Disturbance flow field analysis of particulate interaction with high speed boundary layers

The current work is a follow-up study on numerical simulations of particulate-induced transition for hypersonic boundary layer flows. While prior works have focused on obtaining an efficient and highly accurate simulation approach, in this work the main objective is to analyze the disturbance flow field during the particle impingement phase and its subsequent downstream evolution. Particulate impingement simulations were conducted employing the adaptive mesh refinement wave-packet tracking technique for a plate boundary-layer flow with a freestream Mach number of 5.35 and an isothermal wall at 300K. The disturbance flow field was analyzed by computing frequency spectra for wall pressure along streamwise direction and distributions of the different unsteady disturbance flow quantities at a position in the vicinity of the particle impingement location and further downstream where the mode S (for these conditions, commonly referred to as second mode) dominated wave-packet has been fully established. Biorthogonal decomposition was used to project the disturbance flow field onto normal modes and gain insight into the contributions from the different discrete and continuous modes to the disturbance flow field, and, in particular, to understand how the disturbance energy is translated into mode S.