# obtaining total pressure at a patch

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 April 19, 2013, 12:57 obtaining total pressure at a patch #1 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,186 Rep Power: 16 which functionObjects can use to obtain p0 (average,min,max) at inlet or outlet in time folders?

 April 19, 2013, 13:45 #2 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,186 Rep Power: 16 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? Last edited by immortality; April 19, 2013 at 14:03.

 April 20, 2013, 07:56 #3 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,186 Rep Power: 16 is this a correct work? what about average temperature and velocity at a patch? can use "patchAveragePressure"? or its only for pressure?

 April 20, 2013, 14:52 #4 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,186 Rep Power: 16 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)

 April 24, 2013, 13:52 #5 Senior Member     Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,186 Rep Power: 16 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. namsivag likes this. __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

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