Influence of external geometrical modifications on the flow behaviour of a rotor–stator system: numerical and experimental investigation

Abstract: Earlier experimental and numerical studies have shown the sensitiveness of flow behaviour inside a rotating disc system due to peripheral geometry adjustments. In an opened annular cavity without any superimposed flow, velocity, and pressure levels are strongly affected by a very weak variation of the λ parameter, based on the radii difference between the two discs. The aim of the present work is to improve knowledge of the influence of this parameter with the help of numerical simulations performed with the CFD Fluent code and experimental results carried out by hot-wire anemometry and three-holes pressure probe. At the periphery, centrifugal effects of the rotor drive the fluid out of the cavity, imposing flow compensation on the stator side. Peripheral geometry influences the source of the inlet fluid and the inlet/outlet area ratio: these are two major elements conditioning the pre-swirl of the fluid at the periphery, which seems to control the flow behaviour inside the cavity. One major consequence is that the well-known Batchelor type flow is not always encountered in the inner part of the cavity: it may gradually appear over a range of the λ parameter specific to geometrical conditions of the inlet.