Volume 127, Number 3, August 2019
|Number of page(s)||6|
|Section||Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics|
|Published online||05 September 2019|
A Lagrangian formulation for a gravitational analogue of the acoustic radiation force
1 Univ. Grenoble Alpes, CEA, LETI - F-38000 Grenoble, France
2 Univ. Grenoble Alpes, IRIG- DSBT - F-38000 Grenoble, France
3 Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel - F-38000 Grenoble, France
Received: 26 April 2019
Accepted: 9 July 2019
In this letter, we propose an expression for the instantaneous acoustic radiation force acting on a compressible sphere when it is immersed in a sound field with a wavelength much larger than the particle size (Rayleigh scattering regime). By following a Lagrangian approach, we show that the leading term of the radiation force can alternatively be expressed as a fluctuating gravitation-like force. In other words, the effect of the acoustic pressure gradient is to generate a local acceleration field encompassing the sphere, which gives rise to an apparent buoyancy force, making the object move in the incoming field. When averaging over time, we recover the celebrated Gor’kov expression and emphasize that two terms appear, one local and one convective, which identify with the well-known monopolar and dipolar contributions.
PACS: 43.25.Qp – Radiation pressure / 43.25.+y – Nonlinear acoustics / 47.35.Rs – Sound waves
© EPLA, 2019
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