Statistical Modeling of Stratified Two-Phase Flow

2017 ◽  
Vol 3 (2) ◽  
Author(s):  
M. Benz ◽  
T. Schulenberg
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulence Model ◽  
Input Parameter ◽  
Wave Number ◽  
Energy Potential ◽  
Two Phase ◽  
Turbulent Length Scale ◽  
Inner Region ◽  
Velocity Turbulence

A new numerical model for stratified two-phase flows with wavy interface is derived in this study. Assuming an equilibrium condition between turbulent kinetic energy, potential energy, and surface energy, the turbulent length scale in the inner region of a two-layer turbulence approach can be described by a statistical model to account for the influence of the waves. The average wave number, which is an input parameter to this model, is taken from wave spectra. They can be predicted from a Boltzmann statistic of turbulent kinetic energy. The new turbulence model is compared with the two-phase k–ϵ turbulence model. Time-averaged flow properties calculated by the new approach, such as velocity, turbulence, and void profiles, are shown to be in good agreement with experimental data.

Numerical Simulation of Gas-Particle Turbulent Flow Using kg-εg -kp-εp-kpg-θ Turbulence Model

2012 ◽  
Vol 204-208 ◽  
pp. 4327-4331 ◽  
Author(s):  
Zhuo Xiong Zeng ◽  
Feng Xue ◽  
Yi Hua Xu
Keyword(s):  
Kinetic Energy ◽  
Phase Velocity ◽  
Turbulent Kinetic Energy ◽  
Turbulence Model ◽  
Present Model ◽  
Particle Interaction ◽  
Particle Collision ◽  
Sudden Expansion ◽  
Velocity Correlation ◽  
Two Phase

kg-εg-kp-εp-kpg-θ turbulence model is proposed which considers particle-particle collision and gas-particle turbulence. This model includes turbulent kinetic energy equation, turbulent kinetic energy dissipation rate equation, particle pseudo-temperature transportation equation and the two-phase velocity correlation transport equation. To close the turbulence model, algebraic expressions of two-phase Reynolds stresses and two-phase velocity correlation variable are established which considered both gas-particle interaction and anisotropy. This model is used to simulate gas-particle in swirling sudden-expansion chamber. Comparing with kg-εg-kp-εp-θ model which is simply closed using a semi-empirical dimensional analysis, the present model has better predicted capability. It is shown that the present model gives simulation results in much better agreement with the experimental results than the kg-εg-kp-εp-θ model.

A Nonlinear k-ε-kp Two-Phase Turbulence Model

2003 ◽  
Vol 125 (1) ◽  
pp. 191-194 ◽  
Author(s):  
L. X. Zhou ◽  
H. X. Gu
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulence Model ◽  
Computation Time ◽  
Second Order ◽  
Phase Correlation ◽  
Order Moment ◽  
Reynolds Stresses ◽  
Two Phase ◽  
Particle Flows

Nonlinear relationships of two-phase Reynolds stresses with the strain rates together with the transport equations of gas and particle turbulent kinetic energy and the two-phase correlation turbulent kinetic energy are proposed as the nonlinear k-ε-kp turbulence model. The proposed model is applied to simulate swirling gas-particle flows. The predicted two-phase time-averaged velocities and Reynolds stresses are compared with the PDPA measurements and those predicted using the second-order moment model. The results indicate that the nonlinear k-ε-kp model has the modeling capability near to that of the second-order moment model, but the former can save much computation time than the latter.

scholarly journals Development of a two zone turbulence model and its application to the cycle-simulation

2014 ◽  
Vol 18 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Momir Sjeric ◽  
Darko Kozarac ◽  
Rudolf Tomic
Keyword(s):  
High Pressure ◽  
Kinetic Energy ◽  
Flow Field ◽  
Turbulent Kinetic Energy ◽  
Turbulence Model ◽  
Combustion Process ◽  
Progress Variable ◽  
Cycle Simulation ◽  
Pressure Cycle ◽  
Turbulent Flow Field

The development of a two zone k-? turbulence model for the cycle-simulation software is presented. The in-cylinder turbulent flow field of internal combustion engines plays the most important role in the combustion process. Turbulence has a strong influence on the combustion process because the convective deformation of the flame front as well as the additional transfer of the momentum, heat and mass can occur. The development and use of numerical simulation models are prompted by the high experimental costs, lack of measurement equipment and increase in computer power. In the cycle-simulation codes, multi zone models are often used for rapid and robust evaluation of key engine parameters. The extension of the single zone turbulence model to the two zone model is presented and described. Turbulence analysis was focused only on the high pressure cycle according to the assumption of the homogeneous and isotropic turbulent flow field. Specific modifications of differential equation derivatives were made in both cases (single and two zone). Validation was performed on two engine geometries for different engine speeds and loads. Results of the cyclesimulation model for the turbulent kinetic energy and the combustion progress variable are compared with the results of 3D-CFD simulations. Very good agreement between the turbulent kinetic energy during the high pressure cycle and the combustion progress variable was obtained. The two zone k-? turbulence model showed a further progress in terms of prediction of the combustion process by using only the turbulent quantities of the unburned zone.

scholarly journals Discussion on improved method of turbulence model for supercritical water flow and heat transfer

2020 ◽  
Vol 24 (5 Part A) ◽  
pp. 2729-2741
Author(s):  
Zhenchuan Wang ◽  
Guoli Qi ◽  
Meijun Li
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulence Model ◽  
Buoyancy Effect ◽  
Improved Method ◽  
Production Term ◽  
Flow And Heat Transfer ◽  
Effect Model

The turbulence model fails in supercritical fluid-flow and heat transfer simulation, owing to the drastic change of thermal properties. The inappropriate buoyancy effect model and the improper turbulent Prandtl number model are several of these factors lead to the original low-Reynolds number turbulence model unable to predict the wall temperature for vertically heated tubes under the deteriorate heat transfer conditions. This paper proposed a simplified improved method to modify the turbulence model, using the generalized gradient diffusion hypothesis approximation model for the production term of the turbulent kinetic energy due to the buoyancy effect, using a turbulence Prandtl number model for the turbulent thermal diffusivity instead of the constant number. A better agreement was accomplished by the improved turbulence model compared with the experimental data. The main reason for the over-predicted wall temperature by the original turbulence model is the misuse of the buoyancy effect model. In the improved model, the production term of the turbulent kinetic energy is much higher than the results calculated by the original turbulence model, especially in the boundary-layer. A more accurate model for the production term of the turbulent kinetic energy is the main direction of further modification for the low Reynolds number turbulence model.

Heat Transfer Predictions With Extended k–ε Turbulence Model in Radial Cooling Ducts Rotating in Orthogonal Mode

1994 ◽  
Vol 116 (2) ◽  
pp. 369-380 ◽  
Author(s):  
P. Tekriwal
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulence Model ◽  
Rotation Number ◽  
Density Ratio ◽  
Rotating Systems ◽  
Model Predictions ◽  
Number Flow

Standard and extended k–ε turbulence closure models have been employed for three-dimensional heat transfer calculations for radially outward flow in rectangular and square cooling passages rotating in orthogonal mode. The objective of this modeling effort is to validate the numerical model in an attempt to fill the gap between model predictions and the experimental data for heat transfer in rotating systems. While the trend of heat transfer predictions by the standard k–ε turbulence model is satisfactory, the differences between the data and the predictions are approximately 30 percent or so in the case of high rotation number flow. The extended k–ε turbulence model takes an approach where an extra “source” term based on a second time scale of the turbulent kinetic energy production rate is added to the equation for the dissipation rate of turbulent kinetic energy. This yields a more effective calculation of turbulent kinetic energy as compared to the standard k–ε turbulence model in the case of high rotation number and high density ratio flow. As a result, comparison with the experimental data available in the literature shows that an improvement of up to a significant 15 percent (with respect to data) in the heat transfer coefficient predictions is achieved over the standard k–ε model in the case of high rotation number flow. Comparisons between the results of the standard k–ε model and the extended formulation are made at different rotation numbers, different Reynolds numbers, and varying temperature ratio. The results of the extended k–ε turbulence model are either as good or better than those of the standard k–ε model in all these cases of parametric study. Thus, the extended k–ε turbulence model proves to be more general and reduces the discrepancy between the model predictions and the experimental data for heat transfer in rotating systems.

A K—ε—γ equation turbulence model

1992 ◽  
Vol 237 ◽  
pp. 301-322 ◽  
Author(s):  
Ji Ryong Cho ◽  
Myung Kyoon Chung
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbulence Model ◽  
Mixing Layer ◽  
Spreading Rate ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Model Equations ◽  
Entrainment Effect ◽  
Intermittency Factor

By considering the entrainment effect on the intermittency in the free boundary of shear layers, a set of turbulence model equations for the turbulent kinetic energy k, the dissipation rate ε, and the intermittency factor γ is proposed. This enables us to incorporate explicitly the intermittency effect in the conventional K–ε turbulence model equations. The eddy viscosity νt is estimated by a function of K, ε and γ. In contrast to the closure schemes of previous intermittency modelling which employ conditional zone averaged moments, the present model equations are based on the conventional Reynolds averaged moments. This method is more economical in the sense that it halves the number of partial differential equations to be solved. The proposed K–ε–γ model has been applied to compute a plane jet, a round jet, a plane far wake and a plane mixing layer. The computational results of the model show considerable improvement over previous models for all these shear flows. In particular, the spreading rate, the centreline mean velocity and the profiles of Reynolds stresses and turbulent kinetic energy are calculated with significantly improved accuracy.

A CFD Methodology for Solid and Liquid Flow Fields of Sedimentation Tanks

2012 ◽  
Vol 178-181 ◽  
pp. 371-375
Author(s):  
Y. L. Liu ◽  
Y. Zheng ◽  
P. Zhang ◽  
W.L. Wei
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Dissipation Rate ◽  
Concentration Distribution ◽  
Energy Dissipation Rate ◽  
Two Phase ◽  
Sedimentation Tank ◽  
Solid Distribution ◽  
Solid Liquid

In this paper, the CFD approach is used to study the solid–liquid two-phase turbulent flow and sludge concentration distribution in a secondary sedimentation tank. By the simulation, the velocity and the turbulent kinetic energy and turbulent kinetic energy dissipation rate and solid distribution in a secondary sedimentation tank are obtained, which shows the simulation model is an effective method to investigate the flow patterns and their influence on the process inside the sedimentation vessel.

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