PIV measurement of turbulent flow in curved ducts with variable curvature convex wall

Abstract

The fully developed turbulent flow through 120° curved ducts with variable curvature convex wall is investigated using particle image velocimetry (PIV) over a range of Reynolds numbers from 2 × 104 to 1.4 × 105. The profile of the convex wall adopts the blade pattern of classic centrifugal pumps, namely, spiral line (SL) and involute line (IL). A new coordinate (so’R) with streamwise and curvature radial directions is introduced to adapt to the requirements of variable curvature. Based on coordinate transformation, the profiles of mean streamwise velocity (us) and centrifugal velocity (uR), positions of velocity extreme, vorticity, total shear stress and root mean square (rms) velocities (us’and uR’) under the new coordinate system (so’R) are analyzed to investigate the effects of variable curvature and Reynolds number. The results provide a useful reference to perform curvature correction of turbulence models and guide the design of fluid machinery with variable curvature flow channel.