Title: A Mach 1.92 jet and its near acoustic field

Description: A round Mach 1.92 jet is simulated with high-order finite differences and fourth-order Runge-Kutta time advancement. The turbulence is visualized with contours of vorticity magnitude and the radiating sound field with contours of dilatation (divergence of velocity).

The mechanism by which a jet at this Mach number radiates noise is fairly well understood. Since the unsteady turbulent structures travel supersonically relative to the ambient flow, they radiate Mach waves in the same way a supersonic aircraft makes a sonic boom. These Mach waves can be seen in the animation. The mechanism is different (and much less efficient) in a subsonic jet because the turbulent structures move subsonically. In that case, noise generation depends upon a subtle interaction and evolution of the turbulent structures. They themselves do not directly make noise.

J. B. Freund homepage

Credits: Movie by R. Darke & J. B. Freund

References: D.~Darke & J.~B.~Freund, "Mach wave radiation from a jet at Mach 1.92," Phys.~Fluids, Galary of fluid motion winner, 13(9), S3 (2001).

J. B. Freund, S. K. Lele & P. Moin, "Numerical simulation of a Mach 1.92 turbulent jet and its sound field," AIAA J., 38(11), 2023-2031, (2000).

Web Page: http://www.mechse.illinois.edu/sites/index.php?site_id=64

Contributed By: Prof. Jonathan B. Freund, University of Illinois at Urbana-Champaign