scholarly journals The wave-making resistance of ships: a theoretical and practical analysis

1909 ◽  
Vol 82 (554) ◽  
pp. 276-300 ◽  
Keyword(s):  
Experimental Study ◽  
Theoretical Investigation ◽  
Frictional Coefficient ◽  
Frictional Resistance ◽  
Total Resistance ◽  
Forward Motion ◽  
Practical Analysis ◽  
Hydrodynamical Theory

The theoretical investigation of the total resistance to the forward motion of a ship is usually simplified by regarding it as the sum of certain independent terms such as the frictional, wave-makings and eddy-making resistances. The experimental study of frictional resistance leads to a formula of the type. R s =ƒSV m , (1) where S is the wetted surface, V the speed,ƒ a frictional coefficient, and m an index whose value is about 1.83. After deducting from the total resistance the frictional part calculated from a suitable formula of this kind, the remainder is called the residuary resistance. Of this the wave-making resistance is the most important part; the present paper is limited to the study of wave-making resistance, and chiefly its variation with the speed of the ship. The hydrodynamical theory as it stands at present may be stated briefly.

scholarly journals The diurnal variation of terrestrial magnetism

1914 ◽  
Vol 89 (612) ◽  
pp. 379-392 ◽  
Keyword(s):  
Experimental Study ◽  
Diurnal Variation ◽  
Observational Data ◽  
Theoretical Investigation ◽  
Small Degree ◽  
Law And Order ◽  
Terrestrial Magnetism ◽  
The Earth ◽  
Reasonable Proportion ◽  
The Subject

The diurnal variation of terrestrial magnetism has been the subject of experimental study for many years, and at a considerable number of observatories scattered all over the earth. But the co-ordination of the results, and the theoretical investigation of the physical cause or causes of the phenomena, have not made progress which seems to bear a reasonable proportion to the vast amount of observational data that has accumulated. As far as I know, Dr. Arthur Schuster’s memoirs constitute the most inspiring and systematic attempt to reduce this matter to scientific law and order. Although I have found it convenient to depart from the method pursued by Schuster, this change of procedure was in no small degree suggested by various remarks in his memoirs.

scholarly journals Research on Ship Hull Optimisation of High-Speed Ship Based on Viscous Flow/Potential Flow Theory

2020 ◽  
Vol 27 (1) ◽  
pp. 18-28
Author(s):  
Zhang Baoji
Keyword(s):  
High Speed ◽  
Design Method ◽  
Frictional Resistance ◽  
Linear Wave ◽  
Total Resistance ◽  
Friction Resistance ◽  
Resistance Reduction ◽  
Before And After ◽  
Reduction Effect ◽  
Cfd Method

AbstractIn order to quickly obtain practical ship forms with good resistance performance, based on the linear wave-making resistance theory, the optimal design method of ship forms with minimum total resistance is discussed by using the non-linear programming (NLP) method. Taking the total resistance as the objective function (the Michell integral is used to calculate the wave-making resistance and the equivalent plate friction resistance formula is used to calculate the frictional resistance), the hull surface offset as the design variable and appropriate displacement as the basic constraints, and considering the additional constraints, the hull bow shape and the whole ship are optimised, and an improved hull form is obtained. The resistance of the ship before and after optimisation is calculated by the CFD method to further evaluate the resistance reduction effect and performance after optimisation. Finally, an example of optimisation calculation of an actual high-speed ship is given. The obvious resistance reduction results confirm the reliability of the optimisation design method.

scholarly journals Research on a method of hull form design based on wave-making resistance optimization

2012 ◽  
Vol 19 (3) ◽  
pp. 16-25 ◽  
Author(s):  
Jianglong Sun ◽  
Xujian Lv ◽  
Weibin Liu ◽  
Hanwen Ning ◽  
Xianwen Chen
Keyword(s):  
Cross Section ◽  
Frictional Resistance ◽  
Wave Resistance ◽  
Total Resistance ◽  
Hull Form ◽  
Mathematical Procedure ◽  
Result Show ◽  
Form Design ◽  
Hull Form Design ◽  
Resistance Performance

ABSTRACT In this paper, we consider an optimization of the hull shape in order to minimize the total resistance of a ship. The total resistance is assumed to be the sum of the wave resistance computed on the basis of the thin-ship theory and the frictional resistance. Smoothness of hull lines is proved with mathematical procedure, in which differentials of the hull lines functions are analyzed. The wave-making resistance optimization, involving a genetic algorithm, uses Michell integral to calculate wave resistance. A certain hull form is generated by the method using cross section information of a modified DTMB model ship 5415 and a comparative experiment is carried out. Experimental and calculation result show that the method is of good adaptability for designing certain types of ships with excellent resistance performance.

Study of Prismatic Planing Model Spray and Resistance Components

1983 ◽  
Vol 27 (03) ◽  
pp. 187-196
Author(s):  
Robert Latorre
Keyword(s):  
Frictional Resistance ◽  
Total Resistance ◽  
Wide Beam ◽  
Resistance Components ◽  
Turbulent Transition ◽  
Measured Resistance ◽  
Pressure Resistance ◽  
Resistance Tests ◽  
Resistance Component ◽  
Good Agreement

The results of a study of prismatic planing model spray and resistance components are presented. The calculated total resistance values are shown to be in good agreement with the measured resistance. The features of the whisker spray and spray blister are discussed along with an experimental technique using wide-beam prismatic models for measuring the spray thickness. A derivation based on energy considerations of the prismatic planing hull pressure resistance component and the spray thickness is presented. The spray thickness values calculated from this formulation are in qualitative agreement with the measured spray thickness. The frictional resistance component obtained from the resistance measurements indicated an extensive laminar flow on the planing model bottom. An acetanilid film was sprayed on the planing model bottom which tripped the laminar-turbulent transition. The CF-values estimated from the acetanilid film pattern were found to be 75 to 90 percent of the CF-values estimated from the corresponding resistance tests.

Experimental Study on Critical Design of Electro-Hydrostatic Actuators Small in Size and Light in Weight

2020 ◽  
Vol 32 (5) ◽  
pp. 911-922
Author(s):  
Mitsuo Komagata ◽  
Tianyi Ko ◽  
Ko Yamamoto ◽  
Yoshihiko Nakamura ◽  
◽  
...  
Keyword(s):  
Experimental Study ◽  
Theoretical Investigation ◽  
High Reliability ◽  
Viscous Friction ◽  
Human Environment ◽  
Critical Design ◽  
Involute Gear ◽  
Actuation Systems ◽  
Current Systems

Actuation systems for robots and other machines used in critical applications is an area that requires further research. In such applications, a machine works in a human environment and physically interacts with humans. Reliability and backdrivability are still insufficient in current systems. An electro-hydrostatic actuator has the potential advantage of high reliability by nature and high backdrivability in mechanical simplexity when it is designed to be small and light. This study provides a theoretical investigation of the methods for evaluating internal leaks and other mechanical losses, such as Coulomb and viscous friction, and experimentally evaluates two types (trochoid and involute gear) of prototyped hydraulic pumps.

Numerical and Experimental Analysis of Added Resistance of Ships in Waves

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Ould el Moctar ◽  
Sebastian Sigmund ◽  
Jens Ley ◽  
Thomas E. Schellin
Keyword(s):  
Water Resistance ◽  
Frictional Resistance ◽  
Medium Size ◽  
Total Resistance ◽  
Added Resistance ◽  
Short Waves ◽  
Radiation Forces ◽  
Calm Water ◽  
Added Resistance In Waves ◽  
Force Components

Two Reynolds-Averaged Navier–Stokes (RANS) based field methods numerically predicted added resistance in regular head waves for a 14,000 TEU containership and a medium size cruise ship. Long and short waves of different frequencies were considered. Added resistance was decomposed into diffraction and radiation force components, whereby diffraction forces were obtained by restraining the ship in waves and radiation forces by prescribing the motions of the ship in calm water. In short waves, the diffraction part of total resistance was dominant as almost no ship motions were induced. In long waves, the sum of diffraction and radiation forces exceeded total resistance, i.e., the interaction of these two force components, which caused the reduction of total resistance, needed to be accounted for. Predictions were compared with model test measurements. Particular emphasis was placed on the following aspects: discretization errors, frictional resistance as part of total added resistance in waves, and diffraction and radiation components of added resistance in waves. Investigations comprised two steps, namely, a preliminary simulation to determine calm water resistance and a second simulation to compute total resistance in waves, always using the same grids. Added resistance was obtained by subtracting calm water resistance from total averaged wave resistance. When frictional resistance dominated over calm water resistance, which holds for nearly all conventional ships at moderate Froude numbers, high grid densities were required in the neighborhood surrounding the hull as well as prism cells on top of the model's surface.

Experimental Study on the Frictional Resistance of Gas Flow in Vertical Helically Coiled Pipe

2013 ◽  
Vol 313-314 ◽  
pp. 662-665
Author(s):  
Shui Hua Zheng ◽  
Jie Gang Mu ◽  
Wen Can Fan
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Friction Factor ◽  
Gas Flow ◽  
Frictional Resistance ◽  
Operating Conditions ◽  
Partial Data

Experiments were carried out to learn about the frictional resistance of gas flow in vertical helically coiled pipe. The expression of friction factor was established and the formula used to calculate the frictional resistance of gas flow in vertical helically coiled pipe was defined based on partial data got from different experiment conditions. The calculating formula was verified by the experimental data. The results show that the formula is accurate enough to calculate the frictional resistance of gas flow in similar operating conditions.

Numerical and Experimental Analysis of Added Resistance of Ships in Waves

2015 ◽  
Author(s):  
Ould el Moctar ◽  
Sebastian Sigmund ◽  
Thomas E. Schellin
Keyword(s):  
Water Resistance ◽  
Frictional Resistance ◽  
Medium Size ◽  
Total Resistance ◽  
Added Resistance ◽  
Short Waves ◽  
Radiation Forces ◽  
Calm Water ◽  
Added Resistance In Waves ◽  
Force Components

A RANS-based field method numerically predicted added resistance in regular head waves for a 14000 TEU containership (Duisburg Test Case) and a medium-size cruise ship. We concentrated our investigations on short waves. For different frequencies, we decomposed added resistance into diffraction and radiation force components, whereby diffraction forces were obtained by restraining the ship in waves and radiation forces, by prescribing the motions of the ship in calm water. In short waves, the diffraction part of total resistance was dominant as almost no ship motions were induced. In long waves, the sum of diffraction and radiation forces exceeded total resistance, i.e., the interaction of these two force components, which caused the reduction of total resistance, had to be accounted for. Predictions were compared with model test measurements. Particular emphasis was placed on the following aspects: discretization errors, frictional resistance as part of total added resistance in waves, diffraction and radiation components of added resistance in waves, and the influence of surge motion on added resistance. Investigations comprised two steps, namely, a preliminary simulation to determine calm-water resistance and a second simulation to compute total resistance in waves, always using the same grids. Added resistance was obtained by subtracting calm-water resistance from total averaged wave resistance. When frictional resistance dominated calm-water resistance, which holds for nearly all conventional ships at moderate Froude numbers, high grid densities were required in the neighborhood surrounding the hull.

scholarly journals Ring-Opening Carbonyl-Olefin Metathesis of Norbornenes

2019 ◽  
Author(s):  
Janis Jermaks ◽  
Phong K. Quach ◽  
Zara M. Seibel ◽  
Julien Pomarole ◽  
Tristan Lambert
Keyword(s):  
Experimental Study ◽  
Theoretical Investigation ◽  
Olefin Metathesis ◽  
Ring Opening ◽  
Activation Barrier ◽  
Reaction Pathway ◽  
Next Generation ◽  
Methyl Group ◽  
Optimized Conditions ◽  
Hydrolysis Of

<div> <p>A computational and experimental study of the hydrazine-catalyzed ring-opening carbonyl-olefin metathesis of norbornenes is described. Detailed theoretical investigation of the energetic landscape for the full reaction pathway with six different hydrazines revealed several crucial aspects for the design of next-generation hydrazine catalysts. This study indicated that a [2.2.2]-bicyclic hydrazine should offer substantially increased reactivity versus the previously reported [2.2.1]-hydrazine due to a lowered activation barrier for the rate-determining cycloreversion step, a prediction which was verified experimentally. Optimized conditions for both cycloaddition and cycloreversion steps were identified, and a brief substrate scope study for each was conducted. A complication for catalysis was found to be the slow hydrolysis of the ring-opened hydrazonium intermediates, which were shown to suffer from a competitive and irreversible cycloaddition with a second equivalent of norbornene. This problem was overcome by the strategic incorporation of a bridgehead methyl group on the norbornene ring, leading to the first demonstrated catalytic carbonyl-olefin metathesis of norbornene rings.</p> </div>

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