CFD on a Le Mans Prototype

I am following STAR-CCM+’s Tutorial Guide to get to know the CFD software before starting to work on my actual thesis. Surprisingly, in one of the first chapters we learn about Parts Based Meshing: External Aerodynamics using the geometry of a Le Mans Prototype (LMP) as the subject of study.

Figure 1. Geometry for the external aerodynamic analysis using the parts-based approach.
Figure 1. Geometry for the external aerodynamic analysis using the parts-based approach.

This part of the Tutorial is only about meshing, but, taking advantage of the fact that the mesh is already prepared and the boundaries are defined I will try to simulate the air flow around the LMP. For that I will follow the instructions provided by CD-adapco in their Best Practices for Vehicle Simulations, though I will skip some steps as for now I just want to get a first approximation to the solution.

Figure 2. Mesh generated following the User Guide's Tutorial.
Figure 2. Mesh generated following the User Guide’s Tutorial.

Setting Up the Physics Models

Physic models define the primary variables of the simulation, including pressure, temperature and velocity, and the mathematical formulation. Here I will use turbulent and compressible flow.

Selecting Models

According to CD-adapco, either SST (Menter) K-Omega or Spalart-Allmaras Detached Eddy Simulation model is recommended for vehicle aerodynamics —both seem to give similar results.

The physics model used for this problem is:

  • Time: Steady.
  • Material: Gas.
  • Flow: Coupled Flow.
  • Equation of State: Ideal Gas.
  • Viscous Regime: Turbulent.
  • Reynolds-Averaged Turbulence: Spallart-Allmaras Turbulence.

Setting Initial Conditions

Initial conditions in a continuum specify the initial field data for the simulation.

In steady-state simulations, the solution ought to converge independently of the initial field. However, the initial field still affects the path to convergence, and with it the cost of computing power.

  • Velocity: 150 kph.
  • Static Temperature: 300 K.
  • Turbulent Viscosity Ratio: 10.
  • Reference Pressure: 101325 Pa.

Preliminary results

After a couple hundred iterations we can show some of the results, though the solution has not fully converged.

CFD generated velocity magnitude in the le mans prototype's symmetry plane.
Figure 3. Velocity magnitude in the car’s symmetry plane.
CFD generated streamlines and contours of pressure on a le mans prototype.
Figure 4. Streamlines colored by velocity and contours of pressure.

The tutorial comes with the geometry for three different wing settings which I will try to test and compare. But that is something I will put off; in the meantime I have almost 3000 pages of tutorials ahead I want to look over.