Turbulent boundary layer testing technique over a solid surface under water

Based on the hot wire anemometry system, an experiment for turbulent boundary layer testing technique over a solid surface under water was conducted. Several feasible methods for improvement of testing were provided, such as realization of stable low speed flow, pressurization of water probe and the distance measurement between probe and solid surface, etc. A gravitational low speed flume system was designed, which could realize continuous water flow of 0 to 1.0 m/s, and the turbulent intensity was no more than 2.5%. The pressurization under 3m waterhead was obtained by using the probe pole and two-layer pressurization cushion. Based on the angle measurement of an optical theodolite, a length measurement method was acquired whose measuring error was less than 0.3%. In place of experimental measurement, the friction coefficient was calculated using the Prantl-Nikuradse experiential equation. The results indicate that this technique is capable of measuring turbulent boundary layer over a solid surface under water precisely.