scholarly journals The added mass for two-dimensional floating structures

Wave Motion ◽  
2016 ◽  
Vol 64 ◽  
pp. 1-12 ◽  
Author(s):  
M. McIver ◽  
P. McIver
Keyword(s):  
Added Mass ◽  
Two Dimensional ◽  
Floating Structures

The Motions of Adjacent Floating Structures in Oblique Waves

1984 ◽  
Vol 106 (2) ◽  
pp. 199-205 ◽  
Author(s):  
N. Kodan
Keyword(s):  
Hydrodynamic Interaction ◽  
Diffraction Theory ◽  
Added Mass ◽  
Exciting Force ◽  
Irregular Waves ◽  
Two Dimensional ◽  
Oblique Waves ◽  
Floating Structures ◽  
The Relationship ◽  
Good Agreement

This paper describes the theory on the effects of hydrodynamic interaction between two parallel slender structures in oblique waves. The method is based on the two-dimensional diffraction theory including the interaction effect. According to Ohkusu’s theory, the sectional interaction effects on the added mass, damping coefficient and wave exciting force are evaluated by analyzing incoming waves generated by the oscillatory motion of corresponding sections. Numerical results of the wave exciting force and moment and motions for the case of a combination of a ship and a rectangular barge are presented and compared with the results from model experiments. The comparison shows good agreement. Finally, some attention is given to the relationship between the arrangement of the two structures and responses in irregular waves.

scholarly journals Dynamic response of a wedge through asymmetric free fall in 2 degrees of freedom

2017 ◽  
Vol 233 (1) ◽  
pp. 229-250 ◽  
Author(s):  
Parviz Ghadimi ◽  
Sasan Tavakoli ◽  
Abbas Dashtimanesh ◽  
Pouria Taghikhani
Keyword(s):  
Experimental Data ◽  
Dynamic Response ◽  
Degrees Of Freedom ◽  
Time Derivative ◽  
Free Fall ◽  
Added Mass ◽  
Roll Motion ◽  
Physical Parameters ◽  
Two Dimensional ◽  
Roll Speed

In this article, a mathematical model is presented for simulation of the coupled roll and heave motions of the asymmetric impact of a two-dimensional wedge body. This model is developed based on the added mass theory and momentum variation. To this end, new formulations are introduced which are related to the added mass caused by heave and roll motions of the wedge. These relations are developed by including the asymmetrical effects and roll speed. In addition, by considering the roll speed, a particular method is presented for the time derivative of half-wetted beam of an asymmetric wedge. Furthermore, two equations are derived for the roll and heave motions in which damping terms appear. Validity of the proposed method is verified by comparing the predicted results against available experimental data in two conditions of roll motion and no roll motion. Favorable agreement is observed between the predicted results and experimental data. The pressure and hydrodynamic load are computed, and the differences between the results associated with the considered conditions are explored. Subsequently, the effects of different physical parameters including deadrise angle, initial roll angle, and initial velocity on the dynamic response of a two-dimensional wedge section are investigated. Ultimately, time histories of hydrodynamic coefficients are determined in order to provide a better understanding of the derived equations.

Added Mass of a Three-Parameter Family of Two-Dimensional Forces Oscillating in a Free Surface

1959 ◽  
Vol 3 (01) ◽  
pp. 36-48
Author(s):  
L. Landweber ◽  
Matilde Macagno
Keyword(s):  
Free Surface ◽  
Added Mass ◽  
Small Error ◽  
Parameter Family ◽  
Radius Of Gyration ◽  
Two Dimensional ◽  
Transverse Axis ◽  
Section Area ◽  
Added Masses ◽  
The Given

The added-mass characteristics of shiplike forms, oscillating vertically or horizontally in a free surface, are derived for a three-parameter family of forms. The parameters varied are the draft-beam ratio, the section-area coefficient, and the ratio to the draft of the radius of gyration about the transverse axis in the free surface. The added-mass coefficients are presented as a series of curves for about 70 members of this family. It is suggested that the added masses of arbitrary shiplike sections may be obtained, with only small error, from these curves by interpolation at the parametric values of the given section.

Added Mass and Damping of Rectangular Bodies Close to the Free Surface

1984 ◽  
Vol 28 (04) ◽  
pp. 219-225
Author(s):  
John Nicholas Newman ◽  
Bjørn Sortland ◽  
Tor Vinje
Keyword(s):  
Hydrodynamic Force ◽  
Standing Waves ◽  
Present Theory ◽  
Added Mass ◽  
The Body ◽  
Simple Explanation ◽  
Two Dimensional ◽  
Infinite Depth ◽  
Calm Water ◽  
Heave Motion

A submerged two-dimensional rectangle in calm water with infinite depth is studied. The rectangle is oscillating in a heave motion. Negative added mass and sharp peaks in the damping and added-mass coefficients have been found when the submergence is small and the width of the shallow region on top of the rectangle is large. Resonant standing waves will occur in this area. A linear theory is developed to provide a relatively simple explanation of the occurrence of negative added mass for submerged bodies. The vertical hydrodynamic force is associated only with the flow in the shallow region, and the resulting pressure which acts on the top face of the rectangle. The results from this theory are compared with numerical results from the Frank method. The importance of the interaction effect between the top and the bottom of the body, which is neglected in the present theory, is discussed.

Two-dimensional analyses related to wave-energy extraction by submerged resonant ducts

1979 ◽  
Vol 91 (2) ◽  
pp. 253-317 ◽  
Author(s):  
James Lighthill
Keyword(s):  
Wave Energy ◽  
Pressure Fluctuations ◽  
Added Mass ◽  
Effective Pressure ◽  
Two Dimensional ◽  
Energy Extraction ◽  
Full Account ◽  
Optimum Energy ◽  
Mathematical Analyses ◽  
Experimental Comparisons

Submerged resonant ducts offer an approach to the design of wave-energy extraction devices consistent with the need for maximum seaworthiness. This paper gives a full account of one type of analysis of these systems, based upon two-dimensional wave hydrodynamics and linearized duct dynamics. The mathematical analyses are given in detail in § 2 while § 1 describes as concisely as possible (i) the assumptions underlying each analysis, (ii) its results and their implications for design, and (iii) any available experimental comparisons.One theoretical prediction, unexpected when it was first made but since confirmed by experiment (Knott & Flower 1979), is that the effective pressure fluctuations to which a resonant duct responds can be substantially greater than those that would be present at the level of the duct mouth if the duct were absent. Other important predictions are concerned with added mass, radiation damping and the conditions for optimum energy extraction, calculated below for a wide variety of mouth design configurations and internal duct geometries. Broad tentative conclusions from the analyses are given at the end of § 1.

scholarly journals A Semi-Analytical Method for Calculating the Hydrodynamic Force on Perforated Plates in Oscillating Flow

2019 ◽  
Author(s):  
Fredrik Mentzoni ◽  
Trygve Kristiansen
Keyword(s):  
Analytical Method ◽  
Hydrodynamic Force ◽  
Added Mass ◽  
Navier Stokes ◽  
Oscillating Flow ◽  
Force Model ◽  
Hydrodynamic Coefficients ◽  
Two Dimensional ◽  
Force Coefficient ◽  
Perforated Plates

Abstract A two-dimensional numerical analysis on the hydrodynamic force of perforated plates in oscillating flow is presented, and a new semi-analytical force model is proposed. Plates with ten different perforation ratios, τ, from 0.05 to 0.50 are simulated. The Keulegan–Carpenter numbers in the simulations cover a range from 0.002 to 2.2 when made nondimensional with the width of the plates. Resulting hydrodynamic added mass and damping coefficients are presented. All perforated plates with perforation ratios greater than or equal to 10% are found to be damping dominant. The numerical results are obtained using a two-dimensional Navier–Stokes solver (CFD), previously validated against dedicated 2D experiments on perforated plates. Furthermore, we present verification of the code against the analytical solid flat plate results by Graham. The presently obtained hydrodynamic coefficients are compared with the state-of-the-art semi-analytical method for force coefficient calculation of perforated plates by Molin, as well as the recommended practice for estimating hydrodynamic coefficients of perforated structures by DNV GL. Based on the CFD results, a new method for calculating the hydrodynamic force on perforated plates in oscillating flow is presented. The method is based on curve fitting the present CFD results for perforated plates, to the analytical expressions obtained for solid plates by Graham. In addition to its simplicity, a strength of the method is that coefficients for both the added mass and damping are obtained.

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