Ahmed Body Aerodynamic Study, ANSYS Fluent Simulation

Using ANSYS Fluent, a summary of Ahmed Body Aerodynamic Study

Project Description

A simple model to investigate aerodynamic traits pertinent to car design is the Ahmed body.  This work analyzes the incompressible isothermal airflow around the Ahmed body, a 1-meter automobile model inside a 25-meter wind tunnel using an ANSYS Fluent CFD simulation.  Simulating an automobile speed of 72 km/h, the intention is to evaluate numerical models and compute drag values at an input speed of 20 m/s.

Geometry and Meshing

• Geometry Setup: The Ahmed body is housed in a wind tunnel; the blue face serves as the inlet and the red face as the outlet.
• Meshing: ANSYS Meshing produces a 624,482 element mesh.  With 10 prism layers added to precisely capture the border layer, a maximum skewness of 0.84 and an average of 0.22 guarantee sufficient quality.

Methodology: Body Aerodynamic Study of Ahmed

• Solver Setup: Solver based on pressure with consistent-state flow behavior.
• Turbulence Model: Simulates turbulence using the k-w SST model in view of gravitational influences.

Conclusion

Many results are observed upon convergence of the solution:

• Convergence Criteria: Drag force stabilization and residuals less than 10^-5 mark the convergence of the solution.  With a maximum Y-plus value of 60, boundary layer resolution is clearly efficient.
• Validation: A chaotic benchmark for verifying numerical models is the Ahmed body.  Results of this work can be matched with drag, flow separation, and separation angle experiments.
• LES/DES Suitability: The Ahmed body is fit for high-quality LES/DES simulations to investigate turbulence features in automotive applications because of its basic form.

Results

• Velocity and Pressure Fields: While maximum pressure develops at the front face's center where velocity is lowest, highest velocity is seen at the corners.
• Streamlines: Share observations on flow patterns surrounding the Ahmed body.
• Drag Force: computed for the specified model and conditions to be 15.091 N, exact.