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.

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.

Optimum Configuration of an Expanding-Contracting-Nozzle for Thrust Enhancement by Bubble Injection

2010 ◽  
Author(s):  
Sowmitra Singh ◽  
Jin-Keun Choi ◽  
Georges Chahine
Keyword(s):  
Bubble Dynamics ◽  
Bubbly Flow ◽  
Outlet Section ◽  
Inlet Section ◽  
Concept Design ◽  
Two Phase ◽  
Approximate Analytical Expression ◽  
Analytical Expression ◽  
Bubble Number ◽  
Analytical Approaches

This paper addresses the concept of thrust augmentation through bubble injection into an expanding-contracting nozzle. Two-phase models for bubbly flow in an expanding-contracting nozzle are developed, in parallel with laboratory experiments, and used to ascertain the geometry configuration for the nozzle that would lead to maximum thrust enhancement upon bubble injection. For preliminary optimization of experimental setup’s design, a quasi 1-D approach is used. Averaged flow quantities (such as velocities, pressures, and void fractions) in a cross-section are used for the analysis. The mixture continuity and momentum equations are numerically solved simultaneously, along with equations for bubble dynamics, bubble motion, and an equation for conservation of bubble number. Various geometric parameters such as the exit and inlet areas, the area of the bubble injection section, the presence of a throat and its location, the length of the diffuser section and the length of the contraction section are varied, and their effects on thrust enhancement are studied. Investigation on the effect of the injected void fraction is also carried out. The key objective function of the optimization is the normalized thrust parameter, which is the difference between the thrust with the bubble injection and the thrust before the bubble injection, normalized by the inlet momentum. An approximate analytical expression for the normalized thrust parameter was also derived starting from the mixture continuity and momentum equations. This analytical expression involved flow variables only at three locations; inlet section, injection section, and outlet section, and the expression is simple enough to produce a quick concept design of the diffuser-nozzle thruster. The numerical and analytical approaches are verified against each other and the limitations of the analytical approach are discussed.

Optimum Configuration of an Expanding-Contracting-Nozzle for Thrust Enhancement by Bubble Injection

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Sowmitra Singh ◽  
Jin-Keun Choi ◽  
Georges Chahine
Keyword(s):  
Bubble Dynamics ◽  
Bubbly Flow ◽  
Outlet Section ◽  
Inlet Section ◽  
Concept Design ◽  
Two Phase ◽  
Approximate Analytical Expression ◽  
Analytical Expression ◽  
Bubble Number ◽  
Analytical Approaches

This paper addresses the concept of thrust augmentation through bubble injection into an expanding-contracting nozzle. Two-phase models for bubbly flow in an expanding-contracting nozzle are developed, in parallel with laboratory experiments and used to ascertain the geometry configuration for the nozzle that would lead to maximum thrust enhancement upon bubble injection. For preliminary optimization of experimental setup’s design, a quasi 1-D approach is used. Averaged flow quantities (such as velocities, pressures, and void fractions) in a cross section are used for the analysis. The mixture continuity and momentum equations are numerically solved simultaneously along with equations for bubble dynamics, bubble motion, and an equation for conservation of the total bubble number. Various geometric parameters such as the exit and inlet areas, the area of the bubble injection section, the presence of a throat and its location, the length of the diffuser section and the length of the contraction section are varied, and their effects on thrust enhancement are studied. Investigation on the effect of the injected void fraction is also carried out. The key objective function of the optimization is the normalized thrust parameter, which is the thrust with bubble injection minus the thrust with liquid only divided by the inlet liquid momentum. An approximate analytical expression for the normalized thrust parameter was also derived starting from the mixture continuity and momentum equations. This analytical expression involved flow variables only at three locations; inlet section, injection section, and outlet section, and the expression is simple enough to produce a quick concept design of the diffuser-nozzle thruster. The numerical and analytical approaches are verified against each other and the limitations of the analytical approach are discussed.

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.

scholarly journals Effect of Flow Rate on Turbulence Dissipation Rate Distribution in a Multiphase Pump

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 886
Author(s):  
Zongliu Huang ◽  
Guangtai Shi ◽  
Xiaobing Liu ◽  
Haigang Wen
Keyword(s):  
Flow Rate ◽  
Dissipation Rate ◽  
Circumferential Direction ◽  
Outlet Section ◽  
Inlet Section ◽  
Distribution Characteristics ◽  
Rate Condition ◽  
Rate Distribution ◽  
Multiphase Pump ◽  
Rotating Impeller

The turbulence dissipation will cause the increment of energy loss in the multiphase pump and deteriorate the pump performance. In order to research the turbulence dissipation rate distribution characteristics in the pressurized unit of the multiphase pump, the spiral axial flow type multiphase pump is researched numerically in the present study. This research is focused on the turbulence dissipation rate distribution characteristics in the directions of inlet to outlet, hub to rim, and in the circumferential direction of the rotating impeller blades. Numerical simulation based on the RANS (Reynolds averaged Navier–Stokes equations) and the k-ω SST (Shear Stress Transport) turbulence model has been carried out. The numerical method is verified by comparing the numerical results with the experimental data. Results show that the regions of the large turbulence dissipation rate are mainly at the inlet and outlet of the rotating impeller and static impeller, while it is almost zero from the inlet to the middle of outlet in the suction surface and pressure surface of the first-stage rotating impeller blades. The turbulence dissipation rate is increased gradually from the hub to the rim of the inlet section of the first-stage rotating impeller, while it is decreased firstly and then increased on the middle and outlet sections. The turbulence dissipation rate distributes unevenly in the circumferential direction on the outlet section. The maximum value of the turbulence dissipation rate occurs at 0.9 times of the rated flow rate, while the minimum value at 1.5 times of the rated flow rate. Four turning points in the turbulence dissipation rate distribution that are the same as the number of impeller blades occur at 0.5 times the blade height at 0.9 times the rated flow rate condition. The turbulence dissipation rate distribution characteristics in the pressurized unit of the multiphase pump have been studied carefully in this paper, and the research results have an important significance for improving the performance of the multiphase pump theoretically.

scholarly journals Optimization of a Small Wind Power Plant for Annual Wind Speed Distribution

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1587
Author(s):  
Krzysztof Wrobel ◽  
Krzysztof Tomczewski ◽  
Artur Sliwinski ◽  
Andrzej Tomczewski
Keyword(s):  
Wind Speed ◽  
Power Plant ◽  
Wind Power ◽  
Power Plants ◽  
Control Method ◽  
Wind Power Plant ◽  
Switched Reluctance ◽  
Wind Speeds ◽  
Wind Speed Distribution ◽  
And Control

This article presents a method to adjust the elements of a small wind power plant to the wind speed characterized by the highest annual level of energy. Tests were carried out on the basis of annual wind distributions at three locations. The standard range of wind speeds was reduced to that resulting from the annual wind speed distributions in these locations. The construction of the generators and the method of their excitation were adapted to the characteristics of the turbines. The results obtained for the designed power plants were compared with those obtained for a power plant with a commercial turbine adapted to a wind speed of 10 mps. The generator structure and control method were optimized using a genetic algorithm in the MATLAB program (Mathworks, Natick, MA, USA); magnetostatic calculations were carried out using the FEMM program; the simulations were conducted using a proprietary simulation program. The simulation results were verified by measurement for a switched reluctance machine of the same voltage, power, and design. Finally, the yields of the designed generators in various locations were determined.

scholarly journals Weibull Wind-Speed Distribution Parameters Derived from a Combination of Wind-Lidar and Tall-Mast Measurements Over Land, Coastal and Marine Sites

2015 ◽  
Vol 159 (2) ◽  
pp. 329-348 ◽  
Author(s):  
Sven-Erik Gryning ◽  
Rogier Floors ◽  
Alfredo Peña ◽  
Ekaterina Batchvarova ◽  
Burghard Brümmer
Keyword(s):  
Wind Speed ◽  
Speed Distribution ◽  
Wind Speed Distribution ◽  
Distribution Parameters ◽  
Wind Lidar

Comparison of Three Methods to Estimate Wind Speed Distribution

2011 ◽  
Author(s):  
D. K. Kirova ◽  
Michail D. Todorov ◽  
Christo I. Christov
Keyword(s):  
Wind Speed ◽  
Speed Distribution ◽  
Wind Speed Distribution

scholarly journals Artificial Intelligence Techniques for Estimation of Optimum Weibull Parameters for Wind Speed Distribution

2019 ◽  
Vol 8 (4S2) ◽  
pp. 150-156
Keyword(s):  
Wind Speed ◽  
Tamil Nadu ◽  
Optimization Algorithms ◽  
Coefficient Of Determination ◽  
Short Term ◽  
Weibull Parameters ◽  
Wind Speed Data ◽  
Speed Distribution ◽  
Wind Speed Distribution

The main objective of this study is to estimate the optimum Weibull scale and shape parameters for wind speed distribution at three stations of the state of Tamil Nadu, India using Nelder-Mead, Broyden–Fletcher–Goldfarb–Shanno, and Simulated annealing optimization algorithms. An attempt has been made for the first time to apply these optimization algorithms to determine the optimum parameters. The study was conducted for long term wind speed data (38 years), short term wind speed data (5 years) and also with single year’s wind speed data to assess the performance of the algorithm for different quantum of data. The efficiency of these algorithms are analyzed using various statistical indicators like Root mean square error (RMSE), Correlation coefficient (R), Mean absolute error (MAE) and coefficient of determination (R2). The results suggest that the performance of three algorithms is similar irrespective of the quantum of the dataset. The estimated Weibull parameters are almost similar for short term and long term dataset. There is a marginal variation in the obtained parameters when only single year’s wind data is considered for the analysis. The Weibull probability distribution curve fits very well on the wind speed histogram when only single year’s wind speed data is considered and fits marginally well when short term and long term wind speed data is considered

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