# Vehicle Aerodynamics

Topics: Drag, Viscosity, Aerodynamics Pages: 3 (818 words) Published: March 18, 2013
CFD PROJECT REPORT

Submitted by Sai Yashwanth M

IMPACT OF AERODYNAMICS ON AUTOMOBILES
INTRODUCTION Aerodynamic forces are caused by the relative motion of automobiles with air and they cause:  Drag (resistance to forward motion)  Lift / down force (come into play during cornering and acceleration)  Lateral forces (comes into play during cornering)  Moments in roll, pitch and yaw As a result these factors have to be taken into consideration during automobile design. THEORY BEHIND AERODYNAMIC FORCES The sources of aerodynamic forces are  Viscous forces  Drag (form drag) The major among both of these is the form drag caused by pressure differences between the front part and back part of the vehicle.

EFFECT OF VEHICLE DESIGN ON DRAG & DOWNFORCE
In this project an effort is made to study the effects of vehicle design on drag and down-force. A CFD analysis of air-flow around an automobile is carried out using the following vehicle designs.  Jeep  Sedan  Fast sedan  Sedan with a spoiler The first three are used to study drag and the last is used to study down-force. The following figures Fig. 1, 2, 3, 4 show the 2-D models of the above mentioned vehicle designs:

Fig.1 A 2-D model of a ‘Jeep’.

Fig.2 A 2-D model of a ‘Sedan’.

Fig.3 A 2-D model of a ‘Fast Sedan’.

Fig.4 A 2-D model of a sedan with a rear wing (spoiler).

CFD ANALYSIS OF AIR FLOW OVER VEHICLES
The pressure field across the vehicles is solved in the commercial software ANSYS. The following section describes the procedure used to solve the pressure and velocity fields.

METHODOLOGY
 Creation of 2-D models of different vehicle design is carried out in Pro-Engineer and imported to ANSYS  Solution domain (domain of interest) is created using enclosures of required dimensions and air is chosen as its medium.  Meshing of the solution domain is done using automatic mesh generator. Initially a coarse meshing done and after realistic solutions are obtained the mesh is made...