Experimental Investigation and Characterization of Turbulent Spots on a Wedge in a Hypersonic Boundary Layer

Abstract

The Boundary Layer Transition (BLT) is a serious problem for high-speed vehicles since a vehicle experiences a huge thermal load during a hypersonic flight. Especially, the thermal load becomes so significant that it may destroy the vehicle by altering and/or melting the surface structure in the BLT region. Therefore, it is essential to predict the location of BLT for designing hypersonic vehicles. BLT has been investigated for several decades. Previous experimental and theoretical investigations indicated that the merging of turbulent spots results in a fully developed turbulent boundary layer. Therefore, it is important to study the characteristics of turbulent spots for a better understanding and accurate prediction of BLT location. In this study, the boundary layer flow on a wedge model was investigated using pressure sensors, and turbulent spots were visualized by measuring the heat flux on the surface of a wedge model using a fast-response Temperature-Sensitive Paint (TSP). The frequency analysis may indicate the boundary layer flow was transitional. The global heat flux distribution derived by TSP measurements visualized turbulent spots propagating downstream. Based on the global heat flux distribution, the propagation velocity, the peak heat flux, the lateral spreading angle, the vertex angle, and the number of turbulent spots that appeared during test durations were obtained. Some of the results show good agreement with data available in the previous research, showing the ability of the TSP used in this study.