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-   -   bad results in first totalPressure boundary condition iterations. (http://www.cfd-online.com/Forums/openfoam-solving/114667-bad-results-first-totalpressure-boundary-condition-iterations.html)

immortality March 15, 2013 06:01

bad results in first totalPressure boundary condition iterations.
 
at inlet in totalPressure boundary condition in first few iterations the velocity goes very high and pressure goes very low.
Its because of the formula use in the BC.
At first the velocity in domain is zero or very low.then this low velocity is used in totalPressure formula that leads to high pressure very close to total pressure value.by this high value of pressure first iteration is run and a very high velocity in domain is calculated.
At second iteration this very high(supersonic)value is used for p and a very low pressure is resulted that makes velocity lower than before.
this process continues(if not crashing at second stage because at supersonic speeds the velocity also must set from outside of the domain) until it reach a reasonable values after some iterations.
This process maybe acceptable in steady state problems but not in unsteady ones that results at each time step is important.
So alk thoughts and advices,remarks and hints are appreciated.
Thanks.


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