SENSITIVITY OF TURBULENCE CLOSURE COEFFICIENTS ON THE AERODYNAMIC PREDICTIONS OF FLOW OVER A SIMPLIFIED ROAD VEHICLE

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Dangeti, C. S. (2018). SENSITIVITY OF TURBULENCE CLOSURE COEFFICIENTS ON THE AERODYNAMIC PREDICTIONS OF FLOW OVER A SIMPLIFIED ROAD VEHICLE. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

Computational Fluid Dynamics (CFD) analysis of complex external flows is an important component of road vehicle design and development. The Reynolds Averaged Navier Stokes (RANS) turbulence modeling is widely used in the automotive industry for simulating these complex flows, because of its short turnover time and cost-effectiveness. Existing literature shows that the popular two-equation turbulence models like, the SST k − ω turbulence model, fail to produce good flow predictions when applied to a simplified car geometry, such as the Ahmed body, which exhibits flow features similar to real automotive flows. The present study improves the prediction capabilities of the SST k−ω turbulence model by tuning a few selected turbulence model closure coefficients for the 25° rear slant angle (φ = 25°) Ahmed body. This involves studying individual effects of these closure coefficients and then formulating a combination of these parameters that yields the best correlation with the experimental data. The best combination thus attained is then applied to scale resolved simulations such as the Improved Delayed Detached Eddy simulations (IDDES) for improved flow predictions. The tuning of closure coefficients was further applied to Ahmed body geometry with different slant angles (φ = 20° and φ = 35°). The present study reveals that a combination of the closure coefficients can be obtained that can lead to very well correlated force and flow predictions for each of the Ahmed body configurations. However, this tuned combination is not universal, and each slant angle requires a different combination of model closure coefficients. This, in turn, questions the validity of equilibrium assumptions used in postulating the turbulence model transport equations for flows with massive separation and reattachment.

Details
Author

Dangeti, Chamundeswar Sridhar

Title

SENSITIVITY OF TURBULENCE CLOSURE COEFFICIENTS ON THE AERODYNAMIC PREDICTIONS OF FLOW OVER A SIMPLIFIED ROAD VEHICLE

Physical Description

1 online resource (81 pages) : PDF

Date

2018

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

Computational Fluid Dynamics (CFD) analysis of complex external flows is an important component of road vehicle design and development. The Reynolds Averaged Navier Stokes (RANS) turbulence modeling is widely used in the automotive industry for simulating these complex flows, because of its short turnover time and cost-effectiveness. Existing literature shows that the popular two-equation turbulence models like, the SST k − ω turbulence model, fail to produce good flow predictions when applied to a simplified car geometry, such as the Ahmed body, which exhibits flow features similar to real automotive flows. The present study improves the prediction capabilities of the SST k−ω turbulence model by tuning a few selected turbulence model closure coefficients for the 25° rear slant angle (φ = 25°) Ahmed body. This involves studying individual effects of these closure coefficients and then formulating a combination of these parameters that yields the best correlation with the experimental data. The best combination thus attained is then applied to scale resolved simulations such as the Improved Delayed Detached Eddy simulations (IDDES) for improved flow predictions. The tuning of closure coefficients was further applied to Ahmed body geometry with different slant angles (φ = 20° and φ = 35°). The present study reveals that a combination of the closure coefficients can be obtained that can lead to very well correlated force and flow predictions for each of the Ahmed body configurations. However, this tuned combination is not universal, and each slant angle requires a different combination of model closure coefficients. This, in turn, questions the validity of equilibrium assumptions used in postulating the turbulence model transport equations for flows with massive separation and reattachment.

Genre

masters theses

Subjects--Topics

Mechanical engineering

Degree

M.S.

Keywords

Aerodynamics
CFD
RANS

Subject Area

Mechanical Engineering

Advisor(s)

Uddin, Mesbah

Committee Members

Tkacik, Peter
Vermillion, Christopher

Degree Note

Thesis (M.S.)--University of North Carolina at Charlotte, 2018.

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Rights Holder Information

Copyright is held by the author unless otherwise indicated.

Identifier

Dangeti_uncc_0694N_11856

Permalink

http://hdl.handle.net/20.500.13093/etd:242