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Calculated values from earlier time steps

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Old   May 9, 2011, 08:44
Default Calculated values from earlier time steps
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Roland Rakos
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Dear CFX Users,

I have a simulation where the valve dynamic (valve chattering) is investigated. During the run of solver the valve velocity and the valve displacement are monitored in the full time range but in the CFX Pre I can use only the next expressions: valve displacement new/old and valve velocity new/old. I would like to define a contact model in end positiosn of valve, therefore I should use these values in the earlier time steps too (in t-1, t-2.....t-n timesteps).
How can I refer to these values with expression in earler time steps?

Thanks in advance;
Roland
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Old   May 9, 2011, 09:40
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You cannot access earlier values via expressions. You would need to use User Fortran routines and store the values you want in the MMS (Memory Management System).
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Old   May 9, 2011, 15:51
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Ugly Kid Joe
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Hey can you give some more details about the MMS ???? How can I use it to store values ???? Any tutorial has this MMS use ????
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Old   May 10, 2011, 09:07
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The routines needed to read and write from the MMS are all documented in the CFX documentation (MAKDAT, POKER, PEEKR, etc). I don't know of any tutorials though. It would be nice if CFX could add one that shows how to write data at one timestep then read it at a different timestep. Basically you need a Junction Box routine called at the start of the run to create and initialize a data area. Then you need another Junction Box called at the end of each timestep or coefficient loop to write data. Finally you need a User CEL Routine to read the data and do whatever is necessary (this could also be a Junction Box Routine, but usually a User CEL Routine is easier).
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