Pipe Bend Research Articles

A novel relaxed modified pipe hydrodynamic model for mixed flow simulation

In this study, we propose a novel modified pipe hydrodynamic model with a partial relaxation approach and develop a corresponding numerical algorithm within the framework of the finite volume method for its computation to enable robust, accurate, and comprehensive pipe modeling. The proposed numerical model provides some key improvements compared to existing numerical schemes for simulating mixed pipe flows: (1) it is capable of preserving both moving- and stationary-water steady states, and (2) it effectively reduces post-bore oscillations while maintaining second-order accuracy in the non-pressurized regime for unsteady pipe flows. Such improvements have been verified against theoretical and experimental data through tests involving both smooth and sharp-gradient steady and unsteady flows across various regimes in straight and locally bent circular pipes, which are fundamental elements of stormwater drainage, sewage networks, and industrial process pipelines. The proposed pipe flow model can be further improved regarding post-pore stability by utilizing specific post-bore oscillation suppression techniques, and it can be integrated into a practical hydraulic modeling tool for pipeline networks in future work.

Enhancement of a heat pump's efficiency COP operating on the water-soil principle

AbstractGeothermal energy is increasingly promising for residential use due to rising energy costs and environmental awareness. This work experimentally examines the impact of pipe distribution on the heat pump's performance at varying temperatures for both the incoming water and the ground. The pipes are buried in the soil, distributing them on layers of varying depths up to a depth of 2 m, separated by insulating layers. The quantities of heat gained in the evaporator and released in the condenser are calculated to determine the coefficient of performance of the heat pump. It was found that at the same temperature, the total heat loss in the soil is larger in the case of water entering from the bent pipe towards the great depth compared to water entering from the direct pipe, but the heat gain is larger in the case of water entering from the direct one.

Creep fatigue life prediction of pipe joints under complex bending-torsional loading using large-scale nonlinear structural analysis

With the expansion of clean energy, thermal power plants will be used as a load-following power plant. Thus, temperature and strain variations will occur during load fluctuations including start and stop of operation, and large-diameter pipes will be damaged by fatigue in addition to creep due to internal pressure. Especially, in a bent pipe such as an elbow pipe, bending and torsion are simultaneously applied. Therefore, it is important to predict the creep fatigue life in a bending and torsional stress environment. In this study, analysis method for creep fatigue life using Norton’s law, ductile exhaustion law, and Manson-Coffin’s law is proposed. Next, the proposed method was applied to the prediction of creep fatigue life of the test samples for thermal power plant piping, and the validity of the proposed method was verified by comparing creep fatigue life obtained by proposed method and that obtained by an experiment. In addition, the proposed method is applied to the prediction of creep fatigue life with load fluctuations and investigation of the effects of load fluctuation interval on creep fatigue life.

Enhanced elastic stress solutions for junctions in various pipe bends under internal pressure and combined loading ([formula omitted] pipe bend, U-bend, double-bend pipe)

Piping systems in nuclear power plants normally operate under high pressure and high temperature. To efficiently manage space within these systems, pipe bends are extensively used. However, the welded joints connecting these pipes may be susceptible to flaws due to weld residual stress, transient loads, and operating environments. When flaws are present in such areas, analytical evaluation of flaws is to be carried out based on fracture mechanics parameters such as stress intensity factor. To calculate the stress intensity factor, distributions of the elastic stress are required. Therefore, this paper presents closed-form approximations of elastic stress in the junction between a pipe bend and a straight pipe under internal pressure. Review of the existing elastic stress solutions for estimating the stresses in pipe bends was carried out analyzing their limitations. Based on those limitations elastic stress solutions for thick to thin wall pipe bends were proposed and were validated against finite element (FE) analysis for thick-wall to thin-wall pipe bends under internal pressure and combined loading (i.e. internal pressure, in-plane bending, out-of-plane bending inflicted simultaneously). 90° pipe bend, U-bend and double-bend pipe configurations were considered and showed good agreement with the FE results exhibiting less than 5.8 % discrepancies. The accuracy of the elastic stress solutions for pipe bends provided in the existing code are summarized and validated in the appendix as well.

Mechanism and application of drill pipe bending induced borehole collapse in soft coal seam drilling

AbstractGas extraction drilling is a necessary measure for managing gas hazards. For soft coal seams where gas extraction drilling holes are prone to collapse, it is believed that drill rod disturbance is the main cause of hole collapse. This study proposes a research approach to reduce wall stress by optimizing the drill rod structure. Through theoretical analysis, numerical simulation, and industrial tests, a stress model for the drill rod inside the hole was established, and a wall stress equation was derived. The effects of various parameters on wall stress were analyzed. The study suggests optimizing the drill rod structure to reduce the disturbance‐induced wall stress. SolidWorks was used for drilling stress simulation, and a four‐winged concave groove drill rod was developed. After strength verification, comparative industrial tests were conducted. The research results show that as the line density increases, the wall stress of the drilling hole increases. As the length of the suspended section increases, the wall stress initially decreases and then increases. With increasing drilling thrust, wall stress increases linearly, and the growth rate is greater with a larger diameter difference between the drill hole and the drill rod. Numerical simulation results indicate that the critical point maximum stress at the hole entrance, the critical point maximum stress at the hole bottom, and the average stress at the bottom section of the four‐winged concave groove drill rod with a concavity of 5 are significantly reduced compared to those of circular and grooved drill rods. Industrial test results show that using the four‐winged concave groove drill rod significantly reduces the extent of hole collapse. This study provides a reference for addressing the issue of hole collapse in gas extraction drilling for soft coal seams.

Approach Based on Response-Surface Method to Optimize Lining of Dies Used in 3D Free-Bending Forming Technology

In three-dimensional free-bending forming (3D-FBF), the tube is not overly constrained, and the plastic deformation behavior and forming quality of the bent tube are significantly affected by the critical structure of the forming die lining. However, the effects of die-lining structural parameters on the tube quality, and a method to determine the combination of die-lining structural parameters is yet to be devised. This study aims to propose a new framework that allows one to understand the effects of various die-lining structural parameters on tube quality and to propose the best combination of die-lining structural parameters. First, finite-element modeling is performed to simulate 3D-FBF and examine the effects of individual die-lining structures on the quality of tube formation. The simulation results show that the deformation-zone length and die gap are positively correlated with the tube-section distortion and wall-thickness variation, whereas it shows an opposite trend with respect to the bending radius. Additionally, the lining chamfer radius of the bending die and the guide lining chamfer radius minimally affect the tube forming quality. Subsequently, the optimal die-lining structure is obtained using the response-surface method. The tube cross-sectional distortion rate reduced from 2.73 to 2.53% after the die lining is optimized. Additionally, the average inner-wall thickness reduced to 1.06 mm, whereas the average outer-wall thickness increased to 0.97 mm. This paper proposes a method for optimizing the forming-die-lining mechanism and for improving the tube forming quality in 3D-FBF.

DESIGN AND MANUFACTURE OF BENT AND VARIABLE SECTION TUBES MADE OF FRP COMPOSITE

Manufacturing of bent composite tubes with variable cross-section is a challenge. The traditional process in composite materials uses retractable mandrels that in case of inflated or bent tubes cannot be applied. The tubular composite elements are often used in high performance bicycles, in the manufacturing of frames, handlebars, saddle pipe supports, etc. This paper presents research on the design of a Mountain Bike (MTB) riser handlebar made of Fiber Reinforced Polymer (FRP). The handlebar is numerically analyzed to estimate the most suitable stacking sequence of Carbon Fiber Reinforced Polymer (CFRP) layers. Depending on the safety standard of bicycle handlebars, a case of longitudinal bending tests was numerically evaluated. Comparing the weight of the CFRP handlebar with the steel handlebar of the same shape, the mass reduction is 5.2 times. The obtained results indicate a two-fold reduction in the weight of the handlebar if it is compared to a handlebar made of aluminum alloys. The research also presents the manufacturing process of the composite mold, and CFRP tubular element. Prepreg CFRP materials are used to manufacture the handlebar, the employed technology being the vacuum bag forming and autoclave curing process.

Research on the Internal Flow Properties of the Bending Pipeline Based on the CFD

Abstract Pipeline connection is the main connection of hydraulic parts. For the study of pipe diameter, turning Angle and the turning radius of pipe, the influence law of the internal flow characteristics. this paper adopts CFD 3D simulation technology to explore the influence law of 5 kinds of bending radius, 6 kinds of bending Angle and 4 kinds of pipe diameter on the pressure loss of the pipeline. The results show that there are pressure difference and velocity difference in the inner wall and the outer wall of the bend, due to the impact of the fluid inertia force on the bend, when the fluid flows in the bend. As bending radius and pipe diameter increases, the pressure difference and speed difference of the inner and outer walls at the turning point of the pipeline are reduced, the local pressure loss at the bending is reduced, the internal pressure loss of the pipeline is reduced, and the flow is more uniform. With the increase of bending angle, the pressure difference and velocity difference of the inner and outer walls of the pipeline bending increase, the local pressure loss increases, and the overall pipeline pressure loss increases. The research results of this paper can provide some reference for pipeline hydraulic design and optimization.

Parameter Calibration of Chaboche Kinematic Hardening Model by Inverse Analysis Using Different Optimization Methods in the Case of Pipe Bending

Drag link is one of the important parts in steering system used in automotive. The ball joint, ball joint housing, and pipe compose the drag link. In this study, finite element analysis is used to simulate the deformation process. St 52 steel material is used. A yield criterion, an associated flow rule, and Chaboche’s kinematic hardening rule were used in the finite ele-ment simulations of processes involving high plastic deformation. A series of low-cycle ten-sile/compression tests is performed to determine the parameters of Chaboche’s kinematic hardening rule. The success of the simulation results depends on the more accuracy of the finding parameters. Some optimization methods are used in the calibration progression of these parameters and the results are compared. For the purpose of optimization, the angle of the pipe after bending is set as 16.6 as soon as possible. As design variables, the Chaboche kinematic hardening rule parameters were adjusted. Consequently, calibrated parameters were obtained for St52 pipe bending. By analysing and verifying the candidate points, opti-mization methods are compared. The optimum parameters are determined as YS=350 MPa, C=2984.3 MPa, and =100 while their initial values are YS=373.806 MPa, C=4016 MPa, and =94. It is concluded that the optimization process gives more consistency in the bending process.

Enhancing gas-liquid mixing effect in pipelines: Experimental and numerical investigations of blind tee and traditional elbow

Blind tees, as typical upstream component for multiphase flow measurements, can promote the gas-liquid mixing in pipelines. However, detailed investigations on the mixing mechanism in blind tees are still scarce. This study employs a combination of experiments and numerical simulations on bubble flow in bend pipes to analyze two-phase flow dynamics in both the traditional elbow and blind tee. Firstly, the swirling phenomena at the outlet of bending structures are revealed using the measured flow images, and the dominant modes of gas distribution are extracted with proper orthogonal decomposition method to conduct a low-dimensional spatiotemporal analysis. Then, the mixing mechanism and vorticity distribution in different bending structures are compared using numerical results. Finally, the influences of bending structures and gas-liquid flow conditions on the mixing performance are comprehensively assessed. Results indicate that blind tee has a better mixing performance than traditional elbow, which significantly improves the gas distribution uniformity at the bend outlet. With the increase of volume gas content, the vortex intensity and frequency at the blind tee outlet increase, resulting in an increase in the uniformity of gas distribution. Moreover, the blind tee exhibits a shorter distance of turbulence dissipation than the traditional elbow. Therefore, a more uniform and stable bubble flow can be obtained within the range of 6D-8D downstream of the blind tee.

Numerical and experimental investigations on influence of spherical hinge mandrel on deformation characteristics of large diameter tube in small-radius NC rotary bending

Numerical and experimental investigations on influence of spherical hinge mandrel on deformation characteristics of large diameter tube in small-radius NC rotary bending

Optimization of water supply parameters for enhanced thermal uniformity in aquaculture ponds under varied working conditions: An experimental study

Aquaculture ponds are critical for the successful rearing of fish larvae, and achieving consistent temperature distribution within these systems is essential for optimal growth conditions. This study explores methods for precise temperature regulation on both the water and atmospheric sides of the pond ecosystem. Based on the original design, systematic changes were made to parameters such as water supply pipe layout, bend angles, perforation rates, and working conditions. Metrics including average temperature, average temperature difference, and extreme temperature difference were utilized to extensively discuss the impacts of these parameters. Through this, temperature distributions across five distinct water supply layouts were analyzed, and the impacts of four different bending angles and perforation rates were evaluated using optimized configurations. Our findings demonstrate that a water supply layout radius of 2000 mm, coupled with a 60° bending angle and a 25 % perforation rate, increased overall temperature uniformity in the pond by 5 %. Additionally, seasonal variations significantly impact temperature distribution in ponds, particularly with different extreme temperature differences observed in winter and summer. Compared to the transitional season and summer, the average temperature difference in the pond during winter decreased by 30 % and 45 %, respectively. It was further revealed that winter conditions naturally yield more uniform water-side temperatures, making seasonal fluctuations irrelevant in determining optimal perforation rates. After the implementation of a water agitator, the average extreme temperature difference decreased from 0.6 K to 0.52 K. In the shallow water layer, the water agitator reduced the extreme temperature difference in the pond by 26 %. The use of water agitators has enhanced thermal uniformity in ponds, thereby improving the growth environment for fish larvae and providing valuable insights for environmental management in aquaculture.

Development of an improved limit pressure solution for shape-distorted 90o pipe bends with through-wall circumferential cracks

PurposeThis paper presents the approximate limit pressure solution for shape-imperfect and through-wall circumferential cracked (TWCC) 90° pipe bends at the intrados region. Finite element (FE) limit analysis was used to estimate the limit pressure by considering the small geometrical change effects.Design/methodology/approachThree-dimensional (3D) geometric linear FE methodology was implemented to investigate the limit pressure of structurally deformed TWCC 90° pipe bends. The material considered in the analysis is elastic perfectly plastic (EPP). The limit pressure of TWCC shape-distorted pipe bends was predicted from the corresponding internal pressure when von-Mises stress was equal to or just exceeded the material’s yield strength for all the models. The theoretical solution which was published in the literature was used to evaluate the current FE approach.FindingsOvality Co and TWCC at the intrados region caused a considerable impact on pipe bends, while the thinning? Ct produced a negligible effect and hence was not included in the analysis. With the combined effect, the bend portion of pipe bend experiences substantial influence, and the TWCC effect consequently increases with 45o, 60o and 90o crack angles and decreases the limit pressure of pipe bends. An improved closed-form empirical limit pressure solution was proposed for TWCC shape-distorted pipe bends at the intrados region.Originality/valueIn the limit pressure analysis of 90° pipe bends, the implications of structural irregularities (ovality and thinning) and TWCC have not been examined and reported.

Optimization of water supply parameters for enhanced thermal uniformity in aquaculture ponds: An experimental study based on orthogonal experimental design

The temperature distribution in aquaculture ponds plays a crucial role in the rearing of fish larvae. To achieve a more uniform temperature distribution in the pond and alleviate the problem of thermal stratification, precise control of pond temperature is essential. A recirculating aquaculture pond was taken as the test object. Single-factor experiments and orthogonal experiments were conducted to comprehensively test the aquaculture pond's water supply pipe layout, bend angle, perforation rate, and environmental conditions. Three evaluation indicators were used to analyze the temperature distribution of the aquaculture pond under various water supply pipe structures, leading to the identification of optimal structural configurations. The optimal structure I, obtained from single-factor experiments, was determined to be 2.5 m, 50 %, and 60°, while the optimal structure II, derived from orthogonal experiments, was 1.25 m, 75 %, and 30°. Both optimized structures exhibited significant temperature fluctuations in the pond during the summer season. However, Structure II demonstrated the lowest average temperature difference in the winter season, indicating its superior adaptability during winter. Moreover, Structure II could provide higher temperatures for shallow areas with depths greater than 600 mm, making it more suitable for fish larvae cultivation. Additionally, local devices effectively decreased temperature variations by 17.5 % within the pond. Furthermore, energy consumption output was evaluated for different operational conditions. The results showed that Structure II had the lowest energy consumption output during the summer season. In contrast, during the winter season, the energy consumption output increased by approximately 12 %, indicating significant energy-saving potential in aquaculture ponds during winter.

Study of the thermal effect of hot and cold working on the mechanical properties of medium carbon steel

Medium carbon steel is widely used in industries due to its favourable strength and flexibility. However, they are highly prone to deformation processes that affect their impact resistance and corrosion rate. This research examines the effects of hot and cold working on the mechanical properties of medium-carbon steel. Experimental tests were conducted on medium carbon steel samples subjected to hot and cold working treatment procedures via funnels for the hot working. Deformation techniques such as rolling and bending are employed by subjecting the materials to a high temperature of 900oC. At the same time, in this study, cold working uses room temperature between 0oC to 22 oC for both rolling and bending. The results show that hot bending improves the hardness property in the bending analysis, having 185.64, as opposed to cold bending, which is 174.33. It can be seen that the cold rolling treatment of medium carbon steel increases the hardness property by 179.84 compared with hot rolling techniques, which have a hardness of 161.63. The results from the rolling test show that the tensile stress at the yield point of the zero slopes is lower during the hot working process, having 598.05090 MPa, compared with the cold working results of 665.43718 MPa. However, the results of the elasticity modules show that hot working increases it with a value of 32885.24170 MPa compared with 28923.17810, respectively. It can be concluded that parameter optimization of the specification of medium carbon steel determined the specific treatment needed for the manufacturing industry to produce quality materials.

Study on secondary motions in supersonic boundary layers of a bent pipe

The present study employed direct numerical simulation to investigate the supersonic flow of Mach 3 in a bent pipe with a curvature of 0.0825, elucidating the dynamic mechanism of secondary motions within the turbulent boundary layer. The findings indicate that the compressible flow, affected by the wall curvature, is differentiated into several motion patterns as the bending angle increases: a portion of the outer fluid close to the wall, driven by the circumferential pressure gradient, moves inward through the lateral wall, causing an increase in the mass rate toward the lateral boundary layer and promoting the circumferential transport of energy and vorticity; other outer fluids at the start of the bent section, due to the centrifugal force, approach the wall to form a thinner boundary layer downstream; meanwhile, the fluid near the inner wall experiences the expansion, followed by the flow separation and reattachment at a bending angle of 14.6° and 22.0°, respectively, which induce a shear layer that develops from the inner end point toward the mainstream center, gradually reshaping the high-speed flow area within the pipe cross section into a U-shape, and enhancing the vorticity and temperature field of the inner region. Additionally, this study reveals a remarkable phenomenon that the separated flow in a localized inner region forms a rotating field, inducing vortices distinct from the mainstream Dean vortices in the low-speed flow region enclosed by the shear layer.

Digital-Twin virtual model real-time construction via spatio-temporal cascade reconstruction for full-field plastic deformation monitoring in metal tube bending manufacturing

Digital Twin (DT) technology, which integrates multi-source information, is extensively applied for comprehensive monitoring, predicting, and optimizing manufacturing processes. The core of this technology is the Digital Twin Virtual Model (DTVM), which acts as a virtual mirror reflecting the real-world physical processes within a digital environment. In processes like tube bending, constructing a real-time DTVM capable of capturing full-field plastic deformation is essential for monitoring and analyzing plastic behavior. However, existing DTVMs often simplify spatial resolution and suffer from temporal delays, impeding the accurate real-time depiction of the complete state of the real physical processes. To address this issue, a real-time DTVM construction method based on spatio-temporal cascade reconstruction was proposed for full-field plastic deformation monitoring in metal tube bending. Initially, a joint-section driven predefined bending tube coordinate representation method was introduced to comprehensively capture the entire plastic deformation area in bending tubes. Subsequently, through a physics-derived model integrating limited real-time data and plastic forming theory, a low-fidelity model with complete but low accuracy was obtained. This model was subsequently refined into a high-fidelity model with both completeness and high accuracy using the proposed FPDR-Net. To eliminate temporal lags, the concept of compensation for time-delay through prediction was introduced. The newly developed TSCR-Net was applied to leverage past data to predict the present state, thereby achieving real-time synchronization mapping between the physical process and the DTVM. Finally, the proposed real-time reconstruction method for monitoring was validated through a case study on the bending of a 6061-T6 tube. The accuracy of full-field plastic deformation reconstruction was compared to traditional algorithms and finite element methods. The experimental results demonstrated that the proposed approach is highly efficient for real-time and full-field plastic deformation monitoring.

Analysis of flow and heat transfer in bend pipe with different smoothing

This research employs a numerical approach to comprehensively analyze fluid flow and forced convection heat transfer phenomena within a bent pipe. The finite difference method obtains numerical results, and simulations are conducted across a Reynolds number range of 100≤Re≤800, at constant Prandtl number (Pr=1). The study explores three inclination angles (ϕ=30°45°70°) and incorporates three smoothing phases of the bending angles. The results are presented through streamline and isotherm and local Nusselt numbers. Notably, vortices near the pipe bend positively correlate with Reynolds number and inclination angle, enhancing heat transfer. At the same time, an inverse relationship is observed between vortex length and bend smoothness. Furthermore, higher local Nusselt numbers are identified at elevated inclination angles, and Reynolds numbers are on the wall bend in the channel. Overall, this investigation underscores the significant influence of inclination angle on heat transfer characteristics, providing valuable insights for applications in thermal engineering and fluid dynamics.

A three-directional stress-strain model-based physics-embedded prediction framework for metal tube full-bent cross-sectional characteristics

A metal tube system is known as the industrial blood vessel, among which the bent section is the most vulnerable part. The cross-sectional defects (CSDs) of the bent tube cause the flow fluctuation of the fluid inside the tube. The existing defect characterization methods are roughly presented by describing CSDs in some specific cross-sections, which results in the lack of the tube full-bent section (FBS) characteristic information. To comprehensively describe and predict the tube FBS characteristics, an advanced physics-embedded CSDs prediction framework is proposed. This framework includes an FBS-neutral layer displacement angle (NLDA) prediction module and an FBS-CSDs prediction module, which uses the method that integrates the analytical model and BiLSTM-based deep learning (DL) models to predict the CSDs in the FBS of the tube. A novel analytical model of CSDs that considers both three-directional stresses and strains during tube bending is embedded in the FBS-CSDs prediction module. The analytical model provides the initial predicted values of CSDs through the NLDA sequence obtained from the FBS-NLDA module. The inaccurate CSDs are then treated as physical information to be fed into DL models for further correction and prediction. The prediction performance of this framework is validated through numerical simulations and experiments. The results prove that the framework can accurately predict the CSDs in the tube FBS. The integration of DL models with the analytical model not only overcomes the limitations of the analytical model, but also improves the prediction accuracy and convergence speed of DL models.

Numerical Simulation of Internal Flow Field in Optimization Model of Gas–Liquid Mixing Device

This article studies the influence of structural parameters of the optimization model for the gas–liquid mixing device of a fire truck (compressed air foam lift fire truck, model JP21/G2, made in China) on the liquid phase volume fraction, static pressure, velocity streamline, and the influence of smaller flow rates on the mixing effect. By using the computational fluid dynamics (CFD) software FLUENT 2021 R2, numerical simulations were conducted on the fluid domain model of the gas–liquid mixing device of the JP21/G2 fire truck. The changes in the mixing effect time dimension, liquid phase volume fraction, static pressure, and velocity streamline inside the gas–liquid mixing device were obtained. The optimal mixer structure combination in practical applications was inferred through orthogonal experiments, and the influence of flow rate on the optimal pipe diameter and shortest mixing distance was obtained through variable flow rate simulation experiments. The numerical simulation results show that the presence of bent pipes in the JP21/G2 real vehicle model hinders the gas–liquid mixing process. A straight pipe section of at least 8 m was added after the bent pipe to ensure the mixing effect. The optimal parameter combination for orthogonal experiments had an accurate value of 50°-50°-220 mm. Under the same pipe diameter, using a larger flow rate can achieve better mixing effects.