Experimental Study of Hypersonic Wing/Fin Root Heating at Mach 8

Abstract

The junction between wings or fins and the body of supersonic flight vehicles generate complex vortical structures and shock impingements. In hypersonic flight this interaction can lead to high localised heating rates. While the general topology of this flow has been established, confidence in the heating rates predicted by computational simulation is not high. This study utilises a dense set of heat transfer measurements on a model consisting of a flat plate and a cylinder with an adjustable sweep angle to help better understand and quantify flow features and heating rates on a swept protruding wing in hypersonic flight. Tests were conducted in the T4 shock tunnel facility at the University of Queensland Centre for Hypersonics at conditions simulating Mach 8 flight at 30km altitude. The resulting data is intended to help better understand flow topologies over wing-root junctions at hypersonic speeds, where relatively little testing has been conducted. A series of tests were conducted at both “low” and “high” pressure conditions, representing approximate atmospheric conditions at Mach 8 (total enthalpy ca. 3 MJ/kg) and a higher pressure case respectively, the latter being tested with the intention of inducing turbulence and measuring the effects of higher enthalpy and total pressure (a flow trip was later designed to ensure transition of the upstream boundary layer). The present study succeeded in correlating heating rates to empirical equations in the flat plate region upstream of the interaction, where the flow could be modelled as a simple flat plate of known Reynolds number. Correlation to theory, where applicable, was good. The use of a trip successfully caused flow to consistently transition from laminar to turbulent. Schlieren images were used to successfully match measured heating peaks with observed shock impingements. The present work was able to demonstrate the effectiveness of a trip in triggering turbulence. It demonstrated a correlation between flat plate heating and sweep angle, as well as providing a profile of heating rates along the centreline of a wing protruding from a wing root. Schlieren images added further insight by demonstrating positive the relationship between recirculation region size and peak heating rates. Future work should focus on obtaining more reliable data for the scenarios studied herein, particularly on the wing, where peak heating is expected to significantly exceed heating rates observed on the flat plate.