The cavitating Taylor-Couette flow

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This work presents an investigation of a new phenomenon of the Taylor-Couette flow: the onset of Taylor vortices in a cavitating fluid. This particular form of the Taylor-Couette flow develops if the shear flow between a rotating inner and a fixed outer cylinder approaches the critical Taylor number and the vapor pressure of the fluid simultaneously. This process is achieved by increasing the rotational speed of the inner cylinder, which causes an increase of the radial pressure gradient inside the laminar flow. The fully developed Taylor vortex flow is characterized by a pressure distribution in the azimuthal plane showing a local minimum adjacent to the wall of the inner cylinder between a pair of vortices that form a radial flow towards the outer cylinder. Thence, cavitation occurs simultaneously if the local pressure minimum drops below the vapor pressure of the fluid. This transition from a two-dimensional (Couette) into a three-dimensional (Taylor) flow triggered the idea to apply a newly developed unsteady 2-phase 3D-computational fluid dynamics code by computing the generation of vapor that is coinciding with the formation of Taylor vortices at the critical Taylor number. Whereas the results of a numerical simulation prove the existence of toroidal vapor caused by cavitation, the experimental validation demands additionally the development of a special fluid. Thus, the present work describes this specifically tailored fluid, which not only fulfills Taylor and pressure analogy but also features a favorable refractive index and a chemical suitability for the task.