ASA 124th Meeting New Orleans 1992 October

1pEA2. Observations on subsonic edge tones, continued.

Noel Mascarenhas

Alan Powell

Dept. of Mech. Eng., Univ. of Houston, Houston, TX 77204-4792

The included angle (alpha) of the (w)edge and the stream breadth influence the region of operation (RO) and the frequency characteristics of the classical edge tone (laminar jet, <50 m s[sup -1]) [Powell and Unfried (1964)]. This is also so for high-speed subsonic edge tones (turbulent jet, 48--315 m s[sup -1], 0.14(less than or equal to)Mach number(less than or equal to)1). For (alpha)=8(degrees), 135(degrees), and 180(degrees), the RO decreases while the frequencies for the first two continuous frequency stages are closely proportional to jet velocity and inversely proportional to nozzle-edge distance, but are 5% higher for 180(degrees). For increasing nozzle breadth, 25, 43, and 60 mm (nozzle width 1 mm) the RO increases; frequencies remain the same but with changed jump positions. The sound pressure of the tone decreases with increasing wedge angle and increases proportionally (or more) with the nozzle breadth. The results are qualitatively much the same as for the classical case, except that there are multiple tones and there is very little hysteresis with the frequency jumps; surprisingly, there is apparently no effect dueto the exit velocity being sonic. [Work supported by the Texas Advanced Research Program.]