Flow Patterns, Flow Pattern Maps, and Flow Pattern Transition Models

2022 ◽  
pp. 141-165
Author(s):  
Afshin J. Ghajar
Keyword(s):  
Flow Pattern ◽  
Flow Patterns ◽  
Flow Pattern Transition ◽  
Transition Models

Detecting the Flow Pattern Transition in the Gas-Liquid Two-Phase Flow Using Multivariate Multi-Scale Entropy Analysis

2019 ◽  
Vol 74 (10) ◽  
pp. 837-848 ◽  
Author(s):  
Yudong Liu ◽  
Dayang Wang ◽  
Yingyu Ren ◽  
Ningde Jin
Keyword(s):  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Mean Value ◽  
Entropy Rate ◽  
Permutation Entropy ◽  
Phase Flow ◽  
Two Phase ◽  
Multi Scale ◽  
Flow Pattern Transition

AbstractDue to the complex flow structure and non-uniform phase distribution in the vertical upward gas-liquid two-phase flow, an eight-electrode rotating electric field conductance sensor is used to obtain multi-channel conductance signals. The flow patterns of the vertical upward gas-liquid two-phase flow are classified according to the images obtained from a high-speed camera. Then, we employ the multivariate weighted multi-scale permutation entropy (MWMPE) to detect the instability of flow pattern transition in the gas-liquid two-phase flow. Afterwards, we compare the results of the MWMPE with those of the single-channel weighted multi-scale permutation entropy (SCWMPE) and multivariate multi-scale sample entropy (MMSE). The comparison results indicate that, compared with the SCWMPE and MMSE, the MWMPE has superior performance in terms of the high-resolution presentation of flow instability in the gas-liquid two-phase flow. Finally, we extract the mean value of the MWMPE in whole scales and the entropy rate of the MWMPE in the small scales. The results indicate that the normalized mean value and normalized entropy rate of MWMPE are very sensitive to the transitions of flow patterns, thus allowing the detection of the instability of flow pattern transition.

An Experimental Study on Air-Water Two-Phase Flow Patterns in Pebble Beds

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Bai Bofeng ◽  
Liu Maolong ◽  
Su Wang ◽  
Zhang Xiaojie
Keyword(s):  
Experimental Study ◽  
Flow Pattern ◽  
Test Section ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pattern Transition

An experimental study was conducted on the air-water two-phase flow patterns in the bed of rectangular cross sections containing spheres of regular distribution. Three kinds of glass spheres with different diameters (3 mm, 6 mm, and 8 mm) were used for the establishment of the test section. By means of visual observations of the two-phase flow through the test section, it was discovered that five different flow patterns occurred within the experimental parameter ranges, namely, bubbly flow, bubbly-slug flow, slug flow, slug-annular flow, and annular flow. A correlation for the bubble and slug diameter in the packed beds was proposed, which was an extended expression of the Tung/Dhir model, Jamialahmadi’s model, and Schmidt’s model. Three correlations were proposed to calculate the void friction of the flow pattern transition in bubble flow, slug flow, and annular flow based on the bubble model in the pore region. The experimental result showed that the modified Tung and Dhir model of the flow pattern transition was in better agreement with the experimental data compared with Tung and Dhir’s model.

Simulation on Flow Pattern Transition With Liquid Nitrogen and its Vapor Using a Droplet Entrainment Model

2020 ◽  
Author(s):  
Rui Zhou ◽  
Tao Xia ◽  
Xiaobin Zhang
Keyword(s):  
Flow Pattern ◽  
Liquid Nitrogen ◽  
Slug Flow ◽  
Flow Patterns ◽  
Eulerian Model ◽  
Ansys Fluent ◽  
Droplet Entrainment ◽  
Flow Pattern Transition ◽  
Churn Flow ◽  
Two Fluid

Abstract A droplet entrainment model was applied to characterize the flow pattern transition in the countercurrent horizontal flow with liquid nitrogen (LN2) and vapor nitrogen (VN2). A two-fluid three-field model consisting of liquid film, gas, and droplet was implemented based on the Eulerian-Eulerian model in ANSYS Fluent®. In the droplet entrainment model, the condition and position of the droplet generation were realized by calculating the velocity gradient in the normal direction of the interface towards the gas core. The droplet entrainment and deposition rates were also included and validated according to the available data of water/air in the literature. Three flow patterns, including stratified-wavy flow, churn flow, and pseudo-slug flow, were identified in simulation results with LN2/VN2. Furthermore, ligament breakup was found to be the main droplet entrainment mechanism in the churn and pseudo-slug flow, and there can be a high probability of the occurrence of bubble burst as well. Compared with water/air, the droplets are more easily to be entrained in LN2/VN2 due to the smaller viscosity and surface tension according to the results of droplet mass flow rate. Pressure drop signals of the three flow patterns were also obtained and analyzed.

High-Viscosity Liquid/Gas Flow Pattern Transitions in Upward Vertical Pipe Flow

SPE Journal ◽  
2020 ◽  
Vol 25 (03) ◽  
pp. 1155-1173
Author(s):  
Eissa Al-Safran ◽  
Mohammad Ghasemi ◽  
Feras Al-Ruhaimani
Keyword(s):  
Flow Pattern ◽  
Two Phase Flow ◽  
Bubble Diameter ◽  
High Viscosity ◽  
Transition Model ◽  
Phase Flow ◽  
Liquid Viscosity ◽  
Two Phase ◽  
Flow Pattern Transition ◽  
Transition Models

Summary High-viscosity liquid two-phase upward vertical flow in wells and risers presents a new challenge for predicting pressure gradient and liquid holdup due to the poor understanding and prediction of flow pattern. The objective of this study is to investigate the effect of liquid viscosity on two-phase flow pattern in vertical pipe flow. Further objective is to develop new/improve existing mechanistic flow-pattern transition models for high-viscosity liquid two-phase-flow vertical pipes. High-viscosity liquid flow pattern two-phase flow data were collected from open literature, against which existing flow-pattern transition models were evaluated to identify discrepancies and potential improvements. The evaluation revealed that existing flow transition models do not capture the effect of liquid viscosity, resulting in poor prediction. Therefore, two bubble flow (BL)/dispersed bubble flow (DB) pattern transitions are proposed in this study for two different ranges of liquid viscosity. The first proposed transition model modifies Brodkey's critical bubble diameter (Brodkey 1967) by including liquid viscosity, which is applicable for liquid viscosity up to 100 mPa·s. The second model, which is applicable for liquid viscosities above 100 mPa·s, proposes a new critical bubble diameter on the basis of Galileo's dimensionless number. Furthermore, the existing bubbly/intermittent flow (INT) transition model on the basis of a critical gas void fraction of 0.25 (Taitel et al. 1980) is modified to account for liquid viscosity. For the INT/annular flow (AN) transition, the Wallis transition model (Wallis 1969) was evaluated and found to be able to predict the high-viscosity liquid flow pattern data more accurately than the existing models. A validation study of the proposed transition models against the entire high-viscosity liquid experimental data set revealed a significant improvement with an average error of 22.6%. Specifically, the model over-performed existing models in BL/INT and INT/AN pattern transitions.

Flow Pattern Transition Criteria for Upward Two-Phase Flow in Annulus

2020 ◽  
Author(s):  
He Wen ◽  
Zhao Chenru ◽  
Bo Hanliang
Keyword(s):  
Flow Pattern ◽  
Flow Patterns ◽  
Flow Transition ◽  
Two Phase ◽  
Transition Mechanism ◽  
Flow Pattern Transition ◽  
Transition Criteria ◽  
Asymmetric Shape ◽  
Basic Characteristics ◽  
Churn Flow

Abstract Vertical upward two-phase flows in annulus are of great importance in many industrial fields due to the closely relationship between the flow patterns and the heat transfer characteristics. Common flow patterns in annulus are bubbly (B), slug (S), churn (C) and annular (A) flow, most of which are quite similar to those in tubes. However, due to the elliptic nose and asymmetric shape of the Taylor bubble in annulus, the slug to churn flow transition could be influenced by the channel geometry which was usually ignored in most of the previous researches. The flow pattern transition criteria for tubes are thus not applicable for annulus, especially for slug to churn flow transition, which should be separately studied. Therefore, in this paper, the basic characteristics of the flow pattern in annulus and their transition mechanism are analyzed. In addition, a set of semi-empirical transition criteria with higher accuracy are assessed and selected for annulus based on theoretical analysis and comparisons with experimental data.

scholarly journals Characterizing the correlations between local phase fractions of gas–liquid two-phase flow with wire-mesh sensor

2016 ◽  
Vol 374 (2070) ◽  
pp. 20150335 ◽  
Author(s):  
C. Tan ◽  
W. L. Liu ◽  
F. Dong
Keyword(s):  
Flow Pattern ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Flow Patterns ◽  
Wire Mesh ◽  
Phase Flow ◽  
Local Phase ◽  
Two Phase ◽  
Phase Fluctuations ◽  
Flow Pattern Transition

Understanding of flow patterns and their transitions is significant to uncover the flow mechanics of two-phase flow. The local phase distribution and its fluctuations contain rich information regarding the flow structures. A wire-mesh sensor (WMS) was used to study the local phase fluctuations of horizontal gas–liquid two-phase flow, which was verified through comparing the reconstructed three-dimensional flow structure with photographs taken during the experiments. Each crossing point of the WMS is treated as a node, so the measurement on each node is the phase fraction in this local area. An undirected and unweighted flow pattern network was established based on connections that are formed by cross-correlating the time series of each node under different flow patterns. The structure of the flow pattern network reveals the relationship of the phase fluctuations at each node during flow pattern transition, which is then quantified by introducing the topological index of the complex network. The proposed analysis method using the WMS not only provides three-dimensional visualizations of the gas–liquid two-phase flow, but is also a thorough analysis for the structure of flow patterns and the characteristics of flow pattern transition. This article is part of the themed issue ‘Supersensing through industrial process tomography’.

GAS-LIQUID FLOW-PATTERN TRANSITION IN HORIZONTAL PIPES – ANALYSIS OF REPORTED MODELS

2018 ◽  
Author(s):  
André Mendes Quintino ◽  
Davi Lotfi Lavor Navarro da Rocha ◽  
Oscar Mauricio Hernandez Rodriguez
Keyword(s):  
Flow Pattern ◽  
Liquid Flow ◽  
Horizontal Pipes ◽  
Flow Pattern Transition ◽  
Gas Liquid Flow
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