Abstract
Turbulent swirling flow in a straight pipe is investigated experimentally. It is extremely different from no-swirl pipe flow. Increasing its strength, the axial velocity decreases in the central domain of the pipe and flow reversal occurs. Although swirl decay and flow reversal mechanism have not been known enough yet, they are applied to the cyclone dust collector, and so on. Especially, earlier flow reversal and higher fluctuating velocity according to swirl strength affect its performance. The swirling angle in the vicinity of the pipe wall, Θsw, is employed for representing swirl strength instead of the conventional swirl number. Even on different initial swirl conditions, the flow similarities are ascertained on condition that Θsw are same. The displacement radius, Rd, is also proposed by the authors for estimating quantitatively the decrement of axial velocity in the central domain of the pipe according to the swirl motion. The flow reversal are observed on condition that Θsw, are greater than 22.5 degrees.
