The real tangential velocity of swirling flow in a circular pipe with diameter 300 mm and length 2000 mm was measured by using hot wire anemometry (HWA)

and analysis emphasized on turbulence intensity of the tangential velocity with the effect of oscillation of swirling flow. The real tangential velocity contained high frequency turbulent fluctuation velocity and low frequency fluctuation velocity. The real tangential velocity fluctuated obviously in the center region of the circular pipe

but fluctuated little near the wall of the circular pipe. By analyzing probability density of the real tangential velocity of swirling flow

fluctuation of the real tangential velocity changed greatly along the radial direction. This fluctuation was not only affected by turbulent fluctuation

but also by oscillation of swirling flow. Oscillation of swirling flow resulted in the phenomenon that turbulence intensity of the tangential velocity in the center region was higher than that near the wall.