Direct Determination of Intermittency Distribution with Fast-Response Temperature-Sensitive Paint

Abstract

The focus of this work is the direct determination of intermittency with the help of a Ru(phen)-based fast response temperature-sensitive paint (iTSP) for a high Reynolds number flow and the comparison with surface temperature distribution, average heat-flux and standard deviation of surface temperature σT that are often used to determine the transition location. The studies have been conducted in the low-turbulence (Tupu ~ 0.06 %) Cryogenic Ludwieg-Tube Goettingen (KRG) at a large chord Reynolds numbers (7.5 Million) and Mach number 0.8 with an angle-of-attack (AoA) of -2.1° (favourable pressure gradient). The main part of the model is instrumented with iTSP on the port side and hot-films on the starboard side (18 hot-films staggered at 35°). The iTSP observation area (32 x 55 mm²) is recorded at a frequency of 20 kHz. With the known thermal properties of the model and iTSP coating and the accurate timeresolved surface temperature measurement, the instantaneous heat-flux distribution can be determined. This in turn is then used to distinguish laminar and turbulent boundary layers at a given time and surface location and with it the intermittency distribution.