Research on characteristics of turbulence kinetic energy in boundary layer over riblet surfaces

By performing a number of experiments on the turbulence kinetic energy of smooth plate surfaces and different V-riblet surfaces in various sizes at different wind velocities, the distributing rule of the turbulence kinetic energy over the riblet surfaces in the boundary layer is acquired. The experiments are carried out in a self-made special small-size wind tunnel. The flow field is tested with a TSI-IFA300 hot wire anemometer. The test models, which are made of organic glass, are so placed as to make sure the riblets are streamwise. In the calculation of the virtual origin and wall friction velocity of the riblet surfaces, a modified method is adopted, which can obtain virtual origin and wall friction velocity together by the least-squares fitting method based on the Spalding formula in the turbulent boundary layer. Ultimate results show that the existence of the riblets mainly change the near-wall flow field, and the turbulence kinetic energy in the viscous sublayer of the riblet surface boundary layer is increased, while the turbulence kinetic energy in the buffer zone of the riblet surface boundary layer is reduced dramatically, with the greatest relative reduction quantity of above 10%. This indirectly proves that the drag reduction mechanism of riblet surfaces based on the "secondary vortex" theory is reasonable.