Calculation of Wall-Bounded Complex Flows and Free Shear Flows

The standard -model has the deficiency of predicting swirling and vortical flows due to its isotropic assumption of eddy viscosity. In this study, a second-order nonlinear -model is developed incorporating some new functions for the model coefficients to explore the models applicability to complex turbulent flows. Considering the realizability principle, the coefficient of eddy viscosity ( ) is derived as a function of strain and rotation parameters. The coefficients of nonlinear quadratic term are estimated considering the anisotropy of turbulence in a simple shear layer. Analytical solutions for the fundamental properties of swirl jet are derived based on the nonlinear -model, and the values of model constants are determined by tuning their values for the best-fitted comparison with the experiments. The model performance is examined for two test cases: (i) for an ideal vortex (Stuart vortex), the basic equations are solved numerically to predict the turbulent structures at the vortex center and the (ii) unsteady 3D simulation is carried out to calculate the flow field of a compound channel. It is observed that the proposed nonlinear -model can successfully predict the turbulent structures at vortex center, while the standard -model fails. The model is found to be capable of accounting the effect of transverse momentum transfer in the compound channel through generating the horizontal vortices at the interface.

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“…turbulence model equation should obey [12]. The realizability inequalities for 3D turbulent flows are as follows:…”

Section: Consideration Of Realizability For Plane Shear Layermentioning

confidence: 99%

Development of a Nonlinear k-ε Model Incorporating Strain and Rotation Parameters for Prediction of Complex Turbulent Flows

Ali

Hosoda

Kimura

2015

International Journal of Partial Differential Equations

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“…In this work, a model developed by Shih et al (1996) is used, which relates the mean strain rate of the flow to the Reynolds stress tensor through the algebraic nonlinear Reynolds stress model. The model adjusts the Reynolds stress, τ, by adding a nonlinear stress term τ NL , defined as…”

Section: Nonlinear (Nl)mentioning

confidence: 99%

“…Shih et al (1996) showed the nonlinear k − ǫ model performs better than the standard k − ǫ model under strong adverse pressure gradients, as well as for separated and swirling flows.…”

Section: Introductionmentioning

confidence: 99%

“…In this study, the validity of the isotropic assumption is considered by using a nonlinear k − ǫ model developed by Shih et al (1996), which accounts for anisotropic effects by introducing a nonlinear Reynolds stress term into the standard k − ǫ model. Shih et al (1996) showed the nonlinear k − ǫ model performs better than the standard k − ǫ model under strong adverse pressure gradients, as well as for separated and swirling flows.…”

Section: Introductionmentioning

confidence: 99%

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An Evaluation of Rans Turbulence Closure Models for Spilling Breakers

Brown

Magar²,

Greaves

et al. 2014

Int. Conf. Coastal. Eng.

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1Breaking waves generate turbulence which, along with the bottom stress, undertow, and other mean currents, is capable of suspending and transporting large quantities of sediment. In the present work, open source computational fluid dynamics software is utilised to evaluate four different turbulence models for the application of spilling breakers in the surf zone. The turbulence models are compared against both existing laboratory data and previous numerical models for surface elevation, velocity and turbulent kinetic energy profiles. The results imply that the different models vary in performance for each of these properties and that for incompressible, multiphase flows, it is important to include density explicitly in the turbulence transport equations. Overall, it was found that, out of the models considered, the best one for spilling breakers is the nonlinear k − ǫ model.

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“…is calculated with a nonlinear eddy viscosity relationship suggested by Shih et al 1996. This nonlinear closure relationship for Reynolds stress mimics the more complete Reynolds-stress closure without solving the transport equations of Reynolds stress.…”

Section: Numerical Modelmentioning

confidence: 99%

Numerical and Experimental Study of Dam-Break Flood Propagation and Its Implication to Sediment Erosion

Hsu¹,

Torres-Freyermuth²,

Hsu³

et al. 2012

Int. Conf. Coastal. Eng.

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Regarding the hydrodynamics, within the past two decades it has become popular in numerical modeling of freesurface flow to adopt a Reynolds-averaged Navier-Stokes approach, where the volume of fluid (VOF) method is utilized to track the evolution of free-surface. However, this robust numerical model has not been widely applied to the study of sediment transport processes. In this study, we shall extend the numerical model to simulate suspended sediment transport and study the erosion pattern during the initial stage of the dam break flow. We also conducted a series of experiments in a horizontal channel of rectangular section and recorded the snap shots of surface profiles of a dam-break wave during the initial stage of dam-break. Measured data is utilized here to study the hydrodynamics and to validate the numerical model.

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Calculation of Wall-Bounded Complex Flows and Free Shear Flows

Cited by 54 publications

References 13 publications

Development of a Nonlinear k-ε Model Incorporating Strain and Rotation Parameters for Prediction of Complex Turbulent Flows

Development of a Nonlinear k-ε Model Incorporating Strain and Rotation Parameters for Prediction of Complex Turbulent Flows

An Evaluation of Rans Turbulence Closure Models for Spilling Breakers

Numerical and Experimental Study of Dam-Break Flood Propagation and Its Implication to Sediment Erosion

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