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*CFD

Keyword type: step

This procedure is used to perform a three-dimensional computational fluid dynamics (CFD) calculation.

There are four optional parameters: STEADY STATE, TIME RESET, TOTAL TIME AT START and COMPRESSIBLE.

The parameter STEADY STATE indicates that only the steady state should be calculated. If this parameter is absent, the calculation is assumed to be time dependent and a transient analysis is performed.

The initial time increment and time step period are interpreted mechanical time increment and mechanical time step. For each mechanical time increment a CFD calculation is performed consisting of several CFD time increments. Therefore, the initial CFD time increment cannot exceed the initial mechanical time increment. CFD time increments are usually much smaller than the mechanical time increments. The CFD calculation is performed up to the end of the mechanical time increment (if the calculation is transient) or up to steady state conditions (if the CFD calculation is a steady state calculation).

The parameter TIME RESET can be used to force the total time at the end of the present step to coincide with the total time at the end of the previous step. If there is no previous step the targeted total time is zero. If this parameter is absent the total time at the end of the present step is the total time at the end of the previous step plus the time period of the present step (2nd parameter underneath the *COUPLED TEMPERATURE-DISPLACEMENT keyword). Consequently, if the time at the end of the previous step is 10. and the present time period is 1., the total time at the end of the present step is 11. If the TIME RESET parameter is used, the total time at the beginning of the present step is 9. and at the end of the present step it will be 10. This is sometimes useful if transient coupled temperature-displacement calculations are preceded by a stationary heat transfer step to reach steady state conditions at the start of the transient coupled temperature-displacement calculations. Using the TIME RESET parameter in the stationary step (the first step in the calculation) will lead to a zero total time at the start of the subsequent instationary step.

The parameter TOTAL TIME AT START can be used to set the total time at the start of the step to a specific value.

Finally, the parameter COMPRESSIBLE specifies that the fluid is compressible. Default is incompressible.


First line:

Example: couette1

*CFD
.1,1.,,,0.01

defines a CFD step. The second line indicates that the initial time increment is .1, the total step time is 1 and the CFD time increment is 0.01.


Example files: thermomech.


next up previous contents
Next: *CFLUX Up: Input deck format Previous: *BUCKLE   Contents
guido dhondt 2016-03-08