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 suitto March 21, 2000 12:10

Modelling Ceiling Fan

Dear All, Using Fluent5.3, i am trying to model the flow inside a room (5x5x3m) with a ceiling fan (blade radius 0.6m). The gap between the fan and ceiling is assumed to be 0.5m. There is a window on one side of the wall (1.5x1.0m).

i have tried to model the fan as a 'fan b.c.'. The airflow velocity measured beneath the fan was measured to be 1.5m/s. So using Bernoulli's Eqn, and assume the air above the fan is 0m/s, the pressure jump across the fan is computed to be -1.378Pa.

i am using the k-e turb model & standard wall function. Convergence for u,v,w,k&e were excellent but the continuity eqn residue (non-normalised) hangs above 0.001.

Please advise on where could have gone wrong, and is my modelling correct. Thanks a lot.

ps: i have drawn a jpeg diagram of the setup. i dunno how to post it on this forum. So email me if you would like to take a closer look at the problem.

 Chetan Polavaram March 21, 2000 12:46

Re: Modelling Ceiling Fan

Hi

I have had the same problem when I tried to model turbulent flow thro straight pipes.

One thing I did was adapted the grid based on TKE. You can try doing the same thing. After adapting if you find the residuals levelling off at the same point where they did earlier then just go with what you have. If the residuals level off lower than what they did then you can try adapting till there is no considerable change in pressure(grid independent). One more thing you could do is to reduce the under-relaxation factors.

Good luck, Chetan

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