Insights Derived From Studies on the Interaction of Wall Jets With an Elevated Hump Wake

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Sehman, S. (2020). Insights Derived From Studies on the Interaction of Wall Jets With an Elevated Hump Wake. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

ABSTRACTSEAN M. SEHMAN. Insights Derived from Studies on the Interaction of Wall Jets with an Elevated Hump Wake (Under the Direction of DR. MESBAH UDDIN) Underneath a travelling road vehicle, a channel flow develops between the road and the undertray. This channel flow discharges behind the vehicle as a wall jet. Additionally, flow over the top of the vehicle almost always separates at some point along the body, creating a separated-flow region over and a wake region behind the vehicle, with which the underbody wall jet interacts. While this is a well-known flow configuration, the effects of varying wall jet parameters on the configuration have yet to be studied. This work employs Computational Fluid Dynamics (CFD) to model a traveling vehicle as a simple canonical flow, referred to herein as the wall-jet hump-wake, incorporating a wall jet discharging under the NASA hump wake. These wall-jet hump-wake simulations will be carried out in 2D using Reynolds-Averaged Navier-Stokes (RANS) turbulence modeling approaches. In order to accurately model the flow, validation case studies are carried out for a wall jet, a wall jet in a co-flowing stream, and the NASA hump wake based on previously published experimental works. Based on these validation case studies, a best fit turbulence model is identified, which proves to predict the defining characteristics of each flow to the highest degree of accuracy amongst all other models. The best fit model is then applied to the wall-jet hump-wake flow configuration for a total of nine different cases, each one varying either the wall jet slot height or the wall jet discharge velocity. Results are compiled and compared to shape the defining mean flow and turbulence characteristics of the wall-jet hump-wake. These defining quantities will be compared for the different cases run to determine the effects of wall jet slot height and wall jet discharge velocity on the wake flow. The overall objective of this thesis is to provide a detailed analysis on the interaction of wall jets with the hump induced wake and resultant drag parameters along the top of the body, in hopes that it will provide insight on the wall jet effects on the wake evolution and overall aerodynamic performance for further works. Results and findings can be later applied to vehicle models to investigate the potential of the readily available wall jet of a vehicle to improve aerodynamic performance.

Details
Author

Sehman, Sean

Title

Insights Derived From Studies on the Interaction of Wall Jets With an Elevated Hump Wake

Physical Description

1 online resource (159 pages) : PDF

Date

2020

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

ABSTRACTSEAN M. SEHMAN. Insights Derived from Studies on the Interaction of Wall Jets with an Elevated Hump Wake (Under the Direction of DR. MESBAH UDDIN) Underneath a travelling road vehicle, a channel flow develops between the road and the undertray. This channel flow discharges behind the vehicle as a wall jet. Additionally, flow over the top of the vehicle almost always separates at some point along the body, creating a separated-flow region over and a wake region behind the vehicle, with which the underbody wall jet interacts. While this is a well-known flow configuration, the effects of varying wall jet parameters on the configuration have yet to be studied. This work employs Computational Fluid Dynamics (CFD) to model a traveling vehicle as a simple canonical flow, referred to herein as the wall-jet hump-wake, incorporating a wall jet discharging under the NASA hump wake. These wall-jet hump-wake simulations will be carried out in 2D using Reynolds-Averaged Navier-Stokes (RANS) turbulence modeling approaches. In order to accurately model the flow, validation case studies are carried out for a wall jet, a wall jet in a co-flowing stream, and the NASA hump wake based on previously published experimental works. Based on these validation case studies, a best fit turbulence model is identified, which proves to predict the defining characteristics of each flow to the highest degree of accuracy amongst all other models. The best fit model is then applied to the wall-jet hump-wake flow configuration for a total of nine different cases, each one varying either the wall jet slot height or the wall jet discharge velocity. Results are compiled and compared to shape the defining mean flow and turbulence characteristics of the wall-jet hump-wake. These defining quantities will be compared for the different cases run to determine the effects of wall jet slot height and wall jet discharge velocity on the wake flow. The overall objective of this thesis is to provide a detailed analysis on the interaction of wall jets with the hump induced wake and resultant drag parameters along the top of the body, in hopes that it will provide insight on the wall jet effects on the wake evolution and overall aerodynamic performance for further works. Results and findings can be later applied to vehicle models to investigate the potential of the readily available wall jet of a vehicle to improve aerodynamic performance.

Genre

masters theses

Subjects--Topics

Mechanical engineering
Physics
Fluid mechanics

Degree

M.S.

Subject Area

Engineering

Advisor(s)

Uddin, Mesbah

Committee Members

Xu, Jun
Keanini, Russell

Degree Note

Thesis (M.S.)--University of North Carolina at Charlotte, 2020.

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Rights Holder Information

Copyright is held by the author unless otherwise indicated.

Identifier

Sehman_uncc_0694N_12666

Permalink

http://hdl.handle.net/20.500.13093/etd:2356