An Analytical/Numerical Procedure for Structural Analysis of Hybrid Riser Systems

2005 ◽  
Author(s):  
G. J. O. Rodrigues ◽  
Daniel C. T. Cardoso ◽  
Beatriz S. L. P. de Lima ◽  
Breno P. Jacob ◽  
Antonio C. Fernandes
Keyword(s):  
Finite Element ◽  
Dynamic Simulation ◽  
Production Systems ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Solution Procedure ◽  
Analysis Tool ◽  
Full Time ◽  
Transient Effects ◽  
Dimensional Solution

In deep and ultra-deep water petroleum exploitation activities, floating production systems such as semi submersible platforms and FPSO (Floating Production, Storage and Offloading) units have been commonly employed. However, the utilization of flexible risers in ultra-deep waters has been hindered by technical and economical reasons. On the other hand, first order motions from the floating unit due to environmental loads are not favorable to the use of Steel Catenary Risers (SCR) in a free-hanging configuration. This fact has motivated several studies on hybrid riser systems, including the system studied in this work, which is based on a sub-surface buoy with large dimensions, moored to the seabed by tethers. This system employs flexible lines connecting the floating unit to the buoy, in the region where dynamic effects are more relevant due to the floating unit motions, and also SCRs that extend from the buoy to the seabed, in the region where dynamic motions are not so significant. The objective of this work is to describe a solution procedure for the analysis of such a hybrid riser system. This procedure is based on an analytical formulation that is solved numerically. One of the main features of this procedure is the fact that it takes into account the effects of current loads acting on the lines. Current profiles can be considered, with direction and velocities varying with depth, therefore configuring a full three-dimensional solution. This procedure can be employed either as a preliminary static analysis tool, to be used in parametric studies in order to assess the feasibility of candidate configurations of hybrid riser systems, or else for the generation of finite-element meshes for a full time-domain nonlinear dynamic simulation. It is important to start the dynamic simulation from a statically balanced configuration, since the transient effects can be dramatically shortened and the total simulation time can be reduced. The results obtained from this procedure are compared with a discrete solution obtained using a nonlinear finite-element based solver. The strategy considered here is intended to be an approach that will speed up the tasks involved in the design of hybrid risers systems based on the subsurface buoy concept.

Mathematical Modelling and Field Measurements of Nitrogen Oxides in Metropolitan Areas

1992 ◽  
Vol 3 (2) ◽  
pp. 133-147
Author(s):  
M.M. Elkotb ◽  
O.M.F. Elbahar ◽  
T.A. Abdou Ahmed ◽  
T.W. Abou-Arab
Keyword(s):  
Mathematical Model ◽  
Wind Speed ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Field Measurements ◽  
Mass Conservation ◽  
Eddy Diffusivity ◽  
Solution Procedure ◽  
Pollutant Emissions ◽  
Motor Vehicles

A mathematical model for the prediction of pollutant emissions from motor vehicles is presented. The model is based on the numerical solution of the three-dimensional equation representing the mass conservation of dilute diffusing species. The variation of wind speed and eddy diffusivity with height is taken into consideration. The three-dimensional diffusion equation is solved numerically. The numerical procedure involves the discretization of the partial differential equation using the finite volume approach. The resulting set of discretization equation is solved iteratively using a fully implicit solution procedure. Furthermore, field measurements of the concentrations of nitrogen oxide in the downtown area of Cairo were conducted. For this purpose, a mobile air pollution laboratory fitted with gas analyzers, particulate matter sampler and equipment for the measurement of wind speed and direction has been used. This laboratory is also fitted with data recording and monitoring facility. The mathematical model is tested by comparing the computed pollutant concentrations with the experimental data obtained from the field measurements in the Cairo Metropolitan Area.

scholarly journals A Quasi-Three-Dimensional Finite Element Solution for Steady Compressible Flow Through Turbomachines

1982 ◽  
Author(s):  
A. S. Ücer ◽  
İ. Yeġen ◽  
T. Durmaz
Keyword(s):  
Finite Element ◽  
Solution Method ◽  
Three Dimensional ◽  
Iterative Solution ◽  
Field Variable ◽  
Dimensional Solution ◽  
Subsonic Flows ◽  
Dimensional Finite Element ◽  
Flow Through ◽  
Three Dimensional Finite Element

A quasi-three-dimensional solution method is presented for subsonic flows through turbomachines of arbitrary geometry. Principal equations are based on Wu’s formulation of flow on blade-to-blade and hub-to-shroud surfaces, modified such that the same hub-to-shroud principal equation is used for all types of stream surfaces. Blade-to-blade surfaces are assumed to be surfaces of revolution. A stream function is used as the field variable. The problem is solved by finite element method. An iterative solution is used to find the quasi-three-dimensional solution. Solutions at hub, tip and mid height blade-to-blade surfaces are used to construct a mean hub-to-shroud surface and vice versa, until convergence is obtained. Results indicate that the developed technique is satisfactory for predicting the flow through turbomachine blades.

A Finite Element Model for Umbilical Cable Crushing Analysis

2015 ◽  
Author(s):  
Caio C. P. Santos ◽  
Celso P. Pesce ◽  
Rafael Salles ◽  
Guilherme R. Franzini ◽  
Rafael L. Tanaka
Keyword(s):  
Finite Element ◽  
Production Systems ◽  
Three Dimensional ◽  
Element Model ◽  
Numerical Approach ◽  
Essential Elements ◽  
Joint Analysis ◽  
Dimensional Effects ◽  
Offshore Industry ◽  
Umbilical Cable

Umbilical cables are essential elements of offshore floating production systems. Due to their complexity, the offshore industry regularly counts on numerical tools to perform design assignments. One of these assignments is to evaluate strains and stresses states in all components due to distinct sets of external loads. The main purpose of this paper is to present a numerical model for prediction of the stress and strain fields in the umbilical cable components under crushing loads. Such loads, outcoming from the laying operation, comprise the caterpillar shoes load and the squeezing effects, associated not only to the tensile armours, but also to helical components under tension. The referred model comprises a joint analysis using a two-dimensional Finite Element Method (FEM) fed by an analytical model, which represent three-dimensional effects. A combined analytical-numerical approach is much easier to implement than a complete fully three-dimensional one and it is meant to obtain results efficiently, without the need of a large computational capacity. The paper presents and discuss modeling hypotheses and methodology, describing in which way three-dimensional effects and interactions among cable components were treated. Case studies with three umbilical cables are presented.

scholarly journals Numerical Simulation and Parametric Analysis of Fatigue Crack in UIC60 Rail Thermite Welded Joint

2021 ◽  
Vol 1206 (1) ◽  
pp. 012027
Author(s):  
Prakash Kumar Sen ◽  
Mahesh Bhiwapurkar ◽  
S P Harsha
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Damage Mechanics ◽  
Three Dimensional ◽  
Element Model ◽  
Scale Model ◽  
Dimensional Solution ◽  
Diagnostic Skills ◽  
Analysis Technique

Abstract The mechanism of rail-wheel contact is the most essential field of study in railway engineering since it requires extensive application expertise, diagnostic skills, and a trustworthy analysis technique. In this research the fatigue life of a UIC60 rail AT weld under vertical load and its parametric effect has been studied, and for that a three-dimensional elastic-plastic finite element model is created using ANSYS space-claim software, and then finite element method is employed to analyse the full-scale model of wheel-track and weld system with realistic three-dimensional solution. Model assembly components include axle, wheel, and thermite-welded rail. Simulation of contact between wheel and UIC60 rail weld with crack on weld at angles of 30 and 60 degrees with different coefficients of friction between the weld wheel contact and between crack surfaces was carried out under vertical loadings. In general, the Hertz contact theory assumptions are taken into consideration throughout the analysis, and the impacts on fatigue life are given by using damage mechanics method. The results of the wheel/weld fatigue crack analysis have been displayed to demonstrate the influence of different parameters on the fatigue life of cracks. The purpose of this study is to identify and safeguard the rail against failure, as well as to ensure the safety of passengers and to reduce the cost of maintaining the rail system.

Effect of Varying Diameter of Dental Implants During Placements in Compromised Bony Ridges at Different Insertion Torques: A Finite Element Study

2014 ◽  
Author(s):  
Imran Aziz ◽  
Waleed A. Khan ◽  
Faisal Moeen ◽  
Imran Akhtar ◽  
Wasim Tarar
Keyword(s):  
Finite Element ◽  
Dental Implants ◽  
Dental Implant ◽  
Three Dimensional ◽  
Solution Procedure ◽  
Insertion Torque ◽  
Modeling And Analysis ◽  
Stress And Deformation ◽  
Three Dimensional Finite Element ◽  
Implant Loading

The life of dental implant depends on various parameters such as insertion torque, implant diameter and cortical and cancellous bones thickness. The thickness of the cortical and cancellous bones varies from patient to patient and for each thickness, the corresponding studies are required to determine the favorable implant loading. In this study, stress analysis on various dental implant fixtures inserted in compromised bony ridges is performed using three dimensional finite element analyses. Initially, the modeling and analysis of previously analyzed structure is done to validate the solution procedure. After successful validation, three dimensional linear elastic analysis of bone implant bone assembly is performed. The implant material is treated as isotropic whereas the bone materials are taken as anisotropic materials. The parametric study finds the effect of insertion torque and variation of implant diameter on stress induced in the compromised bony ridge. Further, the implant bone assembly was analyzed using various cortical bone thicknesses. It has been observed that the increase in torque results in increased stress and deformation in the bone. With increasing bone thickness, the similar variation of torque produces less stress and deformation in dental implants. The study is helpful in prediction of favorable implant loading and implants diameters for compromised bony ridges. The study provides useful knowledge in improving the performance and life of dental implants.

On the Torsion of the Slit Circular Cylindrical Shell

1984 ◽  
Vol 51 (1) ◽  
pp. 206-207
Author(s):  
E. H. Mansfield
Keyword(s):  
Finite Element ◽  
Shell Theory ◽  
Present Note ◽  
Circular Cylindrical Shell ◽  
Three Dimensional ◽  
Body Movements ◽  
Dimensional Solution ◽  
First Case ◽  
Shell Analysis ◽  
Shell Finite Element

The complexity of shell analysis stems from the fact that loads are resisted, in general, by both membrane and flexural action. There is a need to develop a suitable shell finite element, but many of those proposed at the present time fail in the context of the “sensitive solutions” coupled with rigid body movements. These “sensitive solutions” refer to known solutions (within the framework of shell theory) of problem in which it is kinematically possible for the shell to deform with no straining of the midsurface. (Purely inextensional solutions were first considered by Lord Rayleigh [1].) In two cases, namely the torsion of a slit cylinder and the application of uniformly distributed moments Mθ and Mx = vMθ to a slit cylinder, the contribution of the membrane forces is identically zero. The second of these two cases is too trivial to be used for comparison with finite element solutions, but the first case exhibits many of the features that current finite elements have difficulty in reproducing. An exact solution within the context of shell theory is not necessarily, of course, an exact three-dimensional solution. However, the torsion of a slit cylinder has also been solved three-dimensionally (Love [2]) and the present Note focuses attention on the exact variation of shear stress through the wall of the shell and on how this compares with shell theory.

Application of Viscous Analyses to the Design of Jet Exhaust Powered Lift Installations

1980 ◽  
Vol 102 (3) ◽  
pp. 626-631 ◽  
Author(s):  
E. Tjonneland ◽  
S. F. Birch
Keyword(s):  
Numerical Methods ◽  
Strong Coupling ◽  
Recent Progress ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Turbulence Models ◽  
External Flow ◽  
Analysis Procedure ◽  
Analysis Tool

The application of available numerical methods to the design of powered lift installations is reviewed. For this application, where strong coupling exists between the jet exhaust and the external flow, a three-dimensional viscous analysis tool is needed. The task of selecting a suitable analysis procedure is first outlined, with particular emphasis on the need for careful coordination of the various elements of the task. Problems and progress in the development of turbulence models are then discussed, and some selected three-dimensional calculations are presented to illustrate recent progress. Finally, a numerical procedure, currently under development for a particular powered lift application, is briefly described.

On Solutions of Plane Strain Consolidation Problems by Finite Element Methods

1971 ◽  
Vol 8 (1) ◽  
pp. 109-118 ◽  
Author(s):  
C. T. Hwang ◽  
N. R. Morgenstern ◽  
D. W. Murray
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Closed Form ◽  
Plane Strain ◽  
Excellent Agreement ◽  
Finite Element Methods ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Algebraic Equations ◽  
Closed Form Solutions

The formulation is presented of the equations governing the solution of true three-dimensional consolidation problems by means of finite element methods. The numerical procedure for handling the resulting algebraic equations is described briefly and detailed results from the solution of several problems are given. Excellent agreement is found between the numerical analysis and existing closed form solutions.

scholarly journals Behaviour of a semi-infinite beam in a creeping medium

1992 ◽  
Vol 29 (5) ◽  
pp. 779-788 ◽  
Author(s):  
B. Rajani ◽  
N. Morgenstern
Keyword(s):  
Finite Element ◽  
Lower Bound ◽  
Structural Design ◽  
Three Dimensional ◽  
Approximate Solutions ◽  
Finite Element Analyses ◽  
Laterally Loaded Piles ◽  
Dimensional Solution ◽  
Infinite Beam ◽  
Laterally Loaded

The behaviour of a pipeline embedded in a creeping medium is examined. Approximate solutions for a beam in a creeping foundation are developed, and characteristic nondimensional load–displacement relationships are presented. A comparison of these approximate solutions provides upper and lower bound solutions that are consistent with finite element analyses. Furthermore, the simplified solutions can be readily adapted for analyzing the uplift behaviour of shallow pipelines. These solutions can also be used to analyze the creeping behaviour of laterally loaded piles. The results are presented in the form of nondimensional charts that permit hand calculations and rapid verification of the structural design of the pipelines and piles. An approximate three-dimensional solution that accounts for embedmentis proposed. Key words : creeping behaviour of pipelines, creeping foundation, laterally loaded pile.

Radial Truck Tire Inflation Analysis: Theory and Experiment

1981 ◽  
Vol 54 (4) ◽  
pp. 751-766 ◽  
Author(s):  
R. H. Kennedy ◽  
H. P. Patel ◽  
M. S. McMinn
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Element Model ◽  
Solution Procedure ◽  
Truck Tire ◽  
Truck Tires ◽  
Tube Type ◽  
The Finite Element Model

Abstract The finite element method is a useful tool in the design process to give deformations, strains and stresses in tires when they are loaded. To show this, a geometrically nonlinear, materially homogeneous, and generally orthotropic finite element model is described and used in the inflation analysis of radial truck tires. The element, a linear strain axisymmetric triangle, has three displacement degrees of freedom at each node in order to correctly model the three-dimensional states of strain and stress present in generally orthotropic structures. Two radial truck tires, a tube-type 10.00R20 and a tubeless 11R22.5, are analyzed both experimentally and analytically for inflation loading. Experimentally, cord forces are measured by cord force transducers, belt edge interply shear strain is measured by a pin rotation technique, sidewall growth is measured by a laser profilometer, and sidewall strains are measured with liquid metal strain gages. These values are compared with those predicted by the finite element model. The model works well for the tube-type 10.00R20 tire and above the mid-sidewall of the tubeless 11R22.5 tire. Further work needs to be done on the lower sidewall and bead area portions of the 11R22.5 tire model. The finite element model and solution procedure for the 11R22.5 radial truck tire is used for trend predictions. Several tire construction features, belt bias angle, belt end count, body ply end count, and bell skim stock modulus are varied, and their effect on inflation growth, strains and cord forces are predicted. The largest effect on inflation behavior was variation of the belt bias angle. The other features had minor effects. These predicted trends are important in giving the design engineer direction in creating new tire types or modifying current designs.

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