfoil during a simulated icing event. A turbine scale model with curved 3-D blades and a DC generator is tested in a large refrigerated wind tunnel, where ice formation is simulated by spraying water droplets. A NACA 63421 airfoil is used to study the characteristics of aerodynamics and convective heat transfer. The current, voltage, rotation of the DC generator and temperature distribution along the airfoil
Hightower, T. Mark; MacDonald, Christine L.; Martinez, Edward R.; Balboni, John A.; Anderson, Karl F.; Arnold, Jim O. (Technical Monitor)
2002-01-01
The NASA Ames Research Center (ARC) Arc Jet Facilities' Aerodynamic Heating Facility (AHF) has been instrumented for the Enthalpy By Energy Balance (EB2) method. Diagnostic EB2 data is routinely taken for all AHF runs. This paper provides an overview of the EB2 method implemented in the AHF. The chief advantage of the AHF implementation over earlier versions is the non-intrusiveness of the instruments used. For example, to measure the change in cooling water temperature, thin film 1000 ohm Resistance Temperature Detectors (RTDs) are used with an Anderson Current Loop (ACL) as the signal conditioner. The ACL with 1000 ohm RTDs allows for very sensitive measurement of the increase in temperature (Delta T) of the cooling water to the arc heater, which is a critical element of the EB2 method. Cooling water flow rates are measured with non-intrusive ultrasonic flow meters.
International Nuclear Information System (INIS)
Different types of Large Carbon Cluster (LCC) layers are synthesized by a single-step pyrolysis technique at various ratios of precursor mixture. The aim is to develop a fast responsive and stable thermal gauge based on a LCC layer which has relatively good electrical conduction in order to use it in the hypersonic flow field. The thermoelectric property of the LCC layer has been studied. It is found that these carbon clusters are sensitive to temperature changes. Therefore suitable thermal gauges were developed for blunt cone bodies and were tested in hypersonic shock tunnels at a flow Mach number of 6.8 to measure aerodynamic heating. The LCC layer of this thermal gauge encounters high shear forces and a hostile environment for test duration in the range of a millisecond. The results are favorable to use large carbon clusters as a better sensor than a conventional platinum thin film gauge in view of fast responsiveness and stability. (paper)
Comparative study on aerodynamic heating under perfect and nonequilibrium hypersonic flows
Wang, Qiu; Li, JinPing; Zhao, Wei; Jiang, ZongLin
2016-02-01
In this study, comparative heat flux measurements for a sharp cone model were conducted by utilizing a high enthalpy shock tunnel JF-10 and a large-scale shock tunnel JF-12, responsible for providing nonequilibrium and perfect gas flows, respectively. Experiments were performed at the Key Laboratory of High Temperature Gas Dynamics (LHD), Institute of Mechanics, Chinese Academy of Sciences. Corresponding numerical simulations were also conducted in effort to better understand the phenomena accompanying in these experiments. By assessing the consistency and accuracy of all the data gathered during this study, a detailed comparison of sharp cone heat transfer under a totally different kind of freestream conditions was build and analyzed. One specific parameter, defined as the product of the Stanton number and the square root of the Reynold number, was found to be more characteristic for the aerodynamic heating phenomena encountered in hypersonic flight. Adequate use of said parameter practically eliminates the variability caused by the deferent flow conditions, regardless of whether the flow is in dissociation or the boundary condition is catalytic. Essentially, the parameter identified in this study reduces the amount of ground experimental data necessary and eases data extrapolation to flight.
Indian Academy of Sciences (India)
Niranjan Sahoo; S Saravanan; G Jagadeesh; K P J Reddy
2006-10-01
Aerodynamic forces and fore-body convective surface heat transfer rates over a 60° apex-angle blunt cone have been simultaneously measured at a nominal Mach number of 5·75 in the hypersonic shock tunnel HST2. An aluminum model incorporating a three-component accelerometer-based balance system for measuring the aerodynamic forces and an array of platinum thin-ﬁlm gauges deposited on thermally insulating backing material ﬂush mounted on the model surface is used for convective surface heat transfer measurement in the investigations. The measured value of the drag coefﬁcient varies by about $\\pm 6$% from the theoretically estimated value based on the modiﬁed Newtonian theory, while the axi-symmetric Navier–Stokes computations overpredict the drag coefﬁcient by about 9%. The normalized values of measured heat transfer rates at 0° angle of attack are about 11% higher than the theoretically estimated values. The aerodynamic and the heat transfer data presented here are very valuable for the validation of CFD codes used for the numerical computation of ﬂow ﬁelds around hypersonic vehicles.
Directory of Open Access Journals (Sweden)
M. T. Schobeiri
2000-01-01
Full Text Available Aerodynamic and heat transfer investigations were done on a constant curvature curved plate in a subsonic wind tunnel facility for various wake passing frequencies and zero pressure gradient conditions. Steady and unsteady boundary layer transition measurements were taken on the concave surface of the curved plate at different wake passing frequencies where a rotating squirrel-cage generated the unsteady wake flow. The data were analyzed using timeaveraged and ensemble-averaged techniques to provide insight into the growth of the boundary layer and transition. Ensemble-averaged turbulence intensity contours in the temporal spatial domain showed that transition was induced for increasing wake passing frequency and structure. The local heat transfer coefficient distribution for the concave and convex surface was determined at those wake passing frequencies using a liquid crystal heat transfer measurement technique. Detailed aerodynamic and heat transfer investigations showed that higher wake passing frequency caused transition to occur earlier on the concave surface. Local Stanton numbers were also calculated on the concave surface and compared with Stanton numbers predicted using a differential boundary layer and heat transfer calculation method. On the convex side, no effect of wake passing frequency on heat transfer was observed due to a separation bubble that induced transition.
Gumusel, Baris
Axial flow turbine stages are usually designed with a gap between the tips of the rotating blades and a stationary outer casing. The presence of a strong pressure gradient across this gap drives flow from the pressure side of the blade to the suction side. This leakage flow creates a significant amount of energy loss of working fluid in the turbine stage. In a modern gas turbine engine the outer casing of the high-pressure turbine is also exposed to a combination of high flow temperatures and heat transfer coefficients. The casing is consequently subjected to high levels of convective heat transfer, a situation that is aggravated by flow unsteadiness caused by periodic blade-passing events. An experimental investigation of the aerodynamic and heat transfer effect of tip and casing treatments used in turbine tip leakage control was conducted in a large scale, low speed, rotating research turbine facility. The effects of casing treatments were investigated by measuring the total pressure field at the exit of the rotor using a high frequency response total pressure probe. A smooth wall as a baseline case was also investigated. The test cases presented include results of casing treatments with varying dimensions for tip gap height of t/h=2.5%. The results of the rotor exit total pressure indicate that the casing treatment significantly reduced the leakage mass flow rate and the momentum deficit in the core of the tip vortex. The reductions obtained in the tip vortex size and strength influenced the tip-side passage vortex and other typical core flow characteristics in the passage. Casing treatments with the highest ridge height was the most effective in reducing the total pressure loss in the leakage flow of the test blades. This was observed at a radius near the core of the tip vortex. It appears that casing treatments with the highest ridge height is also the most effective from a global point of view, as shown by the passage averaged pressure coefficient obtained in
Directory of Open Access Journals (Sweden)
Wang Decheng
2015-01-01
Full Text Available The quartz lamp radiation aerodynamic heating simulation experiment system plays an important role on the structure strength heat experiment. In order to reduce its price and enhance flexibility on control law design of experiment system, a design method for low-cost quartz lamp radiation aerodynamic heating simulation experiment system with control law flexible adjustment feature is proposed. The hardware part is constructed by taking Digital Signal Processor (DSP as an implementing agency controller. The feedback temperature after processed is computed by DSP. But the experiment process control value is computed by computer. The feedback temperature and experiment process control value data are transferred by serial communication model between DSP and computer. The experiment process relation data is saved by computer with EXCEL file, including the given target spectrum, the feedback temperature and the control value. The results of experiments on system identification, PID spectrum tracking, different zone control and the open loop control show the effectiveness of the proposed method.
Avery, D. E.
1978-01-01
An experimental heat-transfer investigation was conducted on two staggered arrays of metallic tiles in laminar and turbulent boundary layers. This investigation was conducted for two purposes. The impingement heating distribution where flow in a longitudinal gap intersects a transverse gap and impinges on a downstream blocking tile was defined. The influence of tile and gap geometries was analyzed to develop empirical relationships for impingement heating in laminar and turbulent boundary layers. Tests were conducted in a high temperature structures tunnel at a nominal Mach number of 7, a nominal total temperature of 1800 K, and free-stream unit Reynolds numbers from 1.0 x 10 million to 4.8 x 10 million per meter. The test results were used to assess the impingement heating effects produced by parameters that include gap width, longitudinal gap length, slope of the tile forward-facing wall, boundary-layer displacement thickness, Reynolds number, and local surface pressure.
International Nuclear Information System (INIS)
Novel barium aluminate (BaAl2O4) and barium alumino-titanate (BaAl2TiO6) glasses have been produced by aerodynamic levitation and laser heating. BaAl2O4 forms a clear and colourless glass under containerless and rapid quenching conditions. Under similar rapid quenching conditions BaAl2TiO6 forms an opaque and black glass, while under slower and controlled quenching conditions it is possible to form a clear and colourless glass. The formation of the opaque or clear glass is reversible and purely dependent on the quench rate used. By slowing the quench rate further, it is possible to produce a milky glass suggestive of liquid-liquid phase separation in the liquid before glassification. High-energy x-ray diffraction experiments confirm the glassy state of these materials and show coordination structures and bond distances similar to their crystalline analogues. (letter to the editor)
Whitehead, Allen H., Jr.
1989-01-01
This paper discusses the critical aerodynamic technologies needed to support the development of a class of aircraft represented by the National Aero-Space Plane (NASP). The air-breathing, single-stage-to-orbit mission presents a severe challenge to all of the aeronautical disciplines and demands an extension of the state-of-the-art in each technology area. While the largest risk areas are probably advanced materials and the development of the scramjet engine, there remains a host of design issues and technology problems in aerodynamics, aerothermodynamics, and propulsion integration. The paper presents an overview of the most significant propulsion integration problems, and defines the most critical fluid flow phenomena that must be evaluated, defined, and predicted for the class of aircraft represented by the Aero-Space Plane.
Institute of Scientific and Technical Information of China (English)
张俊; 刘荣忠; 郭锐; 高天宇; 吴国夫
2015-01-01
末敏子弹在火药燃气推力作用下从母弹舱内抛出后，其表面红外辐射主要源于减速减旋运动产生的气动加热。针对此问题，应用 SIMULINK 建立了末敏子弹减速减旋弹道的仿真模型，求解并分析了弹道诸元的变化规律。以部分弹道数据和气流参数为来流条件，利用 FLUENT 对其气动热进行了数值模拟，分析了不同飞行条件下的表面瞬态温度、压力分布规律。结果表明：末敏子弹在减速减旋段的速度较低，表面温度梯度较小，红外辐射特征较弱；高温区集中在弹头附近、伞盘以及连接杆部位；驻点温度的仿真结果与工程计算结果吻合较好。研究结论可为末敏弹的红外侦察预警仿真技术提供帮助。%The surface infrared radiation(IR)of terminal-sensitive submunition(TSS)mainly comes from the aerodynamic heating after it is projected out of the carrier capsule under the gas thrust generated by gunpowder.Aiming at this problem,SIMULINK was used to build the trajectory simulation-model of TSS at deceleration and despinning stage,and the change laws of the ballistic data were solved and analyzed.Taking some specific ballistic data and airflow parameters as the inlet flow condition,FLUENT was used to simulate the aerodynamic heating and analyze the dis-tribution of the surface transient temperature and pressure.The results show that at the deceleration and despinning stage,the velocity of TSS is relatively lower,and the surface temperature gradient and IR characteristics are not obvious.The high temperature area is concentrated on the warhead,the umbrella plate and the connecting rod.The stagnation temperature obtained by numerical simulation reasonably agrees with the engineering calculation result.The results are useful to the infrared warning reconnaissance technology of terminal-sensitive projectile.
Scorer, R S
1958-01-01
Natural Aerodynamics focuses on the mathematics of any problem in air motion.This book discusses the general form of the law of fluid motion, relationship between pressure and wind, production of vortex filaments, and conduction of vorticity by viscosity. The flow at moderate Reynolds numbers, turbulence in a stably stratified fluid, natural exploitation of atmospheric thermals, and plumes in turbulent crosswinds are also elaborated. This text likewise considers the waves produced by thermals, transformation of thin layer clouds, method of small perturbations, and dangers of extra-polation.Thi
Energy Technology Data Exchange (ETDEWEB)
Schobeiri, Meinhard; Han, Je-Chin
2014-09-30
This report deals with the specific aerodynamics and heat transfer problematic inherent to high pressure (HP) turbine sections of IGCC-gas turbines. Issues of primary relevance to a turbine stage operating in an IGCC-environment are: (1) decreasing the strength of the secondary flow vortices at the hub and tip regions to reduce (a), the secondary flow losses and (b), the potential for end wall deposition, erosion and corrosion due to secondary flow driven migration of gas flow particles to the hub and tip regions, (2) providing a robust film cooling technology at the hub and that sustains high cooling effectiveness less sensitive to deposition, (3) investigating the impact of blade tip geometry on film cooling effectiveness. The document includes numerical and experimental investigations of above issues. The experimental investigations were performed in the three-stage multi-purpose turbine research facility at the Turbomachinery Performance and Flow Research Laboratory (TPFL), Texas A&M University. For the numerical investigations a commercial Navier-Stokes solver was utilized.
Advanced Topics in Aerodynamics
DEFF Research Database (Denmark)
Filippone, Antonino
1999-01-01
"Advanced Topics in Aerodynamics" is a comprehensive electronic guide to aerodynamics,computational fluid dynamics, aeronautics, aerospace propulsion systems, design and relatedtechnology. We report data, tables, graphics, sketches,examples, results, photos, technical andscientific literature, for...
Computation of dragonfly aerodynamics
Gustafson, Karl; Leben, Robert
1991-04-01
Dragonflies are seen to hover and dart, seemingly at will and in remarkably nimble fashion, with great bursts of speed and effectively discontinuous changes of direction. In their short lives, their gossamer flight provides us with glimpses of an aerodynamics of almost extraterrestrial quality. Here we present the first computer simulations of such aerodynamics.
Hunt, L. Roane; Notestine, Kristopher K.
1990-06-01
Surface and gap pressures and heating-rate distributions were obtained for simulated Thermal Protection System (TPS) tile arrays on the curved surface test apparatus of the Langley 8-Foot High Temperature Tunnel at Mach 6.6. The results indicated that the chine gap pressures varied inversely with gap width because larger gap widths allowed greater venting from the gap to the lower model side pressures. Lower gap pressures caused greater flow ingress from the surface and increased gap heating. Generally, gap heating was greater in the longitudinal gaps than in the circumferential gaps. Gap heating decreased with increasing gap depth. Circumferential gap heating at the mid-depth was generally less than about 10 percent of the external surface value. Gap heating was most severe at local T-gap junctions and tile-to-tile forward-facing steps that caused the greatest heating from flow impingement. The use of flow stoppers at discrete locations reduced heating from flow impingement. The use of flow stoppers at discrete locations reduced heating in most gaps but increased heating in others. Limited use of flow stoppers or gap filler in longitudinal gaps could reduce gap heating in open circumferential gaps in regions of high surface pressure gradients.
Heat-balance Thermal Protection with Heat Pipes for Hypersonic Vehicle
Rong Yisheng; Wei Yuechuan; Duan Dongli; Zhan Renjun
2016-01-01
Heat-balance thermal protection is non-ablating thermal protection for leading edge of hypersonic vehicle. Heat will be quickly transferred from high aerodynamic heating area to low aerodynamic heating area, where the energy will be released by radiation. The temperature of high aerodynamic heating area could be reduced to protect the designed structure from being burned down. Heat-balance thermal protection is summarized. The research on heat-pipe for heat-balance thermal protection is intro...
Aerodynamic investigations of ventilated brake discs.
Parish, D.; MacManus, David G.
2005-01-01
The heat dissipation and performance of a ventilated brake disc strongly depends on the aerodynamic characteristics of the flow through the rotor passages. The aim of this investigation was to provide an improved understanding of ventilated brake rotor flow phenomena, with a view to improving heat dissipation, as well as providing a measurement data set for validation of computational fluid dynamics methods. The flow fields at the exit of four different brake rotor geometrie...
Reinforced aerodynamic profile
DEFF Research Database (Denmark)
2010-01-01
The present invention relates to the prevention of deformations in an aerodynamic profile caused by lack of resistance to the bending moment forces that are created when such a profile is loaded in operation. More specifically, the invention relates to a reinforcing element inside an aerodynamic ...... profile and a method for the construction thereof. The profile is intended for, but not limited to, useas a wind turbine blade, an aerofoil device or as a wing profile used in the aeronautical industry....
Horstman, Raymond H.
1992-01-01
Aerodynamic flow achieved by adding fixed fairings to butterfly valve. When valve fully open, fairings align with butterfly and reduce wake. Butterfly free to turn, so valve can be closed, while fairings remain fixed. Design reduces turbulence in flow of air in internal suction system. Valve aids in development of improved porous-surface boundary-layer control system to reduce aerodynamic drag. Applications primarily aerospace. System adapted to boundary-layer control on high-speed land vehicles.
Institute of Scientific and Technical Information of China (English)
王荣; 张学军; 纪楚群
2015-01-01
结合空间推进数值模拟方法和流线追踪法发展了气动力、热快速预测技术。针对高速飞行器的算例研究表明，相对常规时间推进方法，基于空间推进法的气动快速预测方法计算效率提高了一个量级，而两者气动力计算精度相当，相对实验热流预测误差在20％以内。所发展的技术为适应气动外形快速选型和优化设计需求提供了有效的方法。%A fast aerodynamic characteristics prediction technique is developed to predict aer-odynamic force and heat,combining effective space marching numerical method with engineering method based on surface stream tracking technique.Hypersonic aerodynamic forces are obtained effectively by solving the Euler equations numerically with fast space marching method.In order to calculate the heat flux,an engineering method,called tracking the surface stream trace based on the axisymmetric analogue technique and boundary layer theory,is adopted and developed to be applicable for complex geometry.The inviscid flow parameters and surface stream lines re-quired in the engineering method are obtained from above mentioned inviscous numerical flow fields.The proposed method for aerodynamic force and heat prediction is applied to high speed vehicles,the results show that the space marching method saves the computational cost enor-mously,approximately one order less comparing to the time marching method,while the two methods have similar precision in aerodynamic force evaluation.The predicted error of heat flux is within 20% comparing to that of wind tunnel test.The technique promoted is an effective ap-proach suitable for the needs of fast aerodynamic configuration design and optimization.
Katz, Joseph
2006-01-01
Race car performance depends on elements such as the engine, tires, suspension, road, aerodynamics, and of course the driver. In recent years, however, vehicle aerodynamics gained increased attention, mainly due to the utilization of the negative lift (downforce) principle, yielding several important performance improvements. This review briefly explains the significance of the aerodynamic downforce and how it improves race car performance. After this short introduction various methods to generate downforce such as inverted wings, diffusers, and vortex generators are discussed. Due to the complex geometry of these vehicles, the aerodynamic interaction between the various body components is significant, resulting in vortex flows and lifting surface shapes unlike traditional airplane wings. Typical design tools such as wind tunnel testing, computational fluid dynamics, and track testing, and their relevance to race car development, are discussed as well. In spite of the tremendous progress of these design tools (due to better instrumentation, communication, and computational power), the fluid dynamic phenomenon is still highly nonlinear, and predicting the effect of a particular modification is not always trouble free. Several examples covering a wide range of vehicle shapes (e.g., from stock cars to open-wheel race cars) are presented to demonstrate this nonlinear nature of the flow field.
Aerodynamically shaped vortex generators
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver; Velte, Clara Marika; Øye, Stig;
2016-01-01
An aerodynamically shaped vortex generator has been proposed, manufactured and tested in a wind tunnel. The effect on the overall performance when applied on a thick airfoil is an increased lift to drag ratio compared with standard vortex generators. Copyright © 2015 John Wiley & Sons, Ltd....
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver
Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its second edition, it has been entirely updated and substantially extended to reflect advances in technology, research into rotor aerodynamics and the structural...... response of the wind turbine structure. Topics covered include increasing mass flow through the turbine, performance at low and high wind speeds, assessment of the extreme conditions under which the turbine will perform and the theory for calculating the lifetime of the turbine. The classical Blade Element...... Momentum method is also covered, as are eigenmodes and the dynamic behavior of a turbine. The new material includes a description of the effects of the dynamics and how this can be modeled in an aeroelastic code, which is widely used in the design and verification of modern wind turbines. Further...
Computational electromagnetic-aerodynamics
Shang, Joseph J S
2016-01-01
Presents numerical algorithms, procedures, and techniques required to solve engineering problems relating to the interactions between electromagnetic fields, fluid flow, and interdisciplinary technology for aerodynamics, electromagnetics, chemical-physics kinetics, and plasmadynamics This book addresses modeling and simulation science and technology for studying ionized gas phenomena in engineering applications. Computational Electromagnetic-Aerodynamics is organized into ten chapters. Chapter one to three introduce the fundamental concepts of plasmadynamics, chemical-physics of ionization, classical magnetohydrodynamics, and their extensions to plasma-based flow control actuators, high-speed flows of interplanetary re-entry, and ion thrusters in space exploration. Chapter four to six explain numerical algorithms and procedures for solving Maxwell’s equation in the time domain for computational electromagnetics, plasma wave propagation, and the time-dependent c mpressible Navier-Stokes equation for aerodyn...
CFD research, parallel computation and aerodynamic optimization
Ryan, James S.
1995-01-01
Over five years of research in Computational Fluid Dynamics and its applications are covered in this report. Using CFD as an established tool, aerodynamic optimization on parallel architectures is explored. The objective of this work is to provide better tools to vehicle designers. Submarine design requires accurate force and moment calculations in flow with thick boundary layers and large separated vortices. Low noise production is critical, so flow into the propulsor region must be predicted accurately. The High Speed Civil Transport (HSCT) has been the subject of recent work. This vehicle is to be a passenger vehicle with the capability of cutting overseas flight times by more than half. A successful design must surpass the performance of comparable planes. Fuel economy, other operational costs, environmental impact, and range must all be improved substantially. For all these reasons, improved design tools are required, and these tools must eventually integrate optimization, external aerodynamics, propulsion, structures, heat transfer and other disciplines.
Aerodynamic data of space vehicles
Weiland, Claus
2014-01-01
The capacity and quality of the atmospheric flight performance of space flight vehicles is characterized by their aerodynamic data bases. A complete aerodynamic data base would encompass the coefficients of the static longitudinal and lateral motions and the related dynamic coefficients. In this book the aerodynamics of 27 vehicles are considered. Only a few of them did really fly. Therefore the aerodynamic data bases are often not complete, in particular when the projects or programs were more or less abruptly stopped, often due to political decisions. Configurational design studies or the development of demonstrators usually happen with reduced or incomplete aerodynamic data sets. Therefore some data sets base just on the application of one of the following tools: semi-empirical design methods, wind tunnel tests, numerical simulations. In so far a high percentage of the data presented is incomplete and would have to be verified. Flight mechanics needs the aerodynamic coefficients as function of a lot of var...
TAD- THEORETICAL AERODYNAMICS PROGRAM
Barrowman, J.
1994-01-01
This theoretical aerodynamics program, TAD, was developed to predict the aerodynamic characteristics of vehicles with sounding rocket configurations. These slender, axisymmetric finned vehicle configurations have a wide range of aeronautical applications from rockets to high speed armament. Over a given range of Mach numbers, TAD will compute the normal force coefficient derivative, the center-of-pressure, the roll forcing moment coefficient derivative, the roll damping moment coefficient derivative, and the pitch damping moment coefficient derivative of a sounding rocket configured vehicle. The vehicle may consist of a sharp pointed nose of cone or tangent ogive shape, up to nine other body divisions of conical shoulder, conical boattail, or circular cylinder shape, and fins of trapezoid planform shape with constant cross section and either three or four fins per fin set. The characteristics computed by TAD have been shown to be accurate to within ten percent of experimental data in the supersonic region. The TAD program calculates the characteristics of separate portions of the vehicle, calculates the interference between separate portions of the vehicle, and then combines the results to form a total vehicle solution. Also, TAD can be used to calculate the characteristics of the body or fins separately as an aid in the design process. Input to the TAD program consists of simple descriptions of the body and fin geometries and the Mach range of interest. Output includes the aerodynamic characteristics of the total vehicle, or user-selected portions, at specified points over the mach range. The TAD program is written in FORTRAN IV for batch execution and has been implemented on an IBM 360 computer with a central memory requirement of approximately 123K of 8 bit bytes. The TAD program was originally developed in 1967 and last updated in 1972.
Freight Wing Trailer Aerodynamics
Energy Technology Data Exchange (ETDEWEB)
Graham, Sean (Primary Investigator); Bigatel, Patrick
2004-10-17
Freight Wing Incorporated utilized the opportunity presented by this DOE category one Inventions and Innovations grant to successfully research, develop, test, patent, market, and sell innovative fuel and emissions saving aerodynamic attachments for the trucking industry. A great deal of past scientific research has demonstrated that streamlining box shaped semi-trailers can significantly reduce a truck's fuel consumption. However, significant design challenges have prevented past concepts from meeting industry needs. Market research early in this project revealed the demands of truck fleet operators regarding aerodynamic attachments. Products must not only save fuel, but cannot interfere with the operation of the truck, require significant maintenance, add significant weight, and must be extremely durable. Furthermore, SAE/TMC J1321 tests performed by a respected independent laboratory are necessary for large fleets to even consider purchase. Freight Wing used this information to create a system of three practical aerodynamic attachments for the front, rear and undercarriage of standard semi trailers. SAE/TMC J1321 Type II tests preformed by the Transportation Research Center (TRC) demonstrated a 7% improvement to fuel economy with all three products. If Freight Wing is successful in its continued efforts to gain market penetration, the energy and environmental savings would be considerable. Each truck outfitted saves approximately 1,100 gallons of fuel every 100,000 miles, which prevents over 12 tons of CO2 from entering the atmosphere. If all applicable trailers used the technology, the country could save approximately 1.8 billion gallons of diesel fuel, 18 million tons of emissions and 3.6 billion dollars annually.
Hansen, Martin O L
2015-01-01
Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its third edition, it has been substantially updated with respect to structural dynamics and control. The new control chapter now includes details on how to design a classical pitch and torque regulator to control rotational speed and power, while the section on structural dynamics has been extended with a simplified mechanical system explaining the phenomena of forward and backward whirling modes. Readers will also benefit from a new chapter on Vertical Axis W
Zahm, A F
1924-01-01
This report gives the description and the use of a specially designed aerodynamic plane table. For the accurate and expeditious geometrical measurement of models in an aerodynamic laboratory, and for miscellaneous truing operations, there is frequent need for a specially equipped plan table. For example, one may have to measure truly to 0.001 inch the offsets of an airfoil at many parts of its surface. Or the offsets of a strut, airship hull, or other carefully formed figure may require exact calipering. Again, a complete airplane model may have to be adjusted for correct incidence at all parts of its surfaces or verified in those parts for conformance to specifications. Such work, if but occasional, may be done on a planing or milling machine; but if frequent, justifies the provision of a special table. For this reason it was found desirable in 1918 to make the table described in this report and to equip it with such gauges and measures as the work should require.
Mehta, R. D.
1985-01-01
Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.
Mehta, R. D.
Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver
Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its third edition, it has been substantially updated with respect to structural dynamics and control. The new control chapter now includes details on how to design...... Turbines (VAWT). Topics covered include increasing mass flow through the turbine, performance at low and high wind speeds, assessment of the extreme conditions under which the turbine will perform and the theory for calculating the lifetime of the turbine. The classical Blade Element Momentum method...... is also covered, as are eigenmodes and the dynamic behaviour of a turbine. The book describes the effects of the dynamics and how this can be modelled in an aeroelastic code, which is widely used in the design and verification of modern wind turbines. Furthermore, it examines how to calculate...
Wind Turbines Wake Aerodynamics
DEFF Research Database (Denmark)
Vermeer, L.; Sørensen, Jens Nørkær; Crespo, A.
2003-01-01
The aerodynamics of horizontal axis wind turbine wakes is studied. The contents is directed towards the physics of power extraction by wind turbines and reviews both the near and the far wake region. For the near wake, the survey is restricted to uniform, steady and parallel flow conditions......, thereby excluding wind shear, wind speed and rotor setting changes and yawed conditions. The emphasis is put on measurements in controlled conditions.For the far wake, the survey focusses on both single turbines and wind farm effects, and the experimental and numerical work are reviewed; the main interest...... is to study how the far wake decays downstream, in order to estimate the effect produced in downstream turbines.The article is further restricted to horizontal axis wind turbines and excludes all other types of turbines....
DEFF Research Database (Denmark)
Kleissl, Kenneth
This dissertation investigates the possibility of preventing wind-induced cable vibrations on cable-stayed bridges using passive aerodynamic means in the form of cable surface modifications. Especially the phenomenon of rainwind induced vibrations, which is known as the most common type...... of these vibrations and capable of inducing severe vibrations. The recent increase in the number of cable stayed bridges continuously becoming longer and lighter have resulted in a high number of observations of cable vibrations. A detailed literature review of the various types of passive means led...... with a sudden change in the lift during the flow transition, which could be the reason for a dry limited amplitude vibration observed only for cables with helical applications. Dry inclined galloping was only seen with the plain reference cable model, even though only the helically filleted cable was capable...
Introduction to transonic aerodynamics
Vos, Roelof
2015-01-01
Written to teach students the nature of transonic flow and its mathematical foundation, this book offers a much-needed introduction to transonic aerodynamics. The authors present a quantitative and qualitative assessment of subsonic, supersonic, and transonic flow around bodies in two and three dimensions. The book reviews the governing equations and explores their applications and limitations as employed in modeling and computational fluid dynamics. Some concepts, such as shock and expansion theory, are examined from a numerical perspective. Others, including shock-boundary-layer interaction, are discussed from a qualitative point of view. The book includes 60 examples and more than 200 practice problems. The authors also offer analytical methods such as Method of Characteristics (MOC) that allow readers to practice with the subject matter. The result is a wealth of insight into transonic flow phenomena and their impact on aircraft design, including compressibility effects, shock and expansion waves, sho...
Naval Aerodynamics Test Facility (NATF)
Federal Laboratory Consortium — The NATF specializes in Aerodynamics testing of scaled and fullsized Naval models, research into flow physics found on US Navy planes and ships, aerosol testing and...
The aerodynamics of wind turbines
DEFF Research Database (Denmark)
Sørensen, Jens Nørkær; Mikkelsen, Robert Flemming; Troldborg, Niels;
2013-01-01
In the paper we present state-of-the-art of research in wind turbine aerodynamics. We start be giving a brief historical review and a survey over aerodynamic research in wind energy. Next, we focus on some recent research results obtained by our wind energy group at Department of Mechanical Engin...... Engineering at DTU. In particular, we show some new results on the classical problem of the ideal rotor and present a series of new results from an on-going research project dealing with the modelling and simulation of turbulent flow structures in the wake behind wind turbines.......In the paper we present state-of-the-art of research in wind turbine aerodynamics. We start be giving a brief historical review and a survey over aerodynamic research in wind energy. Next, we focus on some recent research results obtained by our wind energy group at Department of Mechanical...
Turbine Aerodynamics Design Tool Development
Huber, Frank W.; Turner, James E. (Technical Monitor)
2001-01-01
This paper presents the Marshal Space Flight Center Fluids Workshop on Turbine Aerodynamic design tool development. The topics include: (1) Meanline Design/Off-design Analysis; and (2) Airfoil Contour Generation and Analysis. This paper is in viewgraph form.
Computational aerodynamics and artificial intelligence
Mehta, U. B.; Kutler, P.
1984-01-01
The general principles of artificial intelligence are reviewed and speculations are made concerning how knowledge based systems can accelerate the process of acquiring new knowledge in aerodynamics, how computational fluid dynamics may use expert systems, and how expert systems may speed the design and development process. In addition, the anatomy of an idealized expert system called AERODYNAMICIST is discussed. Resource requirements for using artificial intelligence in computational fluid dynamics and aerodynamics are examined. Three main conclusions are presented. First, there are two related aspects of computational aerodynamics: reasoning and calculating. Second, a substantial portion of reasoning can be achieved with artificial intelligence. It offers the opportunity of using computers as reasoning machines to set the stage for efficient calculating. Third, expert systems are likely to be new assets of institutions involved in aeronautics for various tasks of computational aerodynamics.
THERMAL AND AERODYNAMIC PERFORMANCES OF THE SUPERSONIC MOTION
Directory of Open Access Journals (Sweden)
Dejan P Ninković
2010-01-01
Full Text Available Generally speaking, Mach number of 4 can be taken as a boundary value for transition from conditions for supersonic, into the area of hypersonic flow, distinguishing two areas: area of supersonic in which the effects of the aerodynamic heating can be neglected and the area of hypersonic, in which the thermal effects become dominant. This paper presents the effects in static and dynamic areas, as well as presentation of G.R.O.M. software for determination of the values of aerodynamic derivatives, which was developed on the basis of linearized theory of supersonic flow. Validation of developed software was carried out through different types of testing, proving its usefulness for engineering practice in the area of supersonic wing aerodynamic loading calculations, even at high Mach numbers, with dominant thermal effects.
Introduction to wind turbine aerodynamics
Schaffarczyk, Alois Peter
2014-01-01
Wind-Turbine Aerodynamics is a self-contained textbook which shows how to come from the basics of fluid mechanics to modern wind turbine blade design. It presents a fundamentals of fluid dynamics and inflow conditions, and gives a extensive introduction into theories describing the aerodynamics of wind turbines. After introducing experiments the book applies the knowledge to explore the impact on blade design.The book is an introduction for professionals and students of very varying levels.
Aerodynamic and aerothermodynamic analysis of space mission vehicles
Viviani, Antonio
2015-01-01
Presenting an up-to-date view on the most important space vehicle configurations, this book contains detailed analyses for several different type of space mission profiles while considering important factors such as aerodynamic loads, aerodynamic heating, vehicle stability and landing characteristics. With that in mind, the authors provide a detailed overview on different state-of-the-art themes of hypersonic aerodynamics and aerothermodynamics, and consider different space vehicle shapes useful for different space mission objectives. These include: · Crew Return Vehicle (CRV) · Crew Exploration Vehicle (CEV) · Sample Return Vehicle (SRV) · Flying Test Bed (FTB). Throughout Aerodynamic and Aerothermodynamic Analysis of Space Mission Vehicles many examples are given, with detailed computations and results for the aerodynamics and aerothermodynamics of all such configurations. Moreover, a final chapter on future launchers is provided and an Appendix on...
Aerodynamics of badminton shuttlecocks
Verma, Aekaansh; Desai, Ajinkya; Mittal, Sanjay
2013-08-01
A computational study is carried out to understand the aerodynamics of shuttlecocks used in the sport of badminton. The speed of the shuttlecock considered is in the range of 25-50 m/s. The relative contribution of various parts of the shuttlecock to the overall drag is studied. It is found that the feathers, and the net in the case of a synthetic shuttlecock, contribute the maximum. The gaps, in the lower section of the skirt, play a major role in entraining the surrounding fluid and causing a difference between the pressure inside and outside the skirt. This pressure difference leads to drag. This is confirmed via computations for a shuttlecock with no gaps. The synthetic shuttle experiences more drag than the feather model. Unlike the synthetic model, the feather shuttlecock is associated with a swirling flow towards the end of the skirt. The effect of the twist angle of the feathers on the drag as well as the flow has also been studied.
Introduction. Computational aerodynamics.
Tucker, Paul G
2007-10-15
The wide range of uses of computational fluid dynamics (CFD) for aircraft design is discussed along with its role in dealing with the environmental impact of flight. Enabling technologies, such as grid generation and turbulence models, are also considered along with flow/turbulence control. The large eddy simulation, Reynolds-averaged Navier-Stokes and hybrid turbulence modelling approaches are contrasted. The CFD prediction of numerous jet configurations occurring in aerospace are discussed along with aeroelasticity for aeroengine and external aerodynamics, design optimization, unsteady flow modelling and aeroengine internal and external flows. It is concluded that there is a lack of detailed measurements (for both canonical and complex geometry flows) to provide validation and even, in some cases, basic understanding of flow physics. Not surprisingly, turbulence modelling is still the weak link along with, as ever, a pressing need for improved (in terms of robustness, speed and accuracy) solver technology, grid generation and geometry handling. Hence, CFD, as a truly predictive and creative design tool, seems a long way off. Meanwhile, extreme practitioner expertise is still required and the triad of computation, measurement and analytic solution must be judiciously used.
Discrete vortex method simulations of aerodynamic admittance in bridge aerodynamics
DEFF Research Database (Denmark)
Rasmussen, Johannes Tophøj; Hejlesen, Mads Mølholm; Larsen, Allan;
The meshless and remeshed Discrete Vortex Method (DVM) has been widely used in academia and by the industry to model two-dimensional ﬂow around bluff bodies. The implementation “DVMFLOW” [1] is used by the bridge design company COWI to determine and visualise the ﬂow ﬁeld around bridge sections......, and to determine aerodynamic forces and the corresponding ﬂutter limit. A simulation of the three-dimensional bridge responseto turbulent wind is carried out by quasi steady theory by modelling the bridge girder as a line like structure [2], applying the aerodynamic load coefﬁcients found from the current version...... of DVMFLOW in a strip wise fashion. Neglecting the aerodynamic admittance, i.e. the correlation of the instantaneous lift force to the turbulent ﬂuctuations in the vertical velocities, leads to higher response to high frequency atmospheric turbulence than would be obtained from wind tunnel tests....
Discrete vortex method simulations of aerodynamic admittance in bridge aerodynamics
DEFF Research Database (Denmark)
Rasmussen, Johannes Tophøj; Hejlesen, Mads Mølholm; Larsen, Allan;
velocity spectra are found in good agreement with the target spectra. The aerodynamic admittance of the structure is measured by sampling vertical velocities immediately upstream of the structure and the lift forces on the structure. The method is validated against the analytic solution for the admittance......The meshless and remeshed Discrete Vortex Method (DVM) has been widely used in academia and by the industry to model two-dimensional ﬂow around bluff bodies. The implementation “DVMFLOW” [1] is used by the bridge design company COWI to determine and visualise the ﬂow ﬁeld around bridge sections......, and to determine aerodynamic forces and the corresponding ﬂutter limit. A simulation of the three-dimensional bridge responseto turbulent wind is carried out by quasi steady theory by modelling the bridge girder as a line like structure [2], applying the aerodynamic load coefﬁcients found from the current version...
Institute of Scientific and Technical Information of China (English)
吴大方; 潘兵; 郑力铭; 王岳武; 牟朦; 朱林; 李松年
2012-01-01
This paper describes the principles and capabilities of a self-developed radiation-based aerodynamic heating simulation system, and demonstrates its applications in the thermal testing and high-temperature strength testing of the materials and structures used in hypersonic flight vehicles. The aerodynamic heating simulation system is capable of producing nonlinear dynamic thermal shocks with a heating rate up to 200 ℃/s, a heat flux of 1.8 MW/m2, and a highest temperature up to 1500℃. A number of experiments were carried out on the developed heating simulation system. These experiments include: (1) the heat-insulation property testing for a high-temperature composite materials SiC/SiC specimen at high-temperature of 1300~1500℃; (2) experimental and numerical investigations of the heat-shielding properties of metallic honeycomb panel structure in non-linear thermal environment up to 950℃; (3) high-temperature thermal environment simulation experiment for the inner surface of a 2.1 m long circular shell, which uses a novel axial non-segmented single regional approach to improve the uniformity of the in-wall temperature field of a large structure. By using non-contact optical metrology, the full-field high-temperature deformation can be measured up to 1550℃. This aerodynamic heating simulation system and the testing methods reach or approach the advanced international standards in terms of the controllable non-linear rate of the temperature rise, the dynamic change process simulation of high-temperature and high heat flux density, the accuracy in the thermal experimental environment simulation and the non-contact full-field deformation measurement method for high-temperature objects.%文章介绍了自行研制的石英灯红外辐射式气动加热试验模拟系统以及使用该系统对高超声速飞行器材料与结构进行的高温热评价试验.本热试验系统可实现升温速率高至200℃/s的非线性热冲击过
Fundamentals of modern unsteady aerodynamics
Gülçat, Ülgen
2016-01-01
In this book, the author introduces the concept of unsteady aerodynamics and its underlying principles. He provides the readers with a comprehensive review of the fundamental physics of free and forced unsteadiness, the terminology and basic equations of aerodynamics ranging from incompressible flow to hypersonics. The book also covers modern topics related to the developments made in recent years, especially in relation to wing flapping for propulsion. The book is written for graduate and senior year undergraduate students in aerodynamics and also serves as a reference for experienced researchers. Each chapter includes ample examples, questions, problems and relevant references. The treatment of these modern topics has been completely revised end expanded for the new edition. It now includes new numerical examples, a section on the ground effect, and state-space representation.
Aerodynamic map for soft and hard hypersonic level flight in near space
Institute of Scientific and Technical Information of China (English)
Ruifeng Hu; Ziniu Wu; Zhe Wu; Xiaoxin Wang; Zhongwei Tian
2009-01-01
In this note, we design a velocity-altitude map for hypersonic level flight in near space of altitude 20-100 km. This map displays aerodynamic-related parameters associated with near space level flight, schematically or quantitatively. Various physical conditions for the near-space level flight are then characterized, including laminar or turbulent flow, rarefaction or continuous flow, aerodynamic heating, as well as conditions for sustaining level flight with and without orbital effect. This map allows one to identify conditions to have soft flight or hard flight, and this identification would be helpful for making correct planning on detailed studies of aerodynamics or making initial design of near space vehicles.
Aerodynamics Research Revolutionizes Truck Design
2008-01-01
During the 1970s and 1980s, researchers at Dryden Flight Research Center conducted numerous tests to refine the shape of trucks to reduce aerodynamic drag and improved efficiency. During the 1980s and 1990s, a team based at Langley Research Center explored controlling drag and the flow of air around a moving body. Aeroserve Technologies Ltd., of Ottawa, Canada, with its subsidiary, Airtab LLC, in Loveland, Colorado, applied the research from Dryden and Langley to the development of the Airtab vortex generator. Airtabs create two counter-rotating vortices to reduce wind resistance and aerodynamic drag of trucks, trailers, recreational vehicles, and many other vehicles.
Rotor/body aerodynamic interactions
Betzina, M. D.; Smith, C. A.; Shinoda, P.
1985-01-01
A wind tunnel investigation was conducted in which independent, steady state aerodynamic forces and moments were measured on a 2.24 m diam. two bladed helicopter rotor and on several different bodies. The mutual interaction effects for variations in velocity, thrust, tip-path-plane angle of attack, body angle of attack, rotor/body position, and body geometry were determined. The results show that the body longitudinal aerodynamic characteristics are significantly affected by the presence of a rotor and hub, and that the hub interference may be a major part of such interaction. The effects of the body on the rotor performance are presented.
Schepers, J.G.
2012-01-01
The subject of aerodynamics is of major importance for the successful deployment of wind energy. As a matter of fact there are two aerodynamic areas in the wind energy technology: Rotor aerodynamics and wind farm aerodynamics. The first subject considers the flow around the rotor and the second subj
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The aerodynamic roughness z0m, the thermodynamic roughness z0h and the excess resistance to heat transfer kB-1 are analyzed with the data obtained from Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment on Tibetan Plateau (GAME/Tibet) in the Intensive Observation Period (IOP), 1998. Some new concepts on the aerodynamic and thermodynamic parameters over the grassy marshland surface of the Tibetan Plateau are proposed.
Description of an aerodynamic levitation apparatus with applications in Earth sciences
Simon Klaus; Albrecht Nina; Kremer Katrina; Pack Andreas; Kronz Andreas
2010-01-01
Abstract Background In aerodynamic levitation, solids and liquids are floated in a vertical gas stream. In combination with CO2-laser heating, containerless melting at high temperature of oxides and silicates is possible. We apply aerodynamic levitation to bulk rocks in preparation for microchemical analyses, and for evaporation and reduction experiments. Results Liquid silicate droplets (~2 mm) were maintained stable in levitation using a nozzle with a 0.8 mm bore and an opening angle of 60°...
Aerodynamic levitation : an approach to microgravity.
Energy Technology Data Exchange (ETDEWEB)
Glorieux, B.; Saboungi, M.-L.; Millot, F.; Enderby, J.; Rifflet, J.-C.
2000-12-05
Measurements of the thermophysical and structural properties of liquid materials at high temperature have undergone considerable development in the past few years. Following improvements in electromagnetic levitation, aerodynamic levitation associated with laser heating has shown promise for assessing properties of different molten materials (metals, oxides, and semiconductors), preserving sample purity over a wide range of temperatures and under different gas environments. The density, surface tension and viscosity are measured with a high-speed video camera and an image analysis system. Results on nickel and alumina show that small droplets can be considered in the first approximation to be under microgravity conditions. Using a non-invasive contactless technique recently developed to measure electrical conductivity, results have been extended to variety of materials ranging from liquid metals and liquid semiconductors to ionically conducting materials. The advantage of this technique is the feasibility of monitoring changes in transport occurring during phase transitions and in deeply undercooled states.
Unsteady aerodynamics modeling for flight dynamics application
Wang, Qing; He, Kai-Feng; Qian, Wei-Qi; Zhang, Tian-Jiao; Cheng, Yan-Qing; Wu, Kai-Yuan
2012-02-01
In view of engineering application, it is practicable to decompose the aerodynamics into three components: the static aerodynamics, the aerodynamic increment due to steady rotations, and the aerodynamic increment due to unsteady separated and vortical flow. The first and the second components can be presented in conventional forms, while the third is described using a one-order differential equation and a radial-basis-function (RBF) network. For an aircraft configuration, the mathematical models of 6-component aerodynamic coefficients are set up from the wind tunnel test data of pitch, yaw, roll, and coupled yawroll large-amplitude oscillations. The flight dynamics of an aircraft is studied by the bifurcation analysis technique in the case of quasi-steady aerodynamics and unsteady aerodynamics, respectively. The results show that: (1) unsteady aerodynamics has no effect upon the existence of trim points, but affects their stability; (2) unsteady aerodynamics has great effects upon the existence, stability, and amplitudes of periodic solutions; and (3) unsteady aerodynamics changes the stable regions of trim points obviously. Furthermore, the dynamic responses of the aircraft to elevator deflections are inspected. It is shown that the unsteady aerodynamics is beneficial to dynamic stability for the present aircraft. Finally, the effects of unsteady aerodynamics on the post-stall maneuverability are analyzed by numerical simulation.
Unsteady aerodynamics modeling for flight dynamics application
Institute of Scientific and Technical Information of China (English)
Qing Wang; Kai-Feng He; Wei-Qi Qian; Tian-Jiao Zhang; Yan-Qing Cheng; Kai-Yuan Wu
2012-01-01
In view of engineering application,it is practicable to decompose the aerodynamics into three components:the static aerodynamics,the aerodynamic increment due to steady rotations,and the aerodynamic increment due to unsteady separated and vortical flow.The first and the second components can be presented in conventional forms,while the third is described using a one-order differential equation and a radial-basis-function (RBF) network. For an aircraft configuration,the mathematical models of 6-component aerodynamic coefficients are set up from the wind tunnel test data of pitch,yaw,roll,and coupled yawroll large-amplitude oscillations.The flight dynamics of an aircraft is studied by the bifurcation analysis technique in the case of quasi-steady aerodynamics and unsteady aerodynamics,respectively.The results show that:(1) unsteady aerodynamics has no effect upon the existence of trim points,but affects their stability; (2) unsteady aerodynamics has great effects upon the existence,stability,and amplitudes of periodic solutions; and (3) unsteady aerodynamics changes the stable regions of trim points obviously.Furthermore,the dynamic responses of the aircraft to elevator deflections are inspected.It is shown that the unsteady aerodynamics is beneficial to dynamic stability for the present aircraft.Finally,the effects of unsteady aerodynamics on the post-stall maneuverability are analyzed by numerical simulation.
POEMS in Newton's Aerodynamic Frustum
Sampedro, Jaime Cruz; Tetlalmatzi-Montiel, Margarita
2010-01-01
The golden mean is often naively seen as a sign of optimal beauty but rarely does it arise as the solution of a true optimization problem. In this article we present such a problem, demonstrating a close relationship between the golden mean and a special case of Newton's aerodynamical problem for the frustum of a cone. Then, we exhibit a parallel…
Aerodynamics and thermal physics of helicopter ice accretion
Han, Yiqiang
Ice accretion on aircraft introduces significant loss in airfoil performance. Reduced lift-to- drag ratio reduces the vehicle capability to maintain altitude and also limits its maneuverability. Current ice accretion performance degradation modeling approaches are calibrated only to a limited envelope of liquid water content, impact velocity, temperature, and water droplet size; consequently inaccurate aerodynamic performance degradations are estimated. The reduced ice accretion prediction capabilities in the glaze ice regime are primarily due to a lack of knowledge of surface roughness induced by ice accretion. A comprehensive understanding of the ice roughness effects on airfoil heat transfer, ice accretion shapes, and ultimately aerodynamics performance is critical for the design of ice protection systems. Surface roughness effects on both heat transfer and aerodynamic performance degradation on airfoils have been experimentally evaluated. Novel techniques, such as ice molding and casting methods and transient heat transfer measurement using non-intrusive thermal imaging methods, were developed at the Adverse Environment Rotor Test Stand (AERTS) facility at Penn State. A novel heat transfer scaling method specifically for turbulent flow regime was also conceived. A heat transfer scaling parameter, labeled as Coefficient of Stanton and Reynolds Number (CSR = Stx/Rex --0.2), has been validated against reference data found in the literature for rough flat plates with Reynolds number (Re) up to 1x107, for rough cylinders with Re ranging from 3x104 to 4x106, and for turbine blades with Re from 7.5x105 to 7x106. This is the first time that the effect of Reynolds number is shown to be successfully eliminated on heat transfer magnitudes measured on rough surfaces. Analytical models for ice roughness distribution, heat transfer prediction, and aerodynamics performance degradation due to ice accretion have also been developed. The ice roughness prediction model was
OPTIMIZATION OF AERODYNAMIC CONDITIONS OF THE CHAMBER DRIER OPERATION
Directory of Open Access Journals (Sweden)
V. A. Sychevsky
2016-01-01
Full Text Available Wood utilization is a critical direction of the industrial production advancement, where desiccation of wood holds a prominent place. Convective drying in chamber driers is the presentday dominant technique for wood desiccation. Nevertheless, available scientific literature on the subject does not place high emphasis on the issue of gas flow structure inside the drier installations and, in particular, in the clearance between horizontal rows of stacked saw timber. Whereas, the air flowing between horizontal rows facilitates wood heating and moisture removing from the boundary layer. The present article studies aerodynamics of the experimental timber drying test stand at the A. V. Luikov Heat and Mass Transfer Institute of NAS of Belarus. The timber drying test stand geometry structure is complicated, which is why aerodynamics valuation of the drier agent in the chamber involves the software system ANSYS Fluent 14.5. For that end, the researchers developed the convective drier installation geometrical model. A physico-mathematical simulation was developed for sawn timber convective drying aerodynamics in the timber drying test stand of the Heat and Mass Transfer Institute. Based on the computations made, the drier agent flow configuration was analyzed, stagnant pockets identified. It was found that the timber drying test stand was not operating within its optimal aerodynamic conditions. The drying chamber optimal aerodynamic conditions determination includes accounting for an additional canal between the chamber rear wall and the timber stack, absence of the screen above the stack, and presence of the screen between the floor and the stack. As well as variation of the drying agent speed, pressure differrential at the blower, the inter-row gobb amount variation. The paper offers recommendations on optimizing the drying installation aerodynamics based on the numerical simulation results. To this effect, speed of the drier agent in the chamber
WIND TURBINE MASS AND AERODYNAMIC IMBALANCES DETERMINATION
Nduwayezu Eric; Mehmet Bayrak
2015-01-01
This paper evaluates the use of simulations to investigate wind turbine mass and aerodynamic imbalances. Faults caused by mass and aerodynamic imbalances constitute a significant portion of all faults in wind turbine. The aerodynamic imbalances effects such as deviations between the three blades pitch angle are often underrated and misunderstood. In practice, for many wind energy converters the blade adjustment is found to be sub-optimal. The dynamics of a model wind turbine was s...
Schepers, J. G.
2012-01-01
The subject of aerodynamics is of major importance for the successful deployment of wind energy. As a matter of fact there are two aerodynamic areas in the wind energy technology: Rotor aerodynamics and wind farm aerodynamics. The first subject considers the flow around the rotor and the second subject considers the (wake) flow within a wind farm. For both areas calculational models have been developed which are implemented i rotor design and wind farm design codes respectively. Accurate roto...
Aerodynamics Laboratory Facilities, Equipment, and Capabilities
Federal Laboratory Consortium — The following facilities, equipment, and capabilities are available in the Aerodynamics Laboratory Facilities and Equipment (1) Subsonic, open-jet wind tunnel with...
Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Project
National Aeronautics and Space Administration — The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) project will focus on the development and demonstration of hypersonic inflatable aeroshell technologies...
The basic aerodynamics of floatation
Energy Technology Data Exchange (ETDEWEB)
Davies, M.J.; Wood, D.H.
1983-09-01
The original derivation of the basic theory governing the aerodynamics of both hovercraft and modern floatation ovens, requires the validity of some extremely crude assumptions. However, the basic theory is surprisingly accurate. It is shown that this accuracy occurs because the final expression of the basic theory can be derived by approximating the full Navier-Stokes equations in a manner that clearly shows the limitations of the theory. These limitations are used in discussing the relatively small discrepancies between the theory and experiment, which may not be significant for practical purposes.
Leading Edge Device Aerodynamic Optimization
Directory of Open Access Journals (Sweden)
Marius Gabriel COJOCARU
2015-12-01
Full Text Available Leading edge devices are conventionally used as aerodynamic devices that enhance performances during landing and in some cases during takeoff. The need to increase the efficiency of the aircrafts has brought the idea of maintaining as much as possible a laminar flow over the wings. This is possible only when the leading edge of the wings is free from contamination, therefore using the leading edge devices with the additional role of shielding during takeoff. Such a device based on the Krueger flap design is aerodynamically analyzed and optimized. The optimization comprises three steps: first, the positioning of the flap such that the shielding criterion is kept, second, the analysis of the flap size and third, the optimization of the flap shape. The first step is subject of a gradient based optimization process of the position described by two parameters, the position along the line and the deflection angle. For the third step the Adjoint method is used to gain insight on the shape of the Krueger flap that will extend the most the stall limit. All these steps have been numerically performed using Ansys Fluent and the results are presented for the optimized shape in comparison with the baseline configuration.
Review paper on wind turbine aerodynamics
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver; Aagaard Madsen, Helge
2011-01-01
The paper describes the development and description of the aerodynamic models used to estimate the aerodynamic loads on wind turbine constructions. This includes a status of the capabilities of computation fluid dynamics and the need for reliable airfoil data for the simpler engineering models...
Aerodynamics of wind turbines emerging topics
Amano, R S
2014-01-01
Focusing on Aerodynamics of Wind Turbines with topics ranging from Fundamental to Application of horizontal axis wind turbines, this book presents advanced topics including: Basic Theory for Wind turbine Blade Aerodynamics, Computational Methods, and Special Structural Reinforcement Technique for Wind Turbine Blades.
Aerodynamic seal assemblies for turbo-machinery
Energy Technology Data Exchange (ETDEWEB)
Bidkar, Rahul Anil; Wolfe, Christopher; Fang, Biao
2015-09-29
The present application provides an aerodynamic seal assembly for use with a turbo-machine. The aerodynamic seal assembly may include a number of springs, a shoe connected to the springs, and a secondary seal positioned about the springs and the shoe.
Migration on Wings Aerodynamics and Energetics
Kantha, Lakshmi
2012-01-01
This book is an effort to explore the technical aspects associated with bird flight and migration on wings. After a short introduction on the birds migration, the book reviews the aerodynamics and Energetics of Flight and presents the calculation of the Migration Range. In addition, the authors explains aerodynamics of the formation flight and finally introduces great flight diagrams.
Biomimetic Approach for Accurate, Real-Time Aerodynamic Coefficients Project
National Aeronautics and Space Administration — Aerodynamic and structural reliability and efficiency depends critically on the ability to accurately assess the aerodynamic loads and moments for each lifting...
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
Aerodynamic seals for rotary machine
Energy Technology Data Exchange (ETDEWEB)
Bidkar, Rahul Anil; Cirri, Massimiliano; Thatte, Azam Mihir; Williams, John Robert
2016-02-09
An aerodynamic seal assembly for a rotary machine includes multiple sealing device segments disposed circumferentially intermediate to a stationary housing and a rotor. Each of the segments includes a shoe plate with a forward-shoe section and an aft-shoe section having multiple labyrinth teeth therebetween facing the rotor. The sealing device segment also includes multiple flexures connected to the shoe plate and to a top interface element, wherein the multiple flexures are configured to allow the high pressure fluid to occupy a forward cavity and the low pressure fluid to occupy an aft cavity. Further, the sealing device segments include a secondary seal attached to the top interface element at one first end and positioned about the flexures and the shoe plate at one second end.
Aerodynamic research on tipvane windturbines
Vanbussel, G. J. W.; Vanholten, T.; Vankuik, G. A. M.
1982-09-01
Tipvanes are small auxiliary wings mounted at the tips of windturbine blades in such a way that a diffuser effect is generated, resulting in a mass flow augmentation through the turbine disc. For predicting aerodynamic loads on the tipvane wind turbine, the acceleration potential is used and an expansion method is applied. In its simplest form, this method can essentially be classified as a lifting line approach, however, with a proper choice of the basis load distributions of the lifting line, the numerical integration of the pressurefield becomes one dimensional. the integration of the other variable can be performed analytically. The complete analytical expression for the pressure field consists of two series of basic pressure fields. One series is related to the basic load distributions over the turbineblade, and the other series to the basic load distribution over the tipvane.
The basic aerodynamics of floatation
Davies, M. J.; Wood, D. H.
1983-09-01
It is pointed out that the basic aerodynamics of modern floatation ovens, in which the continuous, freshly painted metal strip is floated, dried, and cured, is the two-dimensional analog of that of hovercraft. The basic theory for the static lift considered in connection with the study of hovercraft has had spectacular success in describing the experimental results. This appears surprising in view of the crudity of the theory. The present investigation represents an attempt to explore the reasons for this success. An outline of the basic theory is presented and an approach is shown for deriving the resulting expressions for the lift from the full Navier-Stokes equations in a manner that clearly indicates the limitations on the validity of the expressions. Attention is given to the generally good agreement between the theory and the axisymmetric (about the centerline) results reported by Jaumotte and Kiedrzynski (1965).
Directory of Open Access Journals (Sweden)
J. H. Lee
2012-04-01
Full Text Available Aerodynamic roughness height (Z_{om} is a key parameter required in land surface hydrological model, since errors in heat flux estimations are largely dependent on accurate optimization of this parameter. Despite its significance, it remains an uncertain parameter that is not easily determined. This is mostly because of non-linear relationship in Monin-Obukhov Similarity (MOS and unknown vertical characteristic of vegetation. Previous studies determined aerodynamic roughness using traditional wind profile method, remotely sensed vegetation index, minimization of cost function over MOS relationship or linear regression. However, these are complicated procedures that presume high accuracy for several other related parameters embedded in MOS equations. In order to simplify a procedure and reduce the number of parameters in need, this study suggests a new approach to extract aerodynamic roughness parameter via Ensemble Kalman Filter (EnKF that affords non-linearity and that requires only single or two heat flux measurement. So far, to our knowledge, no previous study has applied EnKF to aerodynamic roughness estimation, while a majority of data assimilation study has paid attention to land surface state variables such as soil moisture or land surface temperature. This approach was applied to grassland in semi-arid Tibetan area and maize on moderately wet condition in Italy. It was demonstrated that aerodynamic roughness parameter can inversely be tracked from data assimilated heat flux analysis. The aerodynamic roughness height estimated in this approach was consistent with eddy covariance result and literature value. Consequently, this newly estimated input adjusted the sensible heat overestimated and latent heat flux underestimated by the original Surface Energy Balance System (SEBS model, suggesting better heat flux estimation especially during the summer Monsoon period. The advantage of this approach over other methodologies is
Active Control of Aerodynamic Noise Sources
Reynolds, Gregory A.
2001-01-01
Aerodynamic noise sources become important when propulsion noise is relatively low, as during aircraft landing. Under these conditions, aerodynamic noise from high-lift systems can be significant. The research program and accomplishments described here are directed toward reduction of this aerodynamic noise. Progress toward this objective include correction of flow quality in the Low Turbulence Water Channel flow facility, development of a test model and traversing mechanism, and improvement of the data acquisition and flow visualization capabilities in the Aero. & Fluid Dynamics Laboratory. These developments are described in this report.
Nayeri, Christian Navid; Löfdahl, Lennart; Schober, Martin
2009-01-01
During the 509th Colloquium of the Euromech society, held from March 24th & 25th at TU Berlin, fifty leading researchers from all over europe discussed various topics affecting both road vehicle as well as railway vehicle aerodynamics, especially drag reduction (with road vehicles), cross wind stability (with trains) and wake analysis (with both). With the increasing service speed of modern high-speed railway traffic, aerodynamic aspects are gaining importance. The aerodynamic research topics...
Prediction of Unsteady Transonic Aerodynamics Project
National Aeronautics and Space Administration — An accurate prediction of aero-elastic effects depends on an accurate prediction of the unsteady aerodynamic forces. Perhaps the most difficult speed regime is...
Aerodynamic Efficiency Enhancements for Air Vehicles Project
National Aeronautics and Space Administration — The need for aerodynamics-based efficiency enhancements for air vehicles is presented. The results of the Phase I investigation of concepts for morphing aircraft...
Uniaxial aerodynamic attitude control of artificial satellites
Sazonov, V. V.
1983-01-01
Within the context of a simple mechanical model the paper examines the movement of a satellite with respect to the center of masses under conditions of uniaxial aerodynamic attitude control. The equations of motion of the satellite take account of the gravitational and restorative aerodynamic moments. It is presumed that the aerodynamic moment is much larger than the gravitational, and the motion equations contain a large parameter. A two-parameter integrated surface of these equations is constructed in the form of formal series in terms of negative powers of the large parameter, describing the oscillations and rotations of the satellite about its lengthwise axis, approximately oriented along the orbital tangent. It is proposed to treat such movements as nominal undisturbed motions of the satellite under conditions of aerodynamic attitude control. A numerical investigation is made for the above integrated surface.
Aerodynamic Efficiency Enhancements for Air Vehicles Project
National Aeronautics and Space Administration — The need for aerodynamics-based efficiency enhancements for air vehicles is presented. Concepts are presented for morphing aircraft, to enable the aircraft to...
Computational Hypersonic Aerodynamics with Emphasis on Earth Reentry Capsules
Directory of Open Access Journals (Sweden)
Mihai Leonida NICULESCU
2016-09-01
Full Text Available The temperature in the front region of a hypersonic vehicle nose can be extremely high, for example, reaching approximately 11 000 K at a Mach number of 36 (Apollo reentry due to the bow shock wave. In this case, accurate prediction of temperature behind the shock wave is necessary in order to precisely estimate the wall heat flux. A better prediction of wall heat flux leads to smaller safety coefficient for thermal shield of space reentry vehicle; therefore, the size of thermal shield decreases and the payload could increase. However, the accurate prediction of temperature behind the bow shock wave implies the use of a precise chemical model whose partial differential equations are added to Navier-Stokes equations. This second order partial differential system is very difficult to be numerically integrated. For this reason, the present paper deals with the computational hypersonic aerodynamics with chemical reactions with the aim of supporting Earth reentry capsule design.
Computer Aided Aerodynamic Design of Missile Configuration
Panneerselvam, S; P. Theerthamalai; A.K. Sarkar
1987-01-01
Aerodynamic configurations of tactical missiles have to produce the required lateral force with minimum time lag to meet the required manoeuvability and response time. The present design which is mainly based on linearised potential flow involves (a) indentification of critical design points, (b) design of lifting components and their integration with mutual interference, (c) evaluation of aerodynamic characteristics, (d) checking its adequacy at otherpoints, (e) optimization of parameters an...
Aerodynamics of Unsteady Sailing Kinetics
Keil, Colin; Schutt, Riley; Borshoff, Jennifer; Alley, Philip; de Zegher, Maximilien; Williamson, Chk
2015-11-01
In small sailboats, the bodyweight of the sailor is proportionately large enough to induce significant unsteady motion of the boat and sail. Sailors use a variety of kinetic techniques to create sail dynamics which can provide an increment in thrust, thereby increasing the boatspeed. In this study, we experimentally investigate the unsteady aerodynamics associated with two techniques, ``upwind leech flicking'' and ``downwind S-turns''. We explore the dynamics of an Olympic class Laser sailboat equipped with a GPS, IMU, wind sensor, and camera array, sailed expertly by a member of the US Olympic team. The velocity heading of a sailing boat is oriented at an apparent wind angle to the flow. In contrast to classic flapping propulsion, the heaving of the sail section is not perpendicular to the sail's motion through the air. This leads to heave with components parallel and perpendicular to the incident flow. The characteristic motion is recreated in a towing tank where the vortex structures generated by a representative 2-D sail section are observed using Particle Image Velocimetry and the measurement of thrust and lift forces. Amongst other results, we show that the increase in driving force, generated due to heave, is larger for greater apparent wind angles.
Skylon Aerodynamics and SABRE Plumes
Mehta, Unmeel; Afosmis, Michael; Bowles, Jeffrey; Pandya, Shishir
2015-01-01
An independent partial assessment is provided of the technical viability of the Skylon aerospace plane concept, developed by Reaction Engines Limited (REL). The objectives are to verify REL's engineering estimates of airframe aerodynamics during powered flight and to assess the impact of Synergetic Air-Breathing Rocket Engine (SABRE) plumes on the aft fuselage. Pressure lift and drag coefficients derived from simulations conducted with Euler equations for unpowered flight compare very well with those REL computed with engineering methods. The REL coefficients for powered flight are increasingly less acceptable as the freestream Mach number is increased beyond 8.5, because the engineering estimates did not account for the increasing favorable (in terms of drag and lift coefficients) effect of underexpanded rocket engine plumes on the aft fuselage. At Mach numbers greater than 8.5, the thermal environment around the aft fuselage is a known unknown-a potential design and/or performance risk issue. The adverse effects of shock waves on the aft fuselage and plumeinduced flow separation are other potential risks. The development of an operational reusable launcher from the Skylon concept necessitates the judicious use of a combination of engineering methods, advanced methods based on required physics or analytical fidelity, test data, and independent assessments.
Aerodynamics of a hybrid airship
Andan, Amelda Dianne; Asrar, Waqar; Omar, Ashraf A.
2012-06-01
The objective of this paper is to present the results of a numerical study of the aerodynamic parameters of a wingless and a winged-hull airship. The total forces and moment coefficients of the airships have been computed over a range of angles. The results obtained show that addition of a wing to a conventional airship increases the lift has three times the lifting force at positive angle of attack as compared to a wingless airship whereas the drag increases in the range of 19% to 58%. The longitudinal and directional stabilities were found to be statically stable, however, both the conventional airship and the hybrid or winged airships were found to have poor rolling stability. Wingless airship has slightly higher longitudinal stability than a winged airship. The winged airship has better directional stability than the wingless airship. The wingless airship only possesses static rolling stability in the range of yaw angles of -5° to 5°. On the contrary, the winged airship initially tested does not possess rolling stability at all. Computational fluid dynamics (CFD) simulations show that modifications to the wing placement and its dihedral have strong positive effect on the rolling stability. Raising the wings to the center of gravity and introducing a dihedral angle of 5° stabilizes the rolling motion of the winged airship.
Sharp Hypervelocity Aerodynamic Research Probe
Bull, Jeffrey; Kolodziej, Paul; Rasky, Daniel J. (Technical Monitor)
1996-01-01
The objective of this flight demonstration is to deploy a slender-body hypervelocity aerodynamic research probe (SHARP) from an orbiting platform using a tether, deorbit and fly it along its aerothermal performance constraint, and recover it intact in mid-air. To accomplish this objective, two flight demonstrations are proposed. The first flight uses a blunt-body, tethered reentry experiment vehicle (TREV) to prove out tethered deployment technology for accurate entries, a complete SHARP electronics suite, and a new soft mid-air helicopter recovery technique. The second flight takes advantage of this launch and recovery capability to demonstrate revolutionary sharp body concepts for hypervelocity vehicles, enabled by new Ultra-High Temperature Ceramics (UHTCs) recently developed by Ames Research Center. Successful demonstration of sharp body hypersonic vehicle technologies could have radical impact on space flight capabilities, including: enabling global reentry cross range capability from Station, eliminating reentry communications blackout, and allowing new highly efficient launch systems incorporating air breathing propulsion and zeroth staging.
Aerodynamic Parameter Identification of a Venus Lander
Sykes, Robert A.
An analysis was conducted to identify the parameters of an aerodynamic model for a Venus lander based on experimental free-flight data. The experimental free-flight data were collected in the NASA Langley 20-ft Vertical Spin Tunnel with a 25-percent Froude-scaled model. The experimental data were classified based on the wind tunnel run type: runs where the lander model was unperturbed over the course of the run, and runs were the model was perturbed (principally in pitch, yaw, and roll) by the wind tunnel operator. The perturbations allow for data to be obtained at higher wind angles and rotation rates than those available from the unperturbed data. The model properties and equations of motion were used to determine experimental values for the aerodynamic coefficients. An aerodynamic model was selected using a priori knowledge of axisymmetric blunt entry vehicles. The least squares method was used to estimate the aerodynamic parameters. Three sets of results were obtained from the following data sets: perturbed, unperturbed, and the combination of both. The combined data set was selected for the final set of aerodynamic parameters based on the quality of the results. The identified aerodynamic parameters are consistent with that of the static wind tunnel data. Reconstructions, of experimental data not used in the parameter identification analyses, achieved similar residuals as those with data used to identify the parameters. Simulations of the experimental data, using the identified parameters, indicate that the aerodynamic model used is incapable of replicating the limit cycle oscillations with stochastic peak amplitudes observed during the test.
In vivo recording of aerodynamic force with an aerodynamic force platform
Lentink, David; Ingersoll, Rivers
2014-01-01
Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on tethered experiments with robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here we demonstrate a new aerodynamic force platform (AFP) for nonintrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is ...
Photogrammetry of a Hypersonic Inflatable Aerodynamic Decelerator
Kushner, Laura Kathryn; Littell, Justin D.; Cassell, Alan M.
2013-01-01
In 2012, two large-scale models of a Hypersonic Inflatable Aerodynamic decelerator were tested in the National Full-Scale Aerodynamic Complex at NASA Ames Research Center. One of the objectives of this test was to measure model deflections under aerodynamic loading that approximated expected flight conditions. The measurements were acquired using stereo photogrammetry. Four pairs of stereo cameras were mounted inside the NFAC test section, each imaging a particular section of the HIAD. The views were then stitched together post-test to create a surface deformation profile. The data from the photogram- metry system will largely be used for comparisons to and refinement of Fluid Structure Interaction models. This paper describes how a commercial photogrammetry system was adapted to make the measurements and presents some preliminary results.
Physics of badminton shuttlecocks. Part 1 : aerodynamics
Cohen, Caroline; Darbois Texier, Baptiste; Quéré, David; Clanet, Christophe
2011-11-01
We study experimentally shuttlecocks dynamics. In this part we show that shuttlecock trajectory is highly different from classical parabola. When one takes into account the aerodynamic drag, the flight of the shuttlecock quickly curves downwards and almost reaches a vertical asymptote. We solve the equation of motion with gravity and drag at high Reynolds number and find an analytical expression of the reach. At high velocity, this reach does not depend on velocity anymore. Even if you develop your muscles you will not manage to launch the shuttlecock very far because of the ``aerodynamic wall.'' As a consequence you can predict the length of the field. We then discuss the extend of the aerodynamic wall to other projectiles like sports balls and its importance.
Aerodynamics of magnetic levitation (MAGLEV) trains
Schetz, Joseph A.; Marchman, James F., III
1996-01-01
High-speed (500 kph) trains using magnetic forces for levitation, propulsion and control offer many advantages for the nation and a good opportunity for the aerospace community to apply 'high tech' methods to the domestic sector. One area of many that will need advanced research is the aerodynamics of such MAGLEV (Magnetic Levitation) vehicles. There are important issues with regard to wind tunnel testing and the application of CFD to these devices. This talk will deal with the aerodynamic design of MAGLEV vehicles with emphasis on wind tunnel testing. The moving track facility designed and constructed in the 6 ft. Stability Wind Tunnel at Virginia Tech will be described. Test results for a variety of MAGLEV vehicle configurations will be presented. The last topic to be discussed is a Multi-disciplinary Design approach that is being applied to MAGLEV vehicle configuration design including aerodynamics, structures, manufacturability and life-cycle cost.
Noise aspects at aerodynamic blade optimisation projects
International Nuclear Information System (INIS)
The Netherlands Energy Research Foundation (ECN) has often been involved in industrial projects, in which blade geometries are created automatic by means of numerical optimisation. Usually, these projects aim at the determination of the aerodynamic optimal wind turbine blade, i.e. the goal is to design a blade which is optimal with regard to energy yield. In other cases, blades have been designed which are optimal with regard to cost of generated energy. However, it is obvious that the wind turbine blade designs which result from these optimisations, are not necessarily optimal with regard to noise emission. In this paper an example is shown of an aerodynamic blade optimisation, using the ECN-program PVOPT. PVOPT calculates the optimal wind turbine blade geometry such that the maximum energy yield is obtained. Using the aerodynamic optimal blade design as a basis, the possibilities of noise reduction are investigated. 11 figs., 8 refs
Wind turbine aerodynamics research needs assessment
Stoddard, F. S.; Porter, B. K.
1986-01-01
A prioritized list is developed for wind turbine aerodynamic research needs and opportunities which could be used by the Department of Energy program management team in detailing the DOE Five-Year Wind Turbine Research Plan. The focus of the Assessment was the basic science of aerodynamics as applied to wind turbines, including all relevant phenomena, such as turbulence, dynamic stall, three-dimensional effects, viscosity, wake geometry, and others which influence aerodynamic understanding and design. The study was restricted to wind turbines that provide electrical energy compatible with the utility grid, and included both horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT). Also, no economic constraints were imposed on the design concepts or recommendations since the focus of the investigation was purely scientific.
Aerodynamic Jump for Long Rod Penetrators
Directory of Open Access Journals (Sweden)
Mark L. Bundy
2000-04-01
Full Text Available Aerodynamic jump for a non-spinning kinetic energy penetrator is neither a discontinuous change in the ,direction of motion at the origin of free night, nor is it the converse, i.e. a cumulativer~direc4on over a domain of infinite extent. Rather aerodynamic jump, for such a projectile, is a localised redirection of the centre of gravity motion, caused ~ the force of lift due to yaw over ther4latively short region from entry into free flight until the yaw reaches its first maximum. The primary objective of this paper is to provide answtfrs to the questions like what is aerodynamic jump, what liauses it, !lnd wh~t aspects df the flight trajectory does it refer to, or account for .
A Generic Nonlinear Aerodynamic Model for Aircraft
Grauer, Jared A.; Morelli, Eugene A.
2014-01-01
A generic model of the aerodynamic coefficients was developed using wind tunnel databases for eight different aircraft and multivariate orthogonal functions. For each database and each coefficient, models were determined using polynomials expanded about the state and control variables, and an othgonalization procedure. A predicted squared-error criterion was used to automatically select the model terms. Modeling terms picked in at least half of the analyses, which totalled 45 terms, were retained to form the generic nonlinear aerodynamic (GNA) model. Least squares was then used to estimate the model parameters and associated uncertainty that best fit the GNA model to each database. Nonlinear flight simulations were used to demonstrate that the GNA model produces accurate trim solutions, local behavior (modal frequencies and damping ratios), and global dynamic behavior (91% accurate state histories and 80% accurate aerodynamic coefficient histories) under large-amplitude excitation. This compact aerodynamics model can be used to decrease on-board memory storage requirements, quickly change conceptual aircraft models, provide smooth analytical functions for control and optimization applications, and facilitate real-time parametric system identification.
IEA joint action. Aerodynamics of wind turbines
Energy Technology Data Exchange (ETDEWEB)
Maribo Pedersen, B. [ed.
1997-12-31
In the period 1992-1997 the IEA Annex XIV `Field Rotor Aerodynamics` was carried out. Within its framework 5 institutes from 4 different countries participated in performing detailed aerodynamic measurements on full-scale wind turbines. The Annex was successfully completed and resulted in a unique database of aerodynamic measurements. The database is stored on an ECN disc (available through ftp) and on a CD-ROM. It is expected that this base will be used extensively in the development and validation of new aerodynamic models. Nevertheless at the end of IEA Annex XIV, it was recommended to perform a new IEA Annex due to the following reasons: In Annex XIV several data exchange rounds appeared to be necessary before a satisfactory result was achieved. This is due to the huge amount of data which had to be supplied, by which a thorough inspection of all data is very difficult and very time consuming; Most experimental facilities are still operational and new, very useful, measurements are expected in the near future; The definition of angle of attack and dynamic pressure in the rotating environment is less straightforward than in the wind tunnel. The conclusion from Annex XIV was that the uncertainty which results from these different definitions is still too large and more investigation in this field is required. (EG)
Efficient Global Aerodynamic Modeling from Flight Data
Morelli, Eugene A.
2012-01-01
A method for identifying global aerodynamic models from flight data in an efficient manner is explained and demonstrated. A novel experiment design technique was used to obtain dynamic flight data over a range of flight conditions with a single flight maneuver. Multivariate polynomials and polynomial splines were used with orthogonalization techniques and statistical modeling metrics to synthesize global nonlinear aerodynamic models directly and completely from flight data alone. Simulation data and flight data from a subscale twin-engine jet transport aircraft were used to demonstrate the techniques. Results showed that global multivariate nonlinear aerodynamic dependencies could be accurately identified using flight data from a single maneuver. Flight-derived global aerodynamic model structures, model parameter estimates, and associated uncertainties were provided for all six nondimensional force and moment coefficients for the test aircraft. These models were combined with a propulsion model identified from engine ground test data to produce a high-fidelity nonlinear flight simulation very efficiently. Prediction testing using a multi-axis maneuver showed that the identified global model accurately predicted aircraft responses.
Small Radial Compressors: Aerodynamic Design and Analysis
K. A. R. Ismail; Rosolen, C. V. A. G.; Benevenuto, F. J.; Lucato, D.
1998-01-01
This paper presents a computational procedure for the analysis of steady one-dimensional centrifugal compressor. The numerical model is based on the conservation principles of mass, momentum and energy, and has been utilized to predict the operational and aerodynamic characteristics of a small centrifugal compressor as well as determining the performance and geometry of compressor blades, both straight and curved.
Small Radial Compressors: Aerodynamic Design and Analysis
Directory of Open Access Journals (Sweden)
K. A. R. Ismail
1998-01-01
Full Text Available This paper presents a computational procedure for the analysis of steady one-dimensional centrifugal compressor. The numerical model is based on the conservation principles of mass, momentum and energy, and has been utilized to predict the operational and aerodynamic characteristics of a small centrifugal compressor as well as determining the performance and geometry of compressor blades, both straight and curved.
Computer Aided Aerodynamic Design of Missile Configuration
Directory of Open Access Journals (Sweden)
S. Panneerselvam
1987-10-01
Full Text Available Aerodynamic configurations of tactical missiles have to produce the required lateral force with minimum time lag to meet the required manoeuvability and response time. The present design which is mainly based on linearised potential flow involves (a indentification of critical design points, (b design of lifting components and their integration with mutual interference, (c evaluation of aerodynamic characteristics, (d checking its adequacy at otherpoints, (e optimization of parameters and selection of configuration, and (f detailed evaluation including aerodynamic pressure distribution. Iterative design process in involed because of the mutual dependance between aerodynamic charactertistics and the parameters of the configuration. though this design method is based on third level of approximation with respect to real flow, aid of computer is essential for carrying out the iterative design process and also for effective selection of configuration by analysing performance. Futuristic design requirement which demand better accuracy on design and estimation calls for sophisticated super computer based theoretical methods viz. , full Euler solution/Navier-Strokes solutions.
Aerodynamical sealing by air curtains
Frank, Daria; Linden, Paul
2015-11-01
Air curtains are artificial high-velocity plane turbulent jets which are installed in a doorway in order to reduce the heat and the mass exchange between two environments. The performance of an air curtain is assessed in terms of the sealing effectiveness E, the fraction of the exchange flow prevented by the air curtain compared to the open-door situation. The main controlling parameter for air curtain dynamics is the deflection modulus Dm representing the ratio of the momentum flux of the air curtain and the transverse forces acting on it due to the stack effect. In this talk, we examine the influence of two factors on the performance of an air curtain: the presence of an additional ventilation pathway in the room, such as a small top opening, and the effects of an opposing buoyancy force which for example arises if a downwards blowing air curtain is heated. Small-scale experiments were conducted to investigate the E (Dm) -curve of an air curtain in both situations. We present both experimental results and theoretical explanations for our observations. We also briefly illustrate how simplified models developed for air curtains can be used for more complex phenomena such as the effects of wind blowing around a model building on the ventilation rates through the openings.
In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds.
Lentink, David; Haselsteiner, Andreas F; Ingersoll, Rivers
2015-03-01
Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo. These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing.
In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds.
Lentink, David; Haselsteiner, Andreas F; Ingersoll, Rivers
2015-03-01
Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo. These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing. PMID:25589565
Wind turbines. Unsteady aerodynamics and inflow noise
Energy Technology Data Exchange (ETDEWEB)
Riget Broe, B.
2009-12-15
Aerodynamical noise from wind turbines due to atmospheric turbulence has the highest emphasis in semi-empirical models. However it is an open question whether inflow noise has a high emphasis. This illustrates the need to investigate and improve the semi-empirical model for noise due to atmospheric turbulence. Three different aerodynamical models are investigated in order to estimate the lift fluctuations due to unsteady aerodynamics. Two of these models are investigated to find the unsteady lift distribution or pressure difference as function of chordwise position on the aerofoil. An acoustic model is investigated using a model for the lift distribution as input. The two models for lift distribution are used in the acoustic model. One of the models for lift distribution is for completely anisotropic turbulence and the other for perfectly isotropic turbulence, and so is also the corresponding models for the lift fluctuations derived from the models for lift distribution. The models for lift distribution and lift are compared with pressure data which are obtained by microphones placed flush with the surface of an aerofoil. The pressure data are from two experiments in a wind tunnel, one experiment with a NACA0015 profile and a second with a NACA63415 profile. The turbulence is measured by a triple wired hotwire instrument in the experiment with a NACA0015 profile. Comparison of the aerodynamical models with data shows that the models capture the general characteristics of the measurements, but the data are hampered by background noise from the fan propellers in the wind tunnel. The measurements are in between the completely anisotropic turbulent model and the perfectly isotropic turbulent model. This indicates that the models capture the aerodynamics well. Thus the measurements suggest that the noise due to atmospheric turbulence can be described and modeled by the two models for lift distribution. It was not possible to test the acoustical model by the measurements
Freight Wing Trailer Aerodynamics Final Technical Report
Energy Technology Data Exchange (ETDEWEB)
Sean Graham
2007-10-31
Freight Wing Incorporated utilized the opportunity presented by a DOE category two Inventions and Innovations grant to commercialize and improve upon aerodynamic technology for semi-tuck trailers, capable of decreasing heavy vehicle fuel consumption, related environmental damage, and U.S. consumption of foreign oil. Major project goals included the demonstration of aerodynamic trailer technology in trucking fleet operations, and the development and testing of second generation products. A great deal of past scientific research has demonstrated that streamlining box shaped semi-trailers can significantly reduce a truck’s fuel consumption. However, significant design challenges have prevented past concepts from meeting industry needs. Freight Wing utilized a 2003 category one Inventions and Innovations grant to develop practical solutions to trailer aerodynamics. Fairings developed for the front, rear, and bottom of standard semi-trailers together demonstrated a 7% improvement to fuel economy in scientific tests conducted by the Transportation Research Center (TRC). Operational tests with major trucking fleets proved the functionality of the products, which were subsequently brought to market. This category two grant enabled Freight Wing to further develop, test and commercialize its products, resulting in greatly increased understanding and acceptance of aerodynamic trailer technology. Commercialization was stimulated by offering trucking fleets 50% cost sharing on trial implementations of Freight Wing products for testing and evaluation purposes. Over 230 fairings were implemented through the program with 35 trucking fleets including industry leaders such as Wal-Mart, Frito Lay and Whole Foods. The feedback from these testing partnerships was quite positive with product performance exceeding fleet expectations in many cases. Fleet feedback also was also valuable from a product development standpoint and assisted the design of several second generation products
Aerodynamic control with passively pitching wings
Gravish, Nick; Wood, Robert
Flapping wings may pitch passively under aerodynamic and inertial loads. Such passive pitching is observed in flapping wing insect and robot flight. The effect of passive wing pitch on the control dynamics of flapping wing flight are unexplored. Here we demonstrate in simulation and experiment the critical role wing pitching plays in yaw control of a flapping wing robot. We study yaw torque generation by a flapping wing allowed to passively rotate in the pitch axis through a rotational spring. Yaw torque is generated through alternating fast and slow upstroke and and downstroke. Yaw torque sensitively depends on both the rotational spring force law and spring stiffness, and at a critical spring stiffness a bifurcation in the yaw torque control relationship occurs. Simulation and experiment reveal the dynamics of this bifurcation and demonstrate that anomalous yaw torque from passively pitching wings is the result of aerodynamic and inertial coupling between the pitching and stroke-plane dynamics.
Vortical sources of aerodynamic force and moment
Wu, J. Z.; Wu, J. M.
1989-01-01
It is shown that the aerodynamic force and moment can be expressed in terms of vorticity distribution (and entropy variation for compressible flow) on near wake plane, or in terms of boundary vorticity flux on the body surface. Thus the vortical sources of lift and drag are clearly identified, which is the real physical basis of optimal aerodynamic design. Moreover, these sources are highly compact, hence allowing one to concentrate on key local regions of the configuration, which have dominating effect to the lift and drag. A detail knowledge of the vortical low requires measuring or calculating the vorticity and dilatation field, which is however still a challenging task. Nevertheless, this type of formulation has some unique advantages; and how to set up a well-posed problem, in particular how to establish vorticity-dilatation boundary conditions, is addressed.
Mimicking the humpback whale: An aerodynamic perspective
Aftab, S. M. A.; Razak, N. A.; Mohd Rafie, A. S.; Ahmad, K. A.
2016-07-01
This comprehensive review aims to provide a critical overview of the work on tubercles in the past decade. The humpback whale is of interest to aerodynamic/hydrodynamic researchers, as it performs manoeuvres that baffle the imagination. Researchers have attributed these capabilities to the presence of lumps, known as tubercles, on the leading edge of the flipper. Tubercles generate a unique flow control mechanism, offering the humpback exceptional manoeuverability. Experimental and numerical studies have shown that the flow pattern over the tubercle wing is quite different from conventional wings. Research on the Tubercle Leading Edge (TLE) concept has helped to clarify aerodynamic issues such as flow separation, tonal noise and dynamic stall. TLE shows increased lift by delaying and restricting spanwise separation. A summary of studies on different airfoils and reported improvement in performance is outlined. The major contributions and limitations of previous work are also reported.
Visualization of numerically simulated aerodynamic flow fields
International Nuclear Information System (INIS)
The focus of this paper is to describe the development and the application of an interactive integrated software to visualize numerically simulated aerodynamic flow fields so as to enable the practitioner of computational fluid dynamics to diagnose the numerical simulation and to elucidate essential flow physics from the simulation. The input to the software is the numerical database crunched by a supercomputer and typically consists of flow variables and computational grid geometry. This flow visualization system (FVS), written in C language is targetted at the Personal IRIS Workstations. In order to demonstrate the various visualization modules, the paper also describes the application of this software to visualize two- and three-dimensional flow fields past aerodynamic configurations which have been numerically simulated on the NEC-SXIA Supercomputer. 6 refs
Wind turbine trailing edge aerodynamic brakes
Energy Technology Data Exchange (ETDEWEB)
Migliore, P G [National Renewable Energy Lab., Golden, CO (United States); Miller, L S [Wichita State Univ., KS (United States). Dept. of Aerospace Engineering; Quandt, G A
1995-04-01
Five trailing-edge devices were investigated to determine their potential as wind-turbine aerodynamic brakes, and for power modulation and load alleviation. Several promising configurations were identified. A new device, called the spoiler-flap, appears to be the best alternative. It is a simple device that is effective at all angles of attack. It is not structurally intrusive, and it has the potential for small actuating loads. It is shown that simultaneous achievement of a low lift/drag ratio and high drag is the determinant of device effectiveness, and that these attributes must persist up to an angle of attack of 45{degree}. It is also argued that aerodynamic brakes must be designed for a wind speed of at least 45 m/s (100 mph).
Numerical Simulation Research of Loitering Munitions Aerodynamics
Institute of Scientific and Technical Information of China (English)
HE Guang-lin; JI Xiu-ling; ZHANG Tai-heng
2009-01-01
Aerodynamics of loitering munition is studied in this paper. The aerodynamic characteristics of loitering munition with non-circular body and body-airfoil-empennage combination are calculated numerically at Ma=0.4 based on multi-griddings patching technology, in the range of angle of attack -4°-10°, and the analytical results were compared with those from wind tunnel experiments, they show a good consistency. Analysis of the results showed that the normal force generated by non-circular cross-section missile increases with the angle of attack. At α≥6°, normal force achieved by missile body can take up to 10% of the total lift. Together with the lifting surface, the loitering munitions can provide a better lift to drag ratio, an improved weapon range and a good longitudinal stability.
Influence of Icing on Bridge Cable Aerodynamics
DEFF Research Database (Denmark)
Koss, Holger; Frej Henningsen, Jesper; Olsen, Idar
2013-01-01
In recent years the relevance of ice accretion for wind-induced vibration of structural bridge cables has been recognised and became a subject of research in bridge engineering. Full-scale monitoring and observation indicate that light precipitation at moderate low temperatures between zero and -5......°C may lead to large amplitude vibrations of bridge cables under wind action. For the prediction of aerodynamic instability quasi-steady models have been developed estimating the cable response magnitude based on structural properties and aerodynamic force coefficients for drag, lift and torsion...... forces of different bridge cables types. The experiments were conducted in a wind tunnel facility capable amongst others to simulate incloud icing conditions....
Integrated structural-aerodynamic design optimization
Haftka, R. T.; Kao, P. J.; Grossman, B.; Polen, D.; Sobieszczanski-Sobieski, J.
1988-01-01
This paper focuses on the processes of simultaneous aerodynamic and structural wing design as a prototype for design integration, with emphasis on the major difficulty associated with multidisciplinary design optimization processes, their enormous computational costs. Methods are presented for reducing this computational burden through the development of efficient methods for cross-sensitivity calculations and the implementation of approximate optimization procedures. Utilizing a modular sensitivity analysis approach, it is shown that the sensitivities can be computed without the expensive calculation of the derivatives of the aerodynamic influence coefficient matrix, and the derivatives of the structural flexibility matrix. The same process is used to efficiently evaluate the sensitivities of the wing divergence constraint, which should be particularly useful, not only in problems of complete integrated aircraft design, but also in aeroelastic tailoring applications.
ANALYTICAL METHODS FOR CALCULATING FAN AERODYNAMICS
Directory of Open Access Journals (Sweden)
Jan Dostal
2015-12-01
Full Text Available This paper presents results obtained between 2010 and 2014 in the field of fan aerodynamics at the Department of Composite Technology at the VZLÚ aerospace research and experimental institute in Prague – Letnany. The need for rapid and accurate methods for the preliminary design of blade machinery led to the creation of a mathematical model based on the basic laws of turbomachine aerodynamics. The mathematical model, the derivation of which is briefly described below, has been encoded in a computer programme, which enables the theoretical characteristics of a fan of the designed geometry to be determined rapidly. The validity of the mathematical model is assessed continuously by measuring model fans in the measuring unit, which was developed and manufactured specifically for this purpose. The paper also presents a comparison between measured characteristics and characteristics determined by the mathematical model as the basis for a discussion on possible causes of measured deviations and calculation deviations.
Computational Aerodynamics and Aeroacoustics for Wind Turbines
DEFF Research Database (Denmark)
Shen, Wen Zhong
To analyse the aerodynamic performance of wind turbine rotors, the main tool in use today is the 1D-Blade Element Momentum (BEM) technique combined with 2D airfoil data. Because of its simplicity, the BEM technique is employed by industry when designing new wind turbine blades. However, in order...... to obtain more detailed information of the flow structures and to determine more accurately loads and power yield of wind turbines or cluster of wind turbines, it is required to resort to more sophisticated techniques, such as Computational Fluid Dynamics (CFD). As computer resources keep on improving year...... and aero-acoustics of wind turbines. The papers are written in the period from 1997 to 2008 and numbered according to the list in page v. The work consists of two parts: an aerodynamic part based on Computational Fluid Dynamics and an aero-acoustic part based on Computational Aero Acoustics for wind...
Aerodynamics of Rotor Blades for Quadrotors
Bangura, Moses; Naldi, Roberto; Mahony, Robert
2016-01-01
In this report, we present the theory on aerodynamics of quadrotors using the well established momentum and blade element theories. From a robotics perspective, the theoretical development of the models for thrust and horizontal forces and torque (therefore power) are carried out in the body fixed frame of the quadrotor. Using momentum theory, we propose and model the existence of a horizontal force along with its associated power. Given the limitations associated with momentum theory and the inadequacy of the theory to account for the different powers represented in a proposed bond graph lead to the use of blade element theory. Using this theory, models are then developed for the different quadrotor rotor geometries and aerodynamic properties including the optimum hovering rotor used on the majority of quadrotors. Though this rotor is proven to be the most optimum rotor, we show that geometric variations are necessary for manufacturing of the blades. The geometric variations are also dictated by a desired th...
Nash equilibrium and multi criterion aerodynamic optimization
Tang, Zhili; Zhang, Lianhe
2016-06-01
Game theory and its particular Nash Equilibrium (NE) are gaining importance in solving Multi Criterion Optimization (MCO) in engineering problems over the past decade. The solution of a MCO problem can be viewed as a NE under the concept of competitive games. This paper surveyed/proposed four efficient algorithms for calculating a NE of a MCO problem. Existence and equivalence of the solution are analyzed and proved in the paper based on fixed point theorem. Specific virtual symmetric Nash game is also presented to set up an optimization strategy for single objective optimization problems. Two numerical examples are presented to verify proposed algorithms. One is mathematical functions' optimization to illustrate detailed numerical procedures of algorithms, the other is aerodynamic drag reduction of civil transport wing fuselage configuration by using virtual game. The successful application validates efficiency of algorithms in solving complex aerodynamic optimization problem.
Extended Range Guided Munition Aerodynamic Configuration Design
Institute of Scientific and Technical Information of China (English)
LEI Juan-mian; WU Jia-sheng; JU Xian-ming
2005-01-01
Based on the analysis of the flying scheme and flying style of an extended range guided munition(ERGM), the aerodynamic characteristics design standards were put forward. According to the standards, the ERGM aerodynamic configuration was designed, and the wind tunnel experiments were processed. The experimental results show that the configuration has lower drag and good static stability at unguided flying stage. Moreover, the stability, maneuverability, rudder deflection angle and balance angle of attack of the configuration are all reasonably matched at guided flying stage, and the munition with the configuration can glide with larger lift-drag ratio at little balance angle of attack. The experimental results also indicate that the canard can't conduct rolling control when 1.0 ＜ Ma ＜ 1.5, so the ERGM must take rolling flight style with certain limited rolling speed.
Compressor performance aerodynamics for the user
Gresh, Theodore
2001-01-01
Compressor Performance is a reference book and CD-ROM for compressor design engineers and compressor maintenance engineers, as well as engineering students. The book covers the full spectrum of information needed for an individual to select, operate, test and maintain axial or centrifugal compressors. It includes basic aerodynamic theory to provide the user with the ""how's"" and ""why's"" of compressor design. Maintenance engineers will especially appreciate the troubleshooting guidelines offered. Includes many example problems and reference data such as gas propert
Unsteady aerodynamics of high work turbines
Richardson, David
2009-01-01
One method aircraft engine manufactures use to minimize engine cost and weight is to reduce the number of parts. A significant reduction includes reducing the turbine blade count or combining two moderately loaded turbines into one high-work turbine. The risk of High Cycle Fatigue in these configurations is increased by the additional aerodynamic forcing generated by the high blade loading and the nozzle trailing edge shocks. A lot of research has been done into the efficiency implications of...
Vortices and Vortical Structures in Internal Aerodynamics
Institute of Scientific and Technical Information of China (English)
RudolfDvorak
1997-01-01
The paper aims at summarizing the author's recent phenomenological study of the origin,development and identification of vortical structures in internal aerodynamics.A connection between evolution of these structures and flow separation in closed curved channels is also discussed.It has been shown that in real fluids the individual vortex cores very sonn lose their identity and merge into a new dissipative structure,the properties of which still have to be defined.
The aerodynamics of the beautiful game
Bush, John W. M.
2013-01-01
We consider the aerodynamics of football, specifically, the interaction between a ball in flight and the ambient air. Doing so allows one to account for the characteristic range and trajectories of balls in flight, as well as their anomalous deflections as may be induced by striking the ball either with or without spin. The dynamics of viscous boundary layers is briefly reviewed, its critical importance on the ball trajectories highlighted. The Magnus effect responsible for the anomalous curv...
Aerodynamic Benchmarking of the Deepwind Design
DEFF Research Database (Denmark)
Bedona, Gabriele; Schmidt Paulsen, Uwe; Aagaard Madsen, Helge;
2015-01-01
The aerodynamic benchmarking for the DeepWind rotor is conducted comparing different rotor geometries and solutions and keeping the comparison as fair as possible. The objective for the benchmarking is to find the most suitable configuration in order to maximize the power production and minimize...... NACA airfoil family. (C) 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license...
Integrated aerodynamic-structural-control wing design
Rais-Rohani, M.; Haftka, R. T.; Grossman, B.; Unger, E. R.
1992-01-01
The aerodynamic-structural-control design of a forward-swept composite wing for a high subsonic transport aircraft is considered. The structural analysis is based on a finite-element method. The aerodynamic calculations are based on a vortex-lattice method, and the control calculations are based on an output feedback control. The wing is designed for minimum weight subject to structural, performance/aerodynamic and control constraints. Efficient methods are used to calculate the control-deflection and control-effectiveness sensitivities which appear as second-order derivatives in the control constraint equations. To suppress the aeroelastic divergence of the forward-swept wing, and to reduce the gross weight of the design aircraft, two separate cases are studied: (1) combined application of aeroelastic tailoring and active controls; and (2) aeroelastic tailoring alone. The results of this study indicated that, for this particular example, aeroelastic tailoring is sufficient for suppressing the aeroelastic divergence, and the use of active controls was not necessary.
The Aerodynamics of a Flying Sports Disc
Potts, Jonathan R.; Crowther, William J.
2001-11-01
The flying sports disc is a spin-stabilised axi-symmetric wing of quite remarkable design. A typical disc has an approximate elliptical cross-section and hollowed out under-side cavity, such as the Frisbee(TM) disc. An experimental study of flying disc aerodynamics, including both spinning and non-spinning tests, has been carried out in the wind tunnel. Load measurements, pressure data and flow visualisation techniques have enabled an explanation of the flow physics and provided data for free-flight simulations. A computer simulation that predicts free-flight trajectories from a given set of initial conditions was used to investigate the dynamics of a flying disc. This includes a six-degree of freedom mathematical model of disc flight mechanics, with aerodynamic coefficients derived from experimental data. A flying sports disc generates lift through forward velocity just like a conventional wing. The lift contributed by spin is insignificant and does not provide nearly enough down force to support hover. Without spin, the disc tumbles ground-ward under the influence of an unstable aerodynamic pitching moment. From a backhand throw however, spin is naturally given to the disc. The unchanged pitching moment now results in roll, due to gyroscopic precession, stabilising the disc in free-flight.
Aerodynamics of a rigid curved kite wing
Maneia, Gianmauro; Tordella, Daniela; Iovieno, Michele
2013-01-01
A preliminary numerical study on the aerodynamics of a kite wing for high altitude wind power generators is proposed. Tethered kites are a key element of an innovative wind energy technology, which aims to capture energy from the wind at higher altitudes than conventional wind towers. We present the results obtained from three-dimensional finite volume numerical simulations of the steady air flow past a three-dimensional curved rectangular kite wing (aspect ratio equal to 3.2, Reynolds number equal to 3x10^6). Two angles of incidence -- a standard incidence for the flight of a tethered airfoil (6{\\deg}) and an incidence close to the stall (18{\\deg}) -- were considered. The simulations were performed by solving the Reynolds Averaged Navier-Stokes flow model using the industrial STAR-CCM+ code. The overall aerodynamic characteristics of the kite wing were determined and compared to the aerodynamic characteristics of the flat rectangular non twisted wing with an identical aspect ratio and section (Clark Y profil...
Noise aspects at aerodynamic blade optimisation projects
Energy Technology Data Exchange (ETDEWEB)
Schepers, J.G. [Netherlands Energy Research Foundation, Petten (Netherlands)
1997-12-31
This paper shows an example of an aerodynamic blade optimisation, using the program PVOPT. PVOPT calculates the optimal wind turbine blade geometry such that the maximum energy yield is obtained. Using the aerodynamic optimal blade design as a basis, the possibilities of noise reduction are investigated. The aerodynamic optimised geometry from PVOPT is the `real` optimum (up to the latest decimal). The most important conclusion from this study is, that it is worthwhile to investigate the behaviour of the objective function (in the present case the energy yield) around the optimum: If the optimum is flat, there is a possibility to apply modifications to the optimum configuration with only a limited loss in energy yield. It is obvious that the modified configurations emits a different (and possibly lower) noise level. In the BLADOPT program (the successor of PVOPT) it will be possible to quantify the noise level and hence to assess the reduced noise emission more thoroughly. At present the most promising approaches for noise reduction are believed to be a reduction of the rotor speed (if at all possible), and a reduction of the tip angle by means of low lift profiles, or decreased twist at the outboard stations. These modifications were possible without a significant loss in energy yield. (LN)
Thermal protection mechanism of heat pipe in leading edge under hypersonic conditions
Peng Wengen; He Yurong; Wang Xinzhi; Zhu Jiaqi; Han Jiecai
2015-01-01
Sharp local structure, like the leading edge of hypersonic aircraft, confronts a severe aerodynamic heating environment at a Mach number greater than 5. To eliminate the danger of a material failure, a semi-active thermal protection system is proposed by integrating a metallic heat pipe into the structure of the leading edge. An analytical heat-balance model is established from traditional aerodynamic theories, and then thermal and mechanical characteristics of the structure are studied at Ma...
The aerodynamic and structural study of flapping wing vehicles
Zhou, Liangchen
2013-01-01
This thesis reports on the aerodynamic and structural study carried out on flapping wings and flapping vehicles. Theoretical and experimental investigation of aerodynamic forces acting on flapping wings in simple harmonic oscillations is undertaken in order to help conduct and optimize the aerodynamic and structural design of flapping wing vehicles. The research is focused on the large scale ornithopter design of similar size and configuration to a hang glider. By means of Theodorsen’s th...
THE AERODYNAMIC ANALYSIS OF THE PROFILES FOR FLYING WINGS
Directory of Open Access Journals (Sweden)
Vasile PRISACARIU
2013-01-01
Full Text Available The possibility of using an un-piloted aerial vector is determined by the aerodynamic characteristics and performances. The design for a tailless unmanned aerial vehicles starts from defining the aerial vector mission and implies o series of geometrical and aerodynamic aspects for stability. This article proposes to remark the aerodynamic characteristics of three profiles used at flying wing airship through 2D software analysis.
Aerodynamic stability of cable-stayed-suspension hybrid bridges
Institute of Scientific and Technical Information of China (English)
ZHANG Xin-jun; SUN Bing-nan
2005-01-01
Three-dimensional nonlinear aerodynamic stability analysis was applied to study the aerodynamic stability of a cable-stayed-suspension (CSS) hybrid bridge with main span of 1400 meters, and the effects of some design parameters (such as the cable sag, length of suspension portion, cable plane arrangement, subsidiary piers in side spans, the deck form, etc.) on the aerodynamic stability of the bridge are analytically investigated. The key design parameters, which significantly influence the aerodynamic stability of CSS hybrid bridges, are pointed out, and based on the wind stability the favorable structural system of CSS hybrid bridges is discussed.
Aerodynamic Modeling with Heterogeneous Data Assimilation and Uncertainty Quantification Project
National Aeronautics and Space Administration — Clear Science Corp. proposes to develop an aerodynamic modeling tool that assimilates data from different sources and facilitates uncertainty quantification. The...
Sensor Systems Collect Critical Aerodynamics Data
2010-01-01
With the support of Small Business Innovation Research (SBIR) contracts with Dryden Flight Research Center, Tao of Systems Integration Inc. developed sensors and other components that will ultimately form a first-of-its-kind, closed-loop system for detecting, measuring, and controlling aerodynamic forces and moments in flight. The Hampton, Virginia-based company commercialized three of the four planned components, which provide sensing solutions for customers such as Boeing, General Electric, and BMW and are used for applications such as improving wind turbine operation and optimizing air flow from air conditioning systems. The completed system may one day enable flexible-wing aircraft with flight capabilities like those of birds.
Aerodynamics/ACEE: Aircraft energy efficiency
1981-01-01
An overview is presented of a 10 year program managed by NASA which seeks to make possible the most efficient use of energy for aircraft propulsion and lift as well as provide a technology that can be used by U.S. manufacturers of air transports and engines. Supercritical wings, winglets, vortex drag reduction, high lift, active control, laminar flow control, and aerodynamics by computer are among the topics discussed. Wind tunnel models in flight verification of advanced technology, and the design, construction and testing of various aircraft structures are also described.
Fitting aerodynamics and propulsion into the puzzle
Johnston, Patrick J.; Whitehead, Allen H., Jr.; Chapman, Gary T.
1987-01-01
The development of an airbreathing single-stage-to-orbit vehicle, in particular the problems of aerodynamics and propulsion integration, is examined. The boundary layer transition on constant pressure surfaces at hypersonic velocities, and the effects of noise on the transition are investigated. The importance of viscosity, real-gas effects, and drag at hypersonic speeds is discussed. A propulsion system with sufficient propulsive lift to enhance the performance of the vehicle is being developed. The difficulties of engine-airframe integration are analyzed.
Insect Flight: Aerodynamics, Efficiency, and Evolution
Wang, Z. Jane
2007-11-01
Insects, like birds and fish, locomote via interactions between fluids and flapping wings. Their motion is governed by the Navier-Stokes equation coupled to moving boundaries. In this talk, I will first describe how dragonflies fly: their wing motions and the flows and forces they generate. I will then consider insects in several species and discuss three questions: 1) Is insect flight optimal? 2) How does the efficiency of flapping flight compare to classical fixed-wing flight? 3) How might aerodynamic effects have influenced the evolution of insect flight?
Energy Technology Data Exchange (ETDEWEB)
Dejean, F.
1995-12-01
The purpose of this paper is an aerodynamic simulation of the bucket root and diaphragm packing leakage flow within an impulse steam turbine HP cylinder. Calculations were undertaken in order to accurately compute both the steam temperature and steam-metal heat transfer coefficients. In order to perform this study, a compressible and turbulent finite elements Navier-Stokes code was used. Inlet and exit conditions were computed using an axisymmetrical through flow computer code and a thermal boundary layer modelling, based on classical wall function laws, was used in order to compute heat transfer coefficients. This computational study has underlined the capability of our computer codes to deal with a complex industrial problem and thermal wall boundary conditions were accurately obtained. Moreover, a complex leakage flow problem, with many recirculation zones was solves and interesting results are available. (author) 9 refs.
Aerodynamic characteristics of popcorn ash particles
Energy Technology Data Exchange (ETDEWEB)
Cherkaduvasala, V.; Murphy, D.W.; Ban, H.; Harrison, K.E.; Monroe, L.S. [University of Alabama, Birmingham, AL (United States). Dept. of Mechanical Engineering
2007-07-01
Popcorn ash particles are fragments of sintered coal fly ash masses that resemble popcorn in low apparent density. They can travel with the flow in the furnace and settle on key places such as catalyst surfaces. Computational fluid dynamics (CFD) models are often used in the design process to prevent the carryover and settling of these particles on catalysts. Particle size, density, and drag coefficient are the most important aerodynamic parameters needed in CFD modeling of particle flow. The objective of this study was to experimentally determine particle size, shape, apparent density, and drag characteristics for popcorn ash particles from a coal-fired power plant. Particle size and shape were characterized by digital photography in three orthogonal directions and by computer image analysis. Particle apparent density was determined by volume and mass measurements. Particle terminal velocities in three directions were measured in water and each particle was also weighed in air and in water. The experimental data were analyzed and models were developed for equivalent sphere and equivalent ellipsoid with apparent density and drag coefficient distributions. The method developed in this study can be used to characterize the aerodynamic properties of popcorn-like particles.
[Aerodynamic focusing of particles and heavy molecules
International Nuclear Information System (INIS)
By accelerating a gas containing suspended particles or large molecules through a converging nozzle, the suspended species may be focused and therefore used to write fine lines on a surface. Our objective was to study the limits on how narrow this focal region could be as a function of particle size. We find that, for monodisperse particles with masses mp some 3.6 x 105 times larger than the molecular mass m of the carrier gas (diameters above some 100 angstrom), there is no fundamental obstacle to directly write submicron features. However, this conclusion has been verified experimentally only with particles larger than 0.1 μm. Experimental, theoretical and numerical studies on the defocusing role of Brownian motion for very small particles or heavy molecules have shown that high resolution (purely aerodynamic) focusing is impossible with volatile molecules whose masses are typically smaller than 1000 Dalton. For these, the minimal focal diameter after optimization appears to be 5√(m/mp) times the nozzle diameter dn. But combinations of focused lasers and aerodynamic focusing appear as promising for direct writing with molecular precursors. Theoretical and numerical schemes capable of predicting the evolution of the focusing beam, including Brownian motion effects, have been developed, although further numerical work would be desirable. 11 refs
Influence of ribs on train aerodynamic performances
Institute of Scientific and Technical Information of China (English)
MIAO Xiu-juan; GAO Guang-jun
2015-01-01
The influence of ribs on the train aerodynamic performance was computed using detached eddy simulation (DES), and the transient iteration was solved by the dual-time step lower-upper symmetric Gauss-Seidel (LU-SGS) method. The results show that the ribs installed on the roof have a great effect on the train aerodynamic performance. Compared with trains without ribs, the lift force coefficient of the train with convex ribs changes from negative to positive, while the side force coefficient increases by 110% and 88%, respectively. Due to the combined effect of the lift force and side force, the overturning moment of the train with convex ribs and cutting ribs increases by 140% and 106%, respectively. There is larger negative pressure on the roof of the train without ribs than that with ribs. The ribs on the train would disturb the flow structure and contribute to the air separation, so the separation starts from the roof, while there is no air separation on the roof of the train without ribs. The ribs can also slow down the flow speed above the roof and make the air easily sucked back to the train surface. The vortices at the leeward side of the train without ribs are small and messy compared with those of the train with convex or cutting ribs.
Aerodynamic Simulation of the MEXICO Rotor
International Nuclear Information System (INIS)
CFD (Computational Fluid Dynamics) simulations are a very promising method for predicting the aerodynamic behavior of wind turbines in an inexpensive and accurate way. One of the major drawbacks of this method is the lack of validated models. As a consequence, the reliability of numerical results is often difficult to assess. The MEXICO project aimed at solving this problem by providing the project partners with high quality measurements of a 4.5 meters rotor diameter wind turbine operating under controlled conditions. The large measurement data-set allows the validation of all kind of aerodynamic models. This work summarizes our efforts for validating a CFD model based on the open source software OpenFoam. Both steady- state and time-accurate simulations have been performed with the Spalart-Allmaras turbulence model for several operating conditions. In this paper we will concentrate on axisymmetric inflow for 3 different wind speeds. The numerical results are compared with pressure distributions from several blade sections and PIV-flow data from the near wake region. In general, a reasonable agreement between measurements the and our simulations exists. Some discrepancies, which require further research, are also discussed
Aeroassist flight experiment aerodynamics and aerothermodynamics
Brewer, Edwin B.
1989-01-01
The problem is to determine the transitional flow aerodynamics and aerothermodynamics, including the base flow characteristics, of the Aeroassist Flight Experiment (AFE). The justification for the computational fluid dynamic (CFD) Application stems from MSFC's system integration responsibility for the AFE. To insure that the AFE objectives are met, MSFC must understand the limitations and uncertainties of the design data. Perhaps the only method capable of handling the complex physics of the rarefied high energy AFE trajectory is Bird's Direct Simulation Monte Carlo (DSMC) technique. The 3-D code used in this analysis is applicable only to the AFE geometry. It uses the Variable Hard Sphere (VHS) collision model and five specie chemistry model available from Langley Research Center. The code is benchmarked against the AFE flight data and used as an Aeroassisted Space Transfer Vehicle (ASTV) design tool. The code is being used to understand the AFE flow field and verify or modify existing design data. Continued application to lower altitudes is testing the capability of the Numerical Aerodynamic Simulation Facility (NASF) to handle 3-D DSMC and its practicality as an ASTV/AFE design tool.
Some Features of Aerodynamics of Cyclonic Chamber with Free Exit
Directory of Open Access Journals (Sweden)
A. N. Orekhov
2014-06-01
Full Text Available The paper cites results of an experimental research in aerodynamics of a cyclonic chamber with a free exit that has a large relative length. Distributions of aerodynamic stream characteristics depending on geometry of working volume of the cyclonic chamber are given in the paper. Calculative dependences are proposed in the paper.
Reliability and Applicability of Aerodynamic Measures in Dysphonia Assessment
Yiu, Edwin M.-L.; Yuen, Yuet-Ming; Whitehill, Tara; Winkworth, Alison
2004-01-01
Aerodynamic measures are frequently used to analyse and document pathological voices. Some normative data are available for speakers from the English-speaking population. However, no data are available yet for Chinese speakers despite the fact that they are one of the largest populations in the world. The high variability of aerodynamic measures…
Influence of anisotropic piezoelectric actuators on wing aerodynamic forces
Institute of Scientific and Technical Information of China (English)
GUAN De; LI Min; LI Wei; WANG MingChun
2008-01-01
Changing the shape of an airfoil to enhance overall aircraft performance has always been s goal of aircraft designers.Using smart material to reshape the wing can improve aerodynamic performance.The influence of anisotropic effects of piezo-electric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated.Test verification was conducted.
Exploring the Aerodynamic Drag of a Moving Cyclist
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…
Influence of anisotropic piezoelectric actuators on wing aerodynamic forces
Institute of Scientific and Technical Information of China (English)
2008-01-01
Changing the shape of an airfoil to enhance overall aircraft performance has always been a goal of aircraft designers. Using smart material to reshape the wing can improve aerodynamic performance. The influence of anisotropic effects of piezoelectric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated. Test verification was conducted.
State of the art in wind turbine aerodynamics and aeroelasticity
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver; Sørensen, Jens Nørkær; Voutsinas, S;
2006-01-01
A comprehensive review of wind turbine aeroelasticity is given. The aerodynamic part starts with the simple aerodynamic Blade Element Momentum Method and ends with giving a review of the work done applying CFD on wind turbine rotors. In between is explained some methods of intermediate complexity...
Survey of Unsteady Computational Aerodynamics for Horizontal Axis Wind Turbines
Frunzulicǎ, F.; Dumitrescu, H.; Cardoş, V.
2010-09-01
We present a short review of aerodynamic computational models for horizontal axis wind turbines (HAWT). Models presented have a various level of complexity to calculate aerodynamic loads on rotor of HAWT, starting with the simplest blade element momentum (BEM) and ending with the complex model of Navier-Stokes equations. Also, we present some computational aspects of these models.
Aerodynamic levitator furnace for measuring thermophysical properties of refractory liquids
Langstaff, D.; Gunn, M.; Greaves, G. N.; Marsing, A.; Kargl, F.
2013-12-01
The development of novel contactless aerodynamic laser heated levitation techniques is reported that enable thermophysical properties of refractory liquids to be measured in situ in the solid, liquid, and supercooled liquid state and demonstrated here for alumina. Starting with polished crystalline ruby spheres, we show how, by accurately measuring the changing radius, the known density in the solid state can be reproduced from room temperature to the melting point at 2323 K. Once molten, by coupling the floating liquid drop to acoustic oscillations via the levitating gas, the mechanical resonance and damping of the liquid can be measured precisely with high-speed high-resolution shadow cast imaging. The resonance frequency relates to the surface tension, the decay constant to the viscosity, and the ellipsoidal size and shape of the levitating drop to the density. This unique instrumentation enables these related thermophysical properties to be recorded in situ over the entire liquid and supercooled range of alumina, from the boiling point at 3240 K, until spontaneous crystallization occurs around 1860 K, almost 500 below the melting point. We believe that the utility that this unique instrumentation provides will be applicable to studying these important properties in many other high temperature liquids.
Evaluation of aerodynamic derivatives from a magnetic balance system
Raghunath, B. S.; Parker, H. M.
1972-01-01
The dynamic testing of a model in the University of Virginia cold magnetic balance wind-tunnel facility is expected to consist of measurements of the balance forces and moments, and the observation of the essentially six degree of freedom motion of the model. The aerodynamic derivatives of the model are to be evaluated from these observations. The basic feasibility of extracting aerodynamic information from the observation of a model which is executing transient, complex, multi-degree of freedom motion is demonstrated. It is considered significant that, though the problem treated here involves only linear aerodynamics, the methods used are capable of handling a very large class of aerodynamic nonlinearities. The basic considerations include the effect of noise in the data on the accuracy of the extracted information. Relationships between noise level and the accuracy of the evaluated aerodynamic derivatives are presented.
STUDY ON AERODYNAMIC CHARACTERISTICS OF VAN-BODY TRUCKS
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The aerodynamic characteristics of the van-body truck were studied by means of theoretical analysis, numerical simulation and wind tunnel experiments. The concept of critical length was presented for the van-body truck in wind tunnel experiments, the proper critical Reynolds number was found and the effects of ground parameters in ground effect simulation on the aerodynamic measurements were examined. It shows that two structure parameters, van height and the gap between the cab and the van, can obviously influence the aerodynamic characteristics, and the additional aerodynamic devices, the wind deflector and the vortex regulator in the rear, can considerably reduce the aerodynamic drag of the van-body truck. Numerical simulations provided rich information of the flow fields around the van-body trucks.
Minimum-fuel aerodynamic orbital plane change maneuvers. [for Space Shuttle Orbiters
Joosten, B. K.; Pierson, B. L.
1981-01-01
Several minimum-fuel, aerodynamically controlled, orbital plane change problems are formulated and solved as optimal control problems. A gradient projection algorithm is used to iteratively modify both the control functions, angle of attack and bank angle, and two control parameters to obtain the optimal trajectory. The atmospheric flight profile is combined with two Keplerian (two-body vacuum flight) arcs so that a complete orbit-to-orbit analysis results. The vehicle used in this investigation is the Space Transportation System Shuttle Orbiter. The effects of heat load constraint level and plane change angle are analysed.
A generalized solution of elasto-aerodynamic lubrication for aerodynamic compliant foil bearings
Institute of Scientific and Technical Information of China (English)
YU; Lie; QI; Shemiao; GENG; Haipeng
2005-01-01
Although aerodynamic compliant foil bearings are successfully applied in a number of turbo-machineries, theoretical researches on the modeling, performance prediction of compliant foil bearings and the dynamic analysis of the related rotor system seem still far behind the experimental investigation because of structural complexity of the foil bearings. A generalized solution of the elasto-aerodynamic lubrication is presented in this paper by introducing both static and dynamic deformations of foils and solving gas-lubricated Reynolds equations with deformation equations simultaneously. The solution can be used for the calculation of dynamic stiffness and damping, as well as the prediction of static performances of foil bearings. Systematical theories and methods are also presented for the purpose of the prediction of dynamic behavior of a rotor system equipped with foil bearings.
Aerodynamic Modelling and Optimization of Axial Fans
DEFF Research Database (Denmark)
Sørensen, Dan Nørtoft
of fan efficiency in a design interval of flow rates,thus designinga fan which operates well over a range of different flow conditions.The optimization scheme was used to investigate the dependence ofmaximum efficiency on1: the number of blades,2: the width of the design interval and3: the hub radius.......The degree of freedom in the choice of design variables andconstraints, combined with the design interval concept, providesa valuable design-tool for axial fans.To further investigate the use of design optimization, a modelfor the vortex shedding noise from the trailing edge of the bladeshas been......A numerically efficient mathematical model for the aerodynamics oflow speed axial fans of the arbitrary vortex flow type has been developed.The model is based on a blade-element principle, whereby therotor is divided into a number of annular streamtubes.For each of these streamtubes relations...
Wind Turbines: Unsteady Aerodynamics and Inflow Noise
DEFF Research Database (Denmark)
Broe, Brian Riget
(Sears, W. R.: 1941; and Graham, J. M. R.: 1970). An acoustic model is investigated using a model for the lift distribution as input (Amiet, R. K.: 1975, Acoustic radiation from an airfoil in a turbulent stream). The two models for lift distribution are used in the acoustic model. One of the models...... in order to estimate the lift fluctuations due to unsteady aerodynamics (Sears, W. R.: 1941, Some aspects of non-stationary airfoil theory and its practical application; Goldstein, M. E. and Atassi, H. M.: 1976, A complete second-order theory for the unsteady flow about an airfoil due to a periodic gust......; and Graham, J. M. R.: 1970, Lifting surface theory for the problem of an arbitrarily yawed sinusoidal gust incident on a thin aerofoil in incompressible flow). Two of these models are investigated to find the unsteady lift distribution or pressure difference as function of chordwise position on the aerofoil...
Multiprocessing on supercomputers for computational aerodynamics
Yarrow, Maurice; Mehta, Unmeel B.
1991-01-01
Little use is made of multiple processors available on current supercomputers (computers with a theoretical peak performance capability equal to 100 MFLOPS or more) to improve turnaround time in computational aerodynamics. The productivity of a computer user is directly related to this turnaround time. In a time-sharing environment, such improvement in this speed is achieved when multiple processors are used efficiently to execute an algorithm. The concept of multiple instructions and multiple data (MIMD) is applied through multitasking via a strategy that requires relatively minor modifications to an existing code for a single processor. This approach maps the available memory to multiple processors, exploiting the C-Fortran-Unix interface. The existing code is mapped without the need for developing a new algorithm. The procedure for building a code utilizing this approach is automated with the Unix stream editor.
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.
Prediction of aerodynamic performance for MEXICO rotor
DEFF Research Database (Denmark)
Hong, Zedong; Yang, Hua; Xu, Haoran;
2013-01-01
. The boundaries of fan-shaped both sides are defined as rotationally periodic connection, and the freeze rotor model is applied at the interface of the rotating and stationary domains, which means the relative position of rotating and stationary domains is fixed when calculating the flow field. Speed no......The aerodynamic performance of the MEXICO (Model EXperiments In Controlled cOnditions) rotor at five tunnel wind speeds is predicted by making use of BEM and CFD methods, respectively, using commercial MATLAB and CFD software. Due to the pressure differences on both sides of the blade, the tip-flow...... will produce secondary flow along the blade, consecutively resulting in decreases of torque. To overcome the above-mentioned issue, a variety of tip-correction models are developed, while most models overestimate the axial and tangential forces. To optimize accuracy, a new correction model summarized from CFD...
Aerodynamics of a golf ball with grooves
Kim, Jooha; Son, Kwangmin; Choi, Haecheon
2009-11-01
It is well known that the drag on a dimpled ball is much lower than that on smooth ball. Choi et al. (Phys. Fluids, 2006) showed that turbulence is generated through the instability of shear layer separating from the edge of dimples and delays flow separation. Based on this mechanism, we devise a new golf ball with grooves on the surface but without any dimples. To investigate the aerodynamic performance of this new golf ball, an experiment is conducted in a wind tunnel at the Reynolds numbers of 0.5 x10^5 - 2.7 x10^5 and the spin ratios (ratio of surface velocity to the free-stream velocity) of α=0 - 0.5, which are within the ranges of real golf-ball velocity and spin rate. We measure the drag and lift forces on the grooved ball and compare them with those of smooth ball. At zero spin, the drag coefficient on the grooved ball shows a rapid fall-off at a critical Reynolds number and maintains a minimum value which is lower by 50% than that on smooth ball. At non-zero α, the drag coefficient on the grooved ball increases with increasing α, but is still lower by 40% than that on smooth ball. The lift coefficient on the grooved ball increases with increasing α, and is 100% larger than that on smooth ball. The aerodynamic characteristics of grooved ball is in general quite similar to that of dimpled ball. Some more details will be discussed in the presentation.
Aerodynamic Optimization of Micro Aerial Vehicle
Directory of Open Access Journals (Sweden)
Siew Ping Yeong
2016-01-01
Full Text Available Computational fluid dynamics (CFD study was done on the propeller design of a micro aerial vehicle (quadrotor-typed to optimize its aerodynamic performance via Shear Stress Transport K-Omega (SST k-ω turbulence model. The quadrotor model used was WL-V303 Seeker. The design process started with airfoils selection and followed by the evaluation of drone model in hovering and cruising conditions. To sustain a 400g payload, by Momentum Theory an ideal thrust of 5.4 N should be generated by each rotor of the quadrotor and this resulted in an induced velocity of 7.4 m/s on the propeller during hovering phase, equivalent to Reynolds number of 10403 at 75% of the propeller blade radius. There were 6 propellers investigated at this Reynolds number. Sokolov airfoil which produced the largest lift-to-drag ratio was selected for full drone installation to be compared with the original model (benchmark. The CFD results showed that the Sokolov propeller generated 0.76 N of thrust more than the benchmark propeller at 7750 rpm. Despite generating higher thrust, higher drag was also experienced by the drone installed with Sokolov propellers. This resulted in lower lift-to-drag ratio than the benchmark propellers. It was also discovered that the aerodynamic performance of the drone could be further improved by changing the rotating direction of each rotor. Without making changes on the structural design, the drone performance increased by 39.58% in terms of lift-to-drag ratio by using this method.
Dynamic stability of an aerodynamically efficient motorcycle
Sharma, Amrit; Limebeer, David J. N.
2012-08-01
Motorcycles exhibit two potentially dangerous oscillatory modes known as 'wobble' and 'weave'. The former is reminiscent of supermarket castor shimmy, while the latter is a low frequency 'fish-tailing' motion that involves a combination of rolling, yawing, steering and side-slipping motions. These unwanted dynamic features, which can occur when two-wheeled vehicles are operated at speed, have been studied extensively. The aim of this paper is to use mathematical analysis to identify important stability trends in the on-going design of a novel aerodynamically efficient motorcycle known as the ECOSSE Spirit ES1. A mathematical model of the ES1 is developed using a multi-body dynamics software package called VehicleSim [Anon, VehicleSim Lisp Reference Manual Version 1.0, Mechanical Simulation Corporation, 2008. Available at http://www.carsim.com]. This high-fidelity motorcycle model includes realistic tyre-road contact geometry, a comprehensive tyre model, tyre relaxation and a flexible frame. A parameter set representative of a modern high-performance machine and rider is used. Local stability is investigated via the eigenvalues of the linearised models that are associated with equilibrium points of interest. A comprehensive study of the effects of frame flexibilities, acceleration, aerodynamics and tyre variations is presented, and an optimal passive steering compensator is derived. It is shown that the traditional steering damper cannot be used to stabilise the ES1 over its entire operating speed range. A simple passive compensator, involving an inerter is proposed. Flexibility can be introduced deliberately into various chassis components to change the stability characteristics of the vehicle; the implications of this idea are studied.
Fourier analysis of the aerodynamic behavior of cup anemometers
International Nuclear Information System (INIS)
The calibration results (the transfer function) of an anemometer equipped with several cup rotors were analyzed and correlated with the aerodynamic forces measured on the isolated cups in a wind tunnel. The correlation was based on a Fourier analysis of the normal-to-the-cup aerodynamic force. Three different cup shapes were studied: typical conical cups, elliptical cups and porous cups (conical-truncated shape). Results indicated a good correlation between the anemometer factor, K, and the ratio between the first two coefficients in the Fourier series decomposition of the normal-to-the-cup aerodynamic force. (paper)
Experimental Investigation of Aerodynamic Instability of Iced Bridge Cable Sections
DEFF Research Database (Denmark)
Koss, Holger; Lund, Mia Schou Møller
2013-01-01
The accretion of ice on structural bridge cables changes the aerodynamic conditions of the surface and influences hence the acting wind load process. Full-scale monitoring indicates that light precipitation at moderate low temperatures between zero and -5°C may lead to large amplitude vibrations...... of bridge cables under wind action. This paper describes the experimental simulation of ice accretion on a real bridge cable sheet HDPE tube segment (diameter 160mm) and its effect on the aerodynamic load. Furthermore, aerodynamic instability will be estimated with quasi-steady theory using the determined...
Lin, Qiao; Jiang, Fukang; Wang, Xuan-Qi; Xu, Yong; Han, Zhigang; Tai, Yu-Chong; Lew, James; Ho, Chih-Ming
2004-01-01
MEMS thermal shear-stress sensors exploit heat-transfer effects to measure the shear stress exerted by an air flow on its solid boundary, and have promising applications in aerodynamic control. Classical theory for conventional, macroscale thermal shear-stress sensors states that the rate of heat removed by the flow from the sensor is proportional to the 1/3-power of the shear stress. However, we have observed that this theory is inconsistent with experimental data from MEMS sensors. This pap...
Investigation into the aerodynamic processes of air treatment using a plate-type biofilter.
Baltrėnas, Pranas; Kleiza, Jonas; Idzelis, Raimondas Leopoldas
2016-01-01
The research conducted has involved a laboratory stand of a plate-type air treatment biofilter with a capillary system for humidifying packing material composed of polymer plates vertically arranged next to each other and producing a capillary effect of humidification. The pattern of arranging the plates has sufficiently large spaces (6 mm), and therefore the use of the plate-type structure decreases the aerodynamic resistance of the device. Slightly pressed slabs attached on both sides of the plates are made of heat-treated wood fibre, to increase the longevity of which, wood waste has been heat-treated in the steam explosion reactor under the pressure of 32 bars and a temperature of 235 °C. This is the method for changing the molecular structure of wood, which stops the decay of wood fibre in a humid environment and thus increases the life span of biofilter plates. The research performed has disclosed that, under the application of the above introduced structure of the biofilter, the aerodynamic resistance of the biofilter reaches 1 ÷ 5 Pa when the rate of the air flow passing through the device makes 0.08 m/s. For evaluating the reliability of the obtained results, the theoretical model has been applied.
High-Fidelity Aerodynamic Design with Transition Prediction Project
National Aeronautics and Space Administration — To enhance aerodynamic design capabilities, Desktop Aeronautics proposes to combine a new sweep/taper integrated-boundary-layer (IBL) code that includes transition...
Space Launch System Ascent Static Aerodynamic Database Development
Pinier, Jeremy T.; Bennett, David W.; Blevins, John A.; Erickson, Gary E.; Favaregh, Noah M.; Houlden, Heather P.; Tomek, William G.
2014-01-01
This paper describes the wind tunnel testing work and data analysis required to characterize the static aerodynamic environment of NASA's Space Launch System (SLS) ascent portion of flight. Scaled models of the SLS have been tested in transonic and supersonic wind tunnels to gather the high fidelity data that is used to build aerodynamic databases. A detailed description of the wind tunnel test that was conducted to produce the latest version of the database is presented, and a representative set of aerodynamic data is shown. The wind tunnel data quality remains very high, however some concerns with wall interference effects through transonic Mach numbers are also discussed. Post-processing and analysis of the wind tunnel dataset are crucial for the development of a formal ascent aerodynamics database.
Theoretical and applied aerodynamics and related numerical methods
Chattot, J J
2015-01-01
This book covers classical and modern aerodynamics, theories and related numerical methods, for senior and first-year graduate engineering students, including: -The classical potential (incompressible) flow theories for low speed aerodynamics of thin airfoils and high and low aspect ratio wings. - The linearized theories for compressible subsonic and supersonic aerodynamics. - The nonlinear transonic small disturbance potential flow theory, including supercritical wing sections, the extended transonic area rule with lift effect, transonic lifting line and swept or oblique wings to minimize wave drag. Unsteady flow is also briefly discussed. Numerical simulations based on relaxation mixed-finite difference methods are presented and explained. - Boundary layer theory for all Mach number regimes and viscous/inviscid interaction procedures used in practical aerodynamics calculations. There are also four chapters covering special topics, including wind turbines and propellers, airplane design, flow analogies and h...
Mead Crater, Venus - Aerodynamic roughness of wind streaks
Williams, K. K.; Greeley, R.
1997-03-01
Radar backscatter images of Venus returned by the Magellan spacecraft revealed many aeolian features on the planet's surface. While much work has focused on terrestrial wind streaks, the harsh environment of Venus limits direct measurement of surface properties, such as aerodynamic roughness, that affect aeolian features on that planet. However, a correlation between radar backscatter and aerodynamic roughness (Z0) for the S-band radar system on Magellan can be used to study the aerodynamic roughnesses of areas in which Venusian wind streaks occur. The aerodynamic roughness of areas with both radar-bright and radar-dark wind streaks near Mead crater are calculated and compared to z0 values measured on Earth in order to compare the surface of Venus with known terrestrial surface textures.
The Aerodynamics of Heavy Vehicles III : Trucks, Buses and Trains
Orellano, Alexander
2016-01-01
This volume contains papers presented at the International conference “The Aerodynamics of Heavy Vehicles III: Trucks, Buses and Trains” held in Potsdam, Germany, September 12-17, 2010 by Engineering Conferences International (ECI). Leading scientists and engineers from industry, universities and research laboratories, including truck and high-speed train manufacturers and operators were brought together to discuss computer simulation and experimental techniques to be applied for the design of more efficient trucks, buses and high-speed trains in the future. This conference was the third in the series after Monterey-Pacific Groove in 2002 and Lake Tahoe in 2007. The presentations address different aspects of train aerodynamics (cross wind effects, underbody flow, tunnel aerodynamics and aeroacoustics, experimental techniques), truck aerodynamics (drag reduction, flow control, experimental and computational techniques) as well as computational fluid dynamics and bluff body, wake and jet flows.
High-Fidelity Aerodynamic Design with Transition Prediction Project
National Aeronautics and Space Administration — To enhance aerodynamic design capabilities, Desktop Aeronautics proposes to significantly improve upon the integration (performed in Phase 1) of a new sweep/taper...
Influences of surface temperature on a low camber airfoil aerodynamic performances
Directory of Open Access Journals (Sweden)
Valeriu DRAGAN
2016-03-01
Full Text Available The current note refers to the comparison between a NACA 2510 airfoil with adiabatic walls and the same airfoil with heated patches. Both suction and pressure sides were divided into two regions covering the leading edge (L.E. and trailing edge (T.E.. A RANS method sensitivity test has been performed in the preliminary stage while for the extended 3D cases a DES-SST approach was used. Results indicate that surface temperature distribution influences the aerodynamics of the airfoil, in particular the viscous drag component but also the lift of the airfoil. Moreover, the influence depends not only on the surface temperature but also on the positioning of the heated surfaces, particularly in the case of pressure lift and drag. Further work will be needed to optimize the temperature distribution for airfoil with higher camber.
Aerodynamic Reconstruction Applied to Parachute Test Vehicle Flight Data Analysis
Cassady, Leonard D.; Ray, Eric S.; Truong, Tuan H.
2013-01-01
The aerodynamics, both static and dynamic, of a test vehicle are critical to determining the performance of the parachute cluster in a drop test and for conducting a successful test. The Capsule Parachute Assembly System (CPAS) project is conducting tests of NASA's Orion Multi-Purpose Crew Vehicle (MPCV) parachutes at the Army Yuma Proving Ground utilizing the Parachute Test Vehicle (PTV). The PTV shape is based on the MPCV, but the height has been reduced in order to fit within the C-17 aircraft for extraction. Therefore, the aerodynamics of the PTV are similar, but not the same as, the MPCV. A small series of wind tunnel tests and computational fluid dynamics cases were run to modify the MPCV aerodynamic database for the PTV, but aerodynamic reconstruction of the flights has proven an effective source for further improvements to the database. The acceleration and rotational rates measured during free flight, before parachute inflation but during deployment, were used to con rm vehicle static aerodynamics. A multibody simulation is utilized to reconstruct the parachute portions of the flight. Aerodynamic or parachute parameters are adjusted in the simulation until the prediction reasonably matches the flight trajectory. Knowledge of the static aerodynamics is critical in the CPAS project because the parachute riser load measurements are scaled based on forebody drag. PTV dynamic damping is critical because the vehicle has no reaction control system to maintain attitude - the vehicle dynamics must be understood and modeled correctly before flight. It will be shown here that aerodynamic reconstruction has successfully contributed to the CPAS project.
Aerodynamic structures and processes in rotationally augmented flow fields
DEFF Research Database (Denmark)
Schreck, S.J.; Sørensen, Niels N.; Robinson, M.C.
2007-01-01
Rotational augmentation of horizontal axis wind turbine blade aerodynamics currently remains incompletely characterized and understood. To address this, the present study concurrently analysed experimental measurements and computational predictions, both of which were unique and of high quality...... to reliably identify and track pertinent features in the rotating blade boundary layer topology as they evolved in response to varying wind speed. Subsequently, boundary layer state was linked to above-surface flow field structure and used to deduce mechanisms; underlying augmented aerodynamic force...
Improved Aerodynamic Analysis for Hybrid Wing Body Conceptual Design Optimization
Gern, Frank H.
2012-01-01
This paper provides an overview of ongoing efforts to develop, evaluate, and validate different tools for improved aerodynamic modeling and systems analysis of Hybrid Wing Body (HWB) aircraft configurations. Results are being presented for the evaluation of different aerodynamic tools including panel methods, enhanced panel methods with viscous drag prediction, and computational fluid dynamics. Emphasis is placed on proper prediction of aerodynamic loads for structural sizing as well as viscous drag prediction to develop drag polars for HWB conceptual design optimization. Data from transonic wind tunnel tests at the Arnold Engineering Development Center s 16-Foot Transonic Tunnel was used as a reference data set in order to evaluate the accuracy of the aerodynamic tools. Triangularized surface data and Vehicle Sketch Pad (VSP) models of an X-48B 2% scale wind tunnel model were used to generate input and model files for the different analysis tools. In support of ongoing HWB scaling studies within the NASA Environmentally Responsible Aviation (ERA) program, an improved finite element based structural analysis and weight estimation tool for HWB center bodies is currently under development. Aerodynamic results from these analyses are used to provide additional aerodynamic validation data.
Aerodynamic Performances of Corrugated Dragonfly Wings at Low Reynolds Numbers
Tamai, Masatoshi; He, Guowei; Hu, Hui
2006-11-01
The cross-sections of dragonfly wings have well-defined corrugated configurations, which seem to be not very suitable for flight according to traditional airfoil design principles. However, previous studies have led to surprising conclusions of that corrugated dragonfly wings would have better aerodynamic performances compared with traditional technical airfoils in the low Reynolds number regime where dragonflies usually fly. Unlike most of the previous studies of either measuring total aerodynamics forces (lift and drag) or conducting qualitative flow visualization, a series of wind tunnel experiments will be conducted in the present study to investigate the aerodynamic performances of corrugated dragonfly wings at low Reynolds numbers quantitatively. In addition to aerodynamics force measurements, detailed Particle Image Velocimetry (PIV) measurements will be conducted to quantify of the flow field around a two-dimensional corrugated dragonfly wing model to elucidate the fundamental physics associated with the flight features and aerodynamic performances of corrugated dragonfly wings. The aerodynamic performances of the dragonfly wing model will be compared with those of a simple flat plate and a NASA low-speed airfoil at low Reynolds numbers.
The aerodynamic signature of running spiders.
Directory of Open Access Journals (Sweden)
Jérôme Casas
Full Text Available Many predators display two foraging modes, an ambush strategy and a cruising mode. These foraging strategies have been classically studied in energetic, biomechanical and ecological terms, without considering the role of signals produced by predators and perceived by prey. Wolf spiders are a typical example; they hunt in leaf litter either using an ambush strategy or by moving at high speed, taking over unwary prey. Air flow upstream of running spiders is a source of information for escaping prey, such as crickets and cockroaches. However, air displacement by running arthropods has not been previously examined. Here we show, using digital particle image velocimetry, that running spiders are highly conspicuous aerodynamically, due to substantial air displacement detectable up to several centimetres in front of them. This study explains the bimodal distribution of spider's foraging modes in terms of sensory ecology and is consistent with the escape distances and speeds of cricket prey. These findings may be relevant to the large and diverse array of arthropod prey-predator interactions in leaf litter.
Kinematics and Aerodynamics of Backward Flying Dragonflies
Bode-Oke, Ayodeji; Zeyghami, Samane; Dong, Haibo
2015-11-01
Highly maneuverable insects such as dragonflies have a wide range of flight capabilities; precise hovering, fast body reorientations, sideways flight and backward takeoff are only a few to mention. In this research, we closely examined the kinematics as well as aerodynamics of backward takeoff in dragonflies and compared them to those of forward takeoff. High speed videography and accurate 3D surface reconstruction techniques were employed to extract details of the wing and body motions as well as deformations during both flight modes. While the velocities of both forward and backward flights were similar, the body orientation as well as the wing kinematics showed large differences. Our results indicate that by tilting the stroke plane angle of the wings as well as changing the orientation of the body relative to the flight path, dragonflies control the direction of the flight like a helicopter. In addition, our detailed analysis of the flow in these flights shows important differences in the wake capture phenomena among these flight modes. This work is supported by NSF CBET-1313217.
Measured Aerodynamic Interaction of Two Tiltrotors
Yamauchi, Gloria K.; Wadcock, Alan J.; Derby, Michael R.
2003-01-01
The aerodynamic interaction of two model tilrotors in helicopter-mode formation flight is investigated. Three cenarios representing tandem level flight, tandem operations near the ground, and a single tiltrotor operating above thc ground for varying winds are examined. The effect of aircraft separation distance on the thrust and rolling moment of the trailing aircraft with and without the presence of a ground plane are quantified. Without a ground plane, the downwind aircraft experiences a peak rolling moment when the right (left) roto- of the upwind aircraft is laterally aligned with the left (right) rotor of the downwind aircraft. The presence of the ground plane causes the peak rolling moment on the downwind aircraft to occur when the upwind aircraft is further outboard of the downwind aircraft. Ground plane surface flow visualization images obtained using rufts and oil are used to understand mutual interaction between the two aircraft. These data provide guidance in determining tiltrotor flight formations which minimize disturbance to the trailing aircraft.
Aerodynamically generated noise by lightning arrester
Directory of Open Access Journals (Sweden)
Váchová J.
2007-10-01
Full Text Available This paper presents the general solution of aerodynamically generated noise by lightning arrester. Governing equations are presented in form of Lighthill acoustic analogy, as embodied in the Ffowcs Williams-Hawkings (FW-H equation. This equation is based on conservation laws of fluid mechanics rather than on the wave equation. Thus, the FW-H equation is valid even if the integration surface is in nonlinear region. That’s why the FWH method is superior in aeroacoustics. The FW-H method is implemented in program Fluent and the numerical solution is acquired by Fluent code.The general solution of acoustic signal generated by lightning arrester is shown and the results in form of acoustic pressure and frequency spectrum are presented. The verification of accuracy was made by evaluation of Strouhal number. A comparison of Strouhal number for circumfluence of a cylinder and the lightning arrester was done, because the experimental data for cylinder case are known and these solids are supposed to be respectively in shape relation.
Computational aerodynamics and aeroacoustics for wind turbines
Energy Technology Data Exchange (ETDEWEB)
Shen, W.Z.
2009-10-15
The present thesis consists of 19 selected papers dealing with the development and use of CFD methods for studying the aerodynamics and aero-acoustics of wind turbines. The papers are written in the period from 1997 to 2008 and numbered according to the list in page v. The work consists of two parts: an aerodynamic part based on Computational Fluid Dynamics and an aero-acoustic part based on Computational Aero Acoustics for wind turbines. The main objective of the research was to develop new computational tools and techniques for analysing flows about wind turbines. A few papers deal with applications of Blade Element Momentum (BEM) theory to wind turbines. In most cases the incompressible Navier-Stokes equations in primitive variables (velocity-pressure formulation) are employed as the basic governing equations. However, since fluid mechanical problems essentially are governed by vortex dynamics, it is sometimes advantageous to use the concept of vorticity (defined as the curl of velocity). In vorticity form the Navier-Stokes equations may be formulated in different ways, using a vorticity-stream function formulation, a vorticity-velocity formulation or a vorticity-potential-stream function formulation. In [1] - [3] two different vorticity formulations were developed for 2D and 3D wind turbine flows. In [4] and [5] numerical techniques for avoiding pressure oscillations were developed when solving the velocity-pressure coupling system in the in-house EllipSys2D/3D code. In [6] - [8] different actuator disc techniques combined with CFD are presented. This includes actuator disc, actuator line and actuator surface techniques, which were developed to simulate flows past one or more wind turbines. In [9] and [10] a tip loss correction method that improves the conventional models was developed for use in combination with BEM or actuator/Navier-Stokes computations. A simple and efficient technique for determining the angle of attack for flow past a wind turbine rotor
Rudolf Hermann, wind tunnels and aerodynamics
Lundquist, Charles A.; Coleman, Anne M.
2008-04-01
Rudolf Hermann was born on December 15, 1904 in Leipzig, Germany. He studied at the University of Leipzig and at the Aachen Institute of Technology. His involvement with wind tunnels began in 1934 when Professor Carl Wieselsberger engaged him to work at Aachen on the development of a supersonic wind tunnel. On January 6, 1936, Dr. Wernher von Braun visited Dr. Hermann to arrange for use of the Aachen supersonic wind tunnel for Army problems. On April 1, 1937, Dr. Hermann became Director of the Supersonic Wind Tunnel at the Army installation at Peenemunde. Results from the Aachen and Peenemunde wind tunnels were crucial in achieving aerodynamic stability for the A-4 rocket, later designated as the V-2. Plans to build a Mach 10 'hypersonic' wind tunnel facility at Kochel were accelerated after the Allied air raid on Peenemunde on August 17, 1943. Dr. Hermann was director of the new facility. Ignoring destruction orders from Hitler as WWII approached an end in Europe, Dr. Hermann and his associates hid documents and preserved wind tunnel components that were acquired by the advancing American forces. Dr. Hermann became a consultant to the Air Force at its Wright Field in November 1945. In 1951, he was named professor of Aeronautical Engineering at the University of Minnesota. In 1962, Dr. Hermann became the first Director of the Research Institute at the University of Alabama in Huntsville (UAH), a position he held until he retired in 1970.
IEA joint action. Aerodynamics of wind turbines
Energy Technology Data Exchange (ETDEWEB)
Maribo Pedersen, B. [ed.
1997-08-01
The advances to be made in aerodynamic prediction requires a deeper understanding of the physical processes occurring at the blades, and in the wake, of a wind turbine. This can only come from a continuing process of experimental observation and theoretical analysis. The present symposium presents the opportunity to do this by exchange of data from experiments and simulations, and by discussion of new or modified wake theories. The symposium will consists of a number of presentations by invited speakers and conclude with a summary of the talks and a round-the-table technical discussion. The talks offer the change to present behaviour from full-scale and laboratory experiments that are not explained by existing prediction codes. In addition, presentations are welcome on new modelling techniques or formulations that could make existing codes more accurate, less computationally intensive and easier to use. This symposium is intended to provide a starting point for the formulation of advanced rotor performance methods, which will improve the accuracy of load and performance prediction codes useful to the wind turbine industry. (au)
Unsteady aerodynamic modelling of wind turbines
Energy Technology Data Exchange (ETDEWEB)
Coton, F.N.; Galbraith, R.A. [Univ. og Glasgow, Dept. of Aerospace Engineering, Glasgow (United Kingdom)
1997-08-01
The following current and future work is discussed: Collaborative wind tunnel based PIV project to study wind turbine wake structures in head-on and yawed flow. Prescribed wake model has been embedded in a source panel representation of the wind tunnel walls to allow comparison with experiment; Modelling of tower shadow using high resolution but efficient vortex model in tower shadow domain; Extension of model to yawing flow; Upgrading and tuning of unsteady aerodynamic model for low speed, thick airfoil flows. Glasgow has a considerable collection of low speed dynamic stall data. Currently, the Leishman - Beddoes model is not ideally suited to such flows. For example: Range of stall onset criteria used for dynamic stall prediction including Beddoes. Wide variation of stall onset prediction. Beddoes representation was developed primarily with reference to compressible flows. Analyses of low speed data from Glasgow indicate deficiencies in the current model; Predicted versus measured response during ramp down motion. Modification of the Beddoes representation is required to obtain a fit with the measured data. (EG)
McVetta, Ashlie B.; Giel, Paul W.; Welch, Gerard E.
2014-01-01
Aerodynamic measurements showing the effects of large incidence angle variations on an HPT turbine blade set are presented. Measurements were made in NASA's Transonic Turbine Blade Cascade Facility which has been used in previous studies to acquire detailed aerodynamic and heat transfer measurements for CFD code validation. The current study supports the development of variable-speed power turbine (VSPT) speed-change technology for the NASA Large Civil Tilt Rotor (LCTR) vehicle. In order to maintain acceptable main rotor propulsive efficiency, the VSPT operates over a nearly 50 percent speed range from takeoff to altitude cruise. This results in 50 deg or more variations in VSPT blade incidence angles. The cascade facility has the ability to operate over a wide range of Reynolds numbers and Mach numbers, but had to be modified in order to accommodate the negative incidence angle variation required by the LCTR VSPT operation. Using existing blade geometry with previously acquired aerodynamic data, the tunnel was re-baselined and the new incidence angle range was exercised. Midspan exit total pressure and flow angle measurements were obtained at seven inlet flow angles. For each inlet angle, data were obtained at five flow conditions with inlet Reynolds numbers varying from 6.83×10 (exp 5) to 0.85×10(exp 5) and two isentropic exit Mach numbers of 0.74 and 0.34. The midspan flowfield measurements were acquired using a three-hole pneumatic probe located in a survey plane 8.6 percent axial chord downstream of the blade trailing edge plane and covering three blade passages. Blade and endwall static pressure distributions were also acquired for each flow condition.
Aerodynamic Investigation of Incidence Angle Effects in a Large Scale Transonic Turbine Cascade
McVetta, Ashlie B.; Giel, Paul W.; Welch, Gerard E.
2013-01-01
Aerodynamic measurements showing the effects of large incidence angle variations on an HPT turbine blade set are presented. Measurements were made in NASA's Transonic Turbine Blade Cascade Facility which has been used in previous studies to acquire detailed aerodynamic and heat transfer measurements for CFD code validation. The current study supports the development of variable-speed power turbine (VSPT) speed-change technology for the NASA Large Civil Tilt Rotor (LCTR) vehicle. In order to maintain acceptable main rotor propulsive efficiency, the VSPT operates over a nearly 50 percent speed range from takeoff to altitude cruise. This results in 50deg or more variations in VSPT blade incidence angles. The cascade facility has the ability to operate over a wide range of Reynolds numbers and Mach numbers, but had to be modified in order to accommodate the negative incidence angle variation required by the LCTR VSPT operation. Using existing blade geometry with previously acquired aerodynamic data, the tunnel was re-baselined and the new incidence angle range was exercised. Midspan exit total pressure and flow angle measurements were obtained at seven inlet flow angles. For each inlet angle, data were obtained at five flow conditions with inlet Reynolds numbers varying from 6.83×10(exp 5) to 0.85×10(exp 5) and two isentropic exit Mach numbers of 0.74 and 0.34. The midspan flowfield measurements were acquired using a three-hole pneumatic probe located in a survey plane 8.6 percent axial chord downstream of the blade trailing edge plane and covering three blade passages. Blade and endwall static pressure distributions were also acquired for each flow condition.
Aerodynamics support of research instrument development
Miller, L. Scott
1990-01-01
A new velocimetry system is currently being developed at NASA LaRC. The device, known as a Doppler global velocimeter (DGV), can record three velocity components within a plane simultaneously and in near real time. To make measurements the DGV, like many other velocimetry systems, relies on the scattering of light from numerous small particles in a flow field. The particles or seeds are illuminated by a sheet of laser light and viewed by two CCD cameras. The scattered light from the particles will have a frequency which is a function of the source laser light frequency, the viewing angle, and most importantly the seed velocities. By determining the scattered light intensity the velocity can be measured at all points within the light sheet simultaneously. Upon completion of DGV component construction and initial check out a series of tests in the Basic Aerodynamic Research (wind) Tunnel (BART) are scheduled to verify instrument operation and accuracy. If the results are satisfactory, application of the DGV to flight measurements on the F-18 High Alpha Research Vehicle (HARV) are planned. The DGV verification test in the BART facility will utilize a 75 degree swept delta wing model. A major task undertaken this summer included evaluation of previous results for this model. A specific series of tests matching exactly the previous tests and exploring new DGV capabilities were developed and suggested. Another task undertaken was to study DGV system installation possibilities in the F-18 HARV aircraft. In addition, a simple seeding system modification was developed and utilized to make Particle Imaging Velocimetry (PIV) measurements in the BART facility.
Correlation-based Transition Modeling for External Aerodynamic Flows
Medida, Shivaji
Conventional turbulence models calibrated for fully turbulent boundary layers often over-predict drag and heat transfer on aerodynamic surfaces with partially laminar boundary layers. A robust correlation-based model is developed for use in Reynolds-Averaged Navier-Stokes simulations to predict laminar-to-turbulent transition onset of boundary layers on external aerodynamic surfaces. The new model is derived from an existing transition model for the two-equation k-omega Shear Stress Transport (SST) turbulence model, and is coupled with the one-equation Spalart-Allmaras (SA) turbulence model. The transition model solves two transport equations for intermittency and transition momentum thickness Reynolds number. Experimental correlations and local mean flow quantities are used in the model to account for effects of freestream turbulence level and pressure gradients on transition onset location. Transition onset is triggered by activating intermittency production using a vorticity Reynolds number criterion. In the new model, production and destruction terms of the intermittency equation are modified to improve consistency in the fully turbulent boundary layer post-transition onset, as well as ensure insensitivity to freestream eddy viscosity value specified in the SA model. In the original model, intermittency was used to control production and destruction of turbulent kinetic energy. Whereas, in the new model, only the production of eddy viscosity in SA model is controlled, and the destruction term is not altered. Unlike the original model, the new model does not use an additional correction to intermittency for separation-induced transition. Accuracy of drag predictions are improved significantly with the use of the transition model for several two-dimensional single- and multi-element airfoil cases over a wide range of Reynolds numbers. The new model is able to predict the formation of stable and long laminar separation bubbles on low-Reynolds number airfoils that
Unsteady Aerodynamics of Flapping Wing of a Bird
Directory of Open Access Journals (Sweden)
M. Agoes Moelyadi
2013-04-01
Full Text Available The unsteady flow behavior and time-dependent aerodynamic characteristics of the flapping motion of a bird’s wing were investigated using a computational method. During flapping, aerodynamic interactions between bird wing surfaces and surrounding flow may occur, generating local time-dependent flow changes in the flow field and aerodynamic load of birds. To study the effect of flapping speed on unsteady aerodynamic load, two kinds of computational simulations were carried out, namely a quasi-steady and an unsteady simulation. To mimic the movement of the down-stroke and the upstroke of a bird, the flapping path accorded to a sinus function, with the wing attitude changing in dihedral angle and time. The computations of time-dependent viscous flow were based on the solution of the Reynolds Averaged Navier-Stokes equations by applying the k-e turbulence model. In addition, the discretization for the computational domain around the model used multi-block structured grid to provide more accuracy in capturing viscous flow, especially in the vicinity of the wing and body surfaces, to obtain a proper wing-body geometry model. For this research, the seagull bird was chosen, which has high aspect ratio wings with pointed wing-tips and a high camber wing section. The results include mesh movement, velocity contours as well as aerodynamic coefficients of the flapping motion of the bird at various flapping frequencies.
Aerodynamic and Aeroacoustic Wind Tunnel Testing of the Orion Spacecraft
Ross, James C.
2011-01-01
The Orion aerodynamic testing team has completed more than 40 tests as part of developing the aerodynamic and loads databases for the vehicle. These databases are key to achieving good mechanical design for the vehicle and to ensure controllable flight during all potential atmospheric phases of a mission, including launch aborts. A wide variety of wind tunnels have been used by the team to document not only the aerodynamics but the aeroacoustic environment that the Orion might experience both during nominal ascents and launch aborts. During potential abort scenarios the effects of the various rocket motor plumes on the vehicle must be accurately understood. The Abort Motor (AM) is a high-thrust, short duration motor that rapidly separates Orion from its launch vehicle. The Attitude Control Motor (ACM), located in the nose of the Orion Launch Abort Vehicle, is used for control during a potential abort. The 8 plumes from the ACM interact in a nonlinear manner with the four AM plumes which required a carefully controlled test to define the interactions and their effect on the control authority provided by the ACM. Techniques for measuring dynamic stability and for simulating rocket plume aerodynamics and acoustics were improved or developed in the course of building the aerodynamic and loads databases for Orion.
Resonance versus aerodynamics for energy savings in agile natural flyers
Kok, Jia M.; Chahl, Javaan
2014-03-01
Insects are the most diverse natural flyers in nature, being able to hover and perform agile manoeuvres. Dragon- flies in particular are aggressive flyers, attaining accelerations of up to 4g. Flight in all insects requires demanding aerodynamic and inertial loads be overcome. It has been proposed that resonance is a primary mechanism for reducing energy costs associated with flapping flight, by storing energy in an elastic thorax and releasing it on the following half-stroke. Certainly in insect flight motors dominated by inertial loads, such a mechanism would be extremely beneficial. However in highly manoeuvrable, aerodynamically dominated flyers, such as the dragonfly, the use of elastic storage members requires further investigation. We show that employing resonant mechanisms in a real world configuration produces minimal energy savings that are further reduced by 50 to 133% across the operational flapping frequency band of the dragonfly. Using a simple harmonic oscillator analysis to represent the dynamics of a dragonfly, we further demonstrate a reduction in manoeuvring limits of ˜1.5 times for a system employing elastic mechanisms. This is in contrast to the potential power reductions of √2/2 from regulating aerodynamics via active wing articulation. Aerodynamic means of energy storage provides flexibility between an energy efficient hover state and a manoeuvrable state capable of large accelerations. We conclude that active wing articulation is preferable to resonance for aerodynamically dominated natural flyers.
Research on the Aerodynamic Lift of Vehicle Windshield Wiper
Directory of Open Access Journals (Sweden)
Gu Zhengqi
2016-01-01
Full Text Available Currently, research on the aerodynamic lift of vehicle windshield wipers is confined to the steady results, and there are very few test results. In the face of this truth, a wind tunnel test is conducted by using the Multipoint Film Force Test System (MFF. In this test, the aerodynamic lift of four kinds of wiper is measured at different wind speeds and different rotation angles. And then, relevant steady-state numerical simulations are accomplished and the mechanism of the aerodynamic lift is analyzed. Furthermore, combined with dynamic meshing and user-defined functions (UDF, transient aerodynamic characteristics of wipers are obtained through numerical simulations. It is found that the aerodynamic lift takes great effect on the stability of wipers, and there is maximum value of the lift near a certain wind speed and rotation angle. The lift force when wipers are rotating with the free stream is less than steady, and the force when rotating against the free stream is greater than steady.
Blissit, J. A.
1986-01-01
Using analysis results from the post trajectory optimization program, an adaptive guidance algorithm is developed to compensate for density, aerodynamic and thrust perturbations during an atmospheric orbital plane change maneuver. The maneuver offers increased mission flexibility along with potential fuel savings for future reentry vehicles. Although designed to guide a proposed NASA Entry Research Vehicle, the algorithm is sufficiently generic for a range of future entry vehicles. The plane change analysis provides insight suggesting a straight-forward algorithm based on an optimized nominal command profile. Bank angle, angle of attack, and engine thrust level, ignition and cutoff times are modulated to adjust the vehicle's trajectory to achieve the desired end-conditions. A performance evaluation of the scheme demonstrates a capability to guide to within 0.05 degrees of the desired plane change and five nautical miles of the desired apogee altitude while maintaining heating constraints. The algorithm is tested under off-nominal conditions of + or -30% density biases, two density profile models, + or -15% aerodynamic uncertainty, and a 33% thrust loss and for various combinations of these conditions.
International Nuclear Information System (INIS)
The potential of controlling shockwave—boundary layer interactions (SWBLIs) in air by plasma aerodynamic actuation is demonstrated. Experiments are conducted in a Mach 3 in-draft air tunnel. The separation-inducing shock is generated with a diamond-shaped shockwave generator located on the wall opposite to the surface electrodes, and the flow properties are studied with schlieren imaging and static wall pressure probes. The measurements show that the separation phenomenon is weakened with the plasma aerodynamic actuation, which is observed to have significant control authority over the interaction. The main effect is the displacement of the reflected shock. Perturbations of incident and reflected oblique shocks interacting with the separation bubble in a rectangular cross section supersonic test section are produced by the plasma actuation. This interaction results in a reduction of the separation bubble size, as detected by phase-lock schlieren images. The measured static wall pressure also shows that the separation-inducing shock is restrained. Our results suggest that the boundary layer separation control through heating is the primary control mechanism. (physics of gases, plasmas, and electric discharges)
Aerodynamics and combustion of axial swirlers
Fu, Yongqiang
A multipoint lean direct injection (LDI) concept was introduced recently in non-premixed combustion to obtain both low NOx emissions and good combustion stability. In this concept, a key feature is the injection of finely atomized fuel into the high-swirling airflow at the combustor dome that provides a homogenous, lean fuel-air mixture. In order to achieve the fine atomization and mixing of the fuel and air quickly and uniformly, a good swirler design should be studied. The focus of this dissertation is to investigate the aerodynamics and combustion of the swirling flow field in a multipoint Lean Direct Injector combustor. A helical axial-vaned swirler with a short internal convergent-divergent venturi was used. Swirlers with various vane angles and fuel nozzle insertion lengths have been designed. Three non-dimensional parameter effects on non-reacting, swirling flow field were studied: swirler number, confinement ratio and Reynolds number. Spray and combustion characteristics on the single swirler were studied to understand the mechanism of fuel-air mixing in this special configuration. Multi-swirler interactions were studied by measuring the confined flow field of a multipoint swirler array with different configurations. Two different swirler arrangements were investigated experimentally, which include a co-swirling array and a counter-swirling array. In order to increase the range of stability of multipoint LDI combustors, an improved design were also conducted. The results show that the degree of swirl and the level of confinement have a clear impact on the mean and turbulent flow fields. The swirling flow fields may also change significantly with the addition of a variety of simulated fuel nozzle insertion lengths. The swirler with short insertion has the stronger swirling flow as compared with the long insertion swirler. Reynolds numbers, with range of current study, will not alter mean and turbulent properties of generated flows. The reaction of the spray
Two cases of aerodynamic adjustment of sastrugi
Directory of Open Access Journals (Sweden)
C. Amory
2015-11-01
Full Text Available In polar regions, sastrugi are a direct manifestation of wind driven snow and form the main surface roughness elements. In turn, sastrugi influence the local wind field and associated aeolian snow mass fluxes. Little attention has been paid to these feedback processes, mainly because of experimental difficulties, and, as a result most polar atmospheric models currently ignore sastrugi. More accurate quantification of the influence of sastrugi remains a major challenge. In the present study, wind profiles and aeolian snow mass fluxes were analyzed jointly on a sastrugi covered snowfield in Antarctica. Neutral stability 10 m air-snow drag coefficients CDN10 were computed from six level wind speed profiles collected in Adélie Land during austral winter 2013. The aeolian snow mass flux in the first meter above the surface of the snow was also measured using a windborne snow acoustic sensor. This paper focuses on two cases during which sastrugi responses to shifts in wind direction were evidenced by variations in snow mass flux and drag coefficients. Using this dataset, it was shown that (i the timescale of sastrugi aerodynamic adjustment can be as short as 3 h for friction velocities of 1 m s−1 or above and during strong windborne snow conditions, (ii CDN10 values were in the range of 1.3–1.5 × 103 when the wind was well aligned with the sastrugi and increased to 3 × 103 or higher when the wind only shifted 20–30°, (iii CDN10 can increase (to 120 % and the aeolian snow mass flux can decrease (to 80 % in response to a shift in wind direction, and (iv knowing CDN10 is not sufficient to estimate the erosion flux that results from drag partitioning at the surface because CDN10 includes the contribution of the sastrugi form drag. These results not only support the existence of feedback mechanisms linking sastrugi, aeolian particle transport and surface drag properties over snow surface but also provide orders of magnitude, although further
Aerodynamic window for high precision laser drilling
Sommer, Steffen; Dausinger, Friedrich; Berger, Peter; Hügel, Helmuth
2007-05-01
High precision laser drilling is getting more and more interesting for industry. Main applications for such holes are vaporising and injection nozzles. To enhance quality, the energy deposition has to be accurately defined by reducing the pulse duration and thereby reducing the amount of disturbing melting layer. In addition, an appropriate processing technology, for example the helical drilling, yields holes in steel at 1 mm thickness and diameters about 100 μm with correct roundness and thin recast layers. However, the processing times are still not short enough for industrial use. Experiments have shown that the reduction of the atmospheric pressure down to 100 hPa enhances the achievable quality and efficiency, but the use of vacuum chambers in industrial processes is normally quite slow and thus expensive. The possibility of a very fast evacuation is given by the use of an aerodynamic window, which produces the pressure reduction by virtue of its fluid dynamic features. This element, based on a potential vortex, was developed and patented as out-coupling window for high power CO II lasers by IFSW 1, 2, 3. It has excellent tightness and transmission properties, and a beam deflection is not detectable. The working medium is compressed air, only. For the use as vacuum element for laser drilling, several geometrical modifications had to be realized. The prototype is small enough to be integrated in a micromachining station and has a low gas flow. During the laser pulse, which is focussed through the potential flow, a very high fluence is reached, but the measurements have not shown any beam deflection or focal shifting. The evacuation time is below 300 ms so that material treatment with changing ambient pressure is possible, too. Experimental results have proven the positive effect of the reduced ambient pressure on the drilling process for the regime of nano- and picosecond laser pulses. Plasma effects are reduced and, because of the less absorption, the
AERODYNAMIC AND BLADING DESIGN OF MULTISTAGE AXIAL FLOW COMPRESSORS
Crouse, J. E.
1994-01-01
The axial-flow compressor is used for aircraft engines because it has distinct configuration and performance advantages over other compressor types. However, good potential performance is not easily obtained. The designer must be able to model the actual flows well enough to adequately predict aerodynamic performance. This computer program has been developed for computing the aerodynamic design of a multistage axial-flow compressor and, if desired, the associated blading geometry input for internal flow analysis. The aerodynamic solution gives velocity diagrams on selected streamlines of revolution at the blade row edges. The program yields aerodynamic and blading design results that can be directly used by flow and mechanical analysis codes. Two such codes are TSONIC, a blade-to-blade channel flow analysis code (COSMIC program LEW-10977), and MERIDL, a more detailed hub-to-shroud flow analysis code (COSMIC program LEW-12966). The aerodynamic and blading design program can reduce the time and effort required to obtain acceptable multistage axial-flow compressor configurations by generating good initial solutions and by being compatible with available analysis codes. The aerodynamic solution assumes steady, axisymmetric flow so that the problem is reduced to solving the two-dimensional flow field in the meridional plane. The streamline curvature method is used for the iterative aerodynamic solution at stations outside of the blade rows. If a blade design is desired, the blade elements are defined and stacked within the aerodynamic solution iteration. The blade element inlet and outlet angles are established by empirical incidence and deviation angles to the relative flow angles of the velocity diagrams. The blade element centerline is composed of two segments tangentially joined at a transition point. The local blade angle variation of each element can be specified as a fourth-degree polynomial function of path distance. Blade element thickness can also be specified
Atmospheric testing of wind turbine trailing edge aerodynamic brakes
Energy Technology Data Exchange (ETDEWEB)
Miller, L.S. [Wichita State Univ., KS (United States); Migliore, P.G. [National Renewable Energy Lab., Golden, CO (United States); Quandt, G.A.
1997-12-31
An experimental investigation was conducted using an instrumented horizontal-axis wind turbine that incorporated variable span trailing-edge aerodynamic brakes. A primary goal was to directly compare study results with (infinite-span) wind tunnel data and to provide information on how to account for device span effects during turbine design or analysis. Comprehensive measurements were utilized to define effective changes in the aerodynamic coefficients, as a function of angle of attack and control deflection, for three device spans and configurations. Differences in the lift and drag behavior are most pronounced near stall and for device spans of less than 15%. Drag performance is affected only minimally (<70%) for 15% or larger span devices. Interestingly, aerodynamic controls with characteristic vents or openings appear most affected by span reductions and three-dimensional flow.
The research analysis of aerodynamic numerical simulation of grid fin
Institute of Scientific and Technical Information of China (English)
WU Pin; MA Yong-gang; CHEN Chun
2005-01-01
This paper presents the results of an investigation to use arc-length mesh generation and finite volume TVD scheme to calculate Euler equations for predicting the effect of geometry parameters in reducing the drag force and improving the lift-drag ratio of grid fin in the supersonic flow regime. The effects of frame and web, whose cross section shape and thickness and spacing,on the aerodynamic character of the grid fin were studied. Calculations were made at Mach 2.5 and several angles of attack. The results were validated by comparing the computed aerodynamic coefficients against wind tunnel experimental data. Good agreement was found between computed and experimental results. The computed results suggest that parameters of the grid fin's frame have the greatest effect on the grid fin aerodynamic character, especially on its drag force. It was concluded proper choice of appropriate grid fin geometry parameters could reduce the drag force and improve the lift-drag ratios.
Fluidic Control of Aerodynamic Forces on an Axisymmetric Body
Abramson, Philip; Vukasinovic, Bojan; Glezer, Ari
2007-11-01
The aerodynamic forces and moments on a wind tunnel model of an axisymmetric bluff body are modified by induced local vectoring of the separated base flow. Control is effected by an array of four integrated aft-facing synthetic jets that emanate from narrow, azimuthally-segmented slots, equally distributed around the perimeter of the circular tail end within a small backward facing step that extends into a Coanda surface. The model is suspended in the wind tunnel by eight thin wires for minimal support interference with the wake. Fluidic actuation results in a localized, segmented vectoring of the separated base flow along the rear Coanda surface and induces asymmetric aerodynamic forces and moments to effect maneuvering during flight. The aerodynamic effects associated with quasi-steady and transitory differential, asymmetric activation of the Coanda effect are characterized using direct force and PIV measurements.
Design Estimation of Aerodynamic Angles of High Speed Cars
Directory of Open Access Journals (Sweden)
Debojyoti Mitra
2010-05-01
Full Text Available The study of aerodynamic design of high-speed cars is mainly based on the wind-tunnel experiments and computational methods till date. In this particular study three car models of 100,200,300 pitch angles and 500,600,700 yaw angles are employed, and by wind-tunnel experiments we obtain pressure distributions over them. Now the correlations between drag-coefficient, lift-coefficient, pitch-angle and yaw-angle with Reynolds number are obtained by regression analysis of experimental data using MATLAB software. After plotting graphs it can be concluded that for minimum aerodynamic drag the optimized value of pitch and yaw angle should be 300 and 500. This type of study is expected to give a fair idea of aerodynamic angle design of high-speed cars.
APPLICATION OF VARIABLE-FIDELITY MODELS TO AERODYNAMIC OPTIMIZATION
Institute of Scientific and Technical Information of China (English)
XIA Lu; GAO Zheng-hong
2006-01-01
For aerodynamic shape optimization, the approximation management framework (AMF) method is used to organize and manage the variable-fidelity models. The method can take full advantage of the low-fidelity, cheaper models to concentrate the main workload on the low-fidelity models in optimization iterative procedure. Furthermore, it can take high-fidelity, more expensive models to monitor the procedure to make the method globally convergent to a solution of high-fidelity problem. Finally, zero order variable-fidelity aerodynamic optimization management framework and search algorithm are demonstrated on an airfoil optimization of UAV with a flying wing. Compared to the original shape, the aerodynamic performance of the optimal shape is improved. The results show the method has good feasibility and applicability.
Investigates on Aerodynamic Characteristics of Projectile with Triangular Cross Section
Institute of Scientific and Technical Information of China (English)
YI Wen-jun; WANG Zhong-yuan; LI Yan; QIAN Ji-sheng
2009-01-01
The aerodynamic characteristics of projectiles with triangular and circular cross sections are investigated respectively by use of free-flight experiment. Processed the experiment data, curves of flight velocity variation and nutation of both projectiles are obtained, based on the curves, their aerodynamic force and moment coefficients are found out by data fitting, and their aerodynamic performances are compared and analyzed. Results show that the projectile with triangular cross section has smaller resistance, higher lift-drag ratio, better static stability, higher stability capability and more excellent maneuverability than those of the projectile with circular cross section, therefore it can be used in the guided projectiles; under lower rotation speed, the triangular section projectile has greater Magnus moment leading to bigger projectile distribution.
Investigation of Aerodynamic Capabilities of Flying Fish in Gliding Flight
Park, H.; Choi, H.
In the present study, we experimentally investigate the aerodynamic capabilities of flying fish. We consider four different flying fish models, which are darkedged-wing flying fishes stuffed in actual gliding posture. Some morphological parameters of flying fish such as lateral dihedral angle of pectoral fins, incidence angles of pectoral and pelvic fins are considered to examine their effect on the aerodynamic performance. We directly measure the aerodynamic properties (lift, drag, and pitching moment) for different morphological parameters of flying fish models. For the present flying fish models, the maximum lift coefficient and lift-to-drag ratio are similar to those of medium-sized birds such as the vulture, nighthawk and petrel. The pectoral fins are found to enhance the lift-to-drag ratio and the longitudinal static stability of gliding flight. On the other hand, the lift coefficient and lift-to-drag ratio decrease with increasing lateral dihedral angle of pectoral fins.
Improved blade element momentum theory for wind turbine aerodynamic computations
DEFF Research Database (Denmark)
Sun, Zhenye; Chen, Jin; Shen, Wen Zhong;
2016-01-01
Blade element momentum (BEM) theory is widely used in aerodynamic performance predictions and design applications for wind turbines. However, the classic BEM method is not quite accurate which often tends to under-predict the aerodynamic forces near root and over-predict its performance near tip....... The reliability of the aerodynamic calculations and design optimizations is greatly reduced due to this problem. To improve the momentum theory, in this paper the influence of pressure drop due to wake rotation and the effect of radial velocity at the rotor disc in the momentum theory are considered. Thus...... the axial induction factor in far downstream is not simply twice of the induction factor at disc. To calculate the performance of wind turbine rotors, the improved momentum theory is considered together with both Glauert's tip correction and Shen's tip correction. Numerical tests have been performed...
Aerodynamic performance of vertical and horizontal axis wind turbines
Maydew, R. C.; Klimas, P. C.
1981-06-01
The aerodynamic performance of vertical and horizontal axis wind turbines is investigated, and comparison of data of the 17-m Darrieus VAWT with the 60.7-m Mod-1 HAWT and 37.8-m Mod-0A HAWT is discussed. It is concluded that the maximum average measured power coefficients of the VAWT are about 0%-15% higher than those of the HAWTs. It is suggested that vertical wind shear may have lowered the Mod-1 HAWT aerodynamic performance, but, the magnitude of this effect could not be evaluated. It is included that generalizations which refer to the Darrieus VAWT as aerodynamically less efficient than the HAWT should be used carefully.
Aerodynamic levitator for large-sized glassy material production.
Yoda, Shinichi; Cho, Won-Seung; Imai, Ryoji
2015-09-01
Containerless aerodynamic levitation processing is a unique technology for the fabrication of bulk non-crystalline materials. Using conventional aerodynamic levitation, a high reflective index (RI) material (BaTi2O5 and LaO3/2-TiO2-ZrO2 system) was developed with a RI greater than approximately 2.2, which is similar to that of diamond. However, the glass size was small, approximately 3 mm in diameter. Therefore, it is essential to produce large sized materials for future optical materials applications, such as camera lenses. In this study, a new aerodynamic levitator was designed to produce non-crystalline materials with diameters larger than 6 mm. The concept of this new levitator was to set up a reduced pressure at the top of the molten samples without generating turbulent flow. A numerical simulation was also performed to verify the concept. PMID:26429456
Aerodynamic Jump: A Short Range View for Long Rod Projectiles
Directory of Open Access Journals (Sweden)
Mark Bundy
2001-01-01
Full Text Available It is shown that aerodynamic jump for a nonspinning kinetic energy penetrator is not – as conventional definitions may infer – a discontinuous change in the direction of motion at the origin of free flight, nor is it the converse, a cumulative redirection over a domain of infinite extent. Rather, with the aid of an alternative kinematical definition, it is shown that aerodynamic jump for such a projectile is a localized redirection of the center-of-gravity motion, caused by the force of lift due to yaw over the relatively short region from entry into free flight until the yaw reaches its first maximum. A rigorous proof of this statement is provided, but the primary objective of this paper is to provide answers to the questions: what is aerodynamic jump, what does it mean, and what aspects of the flight trajectory does it refer to, or account for.
Analysis of Flow Structures in Wake Flows for Train Aerodynamics
Muld, Tomas W.
2010-01-01
Train transportation is a vital part of the transportation system of today anddue to its safe and environmental friendly concept it will be even more impor-tant in the future. The speeds of trains have increased continuously and withhigher speeds the aerodynamic effects become even more important. One aero-dynamic effect that is of vital importance for passengers’ and track workers’safety is slipstream, i.e. the flow that is dragged by the train. Earlier ex-perimental studies have found that ...
Computational methods for aerodynamic design using numerical optimization
Peeters, M. F.
1983-01-01
Five methods to increase the computational efficiency of aerodynamic design using numerical optimization, by reducing the computer time required to perform gradient calculations, are examined. The most promising method consists of drastically reducing the size of the computational domain on which aerodynamic calculations are made during gradient calculations. Since a gradient calculation requires the solution of the flow about an airfoil whose geometry was slightly perturbed from a base airfoil, the flow about the base airfoil is used to determine boundary conditions on the reduced computational domain. This method worked well in subcritical flow.
Efficient optimization of integrated aerodynamic-structural design
Haftka, R. T.; Grossman, B.; Eppard, W. M.; Kao, P. J.; Polen, D. M.
1989-01-01
Techniques for reducing the computational complexity of multidisciplinary design optimization (DO) of aerodynamic structures are described and demonstrated. The basic principles of aerodynamic and structural DO are reviewed; the formulation of the combined DO problem is outlined; and particular attention is given to (1) the application of perturbation methods to cross-sensitivity computations and (2) numerical approximation procedures. Trial DOs of a simple sailplane design are presented in tables and graphs and discussed in detail. The IBM 3090 CPU time for the entire integrated DO was reduced from an estimated 10 h to about 6 min.
Cruise aerodynamics of USB nacelle/wing geometric variations
Braden, J. A.; Hancock, J. P.; Burdges, K. P.
1976-01-01
Experimental results are presented on aerodynamic effects of geometric variations in upper surface blown nacelle configurations at high speed cruise conditions. Test data include both force and pressure measurements on two and three dimensional models powered by upper surface blowing nacelles of varying geometries. Experimental results are provided on variations in nozzle aspect ratio, nozzle boattail angle, and multiple nacelle installations. The nacelles are ranked according to aerodynamic drag penalties as well as overall installed drag penalties. Sample effects and correlations are shown for data obtained with the pressure model.
Aerodynamic Support of a Big Industrial Turboblower Rotor
Šimek, Jiří; Kozánek, Jan; Šafr, Milan
2007-01-01
Aerodynamic bearing support for the rotor of a 100 kW input industrial turboblower with operational speed of 18 000 rpm was designed and manufactured. Rotor with mass of about 50 kg is supported in two tilting-pad journal bearings 120 mm in diameter, axial forces are taken up by aerodynamic spiral groove thrust bearing 250 mm in diameter. Some specific features of the bearing design are described in the paper and the results of rotor support tests are presented. The paper is an extended versi...
Hybrid Vortex Method for the Aerodynamic Analysis of Wind Turbine
Directory of Open Access Journals (Sweden)
Hao Hu
2015-01-01
Full Text Available The hybrid vortex method, in which vortex panel method is combined with the viscous-vortex particle method (HPVP, was established to model the wind turbine aerodynamic and relevant numerical procedure program was developed to solve flow equations. The panel method was used to calculate the blade surface vortex sheets and the vortex particle method was employed to simulate the blade wake vortices. As a result of numerical calculations on the flow over a wind turbine, the HPVP method shows significant advantages in accuracy and less computation resource consuming. The validation of the aerodynamic parameters against Phase VI wind turbine experimental data is performed, which shows reasonable agreement.
Feasibility study for a numerical aerodynamic simulation facility. Volume 1
Lincoln, N. R.; Bergman, R. O.; Bonstrom, D. B.; Brinkman, T. W.; Chiu, S. H. J.; Green, S. S.; Hansen, S. D.; Klein, D. L.; Krohn, H. E.; Prow, R. P.
1979-01-01
A Numerical Aerodynamic Simulation Facility (NASF) was designed for the simulation of fluid flow around three-dimensional bodies, both in wind tunnel environments and in free space. The application of numerical simulation to this field of endeavor promised to yield economies in aerodynamic and aircraft body designs. A model for a NASF/FMP (Flow Model Processor) ensemble using a possible approach to meeting NASF goals is presented. The computer hardware and software are presented, along with the entire design and performance analysis and evaluation.
Analysis of broadband aerodynamic noise from VS45
Energy Technology Data Exchange (ETDEWEB)
Dundabin, P. [Renewable Energy Systems Ltd., Glasgow, Scotland (United Kingdom)
1997-12-31
This paper describes the analysis of acoustic data taken from the VS45 at Kaiser-Wilhelm-Koog. The aim was to investigate the dependence of aerodynamic noise on tip speed and angle of attack. In particular, the dependence of noise in individual third octave bands on these variable is examined. The analysis is divided into 3 sections: data selection, data checks and analysis of broadband nacelle noise; analysis of broadband aerodynamic noise and its sensitivity to tip speed and angle of attack. (LN)
Aerodynamics of Dragonfly in Hover: Force measurements and PIV results
Deng, Xinyan; Hu, Zheng
2009-11-01
We useda pair of dynamically scaled robotic dragonfly model wings to investigate the aerodynamic effects of wing-wing interaction in dragonflies. We follow the wing kinematics of real dragonflies in hover, while systematically varied the phase difference between the forewing and hindwing. Instantaneous aerodynamic forces and torques were measured on both wings, while flow visualization and PIV results were obtained. The results show that, in hovering flight, wing-wing interaction causes force reduction for both wings at most of the phase angle differences except around 0 degree (when the wings are beating in-phase).
Improvements on computations of high speed propeller unsteady aerodynamics
Energy Technology Data Exchange (ETDEWEB)
Bousquet, J.M.; Gardarein, P. [Office National d' Etudes et de Recherches Aerospatiales (ONERA), 92 - Chatillon (France)
2003-09-01
This paper presents the application of the CANARI flow solver to the computation of unsteady effects in the aerodynamic interaction of a high speed propeller with the aircraft. The method is first validated on the APIAN isolated propeller test case by comparison with experiment at M = 0.7. The method is then applied to the time accurate 3D Euler computation of a generic transport aircraft at M = 0.68. Analysis of the results shows significant unsteady effects both on the propeller forces and on the wing aerodynamic flows, by comparison with steady computations. (authors)
Improved Aerodynamic Influence Coefficients for Dynamic Aeroelastic Analyses
Gratton, Patrice
2011-12-01
Currently at Bombardier Aerospace, aeroelastic analyses are performed using the Doublet Lattice Method (DLM) incorporated in the NASTRAN solver. This method proves to be very reliable and fast in preliminary design stages where wind tunnel experimental results are often not available. Unfortunately, the geometric simplifications and limitations of the DLM, based on the lifting surfaces theory, reduce the ability of this method to give reliable results for all flow conditions, particularly in transonic flow. Therefore, a new method has been developed involving aerodynamic data from high-fidelity CFD codes which solve the Euler or Navier-Stokes equations. These new aerodynamic loads are transmitted to the NASTRAN aeroelastic module through improved aerodynamic influence coefficients (AIC). A cantilevered wing model is created from the Global Express structural model and a set of natural modes is calculated for a baseline configuration of the structure. The baseline mode shapes are then combined with an interpolation scheme to deform the 3-D CFD mesh necessary for Euler and Navier-Stokes analyses. An uncoupled approach is preferred to allow aerodynamic information from different CFD codes. Following the steady state CFD analyses, pressure differences ( DeltaCp), calculated between the deformed models and the original geometry, lead to aerodynamic loads which are transferred to the DLM model. A modal-based AIC method is applied to the aerodynamic matrices of NASTRAN based on a least-square approximation to evaluate aerodynamic loads of a different wing configuration which displays similar types of mode shapes. The methodology developed in this research creates weighting factors based on steady CFD analyses which have an equivalent reduced frequency of zero. These factors are applied to both the real and imaginary part of the aerodynamic matrices as well as all reduced frequencies used in the PK-Method which solves flutter problems. The modal-based AIC method
Heat Waves Dangers we face during periods of very high temperatures include: Heat cramps: These are muscular pains and spasms due ... that the body is having trouble with the heat. If a heat wave is predicted or happening… - ...
Aerodynamic Profiles of Women with Muscle Tension Dysphonia/Aphonia
Gillespie, Amanda I.; Gartner-Schmidt, Jackie; Rubinstein, Elaine N.; Abbott, Katherine Verdolini
2013-01-01
Purpose: In this study, the authors aimed to (a) determine whether phonatory airflows and estimated subglottal pressures (est-P[subscript sub]) for women with primary muscle tension dysphonia/aphonia (MTD/A) differ from those for healthy speakers; (b) identify different aerodynamic profile patterns within the MTD/A subject group; and (c) determine…
Studying surface glow discharge for application in plasma aerodynamics
Tereshonok, D. V.
2014-02-01
Surface glow discharge in nitrogen between two infinite planar electrodes occurring on the same plane has been studied in the framework of a diffusion-drift model. Based on the results of numerical simulations, the plasma structure of this discharge is analyzed and the possibility of using it in plasma aerodynamics is considered.
Laryngeal Aerodynamics Associated with Oral Contraceptive Use: Preliminary Findings
Gorham-Rowan, Mary; Fowler, Linda
2009-01-01
The purpose of this study was to examine possible differences in laryngeal aerodynamic measures during connected speech associated with oral contraceptive (OC) use. Eight women taking an OC, and eight others not taking an OC, participated in the study. Three trials of syllable /p[subscript alpha] /repetitions were obtained using a…
Unsteady Aerodynamic Flow Control of a Suspended Axisymmetric Moving Platform
Lambert, Thomas; Vukasinovic, Bojan; Glezer, Ari
2011-11-01
The aerodynamic forces on an axisymmetric wind tunnel model are altered by fluidic interaction of an azimuthal array of integrated synthetic jet actuators with the cross flow. Four-quadrant actuators are integrated into a Coanda surface on the aft section of the body, and the jets emanate from narrow, azimuthally segmented slots equally distributed around the model's perimeter. The model is suspended in the tunnel using eight wires each comprising miniature in-line force sensors and shape-memory-alloy (SMA) strands that are used to control the instantaneous forces and moments on the model and its orientation. The interaction of the actuation jets with the flow over the moving model is investigated using PIV and time-resolved force measurements to assess the transitory aerodynamic loading effected by coupling between the induced motion of the aerodynamic surface and the fluid dynamics that is driven by the actuation. It is shown that these interactions can lead to effective control of the aerodynamic forces and moments, and thereby of the model's motion. Supported by ARO.
Improving the efficiency of aerodynamic shape optimization on unstructured meshes
Carpentieri, G.; Tooren, M.J.L. van; Koren, B.
2006-01-01
In this paper the exact discrete adjoint of a finite volume formulation on unstructured meshes for the Euler equations in two dimensions is derived and implemented to support aerodynamic shape optimization. The accuracy of the discrete exact adjoint is demonstrated and compared with that of the appr
The effect of aerodynamic parameters on power output of windmills
Wiesner, W.
1973-01-01
Aerodynamic results for a study on windpower generation are reported. Windmill power output is presented in terms that are commonly used in rotary wing analysis, namely, power output as a function of drag developed by the windmill. Effect of tip speed ratio, solidity, twist, wind angle, blade setting and airfoil characteristics are given.
Plasma Aerodynamic Control Effectors for Improved Wind Turbine Performance
Energy Technology Data Exchange (ETDEWEB)
Mehul P. Patel; Srikanth Vasudevan; Robert C. Nelson; Thomas C. Corke
2008-08-01
Orbital Research Inc is developing an innovative Plasma Aerodynamic Control Effectors (PACE) technology for improved performance of wind turbines. The PACE system is aimed towards the design of "smart" rotor blades to enhance energy capture and reduce aerodynamic loading and noise using flow-control. The PACE system will provide ability to change aerodynamic loads and pitch distribution across the wind turbine blade without any moving surfaces. Additional benefits of the PACE system include reduced blade structure weight and complexity that should translate into a substantially reduced initial cost. During the Phase I program, the ORI-UND Team demonstrated (proof-of-concept) performance improvements on select rotor blade designs using PACE concepts. Control of both 2-D and 3-D flows were demonstrated. An analytical study was conducted to estimate control requirements for the PACE system to maintain control during wind gusts. Finally, independent laboratory experiments were conducted to identify promising dielectric materials for the plasma actuator, and to examine environmental effects (water and dust) on the plasma actuator operation. The proposed PACE system will be capable of capturing additional energy, and reducing aerodynamic loading and noise on wind turbines. Supplementary benefits from the PACE system include reduced blade structure weight and complexity that translates into reduced initial capital costs.
Computational aerodynamic analysis on perimeter reinforced (PR)-compliant wing
Institute of Scientific and Technical Information of China (English)
NI Ismail; AH Zulkifli; MZ Abdullah; M Hisyam Basri; Norazharuddin Shah Abdullah
2013-01-01
Implementing the morphing technique on a micro air vehicle (MAV) wing is a very chal-lenging task, due to the MAV’s wing size limitation and the complex morphing mechanism. As a result, understanding aerodynamic characteristics and flow configurations, subject to wing structure deformation of a morphing wing MAV has remained obstructed. Thus, this paper presents the investigation of structural deformation, aerodynamics performance and flow formation on a pro-posed twist morphing MAV wing design named perimeter reinforced (PR)-compliant wing. The numerical simulation of two-way fluid structure interaction (FSI) investigation consist of a quasi-static aeroelastic structural analysis coupled with 3D incompressible Reynolds-averaged Navier-Stokes and shear-stress-transport (RANS-SST) solver utilized throughout this study. Verification of numerical method on a rigid rectangular wing achieves a good correlation with available exper-imental results. A comparative aeroelastic study between PR-compliant to PR and rigid wing per-formance is organized to elucidate the morphing wing performances. Structural deformation results show that PR-compliant wing is able to alter the wing’s geometric twist characteristic, which has directly influenced both the overall aerodynamic performance and flow structure behavior. Despite the superior lift performance result, PR-compliant wing also suffers from massive drag penalty, which has consequently affected the wing efficiency in general. Based on vortices investigation, the results reveal the connection between these aerodynamic performances with vortices formation on PR-compliant wing.
Research on the Aerodynamic Resistance of Trickle Biofilter
Directory of Open Access Journals (Sweden)
Alvydas Zagorskis
2011-12-01
Full Text Available A four – section trickle biofilter was constructed for experimental research. The filter was filled with the packing material of artificial origin. The material consists of plastic balls having a large surface area. The dependence of biofilter aerodynamic resistance on supply air flow rate and the number of filter sections was determined. The aerodynamic resistance of the biofilter was measured in two cases. In the first case, the packing material of the filter was dry, whereas in the second case it was wet. The experimental research determined that an increase in the air flow rate from 0.043 m/s to 0.076 m/s causes an increase in biofilter aerodynamic resistance from 30.5 to 62.5 Pa after measuring four layers of dry packing material. In case of wet packing material, biofilter aerodynamic resistance after measuring four layers of plastic balls increases from 42.1 to 90.4 Pa.Article in Lithuanian
In vivo aerodynamic characteristics of the Nijdam voice prosthesis
van den Hoogen, F. J. A.; Veenstra, Aalze; Verkerke, GJ; Schutte, HK; Manni, JJ
1997-01-01
The Nijdam voice prosthesis is an indwelling valveless voice prosthesis for postlaryngectomy voice rehabilitation. The in vitro aerodynamic characteristics are reported to be comparable to that of the low-resistance Groningen voice prosthesis. Owing to the design of the prosthesis the airflow resist
Aerodynamic stability of cable-supported bridges using CFRP cables
Institute of Scientific and Technical Information of China (English)
ZHANG Xin-jun; YING Lei-dong
2007-01-01
To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable's cross-sectional area is determined by the principle of equivalent axial stiffness.Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge,its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable's cross-sectional area should be determined by the principle of equivalent axial stiffness.
Computations of Aerodynamic Performance Databases Using Output-Based Refinement
Nemec, Marian; Aftosmis, Michael J.
2009-01-01
Objectives: Handle complex geometry problems; Control discretization errors via solution-adaptive mesh refinement; Focus on aerodynamic databases of parametric and optimization studies: 1. Accuracy: satisfy prescribed error bounds 2. Robustness and speed: may require over 105 mesh generations 3. Automation: avoid user supervision Obtain "expert meshes" independent of user skill; and Run every case adaptively in production settings.
Innovation in Aerodynamic Design Features of Soviet Missiles
Spearman, M. Leroy
2006-01-01
Wind tunnel investigations of some tactical and strategic missile systems developed by the former Soviet Union have been included in the basic missile research programs of the NACA/NASA. Studies of the Soviet missiles sometimes revealed innovative design features that resulted in unusual or unexpected aerodynamic characteristics. In some cases these characteristics have been such that the measured performance of the missile exceeds what might have been predicted. In other cases some unusual design features have been found that would alleviate what might otherwise have been a serious aerodynamic problem. In some designs, what has appeared to be a lack of refinement has proven to be a matter of expediency. It is a purpose of this paper to describe some examples of unusual design features of some Soviet missiles and to illustrate the effectiveness of the design features on the aerodynamic behavior of the missile. The paper draws on the experience of the author who for over 60 years was involved in the aerodynamic wind tunnel testing of aircraft and missiles with the NACA/NASA.
Robust Design of Supercritical Wing Aerodynamic Optimization Considering Fuselage Interfering
Institute of Scientific and Technical Information of China (English)
Huang Jiangtao; Gao Zhenghong; Zhao Ke; Bai Junqiang
2010-01-01
Robust optimization approach for aerodynamic design has been developed and applied to supercritical wing aerodynamic de-sign.The aerodynamic robust optimization design system consists of genetic optimization algorithm,improved back propagation (BP) neural network and deformation grid technology.In this article,the BP neural network has been improved in two major aspects to enhance the training speed and precision.Uniformity sampling is adopted to generate samples which will be used to establish surrogate model.The testing results show that the prediction precision of the improved BP neural network is reliable.On the assumption that the law of Mach number obeys normal distribution,supereritical wing configuration considering fuselage interfering of a certain aerobus has been taken as a typical example,and five design sections and twist angles have been opti-mized.The results show that the optimized wing,which considers robust design,has better aerodynamic characteristics.What's more,the intensity of shock wave has been reduced.
Aerodynamic Characteristic of the Active Compliant Trailing Edge Concept
Nie, Rui; Qiu, Jinhao; Ji, Hongli; Li, Dawei
2016-06-01
This paper introduces a novel Morphing Wing structure known as the Active Compliant Trailing Edge (ACTE). ACTE structures are designed using the concept of “distributed compliance” and wing skins of ACTE are fabricated from high-strength fiberglass composites laminates. Through the relative sliding between upper and lower wing skins which are connected by a linear guide pairs, the wing is able to achieve a large continuous deformation. In order to present an investigation about aerodynamics and noise characteristics of ACTE, a series of 2D airfoil analyses are established. The aerodynamic characteristics between ACTE and conventional deflection airfoil are analyzed and compared, and the impacts of different ACTE structure design parameters on aerodynamic characteristics are discussed. The airfoils mentioned above include two types (NACA0012 and NACA64A005.92). The computing results demonstrate that: compared with the conventional plane flap airfoil, the morphing wing using ACTE structures has the capability to improve aerodynamic characteristic and flow separation characteristic. In order to study the noise level of ACTE, flow field analysis using LES model is done to provide noise source data, and then the FW-H method is used to get the far field noise levels. The simulation results show that: compared with the conventional flap/aileron airfoil, the ACTE configuration is better to suppress the flow separation and lower the overall sound pressure level.
Quasi-steady state aerodynamics of the cheetah tail
Directory of Open Access Journals (Sweden)
Amir Patel
2016-08-01
Full Text Available During high-speed pursuit of prey, the cheetah (Acinonyx jubatus has been observed to swing its tail while manoeuvring (e.g. turning or braking but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities.
Quasi-steady state aerodynamics of the cheetah tail.
Patel, Amir; Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily
2016-08-15
During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities.
Aerodynamic Experiments on DelFly II: Unsteady Lift Enhancement
De Clercq, K.M.E.; De Kat, R.; Remes, B.; Van Oudheusden, B.W.; Bijl, H.
2009-01-01
Particle image velocimetry measurements and simultaneous force measurements have been performed on the DelFly II flapping-wing MAV, to investigate the flow-field behavior and the aerodynamic forces generated. For flapping wing motion it is expected that both the clap and peel mechanism and the occur
Mechanism of unconventional aerodynamic characteristics of an elliptic airfoil
Directory of Open Access Journals (Sweden)
Sun Wei
2015-06-01
Full Text Available The aerodynamic characteristics of elliptic airfoil are quite different from the case of conventional airfoil for Reynolds number varying from about 104 to 106. In order to reveal the fundamental mechanism, the unsteady flow around a stationary two-dimensional elliptic airfoil with 16% relative thickness has been simulated using unsteady Reynolds-averaged Navier–Stokes equations and the γ-Reθt‾ transition turbulence model at different angles of attack for flow Reynolds number of 5 × 105. The aerodynamic coefficients and the pressure distribution obtained by computation are in good agreement with experimental data, which indicates that the numerical method works well. Through this study, the mechanism of the unconventional aerodynamic characteristics of airfoil is analyzed and discussed based on the computational predictions coupled with the wind tunnel results. It is considered that the boundary layer transition at the leading edge and the unsteady flow separation vortices at the trailing edge are the causes of the case. Furthermore, a valuable insight into the physics of how the flow behavior affects the elliptic airfoil’s aerodynamics is provided.
Numerical investigation of wind turbine and wind farm aerodynamics
Selvaraj, Suganthi
A numerical method based on the solution of Reynolds Averaged Navier Stokes equations and actuator disk representation of turbine rotor is developed and implemented in the OpenFOAM software suite for aerodynamic analysis of horizontal axis wind turbines (HAWT). The method and the implementation are validated against the 1-D momentum theory, the blade element momentum theory and against experimental data. The model is used for analyzing aerodynamics of a novel dual rotor wind turbine concept and wind farms. Horizontal axis wind turbines suffer from aerodynamic inefficiencies in the blade root region (near the hub) due to several non-aerodynamic constraints (e.g., manufacturing, transportation, cost, etc.). A new dual-rotor wind turbine (DRWT) concept is proposed that aims at mitigating these losses. A DRWT is designed using an existing turbine rotor for the main rotor (Risoe turbine and NREL 5 MW turbine), while the secondary rotor is designed using a high lift to drag ratio airfoil (the DU 96 airfoil from TU Delft). The numerical aerodynamic analysis method developed as a part of this thesis is used to optimize the design. The new DRWT design gives an improvement of about 7% in aerodynamic efficiency over the single rotor turbine. Wind turbines are typically deployed in clusters called wind farms. HAWTs also suffer from aerodynamic losses in a wind farm due to interactions with wind turbine wakes. An interesting mesoscale meteorological phenomenon called "surface flow convergence" believed to be caused by wind turbine arrays is investigated using the numerical method developed here. This phenomenon is believed to be caused by the pressure gradient set up by wind turbines operating in close proximity in a farm. A conceptual/hypothetical wind farm simulation validates the hypothesis that a pressure gradient is setup in wind farms due to turbines and that it can cause flow veering of the order of 10 degrees. Simulations of a real wind farm (Story County) are also
Analytical Aerodynamic Simulation Tools for Vertical Axis Wind Turbines
International Nuclear Information System (INIS)
Wind power is a renewable energy source that is today the fastest growing solution to reduce CO2 emissions in the electric energy mix. Upwind horizontal axis wind turbine with three blades has been the preferred technical choice for more than two decades. This horizontal axis concept is today widely leading the market. The current PhD thesis will cover an alternative type of wind turbine with straight blades and rotating along the vertical axis. A brief overview of the main differences between the horizontal and vertical axis concept has been made. However the main focus of this thesis is the aerodynamics of the wind turbine blades. Making aerodynamically efficient turbines starts with efficient blades. Making efficient blades requires a good understanding of the physical phenomena and effective simulations tools to model them. The specific aerodynamics for straight bladed vertical axis turbine flow are reviewed together with the standard aerodynamic simulations tools that have been used in the past by blade and rotor designer. A reasonably fast (regarding computer power) and accurate (regarding comparison with experimental results) simulation method was still lacking in the field prior to the current work. This thesis aims at designing such a method. Analytical methods can be used to model complex flow if the geometry is simple. Therefore, a conformal mapping method is derived to transform any set of section into a set of standard circles. Then analytical procedures are generalized to simulate moving multibody sections in the complex vertical flows and forces experienced by the blades. Finally the fast semi analytical aerodynamic algorithm boosted by fast multipole methods to handle high number of vortices is coupled with a simple structural model of the rotor to investigate potential aeroelastic instabilities. Together with these advanced simulation tools, a standard double multiple streamtube model has been developed and used to design several straight bladed
Aerodynamic Analysis of Multistage Turbomachinery Flows in Support of Aerodynamic Design
Adamczyk, John J.
1999-01-01
This paper summarizes the state of 3D CFD based models of the time average flow field within axial flow multistage turbomachines. Emphasis is placed on models which are compatible with the industrial design environment and those models which offer the potential of providing credible results at both design and off-design operating conditions. The need to develop models which are free of aerodynamic input from semi-empirical design systems is stressed. The accuracy of such models is shown to be dependent upon their ability to account for the unsteady flow environment in multistage turbomachinery. The relevant flow physics associated with some of the unsteady flow processes present in axial flow multistage machinery are presented along with procedures which can be used to account for them in 3D CFD simulations. Sample results are presented for both axial flow compressors and axial flow turbines which help to illustrate the enhanced predictive capabilities afforded by including these procedures in 3D CFD simulations. Finally, suggestions are given for future work on the development of time average flow models.
Advanced Electric Systems and Aerodynamics for Efficiency Improvements in Heavy Duty Trucks
Energy Technology Data Exchange (ETDEWEB)
Larry Slone; Jeffrey Birkel
2007-10-31
The Advanced Electric Systems and Aerodynamics for Efficiency Improvements in Heavy Duty Trucks program (DE-FC26-04NT42189), commonly referred to as the AES program, focused on areas that will primarily benefit fuel economy and improve heat rejection while driving over the road. The AES program objectives were to: (1) Analyze, design, build, and test a cooling system that provided a minimum of 10 percent greater heat rejection in the same frontal area with no increase in parasitic fan load. (2) Realize fuel savings with advanced power management and acceleration assist by utilizing an integrated starter/generator (ISG) and energy storage devices. (3) Quantify the effect of aerodynamic drag due to the frontal shape mandated by the area required for the cooling system. The program effort consisted of modeling and designing components for optimum fuel efficiency, completing fabrication of necessary components, integrating these components into the chassis test bed, completing controls programming, and performance testing the system both on a chassis dynamometer and on the road. Emission control measures for heavy-duty engines have resulted in increased engine heat loads, thus introducing added parasitic engine cooling loads. Truck electrification, in the form of thermal management, offers technological solutions to mitigate or even neutralize the effects of this trend. Thermal control offers opportunities to avoid increases in cooling system frontal area and forestall reduced fuel economy brought about by additional aerodynamic vehicle drag. This project explored such thermal concepts by installing a 2007 engine that is compliant with current regulations and bears additional heat rejection associated with meeting these regulations. This newer engine replaced the 2002 engine from a previous project that generated less heat rejection. Advanced power management, utilizing a continuously optimized and controlled power flow between electric components, can offer additional
Metal-wool heat shields for space shuttle. [design, fabrication, and attachment to structure
Miller, R. C.; Clure, J. L.
1974-01-01
The packaging of metal wool for reusable thermal heat shields applied to aerodynamic and other surfaces for the space shuttle was analyzed and designed, and samples were fabricated and experimentally studied. Parametric trends were prepared for selected configurations. An all-metal thermally efficient, reliable, reusable and producible heat shield system was designed and structurally tested for use on spacecraft aerodynamic surfaces where temperatures do not exceed 810 K. Stainless steel sheet, primarily for structure and secondarily in the transverse plane for thermal expansion, was shown to accommodate thermal expansion in all directions when restrained at the edges and heated to 1360 K. Aerodynamic loads of 0.35 x 1000,000 newtons/sq meter, and higher, may be easily accepted by structures of this design. Seven all-metal thermal protection specimens, 12.7 cm square and 2.5 cm thick were fabricated and are being experimentally evaluated at simulated shuttle entry conditions in an arc jet facility.
Study on Aerodynamic Design Optimization of Turbomachinery Blades
Institute of Scientific and Technical Information of China (English)
Naixing CHEN; Hongwu ZHANG; Weiguang HUANG; Yanji XU
2005-01-01
This paper describes the study on aerodynamics design optimization of turbomachinery blading developed by the authors at the Institute of Engineering Thermophysics, Chinese Academy of Sciences, during the recent few years. The present paper describes the aspects mainly on how to use a rapid approach of profiling a 3D blading and of grid generation for computation, a fast and accurate viscous computation method and an appropriate optimization methodology_ including a blade parameterization algorithm to optimize turbomachinery blading aerodynamically. Any blade configuration can be expressed by three curves, they are the camber lines, the thickness distributions and the radial stacking line, and then the blade geometry can be easily parameterized by a number of parameters with three polynomials. A gradient-based parameterization analytical method and a response surface method were applied herein for blade optimization. It was found that the optimization process provides reliable design for turbomachinery with reasonable computing time.
Sparse Sensing of Aerodynamic Loads on Insect Wings
Manohar, Krithika; Brunton, Steven; Kutz, J. Nathan
2015-11-01
We investigate how insects use sparse sensors on their wings to detect aerodynamic loading and wing deformation using a coupled fluid-structure model given periodically flapping input motion. Recent observations suggest that insects collect sensor information about their wing deformation to inform control actions for maneuvering and rejecting gust disturbances. Given a small number of point measurements of the chordwise aerodynamic loads from the sparse sensors, we reconstruct the entire chordwise loading using sparsesensing - a signal processing technique that reconstructs a signal from a small number of measurements using l1 norm minimization of sparse modal coefficients in some basis. We compare reconstructions from sensors randomly sampled from probability distributions biased toward different regions along the wing chord. In this manner, we determine the preferred regions along the chord for sensor placement and for estimating chordwise loads to inform control decisions in flight.
Aerodynamic characteristics research on wide-speed range waverider configuration
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Waverider generated from a given flow field has a high lift-to-drag ratio because of attached bow shock on leading edge. However, leading edge blunt and off-design condition can make bow shock off leading edge and have unfavorable influence on aerodynamic characteristics. So these two problems have always been concerned as important engineering science issues by aeronautical engineering scientists. In this paper, through respectively using low speed and high speed waverider design principles, a wide-speed rang vehicle is designed, which can level takeoff and accelerate to hypersonic speed for cruise. In addition, sharp leading edge is blunted to alleviated aeroheating. Theoretical study and wind tunnel test show that this vehicle has good aerodynamic performance in wide-speed range of subsonic, transonic, supersonic and hypersonic speeds.
Aerodynamic Database Development for Mars Smart Lander Vehicle Configurations
Bobskill, Glenn J.; Parikh, Paresh C.; Prabhu, Ramadas K.; Tyler, Erik D.
2002-01-01
An aerodynamic database has been generated for the Mars Smart Lander Shelf-All configuration using computational fluid dynamics (CFD) simulations. Three different CFD codes, USM3D and FELISA, based on unstructured grid technology and LAURA, an established and validated structured CFD code, were used. As part of this database development, the results for the Mars continuum were validated with experimental data and comparisons made where applicable. The validation of USM3D and LAURA with the Unitary experimental data, the use of intermediate LAURA check analyses, as well as the validation of FELISA with the Mach 6 CF(sub 4) experimental data provided a higher confidence in the ability for CFD to provide aerodynamic data in order to determine the static trim characteristics for longitudinal stability. The analyses of the noncontinuum regime showed the existence of multiple trim angles of attack that can be unstable or stable trim points. This information is needed to design guidance controller throughout the trajectory.
TRO-2D - A code for rational transonic aerodynamic optimization
Davis, W. H., Jr.
1985-01-01
Features and sample applications of the transonic rational optimization (TRO-2D) code are outlined. TRO-2D includes the airfoil analysis code FLO-36, the CONMIN optimization code and a rational approach to defining aero-function shapes for geometry modification. The program is part of an effort to develop an aerodynamically smart optimizer that will simplify and shorten the design process. The user has a selection of drag minimization and associated minimum lift, moment, and the pressure distribution, a choice among 14 resident aero-function shapes, and options on aerodynamic and geometric constraints. Design variables such as the angle of attack, leading edge radius and camber, shock strength and movement, supersonic pressure plateau control, etc., are discussed. The results of calculations of a reduced leading edge camber transonic airfoil and an airfoil with a natural laminar flow are provided, showing that only four design variables need be specified to obtain satisfactory results.
Aerodynamic force coefficients of plain bridge cables in wet conditions
DEFF Research Database (Denmark)
Matteoni, Giulia; Georgakis, Christos T.
In this paper, the aerodynamic forces and force coefficients from preliminary static wind tunnel tests on a plain cable in wet conditions are presented. The presented results are for several different relative cable wind-angles. A comparison is made with tests in dry conditions. In dry conditions...... aerodynamic damping. Analysis of the fluctuating lift component shows the presence of “enhanced” vortex shedding at specific wind velocities – similar to what might be observed in the presence of a tripping wire......., tests were performed for wind velocities between 2 and 31 m/s, whilst in wet conditions tests were performed for the range of wind velocities where rain rivulet formation was found possible, i.e. between 8-18 m/s. For all of the tested relative cable-wind angles in wet conditions, a reduction...
Effects of ice accretion on the aerodynamics of bridge cables
DEFF Research Database (Denmark)
Demartino, C.; Koss, Holger; Georgakis, Christos T.;
2015-01-01
Undesirable wind induced vibrations of bridge cables can occur when atmospheric conditions are such to generate ice accretion. This paper contains the results of an extensive investigation of the effects of ice accretion due to in-cloud icing, on the aerodynamic characteristics of bridge hangers...... of temperature, wind speed and yaw angle of accretion, were reproduced in a climatic wind tunnel, giving rise to different types of accretion. These were chosen such to generate the most common natural ice formations expected to produce bridge cable vibrations. A description of the geometric characteristics...... and stay cables. The aim of this paper is twofold; first, it was investigated the ice accretion process and the final shape of the ice accreted; then the aerodynamics of the ice accreted bridge cables was characterized, and related to the ice shape. Different climatic conditions, i.e. combinations...
Experimental investigation of nanosecond discharge plasma aerodynamic actuation
Institute of Scientific and Technical Information of China (English)
Wu Yun; Li Ying-Hong; Jia Min; Liang Hua; Song Hui-Min
2012-01-01
In this paper we report on an experimental study of the characteristics of nanosecond pulsed discharge plasma aerodynamic actuation. The N2 (C3Ⅱu) rotational and vibrational temperatures are around 430 K and 0.24 eV,respectively. The emission intensity ratio between the first negative system and the second positive system of N2,as a rough indicator of the temporally and spatially averaged electron energy,has a minor dependence on applied voltage amplitude.The induced flow direction is not parallel,but vertical to the dielectric layer surface,as shown by measurements of body force,velocity,and vorticity.Nanosecond discharge plasma aerodynamic actuation is effective in airfoil flow separation control at freestream speeds up to 100 m/s.
Aerodynamic characteristics of missile configurations based on Soviet design concepts
Spearman, M. L.
1979-01-01
The aerodynamic characteristics of several missile concepts are examined. The configurations, which are based on some typical Soviet design concepts, include fixed-wing missiles with either forward- or aft-tail controls, and wing-control missiles with fixed aft stabilizing surfaces. The conceptual missions include air-to-air, surface-to-air, air-to-surface, and surface-to-surface. Analytical and experimental results indicate that through the proper shaping and location of components, and through the exploitation of local flow fields, the concepts provide generally good stability characteristics, high control effectiveness, and low control hinge moments. In addition, in the case of some cruise-type missions, there are indications of the application of area ruling as a means of improving the aerodynamic efficiency. In general, a point-design philosophy is indicated whereby a particular configuration is developed for performing a particular mission.
Aerodynamic Characteristics of Projectile with Exotic Wraparound Wings Configuration
Institute of Scientific and Technical Information of China (English)
Fu Zhang; WenJun Ruan; Hao Wang; ChenGuang Zhu; MengHua Zhang
2014-01-01
A projectile with exotic wraparound wings ( WAW ) configuration is designed to improve the fin-stabilized projectile shooting quality. Two fin-stabilized projectiles with the same body with and without exotic WAW configuration are simulated numerically by applying the Roe scheme. The shear-stress transport turbulence models and the lower-upper symmetric Gauss-Seidel implicit method are used to solve 3D Reynolds-averaged Navier-Stokes equations. The differences in aerodynamic coefficients and aerodynamic characteristics of the projectiles when the Mach number varies from 0�35 to 0�95 are obtained, and the cause of these differences is analyzed. The calculation results indicate that the lift-to-drag ratio of the projectile significantly increases, the rolling moment decreases, and the position of the pressure center of the projectile shows relatively small changes when the exotic WAW configuration is used. Therefore, this projectile can obviously reduce rolling effect, enlarge range and improve flying stability.
Aerodynamic performance of an annular classical airfoil cascade
Bergsten, D. E.; Stauter, R. C.; Fleeter, S.
1983-01-01
Results are presented for a series of experiments that were performed in a large-scale subsonic annular cascade facility that was specifically designed to provide three-dimensional aerodynamic data for the verification of numerical-calculation codes. In particular, the detailed three-dimensional aerodynamic performance of a classical flat-plate airfoil cascade is determined for angles of incidence of 0, 5, and 10 deg. The resulting data are analyzed and are correlated with predictions obtained from NASA's MERIDL and TSONIC numerical programs. It is found that: (1) at 0 and 5 deg, the airfoil surface data show a good correlation with the predictions; (2) at 10 deg, the data are in fair agreement with the numerical predictions; and (3) the two-dimensional Gaussian similarity relationship is appropriate for the wake velocity profiles in the mid-span region of the airfoil.
Influence of a humidor on the aerodynamics of baseballs
Meyer, Edmund R.; Bohn, John L.
2008-11-01
We investigate whether storing baseballs in a controlled humidity environment significantly affects their aerodynamic properties. We measure the change in diameter and weight of baseballs as a function of relative humidity in which the balls are stored. The trajectories of pitched and batted baseballs are modeled to assess the difference between those stored at 30% relative humidity versus 50% relative humidity. We find that a drier baseball will curve slightly more than a humidified one for a given pitch velocity and rotation rate. We also find that aerodynamics alone would add 2ft to the distance a wetter baseball ball is hit. This increased distance is compensated by a 6ft reduction in the batted distance due to the change in the coefficient of restitution of the ball. We discuss consequences of these results for baseball played at Coors Field in Denver, where baseballs have been stored in a humidor at 50% relative humidity since 2002.
Wind turbine aerodynamic response under atmospheric icing conditions
DEFF Research Database (Denmark)
Etemaddar, M.; Hansen, Martin Otto Laver; Moan, T.
2014-01-01
-four hours of icing, with time varying wind speed and atmospheric icing conditions, was simulated on a rotor. Computational fluid dynamics code, FLUENT, was used to estimate the aerodynamic coefficients of the blade after icing. The results were also validated against wind tunnel measurements performed at LM......). However, the thrust of the iced rotor in below rated wind speed is smaller than the clean rotor up to 14%, but after rated wind speed, it is up to 40% bigger than the clean rotor. Finally, it is briefly indicated how the results of this paper can be used for condition monitoring and ice detection......This article deals with the atmospheric ice accumulation on wind turbine blades and its effect on the aerodynamic performance and structural response. The role of eight atmospheric and system parameters on the ice accretion profiles was estimated using the 2D ice accumulation software lewice Twenty...
Parameterization adaption for 3D shape optimization in aerodynamics
Directory of Open Access Journals (Sweden)
Badr Abou El Majd
2013-10-01
Full Text Available When solving a PDE problem numerically, a certain mesh-refinement process is always implicit, and very classically, mesh adaptivity is a very effective means to accelerate grid convergence. Similarly, when optimizing a shape by means of an explicit geometrical representation, it is natural to seek for an analogous concept of parameterization adaptivity. We propose here an adaptive parameterization for three-dimensional optimum design in aerodynamics by using the so-called “Free-Form Deformation” approach based on 3D tensorial Bézier parameterization. The proposed procedure leads to efficient numerical simulations with highly reduced computational costs.[How to cite this article: Majd, B.A.. 2014. Parameterization adaption for 3D shape optimization in aerodynamics. International Journal of Science and Engineering, 6(1:61-69. Doi: 10.12777/ijse.6.1.61-69
BTT autopilot design for agile missiles with aerodynamic uncer tainty
Institute of Scientific and Technical Information of China (English)
Yueyue Ma; Jie Guo; Shengjing Tang
2015-01-01
The approach to the synthesis of autopilot with aerody-namic uncertainty is investigated in order to achieve large maneu-verability of agile missiles. The dynamics of the agile missile with reaction-jet control system (RCS) are presented. Subsequently, the cascade control scheme based on the bank-to-turn (BTT) steering technique is described. To address the aerodynamic un-certainties encountered by the control system, the active distur-bance rejection control (ADRC) method is introduced in the autopi-lot design. Furthermore, a compound control er, using extended state observer (ESO) to online estimate system uncertainties and calculate derivative of command signals, is designed based on dynamic surface control (DSC). Nonlinear simulation results show the feasibility of the proposed approach and validate the robust-ness of the control er with severe unmodeled dynamics.
Aerodynamic Limits on Large Civil Tiltrotor Sizing and Efficiency
Acree, C W., Jr.
2014-01-01
The NASA Large Civil Tiltrotor (2nd generation, or LCTR2) has been the reference design for avariety of NASA studies of design optimization, engine and gearbox technology, handling qualities, andother areas, with contributions from NASA Ames, Glenn and Langley Centers, plus academic and industrystudies. Ongoing work includes airfoil design, 3D blade optimization, engine technology studies, andwingrotor aerodynamic interference. The proposed paper will bring the design up to date with the latestresults of such studies, then explore the limits of what aerodynamic improvements might hope toaccomplish. The purpose is two-fold: 1) determine where future technology studies might have the greatestpayoff, and 2) establish a stronger basis of comparison for studies of other vehicle configurations andmissions.
AERODYNAMIC OPTIMIZATION DESIGN OF LOW ASPECT RATIO TRANSONIC TURBINE STAGE
Institute of Scientific and Technical Information of China (English)
SONG Liming; LI Jun; FENG Zhenping
2006-01-01
The advanced optimization method named as adaptive range differential evolution (ARDE)is developed. The optimization performance of ARDE is demonstrated using a typical mathematical test and compared with the standard genetic algorithm and differential evolution. Combined with parallel ARDE, surface modeling method and Navier-Stokes solution, a new automatic aerodynamic optimization method is presented. A low aspect ratio transonic turbine stage is optimized for the maximization of the isentropic efficiency with forty-one design variables in total. The coarse-grained parallel strategy is applied to accelerate the design process using 15 CPUs. The isentropic efficiency of the optimum design is 1.6% higher than that of the reference design. The aerodynamic performance of the optimal design is much better than that of the reference design.
Aerodynamic optimization by simultaneously updating flow variables and design parameters
Rizk, M. H.
1990-01-01
The application of conventional optimization schemes to aerodynamic design problems leads to inner-outer iterative procedures that are very costly. An alternative approach is presented based on the idea of updating the flow variable iterative solutions and the design parameter iterative solutions simultaneously. Two schemes based on this idea are applied to problems of correcting wind tunnel wall interference and optimizing advanced propeller designs. The first of these schemes is applicable to a limited class of two-design-parameter problems with an equality constraint. It requires the computation of a single flow solution. The second scheme is suitable for application to general aerodynamic problems. It requires the computation of several flow solutions in parallel. In both schemes, the design parameters are updated as the iterative flow solutions evolve. Computations are performed to test the schemes' efficiency, accuracy, and sensitivity to variations in the computational parameters.
Implementation of an aerodynamic lens for TRIGA-SPEC
Grund, J.; Düllmann, Ch. E.; Eberhardt, K.; Nagy, Sz.; van de Laar, J. J. W.; Renisch, D.; Schneider, F.
2016-06-01
We report on the optimization of the gas-jet system employed to couple the TRIGA-SPEC experiment to the research reactor TRIGA Mainz. CdI2 aerosol particles suspended in N2 as carrier gas are used for an effective transport of fission products from neutron induced 235 U fission from the target chamber to a surface ion source. Operating conditions of the gas-jet were modified to enable the implementation of an aerodynamic lens, fitting into the limited space available in front of the ion source. The lens boosts the gas-jet efficiency by a factor of 4-10. The characterization of the gas-jet system as well as the design of the aerodynamic lens and efficiency studies are presented and discussed.
Experimental and Analytical Analysis of Perforated Plate Aerodynamics
Institute of Scientific and Technical Information of China (English)
Jürgen Zierep; Rainer Bohning; Piotr Doerffer
2003-01-01
Perforated walls and transpiration flow play an important role in aerodynamics due to an increasing interest in application of flow control by means of blowing and/or suction. An experimental study was carried out which has led to the determination of a transpiration flow characteristics in the form of a simple formula that is very useful in modelling such flows. In connection to this relation a method of "aerodynamic porosity" determination has been proposed which is much more reliable than geometric description of the porosity. A theoretical analysis of the flow through a perforation hole was also carried out. The flow was considered as compressible and viscous. The gasdynamic analysis led us to a very similar result to the relation obtained from the experiment. The adequacy of the theoretical result is discussed in respect to the experiment.
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Description of an aerodynamic levitation apparatus with applications in Earth sciences
Directory of Open Access Journals (Sweden)
Simon Klaus
2010-09-01
Full Text Available Abstract Background In aerodynamic levitation, solids and liquids are floated in a vertical gas stream. In combination with CO2-laser heating, containerless melting at high temperature of oxides and silicates is possible. We apply aerodynamic levitation to bulk rocks in preparation for microchemical analyses, and for evaporation and reduction experiments. Results Liquid silicate droplets (~2 mm were maintained stable in levitation using a nozzle with a 0.8 mm bore and an opening angle of 60°. The gas flow was ~250 ml min-1. Rock powders were melted and homogenized for microchemcial analyses. Laser melting produced chemically homogeneous glass spheres. Only highly (e.g. H2O and moderately volatile components (Na, K were partially lost. The composition of evaporated materials was determined by directly combining levitation and inductively coupled plasma mass spectrometry. It is shown that the evaporated material is composed of Na > K >> Si. Levitation of metal oxide-rich material in a mixture of H2 and Ar resulted in the exsolution of liquid metal. Conclusions Levitation melting is a rapid technique or for the preparation of bulk rock powders for major, minor and trace element analysis. With exception of moderately volatile elements Na and K, bulk rock analyses can be performed with an uncertainty of ± 5% relative. The technique has great potential for the quantitative determination of evaporated materials from silicate melts. Reduction of oxides to metal is a means for the extraction and analysis of siderophile elements from silicates and can be used to better understand the origin of chondritic metal.
Aerodynamic roughness of glacial ice surfaces derived from high-resolution topographic data
Smith, Mark W.; Quincey, Duncan J.; Dixon, Timothy; Bingham, Robert G.; Carrivick, Jonathan L.; Irvine-Fynn, Tristram D. L.; Rippin, David M.
2016-04-01
This paper presents new methods of estimating the aerodynamic roughness (z0) of glacier ice directly from three-dimensional point clouds and digital elevation models (DEMs), examines temporal variability of z0, and presents the first fully distributed map of z0 estimates across the ablation zone of an Arctic glacier. The aerodynamic roughness of glacier ice surfaces is an important component of energy balance models and meltwater runoff estimates through its influence on turbulent fluxes of latent and sensible heat. In a warming climate these fluxes are predicted to become more significant in contributing to overall melt volumes. Ice z0 is commonly estimated from measurements of ice surface microtopography, typically from topographic profiles taken perpendicular to the prevailing wind direction. Recent advances in surveying permit rapid acquisition of high-resolution topographic data allowing revision of assumptions underlying conventional z0 measurement. Using Structure from Motion (SfM) photogrammetry with Multi-View Stereo (MVS) to survey ice surfaces with millimeter-scale accuracy, z0 variation over 3 orders of magnitude was observed. Different surface types demonstrated different temporal trajectories in z0 through 3 days of intense melt. A glacier-scale 2 m resolution DEM was obtained through terrestrial laser scanning (TLS), and subgrid roughness was significantly related to plot-scale z0. Thus, we show for the first time that glacier-scale TLS or SfM-MVS surveys can characterize z0 variability over a glacier surface potentially leading to distributed representations of z0 in surface energy balance models.
Flight in slow motion: aerodynamics of the pterosaur wing
Palmer, Colin
2010-01-01
The flight of pterosaurs and the extreme sizes of some taxa have long perplexed evolutionary biologists. Past reconstructions of flight capability were handicapped by the available aerodynamic data, which was unrepresentative of possible pterosaur wing profiles. I report wind tunnel tests on a range of possible pterosaur wing sections and quantify the likely performance for the first time. These sections have substantially higher profile drag and maximum lift coefficients than those assumed b...
Aerodynamic Classification of Swept-Wing Ice Accretion
Diebold, Jeff M.; Broeren, Andy P.; Bragg, Michael B.
2013-01-01
The continued design, certification and safe operation of swept-wing airplanes in icing conditions rely on the advancement of computational and experimental simulation methods for higher fidelity results over an increasing range of aircraft configurations and performance, and icing conditions. The current stateof- the-art in icing aerodynamics is mainly built upon a comprehensive understanding of two-dimensional geometries that does not currently exist for fundamentally three-dimensional geometries such as swept wings. The purpose of this report is to describe what is known of iced-swept-wing aerodynamics and to identify the type of research that is required to improve the current understanding. Following the method used in a previous review of iced-airfoil aerodynamics, this report proposes a classification of swept-wing ice accretion into four groups based upon unique flowfield attributes. These four groups are: ice roughness, horn ice, streamwise ice and spanwise-ridge ice. In the case of horn ice it is shown that a further subclassification of "nominally 3D" or "highly 3D" horn ice may be necessary. For all of the proposed ice-shape classifications, relatively little is known about the three-dimensional flowfield and even less about the effect of Reynolds number and Mach number on these flowfields. The classifications and supporting data presented in this report can serve as a starting point as new research explores swept-wing aerodynamics with ice shapes. As further results are available, it is expected that these classifications will need to be updated and revised.
Missile autopilot design considering uncertainties in aerodynamics and actuator dynamics
Song, Yong D.; Hou, J.; Fogson, F.
2000-07-01
This work presents a method for missile autopilot design in the presence of actuator and uncertain dynamics. Nonlinear control algorithms are derived based on both missile aerodynamics and actuator dynamics. To account for system nonlinearities and uncertainties due to varying flight conditions, a memory-based compensation unit is developed and integrated into the strategy. Simulation on EMRAAT missile validates the effectiveness of the proposed control method.
Advanced Modelling of Helicopter Nonlinear Dynamics and Aerodynamics
Castillo-Rivera, Salvador
2014-01-01
The work presented here provides a comprehensive dynamic and aerodynamic helicopter model. The possible applications of this work are wide including, control systems applications, reference and trajectory tracking methods implementation amongst others. The model configuration corresponds to a Sikorsky helicopter; a main rotor in perpendicular combination with a tail rotor. Also, a particular model of unmanned aerial vehicle has been modelled as part of collaboration with the La Laguna Univers...
Review of computational fluid dynamics for wind turbine wake aerodynamics
Sanderse, Benjamin; Pijl, van der, W.; Koren, Barry
2011-01-01
This article reviews the state-of-the-art numerical calculation of wind turbine wake aerodynamics. Different computational fluid dynamics techniques for modeling the rotor and the wake are discussed. Regarding rotor modeling, recent advances in the generalized actuator approach and the direct model are discussed, as far as it attributes to the wake description. For the wake, the focus is on the different turbulence models that are employed to study wake effects on downstream turbines.
Quasi-3d aerodynamic code for analyzing dynamic flap response
Ramos García, Néstor; Sørensen, Jens Nørkær; Shen, Wen Zhong
2011-01-01
A computational model for predicting the aerodynamic behavior of wind turbine airfoil profiles subjected to steady and unsteady motions has been developed. The model is based on a viscous-inviscid interaction technique using strong coupling between the viscous and inviscid parts. The inviscid part is modeled using a panel method whereas the viscous part is modeled by using the integral form of the the laminar and turbulent boundary layer equations and with extensions for 3-D rotational effect...
Aerodynamic assessment of humpback whale ventral fin shapes
Rita Espasa, Damià
2011-01-01
The ventral fins of the humpback whale (Megaptera novaeangliae) include a bulbous leading edge acting as a natural high-lift device. It has been suggested that application of this concept to wing design may yield advantages over traditional shapes (Miklosovic, et al., 2004). During the course of this project, the aerodynamic performance of whale fin models will be compared with conventional wing shapes. Based on the results of the study new wing design paradigms will be developed to improve t...
Aerodynamic focusing of particles and heavy molecules: First annual report
International Nuclear Information System (INIS)
Our first goal was to investigate the phenomenon of aerodynamic focusing in supersonic free jets, in order to assess its potential technological uses in /open quotes/direct writing/close quotes/ and other energy-related applications. Our research program divides itself naturally into two chapters: on focusing microscopic particles, and on focusing individual molecules of heavy vapors carried in jets of He and H2. In both lines we combine diverse experimental and theoretical methods of attack. 3 refs., 4 figs
Differential Reynolds stress modeling for separating flows in industrial aerodynamics
2015-01-01
This book presents recent progress in the application of RANS turbulence models based on the Reynolds stress transport equations. A variety of models has been implemented by different groups into different flow solvers and applied to external as well as to turbomachinery flows. Comparisons between the models allow an assessment of their performance in different flow conditions. The results demonstrate the general applicability of differential Reynolds stress models to separating flows in industrial aerodynamics.
Lateral aerodynamic characteristics of motor vehicles in transient crosswinds
Cairns, Robert Stuart
1994-01-01
Motor car crosswind stability can be adversely affected by reductions in both vehicle mass and drag coefficient. As these are two likely results of future developments the importance of research into vehicle aerodynamic stability is set to increase, moreover, there is evidence that transient effects will be the critical. An experimental facility has been designed and constructed and tests have been carried out to investigate the implications of simulating dynamic flow-fields. Vehicle models o...
Analysis of Aerodynamic Noise Generated from Inclined Circular Cylinder
Institute of Scientific and Technical Information of China (English)
YasutakeHaramoto; ShoujiYasuda; 等
2000-01-01
Making clear the generation mechanism of fluid dynamic noise is essential to reduce noise deriving from turbomachinery.The analysis of the aerodynamic noise generated from circular cylinder is carried out numerically and experimentally in a low noise wind tunnel.in this study,aerodynamic sound radiated from a circular cylinder in uniform flow is predicted numericaslly by the following two step method,First,the three-dimensional unsteady incompressible Navier-Stokes equation is solved using the high order accurate upwind scheme.Next.the sound pressure level at the observed point is calculated from the fluctuating surface pressure on the cylinder.based on modified Lighthill-Curl's equation.It is worth to note that the noise generated from the model is reduced rapidly when it is inclined against the mean flow.In other works,the Peak level of the radiated noise decreases apidly with inclination of the circular cylinder.The simulated SPL for the inclined circular cylinder is compared with the measured value .and good agreement is obtained for the peak spectrum fequency of the sound pressue level and tendency of noise reduction,So we expect that the change of flow structures makes reduction of the aerodynamic noise from the inclined models.
EBF noise suppression and aerodynamic penalties. [Externally Blown Flaps
Mckinzie, L. J., Jr.
1978-01-01
Acoustic tests were conducted at model scale to determine the noise produced in the flyover and sideline planes at reduced separation distances between the nozzle exhaust plane and the flaps of an under-the-wing (UTW) externally blown flap (EBF) configuration in its approach attitude. Tests were also made to determine the noise suppression effectiveness of two types of passive devices which were located on the jet impingement surfaces of the configuration. In addition, static aerodynamic performance data were obtained to evaluate the penalties produced by these suppression devices. Broadband low frequency noise reductions were achieved by reducing the separation distance between the nozzle and flaps. However, mid and high frequency noise was produced which exceeded that of the reference configuration. Two passive noise suppression devices located on the flaps produced moderate to large noise reductions at reduced separation distances. Consideration of the static aerodynamic performance data obtained for the configurations tested suggests that specific broadband noise suppression characteristics may be obtained through a trade-off with aerodynamic performance penalties by the careful selection of suppression devices.
Proper Orthogonal Decomposition as Surrogate Model for Aerodynamic Optimization
Directory of Open Access Journals (Sweden)
Valentina Dolci
2016-01-01
Full Text Available A surrogate model based on the proper orthogonal decomposition is developed in order to enable fast and reliable evaluations of aerodynamic fields. The proposed method is applied to subsonic turbulent flows and the proper orthogonal decomposition is based on an ensemble of high-fidelity computations. For the construction of the ensemble, fractional and full factorial planes together with central composite design-of-experiment strategies are applied. For the continuous representation of the projection coefficients in the parameter space, response surface methods are employed. Three case studies are presented. In the first case, the boundary shape of the problem is deformed and the flow past a backward facing step with variable step slope is studied. In the second case, a two-dimensional flow past a NACA 0012 airfoil is considered and the surrogate model is constructed in the (Mach, angle of attack parameter space. In the last case, the aerodynamic optimization of an automotive shape is considered. The results demonstrate how a reduced-order model based on the proper orthogonal decomposition applied to a small number of high-fidelity solutions can be used to generate aerodynamic data with good accuracy at a low cost.
Parameterization of Vegetation Aerodynamic Roughness of Natural Regions Satellite Imagery
Jasinski, Michael F.; Crago, Richard; Stewart, Pamela
1998-01-01
Parameterizations of the frontal area index and canopy area index of natural or randomly distributed plants are developed, and applied to the estimation of local aerodynamic roughness using satellite imagery. The formulas are expressed in terms of the subpixel fractional vegetation cover and one non-dimensional geometric parameter that characterizes the plant's shape. Geometrically similar plants and Poisson distributed plant centers are assumed. An appropriate averaging technique to extend satellite pixel-scale estimates to larger scales is provided. The parameterization is applied to the estimation of aerodynamic roughness using satellite imagery for a 2.3 sq km coniferous portion of the Landes Forest near Lubbon, France, during the 1986 HAPEX-Mobilhy Experiment. The canopy area index is estimated first for each pixel in the scene based on previous estimates of fractional cover obtained using Landsat Thematic Mapper imagery. Next, the results are incorporated into Raupach's (1992, 1994) analytical formulas for momentum roughness and zero-plane displacement height. The estimates compare reasonably well to reference values determined from measurements taken during the experiment and to published literature values. The approach offers the potential for estimating regionally variable, vegetation aerodynamic roughness lengths over natural regions using satellite imagery when there exists only limited knowledge of the vegetated surface.
The Mechanical Impact of Aerodynamic Stall on Tunnel Ventilation Fans
Directory of Open Access Journals (Sweden)
A. G. Sheard
2012-01-01
Full Text Available This paper describes work aimed at establishing the ability of a tunnel ventilation fan to operate without risk of mechanical failure in the event of aerodynamic stall. The research establishes the aerodynamic characteristics of a typical tunnel ventilation fan when operated in both stable and stalled aerodynamic conditions, with and without an anti-stall stabilisation ring, with and without a “nonstalling” blade angle and at full, half, and one quarter design speed. It also measures the fan’s peak stress, thus facilitating an analysis of the implications of the experimental results for mechanical design methodology. The paper concludes by presenting three different strategies for tunnel ventilation fan selection in applications where the selected fan will most likely stall. The first strategy selects a fan with a low-blade angle that is nonstalling. The second strategy selects a fan with a high-pressure developing capability. The third strategy selects a fan with a fitted stabilisation ring. Tunnel ventilation system designers each have their favoured fan selection strategy. However, all three strategies can produce system designs within which a tunnel ventilation fan performs reliably in-service. The paper considers the advantages and disadvantages of each selection strategy and considered the strengths and weaknesses of each.
Wing Flexion and Aerodynamics Performance of Insect Free Flights
Dong, Haibo; Liang, Zongxian; Ren, Yan
2010-11-01
Wing flexion in flapping flight is a hallmark of insect flight. It is widely thought that wing flexibility and wing deformation would potentially provide new aerodynamic mechanisms of aerodynamic force productions over completely rigid wings. However, there are lack of literatures on studying fluid dynamics of freely flying insects due to the presence of complex shaped moving boundaries in the flow domain. In this work, a computational study of freely flying insects is being conducted. High resolution, high speed videos of freely flying dragonflies and damselflies is obtained and used as a basis for developing high fidelity geometrical models of the dragonfly body and wings. 3D surface reconstruction technologies are used to obtain wing topologies and kinematics. The wing motions are highly complex and a number of different strategies including singular vector decomposition of the wing kinematics are used to examine the various kinematical features and their impact on the wing performance. Simulations are carried out to examine the aerodynamic performance of all four wings and understand the wake structures of such wings.
Numerical simulation of the tip aerodynamics and acoustics test
Tejero E, F.; Doerffer, P.; Szulc, O.; Cross, J. L.
2016-04-01
The application of an efficient flow control system on helicopter rotor blades may lead to improved aerodynamic performance. Recently, our invention of Rod Vortex Generators (RVGs) has been analyzed for helicopter rotor blades in hover with success. As a step forward, the study has been extended to forward flight conditions. For this reason, a validation of the numerical modelling for a reference helicopter rotor (without flow control) is needed. The article presents a study of the flow-field of the AH-1G helicopter rotor in low-, medium- and high-speed forward flight. The CFD code FLOWer from DLR has proven to be a suitable tool for the aerodynamic analysis of the two-bladed rotor without any artificial wake modelling. It solves the URANS equations with LEA (Linear Explicit Algebraic stress) k-ω model using the chimera overlapping grids technique. Validation of the numerical model uses comparison with the detailed flight test data gathered by Cross J. L. and Watts M. E. during the Tip Aerodynamics and Acoustics Test (TAAT) conducted at NASA in 1981. Satisfactory agreements for all speed regimes and a presence of significant flow separation in high-speed forward flight suggest a possible benefit from the future implementation of RVGs. The numerical results based on the URANS approach are presented not only for a popular, low-speed case commonly used in rotorcraft community for CFD codes validation but preferably for medium- and high-speed test conditions that have not been published to date.
Lifting Wing in Constructing Tall Buildings —Aerodynamic Testing
Directory of Open Access Journals (Sweden)
Ian Skelton
2014-05-01
Full Text Available This paper builds on previous research by the authors which determined the global state-of-the-art of constructing tall buildings by surveying the most active specialist tall building professionals around the globe. That research identified the effect of wind on tower cranes as a highly ranked, common critical issue in tall building construction. The research reported here presents a design for a “Lifting Wing,” a uniquely designed shroud which potentially allows the lifting of building materials by a tower crane in higher and more unstable wind conditions, thereby reducing delay on the programmed critical path of a tall building. Wind tunnel tests were undertaken to compare the aerodynamic performance of a scale model of a typical “brick-shaped” construction load (replicating a load profile most commonly lifted via a tower crane against the aerodynamic performance of the scale model of the Lifting Wing in a range of wind conditions. The data indicate that the Lifting Wing improves the aerodynamic performance by a factor of up to 50%.
High angle of attack aerodynamics subsonic, transonic, and supersonic flows
Rom, Josef
1992-01-01
The aerodynamics of aircraft at high angles of attack is a subject which is being pursued diligently, because the modern agile fighter aircraft and many of the current generation of missiles must perform well at very high incidence, near and beyond stall. However, a comprehensive presentation of the methods and results applicable to the studies of the complex aerodynamics at high angle of attack has not been covered in monographs or textbooks. This book is not the usual textbook in that it goes beyond just presenting the basic theoretical and experimental know-how, since it contains reference material to practical calculation methods and technical and experimental results which can be useful to the practicing aerospace engineers and scientists. It can certainly be used as a text and reference book for graduate courses on subjects related to high angles of attack aerodynamics and for topics related to three-dimensional separation in viscous flow courses. In addition, the book is addressed to the aerodynamicist...
Aerodynamic Design Methodology for Blended Wing Body Transport
Institute of Scientific and Technical Information of China (English)
LI Peifeng; ZHANG Binqian; CHEN Yingchun; YUAN Changsheng; LIN Yu
2012-01-01
This paper puts forward a design idea for blended wing body (BWB).The idea is described as that cruise point,maximum lift to drag point and pitch trim point are in the same flight attitude.According to this design idea,design objectives and constraints are defined.By applying low and high fidelity aerodynamic analysis tools,BWB aerodynamic design methodology is established by the combination of optimization design and inverse design methods.High lift to drag ratio,pitch trim and acceptable buffet margin can be achieved by this design methodology.For 300-passenger BWB configuration based on static stability design,as compared with initial configuration,the maximum lift to drag ratio and pitch trim are achieved at cruise condition,zero lift pitching moment is positive,and buffet characteristics is well.Fuel burn of 300-passenger BWB configuration is also significantly reduced as compared with conventional civil transports.Because aerodynamic design is carried out under the constraints of BWB design requirements,the design configuration fulfills the demands for interior layout and provides a solid foundation for continuous work.
Aerodynamic Drag Reduction for Ground Vehicles using Lateral Guide Vanes
Directory of Open Access Journals (Sweden)
Essam Wahba
2012-06-01
Full Text Available The use of lateral guide vanes as a drag reducing device for ground vehicles is numerically investigated in the present study. Two types of ground vehicles are considered, a simplified bus model and a simplified sport utility vehicle (SUV model. The guide vanes are used to direct air into the low-pressure wake region in order to enhance pressure recovery, which in turn would reduce form drag and hence the overall aerodynamic drag. Computational fluid dynamics simulations are used to assess the efficiency of the drag reducing device. The steady-state simulations are based on the Reynolds-averaged Navier-Stokes equations, with turbulence closure provided through two-equation eddy-viscosity models. Guide vane cross-section, chord length and angle of attack are varied in order to obtain the optimal configuration for improved aerodynamic performance. Simulations indicate an overall reduction in the aerodynamic drag coefficient of up to 18% for the bus and SUV models with the use of the lateral guide vanes. Grid-independence tests and comparison with available data in the literature is carried out to validate the present numerical procedure.
Time domain analysis method for aerodynamic noises from wind turbine blades
Directory of Open Access Journals (Sweden)
Hua ZHAO
2015-04-01
Full Text Available The issue of the aerodynamic noises from wind turbine blades affecting the surrounding residents life begins to attract researcher's attention. Most of the existing researches are based on CFD software or experimental data fitting method to analyze the aerodynamic noises, so it is difficult to adapt the demand to dynamic analysis of the aerodynamic noises from wind speed variation. In this paper, the operation parameters, the inflow wind speed and the receiver location are considered, and a modified model to calculate aerodynamic noises from wind turbine blades which is based on traditional acoustic formulas is established. The program to calculate the aerodynamic noises from the 2 MW wind turbine blades is compiled using a time-domain analysis method based on the Simulink modular in Matlab software. And the pressure time sequence diagrams of the aerodynamic noises from wind turbine blades are drawn. It has provided a theoretical foundation to develop low noise wind turbine blades.
Macmichael, DBA
1988-01-01
A fully revised and extended account of the design, manufacture and use of heat pumps in both industrial and domestic applications. Topics covered include a detailed description of the various heat pump cycles, the components of a heat pump system - drive, compressor, heat exchangers etc., and the more practical considerations to be taken into account in their selection.
Full-scale measurements of aerodynamic induction in a rotor plane
Larsen, Gunner Chr.; Hansen, Kurt Schaldemose
2014-01-01
Reliable modelling of aerodynamic induction is imperative for successful prediction of wind turbine loads and wind turbine dynamics when based on state-of- the-art aeroelastic tools. Full-scale LiDAR based wind speed measurements, with high temporal and spatial resolution, have been conducted in the rotor plane of an operating 2MW/80m wind turbine to perform detailed analysis the aerodynamic induction. The experimental setup, analyses of the spatial structure of the aerodynamic induction and ...
Aerodynamic performance of a hovering hawkmoth with flexible wings: a computational approach
Nakata, Toshiyuki; Liu, Hao
2011-01-01
Insect wings are deformable structures that change shape passively and dynamically owing to inertial and aerodynamic forces during flight. It is still unclear how the three-dimensional and passive change of wing kinematics owing to inherent wing flexibility contributes to unsteady aerodynamics and energetics in insect flapping flight. Here, we perform a systematic fluid-structure interaction based analysis on the aerodynamic performance of a hovering hawkmoth, Manduca, with an integrated comp...
Application of CAD/CAE class systems to aerodynamic analysis of electric race cars
Grabowski, L.; Baier, A.; Buchacz, A.; Majzner, M.; Sobek, M.
2015-11-01
Aerodynamics is one of the most important factors which influence on every aspect of a design of a car and car driving parameters. The biggest influence aerodynamics has on design of a shape of a race car body, especially when the main objective of the race is the longest distance driven in period of time, which can not be achieved without low energy consumption and low drag of a car. Designing shape of the vehicle body that must generate the lowest possible drag force, without compromising the other parameters of the drive. In the article entitled „Application of CAD/CAE class systems to aerodynamic analysis of electric race cars” are being presented problems solved by computer analysis of cars aerodynamics and free form modelling. Analysis have been subjected to existing race car of a Silesian Greenpower Race Team. On a basis of results of analysis of existence of Kammback aerodynamic effect innovative car body were modeled. Afterwards aerodynamic analysis were performed to verify existence of aerodynamic effect for innovative shape and to recognize aerodynamics parameters of the shape. Analysis results in the values of coefficients and aerodynamic drag forces. The resulting drag forces Fx, drag coefficients Cx(Cd) and aerodynamic factors Cx*A allowed to compare all of the shapes to each other. Pressure distribution, air velocities and streams courses were useful in determining aerodynamic features of analyzed shape. For aerodynamic tests was used Ansys Fluent CFD software. In a paper the ways of surface modeling with usage of Realize Shape module and classic surface modeling were presented. For shapes modeling Siemens NX 9.0 software was used. Obtained results were used to estimation of existing shapes and to make appropriate conclusions.
Flegel, Ashlie B.; Welch, Gerard E.; Giel, Paul W.; Ames, Forrest E.; Long, Jonathon A.
2015-01-01
Two independent experimental studies were conducted in linear cascades on a scaled, two-dimensional mid-span section of a representative Variable Speed Power Turbine (VSPT) blade. The purpose of these studies was to assess the aerodynamic performance of the VSPT blade over large Reynolds number and incidence angle ranges. The influence of inlet turbulence intensity was also investigated. The tests were carried out in the NASA Glenn Research Center Transonic Turbine Blade Cascade Facility and at the University of North Dakota (UND) High Speed Compressible Flow Wind Tunnel Facility. A large database was developed by acquiring total pressure and exit angle surveys and blade loading data for ten incidence angles ranging from +15.8deg to -51.0deg. Data were acquired over six flow conditions with exit isentropic Reynolds number ranging from 0.05×106 to 2.12×106 and at exit Mach numbers of 0.72 (design) and 0.35. Flow conditions were examined within the respective facility constraints. The survey data were integrated to determine average exit total-pressure and flow angle. UND also acquired blade surface heat transfer data at two flow conditions across the entire incidence angle range aimed at quantifying transitional flow behavior on the blade. Comparisons of the aerodynamic datasets were made for three "match point" conditions. The blade loading data at the match point conditions show good agreement between the facilities. This report shows comparisons of other data and highlights the unique contributions of the two facilities. The datasets are being used to advance understanding of the aerodynamic challenges associated with maintaining efficient power turbine operation over a wide shaft-speed range.
National Aeronautics and Space Administration — ZONA Technology proposes to develop an innovative nonlinear structural reduced order model (ROM) - nonlinear aerodynamic ROM methodology for the inflatable...
National Aeronautics and Space Administration — This proposal defines innovative aerodynamic concepts and technology goals aimed at vehicle efficiency for future subsonic aircraft in the 2020 ? 2030 timeframe....
The design of missile's dome that fits both optical and aerodynamic needs
Wei, Qun; Zhang, Xin; Jia, Hongguang
2010-10-01
Optical guidance missiles requires a dome which fits both optical and aerodynamic needs when they attack at 3 Ma. In this study, ellipse is the figure chosen to be the dome's shape. The ellipticity ɛ is the main variable should to be decided. The optimized function was built by optical and aerodynamic performance function multiply by their weights. The optical and aerodynamic functions were all obtained by computational fluid dynamic (CFD) simulation's results after normalization. In this study, the optical and aerodynamic performances have equal weights, after optimzing the ellipticity ɛis 2 for the missile.
Institute of Scientific and Technical Information of China (English)
Tang Zhili; Dong Jun
2009-01-01
complete and complete decisions of the leader and followers respectively. Several design examples illustrate the efficiency of the coupling algorithms for multi-criterion aerodynamic design optimization problems.
Dill, C. C.; Young, J. C.; Roberts, B. B.; Craig, M. K.; Hamilton, J. T.; Boyle, W. W.
1985-01-01
The phase B Space Shuttle systems definition studies resulted in a generic configuration consisting of a delta wing orbiter, and two solid rocket boosters (SRB) attached to an external fuel tank (ET). The initial challenge facing the aerodynamic community was aerodynamically optimizing, within limits, this configuration. As the Shuttle program developed and the sensitivities of the vehicle to aerodynamics were better understood the requirements of the aerodynamic data base grew. Adequately characterizing the vehicle to support the various design studies exploded the size of the data base to proportions that created a data modeling/management challenge for the aerodynamicist. The ascent aerodynamic data base originated primarily from wind tunnel test results. The complexity of the configuration rendered conventional analytic methods of little use. Initial wind tunnel tests provided results which included undesirable effects from model support tructure, inadequate element proximity, and inadequate plume simulation. The challenge to improve the quality of test results by determining the extent of these undesirable effects and subsequently develop testing techniques to eliminate them was imposed on the aerodynamic community. The challenges to the ascent aerodynamics community documented are unique due to the aerodynamic complexity of the Shuttle launch. Never before was such a complex vehicle aerodynamically characterized. The challenges were met with innovative engineering analyses/methodology development and wind tunnel testing techniques.
Single annular combustor: Experimental investigations of aerodynamics, dynamics and emissions
Mohammad, Bassam Sabry
The present work investigates the aerodynamics, dynamics and emissions of a Single Cup Combustor Sector. The Combustor resembles a real Gas Turbine Combustor with primary, secondary and dilution zones (also known as fuel rich dome combustor). The research is initiated by studying the effect of the combustor front end geometry on the flow field. Two different exit configurations (one causes a sudden expansion to the swirling flow while the other causes a gradual expansion), installed in a dump combustor, are tested using LDV. The results reveal that the expanding surface reduces the turbulence activities, eliminates the corner recirculation zone and increases the length of the CRZ appreciably. An asymmetry in the flow field is observed due to the asymmetry of the expanding surface. To study the effect of chamber geometry on the flow field, the dome configuration is tested in the combustor sector with the primary dilution jets blocked. The size of the CRZ is reduced significantly (40% reduction in the height). With active primary jets, the CRZ is reconstructed in 3D by conducting several PIV measurements off-center. The confinement appears to significantly influence the shape of the CRZ such that the area ratio is similar for both the confinement and the CRZ (approximately 85%). The primary jets considerably contribute to the heat release process at high power conditions. Also, the primary jets drastically impact the flow field structure. Therefore, the parameters influencing the primary jets are studied using PIV (pressure drop, jets size, off-centering, interaction with convective cooling air, jet blockage and fuel injection). This study is referred to as a jet sensitivity study. The results indicate that the primary jets can be used effectively in controlling the flow field structure. A pressure drop of 4.3% and 7.6% result in similar flows with no noticeable effect on the size of the CRZ and the four jets wake regions. On the other hand, the results show that the
Aerodynamic size associations of natural radioactivity with ambient aerosols
Energy Technology Data Exchange (ETDEWEB)
Bondietti, E.A.; Papastefanou, C.; Rangarajan, C.
1986-04-01
The aerodynamic size of /sup 214/Pb, /sup 212/Pb, /sup 210/Pb, /sup 7/Be, /sup 32/P, /sup 35/S (as SO/sub 4//sup 2 -/), and stable SO/sub 4//sup 2 -/ was measured using cascade impactors. The activity distribution of /sup 212/Pb and /sup 214/Pb, measured by alpha spectroscopy, was largely associated with aerosols smaller than 0.52 ..mu..m. Based on 46 measurements, the activity median aerodynamic diameter of /sup 212/Pb averaged 0.13 ..mu..m (sigma/sub g/ = 2.97), while /sup 214/Pb averaged 0.16 ..mu..m (sigma/sub g/ = 2.86). The larger median size of /sup 214/Pb was attributed to ..cap alpha..-recoil depletion of smaller aerosols following decay of aerosol-associated /sup 218/Po. Subsequent /sup 214/Pb condensation on all aerosols effectively enriches larger aerosols. /sup 212/Pb does not undergo this recoil-driven redistribution. Low-pressure impactor measurements indicated that the mass median aerodynamic diameter of SO/sub 4//sup 2 -/ was about three times larger than the activity median diameter /sup 212/Pb, reflecting differences in atmospheric residence times as well as the differences in surface area and volume distributions of the atmospheric aerosol. Cosmogenic radionuclides, especially /sup 7/Be, were associated with smaller aerosols than SO/sub 4//sup 2 -/ regardless of season, while /sup 210/Pb distributions in summer measurements were similar to sulfate but smaller in winter measurements. Even considering recoil following /sup 214/Po ..cap alpha..-decay, the avervage /sup 210/Pb labeled aerosol grows by about a factor of two during its atmospheric lifetime. The presence of 5 to 10% of the /sup 7/Be on aerosols greater than 1 ..mu..m was indicative of post-condensation growth, probably either in the upper atmosphere or after mixing into the boundary layer.
Low Speed Aerodynamics of the X-38 CRV
Komerath, N. M.; Funk, R.; Ames, R. G.; Mahalingam, R.; Matos, C.
1998-01-01
This project was performed in support of the engineering development of the NASA X-38 Crew Return Vehicle (CRV)system. Wind tunnel experiments were used to visualize various aerodynamic phenomena encountered by the CRV during the final stages of descent and landing. Scale models of the CRV were used to visualize vortex structures above and below the vehicle, and in its wake, and to quantify their trajectories. The effect of flaperon deflection on these structures was studied. The structure and dynamics of the CRV's wake during the drag parachute deployment stage were measured. Regions of high vorticity were identified using surveys conducted in several planes using a vortex meter. Periodic shedding of the vortex sheets from the sides of the CRV was observed using laser sheet videography as the CRV reached high angles of attack during the quasi-steady pitch-up prior to parafoil deployment. Using spectral analysis of hot-film anemometer data, the Strouhal number of these wake fluctuations was found to be 0.14 based on the model span. Phenomena encountered in flight test during parafoil operation were captured in scale-model tests, and a video photogrammetry technique was implemented to obtain parafoil surface shapes during flight in the tunnel. Forces on the parafoil were resolved using tension gages on individual lines. The temporal evolution of the phenomenon of leading edge collapse was captured. Laser velocimetry was used to demonstrate measurement of the porosity of the parafoil surface. From these measurements, several physical explanations have been developed for phenomena observed at various stages of the X-38 development program. Quantitative measurement capabilities have also been demonstrated for continued refinement of the aerodynamic technologies employed in the X-38 project. Detailed results from these studies are given in an AIAA Paper, two slide presentations, and other material which are given on a Web-based archival resource. This is the Digital
Aerodynamic Ground Effect in Fruitfly Sized Insect Takeoff.
Directory of Open Access Journals (Sweden)
Dmitry Kolomenskiy
Full Text Available Aerodynamic ground effect in flapping-wing insect flight is of importance to comparative morphologies and of interest to the micro-air-vehicle (MAV community. Recent studies, however, show apparently contradictory results of either some significant extra lift or power savings, or zero ground effect. Here we present a numerical study of fruitfly sized insect takeoff with a specific focus on the significance of leg thrust and wing kinematics. Flapping-wing takeoff is studied using numerical modelling and high performance computing. The aerodynamic forces are calculated using a three-dimensional Navier-Stokes solver based on a pseudo-spectral method with volume penalization. It is coupled with a flight dynamics solver that accounts for the body weight, inertia and the leg thrust, while only having two degrees of freedom: the vertical and the longitudinal horizontal displacement. The natural voluntary takeoff of a fruitfly is considered as reference. The parameters of the model are then varied to explore possible effects of interaction between the flapping-wing model and the ground plane. These modified takeoffs include cases with decreased leg thrust parameter, and/or with periodic wing kinematics, constant body pitch angle. The results show that the ground effect during natural voluntary takeoff is negligible. In the modified takeoffs, when the rate of climb is slow, the difference in the aerodynamic forces due to the interaction with the ground is up to 6%. Surprisingly, depending on the kinematics, the difference is either positive or negative, in contrast to the intuition based on the helicopter theory, which suggests positive excess lift. This effect is attributed to unsteady wing-wake interactions. A similar effect is found during hovering.
Study of Aerodynamic Parameters on Different Underling Surfaces
Institute of Scientific and Technical Information of China (English)
MAO Yuhao; LIU Shuhua; ZHANG Chenyi; LIU Lichao; LI Jing
2007-01-01
Aerodynamic parameters including the zero-plane displacement (d), roughness length (z0), and friction velocity (u*) on the different underlying surfaces of heavy-grazing site, medium-grazing site, light-grazing site, no-grazing site, dune, inter-dune, grassland, rice paddy site, wheat site, soybean site, and maize site have been computed based on the Monin-Obukhov similarity theory by utilizing the micrometeorologically observed data of dune and vegetation in the semi-arid area at Naiman, Inner Mongolia of China, conducted jointly by the Institute of Desert Research, Chinese Academy of Sciences and the National Institute of AgroEnvironmental Sciences of Japan in 1990-1994. And their relationships between wind speed and Richardson number are analyzed. The aerodynamic characteristics of different man-made disturbed grassland ecosystems are also compared. Result shows that the vegetation coverage and the above-ground biomass decrease with the increase in man-made stress of the grassland. The roughness length for different underlying surfaces is closely related to vegetation height, above-ground biomass, and ground surface undulation, and Richardson number Ri is also its influencing factor. The friction velocity varies largely on different underlying surfaces,and it is positively proportional to wind speed and roughness length. The aerodynamic parameters of various times on the same underlying surface are different, too. Above results indicate that grassland and vegetation are of significance in preventing desertification, especially in the arid and semi-arid land ecosystems. And the results of this paper are also important for constructing the land surface physical process as well as regional climate model.
The aerodynamics and control of free flight manoeuvres in Drosophila.
Dickinson, Michael H; Muijres, Florian T
2016-09-26
A firm understanding of how fruit flies hover has emerged over the past two decades, and recent work has focused on the aerodynamic, biomechanical and neurobiological mechanisms that enable them to manoeuvre and resist perturbations. In this review, we describe how flies manipulate wing movement to control their body motion during active manoeuvres, and how these actions are regulated by sensory feedback. We also discuss how the application of control theory is providing new insight into the logic and structure of the circuitry that underlies flight stability.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'. PMID:27528778
Optimization of aerodynamic efficiency for twist morphing MAV wing
N. I. Ismail; A.H. Zulkifli; M.Z. Abdullah; M. Hisyam Basri; Norazharuddin Shah Abdullah
2014-01-01
Twist morphing (TM) is a practical control technique in micro air vehicle (MAV) flight. However, TM wing has a lower aerodynamic efficiency (CL/CD) compared to membrane and rigid wing. This is due to massive drag penalty created on TM wing, which had overwhelmed the successive increase in its lift generation. Therefore, further CL/CDmax optimization on TM wing is needed to obtain the optimal condition for the morphing wing configuration. In this paper, two-way fluid–structure interaction (FSI...
An aerodynamic noise propagation model for wind turbines
DEFF Research Database (Denmark)
Zhu, Wei Jun; Sørensen, Jens Nørkær; Shen, Wen Zhong
2005-01-01
A model based on 2-D sound ray theory for aerodynamic noise propagation from wind turbine rotating blades is introduced. The model includes attenuation factors from geometric spreading, sound directivity of source, air absorption, ground deflection and reflection, as well as effects from...... temperature and airflow. At a given receiver point, the sound pressure is corrected by taking into account these propagation effects. As an overall assumption, the noise field generated by the wind turbine is simplified as a point source placed at the hub height of the wind turbine. This assumtion...
Wake shape and its effects on aerodynamic characteristics
Emdad, H.; Lan, C. E.
1986-01-01
The wake shape under symmetrical flight conditions and its effects on aerodynamic characteristics are examined. In addition, the effect of wake shape in sideslip and discrete vortices such as strake or forebody vortex on lateral characteristics is presented. The present numerical method for airplane configurations, which is based on discretization of the vortex sheet into vortex segments, verified the symmetrical and asymmetrical roll-up process of the trailing vortices. Also, the effect of wing wake on tail planes is calculated. It is concluded that at high lift the assumption of flat wake for longitudinal and lateral-directional characteristics should be reexamined.
Aerodynamic Tests of the Space Launch System for Database Development
Pritchett, Victor E.; Mayle, Melody N.; Blevins, John A.; Crosby, William A.; Purinton, David C.
2014-01-01
The Aerosciences Branch (EV33) at the George C. Marshall Space Flight Center (MSFC) has been responsible for a series of wind tunnel tests on the National Aeronautics and Space Administration's (NASA) Space Launch System (SLS) vehicles. The primary purpose of these tests was to obtain aerodynamic data during the ascent phase and establish databases that can be used by the Guidance, Navigation, and Mission Analysis Branch (EV42) for trajectory simulations. The paper describes the test particulars regarding models and measurements and the facilities used, as well as database preparations.
Aerodynamic investigation of winglets on wind turbine blades using CFD
DEFF Research Database (Denmark)
Johansen, Jeppe; Sørensen, Niels N.
2006-01-01
The present report describes the numerical investigation of the aerodynamics around a wind turbine blade with a winglet using Computational Fluid Dynamics, CFD. Five winglets were investigated with different twist distribution and camber. Four of them were pointing towards the pressure side...... (upstream) and one was pointing towards the suction side (downstream). Additionally, a rectangular modification of the original blade tip was designed with the same planform area as the blades with winglets. Results show that adding a winglet to the existing blade increase the force distribution...
Analyze of aerodynamic forces acting on the Siemens Desiro railcar
Directory of Open Access Journals (Sweden)
Sorin ARSENE
2016-06-01
Full Text Available This paper aims to examine the influence of aerodynamic forces acting on the Siemens Desiro railcar, and the percentage of these forces in the total values of resistance to motion. In this regard the numerical simulation of the airflow is used as a method of analysis. We started from the 3D geometric model at a scale of 1:1 of the vehicle bodywork constructive form. The air flow simulation is performed taking into account the speed limits of the vehicle namely 0 km/ h and 140 km/ h, interval in which eight point values are chosen.
Numerical simulations of synthetic jets in aerodynamic applications
Directory of Open Access Journals (Sweden)
Alexandru Catalin MACOVEI
2014-04-01
Full Text Available This paper presents numerical simulations of synthetic jets in aerodynamic applications. We’ve analyzed the formation of isolated synthetic jets, the influence of nozzle geometry and the interaction of synthetic jets with a uniform flow on a flat plate. Also we’ve studied the influence of the active control in interaction with a stalled airfoil and the controllability of dynamic stall phenomenon. The results are obtained using a dedicated CFD solver. Appropriate comparisons are made with results from scientific literature; as well the numerical results are compared with a set of experimental images.
Variable volume combustor with aerodynamic fuel flanges for nozzle mounting
Energy Technology Data Exchange (ETDEWEB)
McConnaughhay, Johnie Franklin; Keener, Christopher Paul; Johnson, Thomas Edward; Ostebee, Heath Michael
2016-09-20
The present application provides a combustor for use with a gas turbine engine. The combustor may include a number of micro-mixer fuel nozzles and a fuel injection system for providing a flow of fuel to the micro-mixer fuel nozzles. The fuel injection system may include a number of support struts supporting the fuel nozzles and for providing the flow of fuel therethrough. The fuel injection system also may include a number of aerodynamic fuel flanges connecting the micro-mixer fuel nozzles and the support struts.
Aerodynamic Optimum Design of Transonic Turbine Cascades Using Genetic Algorithms
Institute of Scientific and Technical Information of China (English)
无
1997-01-01
This paper presents an aerodynamic optimum design method for transonic turbine cascades based on the Genetic Algorithms coupled to the inviscid flow Euler Solver and the boundary-layer calculation.The Genetic Algorithms control the evolution of a population of cascades towards an optimum design.The fitness value of each string is evaluated using the flow solver.The design procedure has been developed and the behavior of the genetic algorithms has been tested.The objective functions of the design examples are the minimum mean-square deviation between the aimed pressure and computed pressure and the minimum amount of user expertise.
Effect of Moving Surface on NACA 63218 Aerodynamic Performance
Directory of Open Access Journals (Sweden)
Yahiaoui Tayeb
2015-01-01
Full Text Available The main subject of this work is the numerical study control of flow separation on a NACA 63218 airfoil by using moving surface. Different numerical cases are considered: the first one is the numerical simulation of non-modified airfoil NACA 63218 according at different angle of attack and the second one a set of moving cylinder is placed on leading edge of the airfoil. The rotational velocity of the cylinder is varied to establish the effect of momentum injection on modified airfoil aerodynamic performances. The turbulence is modeled by two equations k-epsilon model.
Numerical analysis of aerodynamic noise radiated from cross flow fan
Institute of Scientific and Technical Information of China (English)
Anbang CHEN; Song LI; Dongtao HUANG
2008-01-01
The flow field in a cross flow fan was simulated by solving the 2-D unsteady Reynolds-averaged Navier-Stokes equations. The calculated pressure fluctuations of the blades, the vortex wall, and the rear wall were then used as noise sources to calculate the sound field. The Ffowcs Williams-Hawkings (FW-H) equation was employed to predict the noise field caused by these sources. The predictions show that the rear wall and the vortex wall sources contribute significantly to the total noise and that both the predicted aerodynamic perform-ance and noise agree well with the experimental results.
Prediction of Unsteady Aerodynamic Coefficients at High Angles of Attack
Pamadi, Bandu N.; Murphy, Patrick C.; Klein, Vladislav; Brandon, Jay M.
2001-01-01
The nonlinear indicial response method is used to model the unsteady aerodynamic coefficients in the low speed longitudinal oscillatory wind tunnel test data of the 0.1 scale model of the F-16XL aircraft. Exponential functions are used to approximate the deficiency function in the indicial response. Using one set of oscillatory wind tunnel data and parameter identification method, the unknown parameters in the exponential functions are estimated. The genetic algorithm is used as a least square minimizing algorithm. The assumed model structures and parameter estimates are validated by comparing the predictions with other sets of available oscillatory wind tunnel test data.
Exploring bird aerodynamics using radio-controlled models
Energy Technology Data Exchange (ETDEWEB)
Hoey, Robert G, E-mail: bobh@antelecom.ne [Air Force Flight Test Center, Edwards AFB, CA (United States)
2010-12-15
A series of radio-controlled glider models was constructed by duplicating the aerodynamic shape of soaring birds (raven, turkey vulture, seagull and pelican). Controlled tests were conducted to determine the level of longitudinal and lateral-directional static stability, and to identify the characteristics that allowed flight without a vertical tail. The use of tail-tilt for controlling small bank-angle changes, as observed in soaring birds, was verified. Subsequent tests, using wing-tip ailerons, inferred that birds use a three-dimensional flow pattern around the wing tip (wing tip vortices) to control adverse yaw and to create a small amount of forward thrust in gliding flight.
Aerodynamic design and analysis of a highly loaded turbine exhaust
Huber, F. W.; Montesdeoca, X. A.; Rowey, R. J.
1993-01-01
The aerodynamic design and analysis of a turbine exhaust volute manifold is described. This turbine exhaust system will be used with an advanced gas generator oxidizer turbine designed for very high specific work. The elevated turbine stage loading results in increased discharge Mach number and swirl velocity which, along with the need for minimal circumferential variation of fluid properties at the turbine exit, represent challenging volute design requirements. The design approach, candidate geometries analyzed, and steady state/unsteady CFD analysis results are presented.
Resonances and Aerodynamic Damping of a Vertical Axis Wind Turbine
Ottermo, Fredric; Bernhoff, Hans
2012-01-01
The dynamics of a straight-bladed vertical axis wind turbine is investigated with respect to oscillations due to the elasticity of struts and shaft connecting to the hub. In particular, for the three-bladed turbine, a concept is proposed for dimensioning the turbine to maximize the size of the resonance free rpm range for operation. The effect of aerodynamic damping on the struts is also considered. The damping of these types of oscillations for a typical turbine is found to be good.
Aerodynamic benchmarking of the DeepWind design
DEFF Research Database (Denmark)
Bedon, Gabriele; Schmidt Paulsen, Uwe; Aagaard Madsen, Helge;
The aerodynamic benchmarking for the DeepWind rotor is conducted comparing different rotor geometries and solutions and keeping the comparison as fair as possible. The objective for the benchmarking is to find the most suitable configuration in order to maximize the power production and minimize...... the blade solicitation and the cost of energy. Different parameters are considered for the benchmarking study. The DeepWind blade is characterized by a shape similar to the Troposkien geometry but asymmetric between the top and bottom parts. The blade shape is considered as a fixed parameter...
Application of 3D printing technology in aerodynamic study
International Nuclear Information System (INIS)
3D printing, as an additive process, offers much more than traditional machining techniques in terms of achievable complexity of a model shape. That fact was a motivation to adapt discussed technology as a method for creating objects purposed for aerodynamic testing. The following paper provides an overview of various 3D printing techniques. Four models of a standard NACA0018 aerofoil were manufactured in different materials and methods: MultiJet Modelling (MJM), Selective Laser Sintering (SLS) and Fused Deposition Modeling (FDM). Various parameters of the models have been included in the analysis: surface roughness, strength, details quality, surface imperfections and irregularities as well as thermal properties.
Brodowicz, Kazimierz; Wyszynski, M L; Wyszynski
2013-01-01
Heat pumps and related technology are in widespread use in industrial processes and installations. This book presents a unified, comprehensive and systematic treatment of the design and operation of both compression and sorption heat pumps. Heat pump thermodynamics, the choice of working fluid and the characteristics of low temperature heat sources and their application to heat pumps are covered in detail.Economic aspects are discussed and the extensive use of the exergy concept in evaluating performance of heat pumps is a unique feature of the book. The thermodynamic and chemical properties o
Tuzla, K.; Russell, D. A.; Wai, J. C.
1976-01-01
Nonlifting 10% biconvex airfoils are mounted in a 30 x 40 cm Ludwieg-tube-driven transonic test-section and the flow field recorded with a holographic interferometer. Nitrogen, argon, and carbon dioxide are used as the principal test gases. Experiments are conducted with Reynolds number based on chord of (0.5-3.5) x 10 to the 6th with Mach numbers of 0.70, 0.75, and 0.80. Supporting calculations use inviscid transonic small-disturbance and full-potential computer codes coupled with simple integral boundary-layer modeling. Systematic studies show that significant gamma-effects can occur due to shock-induced separation.
Iridescent aerodynamic contrails. The Norderney case of 27 June 2008
Energy Technology Data Exchange (ETDEWEB)
Gierens, Klaus; Kaestner, Martina [Deutsches Zentrum fuer Luft- und Raumfahrt, Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere; Klatt, Dieter [Deutsches Zentrum fuer Luft- und Raumfahrt, Oldenburg (Germany). Inst. fuer Physik der Atmosphaere
2011-06-15
An iridescent aerodynamic contrail (AerC) of a 2-engine aircraft flying from Amsterdam to Copenhagen was observed and photographed at Norderney on 27 June 2008, 14:06 UTC. In order to see whether this event was caused by an unusual weather situation we investigate the meteorological situation. It turns out that the situation allows AerC to become visible because it was warm enough and sufficiently moist. The dynamical situation is studied, and it seems that the stable stratification at the flight level of 350 hPa supports the appearance of an AerC. Additionally we investigate the ambient cloudiness where interesting halo features have been displayed in cirrus clouds. We examine the special colours of the Norderney aerodynamic contrail which allows to conclude that the width of the ice crystal size distribution is the factor directly relevant for iridescence, in this case representing a mixture from different growth histories. Finally we present an argumentation that AerC can be differentiated from jet contrails as soon as they display iridescence which requires an angular distance from the sun of less than about 30 . (orig.)
Aerodynamic interaction between forewing and hindwing of a hovering dragonfly
Hu, Zheng; Deng, Xin-Yan
2014-12-01
The phase change between the forewing and hindwing is a distinct feature that sets dragonfly apart from other insects. In this paper, we investigated the aerodynamic effects of varying forewing-hindwing phase difference with a 60° inclined stroke plane during hovering flight. Force measurements on a pair of mechanical wing models showed that in-phase flight enhanced the forewing lift by 17% and the hindwing lift was reduced at most phase differences. The total lift of both wings was also reduced at most phase differences and only increased at a phase range around in-phase. The results may explain the commonly observed behavior of the dragonfly where 0° is employed in acceleration. We further investigated the wing-wing interaction mechanism using the digital particle image velocimetry (PIV) system, and found that the forewing generated a downwash flow which is responsible for the lift reduction on the hindwing. On the other hand, an upwash flow resulted from the leading edge vortex of the hindwing helps to enhance lift on the forewing. The results suggest that the dragonflies alter the phase differences to control timing of the occurrence of flow interactions to achieve certain aerodynamic effects.
Time Series Vegetation Aerodynamic Roughness Fields Estimated from MODIS Observations
Borak, Jordan S.; Jasinski, Michael F.; Crago, Richard D.
2005-01-01
Most land surface models used today require estimates of aerodynamic roughness length in order to characterize momentum transfer between the surface and atmosphere. The most common method of prescribing roughness is through the use of empirical look-up tables based solely on land cover class. Theoretical approaches that employ satellite-based estimates of canopy density present an attractive alternative to current look-up table approaches based on vegetation cover type that do not account for within-class variability and are oftentimes simplistic with respect to temporal variability. The current research applies Raupach s formulation of momentum aerodynamic roughness to MODIS data on a regional scale in order to estimate seasonally variable roughness and zero-plane displacement height fields using bulk land cover parameters estimated by [Jasinski, M.F., Borak, J., Crago, R., 2005. Bulk surface momentum parameters for satellite-derived vegetation fields. Agric. For. Meteorol. 133, 55-68]. Results indicate promising advances over look-up approaches with respect to characterization of vegetation roughness variability in land surface and atmospheric circulation models.
Design Exploration of Aerodynamic Wing Shape for RLV Flyback Booster
Chiba, Kazuhisa; Obayashi, Shigeru; Nakahashi, Kazuhiro
The wing shape of flyback booster for a Two-Stage-To-Orbit reusable launch vehicle has been optimized considering four objectives. The objectives are to minimize the shift of aerodynamic center between supersonic and transonic conditions, transonic pitching moment and transonic drag coefficient, as well as to maximize subsonic lift coefficient. The three-dimensional Reynolds-averaged Navier-Stokes computation using the modified Spalart-Allmaras one-equation model is used in aerodynamic evaluation accounting for possible flow separations. Adaptive range multi-objective genetic algorithm is used for the present study because tradeoff can be obtained using a smaller number of individuals than conventional multi-objective genetic algorithms. Consequently, four-objective optimization has produced 102 non-dominated solutions, which represent tradeoff information among four objective functions. Moreover, Self-Organizing Maps have been used to analyze the present non-dominated solutions and to visualize tradeoffs and influence of design variables to the four objectives. Self-Organizing Maps contoured by the four objective functions and design variables are found to visualize tradeoffs and effects of each design variable.
Design, aerodynamics and autonomy of the DelFly.
de Croon, G C H E; Groen, M A; De Wagter, C; Remes, B; Ruijsink, R; van Oudheusden, B W
2012-06-01
One of the major challenges in robotics is to develop a fly-like robot that can autonomously fly around in unknown environments. In this paper, we discuss the current state of the DelFly project, in which we follow a top-down approach to ever smaller and more autonomous ornithopters. The presented findings concerning the design, aerodynamics and autonomy of the DelFly illustrate some of the properties of the top-down approach, which allows the identification and resolution of issues that also play a role at smaller scales. A parametric variation of the wing stiffener layout produced a 5% more power-efficient wing. An experimental aerodynamic investigation revealed that this could be associated with an improved stiffness of the wing, while further providing evidence of the vortex development during the flap cycle. The presented experiments resulted in an improvement in the generated lift, allowing the inclusion of a yaw rate gyro, pressure sensor and microcontroller onboard the DelFly. The autonomy of the DelFly is expanded by achieving (1) an improved turning logic to obtain better vision-based obstacle avoidance performance in environments with varying texture and (2) successful onboard height control based on the pressure sensor. PMID:22617112
Control of flow separation and mixing by aerodynamic excitation
Rice, Edward J.; Abbott, John M.
1990-01-01
The recent research progress in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of fundamental nature concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research reported in this paper include influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications of this research include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made here that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.
Abatement of an aircraft exhaust plume using aerodynamic baffles.
Bennett, Michael; Christie, Simon M; Graham, Angus; Garry, Kevin P; Velikov, Stefan; Poll, D Ian; Smith, Malcolm G; Mead, M Iqbal; Popoola, Olalekan A M; Stewart, Gregor B; Jones, Roderic L
2013-03-01
The exhaust jet from a departing commercial aircraft will eventually rise buoyantly away from the ground; given the high thrust/power (i.e., momentum/buoyancy) ratio of modern aero-engines, however, this is a slow process, perhaps requiring ∼ 1 min or more. Supported by theoretical and wind tunnel modeling, we have experimented with an array of aerodynamic baffles on the surface behind a set of turbofan engines of 124 kN thrust. Lidar and point sampler measurements show that, as long as the intervention takes place within the zone where the Coanda effect holds the jet to the surface (i.e., within about 70 m in this case), then quite modest surface-mounted baffles can rapidly lift the jet away from the ground. This is of potential benefit in abating both surface concentrations and jet blast downstream. There is also some modest acoustic benefit. By distributing the aerodynamic lift and drag across an array of baffles, each need only be a fraction of the height of a single blast fence. PMID:23343109
Optimization of aerodynamic efficiency for twist morphing MAV wing
Directory of Open Access Journals (Sweden)
N.I. Ismail
2014-06-01
Full Text Available Twist morphing (TM is a practical control technique in micro air vehicle (MAV flight. However, TM wing has a lower aerodynamic efficiency (CL/CD compared to membrane and rigid wing. This is due to massive drag penalty created on TM wing, which had overwhelmed the successive increase in its lift generation. Therefore, further CL/CDmax optimization on TM wing is needed to obtain the optimal condition for the morphing wing configuration. In this paper, two-way fluid–structure interaction (FSI simulation and wind tunnel testing method are used to solve and study the basic wing aerodynamic performance over (non-optimal TM, membrane and rigid wings. Then, a multifidelity data metamodel based design optimization (MBDO process is adopted based on the Ansys-DesignXplorer frameworks. In the adaptive MBDO process, Kriging metamodel is used to construct the final multifidelity CL/CD responses by utilizing 23 multi-fidelity sample points from the FSI simulation and experimental data. The optimization results show that the optimal TM wing configuration is able to produce better CL/CDmax magnitude by at least 2% than the non-optimal TM wings. The flow structure formation reveals that low TV strength on the optimal TM wing induces low CD generation which in turn improves its overall CL/CDmax performance.
Effect of flapping trajectories on the dragonfly aerodynamics
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The effects of translational, figure-eight and double-figure-eight flapping trajectories on the dragonfly aerodynamics were numerically studied by solving the Navier-Stokes equations. There is a common characteristic regarding the lift/drag force coefficients that the downstroke flapping provides the lift forces while the upstroke flapping creates the thrust forces for different flapping trajectories. The maximum lift force coefficient exceeds five for the translational trajectory. It is greater than six for the figure-eight and double-figure-eight flapping trajectories, which is sufficiently larger than unity under the steady state flight condition. The ellipse and double-figure-eight flapping trajectories yield the decrease of the lift force, while the figure-eight flapping trajectory yields higher lift force as well as the thrust force than the translational flapping one. During the insect flight, the wing flapping status should be changed instantaneously to satisfy various requirements. Study of the flapping trajectories on the insect aerodynamics is helpful for the design of the Micro-air-vehicles (MAVs).
Aerodynamic surface stress intermittency and conditionally averaged turbulence statistics
Anderson, William; Lanigan, David
2015-11-01
Aeolian erosion is induced by aerodynamic stress imposed by atmospheric winds. Erosion models prescribe that sediment flux, Q, scales with aerodynamic stress raised to exponent, n, where n > 1 . Since stress (in fully rough, inertia-dominated flows) scales with incoming velocity squared, u2, it follows that q ~u2n (where u is some relevant component of the flow). Thus, even small (turbulent) deviations of u from its time-mean may be important for aeolian activity. This rationale is augmented given that surface layer turbulence exhibits maximum Reynolds stresses in the fluid immediately above the landscape. To illustrate the importance of stress intermittency, we have used conditional averaging predicated on stress during large-eddy simulation of atmospheric boundary layer flow over an arid, bare landscape. Conditional averaging provides an ensemble-mean visualization of flow structures responsible for erosion `events'. Preliminary evidence indicates that surface stress peaks are associated with the passage of inclined, high-momentum regions flanked by adjacent low-momentum regions. We characterize geometric attributes of such structures and explore streamwise and vertical vorticity distribution within the conditionally averaged flow field. This work was supported by the National Sci. Foundation, Phys. and Dynamic Meteorology Program (PM: Drs. N. Anderson, C. Lu, and E. Bensman) under Grant # 1500224. Computational resources were provided by the Texas Adv. Comp. Center at the Univ. of Texas.
An aerodynamic study on flexed blades for VAWT applications
Micallef, Daniel; Farrugia, Russell; Sant, Tonio; Mollicone, Pierluigi
2014-12-01
There is renewed interest in aerodynamics research of VAWT rotors. Lift type, Darrieus designs sometimes use flexed blades to have an 'egg-beater shape' with an optimum Troposkien geometry to minimize the structural stress on the blades. While straight bladed VAWTs have been investigated in depth through both measurements and numerical modelling, the aerodynamics of flexed blades has not been researched with the same level of detail. Two major effects may have a substantial impact on blade performance. First, flexing at the equator causes relatively strong trailing vorticity to be released. Secondly, the blade performance at each station along the blade is influenced by self-induced velocities due to bound vorticity. The latter is not present in a straight bladed configuration. The aim of this research is to investigate these effects in relation to an innovative 4kW wind turbine concept being developed in collaboration with industry known as a self-adjusting VAWT (or SATVAWT). The approach used in this study is based on experimental and numerical work. A lifting line free-wake vortex model was developed. Wind tunnel power and hot-wire velocity measurements were performed on a scaled down, 60cm high, three bladed model in a closed wind tunnel. Results show a substantial axial wake induction at the equator resulting in a lower power generation at this position. This induction increases with increasing degree of flexure. The self-induced velocities caused by blade bound vorticity at a particular station was found to be relatively small.
Fully integrated aerodynamic/dynamic optimization of helicopter rotor blades
Walsh, Joanne L.; Lamarsh, William J., II; Adelman, Howard M.
1992-01-01
A fully integrated aerodynamic/dynamic optimization procedure is described for helicopter rotor blades. The procedure combines performance and dynamic analyses with a general purpose optimizer. The procedure minimizes a linear combination of power required (in hover, forward flight, and maneuver) and vibratory hub shear. The design variables include pretwist, taper initiation, taper ratio, root chord, blade stiffnesses, tuning masses, and tuning mass locations. Aerodynamic constraints consist of limits on power required in hover, forward flight and maneuvers; airfoil section stall; drag divergence Mach number; minimum tip chord; and trim. Dynamic constraints are on frequencies, minimum autorotational inertia, and maximum blade weight. The procedure is demonstrated for two cases. In the first case, the objective function involves power required (in hover, forward flight and maneuver) and dynamics. The second case involves only hover power and dynamics. The designs from the integrated procedure are compared with designs from a sequential optimization approach in which the blade is first optimized for performance and then for dynamics. In both cases, the integrated approach is superior.
Some Advanced Concepts in Discrete Aerodynamic Sensitivity Analysis
Taylor, Arthur C., III; Green, Lawrence L.; Newman, Perry A.; Putko, Michele M.
2003-01-01
An efficient incremental iterative approach for differentiating advanced flow codes is successfully demonstrated on a two-dimensional inviscid model problem. The method employs the reverse-mode capability of the automatic differentiation software tool ADIFOR 3.0 and is proven to yield accurate first-order aerodynamic sensitivity derivatives. A substantial reduction in CPU time and computer memory is demonstrated in comparison with results from a straightforward, black-box reverse-mode applicaiton of ADIFOR 3.0 to the same flow code. An ADIFOR-assisted procedure for accurate second-rder aerodynamic sensitivity derivatives is successfully verified on an inviscid transonic lifting airfoil example problem. The method requires that first-order derivatives are calculated first using both the forward (direct) and reverse (adjoinct) procedures; then, a very efficient noniterative calculation of all second-order derivatives can be accomplished. Accurate second derivatives (i.e., the complete Hesian matrices) of lift, wave drag, and pitching-moment coefficients are calculated with respect to geometric shape, angle of attack, and freestream Mach number.
Exploring Discretization Error in Simulation-Based Aerodynamic Databases
Aftosmis, Michael J.; Nemec, Marian
2010-01-01
This work examines the level of discretization error in simulation-based aerodynamic databases and introduces strategies for error control. Simulations are performed using a parallel, multi-level Euler solver on embedded-boundary Cartesian meshes. Discretization errors in user-selected outputs are estimated using the method of adjoint-weighted residuals and we use adaptive mesh refinement to reduce these errors to specified tolerances. Using this framework, we examine the behavior of discretization error throughout a token database computed for a NACA 0012 airfoil consisting of 120 cases. We compare the cost and accuracy of two approaches for aerodynamic database generation. In the first approach, mesh adaptation is used to compute all cases in the database to a prescribed level of accuracy. The second approach conducts all simulations using the same computational mesh without adaptation. We quantitatively assess the error landscape and computational costs in both databases. This investigation highlights sensitivities of the database under a variety of conditions. The presence of transonic shocks or the stiffness in the governing equations near the incompressible limit are shown to dramatically increase discretization error requiring additional mesh resolution to control. Results show that such pathologies lead to error levels that vary by over factor of 40 when using a fixed mesh throughout the database. Alternatively, controlling this sensitivity through mesh adaptation leads to mesh sizes which span two orders of magnitude. We propose strategies to minimize simulation cost in sensitive regions and discuss the role of error-estimation in database quality.
Design, aerodynamics and autonomy of the DelFly
International Nuclear Information System (INIS)
One of the major challenges in robotics is to develop a fly-like robot that can autonomously fly around in unknown environments. In this paper, we discuss the current state of the DelFly project, in which we follow a top-down approach to ever smaller and more autonomous ornithopters. The presented findings concerning the design, aerodynamics and autonomy of the DelFly illustrate some of the properties of the top-down approach, which allows the identification and resolution of issues that also play a role at smaller scales. A parametric variation of the wing stiffener layout produced a 5% more power-efficient wing. An experimental aerodynamic investigation revealed that this could be associated with an improved stiffness of the wing, while further providing evidence of the vortex development during the flap cycle. The presented experiments resulted in an improvement in the generated lift, allowing the inclusion of a yaw rate gyro, pressure sensor and microcontroller onboard the DelFly. The autonomy of the DelFly is expanded by achieving (1) an improved turning logic to obtain better vision-based obstacle avoidance performance in environments with varying texture and (2) successful onboard height control based on the pressure sensor.
An unsteady aerodynamic formulation for efficient rotor tonal noise prediction
Gennaretti, M.; Testa, C.; Bernardini, G.
2013-12-01
An aerodynamic/aeroacoustic solution methodology for predction of tonal noise emitted by helicopter rotors and propellers is presented. It is particularly suited for configurations dominated by localized, high-frequency inflow velocity fields as those generated by blade-vortex interactions. The unsteady pressure distributions are determined by the sectional, frequency-domain Küssner-Schwarz formulation, with downwash including the wake inflow velocity predicted by a three-dimensional, unsteady, panel-method formulation suited for the analysis of rotors operating in complex aerodynamic environments. The radiated noise is predicted through solution of the Ffowcs Williams-Hawkings equation. The proposed approach yields a computationally efficient solution procedure that may be particularly useful in preliminary design/multidisciplinary optimization applications. It is validated through comparisons with solutions that apply the airloads directly evaluated by the time-marching, panel-method formulation. The results are provided in terms of blade loads, noise signatures and sound pressure level contours. An estimation of the computational efficiency of the proposed solution process is also presented.
Advanced Aerodynamic Technologies for Future Green Regional Aircraft
Directory of Open Access Journals (Sweden)
Catalin NAE
2014-04-01
Full Text Available Future Green Regional Aircraft (GRA will operate over airports located in the neighborhood of densely populated areas, with high frequency of takeoff/ landing events and, hence, strongly contribute to community noise and gaseous emissions. These issues currently limit further growth of traffic operated by regional airliners which, in the next future, will have to face even more stringent environmental normative worldwide and therefore re-designed to incorporate advanced active aerodynamic technologies. The new concept behind GRA is based on several mainstream technologies: airframe low-noise (LN, aerodynamic load control (LC and load alleviation (LA. These technologies integrate relevant concepts for hybrid and natural laminar flow (HLC/NLF wing, active control of wing movables and aeroelastic tailoring for LC/LA functions, passive means (micro-riblets for turbulent flow drag reduction, innovative gapless architectures (droop nose, morphing flap beside conventional high-lift devices (HLDs, active flow control through synthetic jets, low-noise solutions applied to HLDs (liners, fences, and to fuselage-mounted main and nose landing gears (bay/doors acoustic treatments, fairings, wheels hub cap. The paper deals with the technological readiness level (TRL assessment of the most promising technologies and overall integration in the new generation of GRA, as a highly optimized configuration able to meet requirements for FlighPath 2050.
Design, aerodynamics and autonomy of the DelFly.
de Croon, G C H E; Groen, M A; De Wagter, C; Remes, B; Ruijsink, R; van Oudheusden, B W
2012-06-01
One of the major challenges in robotics is to develop a fly-like robot that can autonomously fly around in unknown environments. In this paper, we discuss the current state of the DelFly project, in which we follow a top-down approach to ever smaller and more autonomous ornithopters. The presented findings concerning the design, aerodynamics and autonomy of the DelFly illustrate some of the properties of the top-down approach, which allows the identification and resolution of issues that also play a role at smaller scales. A parametric variation of the wing stiffener layout produced a 5% more power-efficient wing. An experimental aerodynamic investigation revealed that this could be associated with an improved stiffness of the wing, while further providing evidence of the vortex development during the flap cycle. The presented experiments resulted in an improvement in the generated lift, allowing the inclusion of a yaw rate gyro, pressure sensor and microcontroller onboard the DelFly. The autonomy of the DelFly is expanded by achieving (1) an improved turning logic to obtain better vision-based obstacle avoidance performance in environments with varying texture and (2) successful onboard height control based on the pressure sensor.
Directory of Open Access Journals (Sweden)
S. L. Rovin
2011-01-01
Full Text Available Heat recovery is an effective method of shortening specific energy consumption. new constructions of recuperators for heating and cupola furnaces have been designed and successfully introduced. two-stage recuperator with computer control providing blast heating up to 600 °C and reducing fuel consumption by 30% is of special interest.
The interference aerodynamics caused by the wing elasticity during store separation
Lei, Yang; Zheng-yin, Ye
2016-04-01
Air-launch-to-orbit is the technology that has stores carried aloft and launched the store from the plane to the orbit. The separation between the aircraft and store is one of the most important and difficult phases in air-launch-to-orbit technology. There exists strong aerodynamic interference between the aircraft and the store in store separation. When the aspect ratio of the aircraft is large, the elastic deformations of the wing must be considered. The main purpose of this article is to study the influence of the interference aerodynamics caused by the elastic deformations of the wing to the unsteady aerodynamics of the store. By solving the coupled functions of unsteady Navier-Stokes equations, six degrees of freedom dynamic equations and structural dynamic equations simultaneously, the store separation with the elastic deformation of the aircraft considered is simulated numerically. And the interactive aerodynamic forces are analyzed. The study shows that the interference aerodynamics is obvious at earlier time during the separation, and the dominant frequency of the elastic wing determines the aerodynamic forces frequencies of the store. Because of the effect of the interference aerodynamics, the roll angle response and pitch angle response increase. When the store is mounted under the wingtip, the additional aerodynamics caused by the wingtip vortex is obvious, which accelerate the divergence of the lateral force and the lateral-directional attitude angle of the store. This study supports some beneficial conclusions to the engineering application of the air-launch-to-orbit.
Aerodynamic design of a free power turbine for a 75 KW gas turbine automotive engine
Kofskey, M. G.; Katsanis, T.; Schumann, L. F.
1975-01-01
A single stage axial-flow turbine having a tip diameter of 15.41 centimeters was designed. The design specifications are given and the aerodynamic design procedure is described. The design includes the transition duct and the turbine exit diffuser. The aerodynamic information includes typical results of a parametric study, velocity diagrams, blade surface and wall velocities, and blade profile and wall coordinates.
AERODYNAMIC IMPROVEMENT OF KhADI 33 RACING CAR RADIATOR COMPARTMENT
Directory of Open Access Journals (Sweden)
A. Avershyn
2011-01-01
Full Text Available Aerodynamic characteristics of radiator compartment of KhADI 33 racing car on the basis of the decision of the interfaced problem of internal and external aerodynamics are numerically investigated. The rational variant of radiator compartment which is characterized by high throughput and low level of non-uniformity of speed field at the input is offered.
A Synthesis of Hybrid RANS/LES CFD Results for F-16XL Aircraft Aerodynamics
Luckring, James M.; Park, Michael A.; Hitzel, Stephan M.; Jirasek, Adam; Lofthouse, Andrew J.; Morton, Scott A.; McDaniel, David R.; Rizzi, Arthur M.
2015-01-01
A synthesis is presented of recent numerical predictions for the F-16XL aircraft flow fields and aerodynamics. The computational results were all performed with hybrid RANS/LES formulations, with an emphasis on unsteady flows and subsequent aerodynamics, and results from five computational methods are included. The work was focused on one particular low-speed, high angle-of-attack flight test condition, and comparisons against flight-test data are included. This work represents the third coordinated effort using the F-16XL aircraft, and a unique flight-test data set, to advance our knowledge of slender airframe aerodynamics as well as our capability for predicting these aerodynamics with advanced CFD formulations. The prior efforts were identified as Cranked Arrow Wing Aerodynamics Project International, with the acronyms CAWAPI and CAWAPI-2. All information in this paper is in the public domain.
Quasi steady-state aerodynamic model development for race vehicle simulations
Mohrfeld-Halterman, J. A.; Uddin, M.
2016-01-01
Presented in this paper is a procedure to develop a high fidelity quasi steady-state aerodynamic model for use in race car vehicle dynamic simulations. Developed to fit quasi steady-state wind tunnel data, the aerodynamic model is regressed against three independent variables: front ground clearance, rear ride height, and yaw angle. An initial dual range model is presented and then further refined to reduce the model complexity while maintaining a high level of predictive accuracy. The model complexity reduction decreases the required amount of wind tunnel data thereby reducing wind tunnel testing time and cost. The quasi steady-state aerodynamic model for the pitch moment degree of freedom is systematically developed in this paper. This same procedure can be extended to the other five aerodynamic degrees of freedom to develop a complete six degree of freedom quasi steady-state aerodynamic model for any vehicle.
Numerical quantification of aerodynamic damping on pitching of vehicle-inspired bluff body
Cheng, S. Y.; Tsubokura, M.; Nakashima, T.; Okada, Y.; Nouzawa, T.
2012-04-01
The influence of transient flows on vehicle stability was investigated by large eddy simulation. To consider the dynamic response of a vehicle to real-life transient aerodynamics, a dimensionless parameter that quantifies the amount of aerodynamic damping for vehicle subjects to pitching oscillation is proposed. Two vehicle models with different stability characteristics were created to verify the parameter. For idealized notchback models, underbody has the highest contribution to the total aerodynamic damping, which was up to 69%. However, the difference between the aerodynamic damping of models with distinct A- and C-pillar configurations mainly depends on the trunk-deck contribution. Comparison between dynamically obtained phase-averaged pitching moment with quasi-steady values shows totally different aerodynamic behaviors.
The influence of aerodynamic coefficients on the elements of classic projectile paths
Directory of Open Access Journals (Sweden)
Damir D. Jerković
2011-04-01
Full Text Available The article deals with the results of the research on the influence of aerodynamic coefficient values on the trajectory elements and the stability parameters of classic axisymmetric projectiles. It presents the characteristic functions of aerodynamic coefficients with regard to aerodynamic parameters and the projectile body shape. The trajectory elements of the model of classic axisymmetric projectiles and the analyses of their changes were presented with respect to the aerodynamic coefficient values. Introduction Classic axisymmetric projectiles fly through atmosphere using muzzle velocity as initial energy resource, so the aerodynamic force and moment have the most significant influence on the motion of projectiles. The aerodynamic force and moment components represented as aerodynamic coefficients depend on motion velocity i. e. flow velocity, the flow features produced by projectile shape and position in the flow, and angular velocity (rate of the body. The functional dependence of aerodynamic coefficients on certain influential parameters, such as angle of attack and angular velocity components is expressed by the derivative of aerodynamic coefficients. The determination of aerodynamic coefficients and derivatives enables complete definition of the aerodynamic force and moment acting on the classic projectile. The projectile motion problem is considered in relation to defining the projectile stability parameters and the conditions under which the stability occurs. The comparative analyses of aerodynamic coefficient values obtained by numerical methods, semi empirical calculations and experimental research give preliminary evaluation of the quality of the determined values. The flight simulation of the motion of a classic axisymetric projectile, which has the shape defined by the aerodynamic coefficient values, enables the comparative analyses of the trajectory elements and stability characteristics. The model of the classic projectile
Performance of streamlined bridge decks in relation to the aerodynamics of a flat plate
DEFF Research Database (Denmark)
Larose, Guy; Livesey, Flora M.
1997-01-01
The aerodynamics of three modern bridge decks are compared to the aerodynamics of a 16:1 flat plate. The comparisons are made on the basis of the analytical evaluation of the performance of each cross-section to the buffeting action of the wind. In general, the closed-box girders studied in this ......The aerodynamics of three modern bridge decks are compared to the aerodynamics of a 16:1 flat plate. The comparisons are made on the basis of the analytical evaluation of the performance of each cross-section to the buffeting action of the wind. In general, the closed-box girders studied...... in this paper showed buffeting responses similar to a flat plate with the exception of the multi-box girder which performed much better aerodynamically....
Aerodynamic Optimization of an Over-the-Wing-Nacelle-Mount Configuration
Directory of Open Access Journals (Sweden)
Daisuke Sasaki
2011-01-01
Full Text Available An over-the-wing-nacelle-mount airplane configuration is known to prevent the noise propagation from jet engines toward ground. However, the configuration is assumed to have low aerodynamic efficiency due to the aerodynamic interference effect between a wing and a nacelle. In this paper, aerodynamic design optimization is conducted to improve aerodynamic efficiency to be equivalent to conventional under-the-wing-nacelle-mount configuration. The nacelle and wing geometry are modified to achieve high lift-to-drag ratio, and the optimal geometry is compared with a conventional configuration. Pylon shape is also modified to reduce aerodynamic interference effect. The final wing-fuselage-nacelle model is compared with the DLR F6 model to discuss the potential of Over-the-Wing-Nacelle-Mount geometry for an environmental-friendly future aircraft.
Directory of Open Access Journals (Sweden)
Grković Vojin R.
2013-01-01
Full Text Available The paper presents the mathematical model and the procedure for calculation of the resultant force acting on the air cooled gas turbine blade(s based on the aerodynamic theory and computation of the circulation around the blade profile. In the conducted analysis was examined the influence of the cooling air mass flow expressed through the cooling air flow parameter λc, as well as, the values of the inlet and outlet angles β1 and β2, on the magnitude of the tangential and axial forces. The procedure and analysis were exemplified by the calculation of the tangential and axial forces magnitudes. [Projekat Ministarstva nauke Republike Srbije: Development and building the demonstrative facility for combined heat and power with gasification
Energy Technology Data Exchange (ETDEWEB)
Craig, L.B.; Farma, A.J.
1987-01-06
This invention concerns a heat exchanger as used in a space heater, of the type in which hot exhaust gases transfer heat to water or the like flowing through a helical heat exchange coil. A significant improvement to the efficiency of the heat exchange occurring between the air and water is achieved by using a conduit for the water having external helical fluting such that the hot gases circulate along two paths, rather than only one. A preferred embodiment of such a heat exchanger includes a porous combustion element for producing radiant heat from a combustible gas, surrounded by a helical coil for effectively transferring the heat in the exhaust gas, flowing radially from the combustion element, to the water flowing through the coil. 4 figs.
Modlin, James Michael
An investigation was conducted to study the feasibility of cooling hypersonic vehicle leading edge structures exposed to severe aerodynamic surface heat fluxes using a combination of liquid metal heat pipes and surface mass transfer cooling techniques. A generalized, transient, finite difference based hypersonic leading edge cooling model was developed that incorporated these effects and was demonstrated on an assumed aerospace plane-type wing leading edge section and a SCRAMJET engine inlet leading edge section. The hypersonic leading edge cooling model was developed using an existing, experimentally verified heat pipe model. Two applications of the hypersonic leading edge cooling model were examined. An assumed aerospace plane-type wing leading edge section exposed to a severe laminar, hypersonic aerodynamic surface heat flux was studied. A second application of the hypersonic leading edge cooling model was conducted on an assumed one-quarter inch nose diameter SCRAMJET engine inlet leading edge section exposed to both a transient laminar, hypersonic aerodynamic surface heat flux and a type 4 shock interference surface heat flux. The investigation led to the conclusion that cooling leading edge structures exposed to severe hypersonic flight environments using a combination of liquid metal heat pipe, surface transpiration, and film cooling methods appeared feasible.
Investigation of Aerodynamic Interference of Double Deck Bridges
Energy Technology Data Exchange (ETDEWEB)
Sitek, M. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division. Transportation Research and Analysis Computing Center (TRACC); Bojanowski, C. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division. Transportation Research and Analysis Computing Center (TRACC); Lottes, S. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Energy Systems Division. Transportation Research and Analysis Computing Center (TRACC)
2016-05-01
Construction of a twin bridge can be a cost effective and minimally disruptive way to increase capacity when an existing bridge is not near the end of its service life. With ever growing vehicular traffic, when demand approaches the capacity of many existing roads and bridges. Remodeling a structure with an insufficient number of lanes can be a good solution in case of smaller and less busy bridges. Closing down or reducing traffic on crossings of greater importance for the construction period, however, can result in major delays and revenue loss for commerce and transportation as well as increasing the traffic load on alternate route bridges. Multiple-deck bridges may be the answer to this issue. A parallel deck can be built next to the existing one, without reducing the flow. Additionally, a new bridge can be designed as a twin or multi-deck structure. Several such structures have been built throughout the United States, among them: - The New NY Bridge Project - the Tappan Zee Hudson River Crossing, - SR-182 Columbia River Bridge, - The Thaddeus Kosciusko Bridge (I-87), - The Allegheny River Bridge, Pennsylvania, which carries I76, - Fred Hartman Bridge, TX, see Figure 1.2. With a growing number of double deck bridges, additional, more detailed, studies on the interaction of such bridge pairs in windy conditions appears appropriate. Aerodynamic interference effects should be examined to assure the aerodynamic stability of both bridges. There are many studies on aerodynamic response of single deck bridges, but the literature on double-deck structures is not extensive. The experimental results from wind tunnels are still limited in number, as a parametric study is required, they can be very time consuming. Literature review shows that some investigation of the effects of gap-width and angle of wind incidence has been done. Most of the CFD computational studies that have been done were limited to 2D simulations. Therefore, it is desirable to investigate twin decks
Weber, J. K. R.; Tamalonis, A.; Benmore, C. J.; Alderman, O. L. G.; Sendelbach, S.; Hebden, A.; Williamson, M. A.
2016-07-01
An aerodynamic levitator with carbon dioxide laser beam heating was integrated with a hermetically sealed controlled atmosphere chamber and sample handling mechanism. The system enabled containment of radioactive samples and control of the process atmosphere chemistry. The chamber was typically operated at a pressure of approximately 0.9 bars to ensure containment of the materials being processed. Samples 2.5-3 mm in diameter were levitated in flowing gas to achieve containerless conditions. Levitated samples were heated to temperatures of up to 3500 °C with a partially focused carbon dioxide laser beam. Sample temperature was measured using an optical pyrometer. The sample environment was integrated with a high energy (100 keV) x-ray synchrotron beamline to enable in situ structure measurements to be made on levitated samples as they were heated, melted, and supercooled. The system was controlled from outside the x-ray beamline hutch by using a LabVIEW program. Measurements have been made on hot solid and molten uranium dioxide and binary uranium dioxide-zirconium dioxide compositions.
Lin, Qiao; Jiang, Fukang; Wang, Xuan-Qi; Xu, Yong; Han, Zhigang; Tai, Yu-Chong; Lew, James; Ho, Chih-Ming
2004-12-01
MEMS thermal shear-stress sensors exploit heat-transfer effects to measure the shear stress exerted by an air flow on its solid boundary, and have promising applications in aerodynamic control. Classical theory for conventional, macroscale thermal shear-stress sensors states that the rate of heat removed by the flow from the sensor is proportional to the 1/3-power of the shear stress. However, we have observed that this theory is inconsistent with experimental data from MEMS sensors. This paper seeks to develop an understanding of MEMS thermal shear-stress sensors through a study including both experimental and theoretical investigations. We first obtain experimental data that confirm the inadequacy of the classical theory by wind-tunnel testing of prototype MEMS shear-stress sensors with different dimensions and materials. A theoretical analysis is performed to identify that this inadequacy is due to the lack of a thin thermal boundary layer in the fluid flow at the sensor surface, and then a two-dimensional MEMS shear-stress sensor theory is presented. This theory incorporates important heat-transfer effects that are ignored by the classical theory, and consistently explains the experimental data obtained from prototype MEMS sensors. Moreover, the prototype MEMS sensors are studied with three-dimensional simulations, yielding results that quantitatively agree with experimental data. This work demonstrates that classical assumptions made for conventional thermal devices should be carefully examined for miniature MEMS devices.
Weber, J K R; Tamalonis, A; Benmore, C J; Alderman, O L G; Sendelbach, S; Hebden, A; Williamson, M A
2016-07-01
An aerodynamic levitator with carbon dioxide laser beam heating was integrated with a hermetically sealed controlled atmosphere chamber and sample handling mechanism. The system enabled containment of radioactive samples and control of the process atmosphere chemistry. The chamber was typically operated at a pressure of approximately 0.9 bars to ensure containment of the materials being processed. Samples 2.5-3 mm in diameter were levitated in flowing gas to achieve containerless conditions. Levitated samples were heated to temperatures of up to 3500 °C with a partially focused carbon dioxide laser beam. Sample temperature was measured using an optical pyrometer. The sample environment was integrated with a high energy (100 keV) x-ray synchrotron beamline to enable in situ structure measurements to be made on levitated samples as they were heated, melted, and supercooled. The system was controlled from outside the x-ray beamline hutch by using a LabVIEW program. Measurements have been made on hot solid and molten uranium dioxide and binary uranium dioxide-zirconium dioxide compositions. PMID:27475566
Wake-Induced Aerodynamics on a Trailing Aircraft
Mendenhall, Michael R.; Lesieutre, Daniel J.; Kelly, Michael J.
2016-01-01
NASA conducted flight tests to measure the exhaust products from alternative fuels using a DC-8 transport aircraft and a Falcon business jet. An independent analysis of the maximum vortex-induced loads on the Falcon in the DC-8 wake was conducted for pre-flight safety analysis and to define safe trail distances for the flight tests. Static and dynamic vortex-induced aerodynamic loads on the Falcon were predicted at a matrix of locations aft of the DC-8 under flight-test conditions, and the maximum loads were compared with design limit loads to assess aircraft safety. Trajectory simulations for the Falcon during close encounters with the DC-8 wake were made to study the vortex-induced loads during traverses of the DC-8 primary trailing vortex. A parametric study of flight traverses through the trailing vortex was conducted to assess Falcon flight behavior and motion characteristics.
SOFIA Closed- and Open-Door Aerodynamic Analyses
Cumming, Stephen; Frederick, Mike; Smith, Mark
2012-01-01
Work to evaluate the aerodynamic characteristics and the cavity acoustic environment of the SOFIA (Stratospheric Observatory for Infrared Astronomy) airplane has been completed. The airplane has been evaluated in its closed-door configuration, as well as several open-door configurations. Work performed included: acoustic analysis tool development, cavity acoustic evaluation, stability and control parameter estimation, air data calibration, and external flow evaluation. Qualitative airflow data were obtained during the closed- and open-door flights using tufts on the aft portion of the fuselage. Video was taken from a chase plane. This video was analyzed for various flight conditions, and general flow descriptions of the aft fuselage of the 747SP were developed for the different closed and open door configurations.
A Computational Model for Rotor-Fuselage Interactional Aerodynamics
Boyd, D. Douglas, Jr.; Barnwell, Richard W.; Gorton, Susan Althoff
2000-01-01
A novel unsteady rotor-fuselage interactional aerodynamics model has been developed. This model loosely couples a Generalized Dynamic Wake Theory (GDWT) to a thin-layer Navier-Stokes solution procedure. This coupling is achieved using an unsteady pressure jump boundary condition in the Navier-Stokes model. The new unsteady pressure jump boundary condition models each rotor blade as a moving pressure jump which travels around the rotor azimuth and is applied between two adjacent planes in a cylindrical, non-rotating grid. Comparisons are made between measured and predicted time-averaged and time-accurate rotor inflow ratios. Additional comparisons are made between measured and predicted unsteady surface pressures on the top centerline and sides of the fuselage.
Aerodynamics of thrust vectoring by Navier-Stokes solutions
Tseng, Jing-Biau; Lan, C. Edward
1991-01-01
Induced aerodynamics from thrust vectoring are investigated by a computational fluid dynamic method. A thin-layer Reynolds-averaged Navier-Stokes code with multiblock capability is used. Jet properties are specified on the nozzle exit plane to simulate the jet momentum. Results for a rectangular jet in a cross flow are compared with data to verify the code. Further verification of the calculation is made by comparing the numerical results with transonic data for a wing-body combination. Additional calculations were performed to elucidate the following thrust vectoring effects: the thrust vectoring effect on shock and expansion waves, induced effects on nearby surfaces, and the thrust vectoring effect on the leading edge vortex.
Sparse polynomial surrogates for aerodynamic computations with random inputs
Savin, Eric; Peter, Jacques
2015-01-01
This paper deals with some of the methodologies used to construct polynomial surrogate models based on generalized polynomial chaos (gPC) expansions for applications to uncertainty quantification (UQ) in aerodynamic computations. A core ingredient in gPC expansions is the choice of a dedicated sampling strategy, so as to define the most significant scenarios to be considered for the construction of such metamodels. A desirable feature of the proposed rules shall be their ability to handle several random inputs simultaneously. Methods to identify the relative "importance" of those variables or uncertain data shall be ideally considered as well. The present work is more particularly dedicated to the development of sampling strategies based on sparsity principles. Sparse multi-dimensional cubature rules based on general one-dimensional Gauss-Jacobi-type quadratures are first addressed. These sets are non nested, but they are well adapted to the probability density functions with compact support for the random in...
Scientific visualization in computational aerodynamics at NASA Ames Research Center
Bancroft, Gordon V.; Plessel, Todd; Merritt, Fergus; Walatka, Pamela P.; Watson, Val
1989-01-01
The visualization methods used in computational fluid dynamics research at the NASA-Ames Numerical Aerodynamic Simulation facility are examined, including postprocessing, tracking, and steering methods. The visualization requirements of the facility's three-dimensional graphical workstation are outlined and the types hardware and software used to meet these requirements are discussed. The main features of the facility's current and next-generation workstations are listed. Emphasis is given to postprocessing techniques, such as dynamic interactive viewing on the workstation and recording and playback on videodisk, tape, and 16-mm film. Postprocessing software packages are described, including a three-dimensional plotter, a surface modeler, a graphical animation system, a flow analysis software toolkit, and a real-time interactive particle-tracer.
Estimation of unsteady aerodynamic forces using pointwise velocity data
Gómez, F; Blackburn, H M
2016-01-01
A novel method to estimate unsteady aerodynamic force coefficients from pointwise velocity measurements is presented. The methodology is based on a resolvent-based reduced-order model which requires the mean flow to obtain physical flow structures and pointwise measurement to calibrate their amplitudes. A computationally-affordable time-stepping methodology to obtain resolvent modes in non-trivial flow domains is introduced and compared to previous existing matrix-free and matrix-forming strategies. The technique is applied to the unsteady flow around an inclined square cylinder at low Reynolds number. The potential of the methodology is demonstrated through good agreement between the fluctuating pressure distribution on the cylinder and the temporal evolution of the unsteady lift and drag coefficients predicted by the model and those computed by direct numerical simulation.
Aerodynamic pitching damping of vehicle-inspired bluff bodies
Tsubokura, Makoto; Cheng, Seeyuan; Nakashima, Takuji; Nouzawa, Takahide; Okada, Yoshihiro
2010-11-01
Aerodynamic damping mechanism of road vehicles subjected to pitching oscillation was investigated by using large-eddy simulation technique. The study was based on two kinds of simplified vehicle models, which represent real sedan-type vehicles with different pitching stability in the on-road test. The simplified vehicle modes were developed so as to reproduce the characteristic flow structures above the trunk deck of the real vehicles measured in a wind-tunnel at the static case without oscillation. The forced sinusoidal pitching oscillation was imposed on the models and their pitching damping factors were evaluated through the phase-averaged pitching moment. Then flow structures in the wake of the models were extracted and its contribution to the damping mechanism was discussed. It was found that slight difference of the front and rear pillars' shape drastically affects the flow structures in the wake of the models, which enhance or restrain the vehicles' pitching instability.
The Aerodynamics of Deforming Wings at Low Reynolds Number
Medina, Albert
Flapping flight has gained much attention in the past decade driven by the desire to understand capabilities observed in nature and the desire to develop agile small-scale aerial vehicles. Advancing our current understanding of unsteady aerodynamics is an essential component in the development of micro-air vehicles (MAV) intended to utilize flight mechanics akin to insect flight. Thus the efforts undertaken that of bio-mimicry. The complexities of insect wing motion are dissected and simplified to more tractable problems to elucidate the fundamentals of unsteady aerodynamics in biologically inspired kinematics. The MAV's fruition would satisfy long established needs in both the military and civilian sectors. Although recent studies have provided great insight into the lift generating mechanisms of flapping wings the deflection response of such wings remains poorly understood. This dissertation numerically and experimentally investigates the aerodynamic performance of passively and actively deflected wings in hover and rotary kinematics. Flexibility is distilled to discrete lines of flexion which acknowledging major flexion lines in insect wings to be the primary avenue for deformation. Of primary concern is the development of the leading-edge vortex (LEV), a high circulation region of low pressure above the wing to which much of the wing's lift generation is attributed. Two-dimensional simulations of wings with chord-wise flexibility in a freestream reveal a lift generating mechanism unavailable to rigid wings with origins in vortical symmetry breaking. The inclusion of flexibility in translating wings accelerated from rest revealed the formation time of the initial LEV was very weakly dependent on the flexible stiffness of the wing, maintaining a universal time scale of four to five chords of travel before shedding. The frequency of oscillatory shedding of the leading and trailing-edge vortices that develops after the initial vortex shedding was shown to be
Small, high pressure ratio compressor: Aerodynamic and mechanical design
Bryce, C. A.; Erwin, J. R.; Perrone, G. L.; Nelson, E. L.; Tu, R. K.; Bosco, A.
1973-01-01
The Small, High-Pressure-Ratio Compressor Program was directed toward the analysis, design, and fabrication of a centrifugal compressor providing a 6:1 pressure ratio and an airflow rate of 2.0 pounds per second. The program consists of preliminary design, detailed areodynamic design, mechanical design, and mechanical acceptance tests. The preliminary design evaluate radial- and backward-curved blades, tandem bladed impellers, impeller-and diffuser-passage boundary-layer control, and vane, pipe, and multiple-stage diffusers. Based on this evaluation, a configuration was selected for detailed aerodynamic and mechanical design. Mechanical acceptance test was performed to demonstrate that mechanical design objectives of the research package were met.
Application of surrogate-based global optimization to aerodynamic design
Pérez, Esther
2016-01-01
Aerodynamic design, like many other engineering applications, is increasingly relying on computational power. The growing need for multi-disciplinarity and high fidelity in design optimization for industrial applications requires a huge number of repeated simulations in order to find an optimal design candidate. The main drawback is that each simulation can be computationally expensive – this becomes an even bigger issue when used within parametric studies, automated search or optimization loops, which typically may require thousands of analysis evaluations. The core issue of a design-optimization problem is the search process involved. However, when facing complex problems, the high-dimensionality of the design space and the high-multi-modality of the target functions cannot be tackled with standard techniques. In recent years, global optimization using meta-models has been widely applied to design exploration in order to rapidly investigate the design space and find sub-optimal solutions. Indeed, surrogat...
Influence of a humidor on the aerodynamics of baseballs
Meyer, Edmund
2007-01-01
We investigate whether storing baseballs in a controlled humidity environment significantly affects their aerodynamic properties. To do this, we measure the change in diameter and mass of baseballs as a function of relative humidity (RH). We then model trajectories for pitched and batted baseballs to assess the difference between those stored at 30% RH versus 50% RH. The results show that a drier baseball may be expected to curve slightly more than a humidified one, and that the drier ball will also likely travel slightly less far when batted. We discuss consequences of these results for baseball played at Coors Field in Denver, where baseballs have been stored in a humidor at 50% RH since 2002.
Multi-objective aerodynamic shape optimization of small livestock trailers
Gilkeson, C. A.; Toropov, V. V.; Thompson, H. M.; Wilson, M. C. T.; Foxley, N. A.; Gaskell, P. H.
2013-11-01
This article presents a formal optimization study of the design of small livestock trailers, within which the majority of animals are transported to market in the UK. The benefits of employing a headboard fairing to reduce aerodynamic drag without compromising the ventilation of the animals' microclimate are investigated using a multi-stage process involving computational fluid dynamics (CFD), optimal Latin hypercube (OLH) design of experiments (DoE) and moving least squares (MLS) metamodels. Fairings are parameterized in terms of three design variables and CFD solutions are obtained at 50 permutations of design variables. Both global and local search methods are employed to locate the global minimum from metamodels of the objective functions and a Pareto front is generated. The importance of carefully selecting an objective function is demonstrated and optimal fairing designs, offering drag reductions in excess of 5% without compromising animal ventilation, are presented.
Unsteady aerodynamic models for agile flight at low Reynolds numbers
Brunton, Steven L.
This work develops low-order models for the unsteady aerodynamic forces on a wing in response to agile maneuvers at low Reynolds number. Model performance is assessed on the basis of accuracy across a range of parameters and frequencies as well as of computational efficiency and compatibility with existing control techniques and flight dynamic models. The result is a flexible modeling procedure that yields accurate, low-dimensional, state-space models. The modeling procedures are developed and tested on direct numerical simulations of a two-dimensional flat plate airfoil in motion at low Reynolds number, Re=100, and in a wind tunnel experiment at the Illinois Institute of Technology involving a NACA 0006 airfoil pitching and plunging at Reynolds number Re=65,000. In both instances, low-order models are obtained that accurately capture the unsteady aerodynamic forces at all frequencies. These cases demonstrate the utility of the modeling procedure developed in this thesis for obtaining accurate models for different geometries and Reynolds numbers. Linear reduced-order models are constructed from either the indicial response (step response) or realistic input/output maneuvers using a flexible modeling procedure. The method is based on identifying stability derivatives and modeling the remaining dynamics with the eigensystem realization algorithm. A hierarchy of models is developed, based on linearizing the flow at various operating conditions. These models are shown to be accurate and efficient for plunging, pitching about various points, and combined pitch and plunge maneuvers, at various angle of attack and Reynolds number. Models are compared against the classical unsteady aerodynamic models of Wagner and Theodorsen over a large range of Strouhal number and reduced frequency for a baseline comparison. Additionally, state-space representations are developed for Wagner's and Theodorsen's models, making them compatible with modern control-system analysis. A number of
International Symposium on Recent Advances in Aerodynamics and Acoustics
Smith, Charles
1986-01-01
The Joint Institute for Aeronautics and Acoustics at Stanford University was established in October 1973 to provide an academic environment for long-term cooperative research between Stanford and NASA Ames Research Center. Since its establishment, the Institute has conducted theoretical and experimental work in the areas of aerodynamics, acoustics, fluid mechanics, flight dynamics, guidance and control, and human factors. This research has involved Stanford faculty, research associates, graduate students, and many distinguished visitors in collaborative efforts with the research staff of NASA Ames Research Center. The occasion of the Institute's tenth anniversary was used to reflect back on where that research has brought us, and to consider where our endeavors should be directed next. Thus, an International Symposium was held to review recent advances in the fields relevant to the activities of the Institute and to discuss the areas of research to be undertaken in the future. This anniversary was also chosen...
Experimental Analysis of Aerodynamic Aspects of Sport Utility Vehicle
Directory of Open Access Journals (Sweden)
DINESH Y DHANDE
2013-07-01
Full Text Available In an era fuel efficiency has become topic of discussion not only among the scholar researchers but also common men. As rapid and continuous increase in prizes of fuels consumers are going for most fuel efficient vehicles. By aerodynamic styling of vehicle one can not only improve the fuel efficiency but also ensure better stability and good handling characteristics of vehicles at higher speed especially on highways. The paper describes assessment of drag force (Fd and drag coefficient (Cd by conventional wind tunnel method. Theexperimental calculations were performed on subsonic wind tunnel having test section of 100cm x 30cm x 30 cm. Exact replica of model of sports utility vehicle (suv on reduced scale 1:32 is used to for experimentation to calculate Fd and Cd.
A Newton-Krylov algorithm for complex aerodynamic design
Energy Technology Data Exchange (ETDEWEB)
Nemec, M.; Zingg, D.W. [Univ. of Toronto, Inst. for Aerospace Studies, Toronto, Ontario (Canada)]. E-mail: marian@oddjob.utias.utoronto.ca
2002-07-01
A Newton-Krylov algorithm for the optimization of single-and multi-element airfoil configurations is presented. The algorithm uses the preconditioned generalized minimum residual (GMRES) method for the computation of the objective function gradient via the discrete-adjoint approach. Furthermore, the GMRES method is also used for the solution of the two-dimensional Navier-Stokes equations in conjunction with an inexact-Newton strategy. Design examples include a lift-enhancement problem, where the optimal position of a flap is determined for a two-element configuration, and also a multi-point lift-constrained transonic drag minimization problem. The results indicate that the new algorithm provides an efficient and robust tool for practical aerodynamic design. (author)
Aerodynamic performance prediction of Darrieus-type wind turbines
Directory of Open Access Journals (Sweden)
Ion NILĂ
2010-06-01
Full Text Available The prediction of Darrieus wind turbine aerodynamic performances provides the necessarydesign and operational data base related to the wind potential. In this sense it provides the type ofturbine suitable to the area where it is to be installed. Two calculation methods are analyzed for arotor with straight blades. The first one is a global method that allows an assessment of the turbinenominal power by a brief calculation. This method leads to an overestimation of performances. Thesecond is the calculation method of the gust factor and momentum which deals with the pale as beingcomposed of different elements that don’t influence each other. This method, developed based on thetheory of the turbine blades, leads to values close to the statistical data obtained experimentally. Thevalues obtained by the calculation method of gust factor - momentum led to the concept of a Darrieusturbine, which will be tested for different wind values in the INCAS subsonic wind tunnel.
Team Software Development for Aerothermodynamic and Aerodynamic Analysis and Design
Alexandrov, N.; Atkins, H. L.; Bibb, K. L.; Biedron, R. T.; Carpenter, M. H.; Gnoffo, P. A.; Hammond, D. P.; Jones, W. T.; Kleb, W. L.; Lee-Rausch, E. M.
2003-01-01
A collaborative approach to software development is described. The approach employs the agile development techniques: project retrospectives, Scrum status meetings, and elements of Extreme Programming to efficiently develop a cohesive and extensible software suite. The software product under development is a fluid dynamics simulator for performing aerodynamic and aerothermodynamic analysis and design. The functionality of the software product is achieved both through the merging, with substantial rewrite, of separate legacy codes and the authorship of new routines. Examples of rapid implementation of new functionality demonstrate the benefits obtained with this agile software development process. The appendix contains a discussion of coding issues encountered while porting legacy Fortran 77 code to Fortran 95, software design principles, and a Fortran 95 coding standard.
Aerodynamic, structural, and trajectory analysis of ASTRID-1 vehicle
Energy Technology Data Exchange (ETDEWEB)
Glover, L.S.; Iwaskiw, A.P.; Oursler, M.A.; Perini, L.L.; Schaefer, E.D.
1994-02-10
The Johns Hopkins University/Applied Physics Laboratory, JHU/API, in support of Lawrence Livermore National Laboratory, LLNL, is conducting aerodynamic, trajectory, and structural analysis of the Advanced Single Stage Technology Rapid Insertion Demonstration (ASTRID) vehicle, being launched out of Vandenberg Air Force Base (VAFB) in February 1994. The launch is designated ASTRID-1 and is the first in a series of three that will be launched out of VAFB. Launch dates for the next two flights have not been identified, but they are scheduled for the 1994-1995 time frame. The primary goal of the ASTRID-1 flight is to test the LLNL light weight thrust on demand bi-propellant pumped divert propulsion system. The system is employed as the main thrusters for the ASTRID-1 vehicle and uses hydrazine as the mono-propellant. The major conclusions are: (1) The vehicle is very stable throughout flight (stability margin = 17 to 24 inches); (2) The aerodynamic frequency and the roll rate are such that pitch-roll interactions will be small; (3) The high stability margin combined with the high launcher elevation angle makes the vehicle flight path highly sensitive to perturbations during the initial phase of flight, i.e., during the first second of flight after leaving the rail; (4) The major impact dispersions for the test flight are due to winds. The wind impact dispersions are 90% dictated by the low altitude, 0 to 1000 ft., wind conditions; and (5) In order to minimize wind dispersions, head wind conditions are favored for the launch as November VAFB mean tail winds result in land impacts. The ballistic wind methodology can be employed to assess the impact points of winds at the launch site.
Aerodynamic effects of trees on pollutant concentration in street canyons.
Buccolieri, Riccardo; Gromke, Christof; Di Sabatino, Silvana; Ruck, Bodo
2009-09-15
This paper deals with aerodynamic effects of avenue-like tree planting on flow and traffic-originated pollutant dispersion in urban street canyons by means of wind tunnel experiments and numerical simulations. Several parameters affecting pedestrian level concentration are investigated, namely plant morphology, positioning and arrangement. We extend our previous work in this novel aspect of research to new configurations which comprise tree planting of different crown porosity and stand density, planted in two rows within a canyon of street width to building height ratio W/H=2 with perpendicular approaching wind. Sulfur hexafluoride was used as tracer gas to model the traffic emissions. Complementary to wind tunnel experiments, 3D numerical simulations were performed with the Computational Fluid Dynamics (CFD) code FLUENT using a Reynolds Stress turbulence closure for flow and the advection-diffusion method for concentration calculations. In the presence of trees, both measurements and simulations showed considerable larger pollutant concentrations near the leeward wall and slightly lower concentrations near the windward wall in comparison with the tree-less case. Tree stand density and crown porosity were found to be of minor importance in affecting pollutant concentration. On the other hand, the analysis indicated that W/H is a more crucial parameter. The larger the value of W/H the smaller is the effect of trees on pedestrian level concentration regardless of tree morphology and arrangement. A preliminary analysis of approaching flow velocities showed that at low wind speed the effect of trees on concentrations is worst than at higher speed. The investigations carried out in this work allowed us to set up an appropriate CFD modelling methodology for the study of the aerodynamic effects of tree planting in street canyons. The results obtained can be used by city planners for the design of tree planting in the urban environment with regard to air quality issues
The influence of flight style on the aerodynamic properties of avian wings as fixed lifting surfaces
Dimitriadis, Grigorios; Nudds, Robert L.
2016-01-01
The diversity of wing morphologies in birds reflects their variety of flight styles and the associated aerodynamic and inertial requirements. Although the aerodynamics underlying wing morphology can be informed by aeronautical research, important differences exist between planes and birds. In particular, birds operate at lower, transitional Reynolds numbers than do most aircraft. To date, few quantitative studies have investigated the aerodynamic performance of avian wings as fixed lifting surfaces and none have focused upon the differences between wings from different flight style groups. Dried wings from 10 bird species representing three distinct flight style groups were mounted on a force/torque sensor within a wind tunnel in order to test the hypothesis that wing morphologies associated with different flight styles exhibit different aerodynamic properties. Morphological differences manifested primarily as differences in drag rather than lift. Maximum lift coefficients did not differ between groups, whereas minimum drag coefficients were lowest in undulating flyers (Corvids). The lift to drag ratios were lower than in conventional aerofoils and data from free-flying soaring species; particularly in high frequency, flapping flyers (Anseriformes), which do not rely heavily on glide performance. The results illustrate important aerodynamic differences between the wings of different flight style groups that cannot be explained solely by simple wing-shape measures. Taken at face value, the results also suggest that wing-shape is linked principally to changes in aerodynamic drag, but, of course, it is aerodynamics during flapping and not gliding that is likely to be the primary driver.
Transonic unsteady aerodynamics in the vicinity of shock-buffet instability
Iovnovich, M.; Raveh, D. E.
2012-02-01
A study of transonic unsteady aerodynamic responses in the vicinity of shock-buffet is presented. Navier-Stokes simulations of a NACA 0012 airfoil with a fitted 20% trailing edge flap are performed to compute the aerodynamic responses to prescribed pitch and flap motions, about mean flow conditions at shock-buffet onset, and while exhibiting shock buffet. The unsteady aerodynamic response is found to be fundamentally different from the response predicted by the linear aerodynamic theory. At mean angles of attack close to buffet onset noticeable damped resonance responses are observed at frequencies close to the buffet frequency. The responses grow as the mean angle of attack is increased towards buffet onset. Also, a phase lead is observed for the aerodynamic coefficients, for some range of frequencies. The large aerodynamic responses and phase lead appear in frequencies that are typical of structural elastic frequencies, suggesting that they may be responsible for transonic aeroelastic instabilities. At shock buffet conditions, prescribing sufficiently large pitch or flap harmonic motions results in synchronization of the buffet frequency with the excitation frequencies. At these conditions, the lift and pitching moment responses to prescribed pitch motion also result in resonance and phase lead, as in the pre-buffet case. Large prescribed flap motions eliminate the lift resonance response, and significantly reduce the lift coefficient amplitudes, indicating that the aerodynamic coefficients at these conditions can be controlled by prescribed structural motions.
Directory of Open Access Journals (Sweden)
yiping wang
2014-01-01
Full Text Available The numerical simulation and wind tunnel experiment were employed to investigate the aerodynamic characteristics of three typical rear shapes: fastback, notchback and squareback. The object was to investigate the sensibility of aerodynamic characteristic to the rear shape, and provide more comprehensive experimental data as a reference to validate the numerical simulation. In the wind tunnel experiments, the aerodynamic six components of the three models with the yaw angles range from -15 and 15 were measured. The realizable k-ε model was employed to compute the aerodynamic drag, lift and surface pressure distribution at a zero yaw angle. In order to improve the calculation efficiency and accuracy, a hybrid Tetrahedron-Hexahedron-Pentahedral-Prism mesh strategy was used to discretize the computational domain. The computational results showed a good agreement with the experimental data and the results revealed that different rear shapes would induce very different aerodynamic characteristic, and it was difficult to determine the best shape. For example, the fastback would obtain very low aerodynamic drag, but it would induce positive lift which was not conducive to stability at high speed, and it also would induce bad crosswind stability. In order to reveal the internal connection between the aerodynamic drag and wake vortices, the turbulent kinetic, recirculation length, position of vortex core and velocity profile in the wake were investigated by numerical simulation and PIV experiment.
Measurement of Unsteady Aerodynamics Load on the Blade of Field Horizontal Axis Wind Turbine
Kamada, Yasunari; Maeda, Takao; Naito, Keita; Ouchi, Yuu; Kozawa, Masayoshi
This paper describes an experimental field study of the rotor aerodynamics of wind turbines. The test wind turbine is a horizontal axis wind turbine, or: HAWT with a diameter of 10m. The pressure distributions on the rotating blade are measured with multi point pressure transducers. Sectional aerodynamic forces are analyzed from pressure distribution. Blade root moments are measured simultaneously by a pair of strain gauges. The inflow wind is measured by a three component sonic anemometer, the local inflow of the blade section are measured by a pair of 7 hole Pitot tubes. The relation between the aerodynamic moments on the blade root from pressure distribution and the mechanical moment from strain gauges is discussed. The aerodynamic moments are estimated from the sectional aerodynamic forces and show oscillation caused by local wind speed and direction change. The mechanical moment shows similar oscillation to the aerodynamic excepting the short period oscillation of the blade first mode frequency. The fluctuation of the sectional aerodynamic force triggers resonant blade oscillations. Where stall is present along the blade section, the blade's first mode frequency is dominant. Without stall, the rotating frequency is dominant in the blade root moment.
Guruswamy, P.; Goorjian, P. M.
1982-01-01
Comparisons were made of computed and experimental data in three-dimensional unsteady transonic aerodynamics, including aeroelastic applications. The computer code LTRAN3, which is based on small-disturbance aerodynamic theory, was used to obtain the aerodynamic data. A procedure based on the U-g method was developed to compute flutter boundaries by using the unsteady aerodynamic coefficients obtained from LTRAN3. The experimental data were obtained from available NASA publications. All the studies were conducted for thin, unswept, rectangular wings with circular-arc cross sections. Numerical and experimental steady and unsteady aerodynamic data were compared for a wing with an aspect ratio of 3 and a thickness ratio of 5% at Mach numbers of 0.7 and 0.9. Flutter data were compared for a wing with an aspect ratio of 5. Two thickness ratios, 6% at Mach numbers of 0.715, 0.851, and 0.913, and 4% at Mach number of 0.904, were considered. Based on the unsteady aerodynamic data obtained from LTRAN3, flutter boundaries were computed; they were compared with those obtained from experiments and the code NASTRAN, which uses linear aerodynamics.
COMPUTATIONAL FLOW MODELLING OF FORMULA-SAE SIDEPODS FOR OPTIMUM RADIATOR HEAT MANAGEMENT
Directory of Open Access Journals (Sweden)
C. M. DE SILVA
2011-02-01
Full Text Available Formula SAE vehicles, over the program’s history have showcased a myriad of aerodynamic packages, each claiming specific quantitative and qualitative features. This paper attempts to critique differing aerodynamic sidepod designs and their effect upon radiator heat management. Various features from inlet size, sidepod shape and size, presence of an undertray, suspension cover, gills and chimneys are analysed for their effects. Computational Fluid Dynamics (CFD analyses are performed in the FLUENT environment, with the aid of GAMBIT meshing software and SolidWorks modelling.
Full-scale measurements of aerodynamic induction in a rotor plane
Larsen, Gunner Chr; Hansen, Kurt S.
2014-12-01
Reliable modelling of aerodynamic induction is imperative for successful prediction of wind turbine loads and wind turbine dynamics when based on state-of- the-art aeroelastic tools. Full-scale LiDAR based wind speed measurements, with high temporal and spatial resolution, have been conducted in the rotor plane of an operating 2MW/80m wind turbine to perform detailed analysis the aerodynamic induction. The experimental setup, analyses of the spatial structure of the aerodynamic induction and subsequent comparisons with numerical predictions, using the HAWC2 aerolastic code, are presented.
Full-scale measurements of aerodynamic induction in a rotor plane
DEFF Research Database (Denmark)
Larsen, Gunner Chr.; Hansen, Kurt Schaldemose
2014-01-01
in the rotor plane of an operating 2MW/80m wind turbine to perform detailed analysis the aerodynamic induction. The experimental setup, analyses of the spatial structure of the aerodynamic induction and subsequent comparisons with numerical predictions, using the HAWC2 aerolastic code, are presented.......Reliable modelling of aerodynamic induction is imperative for successful prediction of wind turbine loads and wind turbine dynamics when based on state-of- the-art aeroelastic tools. Full-scale LiDAR based wind speed measurements, with high temporal and spatial resolution, have been conducted...
Analysis of detailed aerodynamic field measurements using results from an aeroelastic code
Energy Technology Data Exchange (ETDEWEB)
Schepers, J.G. [Energy Research Centre, Petten (Netherlands); Feigl, L. [Ecotecnia S. coop.c.l. (Spain); Rooij, R. van; Bruining, A. [Delft Univ. of Technology (Netherlands)
2004-07-01
In this article an analysis is given of aerodynamic field measurements on wind turbine blades. The analysis starts with a consistency check on the measurements, by relating the measured local aerodynamic segment forces to the overall rotor loads. It is found that the results are very consistent. Moreover, a comparison is made between measured results and results calculated from an aeroelastic code. On the basis of this comparison, the aerodynamic modelling in the aeroelastic code could be improved. This holds in particular for the modelling of 3D stall effects, not only on the lift but also on the drag, and for the modelling of tip effects (author)
DEFF Research Database (Denmark)
Acampora, Antonio; Georgakis, Christos T.
2013-01-01
Moderate vibrations continue to be recorded on the Øresund Bridge twin-stay cables. System identification techniques have been applied to investigate the aerodynamic characteristics of the cables based on ambient vibration measurements. As might be expected, the measured aerodynamic damping ratios...... vary from those estimated through use of aerodynamic coefficients of single circular cylinders, as reported in literature. To address this issue, wind tunnel tests were performed on a 1:2.3 scale section model of the Øresund Bridge cables, with and without the presence of helical fillets. In this paper...
First-order aerodynamic and aeroelastic behavior of a single-blade installation setup
DEFF Research Database (Denmark)
Gaunaa, Mac; Bergami, Leonardo; Guntur, Srinivas;
2014-01-01
of arbitrary direction. The model is coupled with a schematic aeroelastic representation of the taglines system, which returns the minimum line tension required to compensate for the aerodynamic forcing. The simplified models are in excellent agreement with the aeroelastic code HAWC2, and provide a...... first-order aerodynamic and aeroelastic behavior of a single blade installation system, where the blade is grabbed by a yoke, which is lifted by the crane and stabilized by two taglines. A simple engineering model is formulated to describe the aerodynamic forcing on the blade subject to turbulent wind...
3-D Navier-Stokes Analysis of Blade Root Aerodynamics for a Tiltrotor Aircraft In Cruise
Romander, Ethan
2006-01-01
The blade root area of a tiltrotor aircraft's rotor is constrained by a great many factors, not the least of which is aerodynamic performance in cruise. For this study, Navier-Stokes CFD techniques are used to study the aerodynamic performance in cruise of a rotor design as a function of airfoil thickness along the blade and spinner shape. Reducing airfoil thickness along the entire blade will be shown to have the greatest effect followed by smaller but still significant improvements achieved by reducing the thickness of root airfoils only. Furthermore, altering the shape of the spinner will be illustrated as a tool to tune the aerodynamic performance very near the blade root.
Simultaneous Excitation of Multiple-Input Multiple-Output CFD-Based Unsteady Aerodynamic Systems
Silva, Walter A.
2008-01-01
A significant improvement to the development of CFD-based unsteady aerodynamic reduced-order models (ROMs) is presented. This improvement involves the simultaneous excitation of the structural modes of the CFD-based unsteady aerodynamic system that enables the computation of the unsteady aerodynamic state-space model using a single CFD execution, independent of the number of structural modes. Four different types of inputs are presented that can be used for the simultaneous excitation of the structural modes. Results are presented for a flexible, supersonic semi-span configuration using the CFL3Dv6.4 code.
Aerodynamics of Dragonfly in Forward Flight: Force measurements and PIV results
Hu, Zheng; Deng, Xinyan
2009-11-01
We used a pair of dynamically scaled robotic dragonfly model wings to investigate the aerodynamic effects of wing-wing interaction in dragonflies. We follow the wing kinematics of real dragonflies in forward flight, while systematically varied the phase difference between the forewing and hindwing. Instantaneous aerodynamic forces and torques were measured on both wings, while flow visualization and PIV results were obtained. The results show that, in forward flight, wing-wing interaction always enhances the aerodynamic forces on the forewing through an upwash brought by the hindwing, while reduces the forces on the hindwing through a downwash brought by the forewing.
Experimental Investigation of Unsteady Aerodynamic Forces on Airfoil in Harmonic Translatory Motion
DEFF Research Database (Denmark)
Gaunaa, Mac; Sørensen, Jens Nørkær
2003-01-01
The present paper describes the main results from an experimental investigation of the unsteady aerodynamic forces on a NACA 0015 airfoil subject to 1-degree-of-freedom (DOF) harmonic translatory motion. The focus of the experimental investigations was to determine the factors that influence the...... aerodynamic damping of harmonic translatory motion. The maximum negative aerodynamic damping was found to take place at moderate stall and an incidence of about 15, at a movement derection close to the chordwise direction. Up to three distinctively different stall modes (multiple stall) were observed near...
Aerodynamic Analysis of the Truss-Braced Wing Aircraft Using Vortex-Lattice Superposition Approach
Ting, Eric Bi-Wen; Reynolds, Kevin Wayne; Nguyen, Nhan T.; Totah, Joseph J.
2014-01-01
The SUGAR Truss-BracedWing (TBW) aircraft concept is a Boeing-developed N+3 aircraft configuration funded by NASA ARMD FixedWing Project. This future generation transport aircraft concept is designed to be aerodynamically efficient by employing a high aspect ratio wing design. The aspect ratio of the TBW is on the order of 14 which is significantly greater than those of current generation transport aircraft. This paper presents a recent aerodynamic analysis of the TBW aircraft using a conceptual vortex-lattice aerodynamic tool VORLAX and an aerodynamic superposition approach. Based on the underlying linear potential flow theory, the principle of aerodynamic superposition is leveraged to deal with the complex aerodynamic configuration of the TBW. By decomposing the full configuration of the TBW into individual aerodynamic lifting components, the total aerodynamic characteristics of the full configuration can be estimated from the contributions of the individual components. The aerodynamic superposition approach shows excellent agreement with CFD results computed by FUN3D, USM3D, and STAR-CCM+. XXXXX Demand for green aviation is expected to increase with the need for reduced environmental impact. Most large transports today operate within the best cruise L/D range of 18-20 using the conventional tube-and-wing design. This configuration has led to marginal improvements in aerodynamic efficiency over this past century, as aerodynamic improvements tend to be incremental. A big opportunity has been shown in recent years to significantly reduce structural weight or trim drag, hence improved energy efficiency, with the use of lightweight materials such as composites. The Boeing 787 transport is an example of a modern airframe design that employs lightweight structures. High aspect ratio wing design can provide another opportunity for further improvements in energy efficiency. Historically, the study of high aspect ratio wings has been intimately tied to the study of
Effects of aerodynamic particle interaction in turbulent non-dilute particle-laden flow
DEFF Research Database (Denmark)
Salewski, Mirko; Fuchs, Laszlo
2008-01-01
decreases by more than 40% in the dense particle region in the near-field of the jet due to the introduction of aerodynamic four-way coupling. The jet of monodisperse particles therefore penetrates further into the crossflow in this case. The strength of the counterrotating vortex pair (CVP) and turbulence...... is applied to simulate monodisperse, rigid, and spherical particles injected into crossflow as an idealization of a spray jet in crossflow. A domain decomposition technique reduces the computational cost of the aerodynamic particle interaction model. It is shown that the average drag on such particles...... particles under such conditions is suggested. In this idealized atomizing mixture, the effect of aerodynamic four-way coupling reverses: The aerodynamic particle interaction results in a stronger CVP and enhances turbulence levels....
Study of Aerodynamic Design Procedure of a Large-Scale Aircraft Noise Suppression Facility
Kawai, Masafumi; Nagai, Kiyoyuki; Aso, Shigeru
The aerodynamic design procedure of a large-scale aircraft noise suppression facility has been developed. Flow quality required for the engine inlet flow has been determined through basic experiment. Aerodynamic design of the facility has been performed by using wind tunnel experiment and CFD. Important relationship between the length of the facility and the inlet flow quality has been found. The operational envelope of the designed facility has been estimated. Then, the aerodynamic characteristics of an actual large-scale aircraft noise suppression facility, constructed based on the new design procedure, have been measured. Obtained flow field showed good agreement with CFD results, and the effectiveness of the design procedure based on CFD and wind tunnel experiment has been confirmed. The engine operations were satisfactory under various wind conditions. Furthermore, the data under commercial operations thereafter have been collected and analyzed. As the result, the aerodynamic design procedure has been validated.
Nonlinear Aerodynamics-Structure Time Simulation for HALE Aircraft Design/Analysis Project
National Aeronautics and Space Administration — Time simulation of a nonlinear aerodynamics model (NA) developed at Virginia Tech coupled with a nonlinear structure model (NS) is proposed as a design/analysis...
A NEW GENERAL 3DOF QUASI-STEADY AERODYNAMIC INSTABILITY MODEL
DEFF Research Database (Denmark)
Gjelstrup, Henrik; Larsen, Allan; Georgakis, Christos;
2008-01-01
but can generally be applied for aerodynamic instability prediction for prismatic bluff bodies. The 3DOF, which make up the movement of the model, are the displacements in the XY-plane and the rotation around the bluff body’s rotational axis. The proposed model incorporates inertia coupling between......This paper proposes a three degrees of freedom (3DOF) quasi-steady aerodynamic model and instability criterion for a bluff body which is uniform along the length axis. The model and criterion has been developed in the frame of investigating aerodynamic instability of cables due to ice accretions...... the three degrees of freedom and is capable of estimating the onset of aerodynamic instability for changes in drag, lift and moment, which is a function of wind angle of attack in relation to the x-axis of the bluff body, Reynolds number and wind angle in relation to the length axis of the bluff body...
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.
Aerodynamic Study about an Automotive Vehicle with Capacity for Only One Occupan
Directory of Open Access Journals (Sweden)
Almeida R.A
2016-04-01
Full Text Available The presented study describes the aerodynamic behavior of a compact, single occupant, automotive vehicle. To optimize the aerodynamic characteristics of this vehicle, a flow dynamics study was conducted using a virtual model. The outer surfaces of the vehicle body were designed using Computer Aided Design (CAD tools and its aerodynamic performance simulated virtually using Computational Fluid Dynamics (CFD software. Parameters such as pressure coefficient (Cp, coefficient of friction (Cf and graphical analysis of the streamlines were used to understand the flow dynamics and propose recommendations aimed at improving the coefficient of drag (Cd. The identification of interaction points between the fluid and the flow structure was the primary focus of study to develop these propositions. The study of phenomena linked to the characteristics of the model presented here, allowed the identification of design features that should be avoided to generate improved aerodynamic performance
Numerical simulations of the aerodynamic behavior of large horizontal-axis wind turbines
Energy Technology Data Exchange (ETDEWEB)
Gebhardt, C.G. [Departamento de Estructuras, Facultad de Ciencias Exactas Fisicas y Naturales, Universidad Nacional de Cordoba, Av. Velez Sarsfield N 1611, CP 5000, Cordoba (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, Avenida Rivadavia 1917, CP C1033AAJ, Ciudad de Buenos Aires (Argentina); Preidikman, S. [Departamento de Estructuras, Facultad de Ciencias Exactas Fisicas y Naturales, Universidad Nacional de Cordoba, Av. Velez Sarsfield N 1611, CP 5000, Cordoba (Argentina); Departamento de Mecanica, Facultad de Ingenieria, Universidad Nacional de Rio, Cuarto, Ruta Nacional 36, Km 601, CP 5800, Rio Cuarto (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, Avenida Rivadavia 1917, CP C1033AAJ, Ciudad de Buenos Aires (Argentina); Massa, J.C. [Departamento de Estructuras, Facultad de Ciencias Exactas Fisicas y Naturales, Universidad Nacional de Cordoba, Av. Velez Sarsfield N 1611, CP 5000, Cordoba (Argentina); Departamento de Mecanica, Facultad de Ingenieria, Universidad Nacional de Rio, Cuarto, Ruta Nacional 36, Km 601, CP 5800, Rio Cuarto (Argentina)
2010-06-15
In the present work, the non-linear and unsteady aerodynamic behavior of large horizontal-axis wind turbines is analyzed. The flowfield around the wind turbine is simulated with the general non-linear unsteady vortex-lattice method, widely used in aerodynamics. By using this technique, it is possible to compute the aerodynamic loads and their evolution in the time domain. The results presented in this paper help to understand how the existence of the land-surface boundary layer and the presence of the turbine support tower, affect its aerodynamic efficiency. The capability to capture these phenomena is a novel aspect of the computational tool developed in the present effort. (author)
Institute of Scientific and Technical Information of China (English)
Zhiwen LIU; Zhengqing CHEN; Gao LIU; Xinpeng SHAO
2009-01-01
The aerodynamic interference effects on aero-static coefficients of twin deck bridges with large span were investigated in detail by means of wind tunnel test.The distances between the twin decks and wind attack angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of twin decks. The research results have shown that the drag coefficients of the leeward deck are much smaller than that of a single leeward deck. The drag coefficients of a windward deck decrease slightly com-pared with that of a single deck. The lift and torque coefficients of windward and leeward decks are also affected slightly by the aerodynamic interference of twin decks. And the aerodynamic interference effects on lift and torque coefficients of twin decks can be neglected.
Experimental Study of Aerodynamic Behavior in Wind Tunnels with Ornithopter and Plane Models
Institute of Scientific and Technical Information of China (English)
Marie-Francoise SCIBILIA; Jan WOJCIECHOWSKI
2006-01-01
There are similarities between planes and birds. In fact aerodynamics bases are the same. In order to make some comparisons, this paper presents two series of experiments: one in a wind tunnel with an ornithopter model for measurements of aerodynamic forces with flapping wings. The wing movement has two degrees of freedom flapping around the longitudinal axis of the model and feathering around the wing axis. Measurements of aerodynamic forces: lift and drag in static case averaging values during many cycles of movement and in dynamic case have been performed. The other part of the paper concerns velocity and turbulence measurements on a metal plane wall jet in a wind tunnel with and without a rough surface, with and without acoustic vibrations in order to simulate a plane wing. Aerodynamic characteristics have been obtained in all cases.
Wind tunnel study of aerodynamic wind loading on middle pylon of Taizhou Bridge
Institute of Scientific and Technical Information of China (English)
Zhang Zhen; Ma Rujin; Hu Xiaohong; Chen Airong
2011-01-01
Segment sectional model tests are carried out to investigate the wind loading on middle pylon of Taizhou Bridge, which has complicated three-dimension al flow due to its feature of double columns. Through the force measuring tests, aerodynamic force coefficients of every segment of the pylon columns have been obtained. It is found that the tested aerodynamic force coefficients are much smaller than those given by codes. The interference effects of aerody namic force coefficients between columns of pylon are discussed. The results show that the interference effect is the most evident when the yaw angle is about 30° from transverse direction. This kind of interference effect can be described as diminutions in transverse aerodynamic force coefficients and magnifications in longitudinal aerodynamic force coefficients of downstream columns.
Aerodynamic Analysis of a Manned Space Vehicle for Missions to Mars
Directory of Open Access Journals (Sweden)
Giuseppe Pezzella
2011-01-01
Full Text Available The paper deals with the aerodynamic analysis of a manned braking system entering the Mars atmosphere with the aim to support planetary entry system design studies. The exploration vehicle is an axisymmetric blunt body close to the Apollo capsule. Several fully three-dimensional computational fluid dynamics analyses have been performed to address the capsule aerodynamic performance. To this end, a wide range of flow conditions including reacting and nonreacting flow, different angles of attack, and Mach numbers have been investigated and compared. Moreover, nonequilibrium effects on the flow field around the entry vehicle have also been investigated. Results show that real-gas effects, for all the angles of attack considered, increase both the aerodynamic drag and pitching moment whereas the lift is only slighted affected. Finally, results comparisons highlight that experimental and CFD aerodynamic findings available for the Apollo capsule in air adequately represent the static coefficients of the capsule in the Mars atmosphere.
Measuring Shear Stress with a Microfluidic Sensor to improve Aerodynamic Efficiency Project
National Aeronautics and Space Administration — Skin friction drag is directly proportional to the local shear stress of a surface and can be the largest factor in an aerodynamic body's total parasitic drag. The...
Energy Technology Data Exchange (ETDEWEB)
Matha, D.; Schlipf, M.; Cordle, A.; Pereira, R.; Jonkman, J.
2011-10-01
This paper presents the current major modeling challenges for floating offshore wind turbine design tools and describes aerodynamic and hydrodynamic effects due to rotor and platform motions and usage of non-slender support structures.
Dunn, Peter D
1994-01-01
It is approximately 10 years since the Third Edition of Heat Pipes was published and the text is now established as the standard work on the subject. This new edition has been extensively updated, with revisions to most chapters. The introduction of new working fluids and extended life test data have been taken into account in chapter 3. A number of new types of heat pipes have become popular, and others have proved less effective. This is reflected in the contents of chapter 5. Heat pipes are employed in a wide range of applications, including electronics cooling, diecasting and injection mo
Pseudo random interpretation of double hinged ALP under aerodynamic loading
Directory of Open Access Journals (Sweden)
Moazzam Aslam
2016-09-01
Full Text Available Wind produces three different types of effects on structure: static, dynamic and aerodynamic. When the structure deflects in response to wind load then the dynamic and aerodynamic effects should be analysed. The basic mode of an articulated tower is the motion characterized by rigid body sway compliant with a relatively high natural period. The higher modes of oscillation have smaller periods, and their influence is rather insignificant in the overall platform motion. Since the wind velocity spectrum of the fluctuating component has lower frequency energy content, the wind induced vibration of an articulated tower may be significant. The wind induced overturning moment increases linearly with the height of the structure, and thus, as these structures are built in deep and deeper water, the effects of wind drag then become increasingly significant in design. To approach towards the realistic environment, the dynamic analysis of double-hinged articulated tower under the action of wind, waves and current has been carried out. The wave forces with the interaction of current have been computed by the application of Stokes’ fifth order nonlinear wave theory. The sea state with respect to wind speed of 25 m/s (Hs = 18.03 m, Tz = 13.59 s has been considered and standard wind velocity spectrum Ahsan Kareem has been used for the dynamic analysis. The Pierson Moskowitz sea surface elevation spectrum has been used to model the random wave loads. The responses have been obtained under multi-point wind field. The study shows that energy content under combined action of wave and wind forces is more than energy derived under wave alone forces. Results also show that upper hinge is more dynamically active than lower hinge due to wind forces. PSDF shows that wind forces do not practically affect the bending moment, which is predominantly governed by the second mode of frequency; however, the other response parameters like deck displacement, hinge
Experimental characterization of high speed centrifugal compressor aerodynamic forcing functions
Gallier, Kirk
The most common and costly unexpected post-development gas turbine engine reliability issue is blade failure due to High Cycle Fatigue (HCF). HCF in centrifugal compressors is a coupled nonlinear fluid-structure problem for which understanding of the phenomenological root causes is incomplete. The complex physics of this problem provides significant challenges for Computational Fluid Dynamics (CFD) techniques. Furthermore, the available literature fails to address the flow field associated with the diffuser potential field, a primary cause of forced impeller vibration. Because of the serious nature of HCF, the inadequacy of current design approaches to predict HCF, and the fundamental lack of benchmark experiments to advance the design practices, there exists a need to build a database of information specific to the nature of the diffuser generated forcing function as a foundation for understanding flow induced blade vibratory failure. The specific aim of this research is to address the fundamental nature of the unsteady aerodynamic interaction phenomena inherent in high-speed centrifugal compressors wherein the impeller exit flow field is dynamically modulated by the vaned diffuser potential field or shock structure. The understanding of this unsteady aerodynamic interaction is fundamental to characterizing the impeller forcing function. Unsteady static pressure measurement at several radial and circumferential locations in the vaneless space offer a depiction of pressure field radial decay, circumferential variation and temporal fluctuation. These pressure measurements are coupled with high density, full field measurement of the velocity field within the diffuser vaneless space at multiple spanwise positions. The velocity field and unsteady pressure field are shown to be intimately linked. A strong momentum gradient exiting the impeller is shown to extend well across the vaneless space and interact with the diffuser vane leading edge. The deterministic unsteady
Aerodynamic Surface Stress Intermittency and Conditionally Averaged Turbulence Statistics
Anderson, W.
2015-12-01
Aeolian erosion of dry, flat, semi-arid landscapes is induced (and sustained) by kinetic energy fluxes in the aloft atmospheric surface layer. During saltation -- the mechanism responsible for surface fluxes of dust and sediment -- briefly suspended sediment grains undergo a ballistic trajectory before impacting and `splashing' smaller-diameter (dust) particles vertically. Conceptual models typically indicate that sediment flux, q (via saltation or drift), scales with imposed aerodynamic (basal) stress raised to some exponent, n, where n > 1. Since basal stress (in fully rough, inertia-dominated flows) scales with the incoming velocity squared, u^2, it follows that q ~ u^2n (where u is some relevant component of the above flow field, u(x,t)). Thus, even small (turbulent) deviations of u from its time-averaged value may play an enormously important role in aeolian activity on flat, dry landscapes. The importance of this argument is further augmented given that turbulence in the atmospheric surface layer exhibits maximum Reynolds stresses in the fluid immediately above the landscape. In order to illustrate the importance of surface stress intermittency, we have used conditional averaging predicated on aerodynamic surface stress during large-eddy simulation of atmospheric boundary layer flow over a flat landscape with momentum roughness length appropriate for the Llano Estacado in west Texas (a flat agricultural region that is notorious for dust transport). By using data from a field campaign to measure diurnal variability of aeolian activity and prevailing winds on the Llano Estacado, we have retrieved the threshold friction velocity (which can be used to compute threshold surface stress under the geostrophic balance with the Monin-Obukhov similarity theory). This averaging procedure provides an ensemble-mean visualization of flow structures responsible for erosion `events'. Preliminary evidence indicates that surface stress peaks are associated with the passage of
Comparative Analysis of Uninhibited and Constrained Avian Wing Aerodynamics
Cox, Jordan A.
The flight of birds has intrigued and motivated man for many years. Bird flight served as the primary inspiration of flying machines developed by Leonardo Da Vinci, Otto Lilienthal, and even the Wright brothers. Avian flight has once again drawn the attention of the scientific community as unmanned aerial vehicles (UAV) are not only becoming more popular, but smaller. Birds are once again influencing the designs of aircraft. Small UAVs operating within flight conditions and low Reynolds numbers common to birds are not yet capable of the high levels of control and agility that birds display with ease. Many researchers believe the potential to improve small UAV performance can be obtained by applying features common to birds such as feathers and flapping flight to small UAVs. Although the effects of feathers on a wing have received some attention, the effects of localized transient feather motion and surface geometry on the flight performance of a wing have been largely overlooked. In this research, the effects of freely moving feathers on a preserved red tailed hawk wing were studied. A series of experiments were conducted to measure the aerodynamic forces on a hawk wing with varying levels of feather movement permitted. Angle of attack and air speed were varied within the natural flight envelope of the hawk. Subsequent identical tests were performed with the feather motion constrained through the use of externally-applied surface treatments. Additional tests involved the study of an absolutely fixed geometry mold-and-cast wing model of the original bird wing. Final tests were also performed after applying surface coatings to the cast wing. High speed videos taken during tests revealed the extent of the feather movement between wing models. Images of the microscopic surface structure of each wing model were analyzed to establish variations in surface geometry between models. Recorded aerodynamic forces were then compared to the known feather motion and surface
Aerodynamic study on wing and tail small UAV without runways
Soetanto, Maria F.; R., Randy; Alfan M., R.; Dzaldi
2016-06-01
This paper consists of the design and analysis of the aerodynamics of the profiles of wing and tail of a Small Unmanned Aerial Vehicle (UAV). UAV is a remote-controlled aircraft that can carry cameras, sensors and even weapons on an area that needed aerial photography or aerial video [1]. The aim of this small UAV is for used in situations where manned flight is considered too risky or difficult, such as fire fighting or surveillance, while the term 'small means the design of this UAV has to be relatively small and portable so that peoples are able to carry it during their operations [CASR Part 101.240: it is a UAV which is has a launch mass greater than 100 grams but less than 100 kilograms] [2]. Computational Fluid Dynamic (CFD) method was used to analyze the fluid flow characteristics around the aerofoil's profiles, such as the lift generation for each angle of attack and longitudinal stability caused by vortex generation on trailing edge. Based on the analysis and calculation process, Clark-Y MOD with aspect ratio, AR = 4.28 and taper ratio, λ = 0.65 was chosen as the wing aerofoil and SD 8020 with AR = 4.8 and λ = 0.5 was chosen as the horizontal tail, while SD 8020 with AR = 1.58 and λ = 0.5 was chosen as the vertical tail. The lift and drag forces generated for wing and tail surfaces can be determined from the Fluent 6.3 simulation. Results showed that until angle of attack of 6 degrees, the formation of flow separation is still going on behind the trailing edge, and the stall condition occurs at 14 degrees angle of attack which is characterized by the occurrence of flow separation at leading edge, with a maximum lift coefficient (Cl) obtained = 1.56. The results of flight tests show that this small UAV has successfully maneuvered to fly, such as take off, some acrobatics when cruising and landing smoothly, which means that the calculation and analysis of aerodynamic aerofoil's profile used on the wing and tail of the Small UAV were able to be validated.
Hua YANG; Shen, Wen Zhong; Xu, Haoran; Hong, Zedong; Liu, Chao
2013-01-01
Blade Element Momentum (BEM) theory is a widely used technique for prediction of wind turbine aerodynamics performance, but the reliability of airfoil data is an important factor to improve the prediction accuracy of aerodynamic loads and power using a BEM code. The airfoil characteristics used in BEM codes are mostly based on 2D wind tunnel measurements of airfoils with constant span. However, a BEM code using airfoil data obtained directly from 2D wind tunnel measurements will not yield the...
Aerodynamic Measurements in a Wind Tunnel on Scale Models of a 777 Main Landing Gear
Ringshia, Aditya K
2006-01-01
Aerodynamic measurements were taken over models of the Boeing 777 high fidelity isolated landing gear in the 6- by 6-foot Virginia Tech Stability Wind Tunnel (VT-SWT) at a free-stream Mach number of 0.16. Noise control devices (NCD) were developed at Virginia Tech [9] to reduce noise by shielding gear components, reducing wake interactions and by streamlining the flow around certain landing gear components. Aerodynamic measurements were performed to understand the flow over the landing gear a...
Novel Strategies for Aerodynamic Performance Improvement of Wind Turbines in Turbulent Flow
Al-Abadi, Ali
2014-01-01
In this thesis, the influence of the turbulence on the performance of the Horizontal Axis Wind Turbine (HAWT) has been investigated. For that numerical optimizations for aerodynamic shape design, pitch-control, analysis and semi-empirical performance predictions are developed. These methods are numerically and experimentally validated. First, a turbine Torque-Matched Aerodynamic Shape Optimization method (TMASO) which maximizes the power while matching the drive unit torque has been develo...
Comparing Aerodynamic Efficiency in Birds and Bats Suggests Better Flight Performance in Birds
Muijres, Florian T.; L. Christoffer Johansson; Melissa S Bowlin; York Winter; Anders Hedenström
2012-01-01
Flight is one of the energetically most costly activities in the animal kingdom, suggesting that natural selection should work to optimize flight performance. The similar size and flight speed of birds and bats may therefore suggest convergent aerodynamic performance; alternatively, flight performance could be restricted by phylogenetic constraints. We test which of these scenarios fit to two measures of aerodynamic flight efficiency in two passerine bird species and two New World leaf-nosed ...
1983-01-01
Analytical design and wind tunnel test evaluations covering the feasibility of applying wing tip extensions, winglets, and active control wing had alleviation to the model B747 are described. Aerodynamic improvement offered by wing tip extension and winglet individually, and the combined aerodynamic and weight improvements when wing load alleviation is combined with the tip extension or the winglet are evaluated. Results are presented in the form of incremental effects on weight mission range, fuel usage, cost, and airline operating economics.
Numerical Calculation of Effect of Elastic Deformation on Aerodynamic Characteristics of a Rocket
Laith K. Abbas; Dongyang Chen; Xiaoting Rui
2014-01-01
The application and workflow of Computational Fluid Dynamics (CFD)/Computational Structure Dynamics (CSD) on solving the static aeroelastic problem of a slender rocket are introduced. To predict static aeroelastic behavior accurately, two-way coupling and inertia relief methods are used to calculate the static deformations and aerodynamic characteristics of the deformed rocket. The aerodynamic coefficients of rigid rocket are computed firstly and compared with the experimental data, which ver...
Characteristics of aerodynamic sound sources generated by coiled wires in a uniform air-flow
Matsumoto, H.; Nishida, K.; Saitoh, K.
2003-11-01
This study deals experimentally with aerodynamic sounds generated by coiled wires in a uniform air-flow. The coiled wire is a model of the hair dryer's heater. In the experiment, the effects of the coil diameter D, wire diameter d and coil spacing s of the coiled wire on the aerodynamic sound have been clarified. The results of frequency analyses of the aerodynamic sounds show that an Aeolian sound is generated by the coiled wire, when s/d is larger than 1. Also the peak frequencies of Aeolian sounds generated by the coiled wires are higher than the ones generated by a straight cylinder having the same diameter d. To clarify the characteristics of the aerodynamic sound sources, the directivity of the aerodynamic sound generated by the coiled wire has been examined, and the coherent function between the velocity fluctuation around the coiled wire and the aerodynamic sound has been calculated. Moreover, the band overall value of coherent output power between the sound and the velocity fluctuations has been calculated. This method has clarified the sound source region of the Aeolian sound generated by the coiled wire. These results show that the Aeolian sound is generated by the arc part of the coiled wire, which is located in the upstream side of the air-flow.
Unsteady Aerodynamics Experiment Phase V: Test Configuration and Available Data Campaigns; TOPICAL
International Nuclear Information System (INIS)
The main objective of the Unsteady Aerodynamics Experiment is to provide information needed to quantify the full-scale, three-dimensional, unsteady aerodynamic behavior of horizontal-axis wind turbines (HAWTs). To accomplish this, an experimental wind turbine configured to meet specific research objectives was assembled and operated at the National Renewable Energy Laboratory (NREL). The turbine was instrumented to characterize rotating-blade aerodynamic performance, machine structural responses, and atmospheric inflow conditions. Comprehensive tests were conducted with the turbine operating in an outdoor field environment under diverse conditions. Resulting data are used to validate aerodynamic and structural dynamics models, which are an important part of wind turbine design and engineering codes. Improvements in these models are needed to better characterize aerodynamic response in both the steady-state post-stall and dynamic-stall regimes. Much of the effort in the first phase of the Unsteady Aerodynamics Experiment focused on developing required data acquisition systems. Complex instrumentation and equipment was needed to meet stringent data requirements while operating under the harsh environmental conditions of a wind turbine rotor. Once the data systems were developed, subsequent phases of experiments were then conducted to collect data for use in answering specific research questions. A description of the experiment configuration used during Phase V of the experiment is contained in this report
Bayesian inference of nonlinear unsteady aerodynamics from aeroelastic limit cycle oscillations
Sandhu, Rimple; Poirel, Dominique; Pettit, Chris; Khalil, Mohammad; Sarkar, Abhijit
2016-07-01
A Bayesian model selection and parameter estimation algorithm is applied to investigate the influence of nonlinear and unsteady aerodynamic loads on the limit cycle oscillation (LCO) of a pitching airfoil in the transitional Reynolds number regime. At small angles of attack, laminar boundary layer trailing edge separation causes negative aerodynamic damping leading to the LCO. The fluid-structure interaction of the rigid, but elastically mounted, airfoil and nonlinear unsteady aerodynamics is represented by two coupled nonlinear stochastic ordinary differential equations containing uncertain parameters and model approximation errors. Several plausible aerodynamic models with increasing complexity are proposed to describe the aeroelastic system leading to LCO. The likelihood in the posterior parameter probability density function (pdf) is available semi-analytically using the extended Kalman filter for the state estimation of the coupled nonlinear structural and unsteady aerodynamic model. The posterior parameter pdf is sampled using a parallel and adaptive Markov Chain Monte Carlo (MCMC) algorithm. The posterior probability of each model is estimated using the Chib-Jeliazkov method that directly uses the posterior MCMC samples for evidence (marginal likelihood) computation. The Bayesian algorithm is validated through a numerical study and then applied to model the nonlinear unsteady aerodynamic loads using wind-tunnel test data at various Reynolds numbers.
Estimation of Aircraft Unsteady Aerodynamic Parameters from Dynamic Wind Tunnel Testing
Murphy, Patrick C.; Klein, Vladislav
2001-01-01
Improved aerodynamic mathematical models, for use in aircraft simulation or flight control design, are required when representing nonlinear unsteady aerodynamics. A key limitation of conventional aerodynamic models is the inability to map frequency and amplitude dependent data into the equations of motion directly. In an effort to obtain a more general formulation of the aerodynamic model, researchers have been led to a parallel requirement for more general testing methods. Testing for a more comprehensive model can lead to a very time consuming number of tests especially if traditional single frequency harmonic testing is attempted. This paper presents an alternative to traditional single frequency forced-oscillation testing by utilizing Schroeder sweeps to efficiently obtain the frequency response of the unsteady aerodynamic model. Schroeder inputs provide signals with a flat power spectrum over a specified frequency band. For comparison, experimental results using the traditional single-frequency inputs are also considered. A method for data analysis to determine an adequate unsteady aerodynamic model is presented. Discussion of associated issues that arise during this type of analysis and comparison of results using traditional single frequency analysis are provided.
Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics
LaGraff, John E.; Povinelli, Louis A.; Gostelow, J. Paul; Glauser, Mark
2010-01-01
Topics covered include: Flow Physics and control for Internal and External Aerodynamics (not in TOC...starts on pg13); Breaking CFD Bottlenecks in Gas-Turbine Flow-Path Design; Streamwise Vortices on the Convex Surfaces of Circular Cylinders and Turbomachinery Blading; DNS and Embedded DNS as Tools for Investigating Unsteady Heat Transfer Phenomena in Turbines; Cavitation, Flow Structure and Turbulence in the Tip Region of a Rotor Blade; Development and Application of Plasma Actuators for Active Control of High-Speed and High Reynolds Number Flows; Active Flow Control of Lifting Surface With Flap-Current Activities and Future Directions; Closed-Loop Control of Vortex Formation in Separated Flows; Global Instability on Laminar Separation Bubbles-Revisited; Very Large-Scale Motions in Smooth and Rough Wall Boundary Layers; Instability of a Supersonic Boundary-Layer With Localized Roughness; Active Control of Open Cavities; Amplitude Scaling of Active Separation Control; U.S. Air Force Research Laboratory's Need for Flow Physics and Control With Applications Involving Aero-Optics and Weapon Bay Cavities; Some Issues Related to Integrating Active Flow Control With Flight Control; Active Flow Control Strategies Using Surface Pressure Measurements; Reduction of Unsteady Forcing in a Vaned, Contra-Rotating Transonic Turbine Configuration; Active Flow Control Stator With Coanda Surface; Controlling Separation in Turbomachines; Flow Control on Low-Pressure Turbine Airfoils Using Vortex Generator Jets; Reduced Order Modeling Incompressible Flows; Study and Control of Flow Past Disk, and Circular and Rectangular Cylinders Aligned in the Flow; Periodic Forcing of a Turbulent Axisymmetric Wake; Control of Vortex Breakdown in Critical Swirl Regime Using Azimuthal Forcing; External and Turbomachinery Flow Control Working Group; Boundary Layers, Transitions and Separation; Efficiency Considerations in Low Pressure Turbines; Summary of Conference; and Final Plenary Session
Beloborodov, Andrei M
2016-01-01
We examine four candidate mechanisms that could explain the high surface temperatures of magnetars. (1) Heat flux from the liquid core heated by ambipolar diffusion. It could sustain the observed surface luminosity $L_s\\approx 10^{35}$ erg s$^{-1}$ if core heating offsets neutrino cooling at a temperature $T_{\\rm core}>6\\times 10^8$ K. This scenario is viable if the core magnetic field exceeds $10^{16}$ G, the magnetar has mass $M10^{16}$ G varying on a 100 meter scale could provide $L_s\\approx 10^{35}$ erg s$^{-1}$. (4) Bombardment of the stellar surface by particles accelerated in the magnetosphere. This mechanism produces hot spots on magnetars. Observations of transient magnetars show evidence for external heating.
Landing Gear Aerodynamic Noise Prediction Using Building-Cube Method
Directory of Open Access Journals (Sweden)
Daisuke Sasaki
2012-01-01
Full Text Available Landing gear noise prediction method is developed using Building-Cube Method (BCM. The BCM is a multiblock-structured Cartesian mesh flow solver, which aims to enable practical large-scale computation. The computational domain is composed of assemblage of various sizes of building blocks where small blocks are used to capture flow features in detail. Because of Cartesian-based mesh, easy and fast mesh generation for complicated geometries is achieved. The airframe noise is predicted through the coupling of incompressible Navier-Stokes flow solver and the aeroacoustic analogy-based Curle’s equation. In this paper, Curle’s equation in noncompact form is introduced to predict the acoustic sound from an object in flow. This approach is applied to JAXA Landing gear Evaluation Geometry model to investigate the influence of the detail components to flows and aerodynamic noises. The position of torque link and the wheel cap geometry are changed to discuss the influence. The present method showed good agreement with the preceding experimental result and proved that difference of the complicated components to far field noise was estimated. The result also shows that the torque link position highly affects the flow acceleration at the axle region between two wheels, which causes the change in SPL at observation point.
Plume aerodynamic effects of cushion engine in lunar landing
Institute of Scientific and Technical Information of China (English)
He Bijiao; He Xiaoying; Zhang Mingxing; Cai Guobiao
2013-01-01
During the second period of China “Tanyue” Project,the explorer will softland on the moon.The cushion engines are used to decelerate the explorer and reduce the impact on the lunar ground.It is necessary to study its plume effects on the explorer component.The self-developed PWS (Plume WorkStation) software based on direct simulation Monte Carlo (DSMC) method is used to simulate the plume effects of two 150 N engines.Due to the complex structure of the explorer,PWS uses a decoupling method to treat the boundary mesh,which mainly interacts with simulation particles,and has no relation with the computational grids.After the analytical expressions of plane surfaces and curved surfaces of each boundary block are given,the particle position within or without the boundary blocks can be easily determined.Finally the 3D plume field of two 150 N engines is simulated.The pressure,temperature and velocity distributions of plume field are clearly presented by three characteristic slices.The aerodynamic effects on the explorer bottom,the landfall legs and antenna are separately shown.The compression influence on the plume flow of four landfall legs can be observed.
Drones for aerodynamic and structural testing /DAST/ - A status report
Murrow, H. N.; Eckstrom, C. V.
1978-01-01
A program for providing research data on aerodynamic loads and active control systems on wings with supercritical airfoils in the transonic speed range is described. Analytical development, wind tunnel tests, and flight tests are included. A Firebee II target drone vehicle has been modified for use as a flight test facility. The program currently includes flight experiments on two aeroelastic research wings. The primary purpose of the first flight experiment is to demonstrate an active control system for flutter suppression on a transport-type wing. Design and fabrication of the wing are complete and after installing research instrumentation and the flutter suppression system, flight testing is expected to begin in early 1979. The experiment on the second research wing - a fuel-conservative transport type - is to demonstrate multiple active control systems including flutter suppression, maneuver load alleviation, gust load alleviation, and reduce static stability. Of special importance for this second experiment is the development and validation of integrated design methods which include the benefits of active controls in the structural design.
Aerodynamic Characteristics of Airfoils with Blunt Trailing Edge
Directory of Open Access Journals (Sweden)
Alejandro Gómez
2006-11-01
Full Text Available El siguiente trabajo estudia de manera computacional el comportamiento de las características aerodinámicas de perfiles NACA (National Advisory Committee for Aeronautics, hoy conocido como NASA, con modificaciones en el borde de salida. Las modificaciones consisten en remover secciones del borde de fuga del perfil. La investigación realizada estudia 39 perfiles diferentes de la familia NACA de 4 dígitos, con modelos teóricos sencillos para explicar los fenómenos. Los resultados muestran los cambios en las características de sustentación y arrastre del perfil, y cambios en cuanto a la entrada en pérdida del mismo./ This paper is a computational study of the behaviour of aerodynamic characteristics of NACA (National Advisory Committee for Aeronautics, today known as NASA profiles with tailored trailing edges. 39 different profiles 4-digit NACA family were studied during the research. A computational research was made, using simple theoretical models to explain and to understand the results. The results describe the changes in lift and drag characteristics and changes in stall angle of attack.
Aerodynamic study of a small horizontal-axis wind turbine
Directory of Open Access Journals (Sweden)
Cornelia NITA
2012-06-01
Full Text Available The wind energy is deemed as one of the most durable energetic variants of the future because the wind resources are immense. Furthermore, one predicts that the small wind turbine will play a vital role in the urban environment. Unfortunately, nowadays, the noise emissions from wind turbines represent one of the main obstacles to widespread the use in populated zones. Moreover, the energetic efficiency of these wind turbines has to be high even at low and medium wind velocities because, usually the cities are not windy places. The numerical results clearly show that the wakes after the trailing edge are the main noise sources. In order to decrease the power of these noise sources, we should try to decrease the intensity of wakes after the trailing edge, i.e. the aerodynamic fields from pressure and suction sides would have to be almost the same near trailing edge. Furthermore, one observes a strong link between transport (circumferential velocity and acoustic power level, i.e. if the transport velocity increases, the acoustic power level also augments.
Accurate measurement of streamwise vortices in low speed aerodynamic flows
Waldman, Rye M.; Kudo, Jun; Breuer, Kenneth S.
2010-11-01
Low Reynolds number experiments with flapping animals (such as bats and small birds) are of current interest in understanding biological flight mechanics, and due to their application to Micro Air Vehicles (MAVs) which operate in a similar parameter space. Previous PIV wake measurements have described the structures left by bats and birds, and provided insight to the time history of their aerodynamic force generation; however, these studies have faced difficulty drawing quantitative conclusions due to significant experimental challenges associated with the highly three-dimensional and unsteady nature of the flows, and the low wake velocities associated with lifting bodies that only weigh a few grams. This requires the high-speed resolution of small flow features in a large field of view using limited laser energy and finite camera resolution. Cross-stream measurements are further complicated by the high out-of-plane flow which requires thick laser sheets and short interframe times. To quantify and address these challenges we present data from a model study on the wake behind a fixed wing at conditions comparable to those found in biological flight. We present a detailed analysis of the PIV wake measurements, discuss the criteria necessary for accurate measurements, and present a new dual-plane PIV configuration to resolve these issues.
Experimental Characterization of Wind Turbine Blade Aerodynamic Noise
Ingemanson, Megan Lynn
Wind turbine noise at low frequencies less than 300Hz is not only annoying to humans but has been proven to cause serious health issues. Additionally, animals are severely affected by wind turbines because a small increase in ambient noise (as is produced by wind turbines) significantly reduces their listening ability. In an attempt to better understand and characterize the aerodynamic noise of wind turbine blades, experimental testing was completed on PowerWorks 100kW and GudCraft WG700 blade specimens in the University of California, Davis Transportation Noise Control Center's anechoic chamber. Experimental testing and data analysis proved approximately 4.0dB to 6.0dB was produced due to the blades' geometric design for both blade specimens at low frequencies. This noise was maximized at the blades' leading edge along the central portion of the blades' radius. Theoretical prediction models have been used to determine that, for typical wind speeds and low frequencies, noise generated due to the tip passing frequency is clearly predominant.
Aerodynamic ground effect in fruitfly sized insect takeoff
Kolomenskiy, Dmitry; Engels, Thomas; Liu, Hao; Schneider, Kai; Nave, Jean-Christophe
2015-01-01
Flapping-wing takeoff is studied using numerical modelling, considering the voluntary takeoff of a fruitfly as reference. The parameters of the model are then varied to explore the possible effects of interaction between the flapping-wing model and the ground plane. The numerical method is based on a three-dimensional Navier-Stokes solver and a simple flight dynamics solver that accounts for the body weight, inertia, and the leg thrust. Forces, power and displacements are compared for takeoffs with and without ground effect. Natural voluntary takeoff of a fruitfly, modified takeoffs and hovering are analyzed. The results show that the ground effect during the natural voluntary takeoff is negligible. In the modified takeoffs, the ground effect does not produce any significant increase of the vertical force neither. Moreover, the vertical force even drops in most of the cases considered. There is a consistent increase of the horizontal force, and a decrease of the aerodynamic power, if the rate of climb is suff...
High-temperature gas effects on aerodynamic characteristics of waverider
Institute of Scientific and Technical Information of China (English)
Liu Jun; Li Kai; Liu Weiqiang
2015-01-01
This paper focuses on the analysis of high-temperature effect on a conical waverider and it is a typical configuration of near space vehicles. Two different gas models are used in the numerical simulations, namely the thermochemical non-equilibrium and perfect gas models. The non-equilibrium flow simulations are conducted with the usage of the parallel non-equilibrium pro-gram developed by the authors while the perfect gas flow simulations are carried out with the com-mercial software Fluent. The non-equilibrium code is validated with experimental results and grid sensitivity analysis is performed as well. Then, numerical simulations of the flow around the conical waverider with the two gas models are conducted. In the results, differences in the flow structures as well as aerodynamic performances of the conical waverider are compared. It is found that the thermochemical non-equilibrium effect is significant mainly near the windward boundary layer at the tail of the waverider, and the non-equilibrium influence makes the pressure center move forward to about 0.57%of the whole craft’s length at the altitude of 60 km.
Study of aerodynamical and mechanical behaviours of Savonius rotor
Energy Technology Data Exchange (ETDEWEB)
Aouachria, Z. [Hadj Lakhdar Univ., Batna (Algeria). Applied Energetic Physic Laboratory
2007-07-01
Although the efficiency of a Savonius rotor is not as high conventional propeller-type and Darrieus wind turbines, it has the advantage of simple construction; acceptance of wind from various directions, thereby eliminating the need for reorientation; high starting torque; and, relatively low operating speed. These advantages outweigh its low efficiency and make it an ideal economic source to meet small-scale power requirements. The instantaneous pressure field on the blades surface was determined in order to analyze the flow around a Savonius rotor. A two dimensional analysis was used to determine the aerodynamic strengths, which led to underline the Magnus effect and to vibrations on the rotor. An anti-vibratory system was also proposed to stabilize or avoid these vibrations. The drag and lift coefficients were found to be in good agreement with results reported in literature. This study identified an inversion lift effect on a Savonius rotor, which closely resembled the Reynolds number, particularly in the peripheral speed coefficient values. It was shown that the machine does not move in accordance with the Magnus effect. 22 refs., 1 tab., 9 figs.
Control of maglev vehicles with aerodynamic and guideway disturbances
Flueckiger, Karl; Mark, Steve; Caswell, Ruth; Mccallum, Duncan
1994-01-01
A modeling, analysis, and control design methodology is presented for maglev vehicle ride quality performance improvement as measured by the Pepler Index. Ride quality enhancement is considered through active control of secondary suspension elements and active aerodynamic surfaces mounted on the train. To analyze and quantify the benefits of active control, the authors have developed a five degree-of-freedom lumped parameter model suitable for describing a large class of maglev vehicles, including both channel and box-beam guideway configurations. Elements of this modeling capability have been recently employed in studies sponsored by the U.S. Department of Transportation (DOT). A perturbation analysis about an operating point, defined by vehicle and average crosswind velocities, yields a suitable linearized state space model for multivariable control system analysis and synthesis. Neglecting passenger compartment noise, the ride quality as quantified by the Pepler Index is readily computed from the system states. A statistical analysis is performed by modeling the crosswind disturbances and guideway variations as filtered white noise, whereby the Pepler Index is established in closed form through the solution to a matrix Lyapunov equation. Data is presented which indicates the anticipated ride quality achieved through various closed-loop control arrangements.
Modeling, Control, and Estimation of Flexible, Aerodynamic Structures
Ray, Cody W.
Engineers have long been inspired by nature’s flyers. Such animals navigate complex environments gracefully and efficiently by using a variety of evolutionary adaptations for high-performance flight. Biologists have discovered a variety of sensory adaptations that provide flow state feedback and allow flying animals to feel their way through flight. A specialized skeletal wing structure and plethora of robust, adaptable sensory systems together allow nature’s flyers to adapt to myriad flight conditions and regimes. In this work, motivated by biology and the successes of bio-inspired, engineered aerial vehicles, linear quadratic control of a flexible, morphing wing design is investigated, helping to pave the way for truly autonomous, mission-adaptive craft. The proposed control algorithm is demonstrated to morph a wing into desired positions. Furthermore, motivated specifically by the sensory adaptations organisms possess, this work transitions to an investigation of aircraft wing load identification using structural response as measured by distributed sensors. A novel, recursive estimation algorithm is utilized to recursively solve the inverse problem of load identification, providing both wing structural and aerodynamic states for use in a feedback control, mission-adaptive framework. The recursive load identification algorithm is demonstrated to provide accurate load estimate in both simulation and experiment.
Aerodynamic analysis of Audi A4 Sedan using CFD
Birwa, S. K.; Rathi, N.; Gupta, R.
2013-04-01
This paper presents the aerodynamic influence of velocity and ground clearance for Audi A4 Sedan. The topology of the test vehicle was modeled using CATIA P3 V5 R17. ANSYS FLUENT 12 was the CFD solver employed in this study. The distribution of pressure and velocity was obtained. The velocities were 30, 40, 50 and 60 m/s and ground clearances were 76.2 mm,101.6 mm,127 mm and 152.4 mm. The simulation results were compared with the available resources. It was found that the drag coefficient decreases with the velocity increasing from 30 to 60 m/s and increases with the ground clearance from 101.6 mm to 152.4 mm. Further decrease in ground clearance showed no effect on the value of coefficient of drag. The lift coefficient was found to decrease firstly with ground clearance from 152.4 mm to 101.6 mm, and then increase from 101.6 mm to 76.2 mm. Both the lift coefficient and drag coefficient was found to be minimum for the ground clearance of 101.6 mm as designed by the company.
Parametric Deformation of Discrete Geometry for Aerodynamic Shape Design
Anderson, George R.; Aftosmis, Michael J.; Nemec, Marian
2012-01-01
We present a versatile discrete geometry manipulation platform for aerospace vehicle shape optimization. The platform is based on the geometry kernel of an open-source modeling tool called Blender and offers access to four parametric deformation techniques: lattice, cage-based, skeletal, and direct manipulation. Custom deformation methods are implemented as plugins, and the kernel is controlled through a scripting interface. Surface sensitivities are provided to support gradient-based optimization. The platform architecture allows the use of geometry pipelines, where multiple modelers are used in sequence, enabling manipulation difficult or impossible to achieve with a constructive modeler or deformer alone. We implement an intuitive custom deformation method in which a set of surface points serve as the design variables and user-specified constraints are intrinsically satisfied. We test our geometry platform on several design examples using an aerodynamic design framework based on Cartesian grids. We examine inverse airfoil design and shape matching and perform lift-constrained drag minimization on an airfoil with thickness constraints. A transport wing-fuselage integration problem demonstrates the approach in 3D. In a final example, our platform is pipelined with a constructive modeler to parabolically sweep a wingtip while applying a 1-G loading deformation across the wingspan. This work is an important first step towards the larger goal of leveraging the investment of the graphics industry to improve the state-of-the-art in aerospace geometry tools.
Bridge aerodynamics and aeroelasticity: A comparison of modeling schemes
Wu, Teng; Kareem, Ahsan
2013-11-01
Accurate modeling of wind-induced loads on bridge decks is critical to ensure the functionality and survivability of long-span bridges. Over the last few decades, several schemes have emerged to model bridge behavior under winds from an aerodynamic/aeroelastic perspective. A majority of these schemes rely on the quasi-steady (QS) theory. This paper systematically compares and assesses the efficacy of five analytical models available in the literature with a new model presented herein. These models include: QS theory-based model, corrected QS theory-based model, linearized QS theory-based model, semi-empirical linear model, hybrid model, and the proposed modified hybrid model. The ability of these models to capture fluid memory and nonlinear effects either individually or collectively is examined. In addition, their ability to include the effects of turbulence in the approach flow on the bridge behavior is assessed. All models are compared in a consistent manner by utilizing the time domain approach. The underlying role of each model in capturing the physics of bridge behavior under winds is highlighted and the influence of incoming turbulence and its interaction with the bridge deck is examined. A discussion is included that focuses on a number of critical parameters pivotal to the effectiveness of corresponding models.
Unsteady aerodynamic modeling based on POD-observer method
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
A new hybrid approach to constructing reduced-order models(ROM)of unsteady aerodynamics applicable to aeroelastic analysis is presented by using proper orthogonal decomposition(POD)in combination with observer techniques.Fluid modes are generated through POD by sampling observations of solutions derived from the full-order model.The response in the POD training is projected onto the fluid modes to determine the time history of the modal amplitudes.The resulting data are used to extract the Markov parameters of the low-dimensional model for modal amplitudes using a related deadbeat observer.The state-space realization is synthesized from the system’s Markov parameters that are processed with the eigensystem realization algorithm.The POD-observer method is applied to a two-dimensional airfoil system in subsonic flow field.The results predicted by the ROM are in general agreement with those from the full-order system.The ROM obtained by the hybrid approach captures the essence of a fluid system and produces vast reduction in both degrees of freedom and computational time relative to the full-order model.
Aerodynamic roughness length related to non-aggregated tillage ridges
Directory of Open Access Journals (Sweden)
M. Kardous
2005-11-01
Full Text Available Wind erosion in agricultural soils is dependent, in part, on the aerodynamic roughness length (z_{0} produced by tillage ridges. Although previous studies have related z_{0} to ridge characteristics (ridge height (RH and spacing (RS, these relationships have not been tested for tillage ridges observed in the North African agricultural fields. In these regions, due to climate and soil conditions, small plowing tools are largely used. Most of these tools produce non-aggregated and closely-spaced small ridges. Thus, experiments were conducted in a 7-m long wind tunnel to measure z_{0} for 11 ridge types covering the range of geometric characteristics frequently observed in south Tunisia. Experimental results suggest that RH^{2}/RS is the first order parameter controlling z_{0}. A strong relationship between z_{0} and RH^{2}/RS is proposed for a wide range of ridge characteristics.
Measurements of the aerodynamic characteristics of the turbo-jav
Yamamoto, Kenta; Nakajima, Tomoya; Itano, Tomoaki; Sugihara-Seki, Masako
2014-11-01
The ``turbo-jav'' which is used for the javelic throw in the junior Olympic games has four tail fins. In order to investigate the aerodynamic characteristics of the turbo-jav with an emphasis on the effect of the fins, we performed wind tunnel tests, throwing experiments and numerical simulations of the flight for intact turbo-javs as well as turbo-javs with their fins cut. The wind tunnel tests showed that the drag and lift coefficients for the intact turbo-javs are larger than the corresponding values for the turbo-javs without fins. As the angle of attack increases from 0, the pitching moments for the intact turbo-javs decrease from 0, whereas the moments for the turbo-javs without fins increase. In accord with this property, the throwing experiments showed that intact turbo-javs fly stably with oscillating angle of attack around 0. The flight distance, the orbit and the variation of angle of attack for the intact turbo-javs launched by a launcher agree closely with the numerical simulation performed based on the wind tunnel tests. A comparison of throwing experiments by students and by the launcher suggested significant effects of the rolling motion of the turbo-jav on its flight characteristics.
Study on transient aerodynamic characteristics of parachute opening process
Institute of Scientific and Technical Information of China (English)
Li Yu; Xiao Ming
2007-01-01
In the research of parachute, canopy inflation process modeling is one of the most complicated tasks. As canopy often experiences the largest deformations and loa-dings during a very short time, it is of great difficulty for theoretical analysis and experimental measurements. In this paper, aerodynamic equations and structural dynamics equa-tions were developed for describing parachute opening process, and an iterative coupling solving strategy incorpo-rating the above equations was proposed for a small-scale, flexible and flat-circular parachute. Then, analyses were car-ried out for canopy geometry, time-dependent pressure diffe-rence between the inside and outside of the canopy, transient vortex around the canopy and the flow field in the radial plane as a sequence in opening process. The mechanism of the canopy shape development was explained from perspective of transient flow fields during the inflation process. Experi-ments of the parachute opening process were conducted in a wind tunnel, in which instantaneous shape of the canopy was measured by high velocity camera and the opening loading was measured by dynamometer balance. The theoretical pre-dictions were found in good agreement with the experimen-tal results, validating the proposed approach. This numerical method can improve the situation of strong dependence of parachute research on wind tunnel tests, and is of signifi-cance to the understanding of the mechanics of parachute inflation process.
On the Deflexion of Anisotropic Structural Composite Aerodynamic Components
Directory of Open Access Journals (Sweden)
J. Whitty
2014-01-01
Full Text Available This paper presents closed form solutions to the classical beam elasticity differential equation in order to effectively model the displacement of standard aerodynamic geometries used throughout a number of industries. The models assume that the components are constructed from in-plane generally anisotropic (though shown to be quasi-isotropic composite materials. Exact solutions for the displacement and strains for elliptical and FX66-S-196 and NACA 63-621 aerofoil approximations thin wall composite material shell structures, with and without a stiffening rib (shear-web, are presented for the first time. Each of the models developed is rigorously validated via numerical (Runge-Kutta solutions of an identical differential equation used to derive the analytical models presented. The resulting calculated displacement and material strain fields are shown to be in excellent agreement with simulations using the ANSYS and CATIA commercial finite element (FE codes as well as experimental data evident in the literature. One major implication of the theoretical treatment is that these solutions can now be used in design codes to limit the required displacement and strains in similar components used in the aerospace and most notably renewable energy sectors.
Heat Rash or Prickly Heat (Miliaria Rubra)
... rash and rashes clinical tools newsletter | contact Share | Heat Rash or Prickly Heat (Miliaria Rubra) Information for adults A A A ... bumps can suddenly occur, as seen here. Overview Heat rash (miliaria rubra), also known as prickly heat, ...
Energy Technology Data Exchange (ETDEWEB)
Pan, Yong-Le; Cobler, Patrick J.; Rhodes, Scott A.; Halverson, Justin; Chang, Richard K.
2005-08-22
An aerosol deflection technique based on the single-shot UV-laser-induced fluorescence spectrum from a flowing particle is presented as a possible front-end bio-aerosol/hazardous-aerosol sensor/identifier. Cued by the fluorescence spectra, individual flowing bio-aerosol particles (1-10 {micro}m in diameter) have been successfully deflected from a stream of ambient aerosols. The electronics needed to compare the fluorescence spectrum of a particular particle with that of a pre-determined fluorescence spectrum are presented in some detail. The deflected particles, with and without going through a funnel for pulse aerodynamic localization (PAL), were collected onto a substrate for further analyses. To demonstrate how hazardous materials can be deflected, TbCl{sub 3} {center_dot} 6H{sub 2}O (a simulant material for some chemical forms of Uranium Oxide) aerosol particles (2 {micro}m in diameter) mixed with Arizona road dust was separated and deflected with our system.
Menicovich, David
material and energy consumption profiles of tall building. To date, the increasing use of light-weight and high-strength materials in tall buildings, with greater flexibility and reduced damping, has increased susceptibility to dynamic wind load effects that limit the gains afforded by incorporating these new materials. Wind, particularly fluctuating wind and its interaction with buildings induces two main responses; alongwind - in the direction of the flow and crosswind - perpendicular to the flow. The main risk associated with this vulnerability is resonant oscillations induced by von-Karman-like vortex shedding at or near the natural frequency of the structure caused by flow separation. Dynamic wind loading effects often increase with a power of wind speed greater than 3, thus increasingly, tall buildings pay a significant price in material to increase the natural frequency and/or the damping to overcome this response. In particular, crosswind response often governs serviceability (human habitability) design criteria of slender buildings. Currently, reducing crosswind response relies on a Solid-based Aerodynamic Modification (SAM), either by changing structural or geometric characteristics such as the tower shape or through the addition of damping systems. While this approach has merit it has two major drawbacks: firstly, the loss of valuable rentable areas and high construction costs due to increased structural requirements for mass and stiffness, further contributing towards the high consumption of non-renewable resources by the commercial building sector. For example, in order to insure human comfort within an acceptable range of crosswind response induced accelerations at the top of a building, an aerodynamically efficient plan shape comes at the expense of floor area. To compensate for the loss of valuable area compensatory stories are required, resulting in an increase in wind loads and construction costs. Secondly, a limited, if at all, ability to adaptively
Maldonado, Victor Hugo
Wind turbines operate within the atmospheric boundary layer (ABL) which gives rise to turbulence among other flow phenomena. There are several factors that contribute to turbulent flow: The operation of wind turbines in two layers of the atmosphere, the surface layer and the mixed layer. These layers often have unstable wind conditions due to the daily heating and cooling of the atmosphere which creates turbulent thermals. In addition, wind turbines often operate in the wake of upstream turbines such as in wind farms; where turbulence generated by the rotor can be compounded if the turbines are not sited properly. Although turbulent flow conditions are known to affect performance, i.e. power output and lifespan of the turbine, the flow mechanisms by which atmospheric turbulence and other external conditions (such as blade debris contamination) adversely impact wind turbines are not known in enough detail to address these issues. The main objectives of the current investigation are thus two-fold: (i) to understand the interaction of the turbulent integral length scales and surface roughness on the blade and its effect on aerodynamic performance, and (ii) to develop and apply flow control (both passive and active) techniques to alleviate some of the adverse fluid dynamics phenomena caused by the atmosphere (i.e. blade contamination) and restore some of the aerodynamic performance loss. In order to satisfy the objectives of the investigation, a 2-D blade model based on the S809 airfoil for horizontal axis wind turbine (HAWT) applications was manufactured and tested at the Johns Hopkins University Corrsin Stanley Wind Tunnel facility. Additional levels of free stream turbulence with an intensity of 6.14% and integral length scale of about 0.321 m was introduced into the flow via an active grid. The free stream velocity was 10 m/s resulting in a Reynolds number based on blade chord of Rec ≃ 2.08x105. Debris contamination on the blade was modeled as surface roughness
Gelzer, Christian
2011-01-01
In 1973 engineers at Dryden began investigating ways to reduce aerodynamic drag on land vehicles. They began with a delivery van whose shape they changed dramatically, finally reducing its aerodynamic drag by more than 5 percent. They then turned their attention to tracator-trailers, modifying a cab-over and reducing its aerodynamic drag by nearly 25 percent. Further research identified additional areas worth attention, but in the intervening decades few of those changes have appeared.
International Nuclear Information System (INIS)
This investigation examines, from the aerodynamic viewpoint, the necessary conditions required to lift relatively large, heavy objects from ground level, into a tornado flow field. The specific objects of interest are a Schedule 40,12'' diameter steel pipe and a 4,000 pound family sedan-type automobile. Analyses consider, in addition to the aerodynamic characteristics of the objects of concern, the surface boundary layer at or very near the tornado funnel, aerodynamic ground effects and possible injection modes
International Nuclear Information System (INIS)
A heat exchanger having primary and secondary conduits in heat-exchanging relationship is described comprising: at least one serpentine tube having parallel sections connected by reverse bends, the serpentine tube constituting one of the conduits; a group of open-ended tubes disposed adjacent to the parallel sections, the open-ended tubes constituting the other of the conduits, and forming a continuous mass of contacting tubes extending between and surrounding the serpentine tube sections; and means securing the mass of tubes together to form a predetermined cross-section of the entirety of the mass of open-ended tubes and tube sections
Holman, J P
2010-01-01
As one of the most popular heat transfer texts, Jack Holman's "Heat Transfer" is noted for its clarity, accessible approach, and inclusion of many examples and problem sets. The new tenth edition retains the straight-forward, to-the-point writing style while covering both analytical and empirical approaches to the subject. Throughout the book, emphasis is placed on physical understanding while, at the same time, relying on meaningful experimental data in those situations that do not permit a simple analytical solution. New examples and templates provide students with updated resources for computer-numerical solutions.
National Aeronautics and Space Administration — ZONA proposes a phase II effort to fully develop a comprehensive methodology for aeroelastic predictions of the nonlinear aerodynamic/aerothermodynamic - structure...
Young, L. A.; Lillie, D.; McCluer, M.; Yamauchi, G. K.; Derby, M. R.
2001-01-01
A recent experimental investigation into tiltrotor aerodynamics and acoustics has resulted in the acquisition of a set of data related to tiltrotor airframe aerodynamics and rotor and wing interactional aerodynamics. This work was conducted in the National Full-scale Aerodynamics Complex's (NFAC) 40-by-80 Foot Wind Tunnel, at NASA Ames Research Center, on the Full-Span Tilt Rotor Aeroacoustic Model (TRAM). The full-span TRAM wind tunnel test stand is nominally based on a quarter-scale representation of the V-22 aircraft. The data acquired will enable the refinement of analytical tools for the prediction of tiltrotor aeromechanics and aeroacoustics.
Aerodynamics of a Gulfstream G550 Nose Landing Gear Model
Neuhart, Dan H.; Khorrami, Mehdi R.; Choudhari, Meelan M.
2009-01-01
In this paper we discuss detailed steady and unsteady aerodynamic measurements of a Gulfstream G550 nose landing gear model. The quarter-scale, high-fidelity model includes part of the lower fuselage and the gear cavity. The full model configuration allowed for removal of various gear components (e.g. light cluster, steering mechanism, hydraulic lines, etc.) in order to document their effects on the local flow field. The measurements were conducted at a Reynolds number of 7.3 x 10(exp 4) based on the shock strut (piston) diameter and a freestream Mach number of 0.166. Additional data were also collected at lower Mach numbers of 0.12 and 0.145 and correspondingly lower Reynolds numbers. The boundary layer on the piston was tripped to enable turbulent flow separation, so as to better mimic the conditions encountered during flight. Steady surface pressures were gathered from an extensive number of static ports on the wheels, door, fuselage, and within the gear cavity. To better understand the resultant flow interactions between gear components, surface pressure fluctuations were collected via sixteen dynamic pressure sensors strategically placed on various subcomponents of the gear. Fifteen of the transducers were flush mounted on the gear surface at fixed locations, while the remaining one was a mobile transducer that could be placed at numerous varying locations. The measured surface pressure spectra are mainly broadband in nature, lacking any local peaks associated with coherent vortex shedding. This finding is in agreement with off-surface flow measurements using PIV that revealed the flow field to be a collection of separated shear layers without any dominant vortex shedding processes.
Wing motion measurement and aerodynamics of hovering true hoverflies.
Mou, Xiao Lei; Liu, Yan Peng; Sun, Mao
2011-09-01
Most hovering insects flap their wings in a horizontal plane (body having a large angle from the horizontal), called `normal hovering'. But some of the best hoverers, e.g. true hoverflies, hover with an inclined stroke plane (body being approximately horizontal). In the present paper, wing and body kinematics of four freely hovering true hoverflies were measured using three-dimensional high-speed video. The measured wing kinematics was used in a Navier-Stokes solver to compute the aerodynamic forces of the insects. The stroke amplitude of the hoverflies was relatively small, ranging from 65 to 85 deg, compared with that of normal hovering. The angle of attack in the downstroke (∼50 deg) was much larger that in the upstroke (∼20 deg), unlike normal-hovering insects, whose downstroke and upstroke angles of attack are not very different. The major part of the weight-supporting force (approximately 86%) was produced in the downstroke and it was contributed by both the lift and the drag of the wing, unlike the normal-hovering case in which the weight-supporting force is approximately equally contributed by the two half-strokes and the lift principle is mainly used to produce the force. The mass-specific power was 38.59-46.3 and 27.5-35.4 W kg(-1) in the cases of 0 and 100% elastic energy storage, respectively. Comparisons with previously published results of a normal-hovering true hoverfly and with results obtained by artificially making the insects' stroke planes horizontal show that for the true hoverflies, the power requirement for inclined stroke-plane hover is only a little (<10%) larger than that of normal hovering.
Fan Noise Source Diagnostic Test: Rotor Alone Aerodynamic Performance Results
Hughes, Christopher E.; Jeracki, Robert J.; Woodward, Richard P.; Miller, Christopher J.
2005-01-01
The aerodynamic performance of an isolated fan or rotor alone model was measured in the NASA Glenn Research Center 9- by 15- Foot Low Speed Wind Tunnel as part of the Fan Broadband Source Diagnostic Test conducted at NASA Glenn. The Source Diagnostic Test was conducted to identify the noise sources within a wind tunnel scale model of a turbofan engine and quantify their contribution to the overall system noise level. The fan was part of a 1/5th scale model representation of the bypass stage of a current technology turbofan engine. For the rotor alone testing, the fan and nacelle, including the inlet, external cowl, and fixed area fan exit nozzle, were modeled in the test hardware; the internal outlet guide vanes located behind the fan were removed. Without the outlet guide vanes, the velocity at the nozzle exit changes significantly, thereby affecting the fan performance. As part of the investigation, variations in the fan nozzle area were tested in order to match as closely as possible the rotor alone performance with the fan performance obtained with the outlet guide vanes installed. The fan operating performance was determined using fixed pressure/temperature combination rakes and the corrected weight flow. The performance results indicate that a suitable nozzle exit was achieved to be able to closely match the rotor alone and fan/outlet guide vane configuration performance on the sea level operating line. A small shift in the slope of the sea level operating line was measured, which resulted in a slightly higher rotor alone fan pressure ratio at take-off conditions, matched fan performance at cutback conditions, and a slightly lower rotor alone fan pressure ratio at approach conditions. However, the small differences in fan performance at all fan conditions were considered too small to affect the fan acoustic performance.
Variational Methods in Sensitivity Analysis and Optimization for Aerodynamic Applications
Ibrahim, A. H.; Hou, G. J.-W.; Tiwari, S. N. (Principal Investigator)
1996-01-01
Variational methods (VM) sensitivity analysis, which is the continuous alternative to the discrete sensitivity analysis, is employed to derive the costate (adjoint) equations, the transversality conditions, and the functional sensitivity derivatives. In the derivation of the sensitivity equations, the variational methods use the generalized calculus of variations, in which the variable boundary is considered as the design function. The converged solution of the state equations together with the converged solution of the costate equations are integrated along the domain boundary to uniquely determine the functional sensitivity derivatives with respect to the design function. The determination of the sensitivity derivatives of the performance index or functional entails the coupled solutions of the state and costate equations. As the stable and converged numerical solution of the costate equations with their boundary conditions are a priori unknown, numerical stability analysis is performed on both the state and costate equations. Thereafter, based on the amplification factors obtained by solving the generalized eigenvalue equations, the stability behavior of the costate equations is discussed and compared with the state (Euler) equations. The stability analysis of the costate equations suggests that the converged and stable solution of the costate equation is possible only if the computational domain of the costate equations is transformed to take into account the reverse flow nature of the costate equations. The application of the variational methods to aerodynamic shape optimization problems is demonstrated for internal flow problems at supersonic Mach number range. The study shows, that while maintaining the accuracy of the functional sensitivity derivatives within the reasonable range for engineering prediction purposes, the variational methods show a substantial gain in computational efficiency, i.e., computer time and memory, when compared with the finite
Unsteady Thick Airfoil Aerodynamics: Experiments, Computation, and Theory
Strangfeld, C.; Rumsey, C. L.; Mueller-Vahl, H.; Greenblatt, D.; Nayeri, C. N.; Paschereit, C. O.
2015-01-01
An experimental, computational and theoretical investigation was carried out to study the aerodynamic loads acting on a relatively thick NACA 0018 airfoil when subjected to pitching and surging, individually and synchronously. Both pre-stall and post-stall angles of attack were considered. Experiments were carried out in a dedicated unsteady wind tunnel, with large surge amplitudes, and airfoil loads were estimated by means of unsteady surface mounted pressure measurements. Theoretical predictions were based on Theodorsen's and Isaacs' results as well as on the relatively recent generalizations of van der Wall. Both two- and three-dimensional computations were performed on structured grids employing unsteady Reynolds-averaged Navier-Stokes (URANS). For pure surging at pre-stall angles of attack, the correspondence between experiments and theory was satisfactory; this served as a validation of Isaacs theory. Discrepancies were traced to dynamic trailing-edge separation, even at low angles of attack. Excellent correspondence was found between experiments and theory for airfoil pitching as well as combined pitching and surging; the latter appears to be the first clear validation of van der Wall's theoretical results. Although qualitatively similar to experiment at low angles of attack, two-dimensional URANS computations yielded notable errors in the unsteady load effects of pitching, surging and their synchronous combination. The main reason is believed to be that the URANS equations do not resolve wake vorticity (explicitly modeled in the theory) or the resulting rolled-up un- steady flow structures because high values of eddy viscosity tend to \\smear" the wake. At post-stall angles, three-dimensional computations illustrated the importance of modeling the tunnel side walls.
Diving-flight aerodynamics of a peregrine falcon (Falco peregrinus.
Directory of Open Access Journals (Sweden)
Benjamin Ponitz
Full Text Available This study investigates the aerodynamics of the falcon Falco peregrinus while diving. During a dive peregrines can reach velocities of more than 320 km h⁻¹. Unfortunately, in freely roaming falcons, these high velocities prohibit a precise determination of flight parameters such as velocity and acceleration as well as body shape and wing contour. Therefore, individual F. peregrinus were trained to dive in front of a vertical dam with a height of 60 m. The presence of a well-defined background allowed us to reconstruct the flight path and the body shape of the falcon during certain flight phases. Flight trajectories were obtained with a stereo high-speed camera system. In addition, body images of the falcon were taken from two perspectives with a high-resolution digital camera. The dam allowed us to match the high-resolution images obtained from the digital camera with the corresponding images taken with the high-speed cameras. Using these data we built a life-size model of F. peregrinus and used it to measure the drag and lift forces in a wind-tunnel. We compared these forces acting on the model with the data obtained from the 3-D flight path trajectory of the diving F. peregrinus. Visualizations of the flow in the wind-tunnel uncovered details of the flow structure around the falcon's body, which suggests local regions with separation of flow. High-resolution pictures of the diving peregrine indicate that feathers pop-up in the equivalent regions, where flow separation in the model falcon occurred.
Integrated Computational System for Aerodynamic Steering and Visualization
Hesselink, Lambertus
1999-01-01
In February of 1994, an effort from the Fluid Dynamics and Information Sciences Divisions at NASA Ames Research Center with McDonnel Douglas Aerospace Company and Stanford University was initiated to develop, demonstrate, validate and disseminate automated software for numerical aerodynamic simulation. The goal of the initiative was to develop a tri-discipline approach encompassing CFD, Intelligent Systems, and Automated Flow Feature Recognition to improve the utility of CFD in the design cycle. This approach would then be represented through an intelligent computational system which could accept an engineer's definition of a problem and construct an optimal and reliable CFD solution. Stanford University's role focused on developing technologies that advance visualization capabilities for analysis of CFD data, extract specific flow features useful for the design process, and compare CFD data with experimental data. During the years 1995-1997, Stanford University focused on developing techniques in the area of tensor visualization and flow feature extraction. Software libraries were created enabling feature extraction and exploration of tensor fields. As a proof of concept, a prototype system called the Integrated Computational System (ICS) was developed to demonstrate CFD design cycle. The current research effort focuses on finding a quantitative comparison of general vector fields based on topological features. Since the method relies on topological information, grid matching and vector alignment is not needed in the comparison. This is often a problem with many data comparison techniques. In addition, since only topology based information is stored and compared for each field, there is a significant compression of information that enables large databases to be quickly searched. This report will (1) briefly review the technologies developed during 1995-1997 (2) describe current technologies in the area of comparison techniques, (4) describe the theory of our new
Aerodynamic characteristics and respiratory deposition of fungal fragments
Cho, Seung-Hyun; Seo, Sung-Chul; Schmechel, Detlef; Grinshpun, Sergey A.; Reponen, Tiina
The purpose of this study was to investigate the aerodynamic characteristics of fungal fragments and to estimate their respiratory deposition. Fragments and spores of three different fungal species ( Aspergillus versicolor, Penicillium melinii, and Stachybotrys chartarum) were aerosolized by the fungal spore source strength tester (FSSST). An electrical low-pressure impactor (ELPI) measured the size distribution in real-time and collected the aerosolized fungal particles simultaneously onto 12 impactor stages in the size range of 0.3-10 μm utilizing water-soluble ZEF-X10 coating of the impaction stages to prevent spore bounce. For S. chartarum, the average concentration of released fungal fragments was 380 particles cm -3, which was about 514 times higher than that of spores. A. versicolor was found to release comparable amount of spores and fragments. Microscopic analysis confirmed that S. chartarum and A. versicolor did not show any significant spore bounce, whereas the size distribution of P. melinii fragments was masked by spore bounce. Respiratory deposition was calculated using a computer-based model, LUDEP 2.07, for an adult male and a 3-month-old infant utilizing the database on the concentration and size distribution of S. chartarum and A. versicolor aerosols measured by the ELPI. Total deposition fractions for fragments and spores were 27-46% and 84-95%, respectively, showing slightly higher values in an infant than in an adult. For S. chartarum, fragments demonstrated 230-250 fold higher respiratory deposition than spores, while the number of deposited fragments and spores of A. versicolor were comparable. It was revealed that the deposition ratio (the number of deposited fragments divided by that of deposited spores) in the lower airways for an infant was 4-5 times higher than that for an adult. As fungal fragments have been shown to contain mycotoxins and antigens, further exposure assessment should include the measurement of fungal fragments for
Harrison, B. A.; Richard, M.
1979-01-01
The information necessary for execution of the digital computer program L216 on the CDC 6600 is described. L216 characteristics are based on the doublet lattice method. Arbitrary aerodynamic configurations may be represented with combinations of nonplanar lifting surfaces composed of finite constant pressure panel elements, and axially summetric slender bodies composed of constant pressure line elements. Program input consists of configuration geometry, aerodynamic parameters, and modal data; output includes element geometry, pressure difference distributions, integrated aerodynamic coefficients, stability derivatives, generalized aerodynamic forces, and aerodynamic influence coefficient matrices. Optionally, modal data may be input on magnetic field (tape or disk), and certain geometric and aerodynamic output may be saved for subsequent use.
Full Text Available ... for signs of heat stroke or exhaustion. Heat Stroke and Exhaustion Symptoms of early heat exhaustion symptoms ... heavy sweating; nausea; and giddiness. Symptoms of heat stroke (late stage of heat illness) include flushed, hot, ...
Su, H.; Yang, Y.; Liu, S.
2015-12-01
Remotely-sensed land surface temperature (LST) is a key variable in energy balance and is widely used for estimating regional heat flux. However, the inequality between LST and aerodynamic surface temperature (Taero) poses a great challenge for regional heat flux estimation in one -source energy balance models. In this study, a one-source model for land (OSML) was proposed to estimate regional surface heat flux without a need for an empirical extra resistance. The proposed OSML employs both a conceptual VFC/LST trapezoid model and the electrical analogue formula of sensible heat flux (H) to estimate the radiometric-convective resistance (rae) by using a quartic equation. To evaluate the performance of OSML, the model was applied to the Soil Moisture-Atmosphere Coupling Experiment (SMACEX), using a remotely-sensed data set at a regional scale. Validated against tower observations, the root mean square deviation (RMSD) of H and latent heat flux (LE) from OSML was 47 W/m2 and 51 W/m2, which is comparable to other published studies. OSML and SEBS (Surface Energy Balance System) compared under the same available energy indicated that LE estimated by OSML is comparable to that derived from the SEBS model. In conducting further inter-comparisons of rae, the aerodynamic resistance derived from SEBS (ra_SEBS), and aerodynamic resistance (ra) derived from Brutsaert et al. (2005) in corn and soybean fields, we found that rae and ra_SEBS are comparable. Most importantly, our study indicates that the OSML method is applicable without having to acquire wind speed or to specify aerodynamic surface characteristics and that it is applicable to heterogeneous areas.
Directory of Open Access Journals (Sweden)
Hadar Ben-Gida
Full Text Available Wing flapping is one of the most widespread propulsion methods found in nature; however, the current understanding of the aerodynamics in bird wakes is incomplete. The role of the unsteady motion in the flow and its contribution to the aerodynamics is still an open question. In the current study, the wake of a freely flying European starling has been investigated using long-duration high-speed Particle Image Velocimetry (PIV in the near wake. Kinematic analysis of the wings and body of the bird has been performed using additional high-speed cameras that recorded the bird movement simultaneously with the PIV measurements. The wake evolution of four complete wingbeats has been characterized through reconstruction of the time-resolved data, and the aerodynamics in the wake have been analyzed in terms of the streamwise forces acting on the bird. The profile drag from classical aerodynamics was found to be positive during most of the wingbeat cycle, yet kinematic images show that the bird does not decelerate. It is shown that unsteady aerodynamics are necessary to satisfy the drag/thrust balance by approximating the unsteady drag term. These findings may shed light on the flight efficiency of birds by providing a partial answer to how they minimize drag during flapping flight.
Institute of Scientific and Technical Information of China (English)
XING Lida; WU Jianghao; LU Yi; L(U) Junchang; JI Qiang
2009-01-01
The Nyctosaurus specimen KJ1 was reconstructed under the hypothesis that there is a membrane attached to the crest;the so-called headsail crest.The aerodynamic forces and moment acting on the headsail crest were analyzed.It was shown that KJ1 might adjust the angle of the headsail crest relative to the air current as one way to generate thrust(one of the aerodynamic forces,used to overcome body drag in forward flight)and that the magnitude of the thrust and moment could vary with the gesture angle and the relative locafion between the aerodynamic center of the headsail crest and body's center of gravity.Three scenarios were tested for comparison:the crest with membrane attachment,the crest without membrane attachment and the absence of a cranial crest.It was shown that the aerodynamic characteristics(increasing.maintaining and decreasing thrusts and moment) would have almost disappear in flight for the crest without membrane attachment and Was non-existent without the cranial crest.It is suggested from aerodynamics evidence alone that Nyctosaurus specimen KJ1 had a membrane attached to the crest and used this reconstructed form for auxiliary flight control.
Aerodynamic Optimization of the Nose Shape of a Train Using the Adjoint Method
Directory of Open Access Journals (Sweden)
Jorge Munoz-Paniagua
2015-01-01
Full Text Available The adjoint method is used in this paper for the aerodynamic optimization of the nose shape of a train. This method has been extensively applied in aircraft or ground vehicle aerodynamic optimization, but is still in progress in train aerodynamics. Here we consider this innovative optimization method and present its application to reduce the aerodynamic drag when the train is subjected to front wind. The objective of this paper is to demonstrate the effectiveness of the method, highlighting the requirements, limitations and capabilities of it. Furthermore, a significant reduction of the aerodynamic drag in a short number of solver calls is aimed as well. The independence of the computational cost with respect to the number of design variables that define the optimal candidate is stressed as the most interesting characteristic of the adjoint method. This behavior permits a more complete modification of the shape of the train nose because the number of design variables is not a constraint anymore. The information obtained from the sensitivity field permits determining the regions of the geometry where a small modification of the nose shape might introduce a larger improvement of the train performance. A good agreement between this information and the successive geometry modifications is observed here.
The roles of aerodynamic and inertial forces on maneuverability in flapping flight
Vejdani, Hamid; Boerma, David; Swartz, Sharon; Breuer, Kenneth
2015-11-01
We investigate the relative contributions of aerodynamic and the whole-body dynamics in generating extreme maneuvers. We developed a 3D dynamical model of a body (trunk) and two rectangular wings using a Lagrangian formulation. The trunk has 6 degrees of freedom and each wing has 4 degrees of actuation (flapping, sweeping, wing pronation/supination and wing extension/flexion) and can be massless (like insect wings) or relatively massive (like bats). To estimate aerodynamic forces, we use a blade element method; drag and lift are calculated using a quasi-steady model. We validated our model using several benchmark tests, including gliding and hovering motion. To understand the roles of aerodynamic and inertial forces, we start the investigation by constraining the wing motion to flapping and wing length extension/flexion motion. This decouples the trunk degrees of freedom and affects only roll motion. For bats' dynamics (massive wings), the model is much more maneuverable than the insect dynamics case, and the effect of inertial forces dominates the behavior of the system. The role of the aerodynamic forces increases when the wings have sweeping and flapping motion, which affects the pitching motion of the body. We also analyzed the effect of all wing motions together on the behavior of the model in the presence and in the absence of aerodynamic forces.
Large eddy simulation on the unsteady aerodynamic response of a road vehicle in transient crosswinds
International Nuclear Information System (INIS)
A large eddy simulation method based on a fully unstructured finite volume method was developed, and the unsteady aerodynamic response of a road vehicle subjected to transient crosswinds was investigated. First, the method was validated for a 1/20-scale wind-tunnel model in a static aerodynamic condition; this showed that the surface pressure distributions as well as the aerodynamic forces and moments were in good agreement with wind-tunnel data. Second, the method was applied to two transient crosswind situations: a sinusoidal perturbation representing the typical length scale of atmospheric turbulence and a stepwise crosswind velocity corresponding to wind gusts. Typical transient responses of the aerodynamic forces and moments such as phase shifting and undershooting or overshooting were observed, and their dependence on the frequency and amplitude of the input perturbation is discussed. Thus, the utility and validity of the large eddy simulation was demonstrated in the context that such transient aerodynamic forces are difficult to measure using a conventional wind tunnel.
Aerodynamic analysis of the aerospaceplane HyPlane in supersonic rarefied flow
Zuppardi, Gennaro; Savino, Raffaele; Russo, Gennaro; Spano'Cuomo, Luca; Petrosino, Eliano
2016-06-01
HyPlane is the Italian aerospaceplane proposal targeting, at the same time, both the space tourism and point-to-point intercontinental hypersonic flights. Unlike other aerospaceplane projects, relying on boosters or mother airplanes that bring the vehicle to high altitude, HyPlane will take off and land horizontally from common runways. According to the current project, HyPlane will fly sub-orbital trajectories under high-supersonic/low-hypersonic continuum flow regimes. It can go beyond the von Karman line at 100 km altitude for a short time, then starting the descending leg of the trajectory. Its aerodynamic behavior up to 70 km have already been studied and the results published in previous works. In the present paper some aspects of the aerodynamic behavior of HyPlane have been analyzed at 80, 90 and 100 km. Computer tests, calculating the aerodynamic parameters, have been carried out by a Direct Simulation Monte Carlo code. The effects of the Knudsen, Mach and Reynolds numbers have been evaluated in clean configuration. The effects of the aerodynamic surfaces on the rolling, pitching and yawing moments, and therefore on the capability to control attitude, have been analyzed at 100 km altitude. The aerodynamic behavior has been compared also with that of another aerospaceplane at 100 km both in clean and flapped configuration.