# udf explaination

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 May 4, 2012, 12:36 #2 Senior Member   Lucky Tran Join Date: Apr 2011 Location: Orlando, FL USA Posts: 1,982 Rep Power: 26 Try posting in the UDF forum?

 May 5, 2012, 17:32 #3 Member   Join Date: Nov 2011 Location: Czech Republic Posts: 95 Rep Power: 8 The mentioned UDF is just setting velocity and turbulent quantities in the fluid domain according to radius Code: `r =x[1];` (it is asymmetrical simulation). More precisely the UDF is setting 3 components of velocity (u, v, w), turbulence kinetic energy (k) and rate of dissipation of the turbulence kinetic energy (epsilon). The coefficients in the polynomials (defined constants) were obtained from experimental data, so I am not sure, if it is exactly what you want. You might want to use MRF method instead to simulate impeller motion without need of experimental data.

 May 6, 2012, 20:59 Thanks #4 New Member   Ijaz Join Date: Dec 2011 Location: Singapore Posts: 17 Rep Power: 8 Thanks for the explanation...does the radius pertain to radius of impeller? I have an impeller rotating with speed "a" asymmetrically at a distance of 0.16 m from the centre and also need to rotate the tank with speed "b". Could you give me any which way I could do it? is udf necessary?

May 8, 2012, 04:24
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No, it pertains to radius of cylindrical domain. Basically they are setting flow properties by this UDF.

For your simulation, if you don't have an experimental data, which you would like to use, you will have to use a different approach. For example the MRF method comes to my mind (assuming that you want to do steady state simulation). Basically you will have to divide your domain into two subdomains and set demanded angular velocities in them.

Last edited by Sixkillers; May 8, 2012 at 05:18.

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