Near-wall measurements of turbulence statistics with laser Doppler velocity profile and field sensors

We report on the near-wall turbulence statistics of the streamwise velocity in a fully developed channel flow. The measurement was conducted with two systems of laser Doppler velocity profile sensor at three different Reynolds numbers. Since the sensor provides both the velocity and position of individual tracer particles inside the measurement volume without being mechanically traversed, a high spatially resolved velocity measurement is achieved. The resulting turbulence statistics show a good agreement with available data of direct numerical simulations up to the fourth order moments. This demonstrates the velocity profile sensor to be one of the promising techniques for turbulent flow research with the advantage of a spatial resolution more than one order of magnitude higher than a conventional laser Doppler technique. The results qualifies the two profile sensors to build up a velocity field sensor, capable of measuring velocity distribution within a two-dimensional area without using a camera.