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Gas–liquid two-phase flow is very common in industrial pipelines. Flow regime identification is the first step to design, analyze, and operate the gas–liquid system successfully. The purpose of this study is to develop a methodology for identification of a two-phase flow regime using post signal processing techniques, namely Fast Fourier Transform...
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Context 1
... that reason, the hexahedral meshing technique was used to generate the mesh. The multizone method was selected, where pure hexahedral mesh was assigned in all places possible while unstructured mesh is placed in the remaining regions, as shown in Figure 2. To capture twophase flow behavior near the boundary walls properly and accurately, five inflation layers using the smooth transition option were applied, as shown in Figure 2b. ...
Context 2
... that reason, the hexahedral meshing technique was used to generate the mesh. The multizone method was selected, where pure hexahedral mesh was assigned in all places possible while unstructured mesh is placed in the remaining regions, as shown in Figure 2. To capture twophase flow behavior near the boundary walls properly and accurately, five inflation layers using the smooth transition option were applied, as shown in Figure 2b. The transition ratio used was 0.1 with a growth rate of 1.1 to get appropriate inflation layers. ...
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As an emerging flexible-scale energy storage technology, underwater compressed gas energy storage (UW-CGES) is regarded as a promising energy storage option for offshore platforms, offshore renewable energy farms, islands, coastal cities, etc. Liquid accumulation often occurs in underwater gas transmission pipelines, which is a challenge to overcom...
Citations
... The ANSYS Fluent theory guide [37] confirms the remarkable improvements of the realizable model over other k-ε models. Detailed formulations for a thorough comprehension of the applied method and its equations can be found in references [36,38]. ...
Accurate identification of flow regimes is paramount in several industries, especially in chemical and hydrocarbon sectors. This paper describes a comprehensive data-driven workflow for flow regime identification. The workflow encompasses: i) the collection of dynamic pressure signals using an experimentally verified numerical
two-phase flow model for three different flow regimes: stratified, slug and annular flow, ii) feature extraction from pressure signals using Discrete Wavelet transformation (DWT), iii) Evaluation and testing of 12 different Dimensionality Reduction (DR) techniques, iv) the application of an AutoML framework for automated Machine Learning classifier selection among K-Nearest Neighbors, Artificial Neural Networks, Support Vector Machines, Gradient Boosting, Random Forest, and Logistic Regression, with hyper-parameter tuning. Kernel Fisher Discriminant Analysis (KFDA) is the best DR technique, exhibiting superior goodness of clustering, while KNN proved to be the top classifier with an accuracy of 92.5 % and excellent repeatability. The combination of DWT, KFDA and KNN was used to produce a virtual flow regime map. The proposed workflow represents a significant
step forward in automating flow regime identification and enhancing the interpretability of ML classifiers, allowing its application to opaque pipes fitted with pressure sensors for achieving flow assurance and automatic monitoring of two-phase flow in various process industries.
... Longitudinal flow in inlet and outlet arms stayed perpendicular to gravity while rotating U-bend from horizontal to vertically upward flow. Fixed mesh body size of 7 mm was selected for inlet and outlet arm [23]. The element size of Inlet bend, outlet bend, and bend arm were varied to find number of elements that converge mesh independence study curves. ...
U-bends are frequently employed in industries to change the direction of fluid flow. Flow Induced Vibrations (FIV) are very prominent due to internal two-phase flow and vary with U-bend orientation. Potential possibilities of spatial orientations of a U-bend make it impractical to predict these vibrations using an experimental approach. This study investigates the two-phase flow-induced vibrations for 0°, 30°, 60° and 90° upward flow in a U-bend using CFD. In-plane and out-of-plane directional vibrational data was gathered for these four orientations of U-bend. For constant superficial velocities with void fraction of 0.5, impact of orientation on slug frequencies was observed with Fast Fourier Transformation. In-plane (x-axis) forces applied at the outlet bend significantly increase 39% compared to the corresponding forces at the inlet bend. Forces at the outlet bend along the y-axis (out-of-plane) were reduced by 26%, but the forces along the z-axis show a more moderate decrease of 7%. This study provides significant data essential to forming a correlation of two-phase flow-induced vibrations with multiple upward flow U-bend orientations.
... Khan et al., [22] discussed the Grid Convergence Index (GCI), that was calculated using Eq. (6), indicates if the results are within the asymptotic range of convergence if the grid resolution gets close to zero. ...
Multiphase flow induced vibrations is a serious safety issue in oil and gas industries due to its undesirable vibration. Currently, there is a lack of usable data that could help to predict the magnitude of multiphase flow induced vibration in pipe inclined at various angles. The objective of this paper is to determine the magnitude of vibration in two-phase flow in pipe at inclination angle of 0°, 30°, 45°, 60°, and 90°. Air to water superficial velocity ratio of 1.25 was selected for this purpose because it is the value that causes the flow to change abruptly from slug to churn flow and vice versa, depending on the orientation angle. The flow conduit is selected to be a stainless-steel pipe with an internal diameter of 52.5 mm (2 inches). The vibrations are monitored at the pipe section of length 38D from the inlet. Maximum longitudinal vibrations were observed in 0° orientation. 60° encountered the maximum amplitude vibrational frequency in transverse direction but being at a higher frequency. The suggested model can be used to evaluate the FSI impact of unstable vibrations for any piping orientation and diameter.
... The ANSYS Fluent theory guide (Ansys, 2013) asserts that the realizable k-« model exhibits noteworthy enhancements over other k-« models. For a comprehensive understanding of the equations involved, one can refer to the detailed formulations provided in references (Nichita and Zun, 2015;Khan et al., 2023). ...
Purpose:
Identifying the flow regime is a prerequisite for accurately modeling two-phase flow. This paper aims to introduce a comprehensive data-driven workflow for flow regime identification.
Design/methodology/approach:
A numerical two-phase flow model was validated against experimental data and was used to generate dynamic pressure signals for three different flow regimes. First, four distinct methods were used for feature extraction: discrete wavelet transform (DWT), empirical mode decomposition, power spectral density and the time series analysis method. Kernel Fisher discriminant analysis (KFDA) was used to simultaneously perform dimensionality reduction and machine learning (ML) classification for each set of features. Finally, the Shapley additive explanations (SHAP) method was applied to make the workflow explainable.
Findings:
The results highlighted that the DWT + KFDA method exhibited the highest testing and training accuracy at 95.2% and 88.8%, respectively. Results also include a virtual flow regime map to facilitate the visualization of features in two dimension. Finally, SHAP analysis showed that minimum and maximum values extracted at the fourth and second signal decomposition levels of DWT are the best flow-distinguishing features.
Practical implications:
This workflow can be applied to opaque pipes fitted with pressure sensors to achieve flow assurance and automatic monitoring of two-phase flow occurring in many process industries.
Originality/value:
This paper presents a novel flow regime identification method by fusing dynamic pressure measurements with ML techniques. The authors’ novel DWT + KFDA method demonstrates superior performance for flow regime identification with explainability.
... SPH stands out by providing inherent adaptability to complex geometries [20], dynamic interfaces [21,22], and material deformations [23,24]. Unlike grid-based methods [25], SPH employs a meshless framework that excels at handling free surface flows, fluid-structure interactions, and large deformations without the need for cumbersome re-meshing or rezoning procedures. This unique characteristic makes SPH particularly well-suited for simulations involving intricate or evolving boundaries, contributing to its efficacy in various scientific and engineering applications. ...
This research focuses on the computational modelling and comparative analysis of friction
stir welding (FSW) and stationary shoulder friction stir welding (SSFSW) applied to AA6061-T6
aluminium alloy. SSFSW, an FSW variant, employs a stationary shoulder and a rotating pin. This
study introduces a numerical model for both processes, using the innovative Smoothed Particle
Hydrodynamics (SPH) technique to capture their distinct thermo-mechanical characteristics. The aim
is to unravel its mechanics and multi-physics in SSFSW and compare it with conventional FSW. The
temperatures predicted by the model exhibited a close agreement between the advancing side (AS)
and retreating side (RS). Plastic strain patterns show that regular FSW is different from SSFSW. In
SSFSW, the strain is less, and the plastic area is comparatively slightly narrower. The distinct “ironing
effect” resulting from the stationary shoulder in SSFSW reduces the heat-affected zone (HAZ). Yet, it
maintains efficient plasticisation and material flow within the pin-affected zone (PAZ). This research
emphasises the significant impact of temperature, strain, material flow, and thermo-mechanical
characteristics on the quality of joints. Future suggestions include exploring process parameters more
broadly, examining dissimilar welding techniques and hybrid approaches, and comprehensively
investigating the diverse effects of SSFSW under various configurations and joint angles.
... In 2023, Umair Khan and et al. introduced a novel approach to identify flow regimes within a horizontal pipe through numerical simulations. This innovative technique involves leveraging fast Fourier transform and probability density function analyses (38). Unlike other studies in this field, which only modeled the two-phase flow in the horizontal pipeline and only considered technical factors, In this article, while simulating the system with commercial software, the effect of economic considerations was also included as a basic parameter in the design of horizontal pipelines in the seabed by the genetic optimization algorithm. ...
Industries such as oil, gas, and petrochemicals encounter a multifaceted challenge when it comes to the transportation of diverse substances through pipelines. The process relies heavily on two-phase flow, particularly in the case of seabed pipelines responsible for conveying oil and natural gas. In our study, the intricate dynamics of pressure fluctuations in horizontal seabed pipelines were comprehensively investigated through the use of simulation software. Nevertheless, the software employed had its limitations as it failed to account for economic considerations. To address this limitation, the integration of a genetic algorithm was undertaken, which encompassed constraints related to the initial investment, thereby contributing to the enhancement of cost-effectiveness in pressure drop calculations. Additionally, a novel parameter was introduced into the Baker model, leading to improvements in both technical efficiency and economic viability. It was observed that augmenting the weight of the initial investment constraint resulted in a reduction in the optimal pipeline diameter, following a third-degree curve. Furthermore, the research findings indicated that a 4% increase in water shear led to a 14.76% decrease in frictional pressure drop within vertical pipes and a 3.5% reduction in horizontal pipes. Conversely, as the gas-to-oil ratio was increased, frictional pressure drop surged by 116.87% in vertical pipes and 81.69% in horizontal pipes. This valuable information can be harnessed to optimize pipeline design and operations in the demanding underwater environments commonly encountered in these industries.
Aiming at establishing the transient flow characteristics of gas–liquid two-phase flow in high-undulation water pipelines, based on the bubble distribution law measured using physical tests, the bubble distribution law function was input into the hump-pipe fluid domain model, and CFD numerical simulation was carried out for different flow rates and different air contents. The CLSVOF two-phase flow model and the RNG k-ε turbulence model were used to analyze the flow pattern evolution and pressure pulsation propagation in the process of gas–liquid two-phase flow through a hump pipe. The results show that the bubble size has a lognormal distribution, the equivalent diameter is between 3 mm and 10 mm, and the evolution of the flow pattern in the hump pipe is complex and violent. In the horizontal pipe section, there are three main flow patterns: bubble flow, wavy flow and segment plug flow. In the vertical pipe, there are two main flow patterns, slug flow and churning flow, and the flow pattern is affected by the flow rate and the air content rate. When air bubbles or air pockets in the pipeline flow through a certain area, this leads to a steep increase and decrease in the pressure pulsation amplitude in the region, and the pressure fluctuation is extremely frequent. Compared with the water flow rate, the air content is the main factor affecting the relative pressure pulsation amplitude under the condition of a 0.15-air content operating mode, which is generally approximately two to six times that of the 0-air content operating mode. The results of the research should facilitate the prediction of stagnant gas pipeline system bursts and water hammer protection, providing a theoretical basis and calculation parameters.
