Dead Water

The Norwegian explorer Fridtjof Nansen almost became the first person to reach the North Pole on his famous 1893-1896 Fram expedition. Though they missed the pole, the expedition was a huge scientific success.

One effect in particular stood out to Nansen however. His state-of-the-art ship Fram was mysteriously slowed several times on the voyage. He noticed that it only occurred when a layer of fresh water rested on top of salty seawater. He named this strange and powerful drag the dead water effect. His friend and researcher Wilhelm Bjerknes had his PhD student, Vagn Ekman work on it. Several years and hundreds of experiments later, Ekman concluded that dead water resulted from the generation of internal waves within density stratified waters.

More than a century later, we now have the computational techniques to directly simulate this effect. In the header video I simulate dead water using the volume-penalty method in Dedalus. On top I plot the density of the fluid, which gets lighter toward the top. The bottom plots the vorticity, essentially a measure of the rotation of the fluid. Being able to visualise this phenomenon illustrates the variability of the drag, and the striking occurrence of vortices, which seem highly correlated to the peak of the effect.

Eric W. Hester
Eric W. Hester
Hedrick Assistant Adjunct Professor

My research interests include applied mathematics, computational fluid dynamics, singular perturbation theory, the Dedalus PDE solver, and industrial, geophysical and astrophysical fluid dynamics.