ROTATING GAS-LIQUID FLOWS IN FINITE CYLINDERS - SENSITIVITY OF STANDING VORTICES TO END EFFECTS

The spiraling and straight gas-filled vortices formed by a rotating mi xture of a gas and a liquid flowing through a finite-length cylinder a re the subject of this paper. The working fluids considered are primar ily helium and water. The bubbly liquid enters and leaves the cyclone- type separator tangentially. A gas-core vortex forms due to the result ing swirling motion of the mixture and, ideally, most of the gas leave s through an opening centered in the inlet end-wall of the vertical cy linder. The sensitivity of the gas-core configurations to the relative angle between the tangential inlet and outlet (phi) and to the length -to-diameter ratio of the cylinder (L/D) are investigated experimental ly. Direct observations of the flow field are made using video and sti ll cameras. The various gas-core vortex configurations are classified in a stability diagram. Although, as many as eight different types of core patterns have been identified, they are of two basic modes: strai ght and helical-spiral, or combinations of these. However, the straigh t mode is neither perfectly straight nor axisymmetric; it contains som e non-uniformities. In an L/D-versus-phi plane, a linear ridge exists that is a sensitive stability line dividing the regimes of the straigh t and helical-spiral modes. The relationship between the two modes is examined, and the statistics of the wavelength and diameter of the hel ical spiral are given. A kinematic model is deducted and is used to ex plain the observed changes in the geometric parameters of the gas core .