
[Sponsors] 
April 17, 2014, 02:51 
Pressure parameter in paraview

#1 
New Member
Sachchit Vekaria
Join Date: Dec 2013
Posts: 16
Rep Power: 3 
In SU2 v3.0.0 in the paraview output file how the parameter 'pressure' has been calculated? When I calculate pressure from pressure coefficient it is coming out different than the parameter 'pressure'. Is it p/(rho*U^2) or something else?


April 18, 2014, 09:28 

#2  
Super Moderator
Francisco Palacios
Join Date: Jan 2013
Location: Stanford, CA
Posts: 304
Rep Power: 5 
Quote:
Formula to link pressure and Cp in surface_flow.csv? for more details, Best, Francisco 

April 19, 2014, 14:25 
Still some problem

#3 
New Member
Sachchit Vekaria
Join Date: Dec 2013
Posts: 16
Rep Power: 3 
Hi,
I have gone through the file but the formula seems to be the normal formula of Cp but the problem can be seen in the Images. Pressure is varying from 0.155 to 0.536 and Cp is varying from 1.23 to 1.29. Reference pressure is 101325 Pa. So ideally Cp should be ve by that formula. By the way Cp is coming out accurate, verified by other other software suites. But I can't understand the value of pressure. The formula of Pressure in that file is Pressure = Gamma_Minus_One*Density*(node[iPoint]>GetSolution(nDim+1)/Density0.5*Velocity2); Can you please explain this formula? Thanks in Advance. 

April 20, 2014, 08:42 

#4 
New Member
Join Date: Mar 2009
Posts: 13
Rep Power: 8 
Sachchit, i don't understand your problem. The formula in your post is simply equation of state for perfect gas:
Pressure = (Gamma  1)*Denstity*Internal_Energy. node[iPoint]>GetSolution(nDim+1) is the last conservative variable, which equals to Density*Total_Energy, Total_Energy = Internal_Energy  0.5*Velocity*Velocity, where Velocity is velocity magnitude (in your formula Velocity2 is squared velocity magnitude). So, node[iPoint]>GetSolution(nDim+1)/Density is total energy in specified point and (node[iPoint]>GetSolution(nDim+1)/Density0.5*Velocity2) is the internal energy. 

April 20, 2014, 09:04 

#5 
New Member
Sachchit Vekaria
Join Date: Dec 2013
Posts: 16
Rep Power: 3 
Hi Zef,
Thanks for explaining formula. I am confused with Velocity2 being ycomponent of velocity. I have found out later that Velocity2 is square of velocity. But can you please explain the images that I have attached earlier? I am not able to understand the numbers which are coming up in Pressure. The Coefficient of Pressure is coming accurate and pressure calculated from that coefficient is also giving good results. But the problem lies in the Pressure shown by default from the SU2. I just want to know what it is? Thanks Zef. 

April 20, 2014, 19:08 

#6  
Super Moderator
Francisco Palacios
Join Date: Jan 2013
Location: Stanford, CA
Posts: 304
Rep Power: 5 
Quote:
for example if REF_PRESSURE= 1.0 REF_TEMPERATURE= 1.0 REF_DENSITY= 1.0 then the code is running dimensional. You will find a description of the nondimensionalization in http://su2.stanford.edu/documents/SU2_AIAA_ASM2013.pdf Apart from that, the nondimensionalization is implemented in void CConfig::SetNondimensionalization(unsigned short val_nDim, unsigned short val_iZone) in config_structure.cpp. Best Regards, Francisco 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
static vs. total pressure  auf dem feld  FLUENT  14  February 3, 2015 06:08 
Calculation of the Governing Equations  Mihail  CFX  7  September 7, 2014 06:27 
Pulsatile pressure inlet with pressure outlet  a.lynchy  FLUENT  3  March 23, 2012 14:45 
liddriven cavity in matlab using BiCGStab  Don456  Main CFD Forum  1  January 19, 2012 16:00 
Pressure Outlet Guage pressure  Mohsin  FLUENT  34  January 12, 2012 06:45 