Further experiments on the flow around a circular cylinder

Abstract

The intensity of friction on the surfaces of two cylinders of diameter 2·93 in. and 5·89 in. respectively have been determined from measurements of velocity taken at distances of about 0·0025 in. from the surface with small surface tubes. The sensitive range of Reynolds number (VoD/v) over which large changes in the flow characteristics are experienced was covered in the experiments on the larger cylinder. The character of the frictional distribution depends on the value of (VoD/v). At a relatively low value of (VoDv), the frictional intensity rises gradually to a maximum value and then rapidly falls to a zero value; whereas at a larger value of (VoD/v) within the sensitive range the frictional intensity after reaching its maximum value falls less abruptly to a minimum value, and then rises to a second maximum before the zero value is reached. A transition from laminar to turbulent flow occurs in the boundary layer where the frictional intensity is a minimum. The transition region is also clearly indicated by a marked inflexion in the curve of pressure distribution. The frictional distribution measured on the 5·89 in. cylinder is in reasonably close agreement with that predicted by modern boundary layer theory. Experiments have also been made to determine the effect of disturbances in the general stream on the characteristics of the flow.