Experimental Analysis of Surface Geometry, External Damping and Waves on Semisubmersible Vortex Induced Motions

2012 ◽  
Author(s):  
Bruce Martin ◽  
Oriol Rijken
Keyword(s):  
Fatigue Damage ◽  
Experimental Work ◽  
Experimental Analysis ◽  
Surface Characteristics ◽  
Field Conditions ◽  
Surface Geometry ◽  
Dominant Response ◽  
Steel Catenary Riser ◽  
Motion Trajectories ◽  
Response Direction

Semisubmersible Vortex Induced Motions have been studied extensively at model scales, and observed under field conditions. VIM response is of particular concern in evaluations of Steel Catenary Riser (SCR) fatigue damage. Historically, most of this experimental work was done with bare models, without much effort to represent actual hull surface characteristics. In this paper, the effect of these appurtenances, tow direction and wave action is investigated. There is also an examination of vortex induced yaw response. VIM response is assessed using motion trajectories, dominant response direction, and amplitudes and periods of response. Variations in these quantities are also investigated.

Performance Impacts of Tailored Surface Geometry in Li-Ion Battery Cathodes

2013 ◽  
Author(s):  
George J. Nelson
Keyword(s):  
Surface Area ◽  
Solid Phase ◽  
Particle Surface ◽  
Surface Characteristics ◽  
Analytical Models ◽  
Li Ion Battery ◽  
Fractal Structures ◽  
Surface Geometry ◽  
Trade Offs ◽  
Li Ion

Analytical models developed to investigate charge transfer in Li-ion battery cathodes reveal distinct transport regimes where performance may be limited by either microstructural surface characteristics or solid phase geometry. For several cathode materials, particularly those employing conductive additives, surface characteristics are expected to drive these performance limitations. For such electrodes gains in performance may be achieved by modifying surface geometry to increase surface area. However, added surface area may present a diminishing return if complex structures restrict access to electrochemically active interfaces. A series of parametric studies has been performed to better ascertain the merits of complex, tailored surfaces in Li-ion battery cathodes. The interaction between lithium transport and surface geometry is explored using a finite element model in which complex surfaces are simulated with fractal structures. Analysis of transport in these controlled structures permits assessment of scaling behavior related to surface complexity and provides insight into trade-offs in tailoring particle surface geometry.

Sensitivity Study of Critical Parameters Influencing the Uncertainty of Fatigue Damage in Steel Catenary Risers

2010 ◽  
Author(s):  
Feng Zi Li ◽  
Ying Min Low
Keyword(s):  
Fatigue Damage ◽  
Cost Effective ◽  
Sensitivity Study ◽  
Structural Safety ◽  
Critical Parameters ◽  
Design Parameters ◽  
Steel Catenary Riser ◽  
Bending Stresses ◽  
Steel Catenary Risers ◽  
Touchdown Point

The most challenging aspect of a deepwater development is the riser system, and a cost-effective choice is the Steel Catenary Riser (SCR). Fatigue is often a governing design consideration, and it is usually most critical at the touchdown point (TDP) where static and dynamic bending stresses are highest. Unfortunately, it is also at this region that uncertainty is the maximum. The increased uncertainty casts doubt on the applicability of generic safety factors recommended by design codes, and the most consistent way of ensuring the structural safety of the SCR is to employ a reliability-based approach, which has so far not received attention in SCR design. As the number of basic random variables affects the complexity of a reliability analysis, these variables should be selected with caution. To this end, the aim of this paper is to draw up a comprehensive list of design parameters that may contribute meaningfully to the uncertainty of the fatigue damage. From this list, several parameters are selected for sensitivity studies using the commercial package Orcaflex. It is found that variations in seabed parameters such as soil stiffness, soil suction and seabed trench can have a pronounced influence on the uncertainty of the fatigue damage at the touchdown point.

Experimental analysis of contact fatigue damage using fractal methodologies

Wear ◽  
2020 ◽  
Vol 450-451 ◽  
pp. 203262
Author(s):  
Deepak K. Prajapati ◽  
Mayank Tiwari
Keyword(s):  
Fatigue Damage ◽  
Experimental Analysis ◽  
Contact Fatigue

Über den zeitlichen Verlauf des Stromes einer Townsend-Entladung im ebenen Felde

1961 ◽  
Vol 16 (6) ◽  
pp. 539-547 ◽  
Author(s):  
R. Kluckow
Keyword(s):  
Transit Time ◽  
Light Pulse ◽  
Experimental Work ◽  
Uv Light ◽  
Gas Discharge ◽  
Field Conditions ◽  
Single Electron ◽  
Transient Growth ◽  
Discharge System

The transient growth of currents in a TOWNSEND gas discharge system under uniform dc field conditions is calculated by means of the theory given by AUER 1. Three cases are examined in detail: 1) The discharge is initiated by a short UV light pulse releasing a great number of electrons from the cathode. 2) The discharge is started by a single electron. 3) The discharge develops under constant external illumination producing a great number of electrons within a period of an electron transit time.Earlier experimental work is discussed on the basis of the calculated relations.

Time Domain Computation of Riser VIV From Vessel Motions

2006 ◽  
Author(s):  
Yongming Cheng ◽  
Kostas F. Lambrakos
Keyword(s):  
Velocity Profile ◽  
Fatigue Damage ◽  
Time Domain ◽  
Relative Velocity ◽  
Structural Characteristics ◽  
Time Domain Analysis ◽  
Computer Time ◽  
Steel Catenary Riser ◽  
Vessel Motion ◽  
Time Invariant

Intermittent riser VIV behavior caused by vessel motions can affect both riser strength and fatigue life. There are frequency domain codes available that are used routinely to calculate riser fatigue damage from VIV due to currents. These codes are often adapted to calculations of the vessel motion VIV and fatigue damage. The adaptations reduce the intermittent VIV to steady state VIV by assuming an appropriate time invariant velocity profile over the length of the riser. However, since vessel motions cause a relative velocity profile over the riser that varies with time, and the VIV response is intermittent, a time domain VIV code is best suited for such an analysis. The paper demonstrates the use of Technip’s time domain riser VIV code ABAVIV to calculate steel catenary riser VIV response and fatigue damage due to vessel motions. Since time domain analysis is computer time intensive, the paper also outlines an efficient methodology to perform these calculations. The analysis example in the paper is based on surge, pitch, and heave motions which are the most important vessel motions for the riser fatigue damage near the touch down region. The ABAVIV code accounts for the nonlinear structural characteristics of the SCR, and the unsteadiness of the VIV phenomenon for the present application.

scholarly journals Comfort properties of nano-filament polyester fabrics: sensory evaluation

2018 ◽  
Vol 69 (01) ◽  
pp. 3-10
Author(s):  
AZEEM MUSADDAQ ◽  
BOUGHATTAS AMAL ◽  
SIDDIQUE HAFIZ FAISAL ◽  
ANTONIN HAVELKA ◽  
SAJID HUSSAIN
Keyword(s):  
Sensory Evaluation ◽  
Mechanical Characteristic ◽  
Experimental Work ◽  
Evaluation System ◽  
Surface Characteristics ◽  
Polyester Fabric ◽  
Filament Yarn ◽  
Polyester Fabrics

In this article, an experimental work is presented to evaluate the sensorial properties of polyester fabric constructed by nano-filament yarn. For this purpose Nano Filament polyester fabric was fabricated and compared with the spun polyester/cotton (PC) and polyester/viscose (PV) blended fabric by using Kawabata evaluation system (KES-system) to assess the handle of the fabric based on mechanical characteristic. The results revealed that the fabric made from PC and PV blended fabric were stiffer than nano-filament polyester fabric. The higher hand value (THV) resulted in lower stiffness (Koshi), and higher smoothness (Numeri) and fullness (Fukurami).Hand values of PV blended fabric were close to nano-filament polyester fabric rather than PC fabric. The overall results of tensile, shearing, bending, compression and surface characteristics of nano-filament polyester fabric were found best as compared to PC and PV blended fabric.

Simplifying Methods for Fatigue Analysis of Risers

2019 ◽  
Author(s):  
Luiz O. C. M. Pereira ◽  
Paulo M. Videiro ◽  
Luís V. S. Sagrilo
Keyword(s):  
Fatigue Damage ◽  
Computing Time ◽  
Fatigue Analysis ◽  
State Matrix ◽  
Sea State ◽  
Mooring Lines ◽  
Steel Catenary Riser ◽  
Advantages And Disadvantages ◽  
Surface Method ◽  
Early Design Stages

Abstract This work presents methods for reducing computational costs to estimate fatigue damage in riser structures by simplifying the sea state matrix to be solved in time domain by finite element analyses. Two different methods are proposed: The Equivalent Damage Method (EDM), which is a lump block method with an innovative formulation using vessel linearized response to determine significant sea states; and the Response Surface Method (RSM), which uses results from a few sea states to estimate results for other intermediary scenarios required for the fatigue analysis. Basic assumptions and guidance on how to apply the proposed methods are explained through the text. The methods are used to solve an example of a Steel Catenary Riser (SCR) connected to a Semi-Submersible vessel, resulting in a reduction of almost 80% of the required computing time. Results show accurate values for damage estimates at the top of the riser, and limitations at the touch down zone. Advantages and disadvantages of each method are discussed in detail, demonstrating that they can be used with discretion at early design stages to estimate fatigue damage of risers, umbilicals and mooring lines in general.

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