Acoustically-driven jets: from water models to the stirring of liquid metal alloys

Eligibility: UK/EU/International graduates with the required entry requirements

Funding details: Bursary plus tuition fees (UK/International (including EU at international rates from Sept 21)

Duration: Full-Time – between three and three and a half years fixed term

Application deadline: 27 May 2023

Interview date: Will be confirmed to shortlisted candidates

Start date: September 2023

For further details contact: Prof. Alban Potherat

Introduction

Coventry University (CU) is inviting applications from suitablyqualified graduates for a (fully-funded/self-funded) PhD studentship.

Project details

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.

Funding

Tution fees and stipend.

Benefits

The successful candidate will receive comprehensive research training including technical, personal and professional skills. All researchers at Coventry University (from PhD to Professor) are part of the Doctoral College and Centre for Research Capability and Development, which provides support with high-quality training and career development activities.

Candidate Specification

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.
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)