### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 1aPA3. Finite amplitude sound beam propagation in dense gases.

**Edward A. Cox
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*Dept. of Math. Phys., Univ. College Dublin, Belfield, Dublin 4, Ireland
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**Alfred Kluwick
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*Inst. of Fluid Dynam. and Heat Transfer, Technical Univ., Vienna, Austria
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Current studies indicate that fluids with high specific heats may prove
useful in a number of technological applications. These fluids have been shown
to exhibit a range of new phenomena---the most prominent example probably being
the existence of negative shocks (shocks across which the normal stresses
decrease). Of particular theoretical interest is the possibility of propagating
waves with mixed nonlinearity where for example positive and negative shocks
propagate as stable structures within a single wave pulse. Here existing results
for essentially plane waves are extended to include the effects of signal
variations in directions transverse to the propagation direction. An extended
Khoklov--Zabolotskaya--Kuznetsov (eKZK) is derived which models a propagating
finite-amplitude sound beam. The extension to mixed nonlinearity predicts the
formation of postitive and negative shocks and the existence of sonic shocks
(where the shock speed is equivalent to the convected sound speed upstream or
downstream of the shock). Numerical results are presented illustrating the
combined effects of nonlinearity and diffraction for both time harmonic and
pulsed radiators. An analysis of these results is given in terms of propagating
characteristic surfaces.