Stokes flow through a twisted tube with square cross-section

Flow through a twisted tube with square cross-section and helical corrugations of arbitrary pitch is computed under conditions of Stokes flow. The governing equations are formulated in non-orthogonal helical coordinates in terms of a coupled system of linear differential equations describing the longitudinal and transverse flow over the tube cross-section. Numerical solutions are computed by a finite-difference method on a staggered grid incorporating pressure nodes and three sets of velocity nodes. The results illustrate the structure of the secondary flow developing over the tube cross-section and document the effect of the helical corrugations on the axial flow rate.