Pipe Geometry Research Articles

A comparison of gas-liquid two-phase flow behaviors between two offshore pipeline-riser systems with different geometric parameters: From view of flow pattern identification

The accuracy of data-driven flow pattern identification in gas-liquid two-phase flow depends on the quality of training data. If a high similarity of input parameters exists between the training and the application conditions, then, the trained identification model would be applicable. Aiming at pipeline-riser systems in offshore oil and gas fields, a comparative study of different laboratorial two-phase flow loops with different geometric parameters is performed. Statistical parameters commonly used for flow pattern identification are examined. Similarities and differences of parameter distribution in the feature domain are discussed. By analyzing the mean and amplitude scatter distributions, the feature region divisions for identification are determined. First through conditional judgment, and then through LS-SVM recognition, the identification model is constructed. The shortest sample length for effective identification of each flow pattern is analyzed through the relationship between the identification accuracy and the sample length. The typical severe slugging could be easily identified under different pipe geometry conditions even when the sample length is 1 s. The identification accuracies of oscillation, irregular and stable flow patterns vary under different application conditions.

Real Time Measurement of Multiphase Flow Velocity using Electrical Capacitance Tomography

Accurate and real-time measurement of fluid flow velocity is crucial in various industrial processes, especially when dealing with multiple phase fluids. Traditional flow measurement methods often struggle to accurately quantify the velocity of complex multiphase flows within pipes. This challenge necessitates the exploration of innovative techniques capable of providing reliable measurements. This paper proposes the utilization of Electrical Capacitance Tomography (ECT) as a promising approach for measuring the velocity of multiple phase fluids in pipes. The ECT technique involves the non-intrusive imaging of the electrical capacitance distribution within the pipe. By utilizing an array of electrodes placed around the pipe circumference, the capacitance distribution can be reconstructed, offering insight into the fluid flow patterns. By analyzing the temporal changes in the capacitance distribution, the velocity of different phases within the pipe can be estimated. To achieve accurate velocity measurements, an ECT system needs to account for the complexities introduced by multiphase flows. Various image reconstruction algorithms, such as linear back-projection and iterative algorithms like Gauss-Newton and Levenberg-Marquardt, are employed to reconstruct the capacitance distribution. Additionally, advanced signal processing techniques, such as cross-correlation analysis and time-difference methods, are used to extract velocity information from the reconstructed images. This paper presents an experimental investigation of measuring the velocity of multiple-phase fluids in pipes using the ECT technique. The study aims to address the challenges associated with different flow regimes, fluid properties, and pipe geometries by exploring advancements in electrode design, system calibration, and data processing techniques to enhance the accuracy and robustness of ECT-based velocity measurements.

Geodesic equations for guided wave helical path separation for a pipe bend

The sections of pipe bends are susceptible to wall thinning by flow-accelerated corrosion due to the sudden change in the fluid flow direction and velocity. Compared to existing screening approaches, Guided Wave Tomography (GWT) has been demonstrated to provide more accurate information about the defect. In GWT an inversion problem is solved, in which a forward model is used to predict a synthetic dataset for a given physical model. Two-dimensional (2D) forward models are preferred for the inversion scheme due to the feasibility of combining these with tomographic algorithms. Since 2D models resemble the GW propagation of a plate, they do not consider the cyclic nature of the pipe. To overcome this limitation, a robust helical path separation was introduced in Huthwaite and Seher (2015) for a straight pipe. However, it relies on time-reversing the measured wave field ϕ(t) as a function of the propagation distance xs,r from the source to the receiver. Although ray-tracing and grid-based methods are capable of computing the distance xs,r for complex geometries such as the pipe bend, they are complex and time-consuming. Hence, in this paper a straight forward approach is proposed to compute xs,r based on the pipe geometry and the geodesic equations of a torus. Then the computed distance xs,r is used for removing the helical path trajectories. Compared to the distance obtained by using the Hilbert envelope, the results show that the geodesic distances preserve the information of the wavefront of interest, including the focusing effect and the scattered wave field from a Hann-shaped defect. The technique is applied to experimental data and demonstrated to separate the wavefront of interest.

RETRACTED: Modeling a unified slug liquid holdup correlation based on a comprehensive analysis of entering bubble sharpness

Liquid-gas two-phase slug flow is the most complex flow pattern encountered in pipelines, wellbores, and cooling systems in various energy systems. Accurately predicting the slug liquid holdup (HLLS) is vital for the system design and operation because it is a crucial characteristic of slug flow that is closely related to the average liquid holdup and pressure drop. Most existing HLLS models have limited applicability due to a lack of a physical basis for slug aeration mechanisms. This study proposes a new dimensionless number SP to estimate the sharpness of entering bubbles at the liquid slug front and semi-empirically correlates SP to HLLS data, leading to the development of a unified HLLS correlation. We formulate this dimensionless number and its relations using 880 experimental HLLS data points, and the validity of the unified HLLS correlation is tested using 1050 independent data points. The developed semi-empirical model closely agrees with experimental data obtained by varying the fluid properties (0.03 mPa·s ≤ µL ≤ 966 mPa·s, 0.027 N/m ≤ σ ≤ 0.07 N/m) and operating conditions, such as the pipe geometry (1 in. ≤ pipe internal diameter ≤ 3 in., –10° ≤ θ ≤ +90°).

Thermal performance of energy barrettes in an urban environment

Thermal performance of energy barrettes in an urban environment

Optimisation of pipes with constant diameter using the heuristic optimality criterion

Background: Minimising internal pressure drop in pipes is crucial for energy efficiency of fluid flow applications. Numerous computational optimisation tools that are capable of modifying flow geometries to reduce the pressure drop have been developed. Among these is a comparably simple heuristic optimisation algorithm which mimics erosion and sedimentation processes based on the shear stress in the vicinity of the domain boundaries. Although this method succeeds in modifying flow geometries for reduced pressure drop, it allows the fluid domain to widen during the reshaping process. Therefore, a reported reduction of pressure drop is not only caused by an improvement of the flow path, but also by an increase in the domain width. However, pipes with a constant circular diameter are favoured in many applications because they can be easily manufactured. Methods: Here we combine the heuristic optimisation approach with a new geometrical constraint that kept the average diameter constant. This way, a reduction of pressure drop caused solely by the modification of the flow path can be assessed. We determined the applicability of the modified algorithm for 2D channel and 3D pipe geometries, conducting numerical simulations using the Lattice Boltzmann method with Reynolds numbers ranging from 40 to 500. Results: For all investigated cases, potentially optimal shapes could be derived at all tested Reynolds numbers. However, the shape originally derived at a simulated flow with Re = 40 yielded a smaller pressure drop even for flows at Re ≥ 100 than shapes derived specifically at these higher Reynolds numbers. Conclusions: This observed trend should be kept in mind when employing this approach as a simple way to improve channel and pipe layouts.

Experimental analysis of temperature and vapor core pressure for an annular heat pipe

The main contribution of this study is the effects of the operating conditions on the internal vapor pressure and temperature in an annular screen wick heat pipe, using distilled water as the working fluid. High-resolution pressure transducers, optical fiber distributed temperature sensors, and K-type thermocouples were employed to measure the internal and external temperatures as well as the local static pressures at different axial positions of the heat pipe. Temporal and frequency analysis using a one-dimensional continuous wavelet transform was performed on the differential pressure data to characterize flow behavior and infer the flow regime occurring within the heat pipe. The heat pipe was tested in multiple orientations with respect to the horizon (θ=0°, 45°, and 90°), heat loads (25, 50, and 75 W), and condenser coolant temperatures (Tw,in= 10 °C, 20 °C, and 30 °C). To estimate the vapor-phase flow friction factor for multiple Reynolds numbers, the Lockhart–Martinelli correlation was employed. This study provides critical experimental data and analyses for complex two-phase flow behavior in an annular wick heat pipe geometry. The thermal resistance and effective thermal conductivity were estimated as a function of the heat pipe orientation and power input. The experimental investigation revealed that power input and orientation influence both the internal vapor core and external surface temperatures, as well as the local pressure response. The outcomes from this study provide a valuable database that supports the advancement of heat pipe design, modeling, and validation.

A novel correlation models for predicting stress intensity factor of semi-elliptical crack in welded pipelines under cyclic internal pressure based on Bézier base XIGA

Pipelines are strategic infrastructures that are used for energy transfer in the world. Cracks in the residual stress field are the common defects in welded pipelines. These defects with cyclic internal pressure cause crack growth and decrease the fatigue life of pipelines. In this study, a novel correlation model is proposed to predict the stress intensity factor (SIF) of the semi-elliptical crack front in welded steel pipeline subjected to cyclic internal pressure. For this purpose, the Bézier extraction base extended isogeometric method is applied for numerical analysis and preparing a database of results based on the thermo elastic-plastic equation. Taguchi standard L25 orthogonal array was used as the analysis design to create the simulations. New correlations were proposed for SIF prediction using the multivariate linear regression method. These correlations were obtained based on a parametric study that included three parameters. These parameters are dimensionless crack geometry (a/c), pipe geometry (D/t), and loading (P/Pb) or (σres/E). The R-Square (R2) values of the presented model for the welding residual stress and cyclic internal pressure were obtained as 0.989 and 0.992, respectively. The results of FEM analysis with similar conditions were compared to the results of XIGA and correlation models to validate the presented method. The maximum difference between them is approximately 3.71% for the cyclic internal pressure, and 2.94% for the welding residual stress. RMSD for the cyclic internal pressure model is 0.49, and for the welding residual stress model is 0.51. Therefore, the proposed correlation models have acceptable accuracy in predicting the SIF and fatigue crack propagation rate of the semi-elliptical crack in the steel pipes.

Pipe geometry effect on fatigue cracking location of 90° elbows under in-plane bending

In this technical note, the criterion for fatigue cracking location for 90° elbows under in-plane bending is presented. The criterion is found using published elastic solutions and elastic-plastic FE analysis results. It is found that the most important parameter affecting fatigue crack location is the mean radius-to-pipe thickness ratio, rm/t. The circumferential crack at outer intrados is predicted for rm/t <4–5, and the axial crack at inner crown for rm/t >4–5. The exact value of rm/t depends slightly on the bend radius-to-mean pipe radius ratio. This conclusion is found to be appropriate from high cycle fatigue to very low cycle fatigue loading, and to be independent on the material.

Lattice Boltzmann solidification modeling of forced convection internal flows applied to Gen-IV nuclear reactor coolants

Generation-IV nuclear reactors involve novel coolants such as molten salts and lead. One of the issues that must be assessed with these coolants is the risk of solidification during reactor operation owing to their high melting temperature. However, the numerical simulation of solidification problems is computationally demanding. In this work, we assess the applicability of Lattice Boltzmann Method (LBM) to nuclear coolants solidification problems under laminar internal forced flow conditions. The double distribution Total Enthalpy-Partially Saturated Method is implemented in the open-source code OpenLB and compared against more standard Finite-Volume Computational Fluid Dynamics (FV-CFD) results, which uses the enthalpy-porosity Eulerian Multiphase method, in commercial code Star-CCM+. The test cases comprise the solidification of two fluids with significantly different Prandtl numbers, molten salt and lead, in a 3D pipe geometry in laminar flow conditions with an initial Reynolds number of 100. The solid interface advances from the cooled wall towards the bulk of the pipe reducing the area of flow passage as the transient evolves. Results of LBM velocity fields, solid fraction profiles, temperature fields, and pressure fields are in good agreement with FV-CFD results for both coolants. Furthermore, LBM stability and accuracy limits are independently explored for molten salts and lead using Two-Relaxation Time (TRT) and Bhatnagar-Gross-Krook (BGK) collision operators. Simulation time between FV-CFD and LBM is also contrasted for both coolants. In this work, LBM solvers use explicit time schemes with a regular grid, whereas FV-CFD solutions are able to include implicit time schemes and near-wall mesh refinement. For molten salt flows (high Prandtl number) FV-CFD allows for considerably larger timesteps than LBM, which is limited by the maximum lattice Mach number limitation and stability considerations. For lead flows (low Prandtl number), the implicit scheme in FV-CFD is limited in terms of accuracy for large timesteps due to the limiting Fourier-number. On the other hand, LBM does not present notable stability issues for lead and the lattice Mach number limit is not as relevant as for the molten salt case for this Reynolds number, allowing for faster simulation times than FV-CFD.

Frequency varying rheology-based fluid–structure-interactions waves in liquid-filled visco-elastic pipes

This contribution proposes a new rheology-based model for water-hammer wave propagation in visco-elastic pipes. Using a long wavelength analysis and a generalized frequency-dependent Hooke-law for the stress/strain relation, the pressure/longitudinal stress coupled wave system is derived. In this general framework, a visco-elastic Fluid–Structure Interaction (FSI) four equations model is derived by having four visco-elastic kernels associated with the non-local time response of the visco-elastic solid. The explicit dependence of these kernels with the material creep function and the pipe dimension is found. Considering a general linear visco-elastic rheology, the four visco-elastic kernels, and the corresponding creep function are explicitly derived in frequency and time-domain versus four visco-elastic parameters. For a given set of boundary conditions, a general analytical solution for the pressure/stress water hammer wave is obtained in frequency domain. The model’s predictions are successfully compared with experimental measurements as well as with other models adjusted to the same experimental data set by calibrating the model’s parameter. The proposed model can be used in many other contexts with the specific ability to distinguish the intrinsic visco-elastic rheology from the considered pipe geometry and boundary conditions.

Optimal insulation layer for heated water pipes under technical, economic and carbon emission constraints

Piping systems are a common element of thermal systems in several sectors. They usually have the function to deliver hot fluids for thermal processes and/or final uses, and they might be responsible for a large amount of heat losses, which results in higher primary energy consumption and carbon emissions, if adequate insulation layers are not designed and deployed. Finding the optimal insulation thickness is however not a straightforward process, since several technical, economic and environmental aspects enter into play. The present work investigates different optimisation approaches for determining the optimal thickness of insulation layers in civil and industrial piping systems, by introducing the concept of embodied energy and embodied carbon emissions of the insulation material, together with the economic evaluation of the investment associated with the insulation deployment. Several technical and economic characteristics are considered - e.g., pipe size, insulation materials, primary fuel, operating temperature, climatic conditions, fuel market price, country of origin of the insulation layer, etc. Results shows that the piping geometry, operating conditions and heating system strongly affects the optimal insulation thickness, while the climatic conditions have a little influence, especially for fluid operating temperature above 45 °C. Furthermore, the country of origin of the insulation strongly affects the net carbon savings achievable, due to the different embodied carbon emissions linked to the local energy mix used, and should be considered - e.g. by implementing a certification of origin mechanism, to correctly evaluate the emission reduction potential of the insulation layer deployment.

Evaluation of the different inner and outer channel geometry combinations for optimum melting and solidification performance in double pipe energy storage with phase change material: A numerical study

Phase change materials (PCMs) have become preferable among latent heat storage methods due to their high energy storage densities and low energy losses. These properties of PCMs make it possible to use them in applications such as thermal storage of solar energy, cooling of electronic equipment, energy storage for buildings, and cooling of engines. Double-pipe energy storage (DPTES) with PCM can be used in cases where the production and consumption times of the thermal energy obtained from sources such as solar energy, geothermal water, and waste gas do not match. The fact that the thermal conductivity coefficients are quite low is one of the obstacles to the commercialization of PCMs and their use in more applications. Double-pipe energy storage (DPTES) with PCM can be used especially in cases where the production and consumption moments of the thermal energy obtained from solar energy do not match. In studies on DPTES with PCM, methods including different pipe geometries, extended surfaces, different PCM materials, microencapsulation of PCMs, eccentric inner pipe placement, nanoparticle usage, and metal foam addition have been investigated to increase thermal conductivity. The novelty of this study was to examine the effects of different inner and outer channel combinations on melting and solidification performance. In this direction, nine different inner and outer channel combinations of basic geometric shapes were modeled. Among these combinations, the combination with the highest melting rate and the shortest charging time was determined. Afterward, melting and solidification analyzes were made at the different positions of the inner and outer channels for the combination selected, and the most suitable energy storage design was created to make the most efficient use of the existing heat source. The results of the analysis revealed that the optimum design for melting, and solidification performance was the triangle-in-square configuration. With this configuration, it was increased the melting rate by 1.1 times and accelerated the charging time by 20 % for a 40-minute charging period compared to conventional DPTES (circle-in-circle). In addition, for the melting and solidification periods, the inverted and vertical placement of the triangle in the square revealed the best results. It was observed that the effect of the relative positions of the square and the triangle on the solidification rate was negligible. It is predicted that the results given in this study will be useful in designing the most compatible inner and outer channel geometries to increase energy storage efficiency in DPTES systems.

Stress intensity factor of through-wall-cracked steel pipe wrapped with prestressed CFRP composites

Externally wrapped prestressed carbon fiber reinforced polymer (CFRP) composites are effective in cracked steel pipe repairs. In this study, the effects of pipe and crack geometry, CFRP properties, and prestress levels on the Mode Ⅰ stress intensity factor (SIF) were addressed quantitatively for a prestressed CFRP-wrapped steel pipe with a through-walled crack through dimensional and finite element (FE) analysis. Five hundred and ten FE models were established to analyze the effects of the parameters. The effects of radius and wall thickness on the SIF were interactional. The SIF was negatively correlated with the CFRP stiffness and decreased linearly with the increasing prestress. The ratio between the SIFs of a CFRP-wrapped cracked pipe and a cracked pipe was determined by the dimensionless CFRP stiffness. The SIF decreases with the increasing crack angle following the cosine function mode. The ratio between the SIFs of an inclined crack and an axial crack was determined only by the crack angle. The influences of pipe geometry, crack angle, and CFRP properties on SIF were independent of each other. An empirical equation for calculating the Mode Ⅰ SIF was proposed for the CFRP-wrapped thin-walled pipe with a through-walled crack. An accurate mechanical method to calculate the decrement of pipe substrate bearing internal pressure caused by prestress was proposed.

Turbulence spectra in natural and forced convection

Fourier spectra have been traditionally used to get insight into the flow structures of turbulence. In wall-bounded flows these are not reported usually in Kolmogorov units. In this paper the spectra are evaluated in these units to compare with the case of isotropic turbulence, to investigate at which distance from the wall flow isotropy is achieved. We have found that improvement of universality of the spectra in the near-wall region is achieved by evaluating the dissipative length scale from the total turbulence kinetic energy dissipation, rather than through the rate of isotropic dissipation as customary. The database of Lee and Moser [1] for flow in plane channel and of Pirozzoli et al. [2] for flow in a circular pipe have been considered. We have found similarities between pipe and channel flow up to a non-dimensional distance 0.2. Farther from the wall the spectra tend to become universal and similar to isotropic turbulence in channels, whereas the geometry of the circular pipe prevents universality. Large part of the paper is also focused on turbulent natural convection in rectangular enclosures. In that flow, comparison between velocity and temperature spectra allows to answer about possible differences in the slope of the inertial ranges. In this respect, the importance of the spectral bottleneck in the cascade of kinetic and thermal energy is stressed. The large amplitude of the bottleneck in the temperature spectra might be the cause for the k−4/3 spectral range observed at wall distances greater than the thermal boundary layer thickness, defined in terms of the maximum turbulent thermal energy production. Also in this flow evaluating the Kolmogorov length scale through the total dissipation yields better collapse of the spectral range with exponential decay on that of isotropic turbulence in the near-wall region. Flow visualisations and joint PDFs are used for deeper understanding of the complex physics of turbulent convection.

Impact of self-excited cavitating waterjet feeder pipe on acoustic and erosion patterns

The impact of the feeder pipe geometry on the dominant frequencies and erosion patterns induced by self-excited cavitating waterjets, SECJ, is studied using laboratory experiments. Complementary inspection of the bulk flow in the feeder sections is illustrated using averaged governing equations. The experimental results indicate that the feeder pipe length, L2, affects the acoustic characteristics of the waterjets. As an acoustic reflector, the length of feeder pipes induces distinct transmission losses, resulting in resonant intensity changes and reflectivity. The relatively larger section of the feeder section with respect to the upstream fitting led to the formation of a large-scale recirculation pattern due to a sharp shear layer from the incoming flow. This recirculation bubble may cover the entire or a fraction of the feeder extent depending on L2. Overall, the work offers insight into the design of required pipe system parameters to modulate peak resonance.

Narzędzie informatyczne do autogenerowania elementów stanowiska do sprawdzania geometrii rur

Narzędzie informatyczne do autogenerowania elementów stanowiska do sprawdzania geometrii rur

Airflow distribution law of multi-branch pipe of pneumatic rice direct seeder based on dimensional analysis

In order to investigate the flow characteristics and distribution law of airflow in multi-branch pipe of pneumatic rice precision direct seeder and obtain the mathematical model between airflow parameters and pipe geometry structure. In this study, the airflow flow law of the multi-branch pipeline of the pneumatic system was studied, the mechanism of airflow flow in the multi-branch pipe was analyzed, and it was clarified that the main factors affecting the airflow flow in the pipe, namely, air density, air dynamic viscosity, the total flow rate of the inlet branch pipe, the length of the closed end of the header, the inner diameter of the outlet branch pipe, and the outlet branch pipe spacing. Numerical simulations were carried out using Fluent simulation software to elucidate the cause of multi-branch pipes of uneven distribution of airflow in multi-branch pipes, the empirical equation among these factors and the flow velocity of the outlet branch pipe are established by dimensional analysis method. The bench test results show that the established empirical equations are applicable in the following ranges: 0.018 m3/s≤Q≤0.054 m3/s, 0.045 m≤d≤0.05 m, 0.075 m≤L≤0.125 m, 0.7 m≤Y1≤0.875 m (0.5 m≤Y2≤0.75 m, 0.36 m≤Y3≤0.45 m), the prediction accuracy can be controlled within 10% of the empirical formula, which can provide a reference for the prediction and optimization design of outlet velocity of the multi-branch pipe. Keywords: pneumatic system, multi-branch pipe, axial momentum conservation, Fluent, dimensional analysis DOI: 10.25165/j.ijabe.20231601.7663 Citation: Qin W, Wang Z M, Zhang M H, He S Y, Wang X G, Jiang Y C, et al. Airflow distribution law of multi-branch pipe of pneumatic rice direct seeder based on dimensional analysis. Int J Agric & Biol Eng, 2023; 16(1): 111–127.

Experimentally Based Numerical Simulation of the Influence of the Agricultural Subsurface Drainage Pipe Geometric Structure on Drainage Flow

The geometric structure of corrugated plastic pipes affects performance in agricultural subsurface drainage systems. To explore the influence of pipe geometry on flow field characteristics and the characterization of water movements, we developed a three-dimensional (3D) steady-state subsurface drainage model based on computational fluid dynamics (CFD). An analysis of the CFD and sand tank results indicated that the proposed model can accurately simulate the subsurface drainage process (R2 = 0.99). The corrugation structure parameters of the drainpipe, including the outside diameter, corrugation valley width and corrugation height, were taken as the objects for this study, and the influence of corrugation parameters on drainage discharge was orthogonally analysed. During drainage, the soil water initially collects in the corrugation valley and then approximately ninety percent of the water flows into the pipe through the bottom perforations; increasing the contact face area between the corrugation valley and soil can increase the flow rate of the drainpipe and the water table height above the pipe, which decreases the intersection position of the pipe and water table. The results of the analysis of the range and variance of the orthogonal experiment showed that the order of the primary and secondary factors influencing the drainage discharge was the outside diameter, corrugation valley width and corrugation height, with the outside diameter being most critical influencing factor.

Stress intensity factors of rectangular shape cracks for crack growth prediction

This study aimed at modeling cracks as a rectangular shape to predict crack growth for fitness-for-service assessments. Crack extension driving force was represented by a newly proposed line propagation stress intensity factor (LP-SIF), in which, not a point, but a line on a crack front was assumed to grow in the virtual crack extension for the elastic J-integral calculation. LP-SIF could be derived using the conventional point propagation SIF. It was shown that growth prediction of a rectangular crack using the LP-SIF was more conservative than that obtained by crack growth simulation, in which crack growth was calculated at each node along the crack front. In order to apply the LP-SIF for general use, LP-SIF solutions for various pipe and crack geometries and stress distributions were obtained by finite element analyses. The accuracy of the obtained SIFs was confirmed by comparing with analysis results obtained by two research organizations.