Planar flow past multiple successive blades and wakes is studied for nearly aligned
configurations with normal non-symmetry inducing lift. The typical blade lies relatively
near the centreline of the oncoming wake from the preceding blade. The central
motion over a wide parameter range is in condensed periodic boundary layers and
wakes with fixed displacement, buried within surrounding incident shear flow. This is
accompanied, however, by streamwise jumps in the pressure, velocity and mass flux,
across the leading edge of each blade, a new and surprising feature which is supported
by the combination of incident shears and a solid surface and which is related to the
normal flow through the multi-blade system. The leading-edge jumps are required
in order to satisfy the equi-pressure condition at the trailing edge. Computational
results include separating flows and show the lift and drag, and these are followed by
a short-blade analysis which captures the main flow properties explicitly. The results
agree qualitatively with experiments and direct simulations for rotor blade flows. The
jump feature also extends for example to a single blade immersed in the relatively
large wake of an upstream blade.
Swirling Flow through a Curved Diffuser (Flow Properties and Vibration in Pipeline)