In April 2016 Manchester eScholar was replaced by the University of Manchester’s new Research Information Management System, Pure. In the autumn the University’s research outputs will be available to search and browse via a new Research Portal. Until then the University’s full publication record can be accessed via a temporary portal and the old eScholar content is available to search and browse via this archive.

Simulation of Turbulent Flows by Deterministic and Statistical Model Coupling in a Dual-Grid System

Nguyen, Philipp

[Thesis]. Manchester, UK: The University of Manchester; 2020.

Access to files

Abstract

Despite the increasing computational power available to conduct turbulence-resolving Large Eddy Simulation (LES), it is still very expensive to simulate high Reynolds number flows as they appear in industrial problems. This thesis addresses the search for economic means to carry out LES by proposing a novel hybrid RANS/LES model, based on parallel LES and RANS simulations on two separate computational grids and a blended subgrid-scale model. The two-simulation framework enables the LES to be run on isotropic grids with low wall-parallel and wall-normal resolution, with the latter still being rare among present hybrid RANS/LES models. In contrast, the auxiliary RANS simulation is run on wall-refined grids with high-aspect ratio cells, where a full grid overlapping avoids complex boundary conditions. The seamless blending on the subgrid-scale level permits an unhindered movement of turbulent structures into and out of the RANS/LES subdomains. The Dual-Grid model is applied to a variety of wall-bounded flows with increasing flow complexity. Extensive testing on a heated plane channel flow for a range of Reynolds numbers overall shows a good prediction quality for velocity and turbulent stresses, although the grids are too coarse for conventional LES. Then, a periodic hill flow is simulated at different Reynolds numbers. Although the boundary layer separation is sensitive to the near-wall grid resolution and turbulence modelling, the model performance is competitive with other hybrid models on similar grid topologies. The Dual-Grid model is also demonstrated on a rib-roughened duct flow with a squared channel cross-section and high blockage ratio; a geometry usually found in turbine blade cooling applications. Again, the results are consistent with experimental data. Naturally, the computational cost is found to be higher than of the underlying LES on identical grids, yet, the prediction quality is increased. With possible improvements to the transfer of information across the simulations to reduce computational cost and to the heat transfer modelling, it is concluded that the proposed model has potential to become relevant to the industry.

Bibliographic metadata

Type of resource:
Content type:
Form of thesis:
Type of submission:
Degree type:
Doctor of Philosophy
Degree programme:
PhD Mechanical, Aerospace and Civil Engineering (42 months)
Publication date:
Location:
Manchester, UK
Total pages:
228
Abstract:
Despite the increasing computational power available to conduct turbulence-resolving Large Eddy Simulation (LES), it is still very expensive to simulate high Reynolds number flows as they appear in industrial problems. This thesis addresses the search for economic means to carry out LES by proposing a novel hybrid RANS/LES model, based on parallel LES and RANS simulations on two separate computational grids and a blended subgrid-scale model. The two-simulation framework enables the LES to be run on isotropic grids with low wall-parallel and wall-normal resolution, with the latter still being rare among present hybrid RANS/LES models. In contrast, the auxiliary RANS simulation is run on wall-refined grids with high-aspect ratio cells, where a full grid overlapping avoids complex boundary conditions. The seamless blending on the subgrid-scale level permits an unhindered movement of turbulent structures into and out of the RANS/LES subdomains. The Dual-Grid model is applied to a variety of wall-bounded flows with increasing flow complexity. Extensive testing on a heated plane channel flow for a range of Reynolds numbers overall shows a good prediction quality for velocity and turbulent stresses, although the grids are too coarse for conventional LES. Then, a periodic hill flow is simulated at different Reynolds numbers. Although the boundary layer separation is sensitive to the near-wall grid resolution and turbulence modelling, the model performance is competitive with other hybrid models on similar grid topologies. The Dual-Grid model is also demonstrated on a rib-roughened duct flow with a squared channel cross-section and high blockage ratio; a geometry usually found in turbine blade cooling applications. Again, the results are consistent with experimental data. Naturally, the computational cost is found to be higher than of the underlying LES on identical grids, yet, the prediction quality is increased. With possible improvements to the transfer of information across the simulations to reduce computational cost and to the heat transfer modelling, it is concluded that the proposed model has potential to become relevant to the industry.
Thesis main supervisor(s):
Thesis co-supervisor(s):
Funder(s):
Language:
en

Institutional metadata

University researcher(s):

Record metadata

Manchester eScholar ID:
uk-ac-man-scw:324240
Created by:
Nguyen, Philipp
Created:
26th March, 2020, 20:00:11
Last modified by:
Nguyen, Philipp
Last modified:
4th January, 2021, 11:29:17

Can we help?

The library chat service will be available from 11am-3pm Monday to Friday (excluding Bank Holidays). You can also email your enquiry to us.