Drained Breakout Resistance of a Pipeline on a Mobile Seabed

2015 ◽  
Author(s):  
Joe G. Tom ◽  
Simon H. F. Leckie ◽  
David J. White ◽  
Scott Draper
Keyword(s):  
Sediment Transport ◽  
Parametric Study ◽  
Numerical Study ◽  
Strong Impact ◽  
Relative Importance ◽  
Subsea Pipelines

This paper describes a numerical study investigating the effect of sediment transport and associated changes in the local seabed profile on the drained breakout resistance of subsea pipelines. Limit analyses were conducted assessing the breakout response of a pipeline placed on a cohesionless Mohr-Coulomb material considering different seabed profiles around the pipeline. These profiles were determined from surveys of a pipeline on an erodible seabed. The parametric study shows the relative importance of various parameters describing the seabed profile geometry, including the local pipe embedment and the adjacent slope of the seabed. Significant changes in drained resistance occur due to changes in local pipeline embedment resulting from scour induced pipeline lowering and/or sedimentation. The seabed slope local to the pipeline also has a strong impact. The assumption of a flat seabed can lead to predicted seabed resistance that differs significantly from the actual value, accounting for a more natural seabed profile.

2D and 3D CFD Investigations of Seabed Shear Stresses Around Subsea Pipelines

2013 ◽  
Author(s):  
Wenwen Shen ◽  
Terry Griffiths ◽  
Mengmeng Xu ◽  
Jeremy Leggoe
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Interaction Model ◽  
Suspended Sediment Transport ◽  
Shear Stresses ◽  
Parametric Function ◽  
Ample Evidence ◽  
North West ◽  
Wide Range ◽  
Subsea Pipelines

For well over a decade it has been widely recognised that existing models and tools for subsea pipeline stability design fail to account for the fact that seabed soils tend to become mobile well before the onset of pipeline instability. Despite ample evidence obtained from both laboratory and field observations that sediment mobility has a key role to play in understanding pipeline/soil interaction, no models have been presented previously which account for the tripartite interaction between the fluid and the pipe, the fluid and the soil, and the pipe and the soil. There are numerous well developed and widely used theories available to model pipe-fluid and pipe-soil interactions. A challenge lies in the way to develop a satisfactory fluid-soil interaction algorithm that has the potential for broad implementation under both ambient and extreme sea conditions due to the complexity of flow in the vicinity of a seabed pipeline or cable. A widely used relationship by Shields [1] links the bedload and suspended sediment transport to the seabed shear stresses. This paper presents details of computational fluid dynamics (CFD) research which has been undertaken to investigate the variation of seabed shear stresses around subsea pipelines as a parametric function of pipeline spanning/embedment, trench configuration and wave/current properties using the commercial RANS-based software ANSYS Fluent. The modelling work has been undertaken for a wide range of seabed geometries, including cases in 3D to evaluate the effects of finite span length, span depth and flow attack angle on shear stresses. These seabed shear stresses have been analysed and used as the basis for predicting sediment transport within the Pipe-Soil-Fluid (PSF) Interaction Model [2] in determining the suspended sediment concentration and the advection velocity in the vicinity of pipelines. The model has significant potential to be of use to operators who struggle with conventional stabilisation techniques for the pipelines, such as those which cross Australia’s North West Shelf, where shallow water depths, highly variable calcareous soils and extreme metocean conditions driven by frequent tropical cyclones result in the requirement for expensive and logistically challenging secondary stabilisation measures.

A Parametric Numerical Study of Radiative Transfer in Thermotropic Materials

2013 ◽  
Author(s):  
Adam C. Gladen ◽  
Susan C. Mantell ◽  
Jane H. Davidson
Keyword(s):  
Particle Size ◽  
Radiative Transfer ◽  
Optical Thickness ◽  
Parametric Study ◽  
Volume Fraction ◽  
Numerical Study ◽  
Anisotropic Scattering ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Size Parameter

A thermotropic material is modeled as an absorbing, thin slab containing anisotropic scattering, monodisperse, spherical particles. Monte Carlo ray tracing is used to solve the governing equation of radiative transfer. Predicted results are validated by comparison to the measured normal-hemispherical reflectance and transmittance of samples with various volume fraction and relative index of refraction. A parametric study elucidates the effects of particle size parameter, scattering albedo, and optical thickness on the normal-hemispherical transmittance, reflectance, and absorptance. The results are interpreted for a thermotropic material used for overheat protection of a polymer solar absorber. For the preferred particle size parameter of 2, the optical thickness should be less than 0.3 to ensure high transmittance in the clear state. To significantly reduce the transmittance and increase the reflectance in the translucent state, the optical thickness should be greater than 2.5 and the scattering albedo should be greater than 0.995. For optical thickness greater than 5, the reflectance is asymptotic and any further reduction in transmittance is through increased absorptance. A case study is used to illustrate how the parametric study can be used to guide the design of thermotropic materials. Low molecular weighted polyethylene in poly(methyl methacrylate) is identified as a potential thermotropic material. For this material and a particle radius of 200 nm, it is determined that the volume fraction and thickness should equal 10% and 1 mm, respectively.

Inelastic seismic shear amplification due to higher mode effects in reinforced concrete coupled walls

2021 ◽  
pp. 875529302110533
Author(s):  
Gabriel Rivard ◽  
Steeve Ambroise ◽  
Patrick Paultre
Keyword(s):  
Reinforced Concrete ◽  
Parametric Study ◽  
Numerical Study ◽  
Plastic Hinge ◽  
Experimental Studies ◽  
Physical Parameters ◽  
Intensity Level ◽  
Shear Forces ◽  
Coupled Walls ◽  
Seismic Shear

Recent numerical and experimental studies on reinforced concrete shear walls and coupled walls have shown shear forces greater than expected when the walls are subjected to earthquakes at an intensity level that does not exceed the design values. This amplification of shear forces is attributable to the effects of higher modes after the walls develop a plastic hinge at the base. These effects have been recently recognized in North American design codes for cantilever walls and is currently neglected in the design of ductile coupled walls. As part of the research program described in this article, a parametric study was carried out on coupled wall systems to identify the geometric and physical parameters having the greatest influence on the seismic shear amplification. Using the results of this parametric study, an extensive numerical study was conducted on classes of ductile coupled walls subjected to seismic excitation representative of Western and Eastern Canada. This extensive study led to the establishment of shear amplification prediction equations for use in building codes.

Member distortional buckling behaviour of hybrid double-I-box beams

2018 ◽  
Vol 45 (8) ◽  
pp. 605-622 ◽  
Author(s):  
M.S. Deepak ◽  
V.M. Shanthi
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Parametric Study ◽  
Flexural Rigidity ◽  
Numerical Study ◽  
Plate Thickness ◽  
Distortional Buckling ◽  
Study Results ◽  
Box Beams ◽  
The Moment

This paper compiles the experimental and finite-element parametric study on member distortional buckling behaviour of new built-up metal hybrid double-I-box beams (HDIBBs). The cross-section of this built-up beam is unique and looks similar to the shape of a double-I-box fabricated using four channel sections. The flange plates were provided with an intermediate stiffener. In these built-up beams there is more material in the flange portions far away from the horizontal centroidal axis of their cross-section. Hence, there is an increase in the flexural rigidity that enhances the moment capacity of the beam, under major axis bending. The geometry consists of torsionally rigid closed-box web portion that provides high resistance to minor axis lateral-buckling. The varying parameters considered were the ratio of yield stresses of the flange to the web steel plates, the ratio of breadth to the depth of the section, and the flange plate thickness. In the experimental programme, all the HDIBB members failed due to kinds of distortional buckling which was identified by web buckling and flange twist along edges. The results revealed that when flange plate slenderness increases there is a drop in the moment resistance capacity of the beams. The numerical study was performed using ABAQUS software. In comparison, there was good agreement between experimental and numerical results. The validated finite element models were further extended to perform parametric studies on ideal HDIBB models. Both the experimental and parametric study results were compared with the predicted strengths using effective width method equations specified in the Euro code standards EN 3-1-3. It was found that the current Euro code design rules slightly over-estimate the distortional buckling resistance capacity of closed form built-up cold-formed steel members. A new design equation was formulated and recommended for estimating the reduction in distortional buckling moment resistance capacity for HDIBBs.

A Numerical Study of Ammonia-Water Absorption Into a Constrained Microscale Film

2008 ◽  
Author(s):  
Ruander Cardenas ◽  
Vinod Narayanan
Keyword(s):  
Weak Solution ◽  
Steady State ◽  
Parametric Study ◽  
Numerical Study ◽  
Porous Plate ◽  
Coolant Fluid ◽  
Geometrical Parameters ◽  
Ammonia Vapor ◽  
Ammonia Water ◽  
Vapor Distribution

A one-dimensional, steady state, semi-empirical model of an ammonia-water microscale bubble absorber is presented. The geometry consists of a microchannel through which a solution of ammonia-water flows. Ammonia vapor is injected through one of the walls of the channel. A counter flowing coolant solution removes the heat generated due to absorption from the opposite wall. The 1-D, steady state species and energy transport equations are solved to yield, along the length of the channel, concentration and temperature profiles of the solution stream and the temperature profile of the coolant fluid stream. Values for the overall heat transfer coefficient from experimental results are used in this model. A parametric study of fluid and geometrical parameters based on the model is presented. The varied fluidic parameters include the mass flow rates of the weak solution, coolant, and vapor, the inlet coolant temperature, and the weak solution concentration. Two variations of the vapor distribution that resulted from a geometrical variation of the porous plate are considered: (a) variation in length of the non-porous section, and (b) variation in the number of intermittent sections in which there was no injection of vapor. Trends of the parametric study were consistent with those of experiments. A salient result of the parametric study indicates that incomplete absorption occurs with an increase in weak solution flow rate due to the decrease in residence time within the microchannel for absorption. At a specific fixed flow condition, a single porous section followed by a non-porous section provides the optimal vapor distribution for absorption within the channel. The length of this non-porous section for optimal absorption within the channel is also determined using the model.

Dynamic response of a concrete dam impounding an ice-covered reservoir: Part II. Parametric and numerical study

2004 ◽  
Vol 31 (6) ◽  
pp. 965-976 ◽  
Author(s):  
Najib Bouaanani ◽  
Patrick Paultre ◽  
Jean Proulx
Keyword(s):  
Dynamic Response ◽  
Frequency Response ◽  
Parametric Study ◽  
Seismic Analysis ◽  
Numerical Study ◽  
Ice Cover ◽  
Concrete Dams ◽  
Response Curves ◽  
Concrete Dam ◽  
Structure Interaction

This paper presents a numerical and parametric study of the effect of an ice cover on the dynamic response of a concrete dam using the approach proposed in the companion paper in this issue. The method was programmed and implemented in a finite element code specialized for the seismic analysis of concrete dams. The 84-m-high Outardes 3 concrete gravity dam in northeastern Quebec was chosen as a model for this research. Some basic aspects of the numerical model are established in this paper and we show that the ice cover affects the dynamic response of the ice–dam–reservoir system. Main features of this influence are emphasized and discussed in a parametric study through the analysis of: (i) acceleration frequency response curves at the dam crest, (ii) hydrodynamic frequency response curves inside the reservoir, and (iii) the hydrodynamic pressure distribution on the upstream face of the dam. Key words: gravity dams, concrete dams, ice, reservoirs, mathematical models, ice–structure interaction, fluid–structure interaction, forced-vibration testing, finite elements modelling.

scholarly journals Relative Importance of Tide and River Discharge on Sediment Transport on Intertidal Flat

2010 ◽  
Vol 66 (1) ◽  
pp. 531-535 ◽  
Author(s):  
Fumihiko YAMADA ◽  
Yuuichiro SHIRAKAWA ◽  
Yoshitaka FUNAKOSHI ◽  
Kazuhiko TAGAWA ◽  
Takaomi HOKAMURA ◽  
...  
Keyword(s):  
Sediment Transport ◽  
River Discharge ◽  
Intertidal Flat ◽  
Relative Importance
Sign in / Sign up

Export Citation Format

Share Document