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June 14, 2014, 20:03 
How to run cold flow in reactingFoam?

#1 
New Member
Harshad Lalit
Join Date: May 2013
Posts: 26
Rep Power: 5 
Hello all,
I have just started using OpenFoam for my dissertation on jet flame calculations. I am trying to simulate axisymmetric cold flow in reactingFoam. I switched off chemistry and reactions in the "constants" folder to simulate cold flow. Is that the correct way to go about doing it ? Also even if I switch off my chemistry, i still have default product species H2O and CO2 as output files. Why is that? Would really appreciate any help. Thanks 

June 15, 2014, 07:39 

#2 
Senior Member
Bobi
Join Date: Oct 2012
Location: Chicago, Illinois
Posts: 306
Rep Power: 6 
Greetings Harshad
I really didn't get what is exactly your problem. You have switched off the combustion and want to get rid off CO2 and H2O species in results?? (why does it matter) I think you have used onestep reaction in your case i.e. sth like this: Code:
species ( O2 H2O CH4 CO2 N2 ); reactions { methaneReaction { type irreversibleArrheniusReaction; reaction "CH4 + 2O2 = CO2 + 2H2O"; A 5.2e16; beta 0; Ta 14906; } } Regards Bobi 

June 16, 2014, 00:31 

#3 
New Member
Harshad Lalit
Join Date: May 2013
Posts: 26
Rep Power: 5 
Thanks Bobi!, appreciate your help
I didnt check the CO2 and H2O species files. I was just confused about why they were output when I was solving a cold flow solution. Can you also let me know how is the perfect gas equation of state used in a combustion solver in OpenFoam? I am assuming that since reactingFoam is a compressible solver, rho would be obtained from the continuity, velocity from the momentum equations and pressure, temperature from a laplacian and the enthalpy respectively. How is the equation of state used then? 

June 16, 2014, 03:43 

#4 
Senior Member
Bobi
Join Date: Oct 2012
Location: Chicago, Illinois
Posts: 306
Rep Power: 6 
Greetings Harshad
There is a difference between rhoReactingFoam and reactingFoam solvers. In reactingFoam, rho equation is not solved (although it uses compressible LES subgrid scale models) and the density is computed from the equation of state. However, in rhoReactingFoam rho equation is solved. (take a look at their src solvers i.e. reactingFoam.C and rhoReactingFoam.C ) Regards Bobi 

August 6, 2014, 11:56 

#5  
Senior Member
Armin
Join Date: Feb 2011
Location: Helsinki, Finland
Posts: 156
Rep Power: 11 
Quote:
From what I see, in both solvers the actual equation is included in the source code (in the .C files, as well as in the respective pEqn.H files): Code:
#include "rhoEqn.H" Armin 

July 31, 2015, 09:07 
Why can't I see the velocity residuals in my log file?

#6 
Member
Lisandro Maders
Join Date: Feb 2013
Posts: 67
Rep Power: 5 
Hello,
I am running a simulation using reactingFoam. There is an inlet of fuel and an inlet of air. After running everything ok, I can't see the velocity residuals in my log file. Why? Code:
Courant Number mean: 0.0774694 max: 0.394132 deltaT = 0.00116279 Time = 1.5 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCG: Solving for O2, Initial residual = 9.8746e07, Final residual = 9.8746e07, No Iterations 0 DILUPBiCG: Solving for H2O, Initial residual = 9.79843e07, Final residual = 9.79843e07, No Iterations 0 DILUPBiCG: Solving for CH4, Initial residual = 5.35224e08, Final residual = 5.35224e08, No Iterations 0 DILUPBiCG: Solving for CO2, Initial residual = 9.79228e07, Final residual = 9.79228e07, No Iterations 0 DILUPBiCG: Solving for h, Initial residual = 9.8117e07, Final residual = 9.8117e07, No Iterations 0 min/max(T) = 300, 1960.5 DICPCG: Solving for p, Initial residual = 1.47541e06, Final residual = 8.87219e07, No Iterations 21 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 7.03266e08, global = 9.27209e10, cumulative = 1.08985e05 DICPCG: Solving for p, Initial residual = 1.90516e06, Final residual = 6.1582e07, No Iterations 1 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 7.03245e08, global = 9.37162e10, cumulative = 1.08994e05 ExecutionTime = 19.53 s ClockTime = 19 s Regards, Lisandro 

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