An Reτ dependent spatial resolution correction scheme for hotwire measurements in developing zero-pressure-gradient turbulent boundary layers

Constant temperature anemometry remains the preferred method for the measurement of key quantities in turbulent boundary layer investigations. One main challenge is the finite length of the hotwire sensor often being larger than the smallest eddies present in the flow. This leads to spatial averaging along the sensor and the result is an underestimated fluctuation intensity profile, which needs to be corrected. Several correction schemes have been suggested, and most schemes try to correct only for the dimensionless sensor length, L+ within a constant friction Reynolds number, Reτ. Our aim is to develop a correction scheme that takes both parameters into account; L+, and Reτ , to achieve a more global representation. Experiments have been performed over a developing zero-pressure-gradient turbulent boundary layer, with Reτ values ranging from 526 to 1230 and L+ values ranging from 66 to 85. The hot length of the sensor was used in the calculation of L+. We propose a novel and simple magnitude function, M(L+ ,Reτ ) while using the wall-normal function, f(y+), proposed by Smits. The new correction scheme is also compared with DNS results of Schlatter and Örlü at Reτ , with L+ values ranging from 5.4 to 87. The results indicate that the new magnitude function, M(L+ ,Reτ ) has a better performance on both experimental and DNS results, and for a range of L+, and Reτ values.