A STUDY OF TURBULENT FLOWS IN PIPE BENDS

An experimental and numerical study of turbulent air flow in circular section pipe bends was carried out in order to determine the influence of bend curvature on the flow. Two bends were used, with inside diameters of 43 mm and curvature ratios of 1:13.95 and 1:6.98. The corresponding Dean numbers were 9138 and 12919. The Reynolds number for both cases was 34132. Measurements of mean streamwise and r.m.s. velocities were made using laser Doppler anemometry. Numerical modelling was based on the commercial computer package 'PHOENICS', employing a k-epsilon turbulence model, standard wall functions and a three-dimensional elliptic solution procedure. The results showed that the secondary flow as more prevalent in the smaller bend. In view of certain simplifying assumptions in the theoretical model, encouraging agreement between experimental results and numerical predictions was obtained.