VISCOUS FLOW IN HELICAL PIPES WITH NARROW ANNULAR CROSS SECTION
环形截面螺旋管道内的粘性流动

The Navier-Stokes equations are established for a nonorthognal coordinate-system based on tensor analysis. The zeroth-, the first- and the second-order (t = 0) analytic solutions are obtained for fully developed flow in helical pipes with narrow annular cross section using a perturbation method. It is found that there is a secondary flow on the annular cross section.