EXPERIMENTAL STUDY ON THE EFFECT OF SOLID PARTICLES ON RIBLET-PLATE TURBULENT BOUNDARY LAYER

The particle image velocimetry (PIV) is used to conduct experimental research in the solid-liquid two-phase wall turbulent boundary layer in smooth and riblet surface. The streamwise-normal two-dimensional velocity field information of clean water (as single phase) and water with polystyrene particles which diameter is 155 μm was collected, and the turbulence statistics such as the average velocity profile, turbulence intensity and Reynolds shear stress of the smooth and riblet surface are compared in particle phase and clean water to analyze the behavior of fluid in different wall boundary layers. Coherent structures were detected by quadrant splitting method and the concept of local average velocity structure functions of the streamwise is utilized to extract the sweep and eject motions under different operating conditions. Under the different wall conditions, the dimensionless fluid velocity with particles was greater than that of clean water, the Reynolds stress in the logarithmic law region is decreased and the turbulence intensity is receded. The addition of particles reduces the drag reduction near the riblet surface with different velocities, but the drag reduction effect of particles acting on smooth wall surface is not obvious. The number of coherent structures is increased with the addition of particles and the normal fluctuating velocity is decreased. The number of coherent structures is increased near the riblet surface, the normal fluctuating velocity is increased in a higher free flow velocity and the normal fluctuating velocity is decreased in a lower free flow velocity. This indicates that the large vortices can be broken into more vortices under different drag reduction conditions, and this effect is increased by the addition of particles.