NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH GLENN RESEARCH CENTER
Secondary flow tests were conducted on an accelerating elbow with 90 deg. of turning designed for prescribed velocities that eliminate boundary-layer separation by avoiding local decelerations along the walls. Secondary flows were investigated for six boundary-layer thicknesses generated on the plane walls of the elbow by spoilers upstream of the elbow inlet. The passage vortex associated with secondary flows appears to be near the suction surface and away from the plane wall of the elbow at the exit and does not have appreciable span-wise motion as it moves downstream from the elbow exit. As the spoiler size increases, the boundary-layer form changes and a rather sudden difference in the secondary flow occurs, perhaps associated with the reduced importance of viscous effects in thick boundary layers. It is suggested that the strength of the secondary vortices is small and that the energy of secondary flows is small.