scholarly journals Study on the internal two-phase flow of the inverted-umbrella aerator

2019 ◽  
Vol 11 (8) ◽  
pp. 168781401987173 ◽  
Author(s):  
Liang Dong ◽  
Jiawei Liu ◽  
Houlin Liu ◽  
Cui Dai ◽  
Dmitry Vladimirovich Gradov
Keyword(s):  
Free Surface ◽  
Velocity Distribution ◽  
Surface Deformation ◽  
Two Phase Flow ◽  
Back Surface ◽  
High Speed Photography ◽  
Aeration Tank ◽  
Phase Flow ◽  
Two Phase ◽  
Radial Profiles

In order to reveal the gas–liquid two-phase flow pattern of inverted-umbrella aerator, the high-speed photography technology, particle image velocimetry, and Volume of Fluid model are employed to capture the free-surface dynamics and velocity distribution. The Computational Fluid Dynamics simulations are validated by experimental data and the results are in good agreement with experiment. The simulation results of flow field, streamline distribution, velocity distribution, free-surface deformation, and turbulence kinetic energy are analyzed at in time and at radial profiles sampled at several vertical positions. Back surface of each blade revealed the area of low-pressure, which can drag air into water directly from surface and thus enhance liquid aeration and oxygenation capacity. Lifting capacity of the inverted-umbrella aerator is enough to get the liquid at the bottom of the aeration tank accelerated toward liquid surface generating the hydraulic jump. As a result, liquid phase splashes capture portions of air promoting aeration of the solution. A clear circulation whirlpool is formed during the process. The circulation whirlpool starts at the bottom of the impeller moving upward along the plate until the outer edge of the impeller, which is close to the free surface. The circulation whirlpool indicates that the inverted-umbrella aerator plays a significant role in shallow aeration. The turbulence intensity created by the impeller gradually reduces with depth. The position ( z = 0.65 H) is the watershed in the tank. The oxygen mass transfer mainly occurs in the layer above watershed.

Gradient-Augmented Level Set Two-Phase Flow Method With Pretreated Reinitialization for Three-Dimensional Violent Sloshing

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Jianjian Xin ◽  
Fulong Shi ◽  
Qiu Jin ◽  
Lin Ma
Keyword(s):  
Free Surface ◽  
Level Set ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Surface Shape ◽  
Phase Flow ◽  
Two Phase ◽  
Correction Technique ◽  
Highly Nonlinear ◽  
Violent Sloshing

Abstract A three-dimensional (3D) gradient-augmented level set (GALS) two-phase flow model with a pretreated reinitialization procedure is developed to simulate violent sloshing in a cuboid tank. Based on a two-dimensional (2D) GALS method, 3D Hermite, and 3D Lagrange polynomial schemes are derived to interpolate the level set function and the velocity field at arbitrary positions over a cell, respectively. A reinitialization procedure is performed on a 3D narrow band to treat the strongly distorted interface and improve computational efficiency. In addition, an identification-correction technique is proposed and incorporated into the reinitialization procedure to treat the tiny droplet which can distort the free surface shape, even lead to computation failure. To validate the accuracy of the present GALS method and the effectiveness of the proposed identification-correction technique, a 3D velocity advection case is first simulated. The present method is validated to have better mass conservation property than the classical level set and original GALS methods. Also, distorted and thin interfaces are well captured on all grid resolutions by the present GALS method. Then, sloshing under coupled surge and sway excitation, sloshing under rotational excitation are simulated. Good agreements are obtained when the present wave and pressure results are compared with the experimental and numerical results. In addition, the highly nonlinear free surface is observed, and the relationship between the excitation frequency and the impulsive pressure is investigated.

A Numerical Method for the Analysis of a New Model for Two-Phase Bubbly Flow in Elastic Pipes

2002 ◽  
Author(s):  
D. Kim
Keyword(s):  
Numerical Method ◽  
Surface Deformation ◽  
Two Phase Flow ◽  
Numerical Technique ◽  
Bubbly Flow ◽  
Neumann Boundary ◽  
Phase Flow ◽  
Two Phase ◽  
Tube Cross Section ◽  
Elastic Pipes

A new approach and numerical method for study gas-liquid two-phase flows in elastic pipes is suggested. “A nonlinear wave dynamical model for liquid containing gas bubbles” is applied to derive governing equations for two-phase flow-filled pipelines. On assuming the hydraulic approximation the continuity and momentum equations of two-phase flow in a pipe are obtained for the first time. From these equations the inhomogeneous wave equation of Lighthill-type for two-phase flow in pipelines is derived. The shear stress at the tube surface, deformation of the tube cross-section, and liquid’s phase compressibility are taken into account. A high effectively and accurate finite difference technique for the exact solution of the basic equations in the case of Neumann boundary conditions is developed. Based on the proposed algorithm various numerical experiments have been carried out to investigate the major fluid dynamical features of hydraulic shocks and shock waves in the horizontal pipes. Comparisons with both the experimental data and computational results obtained with a second-order accurate predictor-corrector method support our numerical technique as well as the model.

A Two-Phase Flow Model with VOF for Free Surface Flow Problems

2012 ◽  
Vol 232 ◽  
pp. 279-283 ◽  
Author(s):  
Wei Zhang ◽  
You Hong Tang ◽  
Cheng Bi Zhao ◽  
Cheng Zhang
Keyword(s):  
Free Surface ◽  
Flow Model ◽  
Two Phase Flow ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Phase Model ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Problems ◽  
Fluid Sloshing

A numerical model based on the two-phase flow model for incompressible viscous fluid with a complex free surface has been developed in this study. The two-step projection method is employed to solve the Navier–Stokes equations in the numerical solutions, and finite difference method on a staggered grid is used throughout the computation. The two-order accurate volume of fluid (VOF) method is used to track the distorted and broken free surfaces. The two-phase model is first validated by simulating the dam break over a dry bed, in which the numerical results and experimental data agree well. Then 2-D fluid sloshing in a horizontally excited rectangular tank at different excitation frequencies is simulated using this two-phase model. The results of this study show that the two-phase flow model with VOF method is a potential tool for the simulation of nonlinear fluid sloshing. These studies demonstrate the capability of the two-phase model to simulate free surface flow problems with considering air movement effects.

scholarly journals NUMERICAL MODELLING OF KINEMATICS AND DYNAMICS OF SPILLING AND PLUNGING BREAKERS IN SHALLOW WATERS

2018 ◽  
pp. 4
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
Two Phase Flow ◽  
Staggered Grid ◽  
Shallow Waters ◽  
Phase Flow ◽  
Two Phase ◽  
Linear Interaction ◽  
Water Interaction ◽  
Non Linear

Wave breaking is a complex two-phase flow process that strongly influences the air-water interaction. A number of physical processes are involved in the exchange of mass, momentum and energy between air and water interaction during the wave breaking process. In shallow waters, waves undergo different transformation processes such as shoaling, refraction, diffraction and breaking due to their non-linear interaction with the seabed. Thus, the associated hydrodynamics are rather complicated to understand when compared to wave breaking in deep water (Lin, 2008). In the present numerical study, a two phase flow CFD model REEF3D (Bihs et al. 2016) is used to model and investigate the hydrodynamics of spilling and plunging breakers over a slope. An accurate modeling of the wave breaking process is still highly demanding due to the strong non-linear air-water interaction and turbulent production at the free surface. The numerical wave tank is based on the incompressible Reynolds Averaged Navier-Stokes (RANS) equations together with the level set method for free surface and the k-ω model for turbulence (Alagan Chella et al. 2015). The model uses the 5th-order Weighted Essentially Non- Oscillatory (WENO) scheme for the convective discretization and the 3rd-order TVD Runge Kutta Scheme for the time discretization. A staggered grid method is employed in the model in order to achieve a stronger coupling between the pressure and velocity. The model is fully parallelized with the domain decomposition method and MPI (Message passing interface).

Two Domensional Simulation of Velocity Field of Two-Phase Flow for Gas and Solid in the Abrasive Air Jet Nozzle

2007 ◽  
Vol 359-360 ◽  
pp. 465-469
Author(s):  
Chuan Zhen Huang ◽  
Rong Guo Hou ◽  
Zeng Wen Liu ◽  
Quan Lai Li ◽  
Hong Tao Zhu
Keyword(s):  
Fluid Dynamics ◽  
Velocity Field ◽  
Velocity Distribution ◽  
Radial Direction ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Nozzle Outlet ◽  
Two Phase ◽  
Air Jet ◽  
Jet Nozzle

Simulation on velocity field of gas-solid flow in the abrasive air jet nozzle was studied by the computed fluid dynamics(CFD) software. The velocity field of the two-phase flow in the abrasive air jet nozzle can be obtained by means of simulation. The effect of the nozzle diameter on the velocity field shows that the velocity field in the nozzle with a smaller diameter is more well-distributed. The velocity distribution along the nozzle axis and the radial direction of the nozzle outlet was also simulated.

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