Near-wall domain decomposition for turbulence modelling based on RANS-LES

About the Project

For many years, the resolution of the near-wall turbulent layer is a hot topic in fluid dynamics. Near-wall turbulence modelling is a computationally expensive problem. A major part of the computing time is taken up by the resolution of a thin layer, which includes a laminar sublayer adjacent to the wall. As a result, the resolution of the near-wall layer, the thickness of which is about 1% of the entire region, requires up to 90% of all computational costs, even in the case of using the Reynolds averaging models. Over the past decades, the Reynolds models, or RANS models, have been developed tremendously and have seen widespread use. However, their accuracy is very limited and often does not meet state-of-the-art requirements.

With the development of modern high-performance computers, direct numerical simulation (DNS) of turbulence has become possible. With its qualitative resolution, DNS is often viewed as a substitute for a full-scale experiment. At the same time, this approach is extremely limited in practical applications due to the huge consumption of computational resources. Practically, it is much more realistic to use the LES (or large eddy simulation) approach. At the same time, the application of LES becomes much more difficult due to the need to resolve small vortices near the wall. Modern methods for studying near-wall turbulent flows are largely based on hybrid RANS-LES models. The use of RANS models near the wall is justified by the large damping effect of the wall on the level of turbulent pulsations. In addition, the plane-parallel nature of the flow at the wall simplifies the justification and application of RANS models. The weakest point of this hybridization is the problem of coupling RANS and LES. The most common approach is associated with the introduction of a buffer transition zone, in which none of the models is applicable. An alternative approach is based on the strong hybridization of models or heterogeneous decomposition. In this case, there is the problem of setting adequate boundary conditions at the interface.

The project is devoted to a novel approach based on the non-overlapping domain decomposition (NDD). This approach has proven to be very efficient for solving steady and unsteady RANS (see, e.g., Lyu et al., Physics of Fluids, 2024). The domain decomposition is achieved via the transfer of the boundary condition from the wall to an interface boundary. The obtained interface boundary conditions for LES are mesh-independent and nonlocal over space and time. They include a memory term that contains the effect of modelled vortices on the vortices resolved with LES.

This project is aimed at developing a RANS-LES heterogeneous decomposition method without a subdomain intersection. The ultimate goal of the project is to create an efficient and fairly universal approach to the practical application of LES for modeling turbulent flows around complex configurations. If the project is successful, it might be widely used for industrial applications.

Eligibility

Applicants should have, or expect to achieve, at least a 2.1 honours degree or a master’s (or international equivalent) in a relevant science or engineering related discipline.

Funding

This 3.5-year PhD is for self-funded students. Exceptional candidates will be considered for Faculty funding (this will include an annual tax-free stipend of £20,780 and tuition fees will be paid. We expect the stipend to increase each year).

At The University of Manchester, we offer a range of scholarships, studentships and awards at university, faculty and department level, to support both UK and overseas postgraduate researchers.

For more information, visit our funding page or search our funding database for specific scholarships, studentships and awards you may be eligible for.

Before you apply

We strongly recommend that you contact the supervisor for this project before you apply. Please include details of your current level of study, academic background and any relevant experience and include a paragraph about your motivation to study this PhD project.

How to apply

Apply online through our website: https://uom.link/pgr-apply-2425

When applying, you’ll need to specify the full name of this project, the name of your supervisor, if you already having funding or if you wish to be considered for available funding through the university, details of your previous study, and names and contact details of two referees.

Your application will not be processed without all of the required documents submitted at the time of application, and we cannot accept responsibility for late or missed deadlines. Incomplete applications will not be considered.

After you have applied you will be asked to upload the following supporting documents:

• Final Transcript and certificates of all awarded university level qualifications
• Interim Transcript of any university level qualifications in progress
• CV
• Supporting statement: A one or two page statement outlining your motivation to pursue postgraduate research and why you want to undertake postgraduate research at Manchester, any relevant research or work experience, the key findings of your previous research experience, and techniques and skills you’ve developed. (This is mandatory for all applicants and the application will be put on hold without it).
• Contact details for two referees (please make sure that the contact email you provide is an official university/work email address as we may need to verify the reference)
• English Language certificate (if applicable)

If you have any questions about making an application, please contact our admissions team by emailing FSE.doctoralacademy.admissions@manchester.ac.uk.