Vortex Shedding From Trailing Edge of Rotor Blade of Axial Flow Fan at Design Operating Condition

In the present paper the attention is focused on the vortex shedding from the trailing edge of the rotor blade at the design operating condition. We measured the relative velocity, the turbulence intensity, the spectrum of velocity fluctuation and the in-phase velocity fluctuation near the trailing edge along the blade span. The time variations of amplitude of velocity fluctuations from 1500 Hz to 1900 Hz in the wake of the suction and pressure side of the trailing edge are out of phase with each other simultaneously at the mid span region. Karman vortices were formed in the near wake of the trailing edge of rotor blade intermittently. As the distance between two measured locations along the blade span increased, the in-phase rate of two velocity fluctuations decreased. This rate became maximum value at the time lag of 0 s. As the measured radius of the moved sensor increased, the time lag decreased. The rotational axis of Karman vortex inclined for the trailing edge of rotor blade.