CFD (Computational Fluid Dynamics)

CFD is a completely virtual method of aero development.  It solves the physical equations of fluid flow using powerful computers to give a complete picture of the flow field around and through the test vehicle.

CFD has many advantages compared to wind tunnel testing.
  • The entire flow field in and around the test vehicle is solved.  This data can then be analysed to calculate forces and pressures as with a wind tunnel model, but also to give on and off body streamlines and numerous other fluid characteristics (vorticity, shear stresses, total pressures etc).  This additional flow field knowledge can be very useful during the design process. 
  • CFD can simulate non-linear flows.  During cornering, racing cars travel in a circular path, hence so does the air flowing over them.  Wind tunnels cannot model this, though they can come close by running in a non-symmetrical yawed condition.
  • Reliability.  CFD is a completely computer based technique.  Unlike wind tunnels, there is little that can break or fail.
  • Optimisation techniques.  CFD codes can feedback on themselves and can automatically iterate to find an optimum solution to a given multi-parameter problem.
  • CFD can feed data directly into FEA packages for structural analysis.
  • CFD can be cost effective (this will depend on circumstances, so click here for an explanation).
  • CFD can be very fast (this will depend on circumstances, so click here for an explanation).
CFD also has disadvantages compared to wind tunnel testing.
  • CFD only solves simplifications and approximations of the full equations of flow.  Usually the errors introduced by these approximations are small, but not always. Historically, CFD methods have struggled to accurately predict flow separations.  CFD techniques improve all the time, but these approximations can still be a source of significant errors, especially as racing cars tend to feature several, large areas of unsteady separated flow. The correlation of CFD predictions to actual on vehicle performance can be poor.
  • CFD can be very expensive (this will depend on circumstances, so click here for an explanation).
  • CFD can be very slow (this will depend on circumstances, so click here for an explanation).

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