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-   -   obtaining total pressure at a patch (http://www.cfd-online.com/Forums/openfoam-post-processing/116462-obtaining-total-pressure-patch.html)

immortality April 19, 2013 12:57

obtaining total pressure at a patch
 
which functionObjects can use to obtain p0 (average,min,max) at inlet or outlet in time folders?

immortality April 19, 2013 13:45

can I use this swak4FOAM function to calculate total p at each time step?how?
is this true that ahead of expression I write:
Code:

(p+.5*rho*sqr(U))*area/sum(area())
Code:

patchAveragePressure
    {
        type patchExpression;
        patches (
            wall
        );
        verbose true;
        expression "p*area()/sum(area())";
        accumulations (
            sum
        );
    }

I have too little time to triel and error.so all experiences are thanked.
my flow is compressible then how can account for cp if I write total pressure formula in isentropic formula?

immortality April 20, 2013 07:56

is this a correct work?
what about average temperature and velocity at a patch? can use "patchAveragePressure"? or its only for pressure?

immortality April 20, 2013 14:52

I can calculate total pressure without any need to Cp from the formula p0=p+1/2*rho*sqr(U) instead of isentropic relation.because the difference is so little.but how to do this?
add this in solver or can obtain it on inlet and outlet patches like p by (I prefer swak4Foam because it calculates values in each time step not only in writing times) postProcessing functions?
(sorry for repeating according to title)

immortality April 24, 2013 13:52

for anyone needs now or in future see here by search,it works well by this function:
Code:

total_pressure_right
      {
        type swakExpression;
        valueType patch;
        patchName right;
        accumulations (
            min
            max
            average
        );
        outputControl outputTime;
        expression "p+.5*rho*magSqr(U)";
        verbose true;
      }
    total_pressure_left
      {
        type swakExpression;
        valueType patch;
        patchName left;
        accumulations (
            min
            max
            average
        );
        outputControl outputTime;
        expression "p+.5*rho*magSqr(U)";
        verbose true;
      }

for calculating total pressure in two patches(right and left)
you should put like functions in controlDict.
also you should have installed swak4FOAM before.
it writes p0's in each time step in a separate folder and file and is nice.


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