# Turbulent viscosity to viscosity ratio error

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 May 17, 2017, 07:43 Turbulent viscosity to viscosity ratio error #1 New Member   rameez shahab Join Date: May 2017 Posts: 2 Rep Power: 0 During my simulation of a propeller rotating in water. I am using Frozen Rotor Model and I am getting this error "Turbulence viscosity limited to viscosity ratio of 1e5 in 4,491,571 cells". I have tried changing and refining my grid and boundary conditions, but I get this error from start of my simulations. Please tell me how can I resolve this problem.

 May 19, 2017, 01:35 #2 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,665 Rep Power: 65 Is 4 million cells pretty much the entire grid? If it happens this way at the very 1st iteration and sticks around for many iterations, it's your initial condition. Play with your initialization. You can change your mesh and boundary conditions for the next 100 years but you still need to provide the correct initial conditions. If you're using k-epsilon model, you need to provide initial values for k and epsilon. For k-omega, you need to specify k and omega. Etc. Usually people guess reasonable values for velocity so it is usually not the culprit, but it can be. However, most people don't know how to guess what the initial value for k is (it's usually a small number). Similarly, epsilon and omega are usually very large numbers (in the hundreds and thousands). If you guess zeros or ones, then you'll be way off and run into these turbulent viscosity ratio problems. Rameez likes this.

 May 19, 2017, 19:16 #3 New Member   rameez shahab Join Date: May 2017 Posts: 2 Rep Power: 0 Thanks for the guidance. Yes, it is almost whole grid. I am using SA model, can you tell me if SA model is alright for my problem and if it is, what should I use initial conditions? If I give wrong boundary conditions, like if my velocity is too low or too high, will my simulation diverge? Any help would be appreciated. :-)

 Tags fluent, frozen rotor model, turbomachinery, turbulence

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