CFD Approach to Evaluate External

Aerodynamic Simulation on FSAE Car

This project is done to understand the Aerodynamics at play

on a FSAE Car. A base case was set up and run. The number

of cells in the volume mesh for the base case was 4.95

million. Then modifications were done on the Wing and the

Number of Prism Layers to achieve a higher cell number of

5.11 million.

Objectives: >Aerodynamic Lift and Drag for different conditions of the Fluid Volume and the number of cells. >Subtraction Operation. >External Flow Analysis. >Surface Wrapper and Meshing Operation. >Prism Layer Quality. A model of an FSAE Car was given and we had to take into consideration the various parts of the car. Flow near the wings and the tires were to be considered very minutely and were to be refined based on the base case. Various parts of the car body were clubbed into one part. The parts which were to be considered and have been clubbed in the Car Assembly are Main Body, Sidepod Duct, Wheel Front and Rear, Wing Upper, Lower, Endplate and Upper Inner End Plate. The Physics set up models that were used are:

All y+ Wall Treatment

Cell Quality Remediation

Constant Density

Air was used as the Gas

Gradients (Hybrid Gauss LSQ and Venkatakrishnan)

K-Omega Turbulence

RANS

Segregated Flow

Steady State

Three Dimensional

Turbulent Flow

The FSAE Car model is shown below:

The Volume Mesh Properties for the Base case are given below:

The Base Case was set up and the view of the Mesh generated on the Upper Inner End Plate is shown below:

The Wing is shown below with a Mesh which shows some course cells in the edges:

The Down Force Plot is shown below:

The Body Downforce rises rapidly after 20N and after reaching a little above 100N remains

constant although there is regular rise and fall within the same parameters.

The Wing Downforce also rises rapidly after 20N but after reaching above 60N, it remains

constant and almost flattens out.

The Body and Wing Downforce interacts at around 70N.

The Drag Plot is shown below:

The Body Drag rises sharply and after reaching 60N, remains almost constant.

The Wing Drag does not rise sharply and at 10N, flattens out and remains the same throughout.

The Mass Flow Monitor is shown below:

The Mass Flow steeply falls and remains constant within 0.4 to 0.5 till the end.

The Residuals Plot is shown below:

The TKE rises in the beginning and then falls and remains constant throughout. All the other plots fall and then remains constant throughout.

The Velocity Scene is shown below:

The Sidepod duct shows some very high velocity areas upon closer look:

The Pressure scene is shown below:

Upon closer look at under the wing, it shows that the pressure is lower as shown in the figure below:

But the pressure below the tires is higher than under the wing.

The Streamlines appear as below:

The Base case has been shown above. Then changes were made to Wing Area. The Relative to Base size was 33% which was reduced to 28%. Also changes were made to y+ Wall treatment. The maximum value was selected to 1.5. The number of cells generated by the volume mesh was 5.11 million. The number of prism layers were increased to 7 from 6. The Volume Mesh Properties for the modified case are given below:

The mesh that was generated is shown below:

A closer look at the modified Mesh in the Wing area:

The mesh seems to be more finer than the previous case.

The Down Force Plot is shown below:

For the modified case the curvature is more for both Body Downforce and Wing Downforce than the previous case.

The Drag Plot is shown below:

The Body Drag does not touch the y-axis as much as the previous case.

The Mass Flow monitor is shown below:

The Mass Flow follows the same pattern as the previous case.

The Residuals Plot is given below:

Most of the parameters remain the same for the modified case but the X- Momentum follows a curve structure than the previous case.

The Velocity Scene is given below:

The Pressure Scene is shown below:

The Streamlines appear as below:

An additional Simulation of y+ Wall treatment is shown below:

Since we have used K-Omega Turbulence model, this simulation was done to see if there is improved performance for boundary layers under adverse pressure gradients.