Artificial viscosity effects on blast pulses in a nonlinear finite difference outdoor sound propagation program Free

In a finite amplitude acoustic blast wave propagation program developed at the University of Illinois, Urbana‐Champaign and at USA‐CERL a fourth‐order artificial viscosity numerical technique is used. The program is based on the method of finite differences, and the artificial viscosity acts to attenuate very high frequencies generated by nonlinear steepening effects. Such high‐frequency components cannot be resolved easily by the finite difference grid due to computer memory limitations. In this presentation the physical basis for the fourth‐order artificial viscosity will be given. Additionally numerical experiment results will bc described that were used to find minimum artificial viscosity coefficients appropriate for blast waves propagating in a free‐field ANSI standard atmosphere. As expected, higher minimum artificial viscosity values were required for stronger blasts. [Work performed at the U.S. Army Construction Engineering Research Laboratory (USA‐CERL), Champaign, IL. Supercomputer support from the National Center for Supercomputing Applications (NCSA), Champaign, IL.]