A New Cavitation Model Based on Evaporation and Condensation Theory

2009 ◽  
Author(s):  
Gang Chen ◽  
Shuhong Liu ◽  
Guangjun Cao ◽  
Yulin Wu ◽  
Suhong Fu ◽  
...  
Keyword(s):  
Surface Tension ◽  
Aerodynamic Drag ◽  
Water Pressure ◽  
Bubble Diameter ◽  
Simulation Models ◽  
Cavitation Model ◽  
Local Pressure ◽  
Two Phase ◽  
Evaporation And Condensation ◽  
Model Based

Cavitation is a phenomenon which occurs where the local pressure falls off under the vapor pressure. Over the past few years, numerical simulation models for cavitation have been developed significantly in order to investigate the mechanism of cavitation. In the paper, A local homogeneous cavitation model based on the theory of evaporation and condensation has been deduced, which is used to describe the phase change between water and vapor. The RNG k–ε turbulence model is used to simulate the turbulent flow and the finite volume method is employed to discrete the governing equations. The effects of surface tension of water, pressure fluctuations and non-condensable gases are included in the mass transfer cavitation model. Also in order to neglect the effects of the quantities such as the bubble number and bubble diameter, which is difficult to measure, the relations between the aerodynamic drag and surface tension forces is used to describe the bubble diameter. In order to evaluate the new cavitation model, the two phase cavitation flows around a NACA0015 hydrofoil at different attack angle and different cavitation number are simulated by the new cavitation model, and compared with references, which showed good agreement with the experiments.

scholarly journals Hydraulic Transients Induced by Pigging Operation in Pipeline with a Long Slope

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Tao Deng ◽  
Jing Gong ◽  
Haihao Wu ◽  
Yu Zhang ◽  
Siqi Zhang ◽  
...  
Keyword(s):  
Field Data ◽  
Water Pressure ◽  
Severe Damage ◽  
Cavitation Model ◽  
Two Phase ◽  
Vapor Cavity ◽  
The Third ◽  
Simulation Results ◽  
Water Pressure Testing ◽  
Good Agreement

Pigging in pipelines basically performs operations for five reasons including cleaning the pipe interior, batching or separating dissimilar products, displacement, measurement, and internal inspection. A model has been proposed for the dynamic simulation of the pigging process after water pressure testing in a long slope pipeline. In this study, an attempt has been made to analyze two serious accidents during pigging operation in 2010 by the model which is developed by the method of characteristic (MOC) by Wylie et al. (1993) and the two-phase homogeneous equilibrium vaporous cavitation model deveoped by Shu (2003) for vaporous cavitation. Moreover, simulation results of the third operation show good agreement with field data from the previous field trial. After investigation, it was showed that the impulse pressures produced during collapse of a vapor cavity result in severe damage of tubes.

UNSTEADY CAVITATION SIMULATION IN TRANSIENT PROCESS OF TURBINE FLOW METER

2010 ◽  
Vol 24 (13) ◽  
pp. 1503-1506 ◽  
Author(s):  
GANG CHEN ◽  
SHUHONG LIU ◽  
GUANGJUN CAO
Keyword(s):  
Source Terms ◽  
Governing Equations ◽  
Local Pressure ◽  
Flow Meter ◽  
Two Phase ◽  
Rotating Speed ◽  
Evaporation And Condensation ◽  
Liquid Products ◽  
The Given ◽  
Turbine Flow Meter

In a turbine flow meter, cavitation will take place when local pressure falls below the vapor pressure of liquid products and it usually speeds up the rotor at the given high flow rate. In order to study its effects on meter factor, numerical simulation on transient unsteady turbulent flow is carried out based on the mixture homogeneous two phase cavitation model which is deduced from the theory of evaporation and condensation on a plane. The momentum source terms from the variation rotating speed of transient processes and the cavitation mass transport source terms are introduced into the transient unsteady governing equations. The results show that the meter factor grows with the increase of the cavitation number and meter factor will be affected by cavitation.

Numerical modeling of the influence of bubbles on flow and heat transfer in the descending gas-liquid flow in a pipe

2012 ◽  
Vol 9 (1) ◽  
pp. 131-135
Author(s):  
M.A. Pakhomov
Keyword(s):  
Heat Transfer ◽  
Gas Phase ◽  
Liquid Flow ◽  
Bubble Diameter ◽  
Gas Content ◽  
Two Phase ◽  
Eulerian Description ◽  
Flow And Heat Transfer ◽  
Gas Liquid Flow ◽  
The Mathematical Model

The paper presents the results of modeling the dynamics of flow, friction and heat transfer in a descending gas-liquid flow in the pipe. The mathematical model is based on the use of the Eulerian description for both phases. The effect of a change in the degree of dispersion of the gas phase at the input, flow rate, initial liquid temperature and its friction and heat transfer rate in a two-phase flow. Addition of the gas phase causes an increase in heat transfer and friction on the wall, and these effects become more noticeable with increasing gas content and bubble diameter.

Nanometer-Sized Water Bridge and Pull-Off Force in AFM at Different Relative Humidities: Reproducibility Measurement and Model Based on Surface Tension Change

2017 ◽  
Vol 121 (3) ◽  
pp. 610-619 ◽  
Author(s):  
Miroslav Bartošík ◽  
Lukáš Kormoš ◽  
Lukáš Flajšman ◽  
Radek Kalousek ◽  
Jindřich Mach ◽  
...  
Keyword(s):  
Surface Tension ◽  
Water Bridge ◽  
Model Based ◽  
Tension Change ◽  
Surface Tension Change

Study on C–S and P–R EOS in pseudo-potential lattice Boltzmann model for two-phase flows

2017 ◽  
Vol 28 (09) ◽  
pp. 1750120 ◽  
Author(s):  
Yong Peng ◽  
Yun Fei Mao ◽  
Bo Wang ◽  
Bo Xie
Keyword(s):  
Surface Tension ◽  
Lattice Boltzmann ◽  
Equations Of State ◽  
Density Ratio ◽  
Maximum Density ◽  
Lattice Boltzmann Model ◽  
Two Phase Flows ◽  
Two Phase ◽  
Spurious Currents ◽  
Pseudo Potential

Equations of State (EOS) is crucial in simulating multiphase flows by the pseudo-potential lattice Boltzmann method (LBM). In the present study, the Peng and Robinson (P–R) and Carnahan and Starling (C–S) EOS in the pseudo-potential LBM with Exact Difference Method (EDM) scheme for two-phase flows have been compared. Both of P–R and C–S EOS have been used to study the two-phase separation, surface tension, the maximum two-phase density ratio and spurious currents. The study shows that both of P–R and C–S EOS agree with the analytical solutions although P–R EOS may perform better. The prediction of liquid phase by P–R EOS is more accurate than that of air phase and the contrary is true for C–S EOS. Predictions by both of EOS conform with the Laplace’s law. Besides, adjustment of surface tension is achieved by adjusting [Formula: see text]. The P–R EOS can achieve larger maximum density ratio than C–S EOS under the same [Formula: see text]. Besides, no matter the C–S EOS or the P–R EOS, if [Formula: see text] tends to 0.5, the computation is prone to numerical instability. The maximum spurious current for P–R is larger than that of C–S. The multiple-relaxation-time LBM still can improve obviously the numerical stability and can achieve larger maximum density ratio.

Neural Network Based Control of Preform Permeation in Resin Transfer Molding Processes With Real-Time Permeability Estimation

2000 ◽  
Author(s):  
David Nielsen ◽  
Ranga Pitchumani
Keyword(s):  
Neural Network ◽  
Real Time ◽  
Resin Transfer Molding ◽  
Local Pressure ◽  
Transfer Molding ◽  
Model Based ◽  
Rtm Process ◽  
Virtual Sensing ◽  
Intelligent Model ◽  
Injection Pressures

Abstract Variabilities in the preform structure in situ in the mold are an acknowledged challenge to effective permeation control in the Resin Transfer Molding (RTM) process. An intelligent model-based controller is developed which utilizes real-time virtual sensing of the permeability to derive optimal decisions on controlling the injection pressures at the mold inlet ports so as to track a desired flowfront progression during resin permeation. This model-based optimal controller employs a neural network-based predictor that models the flowfront progression, and a simulated annealing-based optimizer that optimizes the injection pressures used during actual control. Preform permeability is virtually sensed in real-time, based on the flowfront velocities and local pressure gradient estimations along the flowfront. Results are presented which illustrate the ability of the controller in accurately steering the flowfront for various fill scenarios and preform geometries.

Effects of Surface Tension and Bubble Diameter on Bubble Breakage Time under Microgravity

2005 ◽  
Vol 31 (1) ◽  
pp. 84-88 ◽  
Author(s):  
Yuichi Ohira ◽  
Jun Amanai ◽  
Yoshikazu Kuga ◽  
Kiyoshi Idogawa ◽  
Eiji Obata ◽  
...  
Keyword(s):  
Surface Tension ◽  
Bubble Diameter

scholarly journals A new cavitation model based on bubble-bubble interactions

2018 ◽  
Vol 30 (12) ◽  
pp. 123301 ◽  
Author(s):  
M. Adama Maiga ◽  
O. Coutier-Delgosha ◽  
D. Buisine
Keyword(s):  
Cavitation Model ◽  
Bubble Interactions ◽  
Model Based

Experiment and Dynamic Simulation of PIG Motion during Pigging Operation in a Slope Pipeline

2018 ◽  
Vol 16 (9) ◽  
Author(s):  
Jun Zhou ◽  
Tao Deng ◽  
Guangchuan Liang ◽  
Jinghong Peng ◽  
Tian Meng ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Water Pressure ◽  
Oil And Gas Industry ◽  
Unsteady Motion ◽  
Stable Operation ◽  
Two Phase ◽  
Transient Model ◽  
Water Pressure Test ◽  
Pressure Test ◽  
Hydraulic Pulse

Abstract Pigging techniques are widely used in the oil and gas industry. The unsteady motion of the PIG in an undulating pipe section during the pigging process after a water pressure test affects the stable operation of the pipeline and also causes a pipe rupture accident in serious cases. First, an experimental study was conducted to investigate the pigging process of air–water two phase pipe flows, and the PIG reverse movement and hydraulic pulse phenomenon were observed. Subsequently, a hydraulic transient model of the pigging process after a water pressure test was established in a dual-grid system. The model combined mass and motion equations of gas and liquid and PIG dynamic equations, considered three types of PIG motion states, namely positive movement, reverse movement and still, and used the method of characteristics to solve the equations. The model exhibits the ability for PIG tracing and hydraulic pulse prediction. It can be used to obtain the position and speed of the PIG. Finally, the field data and simulation results were compared, and the results indicated that they are essentially identical. This verified the accuracy of the model that is established in this study and the reliability of computed results and provided a reliable and effective theoretical basis for the development of field pigging plans.

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