Simultaneous measurements of freestream disturbances, boundary layer instabilities, and transition location on sharp and blunt cones in hypersonic flow

Conference item

Boundary layer instabilities and transition to turbulence on a 7-degree half-angle cone with varying nose-tip radii in Mach 6 and 7 flow are investigated using a combination of surface heat transfer measurements, surface pressure measurements, and high speed schlieren images. The experiments are performed at unit-Reynolds numbers ranging from [22-44]*10^6/m in University of Oxford’s High-Density Tunnel (HDT). The transition Reynolds number, Re_{X_T}, increases with increasing nose tip Reynolds number, Re_{R_N}, for Re_{R_N}<10^5. In this range, evidence of second-mode wave instabilities are observed in both schlieren images and surface pressure measurements. For 10^5 < Re_{R_N} < 4*10^5, Re_{X_T} remains constant and coherent streaks above the boundary layer are observed with schlieren imaging. Images of the interaction of these features with a boundary layer breaking down to a fully turbulent state are presented. The freestream disturbance environment is also varied through existence of several steady state plateaus created by the natural operation of the facility, and characterised with multi-point focused laser differential interferometry (FLDI). Re_{X_T} increases by 10-60% with increasing plateau number which is independent of Re_{R_N}. Variation in freestream fluctuation amplitude with frequency and Reynolds number are in agreement with previous studies while variation with plateau is not. The discrepancy is explained by receptivity functions which are sensitive to the inclination angle of disturbances. A method for measuring the inclination angle using correlated FLDI signals is presented and reveals a consistent trend with plateau number. The trend is physically explained by changes in the relative contribution of entropic and acoustic modes with time.

Authors: Ceruzzi, AP; Le Page, LM; Kerth, P; Williams, BAO; McGilvray, M

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Institute of Aeronautics and Astronautics
• Host title: AIAA SCITECH 2024 Forum
• Volume: 2024
• Pages: 1-22
• Article number: 2187
• Publication date: 2024-01-04
• Acceptance date: 2023-11-02
• Event title: AIAA SCITECH 2024 Forum
• Event location: Orlando, Florida, USA
• Event website: https://www.aiaa.org/events-learning/event/2024/01/08/default-calendar/2024-aiaa-science-and-technology-forum-and-exposition-(aiaa-scitech-forum)
• Event start date: 2024-01-08
• Event end date: 2024-01-12
• DOI: 10.2514/6.2024-2187
• EISBN: 9781624107115
• Language: English