Michael De Antonio George H. Goedecke
Dept. of Phys., NMSU, Las Cruces, NM 88003-0001
Harry J. Auvermann
Army Res. Lab., Battlefield Environment Directorate, WSMR, NM 88003-5501
The usual approximate acoustic wave equations [e.g., A. D. Pierce, J. Acoust. Soc. Am. 87, 2292 (1990)] were developed for ambient conditions (turbulence) in which the scale length a of the spatial variation of temperature and flow velocity is much larger than the acoustical wavelength (lambda); this is not the case in many applications of interest. An alternative set of coupled acoustical wave equations, valid for any a/(lambda), is presented. These equations involve no approximations except the usual neglect of the viscosity terms in the Navier--Stokes equation for the acoustic flow. For quasistatic or ``frozen'' turbulence, the integral forms of these equations are presented, suitable for application of the digitized Green's function method [G. H. Goedecke and Sean G. O'Brien, Appl. Opt. 27, 2431 (1988)].