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Numerical Investigation of Compressor Blades Deformation During Stall Development into Surge

JOURNAL OF PROPULSION AND POWER 2017年第5期33卷 1074-1086页

作者： Halawa, Taher Gadala, Mohamed S. Cairo Univ Fac Engn Mech Power Dept Giza 12613 Egypt Univ British Columbia Dept Mech Engn Vancouver BC V6T 1Z4 Canada Abu Dhabi Univ Abu Dhabi U Arab Emirates

The present paper focuses on the simulations of the flow behavior and the structural analysis for a high-speed compressor at the transition time between stall and surge. Two cases are presented;the first case is for the compressor with its original design unchanged, and the other case is for the compressor controlled with air injection at the vaneless area. The case of the compressor with air injection was studied aerodynamically and discussed in detail in a previously published paper done by the authors of the current presented work. Results showed that the stall effect is relatively higher at the impeller exit near the shroud surface due to the interaction between the main flow and the secondary flow, which causes strong pressure and velocity fluctuations at this area. Results also indicated that the forces and moments for the case of the controlled compressor are lower than those for the uncontrolled compressor during stall and surge. The blades tip surface deflection is maximized at the moment of the maximum pressure in the surge cycle, and the most dangerous region at the deformed blades tip surface is located at the transition area between the axial and radial blade profile. Results also showed that the deformation of the blades at the tip region can be limited by changing the shaft bearing stiffness.

关键词： Centrifugal Compressor Structural Analysis Numerical Modeling computational fluid dynamics simulation Stress Distribution FSI Structural Modeling Rotating Stall Mass Flow Rate Dynamic Pressure

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Assessment and Calibration of the γ-Equation Transition Model at Low Mach

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AIAA JOURNAL 2017年第4期55卷 1126-1139页

作者： Colonia, S. Leble, V. Steijl, R. Barakos, G. Univ Glasgow Sch Engn Glasgow G12 8QQ Lanark Scotland

The numerical simulation of flows over large-scale wind turbine blades without considering the transition from laminar to fully turbulent flow may result in incorrect estimates of the blade loads and performance. Thanks to its relative simplicity and promising results, the local-correlation-based transition modeling concept represents a valid way to include transitional effects into practical computational fluid dynamics simulations. However, the model involves coefficients to be tuned to match the required application. In this paper, the.-equation transition model is assessed and calibrated, for a wide range of Reynolds numbers at low Mach, as needed for wind turbine applications. Different airfoils are used to evaluate the original model and calibrate it, whereas a large-scale wind turbine blade is employed to show that the calibrated model can lead to reliable solution for complex three-dimensional flows. The calibrated model shows promising results for both two-dimensional and three-dimensional flows, even if cross-flow instabilities are neglected.

关键词： Free Stream Velocity computational fluid dynamics simulation Turbine Blades Wind Turbine Airfoil Natural Laminar Flow Free Stream Turbulence XFoil Reynolds Averaged Navier Stokes Laminar to Turbulent Transition Lift Coefficient

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Wind tunnel test and numerical simulation of wind characteristics at a bridge site in mountainous terrain

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ADVANCES IN STRUCTURAL ENGINEERING 2017年第8期20卷 1223-1231页

作者： Li, Yongle Xu, Xinyu Zhang, Mingjin Xu, Youlin Southwest Jiaotong Univ Dept Bridge Engn Chengdu 610031 Sichuan Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong Hong Kong Peoples R China

Wind tunnel test and computational fluid dynamics simulation were conducted to study the wind characteristics at a bridge site in mountainous terrain. The upstream terrains were classified into three types: open terrain, open terrain with a steep slope close to the bridge, and open terrain with a ridge close to the bridge. Results obtained from the two methods were compared, including mean speed profiles in the vertical direction and variations of wind speed and angle of attack along the bridge deck. In addition, turbulence intensities at the bridge site obtained from wind tunnel test were discussed. For mean speed profiles in the vertical direction, two methods are reasonably close for open terrain, while mountain shielding effects are evident for open terrain with a steep slope for both the methods, but the extents of effects appear different. Wind speed and angle of attack along the bridge deck are mainly influenced by the local terrain. Strong downslope wind is generated at the lee slope for the case of wind normal to top of the ridge. The comparative results are expected to provide useful references for the study of wind characteristics in mountainous terrain in the future.

关键词： angle of attack bridge site computational fluid dynamics simulation mean wind speed mountainous terrain turbulence intensity wind characteristics wind tunnel test

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Vibrational Nonequilibrium Quantification for State-Resolved simulation of a Hypersonic Flow

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2017年第3期31卷 660-673页

作者： Burt, Jonathan M. Josyula, Eswar US Air Force Res Lab Ohio Aerosp Inst Wright Patterson AFB OH 45433 USA NASA Glenn Res Ctr Mission Architecture & Anal Branch Cleveland OH 44135 USA

Recent developments in internal energy nonequilibrium modeling for hypersonic gas flow simulations indicate a strong need for improved fidelity. Research efforts have consequently focused on discrete state kinetic relaxation techniques which independently model quantum state populations, although computational requirements for discrete state kinetic relaxation modeling of large-scale flows have to date limited the applicability of this type of model. With an ultimate goal of improving discrete state kinetic relaxation calculation efficiency through the use of locally adaptive model fidelity, in the present work various means of quantifying and predicting vibrational nonequilibrium for a representative hypersonic flow are investigated. A series of nonequilibrium metrics is assessed both for individual states and for the overall vibrational energy distribution, based on quantities including the normalized difference between translational and vibrational temperatures, deviation from equilibrium state populations, time scale ratios, and entropy generation. As a test case, an inviscid Mach 6.5 flow of N-2 over a cylindrical forebody geometry is considered. In observing trends among various metrics, areas of agreement as well as significant discrepancies are found. In a demonstration of local model adaptation, an additional simulation is performed, for which near-equilibrium regions are automatically assigned simplified discrete state kinetic relaxation procedures, and good agreement is observed with baseline simulation results.

关键词： Hypersonic Flows Energy Distribution Entropy Generation Rate Internal Energy Stagnation Streamlines Freestream Mach Number Damköhler Numbers Shock Layers computational fluid dynamics simulation Thermodynamic Equilibrium

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Discrete Vortex Method with Flow Separation Corrections for Flapping-Foil Power Generators

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AIAA JOURNAL 2017年第2期55卷 410-418页

作者： Liu, Zhengliang Lai, Joseph C. S. Young, John Tian, Fang-Bao Univ New South Wales Sch Engn & Informat Technol Canberra ACT 2600 Australia

Energy harvesting using flapping foils has attracted significant attention in the last 10 years. In contrast to conventional turbines, which rely on attached flow for high efficiency, a flapping-foil turbine exploits the separation of fluid flow near the nose of the foil to form a leading-edge vortex, resulting in high instantaneous forces. To reduce the computational cost of simulating a flapping foil undergoing high angles of attack (up to 90deg), a discrete vortex method that incorporates leading-edge flow separation is used in this study. Corrections using semi-empirical functions are introduced to account for the effects of trailing-edge flow separation. Instantaneous lift and power coefficient as well as the mean power coefficient and efficiency from the discrete vortex method with separation corrections are compared against those from a dynamic stall model and computational-fluid-dynamics results obtained by the lattice Boltzmann method. The discrete vortex method provides better agreement with computational-fluid-dynamics simulations compared to the dynamic stall model.

关键词： Flow Separation Vortex Shedding Flapping Frequency Critical Angle of Attack computational fluid dynamics simulation LBM Freestream Velocity Power Coefficient Energy Harvesting fluid Flow

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Impact of Weld Joint on Compressor Blade Performance

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JOURNAL OF PROPULSION AND POWER 2017年第1期33卷 276-284页

作者： Mesbah, M. Geuzaine, P. Arts, T. Simon, J. F. Cenaero Turbomachinery Adv Aerodynam Grp B-6041 Gosselies Belgium Von Karman Inst Fluid Dynam Turbomachinery & Prop Dept B-1640 Rhode St Genese Belgium Techspace Aero B-4041 Milmort Belgium

This contribution focused on the analysis of weld-joint effects resulting from the assembly of the blades and disk for the compressor blades. Experiments at the von Karman Institute and computational fluid dynamics simulations at Cenaero were conducted to study the flowfield in a low-pressure high-speed compressor cascade with two weld-joint configurations. Experiments were performed to measure the total pressure loss coefficient for various inlet flow conditions. Reynolds-averaged Navier-Stokes simulations using the k - L turbulence model were carried out. Comparison between the Reynolds-averaged Navier-Stokes solutions and the experiments were made, and the accuracy of the results was investigated. The impact of the weld-joint height and the upstream boundary layer on the losses was studied. In addition, the effect of the weld-joint heights on the growth of the boundary layer was analyzed and presented.

关键词： Compressor Cascade Boundary Layer Thickness computational fluid dynamics simulation Reynolds Averaged Navier Stokes Flow Conditions Turbulence Models Vortices Freestream Velocity Static Pressure Aspect Ratio

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Aerodynamic Optimization of Microspoiler Actuators for Guided Projectiles

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JOURNAL OF SPACECRAFT AND ROCKETS 2017年第6期54卷 1216-1227页

作者： Leonard, Andrew Rogers, Jonathan Sahu, Jubaraj Georgia Inst Technol Woodruff Sch Mech Engn Atlanta GA 30332 USA US Army Res Lab Weap & Mat Res Directorate Aberdeen Proving Ground MD 21005 USA

Microspoiler actuators have been established as a viable control mechanism for gun-launched guided projectiles. Although the geometric configuration of the microspoilers is known to have a large impact on control authority, these geometrical dependencies have previously not been well characterized. This work seeks to derive an optimal microspoiler configuration that maximizes control authority. Parametric computational fluid dynamics studies are performed in which configuration parameters of the microspoilers are varied and the effects on control forces and moments quantified. Through an iterative approach, an optimal configuration is identified that maximizes the ratio of the control authority to the drag penalty. This optimal configuration exhibits twice the control authority of that used in previous studies. Further computational fluid dynamics simulations are performed to characterize the effects of the spoiler height, Mach number, and angle of attack. In addition, the effect of the spoiler interaction with static fins is quantified to explore the mechanism's applicability to spin-stabilized projectiles. Trajectory simulations using the optimized geometry show that the microspoilers produce favorable control authority for supersonic fin-stabilized rounds. This control authority is shown to be similar to that obtained using canards, with the added benefit that the microspoilers can be easily retracted into the projectile body when not in use.

关键词： Spin Stabilized Projectiles Actuators Aerodynamic Coefficients Angle of Attack Canard computational fluid dynamics simulation Reynolds Averaged Navier Stokes Defense Advanced Research Projects Agencies Muzzle Velocity Airframes

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computational fluid dynamics simulations of a GO2/GH2 Single Element Combustor

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JOURNAL OF PROPULSION AND POWER 2015年第6期31卷 1707-1714页

作者： Zhukov, Victor P. German Aerosp Ctr DLR Inst Space Prop D-74239 Hardthausen Germany

A single-element combustor known as the "Penn State preburner combustor" is modeled numerically using the commercial computational fluid dynamics code ANSYS CFX. The aim of computational fluid dynamics modeling is to simulate the wall heat flux, which has been measured experimentally. The simulated combustion chamber has a single shear coaxial injector and operates with gaseous oxygen and hydrogen in a staged combustion configuration. The turbulent flow in the combustion chamber is modeled using the Favre-averaged Navier-Stokes equations and the shear-stress transport turbulence model. The turbulent non-premixed flame is modeled using an extended eddy dissipation model. The developed turbulent combustion model shows good agreement with the experimental data, good convergence, and a short computational time. A mesh convergence study is performed, and a mesh-independent solution is obtained on a mesh with 1.5 million nodes. The complexity of the model is gradually increased until the model is capable of predicting the wall heat flux. The analysis of numerical results shows a significant effect of boundary conditions on wall heat flux predictions. The comparison of the Reynolds-averaged Navier-Stokes simulations with the experimental data demonstrates the capability of Reynolds-averaged Navier-Stokes simulations to predict wall heat fluxes in a rocket combustion chamber.

关键词： Combustors computational fluid dynamics simulation Heat Flux Chamber Pressure Reynolds Averaged Navier Stokes Combustion Efficiency Ideal Rocket Turbulence Models Coaxial Injector Turbulent Flow

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Numerical investigations of bio-inspired blade designs to reduce broadband noise in aircraft engines and wind turbines 55

Numerical investigations of bio-inspired blade designs to re...

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55th AIAA Aerospace Sciences Meeting

作者： Bodling, Andrew Agrawal, Bharat Raj Sharma, Anupam Clark, Ian Nathan Alexander, W. Devenport, William Department of Aerospace Engineering Iowa State University 1200 Howe Hall AmesIA50011 United States Department of Aerospace Engineering Iowa State University 2341 Howe Hall AmesIA50011 United States Department of Aerospace and Ocean Engineering Virginia Polytechnic Institute and State University BlacksburgVA24061 United States McBryde Hall RM 660E225 Stanger St. BlacksburgVA24061 United States

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

This paper numerically models an airfoil geometry inspired by the downy coat of the barn owl and contrasts its aerodynamic and aeroacoustic performance with the baseline airfoil. Implicit large eddy simulations are performed with the Navier Stokes solver FDL3DI. A baseline NACA 0012 airfoil is compared against the same model with an array of fences at the trailing edge. Both models were simulated at a Reynolds number of 3 × 105, flow mach number of 0.2 and angle of attack of 3 degrees. The fences are shown to reduce the sound spectra in the high frequencies by up to 1.8 dB at the airfoil trailing edge. Spanwise correlations show a reduction in coherence length, especially at low frequencies, with the fences. The simulation results agree with the experiments in that the fence spacing is an important design parameter. © 2017 by Andrew Bodling, Bharat Raj Agrawal, Anupam Sharma, Ian Clark, W. Nathan Alexander, and, William Devenport. Published by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Wind Turbine Gliding Flight NACA 0012 computational fluid dynamics simulation Aerodynamic Performance Reynolds Number Airfoil Geometry Aircraft Engines Navier Stokes Solver Overall Sound Pressure Level

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Aerodynamic breakup and secondary drop formation for a liquid metal column in a shock-induced cross-flow 55

Aerodynamic breakup and secondary drop formation for a liqui...

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55th AIAA Aerospace Sciences Meeting

作者： Chen, Yi DeMauro, Edward P. Wagner, Justin L. Arienti, Marco Guildenbecher, Daniel R. Farias, Paul A. Grasser, Thomas W. Sanderson, Patrick D. Albert, Samuel W. Turpin, Aaron M. Sealy, William Ketchum, Remington S. Sandia National Laboratories Engineering Sciences Center AlbuquerqueNM87185 United States Thermal/Fluid Science and Engineering LivermoreCA94551 United States Iowa State University AmesIA50011 United States Purdue University West LafayetteIN47906 United States North Carolina State University RaleighNC27695 United States University of Arizona TucsonAZ85721 United States

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

The breakup of liquid metals is of relevance to powder formation, thermal spray coatings, liquid metal cooling systems, investigations of accident scenarios, and model validation. In this work, a column of liquid Galinstan, a room-temperature liquid metal alloy, is studied in a shock-induced cross-flow. Backlit experiments are used to characterize breakup morphology and digital in-line holography is used to quantitatively measure the size and speed of secondary droplets. Two-dimensional simulations are also developed in order to help understand the underlying mechanisms that drive breakup behavior. Results show that although breakup morphologies are similar for water and Galinstan at the same Weber number, the breakup distance, secondary droplet size, and secondary droplet shapes differ. Evidence indicates that secondary droplet formation may be related to the Weber number, density ratio, the convective velocity and other effects. © 2017 by André R R Silva, Christian M G Rodrigues, Jorge M M Barata.

关键词： Weber Numbers Thermal Spraying Surface Tension Aerodynamic Instability Convective Flow Lawrence Berkeley National Laboratory Conservation of Mass Adaptive Mesh Refinement Navier Stokes Equations computational fluid dynamics simulation

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