Speaker
Description
Europe’s access to space today relies primarily on the Ariane 5 family of heavy lift launchers and the Vega launcher for small payloads. The successful development of these launchers depends on finding solutions in the critical and challenging areas of propulsion and aero-thermodynamics, which are the key elements of any launch vehicle. In the past, aerodynamic and aero-thermodynamic development work was almost exclusively based on the use of engineering and empirical methods. Today the use of Computational Fluid Dynamics (CFD) has matured to the point where it can provide valuable physics based input where in the past empirical or engineering methods required to strongly simplifying the physics involved. In addition, experimental testing is extremely expensive, time consuming and often it is impossible to simulate the real flight conditions. As a result the data obtained from these experiments is only partially useful and approximate methods need to be used to extrapolate these data to real flight conditions.
This work has been carried out in the Hot-Plume project and concerns the after body flow of launch vehicles also called the base flow region. This flow is characterized by large regions of unsteady separated flow induced by the abrupt changes in geometry of the vehicle. In this region hot gases from the nozzle exit mix with the cold flow coming around the launch vehicle leading to very complex aerodynamic phenomena which today are only poorly understood. As a result there exists a large area of uncertainty in launch vehicle design.
The NSMB solver developed by CFE-Engineering and University of Strasbourg can simulate turbulent hypersonic flow with chemical equilibrium and non-equilibrium modelling. Particle tracking coupled with radiation modelling has been implemented and validated on the VEGA launcher and applied to the simulation of a Solid Rocket Motor which was experimented at Vertical Test Section (VMK) of the DLR in Cologne. The coflow and the solid rocket motor injection plane were modelled using a total pressure and total temperature injection boundary condition. Two injection conditions were considered and the chemical compositions for these conditions were obtained using the NASA Chemical Equilibrium program CEA. Only the most important combustion species were considered and modelled with an equilibrium chemistry. The mixing of the hot plume exhaust gases with the cold coflow was modelled using a passive scalar.
The calculations showed that after the nozzle throat the larger particles remain closer to the symmetry axis than the smaller particles and have lower velocities. Particle velocities on the symmetry axis just downstream of the nozzle exit were found to be slightly higher than the measured particle velocities. The ho tplume experiments showed large unsteady separated flow regions just downstream of the nozzle exit. These large unsteady flow regions makes detailed comparisons difficult. Calculations with radiation showed that the WSSG model gives the most realistic incident radiation.
Summary
CFD hypersonic simulation with particles and radiation are conducted on a Solid Rocket Motor and compared to experimental results performed at the Vertical Test Section (VMK) of the DLR in Cologne.
