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A small-distributed aerodynamic brake prototype and its effects on the vertical dynamics of high-speed electromagnetic suspension maglevs

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART F-JOURNAL OF RAIL AND RAPID TRANSIT 2022年第9期236卷 1091-1103页

作者： Weng, Jingjing Tian, Chun Ma, Tianhe Wu, Mengling Tongji Univ Inst Rail Transit Shanghai Peoples R China

Aerodynamic braking is a clean and environmentally friendly braking mode, and it does not use mechanical friction as its braking force. In this study, we discuss the development of a small-distributed aerodynamic brake prototype and its structure, working principle, ground test and test results. A computational fluid dynamics (CFD) method is developed to record the aerodynamic forces of the prototype, and the simulation results are validated with the wind tunnel test. On the basis of the CFD simulation, the panel opening and braking processes are modelled to analyse the vertical dynamic characteristics of a high-speed electromagnetic suspension maglev with aerodynamic brakes. In addition, a vehicle, guideway and levitation controller are modelled. Finally, a three-car system dynamic model is used to study the effects of the opening time, initial braking position and feedback gains. The aerodynamic forces of the first car show the most significant changes when the braking panels are opened. The increase in the longitudinal force is 15 461.16 N, and the vertical force varies from a lift force of 35 342.98 N to a downforce of 40 721.35 N. The maximum guideway deflection decreases as the opening time increases. The difference between the deflections recorded at the opening time of 0.064 s and 0.6 s is 1.2 mm. Furthermore, the vertical acceleration decreases as the opening time increases. The condition under which the vehicle brakes when the first car enters the object guideway has the maximum effect on the deflection of the guideway. To ensure levitation stability, influenced by the vertical change of the first car, a high feedback gain for the levitation clearance change is required. However, the levitation stability with aerodynamic brakes has low sensitivity to the feedback gains for the observed velocity and acceleration of the system.

关键词： High-speed maglev aerodynamic brake computational fluid dynamics simulation vehicle guideway dynamic model levitation clearance

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Nonequilibrium Dissociation and Recombination Models for Hypersonic Flows

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AIAA JOURNAL 2022年第5期60卷 2810-2825页

作者： Singh, Narendra Schwartzentruber, Thomas E. Stanford Univ Dept Mech Engn Stanford CA 94305 USA Univ Minnesota Dept Mech Engn Dept Aerosp Engn & Mech Minneapolis MN 55455 USA

A recombination reaction model for high-temperature chemical kinetics is analytically derived from ab initio simulation data. When atoms recombine, the kinetic rate model shows that product molecules favor high vibrational energy states. In this manner, recombination repopulates high vibrational energy states depleted by dissociation, in a high-temperature reacting gas. Coupling of internal energy relaxation, dissociation, and recombination results in depleted or overpopulated (relative to a corresponding Boltzmann distribution) vibrational energy distributions. Through a simple model, we show that non-Boltzmann behavior, in other words, depletion or overpopulation of high-energy states, is not only linked to thermal nonequilibrium but also chemical nonequilibrium. The mathematical derivation also indicates that the conventional approach for modeling recombination rates, where shock-tube dissociation rate measurements are combined with the principle of detailed balance, is incorrect. The complete analytical dissociation/recombination model embeds all relevant kinetic processes, including specific terms for translation/rotation/vibration/chemistry coupling, anharmonic and quasi-bound effects, and non-Boltzmann depletion and overpopulation effects. The model is a multitemperature model that can be used within computational fluid dynamics simulations with no appreciable increase in computational expense. Finally, because the model is analytical, containing separate terms for various physical effects, further model simplification could be performed depending on the flow conditions of interest.

关键词： Hypersonic Flows Energy Distribution Chemical Equilibrium computational fluid dynamics simulation Shock Tube High Temperature Chemical Kinetics Thermal Nonequilibrium Direct simulation Monte Carlo Harmonic Oscillator Quasi Steady States

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A Structural Analysis for the Reconfigurable Ducted Turbine Array Concept

A Structural Analysis for the Reconfigurable Ducted Turbine ...

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AIAA SciTech Forum

作者： Methon, Gregory Erol, Nazim Sharghi, Hesam Shan, Xin Bilgen, Onur Rutgers State Univ Dept Mech & Aerosp Engn Mech & Aerosp Engn Piscataway NJ 08854 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

This paper focuses on structural modeling of a single ducted turbine as a key component of the reconfigurable ducted turbine array concept previously proposed by the authors. The ducted hydrokinetic turbine system consists of sub-assemblies, such as the duct, rotor, hub, nacelle, nacelle connectors, etc. This paper focuses on the two geometrically complex components, namely the duct and the rotor blades. The hydrodynamic loads, generator torque, and other loads in the system require a combination of low- and high-fidelity models to accurately represent stresses, strains, and displacements in the system, and to provide an accurate and computationally-efficient structural model for multi-disciplinary design optimization. For example, the duct thickness must be sufficient enough to withstand hydrodynamic, gravity, connection, and transportation loads. In this paper, the duct and the rotor blades of a single reconfigurable ducted turbine are structurally analyzed by their respective loads. The high-fidelity models (i.e., with the use of the finite element method) is compared and verified using analytical (i.e., low-fidelity) models. These analyses are then used to conduct a preliminary design optimization where the minimum duct wall thickness, minimum blade thickness, and respective material choices are identified.

关键词： Turbine Blades Structural Analysis Power Coefficient Structural Modeling Structural Finite Elements Nacelles Multi Disciplinary Design Optimization American Institute of Aeronautics and Astronautics Acrylonitrile Butadiene Styrene computational fluid dynamics simulation

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Trajectory-Informed Sampling for Efficient Construction of Multi-Fidelity Surrogate Models for Hypersonic Vehicles

Trajectory-Informed Sampling for Efficient Construction of M...

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AIAA SciTech Forum

作者： Needels, Jacob T. Alonso, Juan J. Stanford Univ Dept Aeronaut & Astronaut Stanford CA 94305 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

This paper studies the use of multi-fidelity surrogate modeling for analysis of hypersonic vehicles with a focus on the computation of trajectory sensitivities to inform sampling policy. A multi-fidelity aerodynamic database is generated for a hypersonic glide vehicle and surrogate accuracy is assessed for different numbers of high-fidelity samples. A methodology for computing sensitivities of trajectory quantities of interest to surrogate-modeled aerodynamic parameters is applied to hypersonic glide vehicle dynamics. The necessary adjoint equations are derived to compute sensitivities to aerodynamic parameters, which are then used to inform high-fidelity sampling. Of several strategies assessed, sensitivity-based sampling is found to give the best performance for fixed computational cost. Extensions of this methodology are discussed in the context of future work, including the use of sensitivities to allocate simulations among several disciplines in multidisciplinary design problems.

关键词： Hypersonic Vehicles Uncertainty Quantification Hypersonic Glide Vehicle Computing Technology Aerodynamic Coefficients Aerodynamic Performance computational fluid dynamics simulation Lift to Drag Ratio Gaussian Process Gaussian Process Regression

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Quantitative Comparison of Large Eddy simulations and Optical Diagnostics of Bluff-Body Premixed Flames with High and Low Approach Flow Turbulence

Quantitative Comparison of Large Eddy Simulations and Optica...

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AIAA SciTech Forum

作者： Squeo, Joseph N. Sykes, Joshua P. Comer, Adam L. Fugger, Christopher A. Rankin, Brent A. Innovat Sci Solut Inc Dayton OH 45459 USA Spectral Energies LLC Dayton OH 45433 USA Air Force Res Lab Wright Patterson AFB OH 45433 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

The accuracy of large eddy simulations of bluff-body premixed flames is assessed through detailed comparison to experimental measurements acquired using a variety of modern diagnostics. Non-reacting and reacting flows around a confined equilateral triangle bluffbody are simulated with high and low approach flow turbulence levels similar to experiments. Simulated velocity fields, species distributions and heat release rates are respectively compared with hot wire anemometry measurements and simultaneous 10 kHz rate particle image velocimetry, OH and CH2O planar laser-induced fluorescence and OH* chemiluminescence imaging measurements. Results show good qualitative and quantitative agreement of the recirculation zone and shear layer characteristics between the experiments and simulations on a time-averaged basis with the exception of the high approach flow turbulence recirculation zone length. The simulations capture mean and standard deviations of the flame edge and preheat region, as well as trends in flame brush thickness. As revealed by quantitative comparisons with instantaneous data from state-of-the-art diagnostics, this statistical agreement occurs in spite of the simulation's failure to capture small-scale flame wrinkling observed in the experiment.

关键词： Turbulent Combustion Approaching Flow Bluff Body Free Stream Turbulence computational fluid dynamics simulation Planar Laser Induced Fluorescence Shear Layers Chemiluminescence Particle Image Velocimetry Non Reacting Flow

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Modeling and Analysis of Film Cooling in Oxygen-Kerosene Rocket Thrust Chambers

Modeling and Analysis of Film Cooling in Oxygen-Kerosene Roc...

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AIAA SciTech Forum

作者： Cocirla, Gianluca Grossi, Marco Migliorino, Mario Tindaro Bianchi, Daniele Nasuti, Francesco Sapienza Univ Rome Dept Mech & Aerosp Engn Via Eudossiana 18 I-00184 Rome Italy

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

Modern high performance liquid rocket engines are characterized by elevated hot gas temperatures and combustion chamber pressures leading to high wall heat fluxes, which must be correctly predicted and managed to guarantee safe operation. In these severe operating conditions, active cooling systems such as regenerative cooling might not be enough to counteract such high thermal loads. In such cases, cooling capabilities can be enhanced with the addition of a further cooling strategy, such as film cooling. The prediction of wall heat flux in such thrust chambers is of paramount importance during the design phase both for sizing and safety purposes. Despite the complexity of the phenomenon, computational fluid dynamics simulations represent a valuable solution in the convective wall heat flux prediction with respect to more expensive procedures such as hot-firing tests. In any case, the presence of experimental data is necessary in order to validate and evaluate the predictive capacity of a numerical model. In this framework, this paper aims at investigating different operating conditions of the single injector thrust chamber burning gaseous oxygen and kerosene of the Technical University of Munich (TUM) test case with and without the injection of film cooling in order to validate an in-house Reynolds-averaged Navier-Stokes solver.

关键词： Regenerative Cooling Kerosene Rocket Thrust Chamber Heat Flux Combustion Chambers Reynolds Averaged Navier Stokes Roe Approximate Riemann Solver computational fluid dynamics simulation Liquid Rocket Engine Combustion Products

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Updated Aerodynamic Analysis of Outboard Horizontal Stabilizers

Updated Aerodynamic Analysis of Outboard Horizontal Stabiliz...

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AIAA SciTech Forum

作者： De Alwis, Arjuna Ward, Ryan Hinman, W. Schuyler Univ Calgary Dept Mech & Mfg Engn 2500 Univ Dr Calgary AB T2N1N4 Canada

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

The present study examines the aerodynamics of Outboard Horizontal Stabilizer (OHS) configurations using lifting line theory and computational fluid dynamics. This work builds on past efforts that relied heavily on simplified approaches and an assumed behavior of the OHS concept. Thus, this study aims to utilize a mixture of approaches to quantify and describe the OHS concept and potential performance gains. A modern non-linear lifting-line theory, including a vortex decay model, is used for a fast low-fidelity model. This analysis is subsequently supported through Reynolds Averaged Navier Stokes simulations completed in OpenFOAM((R)). Both the lifting line method and CFD approaches were validated using experimental data obtained from the literature. A specific OHS configuration being developed by the present authors was used as a case study. The new results obtained in this work clearly show a substantial increase in performance for the OHS of 19% increased C-L/C-D when compared to a traditional configuration. In order to examine this further, the lifting line approach was utilized to explore the lift and drag performance of the chosen OHS case study when considering the impact of static stability and trim. The results show that even when considering the required negative lift on the horizontal stabilizer to achieve balance, the OHS version performs substantially better. Additionally, it was shown that the performance of the OHS is significantly improved at a negative static margin where the aircraft is statically unstable, but a positive lift on the tailplane can be achieved.

关键词： Horizontal Stabilizers Aerodynamic Coefficients Aerodynamic Performance computational fluid dynamics simulation Horseshoe Vortex Reynolds Averaged Navier Stokes Aircraft Configurations Lift to Drag Ratio Remotely Piloted Aircraft Turbulence Models

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Non-linear Estimators for Hypersonic Heat Flux Reconstruction

Non-linear Estimators for Hypersonic Heat Flux Reconstructio...

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AIAA SciTech Forum

作者： Nguyen, Nhat M. Ruda, Mathew L. Massa, Luca Virginia Polytech Inst & State Univ Dept Aerosp & Ocean Engn Blacksburg VA 24061 USA Ahmic Aerosp Dayton OH USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

A novel class of non-linear estimators that minimizes the projection of the error on a multi-resolution basis is developed to improve the accuracy and efficiency of the multidimensional reconstruction of the heat-flux from discrete temperature sensors in non-planar hypersonic boundary layers. This approach uses the local temperature time derivative as the pre-estimator of the heat flux estimation risk in the inverse heat conduction problem. This new approach leads to improved results both in terms of computational efficiency and signal-to-noise ratio when compared to both regularization of the linear response operator and filtering of the temperature measurements. The approach is verified against an analytical verification test case, which shows significant accuracy improvement compared to optimal linear estimators and L2 regularization. It is then applied to experimental data to resolve the heat flux from noisy temperature data collected using fast-response sensors in the Virginia Tech hypersonic wind tunnel at Mach 6. The heat flux agrees very well with the Fay-Riddel approximation. Moreover, the heat transfer coefficient variation over the surface of the test is consistent with computational fluid dynamics simulations of the Reynolds Averaged Navier Stokes (RANS) equations.

关键词： Heat Flux Distribution Sensors Reynolds Averaged Navier Stokes Inverse Heat Conduction Hypersonic Wind Tunnels computational fluid dynamics simulation Heat Transfer Coefficients Boundary Layer Transition Temperature Sensors Integral Transform

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Flow Field Analysis of Vortex Interactions on Multi-Swept Wing Configurations

Flow Field Analysis of Vortex Interactions on Multi-Swept Wi...

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AIAA SciTech Forum

作者： Presas, Christian Park, Austin M. McCollum, Joeseph L. Avelar, Jacob A. Fagley, Casey Ghoreyshi, Mehdi Seide, Jurgen US Air Force Acad Dept Aeronaut Aeronaut Engn Usaf Acad CO 80840 USA US Air Force Acad Dept Aeronaut Usaf Acad CO 80840 USA US Air Force Acad High Performance Comp Res Ctr Aeronaut Engn Usaf Acad CO 80840 USA US Air Force Acad High Performance Comp Res Ctr Usaf Acad CO 80840 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

The underlying flow physics of vortex breakdown and vortex-vortex interactions at moderate to high angles of attack is not well understood. This lack of understanding is a challenge to the development of optimized wing designs for fighter aircraft. The goal of this study is to gain insight into the breakdown of vortices on multi-swept wing configurations. Two generic models were considered, one with a gradual vortex breakdown and one with a rapid (abrupt) breakdown. Aerodynamic forces were calculated from the US Air Force Academy (USAFA) subsonic wind tunnel to validate the experimental setup using computational fluid dynamics (CFD) and previous work. Stereoscopic particle imaging velocimetry (SPIV) was used to visualize vortex-vortex interactions, measure vortex strengths, and identify vortex breakdown locations. The measured lift and drag forces showed flow physics that agreed with previous experiments and CFD, supporting the validity of the new experimental setup. Analysis of SPIV and CFD data improved our understanding of the different types of vortex interactions observed for both models. The only difference between the models was the location of the secondary sweep angle on the chord. The C4L80 model, with a secondary sweep angle at 40% of the root chord, had a large shear layer along the leading edge, which led to vortex merging and gradual vortex breakdown at lower angles of attack than its counterpart. The C6L80 model, with a secondary sweep angle at 60% of the root chord, had no such shear layer and instead developed strong, isolated vortices that were characterized by vortex braiding and abrupt breakdown at high angles of attack. These vortices were entrained into the main vortex at the leading edge of the strake (inboard vortex), creating a balanced vortex system that enhanced lift and delayed the onset of gradual vortex breakdown seen in the C4L80 model.

关键词： Delta Wing Configuration Vortex Breakdown Critical Angle of Attack Mean Aerodynamic Chord computational fluid dynamics simulation Stereoscopic Particle Image Velocimetry Aerodynamic Coefficients Wind Tunnels Boundary Layer Thickness Fuselages

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CFD Predictions of Fluctuating Pressure Environments on NASA's SLS Ascent Unsteady Aerodynamics Wind Tunnel Test

CFD Predictions of Fluctuating Pressure Environments on NASA...

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AIAA SciTech Forum

作者： Boustani, Jonathan Hall, Leslie Steva, Thomas B. Mclaurin Aerosp Jacobs Space Explorat Grp Huntsville AL 35802 USA NASA Marshall Space Flight Ctr Aerosci Branch Huntsville AL 35808 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

This paper details work that is being conducted on predicting fluctuating pressure environments on NASA launch vehicles using computational fluid dynamics (CFD). The accurate characterization of these aeroacoustic environments is necessary in the analysis of vehicle structural capability and development of sub-component vibration design. High-fidelity simulations of the unsteady flow over NASA's SLS Ascent Unsteady Aerodynamics wind tunnel Test (AUAT) using the hybrid Reynolds-averaged Navier-Stokes (RANS)large eddy simulations (LES) methodologies in Mississippi States' Loci/CHEM solver are presented. The two available methods, Nelson-Nichols and dynamic hybrid RANS-LES (DHRL), are compared head-to-head on identical grids at twoMach numbers. At the high-subsonic Mach number, locally supersonic flow expanding over a shoulder induces a separation-reattachment system that is predicted poorly by the Nelson-Nichols method due to an under-prediction in unsteady content. The DHRL solution predicts the spatial extent and frequency domain response of this system well but under-predicts the peak noise levels due to a delay in the RANS-to-LES transition. At the low-supersonic Mach number, compression corner dynamics dominate the unsteady flow. While the Nelson-Nichols solution captures this phenomenon well, another solution on a refined grid indicates that some model stress depletion is occurring. The DHRL solution again performs well at this Mach number and matches the wind tunnel data fairly closely, but perhaps most impressively, is fairly agnostic to increasing grid resolution. The findings in this paper are expected to be generally applicable and will be used to guide the prediction of aeroacoustic environments of other NASA launch vehicles.

关键词： Unsteady Aerodynamics Unitary Plan Wind Tunnel computational fluid dynamics simulation Reynolds Averaged Navier Stokes Flow Instabilities Freestream Conditions Frequency Domain Launch Vehicles NASA Overall Sound Pressure Level

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