scholarly journals Stress and Deformation Analysis of Buried Gas Pipelines Subjected to Buoyancy in Liquefaction Zones

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2334 ◽  
Author(s):  
Mengying Xia ◽  
Hong Zhang
Keyword(s):  
Analytical Model ◽  
Safety Evaluation ◽  
Element Model ◽  
Deformation Analysis ◽  
Strength Analysis ◽  
Gas Pipelines ◽  
Long Distance ◽  
Axial Forces ◽  
And Performance ◽  
Buried Gas Pipeline

Buried pipelines are the main means of long distance transportation of natural gas. These pipelines are in high risk crossing liquefaction areas due to large deformations and stresses that may exist in pipe induced by the buoyancy load. In this study, a systematic analytical and numerical analysis were performed to investigate the mechanical behavior of a buried gas pipeline subjected to buoyancy in liquefaction areas. Soil constraints on pipe were considered accurately in the proposed models through soil spring assumptions. Effects of axial forces on pipe’s bending deformation were also considered via the governing equations for beam under bending and tension. Deformation compatibility condition was utilized to derive the axial forces in pipe. The accuracy of the proposed analytical model was validated by comparing its results with those derived by an established rigorous finite element model. In addition, parametric analysis was finally performed using the analytical model to study the influences of pipe diameter, pipe wall thickness, soil spring stiffness and width of liquefaction zone on pipe’s mechanical responses. This study can be referenced in the strength analysis and performance based safety evaluation of buried gas pipelines crossing liquefaction areas.

Design of a Flexible-Base Hinged Connector for Very Large Floating Structures

2018 ◽  
Author(s):  
Qijia Shi ◽  
Daolin Xu ◽  
Haicheng Zhang
Keyword(s):  
Dynamic Behavior ◽  
Element Model ◽  
Structure Design ◽  
Deformation Analysis ◽  
Strength Analysis ◽  
Floating Platform ◽  
Floating Structures ◽  
Design Loads ◽  
Flexible Base ◽  
Optimal Stiffness

Connector of multi-modular VLFS is a key component which determines the connection load and the dynamic behavior of the system. This paper presents a new design of the flexible-base hinged connector (FBHC) for VLFS in order to reduce the connection load. The connector consists of a hinged joint and two flexible bases. A finite element model of the connector is established for the deformation analysis to match up the requirement on the optimal stiffness combination of the connector [1]. Further the strength analysis is also carried out to check the safety of the structure design according to the maximum design loads. By applying the connector model to a three-modular floating platform, the dynamic behavior of the platform is analyzed. The results show that the responses of the modules are within the tolerable range and the connector meets the strength requirements.

Axial Force Regulation in MEMS Resonant Sensors

2009 ◽  
Author(s):  
Pezhman A. Hassanpour ◽  
Chris T. Wong ◽  
Patricia M. Nieva ◽  
Amir Khajepour
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Analytical Model ◽  
Axial Force ◽  
Thermal Stresses ◽  
Element Model ◽  
Fine Tuning ◽  
Resonant Sensors ◽  
Passive Mechanism ◽  
Axial Forces

In this paper, a passive mechanism is proposed for regulating the axial forces due to thermal stresses induced in MEMS resonant sensors. It is shown that by using this mechanism, one can control the axial force or thermal stresses to be compressive or tensile, or zero. An analytical model and a finite element model are developed for this study. It is shown that the analytical model is a powerful tool to predict the overall response and/or optimize the design, while the finite element model can be used for fine tuning and obtaining more accurate results.

Residual Strength Analysis of Oil Tubes with Corrosion Defect

2016 ◽  
Vol 850 ◽  
pp. 950-956
Author(s):  
Meng Ying Xia ◽  
Qing Quan Duan ◽  
Xiao Ben Liu ◽  
Hong Zhang
Keyword(s):  
Residual Strength ◽  
Safety Evaluation ◽  
Element Model ◽  
Oil Field ◽  
Strength Analysis ◽  
Oil Well ◽  
Corrosion Defect ◽  
Radial Depth ◽  
Safety Production ◽  
Tahe Oil Field

Corrosion defect in oil tubes is one main threat for the safety production of oil field. The corrosion defect in the tube will cause stress concentration and even lead to failure. The injection of CO2 widely used during the recent years in oil fields, making the corrosion problems more severe. In this study a finite element model for the residual strength analysis of oil tube with corrosion defect was established by the programing language APDL. Based on the actual data of one oil well in Tahe oil field in China, the sensitivities of the axial length, circumferential width, radial depth of the corrosion defect, the internal pressure and axial force on the residual strength of the tube was examined in detail. The proposed method can be referred in the safety evaluation for oil tubes with corrosion defect.

Investigation on the free vibration behavior of sandwich conical shells with reinforced cores

2021 ◽  
pp. 109963622110204
Author(s):  
Mehdi Zarei ◽  
Gholamhossien Rahimi ◽  
Davoud Shahgholian-Ghahfarokhi
Keyword(s):  
Free Vibration ◽  
Orientation Angle ◽  
Element Model ◽  
Filament Winding ◽  
Vertex Angle ◽  
Sandwich Shell ◽  
Cross Sectional ◽  
Conical Shells ◽  
Vibration Behavior ◽  
Axial Forces

The free vibration behavior of sandwich conical shells with reinforced cores is investigated in the present study using experimental, analytical, and numerical methods. A new effective smeared method is employed to superimpose the stiffness contribution of skins with those of the stiffener in order to achieve equivalent stiffness of the whole structure. The stiffeners are also considered as a beam to support shear forces and bending moments in addition to the axial forces. Using Donnell’s shell theory and Galerkin method, the natural frequencies of the sandwich shell are subsequently derived. To validate analytical results, experimental modal analysis (EMA) is further conducted on the conical sandwich shell. For this purpose, a method is designed for manufacturing specimens through the filament winding process. For more validation, a finite element model (FEM) is built. The results revealed that all the validations were in good agreement with each other. Based on these analyses, the influence of the cross-sectional area of the stiffeners, the semi-vertex angle of the cone, stiffener orientation angle, and the number of stiffeners are investigated as well. The results achieved are novel and can be thus employed as a benchmark for further studies.

scholarly journals Selecting sorting centres to avoid long distance transport of weaned beef calves

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
T. Morel-Journel ◽  
E. Vergu ◽  
J.-B. Mercier ◽  
N. Bareille ◽  
P. Ezanno
Keyword(s):  
Negative Impact ◽  
Historical Record ◽  
Management Tool ◽  
Long Distance ◽  
Beef Calves ◽  
Long Distance Transport ◽  
And Performance ◽  
Distance Transport ◽  
French Beef ◽  
General Concern

AbstractThe transport of weaned calves from cow–calf producers to fatteners is a general concern for the young bull industry due to its documented negative impact on the welfare, health and performance of the animals. These transfers are often managed by intermediaries who transport weaned calves to sorting centres, where they are grouped into batches before being sent to fattening units. In this study, we present an algorithm to limiting these transfer distances by appropriately selecting the sorting centre through which they must go. We tested the effectiveness of this algorithm on historical data from a French beef producer organization managing 136,892 transfers using 13 sorting centres. The results show a decrease in the transfer distances compared to the historical record, especially for the calves travelling over long distances (− 76 km, i.e. 18% on average for the 33% longest transfers). Moreover, the distribution of calves between the sorting centres proposed by the algorithm reveals differences in their efficiency in minimizing transfer distances. In addition to its usefulness as a management tool for the daily transport of cattle, this algorithm provides prospects for improving the management of the sorting centres themselves.

Zero Gravity Validation of Smart Aperture Antennas

1999 ◽  
Author(s):  
Hwan-Sik Yoon ◽  
Gregory Washington
Keyword(s):  
Spherical Shell ◽  
Analytical Model ◽  
Stress Function ◽  
Spherical Shape ◽  
Element Model ◽  
Shallow Spherical Shell ◽  
Zero Gravity ◽  
Governing Equations ◽  
Homogeneous Solutions ◽  
Calculated Stress

Abstract In this study, a smart aperture antenna of spherical shape is modeled and experimentally verified. The antenna is modeled as a shallow spherical shell with a small hole at the apex for mounting. Starting from five governing equations of the shallow spherical shell, two governing equations are derived in terms of a stress function and the axial deflection using Reissner’s approach. As actuators, four PZT strip actuators are attached along the meridians separated by 90 degrees respectively. The forces developed by the actuators are considered as distributed pressure loads on the shell surface instead of being applied as boundary conditions like previous studies. This new way of applying the actuation force necessitates solving for the particular solutions in addition to the homogeneous solutions for the governing equations. The amount of deflections is evaluated from the calculated stress function and the axial deflection. In addition to the analytical model, a finite element model is developed to verify the analytical model on the various surface positions of the reflector. Finally, an actual working model of the reflector is built and tested in a zero gravity environment, and the results of the theoretical model are verified by comparing them to the experimental data.

Flow Assurance in Deep-Water Gas Pipelines: Locating Hydrate Plugging Position in a Fast Way

2021 ◽  
Author(s):  
Jing Yu ◽  
Cheng Hui ◽  
Chao Wen Sun ◽  
Zhan Ling Zou ◽  
Bin Lu Zhuo ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Deep Water ◽  
Pipe Wall ◽  
Gas Pipeline ◽  
Flow Assurance ◽  
Gas Pipelines ◽  
Long Distance ◽  
Hydrate Layer ◽  
Hydrate Deposition ◽  
Water Gas

Abstract Hydrate-associated issues are of great significance to the oil and gas sector when advancing the development of offshore reservoir. Gas hydrate is easy to form under the condition featuring depressed temperature and elevated pressure within deep-water gas pipeline. Once hydrate deposition is formed within the pipelines, the energy transmission efficiency will be greatly reduced. An accurate prediction of hydrate-obstruction-development behavior will assist flow-assurance engineers to cultivate resource-conserving and environment-friendly strategies for managing hydrate. Based on the long-distance transportation characteristics of deep-water gas pipeline, a quantitative prediction method is expected to explain the hydrate-obstruction-formation behavior in deep-water gas pipeline throughout the production of deep-water gas well. Through a deep analysis of the features of hydrate shaping and precipitation at various locations inside the system, the advised method can quantitatively foresee the dangerous position and intensity of hydrate obstruction. The time from the start of production to the dramatic change of pressure drop brought about by the deposition of hydrate attached to the pipe wall is defined as the Hydrate Plugging Alarm Window (HPAW), which provides guidance for the subsequent hydrate treatment. Case study of deep-water gas pipeline constructed in the South China Sea is performed with the advised method. The simulation outcomes show that hydrates shape and deposit along pipe wall, constructing an endlessly and inconsistently developing hydrate layer, which restricts the pipe, raises the pressure drop, and ultimately leads to obstruction. At the area of 700m-3200m away from the pipeline inlet, the hydrate layer develops all the more swiftly, which points to the region of high risk of obstruction. As the gas-flow rate increases, the period needed for the system to shape hydrate obstruction becomes less. The narrower the internal diameter of the pipeline is, the more severe risk of hydrate obstruction will occur. The HPAW is 100 days under the case conditions. As the concentration of hydrate inhibitor rises, the region inside the system that tallies with the hydrate phase equilibrium conditions progressively reduces and the hydrate deposition rate slows down. The advised method will support operators to define the location of hydrate inhibitor injection within a shorter period in comparison to the conventional method. This work will deliver key instructions for locating the hydrate plugging position in a fast way in addition to solving the problem of hydrate flow assurance in deep-water gas pipelines at a reduced cost.

scholarly journals Body Flexibility Enhances Maneuverability in the World’s Largest Predator

2018 ◽  
Vol 59 (1) ◽  
pp. 48-60 ◽  
Author(s):  
P S Segre ◽  
D E Cade ◽  
J Calambokidis ◽  
F E Fish ◽  
A S Friedlaender ◽  
...  
Keyword(s):  
Open Ocean ◽  
The Body ◽  
Long Distance ◽  
Active Surfaces ◽  
Aquatic Locomotion ◽  
And Performance ◽  
And Control ◽  
Blue Whales ◽  
Control Surfaces ◽  
Complex Trajectories

Abstract Blue whales are often characterized as highly stable, open-ocean swimmers who sacrifice maneuverability for long-distance cruising performance. However, recent studies have revealed that blue whales actually exhibit surprisingly complex underwater behaviors, yet little is known about the performance and control of these maneuvers. Here, we use multi-sensor biologgers equipped with cameras to quantify the locomotor dynamics and the movement of the control surfaces used by foraging blue whales. Our results revealed that simple maneuvers (rolls, turns, and pitch changes) are performed using distinct combinations of control and power provided by the flippers, the flukes, and bending of the body, while complex trajectories are structured by combining sequences of simple maneuvers. Furthermore, blue whales improve their turning performance by using complex banked turns to take advantage of their substantial dorso-ventral flexibility. These results illustrate the important role body flexibility plays in enhancing control and performance of maneuvers, even in the largest of animals. The use of the body to supplement the performance of the hydrodynamically active surfaces may represent a new mechanism in the control of aquatic locomotion.

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