COMPARISON OF COMPUTER CODES FOR THE PROPAGATION OF SONIC-BOOM WAVE-FORMS THROUGH ISOTHERMAL ATMOSPHERES

A numerical exercise to compare computer codes for the propagation of sonic booms through idealized atmospheres is reported. Ground waveform s are calculated using four different codes or algorithms: (1) weak sh ock theory, an analytical prediction; (2) SHOCKN, a mixed time and fre quency domain code developed at the University of Mississippi; (3) ZEP HYRUS, another mixed time and frequency code developed at the Universi ty of Texas; and (4) THOR, a pure time domain code recently developed at the University of Texas. The codes are described and their differen ces noted. They are then used to calculate propagation for two differe nt source waveforms, for both a uniform and isothermal (varying densit y) atmosphere, with and without the presence of molecular relaxation. In all cases the results of THOR, SHOCKN, and ZEPHYRUS are in excellen t agreement. Because the weak shock theory algorithm does not include the effect of ordinary absorption, it does not predict the shock struc ture provided by the other codes. This leads to discrepancies particul arly for an atmosphere that includes relaxation effects. (C) 1996 Acou stical Society of America.