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Shock-wave/boundary-layer interactions with sidewall effects in the OpenSBLI code-generation framework

Shock-wave/boundary-layer interactions with sidewall effects in the OpenSBLI code-generation framework
Shock-wave/boundary-layer interactions with sidewall effects in the OpenSBLI code-generation framework
Numerical work on shockwave/boundary-layer interactions (SBLIs) to date has largely focused on span-periodic quasi-2D configurations that neglect the influence lateral confinement has on the core flow. The present thesis is concerned with the effect of flow confinement on Mach 2 laminar and transitional SBLI in rectangular ducts. An oblique shock generated by a deflection plate forms a conical swept SBLI with sidewall boundary layers before reflecting from the bottom wall of the domain. In the laminar cases, multiple large regions of flow-reversal are observed on the sidewalls, bottom wall and at the corner intersection of the duct. The main interaction is found to be strongly three-dimensional and highly dependent on the geometry of the duct. Comparison to quasi-2D span-periodic simulations showed that sidewalls strengthen the main interaction, with a 31% increase in the central separation bubble length for the baseline aspect ratio one configuration. Parametric studies of shock strength and duct aspect ratio were performed to find limiting behaviours. Topological features of the three-dimensional separation are identified and shown to be consistent with ‘owl-like’ separations of the first kind.
Time-dependent forcing strips are added to the laminar duct to generate disturbances for the transitional SBLI cases. The transition is observed to develop first in the low-momentum corners of the duct and spread out in a wedge shape. The central separation bubble is seen to react dynamically to oncoming turbulent spots, shifting laterally across the span. While instantaneous corner separations do occur, the time-averaged corner flow remains attached. An assessment of low-dissipative shock-capturing schemes is also performed for transitional and turbulent shock interactions. Targeted Essentially Non-Oscillatory (TENO) schemes are found to provide improved resolution for compressible turbulence compared to conventional Weighted Essentially Non-Oscillatory (WENO) schemes.
A significant portion of the PhD project has involved the co-development of a new open-source CFD code named OpenSBLI. OpenSBLI is a Python-based code-generation framework that generates C code in the Oxford Parallel Structured (OPS) embedded Domain Specific Language (eDSL). OpenSBLI is an explicit CFD solver for the 3D compressible Navier-Stokes equations, utilizing high-order finite-difference schemes on structured meshes. The simulation code generated by OpenSBLI targets massively-parallel High-Performance Computing (HPC) architectures including CPUs, GPUs and many-core accelerator cards. The thesis documents the structure and implementation of the code. A suite of validation cases are performed to demonstrate the accuracy and correctness of the code implementation.
Lusher, David
44ff9096-3c84-440a-9f64-946636aff985
Lusher, David
44ff9096-3c84-440a-9f64-946636aff985
Sandham, Neil
0024d8cd-c788-4811-a470-57934fbdcf97

Lusher, David (2020) Shock-wave/boundary-layer interactions with sidewall effects in the OpenSBLI code-generation framework. University of Southampton, Doctoral Thesis, 217pp.

Record type: Thesis (Doctoral)

Abstract

Numerical work on shockwave/boundary-layer interactions (SBLIs) to date has largely focused on span-periodic quasi-2D configurations that neglect the influence lateral confinement has on the core flow. The present thesis is concerned with the effect of flow confinement on Mach 2 laminar and transitional SBLI in rectangular ducts. An oblique shock generated by a deflection plate forms a conical swept SBLI with sidewall boundary layers before reflecting from the bottom wall of the domain. In the laminar cases, multiple large regions of flow-reversal are observed on the sidewalls, bottom wall and at the corner intersection of the duct. The main interaction is found to be strongly three-dimensional and highly dependent on the geometry of the duct. Comparison to quasi-2D span-periodic simulations showed that sidewalls strengthen the main interaction, with a 31% increase in the central separation bubble length for the baseline aspect ratio one configuration. Parametric studies of shock strength and duct aspect ratio were performed to find limiting behaviours. Topological features of the three-dimensional separation are identified and shown to be consistent with ‘owl-like’ separations of the first kind.
Time-dependent forcing strips are added to the laminar duct to generate disturbances for the transitional SBLI cases. The transition is observed to develop first in the low-momentum corners of the duct and spread out in a wedge shape. The central separation bubble is seen to react dynamically to oncoming turbulent spots, shifting laterally across the span. While instantaneous corner separations do occur, the time-averaged corner flow remains attached. An assessment of low-dissipative shock-capturing schemes is also performed for transitional and turbulent shock interactions. Targeted Essentially Non-Oscillatory (TENO) schemes are found to provide improved resolution for compressible turbulence compared to conventional Weighted Essentially Non-Oscillatory (WENO) schemes.
A significant portion of the PhD project has involved the co-development of a new open-source CFD code named OpenSBLI. OpenSBLI is a Python-based code-generation framework that generates C code in the Oxford Parallel Structured (OPS) embedded Domain Specific Language (eDSL). OpenSBLI is an explicit CFD solver for the 3D compressible Navier-Stokes equations, utilizing high-order finite-difference schemes on structured meshes. The simulation code generated by OpenSBLI targets massively-parallel High-Performance Computing (HPC) architectures including CPUs, GPUs and many-core accelerator cards. The thesis documents the structure and implementation of the code. A suite of validation cases are performed to demonstrate the accuracy and correctness of the code implementation.

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Published date: March 2020

Identifiers

Local EPrints ID: 445538
URI: http://eprints.soton.ac.uk/id/eprint/445538
PURE UUID: 59be64e6-e065-4a19-a2df-c6d3e53c512d
ORCID for Neil Sandham: ORCID iD orcid.org/0000-0002-5107-0944

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Date deposited: 15 Dec 2020 17:30
Last modified: 18 Feb 2021 16:52

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Contributors

Author: David Lusher
Thesis advisor: Neil Sandham ORCID iD

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