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

For many years, the resolution of the near-wall turbulent layer has been a hot topic in fluid dynamics. Near-wall turbulence modelling is a computationally expensive problem. The 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 & Utyuzhnikov, Computers & Fluids, 2022). 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 in a relevant science or engineering related discipline.

Funding

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This project is also eligible for the Osborne Reynolds top-up Scholarship which provides an additional £1500 per year top-up to other funding sources for outstanding candidates. Successful applicants will be automatically considered for this top-up.

  Before you apply

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How to apply

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