A Numerical Investigation of Clustered Spheres Separating in Mach 20 Flow

摘要

In the current study, the separation of equal-sized spheres from initial touching configurations at Mach 20 is examined through numerical simulations using a coupled CFD/FEA solver. Comparison of computational results with free-flight wind tunnel trajectories is conducted, and modest dependence on viscosity is observed, namely in the form of enhanced drag, although errors in lateral velocity are deemed low enough for computational results to be considered representative of actual sphere motions. A survey of two initially touching spheres at various alignment angles reveals a bimodal distribution of separation behaviors, with a stable region of persistent contact detected. From a different survey of four spheres arranged in the form of a tetrahedron, the final lateral velocity is correlated to initial polar positioning in the cluster, and a common assumption of purely radial spreading is supported by minimal changes in azimuthal positioning. Finally, a reduced parameterization of tetrahedron orientation allows for characterization of collective separation velocities and center-of-mass motion.