scholarly journals An Improved Second-Moment Closure Model of Langmuir Turbulence

2015 ◽  
Vol 45 (1) ◽  
pp. 84-103 ◽  
Author(s):  
Ramsey R. Harcourt
Keyword(s):  
Surface Defects ◽  
Solid Wall ◽  
Vertical Component ◽  
Force Production ◽  
Reynolds Stress Model ◽  
Moment Closure ◽  
Langmuir Turbulence ◽  
Near Surface ◽  
Second Moment ◽  
Second Moment Closure

AbstractA prior second-moment closure (SMC) model of Langmuir turbulence in the upper ocean is modified by introduction of inhomogeneous pressure–strain rate and pressure–scalar gradient closures that are similar to the high Reynolds number, near-wall treatments for solid wall boundaries. This repairs several near-surface defects in the algebraic Reynolds stress model (ARSM) of the prior SMC by redirecting Craik–Leibovich (CL) vortex force production of turbulent kinetic energy out of the surface-normal vertical component and into a horizontal one, with an associated reduction in near-surface CL production of vertical momentum flux. A surface-proximity function introduces a new closure parameter that is tuned to previous results from large-eddy simulations (LES), and a numerical SMC model based on stability functions from the new ARSM produces improved comparisons with mean profiles of momentum and TKE components from steady-state LES results forced by aligned wind and waves. An examination of higher-order quasi-homogeneous closures and a numerical simulation of Langmuir turbulence away from the boundaries both show the near-surface inhomogeneous closure to be both necessary for consistency and preferable for simplicity.

scholarly journals A Second-Moment Closure Model of Langmuir Turbulence

2013 ◽  
Vol 43 (4) ◽  
pp. 673-697 ◽  
Author(s):  
Ramsey R. Harcourt
Keyword(s):  
Reynolds Stress ◽  
Momentum Flux ◽  
Stokes Drift ◽  
Moment Closure ◽  
Langmuir Turbulence ◽  
Stress Equation ◽  
Second Moment ◽  
Stability Functions ◽  
Second Moment Closure ◽  
The Stability

Abstract The Reynolds stress equation is modified to include the Craik–Leibovich vortex force, arising from the interaction of the phase-averaged surface wave Stokes drift with upper-ocean turbulence. An algebraic second-moment closure of the Reynolds stress equation yields an algebraic Reynolds stress model (ARSM) that requires a component of the vertical momentum flux to be directed down the gradient of the Stokes drift, in addition to the conventional component down the gradient of the ensemble-averaged Eulerian velocity. For vertical and horizontal component fluctuations, the momentum flux must be closed using the form , where the coefficient is generally distinct from the eddy viscosity or eddy diffusivity . Rational expressions for the stability functions , , and are derived for use in second-moment closure models where the turbulent velocity and length scales are dynamically modeled by prognostic equations for and . The resulting second-moment closure (SMC) includes the significant effects of the vortex force in the stability functions, in addition to source terms contributing to the and equations. Additional changes are made to the way in which is limited by proximity to boundaries or by stratification. The new SMC model is tuned to, and compared with, a suite of steady-state large-eddy simulation (LES) solutions representing a wide range of oceanic wind and wave forcing conditions. Comparisons with LES show the modified SMC captures important processes of Langmuir turbulence, but not without notable defects that may limit model generality.

Nonlinear second moment closure consistent with shear and strain flows

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 825-831
Author(s):  
Dirk G. Pfuderer ◽  
Claus Eifert ◽  
Johannes Janicka
Keyword(s):  
Moment Closure ◽  
Second Moment ◽  
Second Moment Closure

Computation of Discrete-Hole Film Cooling by a Near-Wall Second-Moment Turbulence Closure

1999 ◽  
Author(s):  
Hamn-Ching Chen ◽  
Gengsheng Wei ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Moment Closure ◽  
Navier Stokes ◽  
Closure Model ◽  
Complex Flow ◽  
Second Moment ◽  
Finite Analytic Method ◽  
Second Moment Closure ◽  
Effectiveness Prediction ◽  
Near Wall

Abstract A multiblock Favre-Averaged Navier-Stokes (FANS) method has been developed in conjunction with a chimera domain decomposition technique for investigation of flat surface, discrete-hole film cooling performance. The finite-analytic method solves the FANS equations in conjunction with a near-wall second-order Reynolds stress (second-moment) closure model and a two-layer k-ε model. Comparisons of flow fields and turbulence quantities with experimental data clearly demonstrate the capability of the near-wall second-moment closure model for accurate resolution of the complex flow interaction bewteen the coolant jet and the mainstream. The near-wall second-moment anisotropic model provides better agreement in adiabatic film effectiveness prediction than the two-layer k-ε model.

A Comparison of Algebraic and Differential Second-Moment Closures for Axisymmetric Turbulent Shear Flows With and Without Swirl

1988 ◽  
Vol 110 (2) ◽  
pp. 216-221 ◽  
Author(s):  
S. Fu ◽  
P. G. Huang ◽  
B. E. Launder ◽  
M. A. Leschziner
Keyword(s):  
Shear Flows ◽  
Turbulent Jets ◽  
Moment Closure ◽  
Turbulent Shear ◽  
Turbulence Energy ◽  
Second Moment ◽  
Second Moment Closure ◽  
Transport Effects ◽  
Related Stress ◽  
Comparison Of The Results

Computations are reported for three axisymmetric turbulent jets, two of which are swirling and one containing swirl-induced recirculation, obtained with two models of turbulence: a differential second-moment (DSM) closure and an algebraic derivative thereof (ASM). The models are identical in respect of all turbulent processes except that, in the ASM scheme, stress transport is represented algebraically in terms of the transport of turbulence energy. The comparison of the results thus provides a direct test of how well the model of stress transport adopted in ASM schemes simulates that of the full second-moment closure. The comparison indicates that the ASM hypothesis seriously misrepresents the diffusive transport of the shear stress in nonswirling axisymmetric flows, while in the presence of swirl the defects extend to all stress components and are aggravated by a failure to account for influential (additive) swirl-related stress-transport terms in the algebraic modelling process. The principal conclusion thus drawn is that in free shear flows where transport effects are significant, it is advisable to adopt a full second-moment closure if turbulence modelling needs to proceed beyond the eddy-viscosity level.

Sign in / Sign up

Export Citation Format

Share Document