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To address the measurement accuracy challenges posed by the internal flow complexity in atypical circular bend pipes with short turning sections and without extended straight pipe segments, this study designed an experimental circular "S"-shaped bent pipe with a diameter of 0.4 m and a bending angle of 135°. Numerical analysis was used to determine the stable region for velocity distribution within the experimental segment. Furthermore, a novel evaluation method based on the coefficient of variation was proposed to accurately locate the optimal position for installing thermal mass flow meters on the test cross section. Additionally, a formula for calculating the pipeline flow rate based on velocity differences was derived. This formula considers pipeline flow as the dependent variable and uses the velocity at two points in the test cross section as the independent variable. Experimental validation on a primary standard test bench demonstrated that the flow rate calculated by this method had an error controlled within 0.625% compared to the standard flow rate, thus effectively verifying the method's high accuracy and engineering applicability. This research provides a new testing methodology and practical basis for flow measurement in complex pipeline systems, offering significant guidance for research and applications in related fields. [ABSTRACT FROM AUTHOR]

Protecting pipelines from impact load due to rockfall in mountainous regions is a challenging problem. Many researchers have studied rockfall characteristics and impact loading, however, there is still a lack of large-scale studies about the impact of rockfall on steel buried pipes. In this study, three large-scale tests were carried out to investigate the response of steel buried pipe, including rock penetration, impact force during penetration, circumferential strain, and vertical deformation of the pipe under different falling heights of a large spherical mass. In order to establish a well-based connection between prototype and large-scale models, a comprehensive scaling rule was applied in a way that the response of the prototype and large-scale models approached the same values. The results showed that increasing drop height causes an incremental rate of peak deceleration of the falling mass, and therefore larger impact forces were measured on the trench surface. The equivalent stiffness of the soil-buried pipe system during the impact load proved that the response of the system was mostly governed by the soil rather than the pipe. For this study, the through-wall bending stress of the pipe at drop heights of 3.5 and 4.5 m exceeded the recommended permissible range, and so failing to satisfy this design criterion. [ABSTRACT FROM AUTHOR]

When traversing through an active strike-slip fault, buried pipelines may be subjected to permanent ground deformation (PGD), causing large strains in the pipeline during an earthquake. The presence of bends near the fault-crossing zones may further increase the strain in the pipe. Moreover, it is well acknowledged that bends are the most vulnerable location to earthquake damage, mainly when compressive strain develops due to PGD. Hence, most design guidelines recommend constructing pipelines without field bends, elbows, and flanges crossing the fault zone. However, it is not always possible to provide only a straight segment of the pipeline, especially for blind faults where the location of the faults is unknown. Hence, the present study aims to investigate the response of buried continuous steel pipelines with field bends subjected to strike-slip faulting by conducting an extensive parametric study. A three-dimensional pipe-soil interaction model is developed in a finite element framework for this study. The pipeline response in terms of its maximum von-Mises stress and maximum longitudinal stress and strain due to fault crossing is studied for various influencing parameters such as pipe bend angle, soil strength, pipe burial depth, and distance of the fault trace from the bend. Based on the results obtained, suitable relationships in terms of modification factors over the response of a straight pipeline as a function of a few critical parameters are determined using regression analyses. It is concluded that providing bends to the pipeline can significantly affect its structural response when subjected to fault displacement when the fault trace is close to the pipe bend. The primary outcome of this investigation would be to suggest a simplified methodology to estimate the response of pipelines having field bends while crossing fault lines from the response of straight pipelines in a similar scenario. [ABSTRACT FROM AUTHOR]

Experiments on air-water two-phase flows in a horizontal U-bend placed in the vertical plane were carried out to investigate effects of pipe bending on the void fraction. The inner diameter and the bend radius of curvature were 8 and 24.3 mm, respectively, so that the dimensionless bend diameter was 6. The flow patterns dealt with were plug, slug and annular flows. The void fractions in the bend and the straight section were measured by using quick-closing valves and the void fraction distribution was evaluated with an image processing method. The applicability of available correlations for the void fraction in the straight pipe was also discussed. For the straight pipe, the void fractions of the plug and slug flows can be accurately evaluated using the Smith correlation, whereas in the annular flow regime the Cioncolini and Thome correlation and the Mauro et al. liquid film thickness model give better agreement with the data. The bend void fractions in the downward and upward flows agree well with those for the pipe diameter of 26 mm given in literature, implying that the diameter effect on the void fraction is weak. The Usui et al. void fraction correlation gives reasonable evaluation for downward flows. [ABSTRACT FROM AUTHOR]

This paper presents an analytical solution for thrust restraint analysis of buried pipelines subjected to internal pressures and thermal and earthquake loads. The proposed analytical solution is modified from the current approach, which does not include the effect of temperature or earthquake loads or the complexities of pipe–soil friction nonlinearities resulting from change in the direction of relative pipe-to-soil motions. The proposed analytical solution is validated using a finite-element model that accounts for longitudinal pipe-to-soil friction and soil stiffness against transverse movement of the pipe. This paper also includes two case studies using the approach presented in this paper: one is a steel pipeline with a 5.4-in. (0.137-m) diameter and a 45° bend in a nuclear facility subjected to high internal pressure and high temperature loading, and the other is a prestressed concrete cylinder pipe with a 72-in. (1.83-m) diameter and a 45° bend subjected to internal pressure and temperature and earthquake loads. Both case studies suggest that the demands on the pipe segments adjacent to the pipe bends are greater when we include temperature and earthquake loads. In addition, this paper also shows that the sequence of load application of temperature and earthquake loads may result in changes in the direction of friction along the length of the pipeline, which affect the internal forces in the pipeline. This paper presents a procedure for analysis of pipelines where a change of direction of friction is likely. [ABSTRACT FROM AUTHOR]

A computational fluid dynamic modeling framework is developed to quantify frictional losses, assess the energy efficiency of transport, and characterize the mixing behavior of methane-hydrogen blends across representative regions of a large gas network such as transmission, distribution, and household pipeline sections. The principal conclusions from the present study are: (i) The increase in the energy required for transporting hydrogen as methane-hydrogen blends depends on the volume fraction of hydrogen, the nature of the flow conditions, pipe diameter, pipe roughness and pipe bends. (ii) Pipelines that have larger surface roughness or smaller diameters or those with bend sections require greater energy for transporting gas blends. (iii) The methane-hydrogen gas blends develop a core-annular flow pattern under steady state conditions with the denser and more viscous methane flowing near the pipe wall as the annulus while the less dense and less viscous hydrogen concentrated more towards the mid-sections of the pipelines. [Display omitted] • Pipeline roughness increases transport energy requirements due to friction. • Larger diameter pipelines transport hydrogen with more energy efficiency. • Hydrogen content and flow conditions determine energy costs for transporting blends. • Hydrogen gas blends develop core-annular flow pattern under steady state conditions. [ABSTRACT FROM AUTHOR]

Decanter centrifuges are widely used in solid–liquid separation, and saving their energy consumption is very important. In this paper, a bend pipe installed at the end of the decanter centrifuge was designed to save energy, and the effect of different structural parameters of the energy‐saving bend pipes on the outlet velocity and the reaction torque was investigated. The results revealed that the outlet velocity and the reaction torque were reduced with the increase in the number of pipes, outlet area, and pipe length. Increasing the radial position had little effect on the outlet velocity, but increased the reaction torque. Decreasing the outlet area and increasing the radial position both weaken the separation performance of the decanter centrifuge. The best separation performance and reaction torque effect were achieved in a suitable structure. Furthermore, the turbulent intensity was reduced from 143% to 135% in the new machine installed with bend pipes. The energy‐saving efficiency dropped with the increase of the rotational speed and the value was 13.1% under 2500 rpm. The separation performance of the new machine was similar to that of the original machine, and the dewatering speed was increased with the increase of the axial position. [ABSTRACT FROM AUTHOR]

To improve the efficiency and protection level of combustible gas explosion relief in urban underground pipeline corridors, we built a 150 × 150 × 2000 mm³ transparent pipeline experimental platform to simulate underground pipeline corridors and studied the effect of different positions and diameters of explosion relief conduits on the side of the pipeline on the characteristics of the explosion of methane in the pipeline. The results show that the flame is twisted and deformed at the bend, increasing the contact area between the fuel and oxygen, thus causing flame acceleration. Wall conduit relief bend in the flame has a certain hysteresis, in the front end of the bend, and the back end of the pipe wall conduit were installed, the flame propagation time of 254 ms, and 200 ms, respectively, increased by 71 ms, and 17 ms, the delay ratio of 38.80%, 9.29%, respectively. When the front part of the pipe wall conduit pipe diameter of 60 mm, 80 mm, and 100 mm, the flame propagation time was delayed 71 ms, 82 ms, and 105 ms, the delay ratio of 38.80%, 44.81%, 57.38%, and the position of the front of the pipe wall conduit pipe diameter is larger, the lower the peak explosion pressure. [ABSTRACT FROM AUTHOR]

Objective Mixing hydrogen into natural gas will change the properties and flow state of the fluid, thus affecting the metering accuracy of the flowmeter. ANSYS Fluent was used to simulate the velocity distribution of hydrogen-mixed natural gas after bending pipe, and analyze that whether the existing installation conditions of orifice flowmeter and ultrasonic flowmeter are suitable for hydrogen-mixed natural gas pipeline. Methods Simulating the velocity field of hydrogen-mixed natural gas after single 90° bending pipe and double 90° bending pipe, and comparing the velocity distribution of hydrogen-mixed natural gas with different hydrogen content on the pipeline center line and some sections after the bending pipe to analyze whether the installation position of the flowmeter specified in the current standard achieves symmetrical velocity distribution for hydrogen-mixed natural gas, and to determine whether the length of the front straight pipe section of the installation position of the elbow back flowmeter stipulated in the current standard needs to be extended. Results(1) At the 44D and 50D sections after a single 90° bending pipe, the H2 molar fraction with 10%-30% H2 did not return to the symmetrical velocity distribution; (2) At the 44D section and 50D section after the double 90° bending pipe, the flow velocity with 10% H2 has returned to the symmetrical velocity distribution, while the flow velocity with 20%-30% H2 has not returned to the symmetrical velocity distribution; (3) At the 30D section after the double 90° bending pipe, the velocity with 10% H2 did not return to the symmetrical velocity distribution. Conclusions(1) For hydrogen-mixed natural gas, the length of the straight front section of the single bending pipe rear flowmeter stipulated in the current standard should be appropriately extended; (2) For 20%-30% H2, the length of the straight pipe section in front of the flowmeter after the double bending pipe should be appropriately extended; (3) When the orifice aperture ratio decreases, the length of the straight pipe section in front of the orifice flowmeter with 10% H2 should be appropriately extended. [ABSTRACT FROM AUTHOR]

Flow conditioners are widely utilized in pipeline systems to improve the precision of flow rate measurement in the pipeline systems of the offshore and subsea oil and gas industry. There is a lack of knowledge about the influences of the conditioners on the flow inside a bend pipe due to the measurement inaccuracy caused by geometries complexity. In this study, numerical simulations are carried out solving the three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations with the κ--ω SST model to investigate the large-scale flow characteristics inside a double bend pipe and the performance of a conditioner with a bundle of 19 tubes. The obtained axial velocity inside a double bend pipe flow with no flow conditioner are compared with those of the previously published numerical simulations results and experimental data as the validation study. Helical flow structures are found behind the double bend and effectively removed by the flow conditioner. The performance of the flow conditioner is evaluated based on the axial flow velocity profiles, the swirl intensities and the deviation from the flow inside a straight pipe. The effects of Reynolds numbers and the lengths of the tube bundle on the flow downstream the flow conditioner are discussed. [ABSTRACT FROM AUTHOR]

Buried medium-density polyethylene (MDPE) pipes are widely used for gas distribution systems in Canada and worldwide. When exposed to geotechnical hazards such as ground movements, these pipes can experience excessive distresses, leading to leaking or failure. This research investigates the effects of ground movement near a tee connection of MDPE gas distribution pipes. If the ground movement is parallel to a branch, the branch pipe experiences an axial force, and the main pipe experiences bending deformation/strains. The axial forces and the wall strains were investigated in this study using full-scale laboratory tests. Test results showed that the axial force on the branch and strains on the main pipe depend on the burial depth, backfill soil density, and the pipe diameter due to the effects on the shearing resistance of the soil. The soil shearing resistance was less for shallow buried pipes, resulting in a lower axial force in the branch but higher bending strain in the main pipe. The axial pullout resistance of the main pipe also contributed to the wall strains of this laterally loaded pipe at large displacements. The conventional beam-on-elastic foundation solution reasonably estimated the pipe wall strains within the linear range of deformations. Nonlinear analyses, including lateral and axial soil springs, are recommended to capture the nonlinear responses at large displacements. [ABSTRACT FROM AUTHOR]

This paper investigates the self-cleansing performance of an airlift pump with a U-bend. For this purpose, an experimental setup is used to assess the effect of air flow on the pump's ability to lift water and remove particles under different submergence ratios and particle concentrations. In addition, a simple yet accurate fluid mechanical model is used to interpret the experiments with individual particles and to predict the critical water velocity required for particle removal from the pipe bend. [ABSTRACT FROM AUTHOR]

Elbow pipes are widely used in many industries such as petroleum, chemical, and metallurgy. Of various elbow pipe forming technology, hot pushing pipe bending process is an efficient and economical one for processing elbow pipes. This paper introduced the technological process and plastic deformation mechanism of hot pushing pipe bending. Four deformation assumptions were proposed to describe the main deformation characteristics in the bending process. The proportional relationship between the bending deformation and the diameter expansion deformation was derived and the horn mandrel was designed. The forming process of the elbow was simulated and the metal flow in the forming process of the elbow was obtained. The results showed that controlling the axial compression and circumferential expansion in proportion is the key to getting constant wall thickness. By using the horn mandrel with variable curvature axis, it benefits the metal flowing uniformity from the concave side to the convexity, avoiding the increase of the inner wall thickness and the decrease of the outer wall thickness during pipe bending. Taking the minimum change rate and good uniformity of the concave side wall thickness as goals, the optimal process parameters were obtained, that is, the heating temperature is 750° Celsius, the pushing speed is 3 mm/s, the friction factor is 0.15, the bending angle is 45° and initial bending radius is 2.0 mm. It will play a positive role in revealing the pipe forming mechanism and have a guiding effect on production practice. [ABSTRACT FROM AUTHOR]

Designing a compact hydraulic pipe flocculator is a common challenge for various water purification and wastewater processes where space is limited. Various geometrical parameters are analysed to identify the most important parameters when designing an efficient system for a Reynolds number of Re D = 20, 000. A coupled CFD-PBE model is applied to a total of 123 geometrical configurations to simulate particle aggregation and breakage due to the local velocity gradients in the configurations. The shear present in the 90∘ pipe bends is the dominating factor in the final aggregate size and therefore the most important geometrical factor is the bend radius. Secondly, it is observed that the primary length, L 1 , has the second-largest impact as a linearly increasing particle diameter is observed along the straight pipe. Helically coiled geometrical configurations with no straight sections, L 1 = L 2 = 0, and a bend radius of r b ≥ 2 d h result in large particles as a constant but moderate cross-sectionally averaged turbulent energy dissipation is observed throughout the pipe. The largest volume-averaged particle size is observed for a configuration with a primary length of L 1 = 20 d h , a secondary length of L 2 = 0 and a bend radius of r b = 2.5 d h. • Linearly increasing particle aggregation during straight sections. • Bend radius is the single-most important geometrical parameter. • Helically coiled configurations shows promising results. • The largest aggregates are obtained with L 2 = 20 d h , L 2 = 0 and r B = 2.5 d h. [ABSTRACT FROM AUTHOR]

In this article, a comparative analysis is presented of the schemes for pipe billet shape alteration in traditional and sign-alternating layouts of forming mills. The scheme using an alternating bend of a pipe billet is considered. The deformed state along the edge of the center of the pipe billet folding is calculated for an electric pipe-welded rig 10–60 and a 50 × 1.5 mm pipe, revealing the need to test the scheme with a falling axial fiber of the pipe billet. To analyze the folding centers, the angle between the straight-line contact of the fixed point of the forming flower of the billet and the vertical axis of the molding in the section of the tubular billet was used. Of the 13 calculated schemes, one with a tangent angle of 50° was chosen. An analysis of the deformed state of the pipe billet edge for this scheme showed that the longitudinal deformation values do not exceed the allowable values and provide the specified forming quality. [ABSTRACT FROM AUTHOR]

The stability of pressure pipe bends is evaluated by the equilibrium between the thrust force and resistance forces in the current design, and the behavior of pipe bends is not considered. Force–displacement (F–D) relationships, which are used for predicting the displacement of pipe bends, include the performance of pipe joints in the design of pipe bends and shift the design method to a performance-based approach. However, F–D relationships have been proposed only under plane-strain conditions. The behavior of pipe bends cannot be represented in two dimensions. Therefore, in this study, the prediction method of the F–D relationship for buried structures is extended to a three-dimensional condition to improve the design method of pipe bends with thrust restraint. Lateral loading experiments on thrust restraint, using rigid thrust blocks and flexible thrust restraints with geogrids and gravel, were conducted in dry sand to investigate the lateral behavior of rigid and flexible thrust restraints and to obtain F–D curves with different dimensions of thrust restraint. The experimental results revealed that the deformation of the flexible thrust restraint had little effect on the lateral resistance force if proper dimensions of the thrust restraints were determined. Using the experimental results, the F–D relationship was formulated based on a hyperbolic curve. The proposed equations were able to predict the resistance force relatively well at small lateral displacements. In addition to the formulation of the F–D relationship, a new design procedure considering the pipe displacement and performance of pipe joints was developed by combining the proposed F–D prediction method and the joint separation model proposed in previous studies. [ABSTRACT FROM AUTHOR]

Although inlet bent pipes are usually adopted due to limited installation space, the influences of different bend pipes on the inlet flow characteristics and performance of centrifugal compressors are still unclear. The numerical simulation of a centrifugal compressor is established and validated by experimental results with the case of a straight inlet pipe. Then, the internal flow characteristics of the centrifugal compressor with a 90-degree bent pipe (p90) and Z-shaped bent pipe (pz) are simulated and discussed. The results show that the adoption of two inlet bent pipes reduces the performance of the centrifugal compressor to a certain extent, which reduces more greatly with pz, with a maximum reduction of 6.82% in pressure ratio and 14.83% in efficiency, respectively. The pressure ratio and efficiency reduction of the centrifugal compressor both increase with the increment of distortion degree, which maintains the increasing trend as the flow rate increases, and the maximum distortion degree of p90 and pz reaches 0.0351 and 0.0479, respectively. The reduction degree of the pressure ratio shows a power–law relationship with the distortion degree, while the reduction degree of efficiency shows an exponential relationship with it. The flow characteristics at the outlet section of the inlet pipe affect the flow field distribution at the inlet of the impeller, and the distortion area ranges of the total pressure and axial velocity at the inlet of the impeller are near 72°–144° in the circumferential direction for p90, while those of pz are close to 108°–180° and 288°–360°. When the flow with a high distortion degree enters the impeller, a large area with high turbulent kinetic energy is formed in the downstream flow channel, resulting in an increase in the flow loss. [ABSTRACT FROM AUTHOR]

This study discusses the collapse criteria for thermally treated line pipe and their bending interaction against collapse based on a full-scale test under external pressure with and without bending loading. The critical collapse strain in the pressure bending test was much higher than that estimated by the DNV-ST-F101 standard because it was calculated based on estimating collapse pressures without bending interaction based on specified minimum yield stress (SMYS) of design pipe in the standard. However, the collapse pressures without bending interaction in full-scale test was significantly higher than that of the estimation according to DNV-ST-F101 standard. The effect of the thermal heat cycle simulated anti-corrosion coating heating on line pipe collapse criteria is also discussed based on the change of yield stress of pre-strained and thermally treated material. As the maximum heat cycle temperature increases, the reduction of the compressive yield stress along circumferential direction by the Baushinger effect due to UOE process (U: U-ing, cold forming from a plate; O: O-ing, cold forming from the U shape; E: cold expansion to meet geometric tolerances) becomes small. It is thought that a DNV equation for estimating the critical bending strain to collapse will provide a more accurate estimation of the critical collapse pressure and strain for thermally treated line pipe when the collapse pressure is calculated considering the change of strength parameters due to the tensile pre-strain level and heat cycle temperature. [ABSTRACT FROM AUTHOR]

The thin-wall heat pipe is an efficient heat transfer component that has been widely used in the field of heat dissipation of high-power electronic equipment in recent years. In this study, the orange peel morphology defect of thin-wall heat pipes after bending deformation was analyzed both for the macro-3D profile and for the micro-formation mechanism. The morphology and crystal orientations of the grains and annealing twins were carefully characterized utilizing optical metallography and the electron backscatter diffraction technique. The results show that after high-temperature sintering treatment, the matrix grains of the heat pipe are seriously coarsened and form a strong Goss texture, while certain annealing twins with the unique copper orientation are retained. The distribution of the Schmid factor value subjected to the uniaxial stress indicates that inhomogeneity in the intergranular deformation exists among the annealing twins and matrix grains. The annealing twin exhibits a "hard-oriented" component during the deformation; thus, it plays a role as a barrier and hinders the slipping of dislocation. As the strain accumulates, part of the annealing twins may protrude from the surface of the heat pipe, forming a large-scale fluctuation of the surface as the so-called "orange peel" morphology. The 3D profile shows the bulged twins mostly perpendicular to the drawing direction, about 200–300 in width and 10–20 μm in height. [ABSTRACT FROM AUTHOR]

In an agile power grid environment, hydroelectric power plants must operate flexibly to follow the demand. Their wide operating range and high part-load efficiencies allow for multi-injector Pelton turbines to fulfil these demands as long as the water jet quality is maintained. The water jet shape is governed by the flow in the distributor system. Pelton distributor systems with axial feed can potentially reduce the costs of the power station. Providing the flow quality at the nozzle outlet challenges the design of such Pelton distributors. Therefore, numerical simulations are performed to optimise a parameterised Pelton distributor system with axial feed. The effects of geometric parameter variations on its performance are studied. The criteria to evaluate the flow in distributor systems are presented, which are applied to quantify the power losses and secondary flows. Additionally, the second law analysis illustrates where the losses are generated. Due to various pipe bends, all designs exhibit a distinct S-shaped secondary flow pattern at the nozzle inlet. The simulations reveal that the power losses are greatly reduced by shaping the initial part of the branch line as a conical frustum. Deviation angles of the branch line close to 90° allow for lower secondary flow magnitudes at the nozzle inlet. [ABSTRACT FROM AUTHOR]

We analyse the vortex structures of the mean turbulent flow field in a 90-degree bend pipe at bulk Reynolds number 5300 and radius of curvature 2.5 times the pipe radius. The Reynolds averaged Navier–Stokes equations are solved for the mean turbulent flow field in the finite volume framework of ANSYS Fluent. The Reynolds stress model is adopted for closure of turbulence quantities. Notwithstanding any scale resolving simulation, we show that a detailed exploration of the flow, turbulence, and vortex structures in the mean turbulent flow field inside a pipe bend is possible, through the paradigm based on complex conjugate eigenvalues of the velocity gradient tensor. The convex contour of the inner side of the bend is found to be the key vortex-generating surface. We find that the vortices start to gain swirling strength just after entering the bend. The strength further decays, rather than getting enhanced, within the remaining part of the bend. The outer side of the bend, on the other hand, appears to maintain a straining flow regime. Fluid particles move between the vortex region and the straining region through the strain-dominated vortex regions, the structure of which is also unveiled through the eigenvalue-based vortex defining paradigm. Both the straining and the vortex zone inject turbulence. However, the vortex-induced turbulence suffers significant dissipation within the bend region. The vortices transported downstream of the bend help in generating turbulence to recover the loss of turbulence in the bend region. [ABSTRACT FROM AUTHOR]

The analysis of pipeline flow fields and forces during inspection robot operation is the basis of most pipeline robot studies. In this study, the low-Reynolds-number k -epsilon model was used to numerically simulate the status of the pipeline flow field for an inspection robot operating in a pipe tee and pipe bend, which constituted the experimental group. A pipeline with no robot was set as the control group. The velocity, dynamic pressure, and static pressure of the pipelines were analyzed. A comparison of the results of the experimental and control groups revealed minor changes in the velocity and dynamic pressure of the pipeline flow field when the robot was operating; furthermore, the static pressure was found to increase significantly in the experimental group. Therefore, the presence of an inspection robot increases the load of the pipeline. This conclusion has significance for guiding the working state analysis of inspection robots in complex pipeline environments. [ABSTRACT FROM AUTHOR]

Decay of secondary motion downstream 180° pipe bends is investigated using large-eddy simulations for the bend radii of 1 ≤ r B / d h ≤ 3.375 at a Reynolds number of Re h = 10 000. The velocity and turbulence characteristics are validated against experimental data for a straight pipe section as well as against experimental and direct numerical simulations data for a 90° pipe bend. As the bend radius decreases, a larger magnitude of turbulence intensity is induced immediately downstream of the bend, and for the largest magnitude, the highest gradient of the decay turbulence intensity is observed. As a result, the recovery length needed to reestablish the velocity profile downstream of the pipe bend decreases. Turbulence is transported at a higher rate, indicating that the recovery of the velocity profile is driven by turbulence transport. Secondary motions are induced by the curvature of the pipe bend, and as the bend radius decreases, the magnitude of the secondary motion increases. The results show how the secondary motion decay in magnitude as the flow moves downstream the pipe bend. At the outlet of the bend, secondary motions are dominating at the walls and within the bulk flow. As the fluid moves further downstream, the secondary flows dominate close to the walls, and at a length of x / d h = 5 , a negligible difference in secondary motion is observed for the different bend radii. [ABSTRACT FROM AUTHOR]

Future deployment of 5G NR base stations in the 6425–7125 MHz band raises numerous concerns over the long-term impact on the satellite transponders located in geostationary orbit. To study this impact and understand whether 5G NR may cause adverse effect to the spaceborne receivers, the research which estimated the interference levels to the satellite bent pipe links was done. The study presents the evaluation of aggregate interference from 5G NR base stations located inside the victim satellites' footprints using Monte-Carlo analysis and calculation of signal-to-noise degradation and bit error rates of the fixed-satellite service (FSS) bent-pipe transponders for each scenario. The results of the study showed the feasibility of co-existence between 5G NR and satellite systems in the 6425–7125 MHz bands, and that no negative impact on the performance of the satellite links is expected. [ABSTRACT FROM AUTHOR]

The turbulent flow through a 90-deg circular pipe bend is investigated by carrying out the numerical simulations using the Reynolds-averaged Navier-Stokes (RANS) turbulence model in the present study. The objective of the present study is to evaluate the effects of different values of the curvature radius (Rc) and different Reynolds numbers (Re) on the flow development in the circular pipe bend by employing the explicit algebraic Reynolds stress model (EARSM) to resolve the Reynolds stresses, unlike the research carried out so far where the turbulence anisotropy has not been considered. The curvature ratio defined as the curvature radius to pipe diameter (Rc/D) is varied between 1 and 4 and the investigated Re range is from 10,000 to 60,000. The numerical model is validated by comparing the axial velocity profiles with the previous published experimental data. It is found that for the fixed Re and decreasing Rc/D, the axial velocity, the velocity perturbation, and the pressure difference in the cross section increase and vorticity becomes stronger. When the curvature ratio gets smaller than 2, the flow velocity profile becomes highly distorted. For the fixed Rc/D, the influence of the Re on the flow behavior is small for the investigated range of Re. [ABSTRACT FROM AUTHOR]

he feasibility of a new approach for pipe inspection has been explored using digital twins to enhance guided wave inspection. Guided wave inspection is well established in the oil & gas industry to remotely screen long lengths of predominately straight pipeline for corrosion. However, the inspection of complex pipe geometries remains a challenge. Nuclear fusion facilities are one such potential application. Fusion reactors have a network of many kilometres of service pipes with complex features, including multiple pipe bends. Some of these pipes could be used for actively cooling components such as the first wall and divertor. Guided ultrasonic wave inspection has the significant advantage of offering 100% coverage of the pipe wall over tens of metres of pipe from a remote test location. This is a highly attractive feature, particularly in the nuclear industry where it is important that human presence in high-risk areas is prohibited due to high radiation doses and temperatures. In this work, finite element wave propagation models have been investigated as digital twins of fusion reactor components. The models have been used to calculate bespoke excitation signals that will allow for full volumetric inspections of these complex pipes to be carried out from a remote location. For the first time, a digital twin technique has been developed that is predicted to successfully correct the distortion in guided wave signals caused by multiple pipe bends. The technique is predicted to yield an order of magnitude improvement in detection capability over conventional guided wave inspection. The digital twin technique presented here therefore shows significant promise for the future inspection of nuclear fusion power plant pipes. [ABSTRACT FROM AUTHOR]

The dynamic behaviors of a horizontal piping structure with an elbow due to the two-phase flow excitation are experimentally investigated. The effects of flow patterns and superficial velocities on the pressure pulsations and vibration responses are evaluated in detail. A strong partition coupling algorithm is used to calculate the flow-induced vibration (FIV) responses of the pipe, and the theoretical values agree well with the experimental results. It is found that the lateral and axial vibration responses of the bend pipe are related to the momentum flux of the two-phase flow, and the vibration amplitudes of the pipe increase with an increase in the liquid mass flux. The vertical vibration responses are strongly affected by the flow pattern, and the maximum response occurs in the transition region from the slug flow to the bubbly flow. Moreover, the standard deviation (STD) amplitudes of the pipe vibration in three directions increase with an increase in the gas flux for both the slug and bubbly flows. The blockage of liquid slugs at the elbow section is found to strengthen the vibration amplitude of the bend pipe, and the water-blocking phenomenon disappears as the superficial gas velocity increases. [ABSTRACT FROM AUTHOR]

The present study proposes a closed-form analytical solution for investigating the behaviour of buried adjacent pipeline subjected to ground heave induced from static pipe bursting underneath. The governing differential equation of the adjacent pipe is derived based on the concept of a beam (both Euler–Bernoulli's and Timoshenko's beam) resting on a Pasternak foundation. A Fourier series is used to solve the governing differential equation. The proposed solution is validated with the results obtained from earlier full-scale experimental works and finite-element-based numerical study. Further, a parametric study is conducted to investigate the influence of relative pipe–soil stiffness and pipe–pipe intersection angles on the adjacent pipe response during the pipe bursting process. It is perceived that normalised maximum pipe deformation reduces and normalised maximum pipe bending moment increases as the value of the relative pipe–soil stiffness increases. Further, for the present case, the maximum pipe curvature is obtained at a 35° intersection angle. Hence, it is understood that a 90° intersection angle is not always the critical criterion. The study will be useful in the preliminary design stage for obtaining quick and relevant results without performing rigorous numerical or experimental study. [ABSTRACT FROM AUTHOR]

The safety of the piping systems used in any nuclear or thermal power plant is essential to the environment and also to the people involved. Pipe bends are one of the critical components of the piping system. Hence, fatigue life estimation becomes primary focus when the designing pipe bends for their safety limits. The current study uses finite element analysis and the revised manson universal slope method to estimate the life of elbows under in-plane opening and closing cyclic bending moment. The estimated fatigue life was compared with low-cycle fatigue tests in the literature. The displacement of 20 mm was given as input to estimate the number of cycles. The principal stresses were obtained on the highly strained node of the finite element model to locate the crack and its direction accurately. The elbows with thinning have a reduction in the fatigue life of about 19%. [ABSTRACT FROM AUTHOR]

Thermal stress analysis is an integral part of the design and integrity assessment of buried pipelines. Pipe bends can be subjected to significant cross-sectional deformations due to bending moments induced by thermal cycles, compared to straight pipes, and therefore are the most crucial component of the pipeline's structural integrity. Fatigue fracture, which is the primary failure mode in pipelines under the thermal cycle, may occur at the crown region of the pipe bend in the form of a longitudinal crack. This specific failure pattern is primarily the result of excessive circumferential stress that may develop in the crown region of a pipe bend. The present paper suggests a novel approach to reduce the stress range at the crown region of pipe bends using carbon fiber-reinforced polymer (CFRP) wraps. This approach has been used in the pipeline industry to reinforce and repair corroded pipes. However, a very limited study on the use of CFRP wrap to enhance the mechanical behavior of undamaged pipe bends is available in the literature. This study employs an advanced finite element (FE) method to investigate the performance of buried pipe bends reinforced with CFRP composite wraps and subjected to thermal expansion-induced bending moment. A combined beam and shell-based FE model has been used in this study to ensure reasonable accuracy and remarkable computational efficiency for engineering practice. The FE results show that a 6 mm CFRP wrap around the pipe bend can decrease the von-Mises stress imposed by thermal expansion by up to 27.4%. In short, reinforcing pipe bends with CFRP wrap has a strong potential to decrease the stress range imposed in the pipe bend under thermal expansion-induced moments and consequently prevent fatigue failure in pipe bends. [ABSTRACT FROM AUTHOR]

A new remediation technique is proposed to mitigate large deformations imposed on buried pipeline systems subject to permanent ground deformation. With this technique, low-density gravel (LDG) with high porosity, such as pumice, is used as backfill in the trench containing the pipe near an area susceptible to PGD. This countermeasure decreases soil resistance, soil-pipe interaction forces and strain on the pipe as the pipeline deformation mechanism changes to a more desirable shape. Expanded polystyrene geofoam has been introduced to decrease the density of the pipeline backfill; however, LDG is more efficient regarding workability during construction, environmental effects, durability, fire safety, and cost-effectiveness. A series of centrifuge model experiments in which the pipelines were subjected to reverse faulting was conducted to evaluate the proposed method. During faulting, the axial and bending strain and pipe deflection were measured. A comparison of the responses of the remediated pipeline and the pipeline without remediation indicates that the proposed technique substantially mitigates the effects of large deformation. [ABSTRACT FROM AUTHOR]

Erosion of the elbow due to non-Newtonian viscous slurry flows is often observed in hydrocarbon transportation pipelines. This paper intends to study the erosion behavior of double offset U-bends and 180° U-bends for two-phase (liquid-sand) flow. A numerical simulation was conducted using the Discrete Phase Model (DPM) on carbon steel pipe bends with a 40 mm diameter and an R/D ratio of 1.5. The validity of the erosion model has been established by comparing it with the results quantified in the literature by experiment. While the maximum erosive wear rates of all evaluated cases were found to be quite different, the maximum erosion locations have been identified between 150° and 180° downstream at the outer curvature. It was seen that with the increase in disperse phase diameter, the erosive wear rate and impact area increased. Moreover, with the change of configuration from a 180° U-bend to a double offset U-bend, the influence of turbulence on the transit of the disperse phase decreases as the flow approaches downstream and results in less erosive wear in a double offset U-bend. Furthermore, the simulation results manifest that the erosive wear increases with an increase in flow velocity, and the erosion rate of the double offset U-bend was nearly 8.58 times less than the 180° U-bend for a carrier fluid velocity of 2 m/s and 1.82 times less for 4 m/s carrier fluid velocity. The erosion rate of the double offset U-bend was reduced by 120% compared to the 180° U-bend for 6 m/s in liquid-solid flow. [ABSTRACT FROM AUTHOR]

The Mw 7.8 earthquake that struck Kahramanmaras on February 6, 2023, caused significant damage to hydrocarbon and water transmission lines due to permanent ground deformations. Explosions occurred in the Kahramanmaras–Gaziantep Natural Gas transmission pipeline causing disruption of gas in the cities of Gaziantep and Hatay Fault Displacement Hazard. Water transmission pipelines were also damaged due to extreme fault offsets. This paper presents the findings from the earthquake affected zones. Particular attention was given to the performance of the 2600 mm diameter Duzbag–Gaziantep water transmission pipeline due to three reported challenges: (#1) The behavior of the pipe in the Duzbag tunnel, (#2) The pipe bend behavior at the fault crossing, and (#3) The pull-out of the pipe at valve room. Based on field observations, extreme damage forms at pipes were presented. A three-dimensional nonlinear numerical analysis was performed to simulate the observed damage of the reoriented water pipe at the fault crossing for Case #2. The nonlinear finite element model was able to capture the complex nature of the post-yield behavior of steel pipe as well as the damage locations along the pipe and their sequence of occurrences. As a mitigation measure for new pipes, the need for using flexible connections at critical crossings was highlighted. For existing pipes, the importance of developing secondary (by-pass) lines was emphasized. [ABSTRACT FROM AUTHOR]

In this study, we develop a three-dimensional computational model to explore the transportation and thermal characteristics of a bi-modal slurry flowing through a horizontally placed 90° pipe bend. The slurry comprises silica sand (SS) and fly ash (FA) granular, with varying combinations (65:35, 75:25, 85:15, 95:05, and 100:0). The computational investigation has been carried out for different carrier fluid's characteristics, including Prandtl number, and flow velocity (5 m/s), for efflux concentrations of C w = 40–60% for each mixture. Validated with experimental data, the computational approach employs a two-phase Eulerian-Eulerian RNG k-ε turbulence model and the kinetic theory of granular flow. Results reveal that the 65:35 combination exhibits minimal pressure drop, and the 100:0 combination shows maximum heat transfer characteristics, particularly with low-viscosity fluid (Pr = 2.88) and high particle efflux concentration (C w = 60%). The study also examines bend loss coefficients (K t) , concentration distribution, convective heat transfer coefficient (h), and Nusselt number (Nu) across different Prandtl fluids and efflux concentrations. [Display omitted] • 3D CFD modeling of bi-model slurry flow via horizontal 90° bend pipe is investigated. • Effect of different slurry mixture combinations on slurry flow characteristics is studied. • Slurry with 65:35 combination at efflux concentrations shows maximum efficiency. • Transportation of slurry with higher Pr demonstrates lower heat transfer coefficient. • Pressure drop, heat transfer coefficient and Nusselt number increases with C w. [ABSTRACT FROM AUTHOR]

This study aims at investigating the effects of local wall thinning on the cyclic plasticity behaviours of 90° back-to-back pipe bends, which are commonly utilised in flexible piping systems within plant facilities. Over time, the prolonged operation of these pipe bends may lead to wall thinning and a deterioration of their structural integrity. To understand the effects of such wall thinning, a 3D finite element analysis is conducted. Load interaction diagrams are generated using the Linear Matching Method, which considers the cyclic plasticity behaviours of shakedown and ratcheting. The investigation includes pipe bends with three different locations of local wall thinning: intrados, extrados, and crown. The pipe bends are subjected to steady internal pressure and various cyclic bending moments, including in-plane closing, in-plane opening, and out-of-plane bending. Moreover, comprehensive parametric studies are carried out for the pipe bend structures, varying the wall thinning rates. Semi-empirical formulas are derived based on the study results, enabling the prediction of limit load, shakedown limit, and ratchet limit concerning the position of the local wall thinning. Results and discussions have demonstrated the most detrimental combination of wall thinning type and loading on the structural integrity of the pipe bends and have provided valuable insights into the problems associated with deteriorated pipe bends. • The effects of local wall thinning on the cyclic plasticity behaviours of 90° back-to-back pipe bends are investigated. • The pipe bends with three different locations of local wall thinning is considered: intrados, extrados, and crown. • Shakedown and ratchet limit boundaries are analysed using the Linear Matching Method. • Critical loading combinations and the specific wall thinning locations that may lead to adverse effects are identified. [ABSTRACT FROM AUTHOR]

The flow-accelerated corrosion (FAC) behavior at different bending angles in bend pipe in simulated secondary circuit water environment of pressurized water reactor (PWR) was investigated. The results indicated that the FAC rates at different bending angles within the bend pipe strongly depended on the ferrite nanocrystallization degree and the mass transfer coefficients. Ferrite nanocrystallization played a dominant effect on FAC, and the mass transfer coefficient played a secondary role on FAC, causing the maximum FAC rate in bend pipe was transferred to the 45° position on the intrados. • FAC in elbow depended on ferrite nanocrystallization and mass transfer coefficient. • Ferrite nanocrystallization promoted corrosion and formed a three-layered oxide film. • Damage to oxide film due to the vortex promoted the corrosion of the SA106B. • Deformation between pearlite and ferrite induced localized corrosion. [ABSTRACT FROM AUTHOR]

• In this paper, a beam-shell coupling method based on VFIFE is proposed. The shell element is moved by applying torsion to the beam element. • The effect of torsion on bending pipe is mainly reflected in the downstream pipe. • The flexion propagation modes of dynamic and quasi-static flexion bend pipes in downstream pipelines are different. • When the torsion angle exceeds 5°, the initial collapse position will change from upstream to downstream. Torsion is a prevalent form of stress on pipe. This paper employs experimental and numerical methods to investigate the buckling behavior of thick-walled pipe under combined torsion and external pressure. Firstly, the beam-shell coupling method based on the vector form intrinsic finite element method is utilized to establish a model for torsion and external pressure in thick-walled pipe. The accuracy of the model is verified by the collapsible test of the scaled pipe. On this basis, the influence of different torsion angles on the failure mode and the failure mechanism of bending pipe under dynamic and quasi-static conditions are compared and analyzed. It is found that under different loading conditions, the buckling propagation mode of the downstream pipeline changes greatly. This phenomenon is mainly caused by the action of torque on the elbow. Finally, the effect of different torsion angles on the collapse pressure of the bend is investigated. [ABSTRACT FROM AUTHOR]

Computational studies of micron particle deposition is used to predict inhaled particles through the nasal cavity for understanding drug delivery or toxicology risks. To ensure reliable results in future studies, this study evaluated particle tracking schemes and determined the most appropriate settings for predicting micron particle deposition in a pipe bend and nasal cavity geometry. Micron particles were injected into a fully developed 90° pipe bend under a turbulent flow regime with Reynolds number, R e = 10,000, for comparison with existing data in the literature. Similarly, the micron particles were released into a more complex geometry, a human nasal cavity. The study found that although the high-resolution tracking is the default and preferred option set out by Ansys-Fluent, the 5 μ m particle tested travelled further than when the high-resolution tracking was off. This was rectified by setting the wall nodal velocity to zero. All particle tracking schemes performed well and were suitable for predicting deposition for particle diameters > 5 μ m , with high-resolution tracking and setting the wall nodal velocity to zero. However, the results become sensitive to the particle scheme when dealing with particle diameters ¡ 5 μ m. The lower-order schemes overpredict deposition, while the higher-order schemes have zero deposition in the pipe bend unless the wall nodal velocity is set to zero. This study provides a list of recommended settings to best simulate particle deposition efficiency in Ansys Fluent (version 2023R2), although future releases of the CFD software may incorporate these settings as default options. • Lagrangian time integration schemes were assessed for particle deposition accuracy. • An anisotropic turbulence dampening function is provided. • Additional commands are required to accurately approximate particle deposition. • Recommended discrete phase model settings for micron particle deposition. [ABSTRACT FROM AUTHOR]

The scattering of guided waves propagating through pipe bends is studied by means of normal mode expansion. First, the bi-orthogonality relationship for normal modes in pipe bends is derived, based on which the displacement and stress fields at the interfaces between the straight and curved parts are expanded with the normal modes in both parts. Then, based on the displacement and stress field continuity principle, the scattering problem is regarded as an eigenproblem of a transfer matrix, the solution of which gives the mode conversions at the interfaces. A case study is presented of the low-frequency longitudinal mode incident on a pipe bend, and it is found that the dominant mode conversions are L(0,1) reflection and mode conversion from L(0,1) to F(1,1). Finite element simulations and experiments are also conducted. L(0,1) bend reflection and mode-converted F(1,1) are clearly observed, which agrees well with the theoretical predictions. [ABSTRACT FROM AUTHOR]

One of the main problems of well operation is the risk of uncontrolled leakage of hydrocarbons into the environment. This problem is especially relevant for the long-term operation of wells. The idea for this study was inspired by a real industrial problem that the authors of the article were involved in solving. At several operating gas wells, an abnormal slope of the production tree occurred, which raised the question of the safety of their further operation. An analysis of known studies and current regulatory documents did not allow us to assess the safety of using a gas well based on the measured kinematic parameters of production tree deviations. A mathematical model for the deformation of a package of casing strings when the surface layer of the rock is displaced is developed in the article. A boundary value problem is formulated for differential equations of pipe bending on an elastic foundation. Based on the results of solving this problem, an unambiguous relationship was established between the maximum bending stress in the surface pipe and the angle of inclination of the production tree. The quantitative characteristics of the connection depend on the geometric and mechanical properties of the pipes and on the thickness and mechanical parameters of the formations. It was established that the existing inclination of the production tree can be achieved due to the beginning of the plastic bending of the surface pipe under the slickenside, which does not exclude the exhaustion of the safety margin of the surface pipe and indicates the possible operation of the casing string in a pre-emergency state. In general, the obtained results develop analytical approaches to assessing the behavior of underground structures of a production well in unstable soil bodies. [ABSTRACT FROM AUTHOR]

Aircraft pipelines are mainly used for the storage and transportation of fuel, hydraulic oil and water, which are mostly bent pipes of non-ferromagnetic materials. We used PPM (Periodic Permanent Magnet) EMAT (Electromagnetic Acoustic Transducer) to detect the defects at 90-degree bends. A simulation model was established by finite element software to study the propagation characteristics and defect detection capability of T (0, 1) mode-guided wave in aluminum pipe bend. In terms of propagation characteristics, the energy of the guided wave was focused in the extrados of the bend, and the guided waves in the intrados and extrados of the bend were separated due to the difference in propagation distance. Regarding defect detection capability, T (0, 1) mode-guided wave had the highest detection sensitivity for the defect in the extrados of the bend and the lowest detection sensitivity for the defect in the middle area of the bend. We designed a PPM EMAT for 320 kHz to verify the simulation results experimentally, and the experimental results are in good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

The hydrate particle aggregation is crucial for the flow safety of oil and gas pipelines. In this paper, coupled with the Eulerian-Eulerian model, k−ε turbulence model and the population balance model considering the hydrate aggregation and breakage, the hydrate aggregation process is studied in the bend, and the change of the average particle size under different hydrate volume fractions is discussed. The results show that the hydrate aggregation process includes two stages in the bend, namely the rapid growth and the dynamic equilibrium. In the rapid growth stage, both the hydrate concentration and particle size in the elbow increase rapidly, and the high concentration and large particle size regions on the inside of the elbow also increase significantly. Furthermore, two types of aggregates are formed on the inside of the elbow. One is a small amount of large-particle aggregates, while the other is the relatively high concentration of medium-size aggregates. Besides, the uniform suspension with a smaller concentration and particle size is distributed on the outside of the elbow, but there are also large-size particles that aggregate and adhere near the wall of pipe. As the hydrate volume fraction increases, the hydrate average particle size increases. High concentration hydrate reaches dynamic equilibrium faster during the flow process. [ABSTRACT FROM AUTHOR]

This paper presents a method for the seismic analysis of open‐ended pipe piles subjected to vertically propagating S‐waves, that considers kinematic interaction between the pipe pile and its external and internal soil. Following the presentation of the elastodynamic continuum model, which is based on the assumptions of linear elastic soil response and uniform soil conditions, we employ the derived solution to investigate the sensitivity of the seismic response of pipe piles to certain key problem parameters, such as pile slenderness or the relative stiffness of the pipe pile compared to its surrounding soil. We demonstrate that the bending stiffness of pipe piles is governing their seismic response, and that thin‐walled pipe piles offer the best material usage versus seismic performance ratio. The presented solution offers a low‐cost alternative to complex numerical simulations for preliminary seismic design purposes, such as the selection of optimal pipe pile section geometry. [ABSTRACT FROM AUTHOR]

The present work shows the slurry flow characteristics of bottom ash particulates having density 2219 kg/m3 at different Prandtl number through horizontal pipe bend. The simulation is carried out by adopting Eulerian two-phase model in conjunction with RNG k-ε turbulence model using available commercial software ANSYS Fluent. The transportation of solid particulates has the settling behaviour in the slurry pipeline and that leads to the sedimentation and blockage of the pipeline resulting more power and pressure drop in the pipeline. Therefore, it is important to know the transport capability of the solid particulates at different Prandtl fluids to minimise the pressure loss. The fluid properties at four Prandtl numbers i.e., 1.34, 2.14, 3.42 and 5.83 are used to carry the bottom ash concentration ranging from 40 to 60% (by weight) at mean flow-velocity ranging from 1 to 5 ms−1. The obtained computational results for pressure drop are validated with the published data in the literature and found in good agreement. The findings show that the pressure drop rises with escalation in flow velocity and Prandtl number for chosen efflux concentration range. The bottom ash particulates flowing at higher Prandtl fluid experiences less pressure drop through bend cross section in comparison to bottom ash particulates flowing at low Prandtl fluid. Finally, the contours of granular pressure, granular temperature and wall shear stress are predicted and discussed in details through the bend cross section to understand the complex slurry flow for chosen Prandtl numbers. Granular pressure P ∗ distribution for 300-μm particle at V m = 5 ms−1 and efflux concentration: C w = 50%. [Display omitted] • 3D CFD modeling of slurry flow via horizontal pipe bend is investigated. • Effect of different Prandtl number on slurry flow through pipe bend is studied. • Effect of particle size and flow velocity on slurry pressure drop is presented. • At lower Prandtl number, maximum granular pressure and temperature is found. • Larger particle is found to have higher wall shear stress. [ABSTRACT FROM AUTHOR]