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# Harmonic Fluids

By Troy Parker,2014-06-30 13:50
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Harmonic Fluids

Harmonic Fluids () 3 ppt Changxi Zheng Doug L. James

Cornell University

Introduction

(1)

How to simulate synchronized physics-based sounds for familiar splashes and splatters What causes fluid sounds?

(2) Perhaps surprisingly, the majority of sound from a splashing droplet of water

arises from harmonic vibrations resulting from the entrainment (creation) of millimeterscale air

bubbles (see Figure 1).

(3) Basically, the bubble oscillator stores potential energy as compressed air and surface

tension, and kinetic energy as surrounding fluid vibrations. The important role of these tiny “acoustic bubbles微小发声水泡 in water sound generation has been recognized for nearly a century since

pioneering work by Minnaert [1933], and large texts have since been written about them [Leighton

1994]. Recently, van den Doel [2005] proposed bubbles as primitives for fluid sound synthesis, and

synthesized compelling sounds using stochastically excited modal sound banks.

4 we

choose to model sound wave propagation

and radiation in fluids by assuming they

are a sequence of static problems.!! Given

the harmonic nature of bubbles, we can

efficiently model sound waves in the

frequency-domain using the Helmholtz

wave equation.!!

5 Our approach:

We model the creation of bubbles by air

entrainment at the fluid surface; the

the fluid flow; the surface vibrations

induced by the bubbles’ vibrations; and the

radiation of these vibrations into the air,

producing sound (see Figure 3).

We weight （加权）each oscillator by its

bubble-to-ear acoustic transfer function, which is modeled as a discrete Green’s function of the Helmholtz equation. (赫尔姆霍茨方程 核心算法)

6

To solve potentially millions of 3D Helmholtz problems, we propose a fast dual-domain multipole (声场多极子) boundary-integral solver.

Our main contribution is a parallel algorithm for estimating sound radiation.

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