Numerical experiments on transverse oscillations induced by normal-incident waves in a rectangular harbor of constant slope

2013 ◽  
Vol 57 ◽  
pp. 1-10 ◽  
Author(s):  
Gang Wang ◽  
Jin-Hai Zheng ◽  
Jerome Peng-Yea Maa ◽  
Ji-Sheng Zhang ◽  
Ai-Feng Tao
Keyword(s):  
Numerical Experiments ◽  
Constant Slope ◽  
Incident Waves ◽  
Transverse Oscillations

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.

scholarly journals On the Resonance Hypothesis of Tsunami and Storm Surge Runup

2016 ◽  
Author(s):  
Nazmi Postacioglu ◽  
M. Sinan Özeren ◽  
Umut Canlı
Keyword(s):  
Normal Modes ◽  
Deep Ocean ◽  
Storm Surges ◽  
Underlying Mechanism ◽  
Radiation Damping ◽  
Resonant Frequencies ◽  
Constant Slope ◽  
Incident Waves ◽  
Determining Factor ◽  
Significant Resonance

Abstract. Resonance has recently been proposed as the fundamental underlying mechanism that shapes the amplification in coastal runup for both Tsunamis and storm surges. It is without doubt that the resonance plays a rôle in runup phenomena of various kinds, however we think that the extent at which it plays its role has not been completely understood. For incident waves, the best approach to investigate the rôle played by the resonance would be to calculate the normal modes by taking radiation damping into account and then test how those modes are excited by the incident waves. There are a small number of previous works that attempt to calculate the resonant frequencies but they do not relate the amplitudes of the normal modes to those of the incident wave. This is because, by not including radiation damping, they automatically induce a resonance that leads to infinite amplitudes, thus preventing them from predicting the exact contribution of the resonance to coastal runup. In this study we consider two different coastal geometries: an infinitely wide beach with a constant slope connecting to a flat-bottomed deep ocean and a bay with sloping bottom, again, connected to a deep ocean. For the fully 1-D problem we find significant resonance if the bathymetric discontinuity is large. For the 2-D ocean case the analysis shows that the wave confinement is very effective when the bay is narrow. The bay aspect-ratio is the determining factor for the radiation damping.

scholarly journals Laboratory and numerical experiments on stem waves due to monochromatic waves along a vertical wall

2018 ◽  
Vol 25 (3) ◽  
pp. 521-535
Author(s):  
Sung Bum Yoon ◽  
Jong-In Lee ◽  
Young-Take Kim ◽  
Choong Hun Shin
Keyword(s):  
Small Amplitude ◽  
Numerical Experiments ◽  
Vertical Wall ◽  
Wave Pattern ◽  
Angle Of Incidence ◽  
Stokes Waves ◽  
Wave Heights ◽  
Incident Waves ◽  
Good Agreement ◽  
Monochromatic Waves

Abstract. In this study, both laboratory and numerical experiments are conducted to investigate stem waves propagating along a vertical wall developed by the incidence of monochromatic waves. The results show the following features: for small-amplitude waves, the wave heights along the wall show a slowly varying undulation. Normalized wave heights perpendicular to the wall show a standing wave pattern. The overall wave pattern in the case of small-amplitude waves shows a typical diffraction pattern around a semi-infinite thin breakwater. As the amplitude of incident waves increases, both the undulation intensity and the asymptotic normalized wave height decrease along the wall. For larger-amplitude waves with smaller angle of incidence, the measured data clearly show stem waves. Numerical simulation results are in good agreement with the results of laboratory experiments. The results of present experiments favorably support the existence and the properties of stem waves found by other researchers using numerical simulations. The characteristics of the stem waves generated by the incidence of monochromatic Stokes waves are compared with those of the Mach stem of solitary waves.

Characteristics of bolus formation and propagation from breaking internal waves on shelf slopes

2016 ◽  
Vol 791 ◽  
pp. 260-283 ◽  
Author(s):  
Christine D. Moore ◽  
Jeffrey R. Koseff ◽  
Erin L. Hult
Keyword(s):  
Slope Angle ◽  
Propagation Speed ◽  
Wave Forcing ◽  
Initial Wave ◽  
Image Velocimetry ◽  
Planar Laser ◽  
Wave Trains ◽  
Run Up ◽  
Constant Slope ◽  
Incident Waves

A series of laboratory experiments was conducted to study the formation of internal boluses through the run up of periodic internal wave trains on a uniform slope/shelf topography in a two-layer stratified fluid system. In the experiments, the forcing parameters of the incident waves (wave amplitude and frequency) are varied for constant slope angle and layer depths. Simultaneous particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) measurements are used to calculate high resolution, two-dimensional velocity and density fields. Over the range of wave forcing conditions, four bolus formation types were observed: backward overturning into a coherent bolus, top breaking into a turbulent bolus, top breaking into a turbulent surge and forward breaking into a turbulent surge. Wave forcing parameters, including a wave Froude number $Fr$, a wave Reynolds number $Re$ and a wave steepness parameter $ka_{0}$, are used to relate initial wave forcing to a dominant bolus formation mechanism. Bolus characteristics, including the bolus propagation speed and turbulent components, are also related to wave forcing. Results indicate that for $Fr>0.20$ and $ka_{0}>0.40$, the generated boluses become more turbulent in nature. As wave forcing continues to increase further, boluses are no longer able to form.

scholarly journals Laboratory and numerical experiments on stem waves due to monochromatic waves along a vertical wall

2017 ◽  
Author(s):  
Sung Bum Yoon ◽  
Jong In Lee ◽  
Young Taek Kim ◽  
Choong Hun Shin
Keyword(s):  
Small Amplitude ◽  
Numerical Experiments ◽  
Wave Length ◽  
Vertical Wall ◽  
Wave Pattern ◽  
Angle Of Incidence ◽  
Physical Experiments ◽  
Wave Heights ◽  
Incident Waves ◽  
Monochromatic Waves

Abstract. In this study, both laboratory and numerical experiments are conducted to investigate stem waves propagating along a vertical wall developed by the incidence of monochromatic waves. The results show the following features: For small amplitude waves, the wave heights along the wall show a slowly varying undulation. Normalized wave heights perpendicular to the wall show a standing wave pattern. Thus, overall wave pattern in the case of small amplitude waves show a typical diffraction pattern around a semi-infinite thin breakwater. As the amplitude of incident waves increases, both the undulation intensity and the asymptotic normalized wave height decrease along the wall. For larger amplitude waves with smaller angle of incidence, the measured data show clearly stem waves. Numerical simulation results are in good agreement with the results of laboratory experiments. It is found from a simple geometric relationship of wave pattern that the lengthening of wave length due to the nonlinearity of waves is responsible for the development of stem waves along the wall. The existence and the properties of stem waves for sinusoidal waves found theoretically based on numerical simulations are fully supported by the physical experiments conducted in this study.

Controllable Compliance Joint For Human Oriented Robots

2013 ◽  
Vol 43 (1) ◽  
pp. 47-60
Author(s):  
Mihail Tsveov ◽  
Dimitar Chakarov
Keyword(s):  
Numerical Experiments ◽  
Position Control ◽  
Joint Stiffness ◽  
Joint Motion ◽  
Compliance Control ◽  
Leaf Springs ◽  
Antagonistic Actuation

Abstract In the paper, different approaches for compliance control for human oriented robots are revealed. The approaches based on the non- antagonistic and antagonistic actuation are compared. In addition, an approach is investigated in this work for the compliance and the position control in the joint by means of antagonistic actuation. It is based on the capability of the joint with torsion leaf springs to adjust its stiffness. Models of joint stiffness are presented in this paper with antagonistic and non-antagonistic influence of the spring forces on the joint motion. The stiffness and the position control possibilities are investigated and the opportunity for their decoupling as well. Some results of numerical experiments are presented in the paper too.

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