Mean and turbulent characteristics of tip vortices generated by a slotted model blade

Abstract

This chapter explores evolutionary structure of tip vortices with a two-dimensional LDV system for a plain and slotted blade, respectively. To analyze the effect of slots that bypasses a part of the main stream into the tip face, velocity profiles, and vortex sizes, their displacements and turbulence intensities during one revolution of the rotor are measured by the phase averaging process. It is observed that the peak values of the swirl velocity components of the slotted blade are smaller than those of the plain blade while the core values of the axial velocity components of the slotted blade are considerably larger than those of the plain blade. It is also noted that the slotted rotor blade enlarges the core size and thus results in attenuating the vortex strength, compared with those of the plain blade at the same wake ages. Profile of turbulent intensity of swirl component demonstrates peaks inside the core boundary and exponential decay radially outward.