Estimation of the surface stress from the streamwise pressure gradient: The Kármán Integral Momentum Equation revisited.

A method is developed to estimate the stress at the surface in a portable wind tunnel for wind erosion studies. The boundary layer height and the pressure gradient are used in a simple expression from the Kármán Integral Momentum Equation. Values of friction velocityu_* are within 10% of experimental values obtained through correlation techniques, including measurements of differential pressures with the Murdoch Turbulence Probe MTP and the X-wire, hot-wire anemometer XWA. Wind velocity and stress profiles reveal logarithmic trends and a ‘constant stress layer’ near the surface in the DAWA portable wind tunnel. Realignment of the statistics with the mean wind is essential. [ABSTRACT FROM AUTHOR]