NUMERICAL INVESTIGATIONS ON THE AERODYNAMICS OF GROUND VEHICLES IN PLATOON USING THE FASTBACK DRIVAER MODEL

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Rajasekar, S. (2018). NUMERICAL INVESTIGATIONS ON THE AERODYNAMICS OF GROUND VEHICLES IN PLATOON USING THE FASTBACK DRIVAER MODEL. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

Work concerning aerodynamic optimization of isolated vehicle shapes is available in abundance in existing literature, unlike vehicle interaction studies. Due to its simplicity, all previous studies aimed at understanding the aerodynamic interference effects were carried out primarily using the Ahmed body as the vehicle model. Wind tunnel studies on vehicle interferences using an actual car geometry would be expensive and complicated owing to the geometric limitations of the test facility and the associated difficulties in measurement techniques employed. The work presented in this thesis explores the aerodynamic prediction capabilities of popular turbulence models, used in present-day computational fluid dynamics simulations, using a realistic car model in a platoon. A simulation methodology is first developed using a tandem arrangement of surface-mounted cubes considering the availability of experimental data for CFD correlation and validation. The influence of turbulence model closure coefficients on the prediction capabilities is tested first and a combination of modified coefficients is selected that improves the overall predictions of the SST k-ω turbulence model. Validation studies reveal the inability of the Unsteady Reynolds-Averaged Navier-Stokes (URANS) models to resolve the far wake and hence its frailty in simulating multiple body interactions. Improved Delayed Detached Eddy Simulations (IDDES) models, on the other hand, are able to resolve the wakes with a reasonable accuracy. The simulation methodology is then applied to the fastback DrivAer model at different longitudinal spacings. The results show that, as the longitudinal spacing is reduced, the trailing car’s drag is increased while the leading car’s drag is decreased. The current study supports the prior explanation of vortex impingement as the reason for drag changes. Unlike Ahmed bodies, the trailing model does not return to an isolated state at two car-length separation. The resolution of the far wake of a detailed DrivAer model and its implication on the CFD characterization of vehicle interaction aerodynamics needs further investigations.

Details
Author

Rajasekar, Sudhan

Title

NUMERICAL INVESTIGATIONS ON THE AERODYNAMICS OF GROUND VEHICLES IN PLATOON USING THE FASTBACK DRIVAER MODEL

Physical Description

1 online resource (94 pages) : PDF

Date

2018

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

Work concerning aerodynamic optimization of isolated vehicle shapes is available in abundance in existing literature, unlike vehicle interaction studies. Due to its simplicity, all previous studies aimed at understanding the aerodynamic interference effects were carried out primarily using the Ahmed body as the vehicle model. Wind tunnel studies on vehicle interferences using an actual car geometry would be expensive and complicated owing to the geometric limitations of the test facility and the associated difficulties in measurement techniques employed. The work presented in this thesis explores the aerodynamic prediction capabilities of popular turbulence models, used in present-day computational fluid dynamics simulations, using a realistic car model in a platoon. A simulation methodology is first developed using a tandem arrangement of surface-mounted cubes considering the availability of experimental data for CFD correlation and validation. The influence of turbulence model closure coefficients on the prediction capabilities is tested first and a combination of modified coefficients is selected that improves the overall predictions of the SST k-ω turbulence model. Validation studies reveal the inability of the Unsteady Reynolds-Averaged Navier-Stokes (URANS) models to resolve the far wake and hence its frailty in simulating multiple body interactions. Improved Delayed Detached Eddy Simulations (IDDES) models, on the other hand, are able to resolve the wakes with a reasonable accuracy. The simulation methodology is then applied to the fastback DrivAer model at different longitudinal spacings. The results show that, as the longitudinal spacing is reduced, the trailing car’s drag is increased while the leading car’s drag is decreased. The current study supports the prior explanation of vortex impingement as the reason for drag changes. Unlike Ahmed bodies, the trailing model does not return to an isolated state at two car-length separation. The resolution of the far wake of a detailed DrivAer model and its implication on the CFD characterization of vehicle interaction aerodynamics needs further investigations.

Genre

masters theses

Subjects--Topics

Mechanical engineering
Automobiles--Design and construction
Aerospace engineering

Degree

M.S.

Keywords

Aerodynamic Interferences
Drivaer
Platoon
Surface-Mounted Cube
Tandem
Vehicle Interaction

Subject Area

Mechanical Engineering

Advisor(s)

Uddin, Mesbah

Committee Members

Vermillion, Christopher
Tkacik, Peter T.

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

Rajasekar_uncc_0694N_11862

Permalink

http://hdl.handle.net/20.500.13093/etd:1604