TORSION EFFECT ON SECONDARY FLOW IN A HELICAL PIPE

A steady, fully developed laminar flow in a helical pipe with the Reynolds number less than 17/√ε{lunate} (ε{lunate} the curvature of the centerline of the helical pipe) is investigated by the perturbation method using a helical coordinate system. A second-order soluttion is fully presented. Results show that the torsion of the pipe has only a second-order effect, which causes the secondary vortices to turn and deform. However, this second-order effect still could be appreciable. In some cases of low Reynolds numbers, the dividing line between two vortices could be inclined so much that it is almost vertical. As the Reynolds number increases, two vortices of the secondary flow turn gradually from a left-right position to a commonly acknowledged above-below position. Comparison of this study with other works also shows that the controversy over research results pertaining to this subject could be clarified if agreement can be reached on some basic problems, such as exact definitions of fully developed flow and secondary flow in a helical pipe. © 1990.