# Turbulent viscosity ratio

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 June 4, 2005, 02:54 Turbulent viscosity ratio #1 Balaji Guest   Posts: n/a hi, I am solving 3d flow of species in closed domain.I am using standard k-e model for turbulence.It is a unsteady problem. After few time steps it displayed that turbulent viscosity ratio exceed the maximum limit.I have seen that upto few steps the turbulent viscosity ratio is constant.After that turb. Viscosity ratio builds up at each timestep at goes to the maximum limit within 10 time steps. Ofcourse this implies the K and intensity is getting increased.How can I control the turbulence properties. I am using time step of 10^-4 and velocity is 0.003m/s.Inlet K and e are calculaed based on Intensity and Hydraulic Dia. Thank you . Balaji

 June 9, 2005, 01:18 Re: Turbulent viscosity ratio #3 Balaji Guest   Posts: n/a Thank you for your response. I tried in coupled Solver it's working fine but the residuals are not coming down it is around 10^-1 for continuity and velocities. The FAS scheme I could find only in coupled explicit solvers. Thank you

 June 9, 2005, 02:53 Re: Turbulent viscosity ratio #4 zxaar Guest   Posts: n/a well for some time the continuity residuals will be at the place you have mentioned, or in fact they may increase slightly in the start, but if you observe almost all the other residuals will be coming down. if this is the case you are on correct path, just wait, once other residuals fall below some certain level continuity residuals will also fall, though slowly but they will.

 June 15, 2005, 13:07 Re: Turbulent viscosity ratio #5 Riaan Guest   Posts: n/a Simple fix - try and run the first 50-100 iterations using the S-A turbulence model then switch to the k-epsilon. -Riaan

 May 27, 2014, 03:47 #6 New Member   Peetak Mitra Join Date: Jul 2012 Posts: 19 Rep Power: 13 Hi, What effect does very high reynolds number flows have on the turbulence viscosity ratio? Is it safe to increase the upper limit in cases which involve Re in the range of 1000000 to 9000000? Thanks, peetak