Graduation Year

2014

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Environmental Engineering

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Andrés E. Tejada-Martínez, Ph.D.

Co-Major Professor

Yuncheng You, Ph.D.

Committee Member

Yuncheng You, Ph.D.

Committee Member

Rasim Guldiken, Ph.D.

Committee Member

Autar Kaw, Ph.D.

Committee Member

Daniel C. Simkins, Jr., Ph.D.

Keywords

Computational Fluid Dynamics, Finite element method, Iso-geometric analysis, Large Eddy Simulation, RBVMS method, Wall-Modelling

Abstract

Large-eddy simulation (LES) of wind and wave forced oceanic turbulent boundary layers is performed using the residual-based variational multiscale method (RBVMS) and near-wall modeling. Wind and surface gravity wave forcing generates Langmuir turbulence characterized by Langmuir circulation (LC) with largest scales consisting of streamwise vortices aligned in the direction of the wind, acting as a secondary flow structure to the primary wind-driven component of the flow. The LES here is representative of a shallow water continental shelf flow (10 to 30 meters in depth) far from lateral boundaries in which LC engulfs the full depth of the water column and disrupts the bottom log layer. Field measurements indicate that occurrence of full-depth LC is typical during the passage of storms. The RBVMS method with quadratic NURBS (Non-Uniform Rational B-splines) with near-wall resolution is shown to possess good convergence characteristics for this flow. The use of near-wall modeling facilitates simulations with expanded domains over horizontal directions. Thus, these simulations are able to resolve multiple Langmuir cells permitting analysis of the interaction between the cells. Results in terms of velocity statistics are presented from simulations performed with various domain sizes and distinct near-wall treatments: (1) the classical treatment based on prescription of the wall shear stress assuming a law of the wall and (2) a recent treatment based on weak imposition of the no-slip bottom boundary condition.

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