Advanced numerical Simulation for CAvitation: HPC, numerical and physical modelling, non equilibrium thermodynamics, large scale simulations – ASCA

Investigations on the cavitation highlighted the great difficulty to correlate numerous results relative to a reliable prediction of the cavitation, whether it is in the field of hydraulic machinery, space turbopumps, marine propellers, or combustion and formation of sprays in engines. The multi-physical approach of the mechanism of evaporation in the turbulent flows at high number of Reynolds remains a strong challenge both for numerical and experimental point of view. Indeed, considering the non linear interactions between the turbulent structures and the phenomenon of evaporation, it is nowadays very difficult to model the turbulence-cavitation interaction especially as the dynamics of the interfacial exchanges between the phases is extremely complex to understand. As regard to the numerical simulation, softwares under development have to take into account among others compressibility effects, the propagation of waves (expansion, shock), turbulence modelling (dilatational effects), phase transition modelling and thermal effects for thermosensitive fluids. The numerical integration of the considered PDEs is particularly stiff, due to the presence of source terms in the equations and in the very strong variations of the speed of sound in the mixture. Furthermore, as the physics imposes very low discretization steps, the costs of calculation become quickly prohibitive for unsteady 3D simulations. There is a strong need for massive parallelism and improvement of the numerical methods.

The goal of this project is to provide a new state of the art Numerical Methods and High Performance Computing (HPC) software for the numerical simulation of hydrodynamic cavitation. The project bridges a gap in this field, where reliable HPC numerical codes are nowadays absent due to the complexity of physics (two-phase flow, phase transition involving non equilibrium thermodynamics, strong compressibility effects, propagation of pressure and shock waves, interaction with turbulence at small scales). With the purpose to develop robust and reliable numerical software, based upon new mathematical methods and modern HPC strategies, this project will strongly impact studies of cavitation phenomenon .
This participation ensures the mandatory critical mass required to take up the following challenges:
(i) develop new high order numerical methods with firm mathematical background for flows involving strong shock, expansion waves and interfaces.
(ii) develop a shared HPC software that will materialize advances in both numerical methods and modelling for three-dimensional cavitation simulation.
(iii) apply these codes to numerically reproduce realistic physical configurations that are clearly difficult to simulate with presently existing software, because of the excessive time computing required by refined meshes and the high stifness of PDEs.