Roger Bouard

Experimental determination of the main features of the viscous flow in the wake of a circular cylinder in uniform translation. Part 1. Steady flow

A visualization method is used to obtain the main features of the hydrodynamic field for flow past a circular cylinder moving at a uniform speed in a direction perpendicular to its generating lines in a tank filled with a viscous liquid. Photographs are presented to show the particular fineness of the experimental technique. More especially, the closed wake and the velocity distribution behind the obstacle are investigated; the changes in the geometrical parameters describing the eddies with Reynolds number (5 Re

The early stage of development of the wake behind an impulsively started cylinder for 40 Re 4

The time development of the symmetrical standing zone of recirculation, which is formed in the early stage of the flow due to a circular cylinder impulsively set in motion perpendicular to its generators, has been studied using a flow visualization technique. The Reynolds numbers (based upon the diameter) range from 40 to 10 4 . Some new phenomena indicated in the flow patterns are revealed, and several different regimes are differentiated by a detailed analysis of the evolution of the main flow characteristics. A correlation with some theoretical results is established.

NUMERICAL SOLUTION OF THE EARLY STAGE OF THE UNSTEADY VISCOUS FLOW AROUND A CIRCULAR CYLINDER: A COMPARISON WITH EXPERIMENTAL VISUALIZATION AND MEASUREMENTS

Early stages of unsteady viscous flows around a circular cylinder at Reynolds numbers of 3000 and 9500 are analysed numerically by direct integration of the Navier-Stokes equations - a fourth-order finite-difference scheme is used for the resolution of the stream- function equation and a second-order one for the vorticity-transport equation. Evolution with time of the flow structure is studied in detail. Some new phenomena are revealed and confirmed by experiments. The influence of the grid systems and the downstream boundary conditions on the flow structure and the velocity profiles is discussed. The computed results were in good agreement qualitatively and quantitatively with experimental visualisation and measurements.