Study on the Swirling Flow Field in a Rotating Cylinder : Numerical Analysis

The swirling flow field, including unsteady non-axisymmetric phenomena in a rotating hollow turbine shaft, is solved using computational fluid dynamics. The three-dimensional compressible Navier-Stokes equations are adopted and discretized by an implicit TVD scheme. No axisymmetric assumption is applied in order to find non-axisymmetric phenomena. The computational domain, therefore, is extended circumferentially to 360° and axisymmetric boundary conditions along the center axis are avoided. The existence of a rotating spiral vortex at the place where the swirling flow turns radially outward is shown. The spiral vortex rotates about the shaft center axis in the same direction as the tangential velocity of the main flow. Conversely, the vortex has a spiral form opposite the rotational direction of the fluid. The first non-axisymmetric mode of a single spiral vortex is transformed into the second mode of a double spiral vortex at a specific rotating speed of the shaft.