Modelling of particle paths passing through an ultrasonic standing wave

Modelling of particle paths passing through an ultrasonic standing wave

Within an ultrasonic standing wave particles experience acoustic radiation forces causing agglomeration at the nodal planes of the wave. The technique can be used to agglomerate, suspend, or manipulate particles within a flow. To control agglomeration rate it is important to balance forces on the particles and, in the case where a fluid/particle mix flows across the applied acoustic field, it is also necessary to optimise fluid flow rate.

To investigate the acoustic and fluid forces in such a system a particle model has been developed, extending an earlier model used to characterise the 1-dimensional field in a layered resonator. In order to simulate fluid drag forces, CFD software has been used to determine the velocity profile of the fluid/particle mix passing through the acoustic device. The profile is then incorporated into a MATLAB model. Based on particle force components, a numerical approach has been used to determine particle paths. Using particle coordinates, both particle concentration across the fluid channel and concentration through multiple outlets are calculated.

Such an approach has been used to analyse the operation of a microfluidic flow-through separator, which uses a half wavelength standing wave across the main channel of the device. This causes particles to converge near the axial plane of the channel, delivering high and low particle concentrated flow through two outlets, respectively. By extending the model to analyse particle separation over a frequency range, it is possible to identify the resonant frequencies of the device and associated separation performance.

This approach will also be used to improve the geometric design of the microengineered fluid channels, where the particle model can determine the limiting fluid flow rate for separation to occur, the value of which is then applied to a CFD model of the device geometry.

radiation force, cfd, standing waves, concentration

319-324

Townsend, R.J.

0452b21c-a758-4d4a-925b-1511d9296d62

Hill, M.

0cda65c8-a70f-476f-b126-d2c4460a253e

Harris, N.R.

237cfdbd-86e4-4025-869c-c85136f14dfd

White, N.M.

c7be4c26-e419-4e5c-9420-09fc02e2ac9c

2004

Townsend, R.J.

0452b21c-a758-4d4a-925b-1511d9296d62

Hill, M.

0cda65c8-a70f-476f-b126-d2c4460a253e

Harris, N.R.

237cfdbd-86e4-4025-869c-c85136f14dfd

White, N.M.

c7be4c26-e419-4e5c-9420-09fc02e2ac9c

Townsend, R.J., Hill, M., Harris, N.R. and White, N.M.
(2004)
Modelling of particle paths passing through an ultrasonic standing wave
*Ultrasonics*, 42, (1-9), .

## Abstract

Within an ultrasonic standing wave particles experience acoustic radiation forces causing agglomeration at the nodal planes of the wave. The technique can be used to agglomerate, suspend, or manipulate particles within a flow. To control agglomeration rate it is important to balance forces on the particles and, in the case where a fluid/particle mix flows across the applied acoustic field, it is also necessary to optimise fluid flow rate.

To investigate the acoustic and fluid forces in such a system a particle model has been developed, extending an earlier model used to characterise the 1-dimensional field in a layered resonator. In order to simulate fluid drag forces, CFD software has been used to determine the velocity profile of the fluid/particle mix passing through the acoustic device. The profile is then incorporated into a MATLAB model. Based on particle force components, a numerical approach has been used to determine particle paths. Using particle coordinates, both particle concentration across the fluid channel and concentration through multiple outlets are calculated.

Such an approach has been used to analyse the operation of a microfluidic flow-through separator, which uses a half wavelength standing wave across the main channel of the device. This causes particles to converge near the axial plane of the channel, delivering high and low particle concentrated flow through two outlets, respectively. By extending the model to analyse particle separation over a frequency range, it is possible to identify the resonant frequencies of the device and associated separation performance.

This approach will also be used to improve the geometric design of the microengineered fluid channels, where the particle model can determine the limiting fluid flow rate for separation to occur, the value of which is then applied to a CFD model of the device geometry.

Full text not available from this repository.

## More information

Published date: 2004

Keywords:
radiation force, cfd, standing waves, concentration

## Identifiers

Local EPrints ID: 22728

URI: http://eprints.soton.ac.uk/id/eprint/22728

ISSN: 0041-624X

PURE UUID: 4fb5bf30-ada5-4309-8ab8-e70aa394fade

## Catalogue record

Date deposited: 16 Mar 2006

Last modified: 09 Nov 2017 10:58

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## Contributors

Author:
R.J. Townsend

Author:
N.R. Harris
Author:
N.M. White
## University divisions

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