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Old   October 16, 2004, 15:05
Default HELP: rotating mesh turbulence model
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hello, i have tried many simulations but am not getting the correct result. please help and please be patient with the description. i am a newbie. radial fan with seven blades, blade with beta1=8degrees beta2 = 153 i.e. blade is convex with logarithmic spiral inlet. blade-inlet region having diameter of 36 mm and 4 mm in height). blade-outlet set to be 2 mm heigh. blade is 12 mm long. model has around 1.3 million cells (tetra). omega = 22500 rpm. (multireference, implicit) reference pressure:100000 Pa. i want a presuure gain of 4000 Pa, relative to reference pressure of 100000 Pa (1 bar) and volume flow rate of 0.0025 m^3/s at inlet. result: pressure LOSS at many regions (not gain as a radial ventilator should do) and clear velocity direction at spiral outlet BUT at some discrete points the velocity is very high (around 100 m/s instad of around 10 m/s). Boundary condition: 1) inlet (around 0.8 Diameter of rotating region) with velocity of 8 m/s. 2) outlet: (a short piece from log.outlet): split/fixed. Model: k-epsilon, high Re quadratic. SMPLISO, MARS for U,V,W and Turbulence intensity (5 %), length scale (0.36 mm). maximum iterations: 1000 with residual 0.001 but after around 300 iterations the result "converged". there were very few warnings in PLease help BECAUSE OF DEADLINE.
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Old   October 16, 2004, 19:37
Default Re: HELP: rotating mesh turbulence model
Jörn Beilke
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Why dont you use the pressure difference as boundary condition. Pressure inlet and pressure outlet are fine. Then calculate the mass flux and that's it (in theorie).

You should not expect to get correct results from a rotating frames calculation. I run all of my turbomachinery cases with sliding mesh.

A converged result does not mean anything about the quality of the results.

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Old   October 16, 2004, 20:18
Default Re: HELP: rotating mesh turbulence model
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but wt to do fro steady state calculation. still we have run on sliding mesh

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