Car (AUDI) External Airflow CFD Simulation

Project Description

The present problem simulates the external airflow on the body of an AUDI vehicle using ANSYS Fluent software. A rectangular cube area is considered as the computational domain of the open air flow in which the wind enters this computational area at a speed of 77.76 m.s-1, horizontally. This wind flow hits the front of the car directly and creates aerodynamic forces on the car.

Car Geometry & Mesh

The 3-D geometry of the model is designed using Design Modeler software. The present model includes a rectangular cubic computational domain with dimensions of 20 m * 10 m * 5 m for airflow, in which an AUDI vehicle is located. The following figure shows a view of the geometry.

The meshing of the model has been done using ANSYS Meshing software and the mesh type is unstructured. The element number is 4950697, and the meshing accuracy is higher in the vicinity of the vehicle surfaces. The following figure shows the mesh.

Car External Airflow CFD Simulation

To simulate the present model, several assumptions are considered:

• We perform a pressure-based solver.
• The simulation is steady.
• The gravity effect on the fluid is ignored.

A summary of the defining steps of the problem and its solution is given in the following table:

Models (car)
k-epsilon	Viscous model
Standard	k-epsilon model
Standard wall function	near wall treatment
Boundary conditions (car)
Velocity Inlet	Inlet
77.76 m.s-1	velocity magnitude
Pressure Outlet			Outlet
0 Pascal	gauge pressure
Wall	Wall of AUDI
stationary wall	wall motion
Solution Methods (car)
PISO			Pressure-velocity coupling
Second order	pressure		Spatial discretization
Second order upwind	momentum
First order upwind	turbulent kinetic energy
First order upwind	turbulent dissipation rate
Initialization (car)
Standard	Initialization method
0 Pa	gauge pressure
77.76 m.s-1	x-velocity
0 m.s-1	y-velocity , z-velocity

Results

At the end of the solution process, two-dimensional and three-dimensional velocity and pressure contours, as well as path lines and velocity vector, are obtained. Also, the pressure and shear stress contours on the surface of the car body, and the graph of drag and lift coefficients in term of the number of the iteration are obtained.

There is a mesh file in this product. By the way, the Training File presents how to solve the problem and extract all desired results.