The Visualization of Unsteady Flow Situated Just Behind the Regular Pyramidal Diffuser Inlet

A Case of Higher Pressure Recovery

Abstract

The inner flow situated just behind the regular pyramidal diffuser inlet is a complicated turbulence with a shear voltex produced by separated flow at the diffuser inlet wall and voltex produced by secondary flow at the four corners of the diffuser.
This turbulent flow could be visualized by the tuft method. Photographs and continuous images of it were taken by a telephotographic camera and video tape recorder placed on the diffuser axis downstream from the diffuser outlet.
The power spectrum of static pressure fluctuation was measured at a point on the wall downstream L/W=0.5 from the diffuser inlet.
From the above, it follows that there is a unique flow pattern determind by the diffuser divergence angle and throat Reynolds number.