Control cylinder

Several experiments confirm strong influence of the control cylinder on wake stability. Global stability analysis finds the precise values of the critical Reynolds number.

The control cylinder diffuses the vorticity of the main one and changes the velocity gradients in the vicinity of the shear layer. The wake becomes much shorter than the one without control. The opposite shear layer is almost not effected. All these features of the wake are reflected in the stability properties of the flow.

Critical Reynolds number for different positioning of control cylinder, 16k to load enlargement

Effect of the control cylinder, 14k to load enlargement

The limited area of a very strong influence of the control cylinder is evident. It is possible to suppress the vortex street up to Re=79, in comparison to Re=46 for the cylinder without control. The suppression is accompanied with the decrease of the growth rate of the dominating global mode and reduction of the Strohal number of about 30% in comparison to the single cylinder flow.

Growth rate of the disturbance for control cylinder, 7k to load enlargement

Strouhal number for the flow with and without control, 11k to load enlargement

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Last modified: Wed Dec 15 10:46:55 CEST 1999