Rocket Jet Impinging on a Surface

Abstract: With the continuous growth of the space industry and the introduction of reusable rockets, the number of rocket launches is expected to increase significantly in the following years. During rocket launching, the engine exhaust impinges on the launch structure producing a complex flow field. The rocket jet induces large thermoaerodynamic and acoustic loads on the launch structures and the rocket. This thesis aims to study the physics and numerical considerations behind supersonic flows exhausted from rocket engines. First, the treatment of turbulent compressible flows through the Favre-averaged equations and the SST k-ω model are studied. Next, the numerical modeling of the problem, including solver and meshing theory is presented. Then, a model of a nozzle is explained along with how the performance is assessed to finally design a M=3 two-dimensional nozzle using the method of characteristics (MOC). The two-dimensional results are validated using Ansys Fluent, and the same geometry is used for the following axisymmetrical problems, which include the study of a free and impinging jet. The free jet problem serves to study how the nozzle behaves in a two-dimensional axisymmetric problem and to validate the impinging jet results. To obtain the results, RANS-based simulations of a cold, over-expanded jet with adiabatic walls are performed. Empirical formulas were used to verify the results. Lastly, the impinging jet problem is simulated using the same inlet boundary conditions as for the free jet. The impact that the plate distance to the exit of the nozzle has on the position of the shock waves when the jet impinges on the flat surface is assessed. Finally, an optimization of the shape of a wedge to minimize the maximum turbulence kinetic energy produced during steady-state simulation is carried out. As an appendix to the work, an aeroacoustic study of the impinging jet at 4De distance is presented. The results show the direction of propagation of the acoustic waves but due to the lack of acoustic quality of the mesh, the predicted sound pressure levels do not match the expected behavior.