Variational multi-scale modeling for particle-laden gravity currents over flat and triangular wavy terrains

Liu, Ning

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https://hdl.handle.net/2142/104992 Copy

Description

Title

Variational multi-scale modeling for particle-laden gravity currents over flat and triangular wavy terrains

Author(s)

Liu, Ning

Issue Date

2019-04-26

Director of Research (if dissertation) or Advisor (if thesis)

Yan, Jinhui

Department of Study

Civil & Environmental Eng

Discipline

Civil Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

Particle-laden flows, RBVMS, Lock-exchange gravity currents

Abstract

We deploy the residual-based variational multi-scale (RBVMS) method for simulating dilute particle-laden currents at large Reynolds number Re = 10000. The physical model is based on the coupling balance of fluid momentum and convection and diffusion. We derive the RBVMS formulation for the weak form of governing equations, design the fine scale parameters and make coupling between fluid momentum equations and density concentration equation. The proposed formulation is utilized to simulate the lock-exchange particle-laden gravity currents. In this paper, two sets of simulations based on the finite element method are conducted on the Stampede2, TACC to validate the models. Firstly, we design a simple physical case that gravity currents over flat terrains in lock-exchange box. Two mesh with the different resolutions are constructed to observe convergence properties of the mesh resolution based on the RBVMS method. Flow statistics are compared against direct numerical simulations (DNS) results and experimental results in the literature and it shows that our computational models is able to simulate quite accurate results with even much lower mesh resolution. Then, the particle-laden gravity currents over triangular wavy terrains with changing wave height are further investigated. The effect of the wave height on the flow statistics is discussed. From the good match between our simulation statistics and DNS or experimental data, it demonstrates that the model we build with RBVMS is able to capture physics of the particle-laden currents. The lower resolution mesh produces quite accurate results. The finite element formulation is stabilized by the RBVMS method in an unstructured mesh.

Graduation Semester

2019-05

Type of Resource

text

Permalink

http://hdl.handle.net/2142/104992

Copyright and License Information

Copyright 2019 Ning Liu

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