Date of Award

12-2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Omar, Mohammad A

Committee Member

Ayalew , Beshah

Committee Member

Hung , Stephen T

Abstract

A two dimensional and three dimensional computational study has been carried out respectively regarding aerodynamic forces affecting a symmetric airfoil, NACA0015 and a cambered airfoil, NACA2414. The negative lift (down force) and drag forces were predicted through the simulation of airflows over inverted rear-wings in different configurations namely; varying incidences i.e. angles of attack of the airfoils, two dimensional cross section of the inverted rear wings to be mounted on back of a car, and varying speeds of initial airflow.
The downforce increases as the angle of attack increases however, if an inverted rear wing is fixed on a car at high angle of attacks the rearwing starts to stall which is not a desired condition affecting the vehicle stability. Furthermore, the camberness added to the airfoil increased the downforce, which contributes more to the stability concept of the automobile.
Consequently, three dimensional simulations have evaluated effects of the 3D features of the airflow over the rearwings of a road car. The features are tip vortices along the upper edge, the lower edge and at the tip in addition to the sheet vortex along the trailing edge. The visualizations of the vortex vectors and streamlines explicitly depicted the features. The contour and the 2D plots of the pressure distribution over the inverted rearwings, set at angle of attack of 4° illustrated the effects of the airflow features. The tip vortices and the vortex sheets decrease the downforce.

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