contradicting results of different turbulent model

dani

hi, i am working on turbulent flow over flat plate.i ran the fluent for Spalart Allmaras,K-omega (standard),K-epsilon(standard) and Reynold stress model for same geometry and flow conditions.i got similar velocity profile at outlet.But problem is that' i am getting order of magnitude difference in the values of "turbulent viscosity" for each model especially the difference in the values of Spalart-Allmaras model and K-omega model is very wide. can anybody explain why turbulent viscosity is so different. thanks