Real-time flight simulation with highly resolved wind fields from a LES model

Author(s):  
Xinying Liu ◽  
Julien Gérard Anet ◽  
Leonardo Manfriani ◽  
Yongling Fu

<p>An overproportioned number of accidents involving general aviation occur in complex terrain. According to the statistics included in the accident investigation reports published by the Swiss Transportation Safety Investigation Board, in some cases, pilots overestimated the energy reserves of their aircraft leading to a loss of control. In order to increase flight safety for private pilots in mountainous regions, on behalf of the Swiss Federal Office of Civil Aviation, the Centre for Aviation (ZAV) at the Zurich University of Applied Sciences  develops an energy management system for general aviation, which displays the remaining airplane’s energy reserves taking into account meteorological information. The research project comprises two phases: i) concept and feasibility study and ii) prototype development. The project is currently running in phase one. In this phase, the first implementation of the energy management system was completed. The system was evaluated in the ZAV’s Research and Didactics Simulator (ReDSim). In order to generate highly resolved wind fields in the ReDsim, a well-established large-eddy simulation model, the Parallelized Large-Eddy Simulation (PALM) framework, was used in the concept study, focusing on a small mountainous region in Switzerland, not far from Samedan. For a more realistic representation of specific meteorological situations, PALM was driven with boundary conditions extracted from the COSMO-1 reanalysis of MeteoSwiss. The environment model in the ReDSim was modified to include a new subsystem simulating atmospheric disturbance. The essential variables (wind components, temperature and pressure) were extractred from the PALM output and fed into the subsystem after interpolation to obtain the values at any instant and any aircraft position. Within the subsystem, it is also possible to generate statistical atmospheric turbulence based on the Dryden turbulence model which refers to the military specification MIL-F-8785. This work focuses on the presentation of the PALM model setup and discusses the COSMO-1 forced PALM simulation results, including a statistical comparison of the simulation results with meteorological data from different meteorological reference stations.</p>

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Yan Xu ◽  
Zunce Wang ◽  
Lin Ke ◽  
Sen Li ◽  
Jinglong Zhang

Reynolds Stress Model and Large Eddy Simulation are used to respectively perform numerical simulation for the flow field of a hydrocyclone. The three-dimensional hexahedral computational grids were generated. Turbulence intensity, vorticity, and the velocity distribution of different cross sections were gained. The velocity simulation results were compared with the LDV test results, and the results indicated that Large Eddy Simulation was more close to LDV experimental data. Large Eddy Simulation was a relatively appropriate method for simulation of flow field within a hydrocyclone.


Author(s):  
Tuy N. M. Phan ◽  
John C. Wells ◽  
William D. Kirkey ◽  
Mohammad S. Islam ◽  
James S. Bonner

Large-eddy simulation (LES) has been conducted under idealized conditions in two river reaches of the Hudson River (New York, USA), with near-bank resolution set to some 5 meters in order to resolve large-scale motions of turbulence in the near-bank regions. To simplify analysis, simulation is performed at a constant discharge corresponding to a typical ebb tide. A standard Smagorinsky model is implemented in the commercial package FLUENT, with buoyancy neglected and bottom roughness set to zero. We perform Proper Orthogonal Decomposition (POD) on the LES results. POD modes are orthogonal flow fields that capture the kinetic energy in an optimally convergent fashion. Results show that only a few POD modes are enough to describe the most energetic flow dynamics. In a reach around the Indian Point power plant, the second and third modes reflect an interesting generation of separating eddies on the western bank, which we do not find with a URANS (standard k-ε) computation on the same grid. To test our simulation, a comparison of simulation results with other simulation results and Acoustic Doppler Current Profiler (ADCP) data measured at West Point, New York will be presented.


Author(s):  
Parisa Golchoubian ◽  
Nasser L. Azad

In this study, the potential merits of integrating a supercapacitor into an electric vehicle (EV), namely a Toyota RAV4 EV, is investigated. In particular, the impacts of energy management system (EMS) with a buffer scheme and a dynamic programming (DP)-based control law on the vehicle performance characteristics are examined and compared to the vehicle with no supercapacitor in use. While the simulation results show improvements in the vehicle’s driving range and heat loss for the both considered EMSs, the DP-based controller significantly outperforms the buffer policy. The investigations also demonstrate promising results regarding the use of supercapacitors in EVs, intriguing interest for further studies on online control strategies for these systems.


2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Juan M. Mejía ◽  
Amsini Sadiki ◽  
Alejandro Molina ◽  
Farid Chejne ◽  
Pradeep Pantangi

Accurate subgrid-scale (SGS) scalar flux models are essential when large eddy simulation (LES) is used to represent flow, mixing and transport of passive and active scalars in engineering, and environmental applications in turbulent regime. Many SGS scalar flux models have been developed for flows with low Schmidt numbers (Sc), but their application to high Sc flows has important limitations. In high Sc flows, the behavior of the scalar field becomes anisotropic because of intermittency effects, phenomenon that must be accounted for by SGS scalar flux models. The objective of this paper is to evaluate the ability of three SGS scalar flux models to predict the scalar behavior of a high Sc-number flow configuration, namely the anisotropy-resolved SGS scalar flux model: (1) appropriate for high Sc-number flow configurations, and two additional SGS models (linear eddy diffusivity based SGS models) with (2) constant, and (3) dynamically calculated turbulent Schmidt number. The LES simulation results accomplished by these models are compared to each other and to experimental data of a turbulent round jet discharging a diluted scalar into a low-velocity coflowing water stream. The comparison of simulation results and experimental observations shows that, in general, all SGS models reproduce the mean filtered concentration distribution in radial direction. The dynamic eddy diffusivity and anisotropy models reproduce the rms of the concentration and SGS scalar fluxes distribution. In particular, the anisotropy model improves the prediction reliability of LES. However, the three models evaluated in this study cannot accurately predict the scalar behavior at the superviscous layer. Finally, this work demonstrates that complex models can achieve reliable predictions on reasonable grids using less computational effort, while simple models require fine grids with increased computational costs.


1997 ◽  
Vol 119 (2) ◽  
pp. 248-262 ◽  
Author(s):  
W. Rodi ◽  
J. H. Ferziger ◽  
M. Breuer ◽  
M. Pourquie´e

Designs ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 34
Author(s):  
Yi Wang ◽  
Giulio Vita ◽  
Bruño Fraga ◽  
Jianchun Wang ◽  
Hassan Hemida

For large eddy simulation, it is critical to choose the suitable turbulent inlet boundary condition as it significantly affects the calculated flow field. In this paper, the effect of different inlet boundary conditions, including random method (RAND), Lund method, and divergence-free synthetic eddies method (DFSEM), on the flow in a channel with a hump are investigated through large-eddy simulation. The simulation results are further compared with experimental data. It has been found that turbulence is nearly fully developed in the case based on the Lund method, not fully developed in the case based on DFSEM, and not developed in the case based on the RAND method. In the flow region before the hump, mean velocity profiles in the case applying the Lund method gradually fit the law of the wall as the main flow moves towards the hump, but the simulation results based on the RAND and DFSEM methods cannot fit the wall function. In the flow region after the hump, cases applying Lund and DFSEM methods could relative precisely predict the size of turbulent bubble and turbulent statistics profiles. Meanwhile, the case based on the RAND method cannot capture the positions of flow separation and re-attachment point and overestimates the turbulent bubble size. From this research, it could be found that different turbulent inflow generation methods have a manifested impact on the flow separation and re-attachment after the hump. If the coherent turbulence is maintained in the approach flow, even though turbulent intensity is not large enough, the simulation can still predict the flow separation and turbulent bubble size relative precisely.


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