Phenomenology of laminar acoustic streaming jets

TL;DR

This paper investigates the physical mechanisms of laminar acoustic streaming jets using numerical simulations, deriving scaling laws for flow velocity in different regions to inform experimental and industrial design.

Contribution

It introduces a novel modeling approach for the acoustic force including attenuation effects and provides detailed scaling laws for flow regimes along the jet.

Findings

Flow accelerates near the source and decays at a distance.

Scaling laws relate jet velocity to acoustic force and beam diffraction.

The study clarifies the spatial structure of Eckart streaming jets.

Abstract

This work identifies the physical mechanisms at play in the different flow regions along an Eckart acoustic streaming jet by means of numerical simulation based on a novel modeling of the driving acoustic force including attenuation effects. The flow is forced by an axisymmetric beam of progressive sound waves attenuating over a significant part of a closed cylindrical vessel where the jet is confined. We focus on the steady, axisymmetric and laminar regime. The jet typically displays a strong acceleration close to the source before reaching a peak velocity. At further distances from the transducer, the on-axis jet velocity smoothly decays before reaching the opposite wall. For each of these flow regions along the jet, we derive scaling laws for the on-axis velocity with the magnitude of the acoustic force and the diffraction of the driving acoustic beam. These laws highlight the different flow regimes along the jet and establish a clear picture of its spatial structure, able to inform the design of experimental or industrial setups involving Eckart streaming jets.