Flows Through Round Sudden Contractions

Abstract

Measurements of the mean axial and radial components of velocity, the r.m.s. of the corresponding fluctuations and the wall static pressure are reported for flows through round sudden axi- and asymmetric contractions with an area ratio of 2.5 and were obtained at a Reynolds number of 40 000 based on the bulk velocity in the upstream pipe. In the axisymmetric case, the main changes in the approach velocity profiles occurred within a distance of one-half diameter upstream of the contraction, and the velocity profiles suggested that the flow separates at the entrance to the smaller diameter pipe. The wall static pressures revealed the presence of a vena-contracta downstream of the contraction plane. In the asymmetric case, the velocity profiles were very three-dimensional but regained symmetry by 9.5 diameters from the contraction plane.