PhD Studentship: Acoustically Driven Jets: From Water Models to the Stirring of Liquid Metal Alloys

Coventry University

Sir J. Lighthill discovered that fluid motion could be driven by sound waves.The team proposing this project developed a complete theoretical, numerical and experimental framework to study liquid flows generated by ultrasounds. This thesis focuses on applying this idea to the stirring liquid semi-conductors and metallic alloys during their solidification. This could prove transformative for the casting of Aluminium alloys and the production of Photovoltaic silicon as both involve high working temperatures, for which contactless stirring would provide a key advantage. Theory and technical solutions for the application of acoustic streaming to liquid metals have already been developed by the international academic and industrial research community, including the research team driving this research project. The idea pursued in this project is to explore high frequency ultrasounds waves, which have not been well studied but whose large sound attenuation offers promising prospects for liquid metals. To this end, we aim to generate a comprehensive set of experimental and numerical observations of acoustic streaming in view to extend current scaling and similarity laws over a wide range of frequencies and material properties relevant to applications. This will provide a strong basis for developing optimisation strategies to produce the most efficient stirring, under the specific geometrical constraints imposed by each process. A new approach to identify different streaming regimes is to focus on the dimensionless attenuation, which our team identified as best suited to characterise acoustic streaming. One of the aims of the PhD is to understand the influence of this parameter on the flow, since up to now our team only studied the limit N<<1, which is less relevant to liquid metals. To achieve this, we propose to either increase the working frequency or the characteristic length over which the fluid is observed. In particular, the acoustic beam consistency over long distances is a key point to design geometrically complex forcing fields relying on multiple successive reflexions on the container walls. Several cutting edge optical and ultrasound velocimetry techniques available in Lyon will be used to characterise experimentally such streaming configurations in water, while high order spectral element simulations will be conducted in Coventry with Computational Fluid Dynamics software such as NEKTAR++. Finally a first step towards liquid metals applications is also planned with an experimental campaign in the Helmholtz research centre (HZDR), in Dresden (Germany) using galinstan (liquid metal at room temperature) as the working fluid. These significant steps forward in the use of acoustic streaming for stirring will be done by the present PHD student in the framework of a INSA Lyon – Coventry University co-tutelle program involving two research teams, respectively in the LMFA and FCS laboratories.

Entry criteria for applicants to PHD

  • A minimum of a 2:1 first degree in a relevant discipline/subject area with a minimum 60% mark in the project element or equivalent with a minimum 60% overall module average. PLUS the potential to engage in innovative research and to complete the PhD within a 3.5 years
  • a minimum of English language proficiency (IELTS overall minimum score of 7.0 with a minimum of 6.5 in each component)

How to apply

Candidates should contact Prof Alban Potherat – [email protected] with full academic records and CV prior to application. All applications require full documentation including a CV and covering letter.

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