We revisit experimental studies performed by Ekman on dead-water (Ekman, 1904) using modern techniques in order to present new insights on this peculiar phenomenon. We extend its description to more general situations such as a three-layer fluid or a linearly stratified fluid in presence of a pycnocline, showing the robustness of dead-water phenomenon. We observe large amplitude nonlinear internal waves which are coupled to the boat dynamics, and we emphasize that the modeling of the wave-induced drag requires more analysis, taking into account nonlinear effects. Dedicated to Fridtj ¨ of Nansen born 150 yr ago (10 October 1861). In this paper, we present detailed experimental results on the dead-water phenomenon as shown in the video by (2008). The material is organized as fol- lows. In the remaining of this section, we briefly review the different studies of this phenomenon, either directly related to Ekman's work or only partially connected to it. Section 2 presents the experimental set-up. The case of a two-layer fluid is addressed in Sect. 3, followed by the case with a three-layer fluid in Sect. 4. The more realistic stratification with a pycnocline above a linearly stratified fluid is finally discussed in Sect. 5. Our conclusions, and suggestions for future work are presented in Sect. 6.
@cite_1 took advantage of the dead-water effect to study the effects of interfacial waves on wind induced surface waves. The study relates the statistical properties of surface waves to the currents induced by internal waves.
@cite_1
2025021278 1483773184 2074548003 2055609422
Internal waves were generated by a ship using the ‘dead water’ effect in areas where the water contains a strong near-surface density gradient. The effects of these internal waves on wind waves were examined. The principal measurements were slope statistics of the wind waves and horizontal currents in the internal waves. The effects on the wind waves were always observable from an aircraft; however, in measurements made only along the ship's track the effects of the internal waves were not always readily distinguishable from other factors that influence the wind wave field. By using statistical techniques, relationships have been established between the wind waves, the internal waves, and the wind velocity. The principal finding is that the wind wave field is relatively more sensitive to internal wave currents at low wind speeds than at high wind speeds. Numerical values are given. The effect of harmonic excitation on suspension bridges is examined as a first step towards the understanding of wind excitation upon such structures. The simplest asymmetric oscillator model is studied systematically and an unexpectedly rich dynamical structure is revealed. The methodology employed has been previously applied to models of rocking blocks and other free-standing rigid structures. Conditions for the existence of asymptotic periodic responses can be established; and a two part Poincare map is used to study the orbital stability of such solutions. Numerical results are reviewed which illustrate multiple coexistence of sub- and superharmonics over broad intervals of forcing and frequency. Observed dynamics include fold and flip bifurcations, (truncated and reversed) period doublings, and period adding. Numerical solutions are obtained via direct simulation, and as Poincare map fixed points under parameter continuation using the package AUT094. The results illustrate the possibility of the coexistence of 'dangerous' large amplitude (nonlinear) responses at the same point of parameter space as 'safe' (linear) solutions. Abstract Analytical methods for studying tsunami run-up become untenable when the tsunami wave runs on beaches. In this study, we use a finite-element procedure that includes the interaction between solid and fluid based on the potential flow theory to simulate the dynamics of tsunami wave induced by a thrust fault earthquake in order to investigate the effect of different beach slopes on the tsunami run-up. The simulated run-up shows significantly differences from that predicted by the analytical solution. The maximum run-up shows a negative linear relationship with the square root of the cotangent of the beach slope, similar to the result of the analytical solution using a solitary wave as the incident wave, but with different slopes and amplitudes. Fundamental physical phenomena such as laser-induced ionization, driven quantum tunneling, Faraday waves, Bogoliubov quasiparticle excitations, and the control of new states of matter rely on time-periodic driving of the system. A remarkable property of such driving is that it can induce the localized (bound) states to resonantly couple to the continuum. Therefore experiments that allow for enlightening and controlling the mechanisms underlying such coupling are of paramount importance. We implement such an experiment in a special optical fiber characterized by a dispersion oscillating along the propagation coordinate, which mimics “time”. The quasi-momentum associated with such periodic perturbation is responsible for the efficient coupling of energy from the localized wave-packets (solitons in anomalous dispersion and shock fronts in normal dispersion) sustained by the fiber nonlinearity, into free-running linear dispersive waves (continuum) at multiple resonant frequencies. Remarkably, the observed resonances can be explained by means of a unified approach, regardless of the fact that the localized state is a soliton-like pulse or a shock front.