Accession Number : ADA430481


Title :   Equations for Finite-Difference, Time-Domain Simulation of Sound Propagation in Moving Inhomogeneous Media and Numerical Implementation


Corporate Author : NEW MEXICO STATE UNIV LAS CRUCES DEPT OF PHYSICS


Personal Author(s) : Ostashev, Vladimir E ; Wilson, D K ; Liu, Lanbo ; Aldridge, David F ; Symons, Neil P


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a430481.pdf


Report Date : Feb 2005


Pagination or Media Count : 16


Abstract : Finite-difference, time-domain (FDTD) calculations are typically performed with partial differential equations that are first order in time. Equation sets appropriate for FDTD calculations in a moving inhomogeneous medium with an emphasis on the atmosphere! are derived and discussed in this paper. Two candidate equation sets, both derived from linearized equations of fluid dynamics, are proposed. The first, which contains three coupled equations for the sound pressure, vector acoustic velocity, and acoustic density, is obtained without any approximations. The second, which contains two coupled equations for the sound pressure and vector acoustic velocity, is derived by ignoring terms proportional to the divergence of the medium velocity and the gradient of the ambient pressure. It is shown that the second set has the same or a wider range of applicability than equations for the sound pressure that have been previously used for analytical and numerical studies of sound propagation in a moving atmosphere. Practical FDTD implementation of the second set of equations is discussed. Results show good agreement with theoretical predictions of the sound pressure due to a point monochromatic source in a uniform, high Mach number flow and with Fast Field Program calculations of sound propagation in a stratified moving atmosphere.


Descriptors :   *NUMERICAL ANALYSIS , *FINITE DIFFERENCE THEORY , *MATHEMATICAL PREDICTION , *LINEAR ALGEBRAIC EQUATIONS , *HOMOGENEOUS REACTORS , COUPLING(INTERACTION) , REPRINTS , DENSITY , COMPUTATIONS , FLOW RATE , SOUND TRANSMISSION , VECTOR ANALYSIS , MACH NUMBER , EQUATIONS , FLUID DYNAMICS , ACOUSTIC VELOCITY , STRATIFICATION , SOUND PRESSURE , ATMOSPHERES


Subject Categories : Theoretical Mathematics
      Statistics and Probability
      Nuclear Fission Reactors(power)


Distribution Statement : APPROVED FOR PUBLIC RELEASE