scholarly journals Hydrodynamic Behaviour of Floating Polygonal Platforms under Wave Action

2021 ◽  
Vol 9 (9) ◽  
pp. 923
Author(s):  
Jeong Cheol Park ◽  
Chien Ming Wang
Keyword(s):  
Wave Attenuation ◽  
Wave Action ◽  
Wave Direction ◽  
Hydrodynamic Behaviour ◽  
Radial Perturbation ◽  
Parametric Studies ◽  
Exciting Forces ◽  
The Cost ◽  
Marine Vessels ◽  
Analytical Approaches

The hydrodynamic behaviour of floating regular polygonal platforms under wave action was studied by conducting parametric studies. Considering triangular, square, hexagonal, and circular platforms of similar size and draft, the results show that their added mass, radiation damping, and RAOs are similar. However, the wave exciting forces are slightly different, particularly the horizontal forces. The polygonal platforms oriented with one of its corners in line with the prevailing wave direction can lead to a reduction in the horizontal force on the platform, a feature that helps in reducing the cost of a mooring system. Moreover, such oriented platforms are able to disperse the waves better in multiple directions and hence will not pose problems for ships or marine vessels passing by the platform on the weather side. Thus, the orientation of a polygonal platform is an important design consideration. From the comparison study among different polygonal platforms, their wave attenuation performances are slightly similar. The hydrodynamic analyses performed herein for the parametric studies were sped up considerably by using a significantly lesser number of Fourier coefficient sets for the series functions that define the velocity potentials when compared to those used by previous researchers in their analytical approaches. The adoption of the radius function defined by cosine-type radial perturbation does not only generate the geometric boundaries of polygonal platforms, but it also simplifies the formulation and quickens the computations.

The Concept of the Optimum Alignment of Discharge Pipelines Due to the Minimization of the Wave Forces

1992 ◽  
Vol 25 (9) ◽  
pp. 211-216
Author(s):  
A. Akyarli ◽  
Y. Arisoy
Keyword(s):  
Wave Height ◽  
Wave Force ◽  
Wave Forces ◽  
Wave Direction ◽  
Incoming Wave ◽  
Pipeline Route ◽  
Optimum Alignment ◽  
The Cost ◽  
Resultant Wave

As the wave forces are the function of the wave height, period and the angle between the incoming wave direction and the axis of the discharge pipeline, the resultant wave force is directly related to the alignment of the pipeline. In this paper, a method is explained to determine an optimum pipeline route for which the resultant wave force becomes minimum and hence, the cost of the constructive measures may decrease. Also, the application of this method is submitted through a case study.

Predicted Ice Accretion on Horizontal Surfaces of Marine Vessels and Offshore Structures in Arctic Regions

2016 ◽  
Author(s):  
Alireza Dehghani-Sanij ◽  
Yuri S. Muzychka ◽  
Greg F. Naterer
Keyword(s):  
Water Film ◽  
Theoretical Method ◽  
Offshore Structures ◽  
Sea Spray ◽  
Ice Accretion ◽  
Wave Direction ◽  
Arctic Regions ◽  
Air Temperatures ◽  
The Stability ◽  
Marine Vessels

Sea spray icing is one of the most significant problems for the operation of marine vessels and offshore structures in Arctic regions. This phenomenon affects the stability of marine vessels and offshore structures, and also the safety of human activities onboard. In this paper, a new predictive icing model for large horizontal surfaces of a marine vessel is developed. To obtain the total flux of sea spray during the icing process, both wind spray and wave spray are considered. By applying heat, mass and salt concentration balances, the freezing fraction, temperature distribution, ice layer and water film thicknesses are determined. Moreover, the effects of different parameters on the freezing fractions at various air temperatures are investigated. The results indicate that air temperature, wind velocity, vessel speed, spray water salinity, height from the water surface, and angle between the vessel heading and wind/wave direction are major parameters in the growth rate of the ice. This theoretical method provides a reasonably accurate and simple way for predicting the sea spray icing phenomena on marine vessels and offshore structures.

A Novel Activated Carbon Enabled Steam Generation System Under Simulated Solar Light

2018 ◽  
Author(s):  
Ashreet Mishra ◽  
A. G. Agwu Nnanna
Keyword(s):  
Activated Carbon ◽  
Metallic Nanoparticles ◽  
Solar Light ◽  
Bulk Temperature ◽  
Steam Generation ◽  
Simulated Solar Light ◽  
Parametric Studies ◽  
Rate Of Evaporation ◽  
The Cost ◽  
First Time

A number of studies on CNT, Au and Ag solar enabled steam generation with potential application in water purification, distillation and sterilization of medical equipment. The key challenge with these nanoparticles is cost of production hence limiting its wide application for clean water production. This work for the first time, reports on activated carbon enabled steam generation hence addressing the cost limitations of metallic nanoparticles. Activated carbon has high solar absorptivity at various wavelengths of visible light under low concentration. Experiments were carried out using activated carbon and CNT nanofluids and polyurethane membrane with immobilized activated carbon and CNT. A simulated solar light of 1 KW ∼1 Sun was used. The rate of evaporation, temporal and spatial evolution of bulk temperature in the water were monitored automatically and recorded for further data reductions. Parametric studies of the effect of nanoparticle concentration, water quality and salinity were performed. Experimental evidence showed that activated carbon has potential. We reported for the first time that optimal activated carbon concentration for maximum steam generation is 60 % vol. We also obtained a 160 % increase in steam production rate at 60 % concentration of activated carbon when compared with D.I water.

The Friction Between Car Tires and Decks Under Ship Motions

2006 ◽  
Vol 43 (01) ◽  
pp. 27-39
Author(s):  
Junbo Jia ◽  
Anders Ulfvarson
Keyword(s):  
Friction Coefficient ◽  
Ship Motions ◽  
Pitch Period ◽  
Vertical Location ◽  
Safety Consideration ◽  
Parametric Studies ◽  
The Cost ◽  
Time Of Operation

For roll-on/roll-off (RO/RO) ships, when transporting more cars within the same deck area on board, it is necessary to adjust or take away the current lashing system. Furthermore, this operation may also decrease the cost and time of operation as well as cargo damages due to lashing. This requirement, combined with the safety consideration on cargo shifting, may lead to concepts of lashing-free deck design. One of the lashing-free concepts suggests that in some conditions cars can be secured without using lashings, mainly depending on the friction between the tire and the deck without lashings. By doing a series of parametric studies of vehicle securing without lashings under roll and pitch motions, it was found that the value of the maximum required friction coefficient between the tires and the deck is highly relevant to the roll and pitch amplitude, pitch period, orientation of vehicles on decks, and the vertical location of vehicles from the baseline of the vessel.

Eigenvalue Solution of Thermoelastic Damping in Beam Resonators Using a Finite Element Analysis

2007 ◽  
Vol 129 (4) ◽  
pp. 478-483 ◽  
Author(s):  
Yun-Bo Yi ◽  
Mohammad A. Matin
Keyword(s):  
Finite Element ◽  
Numerical Solutions ◽  
Finite Element Formulation ◽  
Element Formulation ◽  
Thermoelastic Damping ◽  
Element Analysis ◽  
Beam Resonator ◽  
Various Boundary Conditions ◽  
Parametric Studies ◽  
Analytical Approaches

A finite element formulation is developed for solving the problem related to thermoelastic damping in beam resonator systems. The perturbation analysis on the governing equations of heat conduction, thermoleasticity, and dynamic motion leads to a linear eigenvalue equation for the exponential growth rate of temperature, displacement, and velocity. The numerical solutions for a simply supported beam have been obtained and shown in agreement with the analytical solutions found in the literature. Parametric studies on a variety of geometrical and material properties demonstrate their effects on the frequency and the quality factor of resonance. The finite element formulation presented in this work has advantages over the existing analytical approaches in that the method can be easily extended to general geometries without extensive computations associated with the numerical iterations and the analytical expressions of the solution under various boundary conditions.

scholarly journals DETECTING AND ANALYZING CORROSION SPOTS ON THE HULL OF LARGE MARINE VESSELS USING COLORED 3D LIDAR POINT CLOUDS

2016 ◽  
Vol III-3 ◽  
pp. 153-160 ◽  
Author(s):  
A. K. Aijazi ◽  
L. Malaterre ◽  
M. L. Tazir ◽  
L. Trassoudaine ◽  
P. Checchin
Keyword(s):  
Surface Defects ◽  
Real Data ◽  
Point Clouds ◽  
Color Component ◽  
Ship Hulls ◽  
Adaptive Thresholds ◽  
Different Shapes ◽  
The Cost ◽  
Marine Vessels ◽  
3D Lidar

This work presents a new method that automatically detects and analyzes surface defects such as corrosion spots of different shapes and sizes, on large ship hulls. In the proposed method several scans from different positions and viewing angles around the ship are registered together to form a complete 3D point cloud. The <i>R</i>, <i>G</i>, <i>B</i> values associated with each scan, obtained with the help of an integrated camera are converted into HSV space to separate out the illumination invariant color component from the intensity. Using this color component, different surface defects such as corrosion spots of different shapes and sizes are automatically detected, within a selected zone, using two different methods depending upon the level of corrosion/defects. The first method relies on a histogram based distribution whereas the second on adaptive thresholds. The detected corrosion spots are then analyzed and quantified to help better plan and estimate the cost of repair and maintenance. Results are evaluated on real data using different standard evaluation metrics to demonstrate the efficacy as well as the technical strength of the proposed method.

Study of changes in the coefficient of hydraulic friction of materials of pressure pipes at different temperatures

2021 ◽  
pp. 54-59
Author(s):  
В.А. Орлов ◽  
С.П. Зоткин
Keyword(s):  
Calculated Data ◽  
Hydraulic Testing ◽  
Energy Costs ◽  
Temperature Conditions ◽  
Alternative Materials ◽  
Transportation Process ◽  
Different Temperatures ◽  
Hydraulic Friction ◽  
The Cost ◽  
Analytical Approaches

Снижение затрат электроэнергии на механическую транспортировку воды по напорным трубопроводам за счет уменьшения гидравлического сопротивления внутренних стенок труб носит актуальный характер. Это обстоятельство предопределяет необходимость проведения соответствующих гидравлических испытаний альтернативных материалов, которые могут быть использованы при проектировании и строительстве трубопроводных систем. Целью исследований является выявление характера изменения величины гидравлического трения в зависимости от температурных условий транспортируемой воды и окружающей среды в определенных диапазонах с последующей возможностью управления процессом транспортировки при минимуме затрат на электроэнергию. Достижение поставленных целей осуществляется путем опытного и расчетно-аналитического подходов к определению динамики изменения гидравлических показателей трубопроводов из различных материалов. Представлен комплексный анализ экспериментальных и расчетных данных, полученных с помощью запатентованных автоматизированных комплексов, по определению коэффициентов гидравлического трения для полиэтиленовой трубы и трубы из непластифицированного поливинилхлорида и динамики изменения этих коэффициентов в зависимости от температуры транспортируемых вод и температурных условий прокладки трубопроводов. Reducing the cost of electricity for the mechanical transportation of water through pressure pipelines by reducing the hydraulic resistance of the inner walls of the pipes is of current importance. This circumstance predetermines the need for appropriate hydraulic testing of alternative materials that can be used in the design and construction of pipeline systems. The aim of the study is to identify the nature of the change in the value of hydraulic friction depending on the temperature conditions of the transported water and the environment in certain ranges, with the subsequent possible control of the transportation process with a minimum of energy costs. The set goals are achieved by experimental computational and analytical approaches to determining the dynamics of changes in the hydraulic parameters of pipelines made of various materials. A comprehensive analysis of the experimental and calculated data obtained using patented automated systems for determining the coefficients of hydraulic friction for a polyethylene pipe and a pipe made of unplasticized polyvinylchloride, and the dynamics of changes in these coefficients depending on the temperature of the transported water and the temperature conditions of pipeline laying is presented.

New Sources and Methods In the Study of the Nineteenth Century Parliament

1972 ◽  
Vol 4 (2) ◽  
pp. 67-81 ◽  
Author(s):  
Thomas William Heyck
Keyword(s):  
Nineteenth Century ◽  
Electoral System ◽  
House Of Commons ◽  
Political Structure ◽  
Structural Investigations ◽  
Electoral Reforms ◽  
History Of ◽  
Parliamentary History ◽  
The Cost ◽  
Analytical Approaches

The study of the nineteenth century British Parliament cannot be limited to the institution itself, nor to the constitutional relations of its par ts. The great electoral reforms of the century increased the importance of the electorate in political decision-making. Coupled with these changes, the vast transformations of economy and society altered the very functions of Parliament. Thus nineteenth century parliamentary history requires an understanding of the whole political system, as well as the events within the House. Many of the recent works bearing on the history of Parliament reflect these facts. While good narrative history of parliamentary events continues to be needed and produced, the most innovative recent work raises different kinds of problems entirely and is not limited to affairs at Westminster. The newer types of work can be viewed as coming in two waves: first, a detailed analysis of political structure, utilizing traditional kinds of sources; and second, a proliferation of analytical approaches, using new sources and methods. Both waves are basically analytical, but they differ in questions asked and in routes to the answers.The analysis of political structure has been inspired by the questions, if not the methods and interpretations, of Sir Lewis Namier. The best of many examples are still Norman Gash's Politics in the Age of Peel and H. J. Hanham's Elections and Party Management. The main questions asked in such works are: What was the real, as opposed to the theoretical, framework of politics? How were politics actually conducted outside the House of Commons? How did the various reform acts affect the functioning of the electoral system? These works stress, in Gash' terminology, the “medium” in which the ordinary politician operated. In each case, they seem to emphasize continuity rather than change, and the enduring power of bribery, corruption, and influence. They have added a great deal to what the narratives tell us about Victorian politics, especially in regard to the realities of constituency operations, the origins and workings of party machinery, the problems of party finance, and the cost of elections. Structural investigations of parties, like Conor Cruise O'Brien's Parnell and His Party and E. J. Feuchtwanger's Disraeli, Democracy and the Tory Party have given a new dimension to party history. Perhaps most important, the structural studies have established the crucial significance of local factors and the comparative inconsequence of national issues in most elections.

scholarly journals Evaluation of an Improved Technique for Geosynthetic-Reinforced and Pile-Supported Embankment

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Jun Zhang ◽  
Shao-wen Liu ◽  
He-fu Pu
Keyword(s):  
Elastic Modulus ◽  
Conventional Technique ◽  
Cost Evaluation ◽  
Effective Measure ◽  
Parametric Studies ◽  
The Stability ◽  
Improved Technique ◽  
The Cost ◽  
Grps Embankment ◽  
Pile Supported Embankment

With a large number of applications of conventional technique for geosynthetic-reinforced and pile-supported (GRPS) embankment (called CT embankment), many deficiencies have been exposed. In view of the deficiencies, an improved technique, fixed-geosynthetic-reinforced and pile-supported embankment (called FGT embankment), is developed. To investigate the performance of the FGT embankment, the comparison analyses and parametric studies are conducted by Finite Element Method (FEM). The influencing factors investigated include elastic modulus of soil, tensile stiffness of geosynthetics, pile length, pile spacing, and pile elastic modulus. In addition, the cost evaluation for the FGT embankment and CT embankment is also made. The results show that the FGT embankment can significantly reduce the settlement and differential settlement, enhance the stability, and provide an economical and effective measure for the construction of high embankment at the bridge approach.

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