Self-induced flow in a stepped rotating tube

Self-induced flow occurs when a tube, open at one end and sealed at the other, is rotated about its central axis: fluid flows along the axis from the open end toward the sealed end and returns in a layer adjacent to the inner surface of the tube. This mechanism, which can occur under isothermal or nonisothermal conditions, is believed to be responsible for the so-called 'hot-poker effect' that was observed during anti-icing tests on the nose bullet of an aeroengine. This paper describes a combined theoretical and experimental study of self-induced flow. It is shown that, for the length-to-diameter (L/D) ratios and rotational Reynolds numbers associated with the anti-icing tubes of aeroengines, the laminar flow near the sealed end of the tube is similar to that of the so-called free disk. Swirl in the air outside the open end reduces the self-induced flow, but flow can reach the sealed end of a stepped tube which has either a sudden contraction or a sudden enlargement.