Abstract
Abstract. 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 Fridtjöf Nansen born 150 yr ago (10 October 1861).
Highlights
The dead-water phenomenon is a well-known peculiar phenomenon, when a boat evolving on a two-layer fluid feels an extra drag due to waves being generated at the interface between the two layers whereas the free surface remains still
The wave field associated with the subcritical regime is analogous to the previous layered stratifications considered, the supercritical regime is different in nature since it consists mainly of radiated waves from turbulent perturbations in the pycnocline
This is similar to observations of the radiated wave field associated with an object moving at constant speed in a stratified fluid (Rottman et al, 2004)
Summary
The dead-water phenomenon is a well-known peculiar phenomenon, when a boat evolving on a two-layer fluid feels an extra drag due to waves being generated at the interface between the two layers whereas the free surface remains still. One finds reports of similar phenomena in the Latin literature when Tacitus described a flat sea on which one could not row a boat, North of Scotland and of Germany, in the Agricola (Tacitus, 98a) and in the Germania (Tacitus, 98b). This effect is only observed when the upper part of the fluid is composed of layers of different densities, due to variations in salt concentration or temperature. We present detailed experimental results on the dead-water phenomenon as shown in the video by Vasseur et al (2008).
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