Quiet wall jet facility for basic aero/hydroacoustics research

The design, performance, and research applications of a novel quiet air flow facility are described. This facility is an open-jet with a semi-circular orifice situated in a planar baffle. A flat plate which is typically 30.5 cm wide by 125 cm long inserts into the orifice 1.2 cm above the flat side forming a wall jet over the plate. For prevention of the formation of a jet free shear layer and control of corner vortex contamination, an acoustically transparent, but flow impermeable semi-circular mylar tube is placed over the plate. An acoustically and mechanically isolated 20 HP centrifugal blower, provides air which passes through a treated labyrinth and flexible hose to the settling chamber of the wall jet facility where turbulence management screens are located. The flat plate apparatus is inserted into a very large flow-through anechoic chamber which is described. Acoustic probes (both pressure and intensity) are moved robotically with a computer controlled scanner. With a rigid flat plate, measurements of the acoustic emissions from basic turbulent boundary layer flow structures are being performed. In another investigation, rearward facing steps and ramps of various heights and angles which promote natural flow separation are substituted. The direct acoustic radiation is measured along with wall pressure statistics and plate response.