After More Than A Century, Physicists Explain Why Ships Get Stuck In “Dead-Water”

In 1893, Norwegian explorer Nansen described what must are a daunting phenomenon under the circumstances. His ship became trapped within the Nordenskiöld Archipelago off Siberia, barely ready to move, yet its engines seemed to be working normally and he wasn’t confronted by any known force. It’s taken 127 years, but physicists think they finally have a solution to how this phenomenon operates. it is also possible a rare appearance changed the course of history.

Nansen was little question not the primary to be trapped within the manner he described, but he did provide an in depth description that was recorded and believed. The phenomenon where a ship can make no headway without apparent reason, now referred to as dead-water, has been experienced repeatedly since.

From the beginning , Nansen recognized such entrapment occurred when a layer of water sat above more salty water, something common in fjords, particularly when cold meltwater from glaciers drain into the ocean . However, he didn’t understand why water layers created more drag than a well-mixed fluid.

Progress was made towards an evidence in 1904, when Swedish physicist Vagn Walfrid Ekman reproduced it within the laboratory, showing subsurface waves could occur at the purpose where the salty and water met. If these waves counteract the force provided by the ship’s propeller, they will bring it to a near complete halt.

In Proceedings of the National Academy of Sciences, a team at the Universite de Poitiers argue there are literally two phenomena which will cause dead-water: kinematic drag and dynamic resistance. They name the previous after Nansen (Nansen-wave making drag) and therefore the latter after Ekman (Ekman wave-making drag).

The authors used a rope to tow a model ship during a stratified canal and filmed the wake it produced with high-resolution cameras. They report the Ekman wave-making drag is amplified in enclosed spaces, leading past researchers (who also used narrow canals) to specialise in it. However, in additional open waters the Nansen-wave making drag quickly becomes dominant. While acknowledging more work is required to completely understand the character of the Nansen drag, the paper claims “that we’ve solved a quite 1-century mystery with reference to truth nature of the dead-water effect.”

Since its discovery, scientists and mariners have observed dead-water can occur wherever two layers of water with different densities fail to combine . One suitable location is that the Bay of Actium, Greece, where Antony and Cleopatra’s combined forces fought Octavian for control of the Roman world. Shakespeare, never the foremost reliable historian, attributed the result to a loss of nerve on Cleopatra’s part, but the researchers think it’s possible her ships got caught in dead-water, rendering her unable to return to Antony’s aid.

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