Study on Nonlinear Motion Behavior of Coupled Heave-Pitch for the Classic Spar Platform Based on AQWA

2012 ◽  
Vol 170-173 ◽  
pp. 2170-2174 ◽  
Author(s):  
Song Sang ◽  
Yuan Zhou ◽  
Xue Liang Jiang
Keyword(s):  
Incident Wave ◽  
Wave Amplitude ◽  
Wave Period ◽  
Critical Periods ◽  
Spar Platform ◽  
Natural Period ◽  
Nonlinear Motion ◽  
Motion Characteristic ◽  
Instability Parameter ◽  
Motion Behavior

This paper used AQWA software to research the nonlinear motion characteristic of heave-pitch coupling of classical Spar platform in regular waves. With classic Spar platform as an example, the wave amplitude and periodic changes’ effect to the nonlinear motion behavior of coupled heave-pitch is researched. After calculation, the critical periods corresponding to the different incident wave amplitude are obtained, based which, gets the instability parameter domain of coupling resonance of platform in the wave period-amplitude plane. The results in this paper show that the heave-pitch coupled resonance of platform depends on the wave amplitude and the ratio of the natural period of heave and pitch, and the incident wave period.

Interaction of the electromagnetic precursor from a relativistic shock with the upstream flow – II. Induced scattering of strong electromagnetic waves

2019 ◽  
Vol 490 (1) ◽  
pp. 1474-1478 ◽  
Author(s):  
Yuri Lyubarsky
Keyword(s):  
Incident Wave ◽  
Electromagnetic Waves ◽  
Wave Amplitude ◽  
Strong Wave ◽  
Relativistic Shock ◽  
Scattering Rate ◽  
Relativistic Shocks ◽  
Upstream Flow ◽  
Electromagnetic Precursor

ABSTRACT This is the second in the series of papers aiming to study interaction of the electromagnetic precursor waves from relativistic shocks with the upstream flow. Here, I consider the induced scattering of strong waves. In such a wave, the electrons oscillate with relativistic velocities therefore, the scattering generally occurs in harmonics of the incident wave. I show that the induced scattering occurs predominantly in the first harmonics. I also show that even though in the weak case regime, the induced scattering rate is proportional to the intensity of the incident wave, in the strong wave case, the rate decreases as the wave amplitude grows.

scholarly journals Laboratory Investigation on Hydrodynamic Performance of an Innovative Aeration Device with a Wave-Driven Heaving Buoy

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3262 ◽  
Author(s):  
Zegao Yin ◽  
Yanxu Wang ◽  
Yong Liu ◽  
Chengyan Gao ◽  
Huan Zhang
Keyword(s):  
Wave Height ◽  
Flow Rate ◽  
Incident Wave ◽  
Air Flow ◽  
Wave Period ◽  
Hydrodynamic Performance ◽  
Wave Steepness ◽  
Air Flow Rate ◽  
Rate Decrease ◽  
Relative Value

Coastal seawater quality is of significance for the environment, ecology and fisheries. In recent years, the hypoxia or anoxia problems of bottom seawater aggravated due mainly to the seawater stratification and eutrophication. This paper addresses an innovative aeration device with a wave-driven heaving buoy to enhance the dissolved oxygen concentration for bottom water. A series of physical experiments was conducted to investigate its hydrodynamic performance and air flow rate. The response amplitude of heaving components and the average value of air flow rate were examined with the related parameters, including incident wave height, incident wave steepness and aeration depth. It was found that with increasing incident wave height, the average heaving displacement and the average air flow rate increase respectively. With the increase of incident wave steepness, the relative value of average heaving displacement increases obviously for high wave period scenarios, it increases slightly for small wave period scenarios in comparison and the relative value of air flow rate increases evidently. With the increase of aeration depth, the average heaving displacement and the average air flow rate decrease respectively. With the increase of relative aeration depth, the relative value of average heaving displacement and the relative value of air flow rate decrease respectively. In addition, the dimensional analysis and the least squares methods were used to obtain the prediction formulas for the average heaving displacement and the average air flow rate, and they agreed well with the related experimental data.

Hysteresis jumps of the surface reactance of a layered superconductor as the incident wave amplitude varies

2010 ◽  
Vol 36 (1) ◽  
pp. 92-99 ◽  
Author(s):  
S. S. Apostolov ◽  
D. V. Kadygrob ◽  
Z. A. Mayselis ◽  
T. M. Slipchenko ◽  
S. E. Savel’ev ◽  
...  
Keyword(s):  
Incident Wave ◽  
Wave Amplitude ◽  
Layered Superconductor ◽  
Surface Reactance

Effect of Free Surface Nonlinear and Fluid Viscosity on Fluid Resonance in the Narrow Gap

2017 ◽  
Author(s):  
Sheng-chao Jiang ◽  
Li Zou ◽  
Tie-zhi Sun ◽  
Chang-feng Liu
Keyword(s):  
Free Surface ◽  
Energy Dissipation ◽  
Resonant Frequency ◽  
Incident Wave ◽  
Wave Amplitude ◽  
Relative Energy ◽  
Dominant Factor ◽  
Fluid Viscosity ◽  
Narrow Gap ◽  
Resonant Amplitude

Numerical simulations are carried out for gap resonance problem between two side-by-side non-identical boxes. The linear potential model over-predicts the resonant amplitude in the narrow gap because it not only neglects the energy dissipation due to vortical motion, but also neglect the nonlinearity due to free surface. More relative energy are reflected with the increase of incident wave amplitude, leading to the decrease of relative resonant amplitude and relative energy dissipation in the narrow gap at resonant frequency. When the incident wave frequency is outside a little band to resonant frequency, relative energy dissipation becomes the dominant factor for the decrease of relative wave amplitude in the narrow gap with the increase of incident wave amplitudes. In a word, both the free surface nonlinearity and fluid viscosity play the important, but different, roles on wave resonances in the narrow gap.

scholarly journals ANFIS and ANN models for the estimation of wind and wave-induced current velocities at Joeutsu-Ogata coast

2015 ◽  
Vol 18 (2) ◽  
pp. 371-391 ◽  
Author(s):  
Morteza Zanganeh ◽  
Abbas Yeganeh-Bakhtiary ◽  
Takao Yamashita
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
Water Depth ◽  
Incident Wave ◽  
Wind Direction ◽  
Significant Wave Height ◽  
Wave Period ◽  
Inference System ◽  
Significant Wave ◽  
Wave Induced

In this study, the adaptive network-based fuzzy inference system (ANFIS) and artificial neural network (ANN) were employed to estimate the wind- and wave-induced coastal current velocities. The collected data at the Joeutsu-Ogata coast of the Japan Sea were used to develop the models. In the models, significant wave height, wave period, wind direction, water depth, incident wave angle, and wind speed were considered as the input variables; and longshore and cross-shore current velocities as the output variables. The comparison of the models showed that the ANN model outperforms the ANFIS model. In addition, evaluation of the models versus the multiple linear regression and multiple nonlinear regression with power functions models indicated their acceptable accuracy. A sensitivity test proved the stronger effects of wind speed and wind direction on longshore current velocities. In addition, this test showed great effects of significant wave height on cross-shore currents' velocities. It was concluded that the angle of incident wave, water depth, and significant wave period had weaker influences on the velocity of coastal currents.

Characteristics of Leading Tsunami Waves Generated in Three Recent Tsunami Events

2014 ◽  
Vol 08 (03) ◽  
pp. 1440001 ◽  
Author(s):  
Chao An ◽  
Philip L.-F. Liu
Keyword(s):  
Water Depth ◽  
Wave Amplitude ◽  
Propagation Speed ◽  
Frequency Dispersion ◽  
Wave Period ◽  
Wave Crest ◽  
Haida Gwaii ◽  
Tsunami Waves ◽  
Wave Nonlinearity ◽  
Chile Tsunami

In this paper, the time series of ocean water surface elevation, recorded by Deep-ocean Assessment and Recording of Tsunamis (DART) sensors in the Pacific Ocean, during three recent tsunami events — 2010 Chile tsunami, 2011 Tohoku tsunami, and 2012 Haida Gwaii tsunami — are analyzed. The characteristics of leading tsunami waves are examined in terms of their propagation speed, wave period and wave amplitude so as to determine the importance of wave nonlinearity and frequency dispersion. Using the estimated arrival time of leading waves at each DART station and the distance from each station to the epicenter of the corresponding earthquake, the averaged propagation speed of leading waves for each event is calculated. It is found that the wave propagation speed for 2010 Chile tsunami is roughly 190 m/s, and is slightly slower than that of 2011 Tohoku and 2012 Haida Gwaii tsunamis, 210 m/s for both events. Two time scales associated with the leading waves are introduced: the duration of leading wave crest and the leading wave period obtained from a wavelet analysis. The results show that the leading wave crest duration is roughly 15–20 min and the wave period is roughly 25–30 min at most of DART stations for all the three events. The wave nonlinearity and frequency dispersion parameters, being defined as the wave amplitude to water depth ratio and the square of water depth to wavelength ratio, respectively, are calculated for the leading waves. The parameter for wave nonlinearity is found to be smaller than 4.0 × 10-4, while the parameter for frequency dispersion is smaller than 0.02 at all stations for all the three events. Finally, the cumulative effects of nonlinearity and frequency dispersion for the leading waves are investigated. It is found that the distances between the epicenter and all DART stations in each event are much smaller than those required for the nonlinearity and/or frequency dispersive effects to become significant.

Numerical Study on Mathieu Instability of DDMS Platform

2010 ◽  
Author(s):  
Binbin Li ◽  
Jinping Ou
Keyword(s):  
Numerical Study ◽  
Mooring Line ◽  
Early Investigation ◽  
Spar Platform ◽  
Mooring Lines ◽  
Natural Period ◽  
Ballast Tank ◽  
University Of Technology ◽  
Mathieu Instability ◽  
Decay Tests

Deep draft multi-spar (DDMS) is an innovative platform which is specially designed for deepwater drilling and production in 2009 by Center for Deepwater Engineering, Dalian University of Technology. The hard tank of DDMS is composed of four columns at corners and a novel moonpool protecting the top tension risers at center. In addition, the top tension and self-weight of rigid risers are provided by air-cans in the moonpool. At the foot of hard tank, the pontoons and horizontal bracing are used to connect the separated columns and moonpool. It is noted that two heave plates are directly integrated with the hard tank in order to reduce the heave response. The middle section consists of 4 columns of smaller diameter which connect the hard tank and ballast tank. The early investigation indicates that the global hydrodynamic and motion behavior of DDMS are similar with Spar platform, and furthermore the heave natural period is close to the half pitch natural period. Therefore the DDMS platform may have possibility to trigger the Mathieu instability which has been validated on Spar platform through the numerical and experimental method. In this paper, a coupled heave and pitch motion equations of DDMS platform are established with accounting the time-varying restoring heave and pitch restoring stiffness. A damping case matrix is generated considering the heave plate damping, mooring line damping and hull drag damping. The damping ratios are identified by free-decay tests. The nonlinear motions under the action of regular waves of different periods and heights are numerically solved by the 4th order Runge-kutta method. The calculational results reveal that the heave damping significantly influences the occurrence of pitch instability, meanwhile the damping contribution of heave plates and mooring lines also play an important role in suppressing the instability. The phenomenon of Mathieu instability is owing to the energy exchange in this paper, and the mechanism of this phenomenon is amply studied as well as 3 different ways of instability are summarized.

scholarly journals Run-up of nonlinear monochromatic wave on a plane beach in presence of a tide

2019 ◽  
Vol 59 (4) ◽  
pp. 529-532
Author(s):  
I. I. Didenkulova ◽  
E. N. Pelinovsky
Keyword(s):  
Exact Solution ◽  
Shallow Water ◽  
Nonlinear Problem ◽  
Incident Wave ◽  
Wave Amplitude ◽  
Monochromatic Wave ◽  
Shallow Water Theory ◽  
Long Wave ◽  
Run Up

The nonlinear problem of long wave run-up on a plane beach in a presence of a tide is solved within the shallow water theory using the Carrier-Greenspan approach. The exact solution of the nonlinear problem for wave run-up height is found as a function of the incident wave amplitude. Influence of tide on characteristics of wave run-up on a beach is studied.

scholarly journals Dasar Laut Sinusoidal Sebagai Reflektor Gelombang

2011 ◽  
Vol 2 (1) ◽  
pp. 441
Author(s):  
Viska Noviantri
Keyword(s):  
Asymptotic Expansion ◽  
Incident Wave ◽  
Large Amplitude ◽  
Wave Amplitude ◽  
Transmitted Wave ◽  
Bragg Resonance ◽  
Multi Scale ◽  
Reflected Wave ◽  
Incident Waves

This article discusses about the influence of sinusoidal sandbars towards the amplitude of incident wave. sinusoidal sandbars may lead to Bragg resonance. Basically, when a wave meets a different depth, it will scatter into a transmitted wave and a reflected wave. Bragg resonance happens when the wavelength of incident wave is twice of the wavelength of the periodic bottom disturbance. We apply the multi-scale asymptotic expansion to obtain the results. Eventually we find that a larger amplitude disturbance leads to larger reflected wave amplitude. This result explains that the sinusoidal sandbars indeed can reduce the amplitude of incident wave and protect a beach from large amplitude incident waves. 

scholarly journals SUBHARMONIC GENERATION OF TRANSVERSE OSCILLATIONS INDUCED BY INCIDENT REGULAR WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 11 ◽  
Author(s):  
Gang Wang ◽  
Jin-Hai Zheng
Keyword(s):  
Numerical Investigation ◽  
Incident Wave ◽  
Growth Rates ◽  
Wave Amplitude ◽  
Threshold Value ◽  
Steep Slope ◽  
Regular Waves ◽  
Constant Slope ◽  
Incident Waves ◽  
Transverse Oscillations

It is generally accepted that there are transverse oscillation, which are concentrated and confined to the backwall and decay asymptotically offshore, existed in the harbor of constant slope, however, whether these oscillations can be induced by the normally incident waves is not clear. This numerical investigation aims at providing the subharmonic generations of transverse oscillations within the harbor of a plane slope by waves normally impacting on. For the harbor of perfectly plane slopes, the subharmonic transverse oscillations are small on the mild and moderate slopes but evident on the steep slope. This instability can take place only if the incident wave amplitude exceeds a threshold value, and transverse oscillations can even grow up to a larger value than that of longitudinal oscillations. The magnitudes of transverse oscillations are approximately the same, only their growth rates are affected by the incident wave amplitude.

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