2D Flamelet Combustion

rcm1_animation.gif

This tutorial will cover the basics of setting up and running a non-premixed combustion problem using Loci-Stream's flamelet capabilities. The fuel and oxidizer is hydrogen and oxygen, respectively. Files for running the case yourself can be found here: LOCI-STREAM RUN FILES.

In this combustion scenario, a hydrogen stream and oxygen stream travel separately and mix in a combustion chamber. The flow is compressible, and the chemical reactions are handled by a flamelet table. This case has two modes that can be run: 1.) A steady-state RANS solution, and 2.) An unsteady detached eddy simulation(DES).


ComputatIOnal Domain

 
rcm1_flamelet_domain_diagram.png

The domain is axisymmetric.  

To see the Loci-Stream control file for the RANS case click HERE.
To see the Loci-Stream control file for the DES case click HERE.


Running the Code

Loci-Stream is an MPI based parallel code, so execution of the code is started with a call to mpirun. A template call is shown below where the terms in brackets(<>) are replaced by the specifics of your case.


mpirun -np <np> <path_to_stream_exec> --scheduleoutput -q solution <casename> <restart> > /dev/null >run.out 2>&1 &

For this example the call to run the RANS case is:
mpirun -np 8 /home/user/Loci-Stream/bin/stream --scheduleoutput -q solution case  > /dev/null >run.out 2>&1 &

Once the RANS solution is obtained, your can restart a DES solution from it using the following command:
mpirun -np 8 /home/user/Loci-Stream/bin/stream --scheduleoutput -q solution case 5000  > /dev/null >run5000.out 2>&1 &

*Note that here we used a consistent name between the RANS and DES cases. This is because the RANS solution is needed as an initial condition to start the DES case from, so the solution name for the RANS case should match the vars file name for the DES case to ensure consistency.


Results

The 'extract' utility is used to view the results of a simulation. The simulation is viewed at the 5000th time step. In the run directory extract the solution using: extract -vtk flamelet 5000 P v ZZ r tf . This will generate a solution directory with files in the Paraview VTK format which can be opened by Paraview. The case name is 'flamelet' and the timestep is '5000', and the variables to extract are the pressure(P) and velocity(v), mixture fraction(ZZ), density(r), flamelet table temperature(tf). Below is a contour plot of the temperature of the flow that was created using Paraview.

 

rans_temperature_field.png