Doctoral seminar

Supersonic Combustor Fuel Injection Simulations Using a Hybrid RANS/LES Approach:
The flow inside the combustion chamber of a supersonic combustion ramjet (scramjet) engine is challenging to simulate. The mixing process is highly unsteady, with regions of both attached and separated flow, as well as shock interactions. These flow features make it difficult to obtain accurate solutions with Reynolds-Averaged Navier-Stokes (RANS) solvers. Our approach is to use a hybrid RANS and large eddy simulation (LES) turbulence model. The LES portion of the model is used to resolve the large-scale unsteady features of the flow in regions that are the most challenging for RANS: where mixing and combustion occurs, and where the flow is massively separated. The RANS portion of the model is used in regions where mixing is not occurring and the flow is attached. RANS is also used as a wall model for LES regions. Using the RANS portion of the model in this way allows for realistic Reynolds numbers to be simulated on reasonably sized grids. The hybrid RANS/LES model is used in the US3D flow solver, which has an unstructured grid framework and fully implicit time integration. These are enabling features for the simulations. Before confidence can be placed in the results of any simulation, a thorough validation against experimental data must be performed. This talk presents some results from this ongoing validation process. Simulations focus on non-reacting injection through circular injector ports in various geometric configurations and at a variety of flow conditions. Simulations are compared to measurements of mean wall pressure, mean velocity and turbulence quantities from LDV, instantaneous flow visualizations, as well as mean mixing measurements from PLIF and vibrational Raman scattering. The results compare well with experiment, indicating that the methods employed are capable of accurately simulating the mixing process this complex flow. The methods are also efficient, making their use promising for the analysis and design of actual scramjet combustor sections.

Speaker: David Peterson, University of Minnesota

Date: Monday, May 26, 2010

Time: 16:15

Location: Seminar Room 102, Schinkelstr. 2a, German Research School for Simulation Sciences, 52062 Aachen