Car (AUDI) External Flow CFD Simulation, ANSYS Fluent Training

Description

This project will study an incompressible isothermal air flow adjacent to an Audi-A4-2017 car by ANSYS Fluent software. The maximum speed of 77.76 m / s, which is relatively high, is selected for the testing, and the drag force value is obtained.

Car Methodology

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 model meshing 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.

Car Conclusion

After the solution has been converged, the results could be observed through post-processing. Meanwhile, the drag value was monitored during the solution iterations to assure an excellent convergence.

In this study, the solution was a converged one when the drag force reached a constant value and the residuals were below 10-5 values. As the results show, most drag forces are due to pressure forces, and the share of frictional forces in drag is low.

The highest pressure occurred in the front and back of the car, which happened in these areas due to the minimum velocity contour. The velocity vectors indicate that there is flow separation at the front and rear of the vehicle.

This separation is more concentrated in the front of the car and is wider in the back of the vehicle, which can be attributed to the broader geometry in the back of the car. The pressure on the surface of the car body is almost evenly distributed, but in areas with a greater angle to the flow direction, this pressure is higher.

The more perpendicular the surface is to the flow, the greater the pressure on it. Also, the pressure on the sharp edges, especially on the front wheel and the edge of the front window, is negative, and the speed in these areas has increased, which can be attributed to the rapid change in the flow angle due to the change in fracture.

The Shear force contours also show that the flow separation started when these contours changed sign. The drag force obtained in this problem is 1684.74 Newtons.