PIV in the vicinity of cork samples in particle-laden high-enthalpy flow

This research aims at analysing the particle-laden flow of the high-enthalpy wind tunnel L2K, which is used to characterize the impact of dust particles on the recession behaviour of thermal protection systems during Martian entry flight. In the tests, a slightly simplified Martian atmosphere (\({\text{97\% CO}}_{{\text{2}}}\) and \({\text{3\% N}}_{{\text{2}}}\)) is used. The high-enthalpy flow is loaded with micrometric particles of magnesium oxide. Several samples for stagnation point tests made of P50 cork are positioned inside the particle-laden flow. The particles’ mean velocity is measured at the stagnation point of the probe in a region of interest that includes the free stream and the shock layer, with a 2D-2C particle image velocimetry (PIV) system. Several particle flow features are observed, such as the particle’s steep velocity gradient across the shock, the shock layer, and a counter-flow that might be caused by outgassing and rebounded particles. Average particle velocities ranging from 0 to 2100 m/s are measured and compared with the numerical simulation of the wind tunnel’s particle-free flow. A discussion on particle agglomeration due to melting is reported, and the importance of considering this effect for the simulation of atmospheric entry in particle-laden atmospheres is highlighted. Particles are collected with double-sided copper tape on a cooled probe and analysed with a scanning electron microscope (SEM) and with energy-dispersive X-ray spectroscopy (EDX), to characterize their morphological change during their residence time in the wind tunnel flow.