CFD programming tricks?
 

Recently I've been reading the CFL3D 5.0 manual.On page 273. I found a problem that comfused me:The last 7 lines says that for nonlinear turbulent models,one has to add the additinal nonlinear terms to Reynolds stress Tau(ij) in the momentum equations,it's quite reasonalbe.However later it says miu*Laplace(k) (k is turbulent kinetic energy)should also be added to energy equations,why? It doesn't make sense.Is it because that 5.0 edition of CFL3D uses thin layer approximation so that this additonal term should be considered?If I has to modify this code for full N-S computation,how should I deal with these additional nonlinear terms? Thank you for your reply.