Use of the Piv Method for Investigation of Motion Near a Cylinder in Transverse Flow

Abstract

Turbulent flow past a cylinder in a wind tunnel has been investigated experimentally. Averaged velocity fields near the cylinder have been obtained with the optical PIV method and comparative characteristics have been given for noncavitation and cavitation regimes. From the vector patterns of the averaged velocity fields, the author has determined the angles of separation of the boundary layer from the cylinder surface in the considered regimes of flow. It has been shown that cavitation causes the vortex zone behind the cylinder to increase, the separation angles to displace upstream, and the hydraulic resistance to grow. A comparative calculation of the separation angles and the coefficients of hydraulic resistance of cylinders manufactured from different materials has been given. It has been shown that the vortex zone of a Teflon cylinder in flow having a hydrophobic surface differs from the vortex zone of a steel cylinder, particularly for the cavitation regime in which the angles of separation, especially from the upper part, decrease appreciably and the resistance grows.