Exercise

Introduction

The simulation setup of the turbulent, compressible flow through a exhaust gas recirculation system did give reasonable results. However, there are unresolved issues:

• Maximum and minimum temperature within the computational domain where unphysical.
• How does the mixing temperature as well as maximum temperature at the outlet change with varying exhaust gas flow rate?

In order to resolve these issues, additional simulations should be performed.

Tasks

1. Improved Discretization Schemes

Repeat the simulation with a limited gradient scheme to suppress unphysical temperature.

Subtasks

1. Duplicate the case folder and rename it to exhaust_gas_recirculation_gradient_scheme. This way the results of the first simulation do not get overwritten by this second simulation.
2. Within the exhaust_gas_recirculation_gradient_scheme case folder, remove all results folders (except 0), processor folder, and the postProcessing folder for a clean setup.
3. Set the default gradient scheme in fvSchemes in the system directory from Gauss linear to cellLimited Gauss linear 1.0.
4. Rerun the simulation in parallel:
   1. Decompose the case with decomposePar
   2. Run the simulation in parallel with mpirun -np 4 rhoPimpleFoam -parallel.
   3. Reconstruct the case with reconstructPar.
5. Analyse the simulation results with ParaView similar to the first simulation.

Questions

1. Did the limited gradient scheme remove the unphysical temperature?

2. Variation of Exhaust Gas Flow Rate

Repeat the simulations with different volumetric flow rates of the exhaust gas.

Subtasks

1. Duplicate the folder with the updated discretization schemes from Task 1 and rename it to exhaust_gas_recirculation_0.00125.
2. Within the exhaust_gas_recirculation_0 case folder, remove all results folders (except 0), processor folder, and the postProcessing folder for a clean setup.
3. Change the volumetric flow rate of the inlet_exhaust from 0.0025 to 0.00125.
4. Rerun the simulation in parallel:
   1. Decompose the case with decomposePar
   2. Run the simulation in parallel with mpirun -np 4 rhoPimpleFoam -parallel.
   3. Reconstruct the case with reconstructPar.
5. Analyse the simulation results with ParaView similar to the first simulation.
6. Repeat steps 1-5 with volumetric flow rates of 0.005 and 0.0075.

Questions

1. How does the maximum and average outlet temperature change with varying exhaust gas flow rate?