Application of a Subfilter-Scale Flux Model over the Ocean Using OHATS Field Data

2009 ◽  
Vol 66 (10) ◽  
pp. 3217-3225 ◽  
Author(s):  
Mark Kelly ◽  
John C. Wyngaard ◽  
Peter P. Sullivan
Keyword(s):  
Field Data ◽  
Pressure Fluctuations ◽  
Model Resolution ◽  
Scalar Flux ◽  
Terra Incognita ◽  
Air Interface ◽  
Momentum Fluxes ◽  
Flux Model ◽  
Horizontal Array ◽  
Effect Of Surface

Abstract Simple rate equation models for subfilter-scale scalar and momentum fluxes have previously been developed for application in the so-called “terra incognita” of atmospheric simulations, where the model resolution is comparable to the scale of turbulence. The models performed well over land, but only the scalar flux model appeared to perform adequately over the ocean. Analysis of data from the Ocean Horizontal Array Turbulence Study (OHATS) reveals a need to account for the moving ocean–air interface in the subfilter stress model. The authors develop simple parameterizations for the effect of surface-induced pressure fluctuations on the subfilter stress, leading to good predictions of subfilter momentum flux both over land and in OHATS.

scholarly journals Improved Subfilter-Scale Models from the HATS Field Data

2007 ◽  
Vol 64 (5) ◽  
pp. 1694-1705 ◽  
Author(s):  
Stephen C. Hatlee ◽  
John C. Wyngaard
Keyword(s):  
Numerical Modeling ◽  
Field Data ◽  
Stress Model ◽  
Scalar Flux ◽  
Terra Incognita ◽  
Advection Term ◽  
Scale Models ◽  
Flux Model ◽  
Horizontal Array ◽  
Grid Mesh

Abstract An earlier paper proposed simple rate-equation models for subfilter-scale (SFS) scalar flux and deviatoric stress in the terra incognita—that is, in numerical modeling applications where the filter (grid-mesh) scale is of the order of the scale of the turbulence. Here the physics in these models is extended and further tested against data from the Horizontal Array Turbulence Study (HATS) experiment. It is found that extensions of the SFS scalar-flux model do not appreciably improve its performance, although an advection term (which could easily be used in modeling applications) substantially and realistically increases the fluctuation level of SFS scalar flux. The addition of buoyancy and rapid-mean-shear terms to the SFS stress model does improve its performance, bringing it to the level of the scalar-flux model.

Cross-Borehole ERT: Sensitivity, Model Resolution, and Field Data Quality

2021 ◽  
Author(s):  
L.M. Madsen ◽  
A.K. Kühl ◽  
L. Levy ◽  
A.V. Christiansen
Keyword(s):  
Data Quality ◽  
Field Data ◽  
Model Resolution

scholarly journals An explicit algebraic model for the subgrid-scale passive scalar flux

2013 ◽  
Vol 721 ◽  
pp. 541-577 ◽  
Author(s):  
Amin Rasam ◽  
Geert Brethouwer ◽  
Arne V. Johansson
Keyword(s):  
Channel Flow ◽  
Rotation Rate ◽  
Model Performance ◽  
Turbulent Channel Flow ◽  
Passive Scalar ◽  
Subgrid Scale ◽  
Scalar Flux ◽  
Algebraic Form ◽  
New Model ◽  
Flux Model

AbstractIn Marstorpet al. (J. Fluid Mech., vol. 639, 2009, pp. 403–432), an explicit algebraic subgrid stress model (EASSM) for large-eddy simulation (LES) was proposed, which was shown to considerably improve LES predictions of rotating and non-rotating turbulent channel flow. In this paper, we extend that work and present a new explicit algebraic subgrid scalar flux model (EASSFM) for LES, based on the modelled transport equation of the subgrid-scale (SGS) scalar flux. The new model is derived using the same kind of methodology that leads to the explicit algebraic scalar flux model of Wikströmet al. (Phys. Fluids, vol. 12, 2000, pp. 688–702). The algebraic form is based on a weak equilibrium assumption and leads to a model that depends on the resolved strain-rate and rotation-rate tensors, the resolved scalar-gradient vector and, importantly, the SGS stress tensor. An accurate prediction of the SGS scalar flux is consequently strongly dependent on an accurate description of the SGS stresses. The new EASSFM is therefore primarily used in connection with the EASSM, since this model can accurately predict SGS stresses. The resulting SGS scalar flux is not necessarily aligned with the resolved scalar gradient, and the inherent dependence on the resolved rotation-rate tensor makes the model suitable for LES of rotating flow applications. The new EASSFM (together with the EASSM) is validated for the case of passive scalar transport in a fully developed turbulent channel flow with and without system rotation. LES results with the new model show good agreement with direct numerical simulation data for both cases. The new model predictions are also compared to those of the dynamic eddy diffusivity model (DEDM) and improvements are observed in the prediction of the resolved and SGS scalar quantities. In the non-rotating case, the model performance is studied at all relevant resolutions, showing that its predictions of the Nusselt number are much less dependent on the grid resolution and are more accurate. In channel flow with wall-normal rotation, where all the SGS stresses and fluxes are non-zero, the new model shows significant improvements over the DEDM predictions of the resolved and SGS quantities.

Using Idealized Coherent Structures to Parameterize Momentum Fluxes in a PBL Mass-Flux Model

2005 ◽  
Vol 62 (8) ◽  
pp. 2829-2846 ◽  
Author(s):  
Cara-Lyn Lappen ◽  
David A. Randall
Keyword(s):  
Coherent Structures ◽  
Mass Flux ◽  
Potential Temperature ◽  
Orientation Angle ◽  
Higher Order ◽  
Horizontal Wind ◽  
Spatial Integration ◽  
Momentum Fluxes ◽  
Flux Model ◽  
Horizontal Momentum

Abstract In 2001, the authors presented a higher-order mass-flux model called assumed distributions with higher-order closure (ADHOC), which represents the large eddies of the planetary boundary layer (PBL) in terms of an assumed joint distribution of the vertical velocity and scalars such as potential temperature or water vapor mixing ratio. ADHOC is intended for application as a PBL parameterization. It uses the equations of higher-order closure to predict selected moments of the assumed distribution, and diagnoses the parameters of the distribution from the predicted moments. Once the parameters of the distribution are known, all moments of interest can be computed. The first version of ADHOC was incomplete in that the horizontal momentum equations, the vertical fluxes of horizontal momentum, the contributions to the turbulence kinetic energy from the horizontal wind, and the various pressure terms involving covariances between pressure and other variables were not incorporated into the assumed distribution framework. Instead, these were parameterized using standard methods. This paper describes an updated version of ADHOC. The new version includes representations of the horizontal winds and momentum fluxes that are consistent with the mass-flux framework of the model. The assumed joint probability distribution is replaced by an assumed joint spatial distribution based on an idealized coherent structure, such as a plume or roll. The horizontal velocity can then be determined using the continuity equation, and the momentum fluxes and variances are computed directly by spatial integration. These expressions contain unknowns that involve the parameters of the assumed coherent structures. Methods are presented to determine these parameters, which include the radius of convective updrafts and downdrafts and the wavelength, tilt, and orientation angle of the convective rolls. The parameterization is tested by comparison with statistics computed from large-eddy simulations. In a companion paper, the results of this paper are built on to determine the perturbation pressure terms needed by the model.

scholarly journals Estimating Dependence of the Turbulent Length Scales on Model Resolution Based on A Priori Analysis

2015 ◽  
Vol 72 (2) ◽  
pp. 750-762 ◽  
Author(s):  
Yuji Kitamura
Keyword(s):  
Boundary Layer ◽  
Aspect Ratio ◽  
A Priori ◽  
Parameterization Scheme ◽  
Length Scale ◽  
Model Resolution ◽  
Length Scales ◽  
Turbulent Length Scale ◽  
Terra Incognita ◽  
A Priori Analysis

Abstract The Reynolds-averaged Navier–Stokes simulation (RANS) and the large-eddy simulation (LES) have been widely used to parameterize unresolved turbulent motions for the atmospheric boundary layer. However, there is an intermediate model resolution, termed terra incognita, in which neither RANS nor LES is appropriate. Although identifying an appropriate turbulent length scale is essential for an eddy-diffusivity model, it is still uncertain how transition of the length scale is between the LES and RANS regimes. In the present study, dependence of the turbulent length scale on the horizontal resolution of a numerical model is investigated using a priori analysis for a convective boundary layer to explore a turbulent parameterization scheme applicable to the terra incognita region. Here, the approaches for estimating the length scales derived from the dissipation rate of the turbulent kinetic energy and the eddy viscosity are proposed. The estimated length scale depends on both the horizontal and vertical grid sizes when the aspect ratio of the grid sizes is close to unity, while it tends to be insensitive to the vertical resolution and asymptotically converges to an upper limit as the aspect ratio increases. Analysis of the length scales divided into horizontal and vertical components reveals that anisotropy of the length scale is remarkable even though the aspect ratio is close to unity. This result suggests that the anisotropic effects of the turbulent flux in subgrid scales should be taken into consideration for a turbulence parameterization scheme.

Redistribution of momentum fluxes on the water-air interface

2000 ◽  
Vol 10 (4) ◽  
pp. 323-330
Author(s):  
E. P. Anisimova ◽  
K. V. Pokazeev ◽  
A. A. Speranskaya
Keyword(s):  
Air Interface ◽  
Momentum Fluxes
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