Dead water is the curious phenomenon when ships become sluggish and difficult to control in stratified waters in which a fresh layer sits on top of salty water. Such conditions often occur in arctic regions where water run off from melting glaciers or ice flows can float on top of denser salty water.
The effect was first noted by the Norwegian explorer Fridtjof Nansen in 1893 who noted that while his boat, Fram, could cruise easily at 7 knots in ordinary seas, in dead water she was unable to make 1.5 knots. “When caught in dead water Fram appeared to be held back, as if by some mysterious force,” he wrote.
Now Romain Vasseur and pals from the
They have even made a rather beautiful video showing how a toy boat is dramatically slowed by the effect.
The explanation is that movement of the boat causes a wave to form beneath the surface at the interface between the fresh and salty waters. This wave eventually catches up with the boat and breaks, dragging the boat to a halt.
What’ s fascinating is that while all this is going on beneath the water, the surface remains absolutely flat.
Presumably these guys have posted this paper in anticipation of the Gallery of Fluid Motion 2008 at the upcoming meeting of the APS Division of Fluid Dynamics in San Antonio in November.
Ref: arxiv.org/abs/0810.1702: Dead Waters: Large Amplitude Interfacial Waves Generated by a Boat in a Stratified Fluid
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2 responses to “The waves beneath the sea”
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Well, a neat stuff…;-) Believe it or not – but just the internal waves phenomena helped me to realize before few years, why the observable reality is formed just by density gradients of Aether density (concept of gradient driven reality). It’s totally invisible artifact – it manifests itself just by density gradient. By another way, whole the reality is gradient itself.
By AWT the space-time is always formed by these gradients, similar to water surface. The direction(s) normal to the space dimensions is time dimension(s): this model explains finally by trivial way, why the time direction has always “an arrow” (the gradient is always oriented).
The water surface model can even explain quantum uncertainty: the gradient can never be of infinite density, which enables all waves, which are spreading along it to have the character of both transversal, both longitudinal waves at the same moment (capillary – Rayleigh – Love – gravity waves).
It means, by using of water waves we are forced to observe the water surface both from inner, both from outer perspective at the same moment: this ambiguity bring a quantum uncertainty and fuzziness (many possible solutions “landscape”) into string and quantum gravity theories, because we are forced to observe the Universe both from inside, both from outside perspective as well. It means the same geometry, which makes our Universe real and observable, brings an uncertainty into its view.
The internal waves in dead water can cause even the ship wreckage, especially in unloaded state because of abrupt change of location of center of mass.