Radiation of waves by a cylinder submerged in water with ice floe or polynya

2015 ◽  
Vol 784 ◽  
pp. 373-395 ◽  
Author(s):  
Izolda V. Sturova
Keyword(s):  
Elastic Plate ◽  
Diffraction Problem ◽  
Open Water ◽  
Finite Depth ◽  
The Body ◽  
Elastic Plates ◽  
Radiation Problem ◽  
Radiation Load ◽  
Body Contour ◽  
Damping Coefficients

The problems of radiation (sway, heave and roll) of surface and flexural-gravity waves by a submerged cylinder are investigated for two configurations, concerning; (i) a freely floating finite elastic plate modelling an ice floe, and (ii) two semi-infinite elastic plates separated by a region of open water (polynya). The fluid of finite depth is assumed to be inviscid, incompressible and homogeneous. The linear two-dimensional problems are formulated within the framework of potential-flow theory. The method of mass sources distributed along the body contour is applied. The corresponding Green’s function is obtained by using matched eigenfunction expansions. The radiation load (added mass and damping coefficients) and the amplitudes of vertical displacements of the free surface and elastic plates are calculated. Reciprocity relations which demonstrate both symmetry of the radiation load coefficients and the relation of damping coefficients with the far-field form of the radiation potentials are found. It is shown that wave motion essentially depends on the position of the submerged body relative to the elastic plate edges. The results of solving the radiation problem are compared with the solution of the diffraction problem. It is noted that resonant frequencies in the radiation problem correlate with those frequencies at which the reflection coefficient in the diffraction problem has a local minimum.

The absorption of wave energy by a three-dimensional submerged duct

1981 ◽  
Vol 104 ◽  
pp. 189-215 ◽  
Author(s):  
J. R. Thomas
Keyword(s):  
Three Dimensional ◽  
Added Mass ◽  
Axisymmetric Body ◽  
The Body ◽  
Forced Oscillations ◽  
Radiation Problem ◽  
Absorption Length ◽  
Damping Coefficients ◽  
Sea Bed ◽  
Linear Spring

It has been shown (Evans 1976) that the power absorbed by a general, axisymmetric body depends solely upon the added-mass and damping coefficients. These coefficients are fundamental properties of the body, representing the component of the force on the body proportional to the acceleration and velocity of the body respectively in the radiation problem, where the body is forced to oscillate in the absence of incoming waves.In the present paper these coefficients are determined by solution of the radiation problem, for a mouth-upward cylindrical duct situated on the sea bed and fitted with a piston undergoing forced oscillations. The added-mass and damping coefficients are then used to study the power absorption properties of the duct when the power take-off is modelled by a linear-spring–dashpot system attached to the piston. Curves of the added mass, damping coefficients and absorption length (a measure of the power absorbed) as functions of wavenumber are presented, for different duct diameters and different depths of submergence.

Radiation and diffraction by a submerged sphere advancing in water waves of finite depth

1995 ◽  
Vol 448 (1932) ◽  
pp. 29-54 ◽  
Keyword(s):  
Water Waves ◽  
Finite Depth ◽  
Multipole Expansion ◽  
The Body ◽  
Field Equations ◽  
Damping Coefficients ◽  
Submerged Sphere ◽  
Added Masses ◽  
Exciting Forces ◽  
Depth Water

A submerged sphere advancing in a regular finite depth water wave at constant forward speed is analysed by linearized velocity potential. The solution is ob­tained by the multipole expansion extended from that developed for zero speed. Numerical results are obtained for wave-making resistance and lift, added masses, damping coefficients and exciting forces. Far field equations are also derived for calculating damping coefficients and exciting forces. They are used to check the results obtained from integrating pressure over the body surface. Excellent agree­ment is found.

scholarly journals Hydrodynamics of Moonpool-Type Floaters: A Theoretical and a CFD Formulation

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 570
Author(s):  
Anargyros S. Mavrakos ◽  
Dimitrios N. Konispoliatis ◽  
Dimitrios G. Ntouras ◽  
George P. Papadakis ◽  
Spyros A. Mavrakos
Keyword(s):  
Diffraction Problem ◽  
Finite Depth ◽  
The Body ◽  
Viscous Effects ◽  
Wave Energy Converters ◽  
Confined Fluid ◽  
Marine Industry ◽  
Calm Water ◽  
Sharp Edges ◽  
Computational Fluid Dynamics Cfd

Moonpool-type floaters were initially proposed for applications such as artificial islands or as protecting barriers around a small area enabling work at the inner surface to be carried out in relatively calm water. In recent years, a growing interest on such structures has been noted, especially in relation to their use as heaving wave energy converters or as oscillating water column (OWC) devices for the extraction of energy from waves. Furthermore, in the offshore marine industry, several types of vessels are frequently constructed with moonpools. The present paper deals with the hydrodynamics of bottomless cylindrical bodies having vertical symmetry axis and floating in a water of finite depth. Two computation methods were implemented and compared: a theoretical approach solving analytically the corresponding diffraction problem around the moonpool floater and a computational fluid dynamics (CFD) solver, which considers the viscous effects near the sharp edges of the body (vortex shedding) as non-negligible. Two different moonpool-type configurations were examined, and some interesting phenomena were discussed concerning the viscous effects and irregularities caused by the resonance of the confined fluid.

Preoperative and Postoperative Management of the Body Contour Patient

1996 ◽  
Vol 16 (4) ◽  
pp. 218-223
Author(s):  
R. Rohrich ◽  
P. B. Fodor ◽  
J. J. Petry ◽  
P. Vash
Keyword(s):  
Postoperative Management ◽  
The Body ◽  
Body Contour

Incipient Separation Near Corners

2018 ◽  
Author(s):  
Anatoly I. Ruban
Keyword(s):  
Corner Point ◽  
Analytic Form ◽  
The Body ◽  
Recirculation Region ◽  
Body Contour ◽  
Concave Corner ◽  
Attached Flow ◽  
Surface Deflection ◽  
Interaction Problem ◽  
Incipient Separation

Chapter 4 analyses the transition from an attached flow to a flow with local recirculation region near a corner point of a body contour. It considers both subsonic and supersonic flow regimes, and shows that the flow near a corner can be studied in the framework of the triple-deck theory. It assumes that the body surface deflection angle is small, and formulates the linearized viscous-inviscid interaction problem. Its solution is found in an analytic form. It also presents the results of the numerical solution of the full nonlinear problem. It shows how, and when, the separation region forms in the boundary layer. In conclusion, it suggests that in the subsonic flow past a concave corner, the solution is not unique.

Boundaries Influence on the Flow Field Around an Oscillating Sphere

2013 ◽  
Author(s):  
Domenica Mirauda ◽  
Antonio Volpe Plantamura ◽  
Stefano Malavasi
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Boundary Conditions ◽  
Damping Ratio ◽  
Water Channel ◽  
Open Water ◽  
Free Surface Flows ◽  
The Body ◽  
Sphere Diameter ◽  
Oscillating Sphere

This work analyzes the effects of the interaction between an oscillating sphere and free surface flows through the reconstruction of the flow field around the body and the analysis of the displacements. The experiments were performed in an open water channel, where the sphere had three different boundary conditions in respect to the flow, defined as h* (the ratio between the distance of the sphere upper surface from the free surface and the sphere diameter). A quasi-symmetric condition at h* = 2, with the sphere equally distant from the free surface and the channel bottom, and two conditions of asymmetric bounded flow, one with the sphere located at a distance of 0.003m from the bottom at h* = 3.97 and the other with the sphere close to the free surface at h* = 0, were considered. The sphere was free to move in two directions, streamwise (x) and transverse to the flow (y), and was characterized by values of mass ratio, m* = 1.34 (ratio between the system mass and the displaced fluid mass), and damping ratio, ζ = 0.004. The comparison between the results of the analyzed boundary conditions has shown the strong influence of the free surface on the evolution of the vortex structures downstream the obstacle.

Theory of Short Wave Excitation

1986 ◽  
Vol 30 (03) ◽  
pp. 147-152
Author(s):  
Yong Kwun Chung
Keyword(s):  
Incident Wave ◽  
Characteristic Length ◽  
Finite Depth ◽  
Short Wave ◽  
The Body ◽  
Wave Number ◽  
Floating Body ◽  
Wave Excitation ◽  
Exciting Forces ◽  
Wave Exciting Forces

When the wavelength of the incident wave is short, the total surface potential on a floating body is found to be 2∅ i & O (m-l∅ i) on the lit surface and O (m-l∅ j) on the shadow surface where ~b i is the potential of the incident wave and m the wave number in water of finite depth. The present approximation for wave exciting forces and moments is reasonably good up to X/L ∅ 1 where h is the wavelength and L the characteristic length of the body.

Morphological characterization of Trichotylenchus gorganiensis n. sp. (Nematoda: Dolichodoridae) and photomicrographs of several other species of the subfamily Telotylenchinae Siddiqi, 1960

Zootaxa ◽  
2018 ◽  
Vol 4526 (4) ◽  
pp. 447
Author(s):  
REZA GHADERI ◽  
AKBAR KAREGAR ◽  
ESMAEIL MIRAEIZ
Keyword(s):  
New Species ◽  
Morphological Characterization ◽  
The Body ◽  
Morphometric Data ◽  
Tail Region ◽  
Body Contour ◽  
Closely Related Species ◽  
Pharyngeal Bulb ◽  
Anal Sac

Trichotylenchus gorganiensis n. sp. is described and illustrated based on morphological and morphometric data. The new species is characterized by its 760–1073 µm long body, conoid-rounded lip region continuous with the body contour and bearing 5–7 fine striae, 22.0–24.5 µm long stylet, basal pharyngeal bulb offset or slightly overlapping intestine, post-anal sac extending 50–73 % of the tail region, and cylindrical or subclavate tail with a striated terminus. Differences of the new species from the closely related species T. astriatus, T. astriatoides, T. changlingensis and T. papyrus are discussed. Photomicrographs and several taxonomic notes on 13 other species of Telotylenchinae, collected from Iran, are provided. 

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