# update initial conditions every 10 iterations

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 November 28, 2011, 07:45 update initial conditions every 10 iterations #1 Member   Join Date: Mar 2010 Posts: 42 Rep Power: 8 Hi all, I'm testing the whole operation curve of a hydraulic turbine, but the net head is highly dependent of the mass flow. I want to update the Total Pressure inlet condition every 10 timesteps, to match the new losses. The inlet condition would be something like this: Ptotal,in = 115000[Pa] - k*Q^2 where k is a constant for losses and Q the massflow. is it possible to do with cel expressions to update the boundary every 10 or more iterations? Thank you in advance, lindner

 November 28, 2011, 10:06 #2 Member   Join Date: Oct 2011 Posts: 32 Rep Power: 6 Yes, you can. However, you will have to do an expression for the current P rather than the total. Just set the input to an expression and define the expression for current pressure. CEL is quite easy to learn and there are quite a few specific examples in the tutorials provided with CFX, just watch the units. Hope this helps.

 November 28, 2011, 11:41 #3 Member   Join Date: Mar 2010 Posts: 42 Rep Power: 8 Hi Martin, Thanks for the quick answer! The cel expression is ok now, the only problem is to force the cfx to execute this expression every x timesteps (without fortran). Im reading about user functions and user subroutine to find something about it.

 November 28, 2011, 12:25 #4 Member   Join Date: Oct 2011 Posts: 32 Rep Power: 6 Great, a simple iterative function should sort that. A bit of imagination and you will have it.

 Tags cel, hydraulic turbine, iterative update

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