Yorinobu Toya

An Experiment on a Taylor Vortex Flow in a Gap with a Small Aspect Ratio : Bifurcation of Flows in a Symmetric System

SummaryBoth Taylor vortex flows in a symmetric or asymmetric system exhibit various patterns (cell modes). They can be classified by the process of cell formation, the number of cells and the direction of flow for the cell, into primary modes or secondary modes, and normal modes or anomalous modes. Following the previous report in which flows in a symmetric end condition were classified, in the present work, for flows in an asymmetric end condition, the Reynolds number at which a secondary mode bifurcates into another mode is experimentally investigated, and the bifurcation of the Taylor vortex flows in an asymmetric system when the Reynolds number is gradually decreased is presented in a bifurcation diagram.

Transition of Free-Surface Flow Modes in Taylor-Couette System

This paper presents our numerical and experimental results of the bifurcation found in Taylor-Couette system with a free surface. The lengths of the two concentric cylinders are finite and their axes are parallel to the direction of the gravitational force. When the end walls of the cylinders are fixed and stationary, numerical and experimental studies have shown that the flow has multiple patterns depending on the cylinder lengths and the Reynolds numbers. Experimental studies on flows with free surfaces also gave various flow modes. Our result shows that the measured and predicted time-dependent displacements of the free surface are in favorable agreement. In case of the cylinder length comparable with the gap width between the cylinders, gradual accelerations of the inner cylinder bring the normal mode flows with one, three and five toroidal vortices. The exchanges of stabilities between these flow modes are summarized in a phase diagram.

Numerical analysis of the bifurcation to wavy Taylor vortex flow with a small aspect ratio

We present a numerical analysis of the bifurcation to wavy Taylor vortex flow from Taylor vortex flow with a small aspect ratio and compare the experimental results for the instability of the Taylor vortex flow and for the critical Reynolds number to the wavy Taylor vortex flow. In this work, flow patterns and spatially averaged energy and spatially averaged enstrophy are shown by 3-dimensional numerical analysis. Comparison of the critical Reynolds numbers between numerical results and experimental results shows broad agreement about qualitative variation.

Existence of Extra Vortex and Twin Vortex of Anomalous Mode in Taylor Vortex Flow with a Small Aspect Ratio.

This experimental work on Taylor vortex flow in a gap with a small aspect ratio is concerned with two extra vortices and a twin vortex system depending on an anomalous cell of the anomalous mode. Extra vortices are smaller than other vortices such as defined cells, and stay at the corners of the inner rotating cylinder and the outer stationary one and the end plate with anomalous cells at any Reynolds number and aspect ratio. For one-cell flow (anomalous one-cell mode) in a symmetric system, an outer extra vortex develops and grows to the same size as the main cell, only in a certain range of aspect ratio of less than one. A twin vortex is observed to form when two vortices line up in the direction of the radius. On the end plate there are three flow fields; two are extra vortex flows and the other is the main cell flow. It appears that the flow direction of the anomalous cell is from the inner cylinder to the outer one, opposite to the flow direction of the normal cell.