Accurate prediction of the turbulent two-phase flowfield is of great importance to the correct estimation of performance of solid rocket motors (SRM) and slag accumulation rate. An analysis is hampered by the complex flow features involving complex geometry, turbulence with mass injection, recirculation regions, a wide range of Mach numbers, two-phase flow phenomena, heterogeneous combustion, and uncertainties in particle density and particle size distribution. Turbulence plays an important role in determining the wave properties through the damping effect of turbulence-induced eddy viscosity on vortical motion. Turbulence modeling becomes necessary for the evaluation of heat transfer and related phenomena (e.g. erosive burning). The interactions between organized oscillatory motions and turbulent fluctuations give rise to additional mechanisms of energy production, transfer and dissipation of wave modes. The difficulty in simulation of turbulence comes from the fact the transition is always inside the SRM, since the velocity at the head-end is equal to zero.
Jet injection into a supersonic nozzle flow is a challenging fluid dynamics problem in the field of aerospace engineering which has applications as part of a rocket thrust vector control system for noise control in cavities and fuel injection in scramjet combustion chambers. Several experimental and theoretical/numerical works have been conducted to explore this flow; however, there is a dearth of literature detailing the instantaneous flow which is vital to improve the efficiency of the mixing of fluids.
A numerical analysis of the internal flow is performed to improve the current understanding and modelling capabilities of the complex flow characteristics encountered in combustion chambers of SRMs in presence of transverse jet injection.
The flow is simulated using large-eddy simulation (LES) and solution of Reynolds-averaged Navier-Stokes (RANS) equations. Flow solution is provided using cell-centered finite volume formulation of the unsteady 3D compressible Navier-Stokes equations on dynamic unstructured meshes. Governing equations are solved by the three-step or fifth-step Runge-Kutta time marching scheme. Piecewise parabolic method and Chakravarthy-Osher scheme are applied to inviscid fluxes, and central difference scheme of the 2nd order is applied to viscous fluxes. Preconditioning block-Jacoby technique in conjunction with implicit dual time-stepping integration method is employed to stabilize numerical calculations and speed up convergence.
This study focuses on the averaged and instantaneous flow features including vortex structures downstream of the jet injection, along with the jet penetration, jet mixing, pressure distributions, turbulent kinetic energy, and Reynolds stresses in the downstream flow. It demonstrates that Kelvin-Helmholtz type instabilities in the upper jet shear layer are primarily responsible for mixing of the two fluids. Dynamics of control valve and its influence on flow structure is taken into account. Dependence of forces acting on nozzle walls on parameters of the problem and shock wave structure forming as a result of interaction of injected jet with supersonic nozzle flow are studied. The results are compared to available experimental data.
