K. Ibrahim¹, W.A. El-Askary^1,2, A. Balabel¹, I.M. Sakr¹

CMES-Computer Modeling in Engineering & Sciences, Vol.85, No.1, pp. 79-104, 2012, DOI:10.3970/cmes.2012.085.079

Abstract In the present paper, a numerical code has been developed with different turbulence models aiming at simulating turbulent bubbly flows in vertical circular pipes. The mass and momentum conservation equations are used to describe the motion of both phases (water/air). Because of the averaging process additional models are needed for the inter-phase momentum transfer and turbulence quantities for closure. The continuous phase (water) turbulence is represented using different turbulence models namely: two-equation k-ε, extended k-ε and shear-stress transport (SST) k-ω turbulence models which contains additional term to account for the effect of the dispersed phase… More >

Ashraf Balabel

CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.6, pp. 599-638, 2012, DOI:10.3970/cmes.2012.083.599

Abstract In the present paper, a new generalized level set numerical method based on the Fast Marching Method is developed for predicting the moving interface thermo-fluid dynamics in turbulent free surface flows. The numerical method is devoted to predict the turbulent interfacial dynamics resulting from either aerodynamic force or thermocapillary effects. The unsteady Reynolds averaged Navier-Stokes equations (RANS) and energy equation are coupled with the level set method and solved separately in each phase using the finite volume method on a non-staggered grid system. The application of the fast marching technique enables the fast as well… More >

A. Belcaid^1,2, G. Le Palec², A. Draoui¹, Ph. Bournot¹

FDMP-Fluid Dynamics & Materials Processing, Vol.8, No.2, pp. 241-256, 2012, DOI:10.3970/fdmp.2012.008.241

Abstract The study is focused on numerical simulation of the process of coastal pollution by wastewater in the Bay of Tangier in Morocco. The process is governed by flows generated by the tide and the large variations of the discharges from the different Wadis (rivers) flowing into the bay. The simulation requires a number of tests and trials, something that is experimentally expensive and sometimes impossible. Hence the idea was developed of a numerical study aimed at tracking the dispersion of pollutants into the bay and determining the level of degradation of its waters. The simulation… More >

T. Watanabe, T.Gotoh

The International Conference on Computational & Experimental Engineering and Sciences, Vol.18, No.3, pp. 91-92, 2011, DOI:10.3970/icces.2011.018.091

Abstract The effects of polymer additives on decaying isotropic turbulence were numerically investigated using a hybrid approach. The approach consisted of a Brownian dynamics simulation with an enormous number of dumbbells and a turbulence DNS with large-scale parallel computations. A reduction of the energy dissipation rate and modification of the kinetic energy spectrum were observed when the reactions of the polymers were incorporated into the fluid motion. We found that results with few polymers and large replicas could approximate those with many polymers and smaller replicas as far as the large-scale statistics were concerned. More >

L.Q. Moreira¹, F.P. Mariano², A. Silveira-Neto¹

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.2, pp. 113-140, 2011, DOI:10.3970/cmes.2011.075.113

Abstract Turbulence in fluid flow is one of the most challenging problems in classical physics. It is a very important research problem because of its numerous implications, such as industrial applications that involve processes using mixtures of components, heat transfer and lubrication and injection of fuel into the combustion chambers and propulsion systems of airplanes. Turbulence in flow presents characteristics that are fully nonlinear and that occur at high Reynolds numbers. Because of the nonlinear nature of turbulent flow, an increase in the Reynolds number implies an increase in the Kolmogorov wave numbers, and the flow… More >

W.A. El-Askary^1,2, A. Balabel², S.M. El-Behery², A. Hegab³

CMES-Computer Modeling in Engineering & Sciences, Vol.82, No.1, pp. 29-54, 2011, DOI:10.32604/cmes.2011.082.029

Abstract In the present paper, the characteristics of compressible turbulent flow in a porous channels subjected to either symmetric or asymmetric mass injection are numerically predicted. A numerical computer-program including different turbulence models has been developed by the present authors to investigate the considered flow. The numerical method is based on the control volume approach to solve the governing Reynolds-Averaged Navier-Stokes (RANS) equations. Turbulence modeling plays a significant role here, in light of the complex flow generated, so several popular engineering turbulence models with good track records are evaluated, including five different turbulence models. Numerical results… More >

Zhi Yuan Cui¹, Jiu Hui Wu¹, Di Chen Li¹

CMES-Computer Modeling in Engineering & Sciences, Vol.71, No.2, pp. 149-156, 2011, DOI:10.3970/cmes.2011.071.149

Abstract A quantitative rule of the vibrated granular media's energy dissipation is obtained by adopting the turbulence theory in this letter. Our results show that, similar to the power spectrum in fully developed fluid turbulence as described in Kolmogorov's theory, the power spectrum of vibrated granular media also exhibits a k - 5 / 3 (k is the wave number) power which characterizes the local isotropic flow. What's more, the mean energy dissipation rate in vibrated granular media rises with the increase of particle size and volume ratio. The theoretical results in this letter can be More >

Sung-Eun Kim¹, Shin Hyung Rhee²

CMES-Computer Modeling in Engineering & Sciences, Vol.62, No.3, pp. 291-310, 2010, DOI:10.3970/cmes.2010.062.291

Abstract Turbulent flow past a finite wing has been computed to assess the fidelity of modern computational fluid dynamics in predicting tip vortex flows. The efficacy of a feature-adaptive local mesh refinement to resolve the steep gradients in the flow field near the tip vortex is demonstrated. The impact of turbulence modeling is evaluated using several popular eddy viscosity models and a Reynolds stress transport model. The results indicate that the combination of a computational mesh with an adequate resolution, high-order spatial discretization scheme along with the use of advanced turbulence models can predict tip vortex More >

A. Benaissa¹, I. Yimer²

FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.2, pp. 203-218, 2010, DOI:10.3970/fdmp.2010.006.203

Abstract This work presents a study on the effect of pulsing on a jet flow. Pulsing is used to modify jet inlet conditions with the objective of improving mixing. In this experimental work, a jet was slightly heated so that temperature could be considered as a passive scalar. The spectral behaviour of velocity and the passive scalar temperature was analyzed along the jet axis with and without pulsing. Low frequency pulsing (f/fS< 0.05 fSthe Strouhal frequency) modifies the spectral composition of the velocity at the jet exit, but it does not affect the asymptotic profile reached… More >

R. Vertnik¹, B. Šarler²

CMES-Computer Modeling in Engineering & Sciences, Vol.44, No.1, pp. 65-96, 2009, DOI:10.3970/cmes.2009.044.065

Abstract The application of the mesh-free Local Radial Basis Function Collocation Method (LRBFCM) in solution of incompressible turbulent flow is explored in this paper. The turbulent flow equations are described by the low - Re number k-emodel with Jones and Launder [Jones and Launder (1971)] closure coefficients. The involved velocity, pressure, turbulent kinetic energy and dissipation fields are represented on overlapping 5-noded sub-domains through collocation by using multiquadrics Radial Basis Functions (RBF). The involved first and second derivatives of the fields are calculated from the respective derivatives of the RBF's. The velocity, turbulent kinetic energy and… More >