Analysis the Response of Aerated Flow Depth to the VOF Model

2014 ◽  
Vol 716-717 ◽  
pp. 767-770
Author(s):  
Hong Qing Zhang ◽  
Yi Long Lou ◽  
Qian Zhao ◽  
Wei Kai Tan
Keyword(s):  
Water Depth ◽  
Empirical Formula ◽  
Maximum Deviation ◽  
Flow Depth ◽  
Turbulent Model ◽  
Aerated Flow ◽  
Vof Model ◽  
High Head ◽  
Spillway Tunnel ◽  
Large Discharge

In order to analysis the response of aerated flow depth to the VOF model, in this paper, we used VOF combining turbulent model to simulate aerated flow depth in a hydropower station spillway tunnel with high head and large discharge in China. The results show that aerated flow depth is slightly larger than the experiment water depth, but the maximum deviation are not greater than 5% (except the pile number 0+605.236 m). So, using empirical formula to converse the calculate value of water depth into aerated flow depth can make up for the defects of the VOF model which cannot directly get aerated flow depth of the cross section inside the spillway tunnel. But the section water depth can’t be obtained by empirical formula calculation value conversion when cavity exists in the spillway tunnel.

Numerical Simulation of Ventilation Characteristics in a Hydropower Station Spillway Tunnel with High Head and Large Discharge

2014 ◽  
Vol 926-930 ◽  
pp. 3527-3530
Author(s):  
Hong Qing Zhang ◽  
Yi Long Lou ◽  
Wei Ping Xing ◽  
Jun Jun Tan
Keyword(s):  
Wind Speed ◽  
Hydropower Station ◽  
Aerated Flow ◽  
Speed Distribution ◽  
Vof Model ◽  
High Head ◽  
Spillway Tunnel ◽  
The Right ◽  
Ventilation Hole ◽  
Large Discharge

High wind speedandloudnoise usually occur in the hydropower station spillway tunnel, which will impact the producing environment of operators. In this paper, turbulent model and VOF modelwere combinedto simulate wind speed and the volume of ventilated airin ventilation holeandthreeaeratorsin the spillway tunnel on the right bank of a hydropower station in China. The results show thatVOF modelcan well simulate ventilated air induced by water drag, andthe volume of ventilated air in ventilation hole is the largest.Wind speed distribution on the longitudinal sectionof the inlet of ventilation hole is non-uniform,and loud noisewill occurthere. Wind speed on the left side of three aerators is higher than that on the right side. The results of the volume of ventilated airin threeaerators simulated by VOF modelare credible, but we should improve the VOF model to more accurately simulate aerated flow.

Pressure Distribution of Pressure and Non-Pressure Sections of a Hydropower Station Spillway Tunnel

2014 ◽  
Vol 716-717 ◽  
pp. 244-247
Author(s):  
Hong Qing Zhang ◽  
Wei Kai Tan ◽  
Yi Long Lou ◽  
Qian Zhao
Keyword(s):  
Pressure Distribution ◽  
Model Experiment ◽  
Hydropower Station ◽  
Maximum Pressure ◽  
Turbulent Model ◽  
Sudden Drop ◽  
Sudden Enlargement ◽  
High Head ◽  
Spillway Tunnel ◽  
Large Discharge

In this paper, we used VOF combining turbulent model to simulate pressure distribution of pressure section and non-pressure section in a hydropower station spillway tunnel with high head and large discharge in China. The results show that in the pressure section of the spillway tunnel, the values of pressure of emergency gate slot, working gate and the pressing slope, getting from physical model experiment and numerical simulation, are all positive. While in the non-pressure section, the No.1、2、3 aerators of the sudden enlargement and sudden drop occur the maximum pressure. And at the back of the No.1、2、3 aerators, where the values of pressure are negative, forms cavity. The conclusions obtained can improve the design of spillway tunnel.

Study on Flow Characteristics inside a Spillway Tunnel of Hydropower Station

2014 ◽  
Vol 716-717 ◽  
pp. 219-222
Author(s):  
Hong Qing Zhang ◽  
Bing Cao ◽  
Yi Long Lou ◽  
Wei Kai Tan
Keyword(s):  
Flow Velocity ◽  
High Speed ◽  
Flow Characteristic ◽  
Flow Characteristics ◽  
Hydropower Station ◽  
Turbulent Model ◽  
Cross Sectional ◽  
Vof Model ◽  
Spillway Tunnel ◽  
The Right

VOF model and turbulent model were used in this paper to study on flow characteristic inside a certain spillway tunnel of hydropower station, which includes cross sectional distributions of flow velocity in pressure section and non-pressure section. The results show that flow velocity distribution in the pressure section of the spillway tunnel is basically symmetrical. After turning, flow velocity is well-distributed and move ahead; flow velocity in the right side of non-pressure section in the spillway tunnel is 1m/s faster than that in the left side. When two high-speed water flow come together after passing through the central division pier, flow velocity distributions in the both sides of the spillway tunnel are all uniform. The conclusions obtained can improve the design of the spillway tunnel.

Comparative Analysis of Wind Speed in Ventilation Hole Simulated by VOF and Euler Model

2014 ◽  
Vol 624 ◽  
pp. 643-646
Author(s):  
Hong Qing Zhang ◽  
Xian Tang Zhang ◽  
Yi Long Lou ◽  
Wei Ping Xing
Keyword(s):  
Wind Speed ◽  
Outlet Section ◽  
Inlet Section ◽  
Two Phase ◽  
Vof Model ◽  
Wind Speed Distribution ◽  
Euler Model ◽  
Spillway Tunnel ◽  
Ventilation Hole ◽  
Large Discharge

In order to analysis the applicability of VOF and Euler models to simulate water-air two-phase flow, VOF model and Euler model, respectively combining turbulent model, were used to simulate wind speed in ventilation hole of working gate in a hydropower station spillway tunnel with high head and large discharge in China. The results show that the dragging force simulated by Euler model is much more effective than that simulated by VOF model, causing significant increase of airflow in ventilation hole. It is obviously that wind speed simulated by Euler model is more close to the measured one, which may also provide evidence for design of ventilation hole. So Euler model is a better method to simulate the characteristic of aerated flow than VOF model. Meanwhile, the maximum wind speed occur near the inlet of ventilation hole, and the maximum value of wind speed is close to 120 m/s, which can cause loud noise. And wind speed distribution on the inlet section and outlet section of ventilation hole is respectively the most non-uniform and uniform. The conclusions obtained can improve the design of ventilation hole.

Simulation and Experiments of Aerated Flow in Curve-Connective Tunnel with High Head and Large Discharge

2016 ◽  
Vol 14 (1) ◽  
pp. 23-33 ◽  
Author(s):  
Shuai Li ◽  
Jian-min Zhang ◽  
Wei-lin Xu ◽  
Jian-gang Chen ◽  
Yong Peng ◽  
...  
Keyword(s):  
Aerated Flow ◽  
High Head ◽  
Large Discharge

Experimental and Numerical Simulation for Thermal Investigation of Oscillating Heat Pipe Using VOF Model

2020 ◽  
Vol 38 (1A) ◽  
pp. 88-104
Author(s):  
Anwar S. Barrak ◽  
Ahmed A. M. Saleh ◽  
Zainab H. Naji
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Input ◽  
Cfd Simulation ◽  
Working Fluid ◽  
Maximum Deviation ◽  
Inlet Temperature ◽  
Maximum Heat ◽  
Oscillating Heat Pipe ◽  
Vof Model

This study is investigated the thermal performance of seven turns of the oscillating heat pipe (OHP) by an experimental investigation and CFD simulation. The OHP is designed and made from a copper tube with an inner diameter 3.5 mm and thickness 0.6 mm and the condenser, evaporator, and adiabatic lengths are 300, 300, and 210 mm respectively.  Water is used as a working fluid with a filling ratio of 50% of the total volume. The evaporator part is heated by hot air (35, 40, 45, and 50) oC with various face velocity (0.5, 1, and 1.5) m/s. The condenser section is cold by air at temperature 15 oC. The CFD simulation is done by using the volume of fluid (VOF) method to model two-phase flow by conjugating a user-defined function code (UDF) to the FLUENT code. Results showed that the maximum heat input is 107.75 W while the minimum heat is 13.75 W at air inlet temperature 35 oC with air velocity 0.5m/s. The thermal resistance decreased with increasing of heat input. The results were recorded minimum thermal resistance 0.2312 oC/W at 107.75 W and maximum thermal resistance 1.036 oC/W at 13.75W. In addition, the effective thermal conductivity increased due to increasing heat input.  The numerical results showed a good agreement with experimental results with a maximum deviation of 15%.

Study of Flow Characteristics of Oil and Water in the Process of Stirring

2013 ◽  
Vol 353-356 ◽  
pp. 3190-3193
Author(s):  
Zong Rui Hao ◽  
Juan Xu ◽  
Hai Yan Bie ◽  
Zhong Hai Zhou
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Cross Section ◽  
Radial Flow ◽  
Flow Characteristics ◽  
Stirred Tank ◽  
Turbulent Model ◽  
Vof Model ◽  
Circular Flows ◽  
Oil Water

To study the flow pattern in the process of oil-water stirring in three paddle stirring tank, RNG k-ε turbulent model and VOF model are adopted to simulate the flow field at different time in the stirred tank with the baffle. The results showed that, in the stirring process, inverted cone manifold was formed in the center of the stirring shaft. The stratified area was formed in the baffle and gradually transported to the bottom of the tank. The two circular flows were formed among three groups of blades. And the axially acting of the fluid was strong, which made homogeneous stirring in the stirred tank. At the same time the radial flow of the cross-section inside the tank increased because of the baffle.

scholarly journals Free surface profile and inception point as characteristics of aerated flow over stepped spillway: Numerical study

2019 ◽  
Vol 42 (1) ◽  
pp. 42-48
Author(s):  
Chakib Bentalha ◽  
Mohammed Habi
Keyword(s):  
Free Surface ◽  
Kinetic Energy ◽  
Water Depth ◽  
Numerical Study ◽  
Surface Profile ◽  
Air Entrainment ◽  
Stepped Spillway ◽  
Ansys Fluent ◽  
Vof Model ◽  
Inception Point

Abstract Stepped spillway is hydraulic structure designed to dissipate the excess in kinetic energy at the downstream of dams and can reduce the size of stilling basin at the toe of the spillway or chute. The flow on a stepped spillway is characterised by the large aeration that can prevent or reduce the cavitation damage. The air entrainment starts where the boundary layer attains the free surface of flow; this point is called “point of inception”. Within this work the inception point is determined by using software Ansys Fluent where the volume of fluid (VOF) model is used as a tool to track the free surface thereby the turbulence closure is derived in the k − ε turbulence standard model. This research aims to find new formulas for describe the variation of water depth at step edge and the positions of the inception point, at the same time the contour map of velocity, turbulent kinetic energy and strain rate are presented. The found numerical results agree well with experimental results like the values of computed and measured water depth at the inception point and the numerical and experimental inception point locations. Also, the dimensionless water depth profile obtained by numerical method agrees well with that of measurement. This study confirmed that the Ansys Fluent is a robust software for simulating air entrainment and exploring more characteristics of flow over stepped spillways.

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