Nonlinear Damping of Standing Waves on Shallow Water

1973 ◽  
Vol 51 (20) ◽  
pp. 2175-2183 ◽  
Author(s):  
F. L. Curzon ◽  
M. G. R. Phillips
Keyword(s):  
Theoretical Model ◽  
Shallow Water ◽  
Standing Wave ◽  
Oscillation Frequency ◽  
Excitation Frequency ◽  
Standing Waves ◽  
Nonlinear Effects ◽  
Resonance Curve ◽  
Nonlinear Damping ◽  
Good Agreement

The amplitude of a standing wave on shallow water has been observed as a function of the excitation frequency (ω) in conditions where nonlinear effects are important. It is found that the peak of the normal resonance curve is flattened, due to extra damping caused by resonant, nonlinear generation of a wave having an oscillation frequency of 2ω. The experimental observations are in good agreement with the theoretical model presented in the paper.

scholarly journals Prediction of the dynamic response of a plate treated by particle impact damper

2013 ◽  
Vol 228 (5) ◽  
pp. 799-814 ◽  
Author(s):  
Moez Trigui ◽  
Emmanuel Foltete ◽  
Noureddine Bouhaddi
Keyword(s):  
Dynamic Response ◽  
Excitation Frequency ◽  
Element Model ◽  
Nonlinear Damping ◽  
Design Parameters ◽  
Particle Impact ◽  
Equivalent Viscous Damping ◽  
Impact Damper ◽  
Experimental Characterisation ◽  
Good Agreement

In this paper, an experimental characterisation of a particle impact damper (PID) under periodic excitation is investigated. The developed method allows the measurement of damping properties of PID without the supplementary use of a primary structure. The passive damping of PID varies with the excitation frequency and its design parameters. The nonlinear damping of PID is then interpreted as an equivalent viscous damping to be introduced in a finite element model of a structure to predict its dynamic response. The results of numerical simulations are in good agreement with those of experiment and show the relevance of the developed method to predict the dynamic behaviour of a structure treated by PID’s.

Nonlinear effects in trapped modes of standing waves on the surface of shallow water

2000 ◽  
Vol 45 (12) ◽  
pp. 1513-1517 ◽  
Author(s):  
D. A. Indeitsev ◽  
E. V. Osipova
Keyword(s):  
Shallow Water ◽  
Standing Waves ◽  
Nonlinear Effects ◽  
Trapped Modes

Tire Vibrations

1977 ◽  
Vol 5 (4) ◽  
pp. 202-225 ◽  
Author(s):  
G. R. Potts ◽  
C. A. Bell ◽  
L. T. Charek ◽  
T. K. Roy
Keyword(s):  
Natural Frequencies ◽  
Standing Waves ◽  
Resonant Mode ◽  
Mode Shapes ◽  
Resonant Vibrations ◽  
Resonant Frequencies ◽  
Radial Tire ◽  
Analysis Techniques ◽  
Thin Ring ◽  
Good Agreement

Abstract Natural frequencies and vibrating motions are determined in terms of the material and geometric properties of a radial tire modeled as a thin ring on an elastic foundation. Experimental checks of resonant frequencies show good agreement. Forced vibration solutions obtained are shown to consist of a superposition of resonant vibrations, each rotating around the tire at a rate depending on the mode number and the tire rotational speed. Theoretical rolling speeds that are upper bounds at which standing waves occur are determined and checked experimentally. Digital Fourier transform, transfer function, and modal analysis techniques used to determine the resonant mode shapes of a radial tire reveal that antiresonances are the primary transmitters of vibration to the tire axle.

scholarly journals Analysis of a Cantilevered Piezoelectric Energy Harvester in Different Orientations for Rotational Motion

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1206 ◽  
Author(s):  
Wei-Jiun Su ◽  
Jia-Han Lin ◽  
Wei-Chang Li
Keyword(s):  
Theoretical Model ◽  
Resonant Frequency ◽  
Rotational Motion ◽  
Axial Load ◽  
Energy Harvester ◽  
Excitation Frequency ◽  
Experimental Studies ◽  
Piezoelectric Energy ◽  
Piezoelectric Cantilever ◽  
Tip Mass

This paper investigates a piezoelectric energy harvester that consists of a piezoelectric cantilever and a tip mass for horizontal rotational motion. Rotational motion results in centrifugal force, which causes the axial load on the beam and alters the resonant frequency of the system. The piezoelectric energy harvester is installed on a rotational hub in three orientations—inward, outward, and tilted configurations—to examine their influence on the performance of the harvester. The theoretical model of the piezoelectric energy harvester is developed to explain the dynamics of the system and experiments are conducted to validate the model. Theoretical and experimental studies are presented with various tilt angles and distances between the harvester and the rotating center. The results show that the installation distance and the tilt angle can be used to adjust the resonant frequency of the system to match the excitation frequency.

Theoretical Prediction of Motions of High-Speed Planing Boats in Waves

1978 ◽  
Vol 22 (03) ◽  
pp. 140-169
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Nonlinear Effects ◽  
Theoretical Method ◽  
Valuable Insight ◽  
Response Characteristics ◽  
Theoretical Predictions ◽  
Response Amplitude Operators ◽  
Phase Angles ◽  
Good Agreement

A theoretical method is derived for predicting the linearized response characteristics of constant deadrise high-speed planing boats in head and following waves. Comparisons of the theoretical predictions of the pitch and heave response amplitude operators and phase angles with existing experimental data show reasonably good agreement for a wide variety of conditions of interest. It appears that nonlinear effects are more severe at a speed to length ratio of 6 than of, say, 4 or less, principally because of the reduction of the damping ratio of the boat with increasing speed, and the consequent increase in motions in the vicinity of the resonant encounter frequency. However, it is concluded that the linear theory can provide a simple and fast means of determining the effect of various parameters such as trim angle, deadrise, loading, and speed on the damping, natural frequency, and linearized response in waves, and that this can furnish valuable insight into the actual boat dynamics, even though the accurate predictions of large motions and peak accelerations would require a nonlinear analysis.

Analytical and Experimental Simulation of Loose Pedestal Dynamic Effects on a Rotating Machine Vibrational Response

1991 ◽  
Author(s):  
Pavel Goldman ◽  
Agnes Muszynska
Keyword(s):  
Excitation Frequency ◽  
Experimental Studies ◽  
Experimental Simulation ◽  
Physical Parameters ◽  
Vibrational Response ◽  
Rotating Machine ◽  
Qualitative Pattern ◽  
The Impact ◽  
Good Agreement ◽  
Periodic Changes

Abstract This report presents experimental, analytical, and numerical results describing vibrational phenomena in a rotating machine with one loose pedestal. The loose-pedestal machine rotor vibrations represent unbalance-related excited vibrations of synchronous and fractional subsynchronous regimes. In this study the loose-pedestal machine is first simulated by a simple vibrating beam excited by a shaker mounted on it. The shaker simulates an unbalanced machine rotor. The beam occasionally enters in contact with the foundation. The excited vibrations are modified by impacting occurrences, and by periodic changes in system stiffness. A new model of the impact has been developed. The results of analytical and experimental studies stand in a good agreement. They illustrate the existence of the synchronous regime and several subsynchronous fractional regimes in various excitation frequency ranges. The analysis adequately predicts the occurrence of these regimes and determines the physical parameters affecting them. The analytical and experimental results are then compared with the responses of experimental rotor rig with one bearing pedestal looseness. They show the same qualitative pattern.

The structure of the Cincinnati arch as determined by short period Rayleigh waves

1969 ◽  
Vol 59 (1) ◽  
pp. 399-407
Author(s):  
Robert B. Herrmann
Keyword(s):  
Experimental Data ◽  
Theoretical Model ◽  
Layer Thickness ◽  
Rayleigh Waves ◽  
Layer Model ◽  
Depth Data ◽  
Short Period ◽  
Best Fitting ◽  
Good Agreement

Abstract The propagation of Rayleigh waves with periods of 0.4 to 2.0 seconds across the Cincinnati arch is investigated. The region of investigation includes southern Indiana and Ohio and northern Kentucky. The experimental data for all paths are fitted by a three-layer model of varying layer thickness but of fixed velocity in each layer. The resulting inferred structural picture is in good agreement with the known basement trends of the region. The velocities of the best fitting theoretical model agree well with velocity-depth data from a well in southern Indiana.

scholarly journals Instability of standing waves for non-linear Schrödinger-type equations

1988 ◽  
Vol 8 (8) ◽  
pp. 119-138 ◽  
Keyword(s):  
Dynamical Systems ◽  
Standing Wave ◽  
Optical Waveguides ◽  
Standing Waves ◽  
Positive Eigenvalue ◽  
Shooting Argument ◽  
Wave Solutions ◽  
Non Linear ◽  
Linearized Operator

AbstractA theorem is proved giving a condition under which certain standing wave solutions of non-linear Schrödinger-type equations are linearly unstable. The eigenvalue equations for the linearized operator at the standing wave can be analysed by dynamical systems methods. A positive eigenvalue is then shown to exist by means of a shooting argument in the space of Lagrangian planes. The theorem is applied to a situation arising in optical waveguides.

Investigation of Sinkage and Trim by Ships in Shallow Water Based on Overset Grid

2015 ◽  
Vol 713-715 ◽  
pp. 2126-2132
Author(s):  
Da Ming Sun ◽  
Ji Yong Liu ◽  
Qing Wen Kong
Keyword(s):  
Shallow Water ◽  
Equations Of Motion ◽  
Navier Stokes ◽  
Overset Grid ◽  
Ship Hulls ◽  
Surface Ship ◽  
Solving Equations ◽  
Sinkage And Trim ◽  
Volume Method ◽  
Good Agreement

A study on the navigation behavior for ships in shallow water had been carried out on CFD. The problem of surface ship hulls free of sinkage and trim in shallow water is analyzed numerically by simultaneously solving equations of the Reynolds averaged Navier-Stokes (RANS). The computations, based on the single-phase level set and overset grid, are discretized by finite volume method (FVM). An earth-based reference system is used for the solution to the fluid flow, while a ship-based reference is used to compute the rigid-body equations of motion. A S60 CB=0.6 ship model is taken as an example to the numerical simulation. Numerical results of the sinkage and trim of the seven Froude Numbers (Fn=0.5~0.8) are compared against experimental data, which have a good agreement.

scholarly journals ADDED MASSES OF LARGE TANKERS BERTHING TO DOLPHINS

1976 ◽  
Vol 1 (15) ◽  
pp. 161 ◽  
Author(s):  
Taizo Hayashi ◽  
Masujiro Shirai
Keyword(s):  
Shallow Water ◽  
Froude Number ◽  
Water Depth ◽  
Head Loss ◽  
Theoretical Formula ◽  
Counter Flow ◽  
Added Masses ◽  
Mass Factor ◽  
Large Vessels ◽  
Good Agreement

The added masses of large tankers berthing to dolphins are studied both theoretically and experimentally. The movements of large vessels in shallow water in the directions normal to their planes of symmetry cause counterflows of appreciable velocities under the hulls. The inertia of these counter-flows is shown to have an important effect on the added masses of the vessels. A theoretical formula is derived to determine the mass factor of an ocean vessel in shallow water as a function of the ratio Draught/Water- depth, the Froude number of the vessel and the coefficient of head loss of the counter-flow under the hull. Experiment is made to determine the mass factor. Comparison:, between the theory and the experiment shows a good agreement.

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