Browsing by Author "Kim, Hyun S."

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    Active and Passive Acoustic Behavior of Bubble Clouds at the Ocean’s Surface
    (The Journal of the Acoustical Society of America, 1993-06) Prosperetti, Andrea; Lu, N.Q.; Kim, Hyun S.
    The emission and scattering of sound from bubble clouds is studied theoretically. It is shown that clouds having a size and air content similar to what might be expected as a consequence of the breaking of ocean waves can oscillate at frequencies as low as 100 Hz and below. Thus cloud oscillations may furnish an explanation of the substantial amount of low?frequency wind?dependent oceanic ambient noise observed experimentally. Detailed results for the backscattering from bubble clouds—particularly at low grazing angles—are also presented and shown to be largely compatible with oceanic data. Although the cloud model used here is idealized (a uniform hemispherical cloud under a plane water free?surface), it is shown that the results are relatively robust in terms of bubble size, distribution, and total air content. A similar insensitivity to cloud shape is found in a companion paper [Sarkar and Prosperetti, J. Acoust. Soc. Am. 93, XXX (1993)].
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    Numerical Simulation of the Motion of Rigid Spheres in Potential Flow
    (SIAM Journal on Applied Mathematics, 1992-12) Kim, Hyun S.; Prosperetti, Andrea
    A numerical method for the simulation of the motion of a number of rigid spheres in a potential flow is described. The equations derived are applicable to the case of spheres in an unbounded fluid or in a circular tube of variable cross section. The method itself is, however, more general and can be applied to a variety of situations. The maximum number of spheres is only limited by the available computational resources. Some numerical examples are described both as a test of the method and for their intrinsic interest. The ultimate aim of the study is to develop a tool capable of shedding light on the nature of the inertial coupling in two-phase disperse flows.