Effect of Mounting Position on Hot-Film Wall Shear Stress Sensors

摘要

Experimental data on the errors introduced in wall shear stress measurements when flush-mounted hot-film sensors are not properly positioned in relation to the test surface are presented. These data lead to the establishment of acceptable tolerance limits when positioning sensors in a calibration facility and also in the subsequent relocation of the sensor to where actual measurements are to be taken. Consideration is given not only to errors in mean values of wall shear stress, but also to RMS and instantaneous values. Results show that the hot-film sensor must be positioned within close tolerances for accurate shear stress measurements. Even though all testing was conducted on a 5 cm diameter pipe with fully developed turbulent flow, results are also applicable to other flows such as that over flat plates and in pipes of larger diameters.