Introducing Consistently Formulated Eddy-Viscosity Coefficient with Spalart–Allmaras Model

AIAA Journal ◽  
2020 ◽  
Vol 58 (6) ◽  
pp. 2764-2769
Author(s):  
M. M. Rahman
Keyword(s):  
Eddy Viscosity ◽  
Viscosity Coefficient ◽  
Eddy Viscosity Coefficient

scholarly journals VERTICAL VARIATION OP UNDERTOW IN THE SURF ZONE

1988 ◽  
Vol 1 (21) ◽  
pp. 33 ◽  
Author(s):  
Akio Okayasu ◽  
Tomoya Shibayama ◽  
Kiyoshi Horikawa
Keyword(s):  
Laboratory Experiments ◽  
Eddy Viscosity ◽  
Surf Zone ◽  
Viscosity Coefficient ◽  
Laser Doppler Velocimeter ◽  
Vertical Variation ◽  
Two Component ◽  
The Mean ◽  
Eddy Viscosity Coefficient ◽  
The Vertical Distribution

In order to establish a model of the vertical distribution of the undertow, laboratory experiments were performed on uniform slopes of 1/20 and 1/30. The turbulent velocity in the surf zone including the area close to the bottom was measured by using a two-component laser doppler velocimeter. The distributions of the mean Reynolds stress and the mean eddy viscosity coefficient were calculated. Based on the experimental results, a model to predict the vertical profile of the undertow was presented.

One-equation sub-grid scale model with variable eddy-viscosity coefficient

2015 ◽  
Vol 107 ◽  
pp. 155-164 ◽  
Author(s):  
Javad Taghinia ◽  
Md Mizanur Rahman ◽  
Timo Siikonen ◽  
Ramesh K. Agarwal
Keyword(s):  
Eddy Viscosity ◽  
Viscosity Coefficient ◽  
Scale Model ◽  
Variable Eddy Viscosity ◽  
Eddy Viscosity Coefficient

scholarly journals Inversion Study of Vertical Eddy Viscosity Coefficient Based on an Internal Tidal Model with the Adjoint Method

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Guangzhen Jin ◽  
Qiang Liu ◽  
Xianqing Lv
Keyword(s):  
Eddy Viscosity ◽  
Adjoint Method ◽  
Viscosity Coefficient ◽  
Optimization Method ◽  
Gradient Descent Method ◽  
Bfgs Method ◽  
Tidal Model ◽  
Vertical Eddy Viscosity ◽  
Eddy Viscosity Coefficient ◽  
Vertical Eddy

Based on an isopycnic-coordinate internal tidal model with the adjoint method, the inversion of spatially varying vertical eddy viscosity coefficient (VEVC) is studied in two groups of numerical experiments. In Group One, the influences of independent point schemes (IPSs) exerting on parameter inversion are discussed. Results demonstrate that the VEVCs can be inverted successfully with IPSs and the model has the best performance with the optimal IPSs. Using the optimal IPSs obtained in Group One, the inversions of VEVCs on two different Gaussian bottom topographies are carried out in Group Two. In addition, performances of two optimization methods of which one is the limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) method and the other is a simplified gradient descent method (GDM-S) are also investigated. Results of the experiments indicate that this adjoint model is capable to invert the VEVC with spatially distribution, no matter which optimization method is taken. The L-BFGS method has a better performance in terms of the convergence rate and the inversion results. In general, the L-BFGS method is a more effective and efficient optimization method than the GDM-S.

A comparison of models for coastal circulation

1995 ◽  
Vol 32 (7) ◽  
pp. 55-62
Author(s):  
Anastasios I. Stamou ◽  
George C. Christodoulou ◽  
Lisa A. Bensasson ◽  
Iason E. Lazaridis
Keyword(s):  
Finite Difference ◽  
Eddy Viscosity ◽  
Numerical Models ◽  
Viscosity Coefficient ◽  
Element Model ◽  
Coastal Circulation ◽  
Difference Model ◽  
Open Sea ◽  
Circulation Patterns ◽  
Eddy Viscosity Coefficient

A comparative study of coastal circulation by means of two depth-averaged numerical models, a finite difference and a finite element model, is undertaken. From the application of the models to Amvrakikos Gulf, a nearly enclosed coastal water body of particular ecological interest in Western Greece, the following conclusions are drawn. (i) Circulation patterns calculated for the same eddy viscosity coefficient with both models are essentially identical. (ii) Increasing the value of eddy viscosity coefficient results in a significant reduction of the magnitude of the flow velocities with no major changes on the general flow pattern. (iii) Preliminary calculations with the finite difference model show that the incorporation of the k-ε turbulence model has minor effects on the results, but it improves the rate of convergence. (iv) Calculations with both models using alternative conditions in the open sea boundary show only minor differences in the proximity of the boundary.

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