PIV measurement of secondary flow in curvilinear pipe flow of polymer solution

The secondary flow in a curvilinear pipe flow of Polyacrylamide (PAA) 0.1 wt% solution was investigated by the PIV measurement near the inlet region of a straight pipe downstream of the curvilinear pipe. The number of curves N was set at 1, 2 and 60. We observed three kinds of secondary flow patterns, i.e., the outward and inward secondary flows in the almost whole region of the cross section of the pipe, and the secondary flow in which the flow is almost zero near the center of the pipe and inward in the upper and lower regions. These secondary flow patterns were dependent on the streamwise location, Reynolds number, and N, unlike the Newtonian fluid.