Hi, i have very simply geometry, two line horizontal parrallel 1 cm far.The upper move at costant velocity at the finish of simulation ( residual ~ 1e-14) i report the force to pull the upper line and the force to take stationary the bottom line. i use laminar model for viscosity. i have found that at v=0,004 m/s two Force are very different, while at v=0,00004 m/s the two Force are similar ( to evaluate the force i have subtract the inlet zone initial line over and initial line under to minimize the edge effect) this is turbulance?? plz help me it's importat thank you

Dear Ereka: In this range of reynolds number there is no turbulence and so you don't need any turbulence modeling. However, no turbulnce effect could be seen while you use a turbulnce modeling even if you have a turbulent flow in real.

Your velocity is too small (0.00004) and numerical diffusion can change your answers. the changes could be arised from this. Also you should not give same force on the two plates in couette flow problem.

Regards