Effective modelling of acoustofluidic devices

Mikkel Wennemoes Hvitfeld Ley

Research output: Book/ReportPh.D. thesisResearch

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In this thesis work we develop three models for involved systems in the field of microscale acoustofluidics. Because of the complexity of the systems studied, the aim of the Ph.d. project has been to make simplified and effective descriptions of these systems, capturing the most essential behaviour of the system, as opposed to making detailed calculations of idealised cases.
The effective models developed in this thesis concerns: 1) hydrodynamic particle-particle interactions in dense microparticle suspensions, 2) the acoustic field in mm-sized liquid-filled glass capillaries used for acoustic trapping, and 3) acoustic streaming patterns in the devices considered in model 2).
1) We derive an effective model for numerical studies of hydrodynamic particle-particle interactions in microfluidic high-concentration suspensions. A suspension of microparticles placed in a microfluidic channel and influenced by an external force, is described by a continuous particle-concentration field coupled to the continuity and Navier–Stokes equation for the solution. The hydrodynamic interactions are accounted for through the concentration dependence of the suspension viscosity, of the single-particle mobility, and of the momentum transfer between the particles and the suspension.
2) We derive a full 3D numerical model for the coupled acoustic fields in mm-sized water-filled glass capillaries, calculating pressure field in the liquid coupled to the displacement field of the glass channel, taking into account mixed standing and travelling waves as well as absorption. We model the connective tubing at the outlets, either as being free reflecting surfaces or perfect absorbers of outgoing acoustic waves, and we make an effective description of the mechanical actuation of the attached piezoelectric transducer.
3) Using the model for the acoustic field in glass capillary devices derived in 2), we make an effective model for calculating the acoustic streaming velocity in 3D. To do this, we use recent analytical results that allows calculation of the acoustic streaming field resulting from channel-wall oscillations in any direction, with significantly lower computational power requirements compared to previous methods, enabling full 3D calculations.
Original languageEnglish
PublisherDepartment of Physics, Technical University of Denmark
Number of pages141
Publication statusPublished - 2017

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