Effects of Free Stream Turbulence on the Viscous Flow Field of a Compressor Cascade.

Turbulence measurements have been made to document the flow through a linear compressor cascade with tip gap, with and without a turbulence generating grid upstream of the blade row. Measurements were made with and without a turbulence generating grid at 7 measurement locations to study the effects of the grid generated turbulence on the viscous flow regions. Measurements within the tip leakage vortex revealed that with the presence of grid generated turbulence, the size and strength of the tip leakage vortex has been increased. Effects of the grid on the turbulence field are highly complex, showing regions of increased and decreased turbulence levels. Measurements taken in the wake of the blades show turbulence levels decreasing in the presence of grid generated turbulence due to both inviscid and viscous effects. The inviscid effect is due to blade blocking whereby the velocity fluctuations normal to the surface of the blade are suppressed due to the non penetration condition. Viscous mixing and entrainment effects are seen at the edge of the wake, and are a result of the non-slip condition seen on the surface of the blades.

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