A New Method for Numerical Prediction of Liquid Column Separation Accompanying Hydraulic Transients in Pipelines

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Adam Adamkowski ◽  
Mariusz Lewandowski
Keyword(s):  
Hydraulic System ◽  
Pressure Fluctuations ◽  
Liquid Column ◽  
New Method ◽  
Cavity Model ◽  
Vapor Cavity ◽  
Pressure Drops ◽  
Column Separation ◽  
Proposed Model ◽  
Positive Results

This paper presents a new method for calculating pressure fluctuations in pipelines during a water hammer with liquid column separation. The method is based on the discrete-vapor-cavity model (DVCM). Such kind of models assumes that vaporous cavities are formed in each computational section of the pipeline whenever the pressure drops to the vapor pressure at a given temperature. The proposed new model (new DVCM) brings a significant improvement in the reliability of predictions compared with existing DVCMs. The calculation method based on it eliminates some disadvantages of basic methods used in practice, as shown by comparisons between calculations made for simple hydraulic system under theoretical frictionless conditions using various DVCMs. Additionally, the authors present preliminary verification of the proposed model based on experimental results. The positive results of this verification, and the advantages of the new DVCM, could lead to incorporating them into commercial codes.

A New Method for Numerical Prediction of Liquid Column Separation Accompanying Hydraulic Transients in Pipelines

2007 ◽  
Author(s):  
Adam Adamkowski ◽  
Mariusz Lewandowski
Keyword(s):  
Pressure Fluctuations ◽  
Water Hammer ◽  
Liquid Column ◽  
New Method ◽  
Cavity Model ◽  
Vapor Cavity ◽  
Main Method ◽  
Pressure Drops ◽  
Column Separation ◽  
Prediction Reliability

The paper presents a new method for calculating pressure fluctuations in pipelines during a water hammer with liquid column separation. The method is based on the discrete-vapor-cavity model which assumes that vaporous cavities are formed in every computational section of the pipeline whenever the pressure drops to the vapor pressure at a given temperature. The method brings a significant improvement in prediction reliability as compared with the methods known so far. It eliminates disadvantages of basic methods used in practice — this is proved by comparisons between calculations made for several study cases. It is expected that the proposed method will become the main method in commercial codes used for simulating water hammer with the liquid column separation.

New Method for Numerical Prediction of Water Hammer With Column Separation: Comparison With Experiment and the Relap5 Program

2009 ◽  
Author(s):  
Adam Adamkowski ◽  
Mariusz Lewandowski ◽  
Jerzy Marcinkiewicz
Keyword(s):  
Pressure Fluctuations ◽  
Water Hammer ◽  
Liquid Column ◽  
New Method ◽  
Cavity Model ◽  
Validation Process ◽  
Hydraulic Transients ◽  
Column Separation ◽  
Comparison With Experiment ◽  
Measured Pressure

Liquid column separation accompanying water hammer (hydraulic transients) was a subject of numerous research works conducted in many scientific centres of the world. So far, there are not any satisfactory results of using computational methods to simulate this phenomenon. The authors of this paper have developed a new method for calculating pressure fluctuations in pipelines during hydraulic transients with liquid column separation. This method is based on the innovative (original) discrete-vapour-cavity model. In the paper there are two steps presented in the validation process of the new model. The first step is the comparison with experimental data and the second one is the comparison with results obtained using the commercial computer program Relap5. The comparisons of calculated by means of the considered numerical methods and measured pressure surges show significant differences. The reasons for the discrepancies are discussed and conclusions are presented.

scholarly journals Coupling Quasi-Two-Dimensional Friction Model and Discrete Vapor Cavity Model for Simulation of Transient Cavitating Flows in Pipeline Systems

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Qiang Sun ◽  
Yuebin Wu ◽  
Ying Xu ◽  
Liang Chen ◽  
Tae Uk Jang
Keyword(s):  
Cost Effective ◽  
Friction Model ◽  
Experimental Results ◽  
Complex Nature ◽  
Two Dimensional ◽  
Cavity Model ◽  
Cavitating Flows ◽  
Vapor Cavity ◽  
Proposed Model ◽  
Pipeline Systems

Accurate simulation of cavitating flows in pipeline systems is important for cost-effective surge protection. However, this is still a challenge due to the complex nature of the problem. This paper presents a numerical model that combines the discrete vapor cavity model (DVCM) with the quasi-two-dimensional (quasi-2D) friction model to simulate transient cavitating flows in pipeline systems. The proposed model is solved by the method of characteristics (MOC), and the performance is investigated through a numerical case study formulated based on a laboratory pipeline reported in the literature. The results obtained by the proposed model are compared with those calculated by the classic one-dimensional (1D) friction model with the DVCM and the corresponding experimental results provided by the literature, respectively. The comparison shows that the pressure peak, waveform, and phase of pressure pulsations predicted by the proposed model are closer to the experimental results than those obtained by the classic 1D model. This demonstrates that the proposed model that combines the quasi-2D friction model with the DVCM has provided a solution to more accurately simulate transient cavitating flows in pipeline systems.

scholarly journals A Multidimensional and Multiscale Model for Pressure Analysis in a Reservoir-Pipe-Valve System

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Feng Jie Zheng ◽  
Chao Yong Zong ◽  
William Dempster ◽  
Fu Zheng Qu ◽  
Xue Guan Song
Keyword(s):  
Large Scale ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Multiscale Model ◽  
Computational Time ◽  
Small Scale ◽  
Dimensional System ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Proposed Model

Reservoir-pipe-valve (RPV) systems are widely used in many industrial processes. The pressure in an RPV system plays an important role in the safe operation of the system, especially during the sudden operations such as rapid valve opening or closing. To investigate the pressure response, with particular interest in the pressure fluctuations in an RPV system, a multidimensional and multiscale model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the model, the reservoir is modeled as a zero-dimensional virtual point, the pipe is modeled as a one-dimensional system using the MOC, and the valve is modeled using a three-dimensional CFD model. An interface model is used to connect the multidimensional and multiscale model. Based on the model, a transient simulation of the turbulent flow in an RPV system is conducted in which not only the pressure fluctuation in the pipe but also the detailed pressure distribution in the valve is obtained. The results show that the proposed model is in good agreement when compared with a high fidelity CFD model used to represent both large-scale and small-scale spaces. As expected, the proposed model is significantly more computationally efficient than the CFD model. This demonstrates the feasibility of analyzing complex RPV systems within an affordable computational time.

scholarly journals A Single Valued Neutrosophic Inventory Model with Neutrosophic Random Variable

2020 ◽  
pp. 52-63
Author(s):  
M. Mullai*, K. Sangeetha, R. Surya, G. Madhan kumar, R. Jeyabalan ◽  
◽  
◽  
S. Broumi
Keyword(s):  
Random Variables ◽  
Random Variable ◽  
Inventory Model ◽  
Newsvendor Problem ◽  
New Method ◽  
Optimal Sequence ◽  
Average Value ◽  
Proposed Model

This paper presents the problematic period of neutrosophic inventory in an inaccurate and unsafe mixed environment. The purpose of this paper is to present demand as a neutrosophic random variable. For this model, a new method is developed for determining the optimal sequence size in the presence of neutrosophic random variables. Where to get optimality by gradually expressing the average value of integration. The newsvendor problem is used to describe the proposed model.

A novel fractional discrete nonlinear grey Bernoulli model for forecasting the wind turbine capacity of China

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Wen-ze Wu ◽  
Wanli Xie ◽  
Chong Liu ◽  
Tao Zhang
Keyword(s):  
Wind Turbine ◽  
Nonlinear Coefficient ◽  
Predictive Performance ◽  
Prediction Performance ◽  
New Method ◽  
Grey Model ◽  
Content Type ◽  
Proposed Model ◽  
Whale Optimization ◽  
Turbine Capacity

PurposeA new method for forecasting wind turbine capacity of China is proposed through grey modelling technique.Design/methodology/approachFirst of all, the concepts of discrete grey model are introduced into the NGBM(1,1) model to reduce the discretization error from the differential equation to its discrete forms. Then incorporating the conformable fractional accumulation into the discrete NGBM(1,1) model is carried out to further improve the predictive performance. Finally, in order to effectively seek the emerging coefficients, namely, fractional order and nonlinear coefficient, the whale optimization algorithm (WOA) is employed to determine the emerging coefficients.FindingsThe empirical results show that the newly proposed model has a better prediction performance compared to benchmark models; the wind turbine capacity from 2019 to 2021 is expected to reach 275954.42 Megawatts in 2021. According to the forecasts, policy suggestions are provided for policy-makers.Originality/valueBy combing the fractional accumulation and the concepts of discrete grey model, a new method to improve the prediction performance of the NGBM(1,1) model is proposed. The newly proposed model is firstly applied to predict wind turbine capacity of China.

scholarly journals A Hybrid Grey Prediction Model for Small Oscillation Sequence Based on Information Decomposition

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Meng Zhou ◽  
Bo Zeng ◽  
Wenhao Zhou
Keyword(s):  
Prediction Model ◽  
Small Oscillation ◽  
New Method ◽  
Superior Performance ◽  
Small Data ◽  
Grey Prediction ◽  
New Model ◽  
Grey Prediction Model ◽  
Proposed Model ◽  
Oscillation Characteristic

Grey prediction model has good performance in solving small data problem, and has been widely used in various research fields. However, when the data show oscillation characteristic, the effect of grey prediction model performs poor. To this end, a new method was proposed to solve the problem of modelling small data oscillation sequence with grey prediction model. Based on the idea of information decomposition, the new method employed grey prediction model to capture the trend characteristic of complex system, and ARMA model was applied to describe the random oscillation characteristic of the system. Crops disaster area in China was selected as a case study and the relevant historical eight-year data published by government department were substituted to the proposed model. The modelling results of the new model were compared with those of other traditional mainstream prediction models. The results showed that the new model had evidently superior performance. It indicated that the proposed model will contribute to solve small oscillation problems and have positive significance for improving the applicability of grey prediction model.

scholarly journals Single-Diode Models of PV Modules: A Comparison of Conventional Approaches and Proposal of a Novel Model

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1296 ◽  
Author(s):  
Tuyen Nguyen-Duc ◽  
Huy Nguyen-Duc ◽  
Thinh Le-Viet ◽  
Hirotaka Takano
Keyword(s):  
Renewable Energy ◽  
New Method ◽  
National Renewable Energy Laboratory ◽  
Matlab Code ◽  
Proposed Model ◽  
Pv Modules ◽  
Consistent Performance ◽  
Novel Model

In this paper, the seven traditional models of photovoltaic (PV) modules are reviewed comprehensively to find out the appropriate model for reliability. All the models are validated using the Matlab code and graphical comparisons between models are made. The accuracy and convergence of each model is evaluated using the data of manufactured PV panels. Then, a novel model is proposed showing its consistent performance. The three most key parameters of the single-diode model are self-revised to adapt to various types of PV modules. This new method is verified in three types of PV panels’ data measured by the National Renewable Energy Laboratory (NREL), USA. The validated data show promising results when the error RMSEs’ range of the proposed model is under 0.36.

Hydraulic System Simulation Analysis of Shearer's Cutting Part Based on AEMSim

2012 ◽  
Vol 268-270 ◽  
pp. 841-844
Author(s):  
Li Rong Wan ◽  
Xing Hua Wang ◽  
Jian Liang Li ◽  
Bin Zhang ◽  
Xian Peng Li
Keyword(s):  
Dynamic Property ◽  
Hydraulic System ◽  
Simulation Analysis ◽  
System Simulation ◽  
Fluid Simulation ◽  
New Method ◽  
Simulation Technology ◽  
Rigorous Analysis ◽  
Mining Machinery ◽  
New Type

Simulation analysis on the hydraulic system of shearer's cutting part was established based on the research of fluid simulation technology. The hydraulic model was built using the AMESim software. By verifying the results, a new method about the rigorous analysis of holistic dynamic property of the hydraulic system is developed and a new way to design new type mining machinery and improve its capabilities is provided.

scholarly journals A New Method to Extract Gate Bias-Dependent Parasitic Resistances in GaAs pHEMTs

Electronics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 266
Author(s):  
Ruirui Dang ◽  
Lijie Yang ◽  
Zhihao Lv ◽  
Chunyi Song ◽  
Zhiwei Xu
Keyword(s):  
Parameter Extraction ◽  
New Method ◽  
Small Signal ◽  
Gate Bias ◽  
Large Signal ◽  
S Parameter ◽  
Proposed Model ◽  
Measurement Results ◽  
Parasitic Parameter ◽  
Signal Models

Accurate large signal GaAs pHEMT models are essential for devices’ performance analysis and microwave circuit design. This, in turn, mandates precise small signal models. However, the accuracy of small signal models strongly depends on reliable parasitic parameter extraction of GaAs pHEMT, which also greatly influences the extraction of intrinsic elements. Specifically, the parasitic source and drain resistances, R s and R d , are gate bias-dependent, due to the two-dimensional charge variations. In this paper, we propose a new method to extract R s and R d directly from S-parameter measurements of the device under test (DUT), which save excessive measurements and complicated parameter extraction. We have validated the proposed method in both simulation and on-wafer measurement, which achieves better accuracy than the existing state-of-the-art in a frequency range of 0.5–40 GHz. Furthermore, we develop a GaAs pHEMT power amplifier (PA) to further validate the developed model. The measurement results of the PA at 9–15 GHz agree with the simulation results using the proposed model.

Sign in / Sign up

Export Citation Format

Share Document