Ramp-Jet Scaling Effects on Aerospike Nozzle Flow Dynamics Using a High-Fidelity Navier-Stokes Solver

The effect of the relative scaling of the supersonic, wall-bounded jets on an aerospike nozzle ramp as compared to the aerospike nozzle’s base height is investigated using a high-fidelity Navier-Stokes solver. Three jet-height-to-spike-base ratios are studied: ℎi /ℎ = 0.2, 0.5, and 1.5. A sinuous flapping mode forms along the nozzle’s symmetry line in all cases. For the two smaller ratios, nonlinear mixing between the jets and centerline vortices yields a turbulent, vortex-dominated jet downstream of the aerospike nozzle. For the largest ratio, the jet cores separate the outer shear layers and the centerline vortices, preventing direct interactions between the two unstable flows and inhibiting mixing. A frequency analysis of the velocity and nozzle loading spectra suggests that the flapping mode feeds back onto the aerospike. A drastic decrease in the nozzle loading at ℎi /ℎ = 1.5 is observed, which is consistent with the onset of wake closure.