# Need info about totalPressure boundary condition

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 March 8, 2017, 12:30 Need info about totalPressure boundary condition #1 Member   Sheikh Ahmed Join Date: Dec 2015 Location: South Carolina, USA Posts: 88 Rep Power: 9 Dear foamers I am sure lots of you are using totalPressure boundary condition in your simulations. I am trying to use it as my outlet boundary condition for pressure since I have possibility of backflow and in that case, the totalPressure bc is numerically most stable one along with pressureInletOutletVelocity boundary for velocity. In the manual, it is mentioned that the data to specify with totalPressure is only p0, but I saw that there are a number of parameters speficied, e.g. gamma, phi, rho, U etc. Could anyone PLEASE tell me what values I have to specify along with totalPressure boundary condition?

 March 8, 2017, 13:56 dam breaking example #2 Member   Sheikh Ahmed Join Date: Dec 2015 Location: South Carolina, USA Posts: 88 Rep Power: 9 I used the parameters of the totalPressure from the top 'atmosphere' boundary of the dam breaking tutorial. But it always gives me diverged solution- 'floating point exception'. Can anyone please help me regarding the parameters to be specified for this totalPressure boundary??

 March 9, 2017, 06:23 #3 Member   Join Date: Sep 2014 Location: Germany Posts: 88 Rep Power: 10 Look here for settings: https://cpp.openfoam.org/v4/a02729.html In older versions of OF you had to specify more than just p0, the totalPressure BC was simplified.

 May 7, 2017, 17:49 #4 Member   sibo Join Date: Oct 2016 Location: Chicago Posts: 55 Rep Power: 8 Dear TobM, I have a question about the ganma in totalpressure Bc setting. I thought the value of gamma should be determined by the temperature of air not the mach number. but from the page you provided, for transonic flow the gamma is 1. Does that mean no matter what the initial condition is, as long as the flow is transonic, the gamma should be 1 in the totalpressure Bc? Also, it said for compressible subsonic flow, there is no need to input gamma, but when i delete the gamma for my subsonic flow case, there will be an error"gamma undefined". Could you help me with these questions? Thanks a lot!!!!!!!

 December 4, 2018, 22:23 #5 Senior Member   Jianrui Zeng Join Date: May 2018 Location: China Posts: 157 Rep Power: 6 I am also interested in the parameters in this boundary setting. Can you give some explains? Thank you very much.

 Tags backflow, totalpressure