hello for automotive application how and at what stage y+ is applied .anybody please thanks

which automotive application you mean to say? suppose if you are calculating drag coefficient on your vehicle using relaizable k epsilon model, then your y+ shall be somewhere between 30 to 100. so if you intend to maintain the Y+ you can adjust the first prism height at the boundary accordingly.

o.k fine thank you for the information. Actually what i want to know is whether y+ is applied before volume meshing or after.Normal steps followed in solving aerodynamics problem are (car geometry+virtual wind tunnel+geometry clean up+surface mesh+volume mesh) So in this process when to apply y+. It would be very glad if you could answer my second querry also. Fluent gives skin friction coefficient.Whether this should be treated as total drag or else how to work out total drag (Pressure drag+skin friction drag) or is it a pressure drag as car is more or less a bluff body and has a pressure drag as measure component. thank you again.