Resolvent based estimation of freestream disturbances from a hypersonic boundary layer*

Freestream noise generated by hypersonic turbulent boundary layers (TBL) on tunnel walls poses significant challenges for studies of transition over test objects in hypersonic experimental facilities. To mimic transition in freestream flight conditions, it is important to be able to predict, and account for, the freestream noise environment in such facilities. As a first step, in this study, we use resolvent-based estimation to predict the freestream noise environment generated by a hypersonic TBL over a flat-plate. We utilize a truncated set of planar power-spectral density measurements at a limited number of near-wall locations and show that we are able to qualitatively estimate the co-spectrum and spectrum of the one-point statistics in the freestream.

In addition to discussing the modeling methodology, we will discuss different considerations that can improve the estimation abilities of the model. Particularly, we will discuss the impact of a forcing model on the estimation and insights derived from the biglobal resolvent analysis.