Numerical Simulations of Supersonic Flows in an Aerospike using OpenFOAM

The main objective of this thesis is to implement a suitable open-source, density-based solver to simulate the high-speed compressible flows coming out of an aerospike rocket nozzle at different altitudes. The stability of the solver is demonstrated through an assessment of the calculated thrust and the degree of accuracy in the resolution of shocks and other critical compressibility effects. The method that will be used to design the contour has been devised by Angelino, this approach assumes a series of centred, isentropic expansion waves originating at the throat section of the aerospike nozzle and is based on the Prandtl-Meyer function. A recently developed coupled density-based solver on the foam-extend release of OpenFOAM, dbnsFoam (Jasak et al., 2014) has been chosen to simulate the flow field of interest. The solver is based on the HLLC Approximate Riemann Solver algorithm for the solution of the Euler Equations. Therefore, the solver is inviscid, but it represents a perfect starting point, especially to determine a proper set of boundary conditions. Additionally, there is also a viscous version of the solver, called dbnsTurbFoam, that will be useful for future works when viscosity and a model for turbulence will be introduced in the calculations. The HLLC Approximate Riemann Solver managed to obtain a solution for the presented cases. It turned out to be fairly precise in terms of accuracy of the produced thrust and in representing the characteristic waves and other flow features sought in the simulation. Nevertheless, the solver is slow and prone to instabilities when the shocks present in the flow are too strong. In fact, simulations with ambient pressures lower than 5000 Pa didn’t result in a converged solution.