setFixedTempProfile function

[Etienne Espada]

Hello everyone,

I am coming back to regarding the setFixedTempProfile() which allows the user to fix a temprature profile for a 1D simulation (Sim1D class). In the latest version of cantera (and previous one) I saw lines 302 - 303 in StFLow.cpp the following comment : 

rsd[index(c_offset_U,j)] = (rho_u(x,j)

- m_rho[0]*0.3); // why 0.3?

I don't understand why there is a 0.3 indeed. This line concerns the fixed point temperature. To me at this point when the temperature is fixed, the residual should be 0 so instead of :(line 302-303)

               rsd[index(c_offset_U,j)] = (rho_u(x,j)- m_rho[0]*0.3); 

we should have had :

                rsd[index(c_offset_U,j)] = (T(x,j)- m_fixedtemp[x]);

 which is what is done above when energy ins't disabled : (line 300)

                rsd[index(c_offset_U,j)] = (T(x,j) - m_tfixed);

Why question is the following : why this expression ? I believe that the fixed point is useful for freeflow as it enables to have a fixed flame front in space and so that the flame speed becomes a eigen value of the problem (please correct me if I am wrong).

The context of my interogation is that I want to do a similar thing for another variable of the solution vector (The FixedTemperatureProfile allows to fix the temperature by desabling the energy equation and I want to do the same for the velocity for instance by desabling the continuity equation or I want to do the same by fixing the profile of some species)

Thanks in advance, 

Etienne ESPADA PhD