Hi I'm running FLUENT simulation of NREL Phase VI turbine, I'm doing CFD analysis of two turbines placed in an array. It is a 10 meter dia two bladed turbine, rotating at 72rpm. I have placed the second turbine at 100m and 150m behind the first to know effect of wake on the second turbine. Whenever I run the simulation, I get the warning turbulent viscosity ratio exceeds 1e5 in this much number of cells and it goes on increasing, also continuity value instead of decreasing it goes on increasing.
Can anyone suggest me how to eradicate this error?
Hi Ijaz,
For how many iterations have you run the simulations before terminating it? Turbulent viscosity ratio is defined as the ratio of turbulent viscosity to dynamic viscosity and might exceed the specified limit in highly turbulent flows (which in your case is true). So basically it is not an error. Running the simulation for a larger number of iterations will eventually result in reduced number of cells where the ratio exceeds the limit. Also you should check your boundary conditions.
Hope this helps,
Aman
i have run around 1000 iterations brother.
Can I know how much distance you placed between two turbines in your work. Now I'm continuing running the simulation.
1000 iterations is a far far too low for such a simulation. A simple airfoil requires around 300,000 to 500,000 iterations to compute the transition location using the new transition models. For a wind turbine, it is far too less to compute the flow fields. Leave it on for a few nights :) .
I did only one turbine. Used the data from the study to use for my own model to predict dynamic stall on a downstream turbine. DIdnt place any downstream turbines in the wake.
It can happen with poor mesh, unrealistic boundary conditions...etc
See whether it is dying with time. Run for more iterations.
Also check, where in the mesh the value of turbulent viscosity is limited and then check the quality of the mesh there.
Regards,
Rajesh.
Hi Rajesh maximum skewness value of the mesh is 0.92. also warning occurs in 2nd windturbine,
You can change the limiter. This can be done in Solution Control and then Limits...
Hi J.L Ferrin Now I'm running two simulations one with the same limit, other I have increased the limit as u suggested.
But my frien told that increasing the limit will affect the flow prediction.
Also now I'm worried about the continuity as it goes on increasing to 1e51.
Then simply there are some flaws in your problem formulation, mesh or in boundary condition. I would like to suggest you to reconsider these things again and changing the solution control wont able to solve your problem it only change the control limits so not to do this and maintain the 10e-7 convergence criteria that is sufficient to resolve flow not need to run long simulation time.
good luck
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