Measuring Technique of Wall Shear Stress with Hot Wire Probe

Abstract

A measuring technique of wall shear stress based on the hot wire method is presented. Measurements were carried out in a two-dimensional turbulent channel flow, where a single hot wire sensor was placed close to the wall. Output voltage of a constant temperature anemometer was recorded with varying diameter, distance from the wall and temperature of the wire as well as Reynolds number of the flow. The measured results were compared with the standard values of wall shear stress obtained from the streamwise pressure gradient. Applicability of conventional calibration methods were examined. Finally, the new calibration curve was proposed where the heat conduction error and the additional heat loss due to the wall proximity were cancelled out by subtracting the heat loss without flow at the same position. The universality of the curve was confirmed in that it was quite independent of diameter, height and temperature of the wire.