Numerical reconstruction of spalled particle trajectories in an arc-jet environment: Accounting for non-sphericity and back-tracking

Abstract

It is essential to evaluate the effect of spallation phenomena compared to other ablative mechanisms to determine its significance. Therefore, numerical reconstruction of particle trajectories is employed on experimental data to estimate the mass loss caused by spallation phenomena. A data-driven adaptive technique is inserted into the Lagrangian particle trajectory model to reconstruct the trajectories. The non-sphericity of the particles is accounted for by assuming a spherical control volume around them and thereby treating them as porous spheres. Porosity and permeability relationships as a function of control volume size are developed. A polynomial function of the Forchheimer number is developed using the relationships that, when multiplied with the spherical drag coefficient, yield the non-spherical drag coefficient value. Additionally, a backtracking methodology was developed to simulate the trajectories reverse in time until the particle touches the sample surface from where the ejection takes place. The results from the spallation experiments conducted at the NASA HyMETS facility over a wedge sample are considered. The extracted sizes and ejection parameters are presented. The results show that the sizes of most of the particles are around 10 microns that eject with a velocity of around 70 m/s and at an angle of around 35 degrees from the top of the wedge and -20 degrees from the bottom of the wedge.