Laser Doppler anemometry measurements of laminar flow in helical pipes

Three-dimensional laser Doppler anemometry measurements are performed on developed laminar flow in three helical pipes. The experimental observations are compared to results of numerical calculations employing the fully elliptic numerical method. Good agreement is found between measured data and numerical results. The three helical pipes, with curvature ratios of 0.0734 and 0.1374 and non-dimensional pitches of 0.0793 and 0.193, are adopted to study the effects of curvature and pitch on laminar flow in the experimental approach. The range of Reynolds numbers is 500–2000 to ensure laminar flow in the entire helical pipe. Both the profile shapes of the normal components of the secondary flow and those of the axial flow along the same centerline present not only similar patterns but also similar change when pitch, curvature ratio, and Reynolds number vary. The results demonstrate comprehensive relationships between the axial flow and the secondary flow.