Response of flush-mounted hot-wire and hot-film wall shear stress probes

Abstract

The present study continues the preliminary work of Khoo et al (1997) using the apparatus designed for generating a known near-wall fluctuating flow field to quantify the dynamic response of a flush-mounted hot-element wall shear stress gauge. Two different types of wall shear stress gauges were used in our experiment: a flush-mounted hot-wire in contact with the wall substrate and commercially-available quartz substrate hot-film gauges with different thickness of quartz coating. The flush-mounted hot-wire gauge was found to have a much higher dynamic response compared to the quartz substrate gauges although it is still lower than the marginally elevated hot-wire configuration. This may suggest the possible use of a marginally-elevated hot-wire as a wall shear stress gauge to ensure sufficient responsiveness for time-resolved wall shear stress measurements.