# Problem with Residual plot raising up to hige numbers na do not converge

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 March 14, 2014, 16:22 Problem with Residual plot raising up to hige numbers na do not converge #1 New Member   Fardin Khalili Join Date: Feb 2014 Posts: 10 Rep Power: 5 Hi, I am working ono my thesis about CFD and Aeroacoustics of wind turbine with rotating blades. I got perfect results when I ran my simulation in steady-state condition for Curle and Proudman noise Models. For example I followed the first tutorial for aeroacoustics and the results were OK and I got convergence near to 10^-4 for residual plot. But, when I change the physics to unsteady, and change the motion to rotating, either using Reynolds-Averaged Navier-Stokes or DES or LES, everything goes wrong and the residual plot rises to hige numbers up to 10^7!!!! I change the motion to stationary or rotation but nothing got better. What is your opinion and how can I solve this problem.

 March 14, 2014, 16:26 Errors while running the program #2 New Member   Fardin Khalili Join Date: Feb 2014 Posts: 10 Rep Power: 5 pressure corrections limited on 9 cells in STATIC pressure corrections limited on 60083 cells in ROTATING Temperature corrections limited on 327 cells in STATIC Temperature corrections limited on 34752 cells in ROTATING Minimum Temperature limited to 100 on 439 cells in ROTATING Maximum Temperature limited to 5000 on 405 cells in ROTATING Maximum Temperature limited to 5000 on 33 faces on Wind Turbine Rotor.Default Temperature limited to maximum value 1270 times on model-part "ROTATING" Breaking out of time step iteration. Time solution is in an inconsistent state.

March 14, 2014, 16:28
residual plot for first iterations
#3
New Member

Fardin Khalili
Join Date: Feb 2014
Posts: 10
Rep Power: 5
And here is the residual plot for first iterations.
Attached Images
 V.1_Residuals.jpg (44.2 KB, 61 views)

 March 19, 2014, 15:27 #4 Senior Member   Join Date: Nov 2010 Location: USA Posts: 943 Rep Power: 14 How are you initializing the transient simulation? Is the flowfield static and your turbine suddenly is spinning at maximum RPM? That will be very difficult to converge, you need to ramp its speed or start your solution off from your steady-state solution.

 March 25, 2014, 10:35 #5 Senior Member   Ping Join Date: Mar 2009 Posts: 314 Rep Power: 12 you should certainly be starting your unsteady solve from a reasonably converged steady run - very easy to do. also check your timestep - i suggest one that gives you about 1 degree of rotation per timestep.

 Tags aeroacoustics, residual, star ccm+, unsteady, wind turbine

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