Dynamic response of a hot-wire anemometer. Part II: A flush-mounted hot-wire and hot-film probes for wall shear stress measurements

The present study continues the work described in Part I of this paper in utilizing a specifically designed apparatus for generating a known near-wall fluctuating flow field for the purpose of quantifying the dynamic response of a flush-mounted hot-element wall shear stress gauge. Two different types of wall shear stress gauges were tested: a flush-mounted hot wire in contact with the wall substrate and commercially available quartz substrate hot-film gauges with different thicknesses of quartz coating. It is found that the flush-mounted hot-wire gauge has a much higher dynamic response than 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.