Experimental investigation of drag reduction for rotating disk surface with spiral grooves

An experimental platform for drag reduction of open rotating disk system has been constructed. Combined with the numerical study, the drag reduction effects of spiral grooves on rotating disk and the drag reduction mechanism of grooves have been investigated in detail. The results show that the maximum drag reduction ratio of 6.1% is obtained on rotating disk with the 7.4% disk surface area machined with spiral grooves. The main drag reduction mechanism in this experiment is that the pressure difference of the two sides in V-shaped groove creates a positive torque. Furthermore, the grooves have an effect of increasing the pressure difference between the inner and outer radius of rotating disk. Even though the grooves on the surface of disk have the same dimensionless height and width with that of the grooves on the surface of flat plate where drag reduction occurs, it increases significantly the shear stress on disk surface.