Vibration of otolithlike scatterers due to low frequency harmonic wave excitation in water.

2011 ◽  
Vol 129 (4) ◽  
pp. 2472-2472 ◽  
Author(s):  
Carl R. Schilt ◽  
Ted W. Cranford ◽  
Petr Krysl ◽  
Anthony D. Hawkins
Keyword(s):  
Harmonic Wave ◽  
Low Frequency ◽  
Wave Excitation ◽  
Frequency Harmonic

Inertia, Damping, and Wave Excitation of Heaving Coaxial Cylinders

2012 ◽  
Author(s):  
Fun Pang Chau ◽  
Ronald W. Yeung
Keyword(s):  
Low Frequency ◽  
Bottom Surface ◽  
Hydrodynamic Coefficients ◽  
Wave Excitation ◽  
Hydrodynamic Properties ◽  
Coaxial Cylinders ◽  
Ocean Wave Energy ◽  
Matched Eigenfunction Expansions ◽  
Frequency Behavior ◽  
Analytical Expressions

The method of matched eigenfunction expansions is applied in this paper to obtain the hydrodynamic coefficients of a pair of coaxial cylinders, each of which can have independent movement. The geometry idealizes a device for extracting ocean wave energy in the heave mode. The effects of geometric variations and the interaction between cylinders on the hydrodynamic properties are discussed. Analytical expressions for the low-frequency behavior of the hydrodynamic coefficients are also derived. The wave-exciting force on the bottom surface of either one of the cylinders is derived using the radiation solutions, with a generalized form of the Haskind relation developed for this geometry. The presented results are immediately applicable to examine free motion of coaxial cylinders in a wave field.

Filter for testing low-frequency harmonic analyzers S5-2 and S5-3

1974 ◽  
Vol 17 (4) ◽  
pp. 616-617
Author(s):  
A. S. Karavaev ◽  
L. V. Mishin
Keyword(s):  
Low Frequency ◽  
Frequency Harmonic

Localized Vibration Isolation Strategy for Low-Frequency Excitations in Membrane Space Structures

2006 ◽  
Vol 128 (6) ◽  
pp. 790-797 ◽  
Author(s):  
Hiraku Sakamoto ◽  
K. C. Park
Keyword(s):  
Vibration Isolation ◽  
Controller Design ◽  
Low Frequency ◽  
Space Structures ◽  
Membrane Structures ◽  
Low Frequency Vibration ◽  
And Control ◽  
Structural Mass ◽  
The Web ◽  
Frequency Harmonic

The present study explores both structural and controller design to attenuate vibration in large membrane space structures, especially due to low-frequency harmonic excitations. It is very difficult for membrane structures to suppress the low-frequency vibration induced by flexible support structures, because a lightly prestressed membrane has extremely low mode frequencies and little damping effect. The present study proposes the use of weblike perimeter cables around a membrane, and the application of simple and lightweight active controllers only along the web cables in order to isolate the membrane from vibration. This strategy successfully reduces the membrane vibration when the web-cable configuration is appropriately tailored. Both linear and nonlinear finite-element analyses exhibit a clear tradeoff between structural mass and control efficiency.

High-Frequency Harmonic Effects on Low-Frequency Iron Losses

2014 ◽  
Vol 50 (11) ◽  
pp. 1-4 ◽  
Author(s):  
Lucian Petrea ◽  
Cristian Demian ◽  
Jean Francois Brudny ◽  
Thierry Belgrand
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Iron Losses ◽  
High Frequency Harmonic ◽  
Frequency Harmonic

Viscous Drift Force and Motion Analysis of Semi-Submersible in Storm Sea States Compared With Model Tests

2017 ◽  
Author(s):  
Limin Yang ◽  
Erik Falkenberg ◽  
Arne Nestegård ◽  
Jørn Birknes-Berg
Keyword(s):  
Frequency Response ◽  
Potential Flow ◽  
Low Frequency ◽  
Model Tests ◽  
Viscous Drag ◽  
Wave Forces ◽  
Linear Wave ◽  
Wave Excitation ◽  
Frequency Wave ◽  
Drift Force

Standard analysis models applied for motions of moored floaters are based on potential flow perturbation methods with wave frequency response governed by first order wave forces and low-frequency response governed by second-order difference frequency wave forces. These models have been shown to have limitations in extreme sea states where nonlinear wave excitation and viscous drag forces above still water level may dominate. This effect is particularly visible for the low frequency excitation since the potential flow contribution goes to zero for long waves. In the present study non-linear wave excitation and viscous drag contributions on a semi-submersible is modelled by Morison’s load formula since the columns and pontoons are slender elements. A numerical simulation model is developed using SIMO [6], in which viscous forces and damping are included by the drag term of Morison equation and with drag coefficients recommended from DNV-RP-C205 [1]. Low frequency surge responses calculated by the combined potential flow drift forces and viscous drag from Morison load model are compared with model tests for waves only and for combined wave and current conditions. A simplified formula for current and viscous effects on wave drift force, generalized to non-collinear conditions is presented and compared with model test results.

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