Turbulence wall-shear stress sensor for the atmospheric surface layer

Abstract

A new sensor is described for measuring the fluctuating component of the wall-shear stress. in the atmospheric surface layer over relatively smooth uniform terrain. The sensor was tested at the Surface Layer Turbulence and Environmental Science Test (SLTEST) site on the western salt flats of Utah, giving the first ever direct measurements of this quantity in an atmospheric-scale flow. The device consists of a lightweight floating element whose position is detected using a spherical mirror which deflects a laser beam onto a duo-lateral position-sensing photodiode. The sensor has a frequency response of 25 Hz and a circular sensing area of 50 mm diameter, making it suitable for atmospheric-sca..