Experimental Study of Effects of Coriolis Force on Flow in a Rotating Deffuser

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To investigate the coupled effects of secondary flow, stability ( or instability ) due to Coriolis force, and adverse pressure gradient on the flow in a rotating diffuser of low aspect ratio, pressure, time-mean and fluctuating velocity components were measured. Conclusions reached as a result of present experimental study may be summarized as follows :(1) As increasing angular velocity, the boundary-layr development is promoted on the suction side and is suppressed on the pressure side due to thje secondary flows arising in the top and bottom wall boundary layrs. Eventually, the fully developed and retarded boundary layr separates only from the suction side wall due to the coupled effects of adverse pressure gradient, secondary flow and stability, while never separates from the pressure side due to the coupled effects of secondary flow and instability, but the secondary flow effect may be stronger than the instability effect,(2) Once the oncoming flow is separated from the suction side wall, the separated flow pattern is steady due to the combined effects of secondary flow and stability. The change ofg the angular velocity has little ro no effect on the mean velocity and turbulence intensity profiles at the diffuser mid-height. The flow is divided approximately into two regions, a through-flow ( jet ) on the pressure side and a separated flow ( wake ) on the suction side. The separated flow region with reverse flow is strabilized substantially,(3) In the shear flow region between the reverse flow and the through-flow, the turbulence intensity decreases with increasing the angular velocity at the same included angle because the production of turbulent shear stress is suppressed due to the stabilizing effect.