Author(s)

G. Ciaravino, L. Ciaravino & G. Pulci Doria

Abstract

With reference to the hydrodynamic working of a dropshaft fitted with a vortex inlet, there are still two problems that are open to debate: the actual distribution of velocities at the inlet and the pressure distribution along the radius in the first cross section of the shaft. The majority of researchers assume that the velocity distribution is both irrotational and axially symmetrical, although some forty years ago Viparelli experimentally showed that such an assumption is actually incorrect, hypothesizing that the flow is symmetrical but not irrotational. Moreover, the determination of pressure distribution in the different proposed theories remains a debatable issue, with some claiming that the distribution of pressure is equal to zero while others maintain it is positive. In the present paper, two series of experimental measurements concerning the above-mentioned problems are analyzed. A first series of experimental tests performed with a Laser Doppler Anemometer confirms a different velocity distribution hypothesis: irrotational but not entirely symmetrical. A second series of experimental tests deals with pressure measurements made in the vertical shaft inlet. Contrary to what has been hypothesized by other researchers, these measurements indicate negative pressure values. Keywords: dropshaft, vortex flow, mathematical model, experimental measurements, Laser-Doppler Anemometer. 1 Introduction Inflow in a dropshaft with vortex inlet is a rather complex phenomenon which still presents certain issues that have not been fully clarified. In spite of this such device is of great interest because of its undeniable technical importance. Its

Keywords

dropshaft, vortex flow, mathematical model, experimental measurements, Laser-Doppler Anemometer.