Influence of Wave-Induced Uplift Forces on Upheaval Buckling of Pipelines Buried in Sandy Seabeds

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
D. Suresh Kumar ◽  
D. Achani ◽  
M. R. Sunny ◽  
T. Sahoo
Keyword(s):  
Gravity Waves ◽  
Shallow Waters ◽  
Burial Depth ◽  
Theoretical Studies ◽  
Wave Loads ◽  
Upheaval Buckling ◽  
Consolidation Model ◽  
Wave Induced ◽  
Uplift Forces ◽  
Experimental And Theoretical Studies

This study focuses on the buckling of pipelines in shallow waters subjected to surface gravity waves. The wave-induced uplift forces on pipelines buried in sandy seabeds are investigated using Biot's consolidation model. Empathetic imperfection model proposed by Taylor and Tran (1994, “Experimental and Theoretical Studies in Subsea Pipeline Buckling," Mar. Struct., 9(2), pp. 211–257.) is used for the study. Thereafter, buckling analyses are performed on the pipeline with the combined temperature and the wave-induced loads. The differences in the critical buckling temperatures for the pipe with consideration of wave loads are analyzed within a range of sea states. The influence of wave loads is found significant for low burial depth ratios.

Effect of Seabed Imperfection on the Buckling of Buried Pipelines Subjected to Wave-Induced Loads

2019 ◽  
Author(s):  
D. Suresh Kumar ◽  
M. R. Sunny ◽  
T. Sahoo
Keyword(s):  
High Pressures ◽  
Wave Forces ◽  
Wave Loads ◽  
Buried Pipelines ◽  
Soil Medium ◽  
Finite Element Software ◽  
Pore Pressures ◽  
Buckling Behavior ◽  
Wave Induced ◽  
Uplift Forces

Abstract Subsea pipelines operating under high pressures and temperatures are typically buried to protect from the environmental impacts and to prevent the instigation of global buckling. As the seabed profile is generally uneven, certain initial imperfections generally exist along the pipeline. As the pipe traverses in shallow waters, the seabed can be subjected to hydrodynamic loads caused by surface gravity waves. The hydrodynamic pressure, which typically depends on the wave height and water depth, leads to the development of pore pressures within the soil medium. This gradient of the pore pressures can cause significant uplift forces on the pipe, which may initiate the buckling in the vicinity of the imperfection. This study focuses on understanding the influence of these wave induced uplift forces on the buckling of the initial imperfect pipelines. Four typical imperfection profiles are considered in the study. The influence of imperfection shape on the buckling behavior is compared for surface laid and buried pipelines. Thereafter buckling behavior of the considered imperfect pipelines is studied with and without consideration of wave loads for a range of wave particulars and burial depths. The wave forces on the pipeline are estimated by solving Biot’s consolidation equations using finite element software COMSOL and the buckling studies are carried out using ABAQUS.

The Stabilizing Effect of Pre-Equilibria: A Trifluoromethyl Complex as CF2 Reservoir in Catalytic Olefin Difluorocarbenation

2020 ◽  
Author(s):  
Thomas Louis-Goff ◽  
Huu Vinh Trinh ◽  
Eileen Chen ◽  
Arnold L. Rheingold ◽  
Christian Ehm ◽  
...  
Keyword(s):  
High Selectivity ◽  
Side Reactions ◽  
Theoretical Studies ◽  
Attractive Feature ◽  
Catalyst Recovery ◽  
Wide Range ◽  
Stabilizing Effect ◽  
Experimental And Theoretical Studies

A new, efficient, catalytic difluorocarbenation of olefins to give 1,1-difluorocyclopropanes is presented. The catalyst, an organobismuth complex, uses TMSCF<sub>3</sub> as a stoichiometric difluorocarbene source. We demonstrate both the viability and robustness of this reaction over a wide range of alkenes and alkynes, including electron-poor alkenes, to generate the corresponding 1,1-difluorocyclopropanes and 1,1-difluorocyclopropenes. Ease of catalyst recovery from the reaction mixture is another attractive feature of this method. In depth experimental and theoretical studies showed that the key difluorocarbene-generating step proceeds through a bismuth non-redox synchronous mechanism generating a highly reactive free CF<sub>2</sub> in an endergonic pre-equilibrium. It is the reversibility when generating the difluorocarbene that accounts for the high selectivity, while minimizing CF<sub>2</sub>-recombination side-reactions.

Strong coupling: resonant effects

2017 ◽  
Author(s):  
Alexey V. Kavokin ◽  
Jeremy J. Baumberg ◽  
Guillaume Malpuech ◽  
Fabrice P. Laussy
Keyword(s):  
Strong Coupling ◽  
Experimental Studies ◽  
Strong Coupling Regime ◽  
Theoretical Studies ◽  
Stimulated Scattering ◽  
Quantum Theories ◽  
Pump Probe ◽  
Exciton Polaritons ◽  
Linear Optical Properties ◽  
Experimental And Theoretical Studies

This chapter presents experimental studies performed on planar semiconductor microcavities in the strong-coupling regime. The first section reviews linear experiments performed in the 1990s that evidence the linear optical properties of cavity exciton-polaritons. The chapter is then focused on experimental and theoretical studies of resonantly excited microcavity emission. We mainly describe experimental configuations in which stimulated scattering was observed due to formation of a dynamical condensate of polaritons. Pump-probe and cw experiments are described in addition. Dressing of the polariton dispersion and bistability of the polariton system due to inter-condensate interactions are discussed. The semiclassical and the quantum theories of these effects are presented and their results analysed. The potential for realization of devices is also discussed.

Homo- and heterobimetallic trihydride complexes stabilized by the tripodal phosphine ligand MeC(CH2PPh2)3: experimental and theoretical studies

1989 ◽  
Vol 28 (13) ◽  
pp. 2552-2560 ◽  
Author(s):  
Claudio Bianchini ◽  
Franco Laschi ◽  
Dante Masi ◽  
Carlo Mealli ◽  
Andrea Meli ◽  
...  
Keyword(s):  
Phosphine Ligand ◽  
Theoretical Studies ◽  
Experimental And Theoretical Studies
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