Sculpted beach rock. Photograph: © SAF
Erosion caused by flowing water does not only smooth out objects, but can also form distinct shapes with sharp points and edges, a team of New York University researchers has found.
Their findings, which appear in the latest edition of the journal the Proceedings of the National Academy of Sciences (PNAS), reveal the unexpected ways that erosion can affect landscapes and artificial materials…
Original Study: “Sculpting of an erodible body by flowing water”, PNAS
“Erosion by flowing fluids carves striking landforms on Earth and also provides important clues to the past and present environments of other worlds. In these processes, solid boundaries both influence and are shaped by the surrounding fluid, but the emergence of morphology as a result of this interaction is not well understood. We study the coevolution of shape and flow in the context of erodible bodies molded from clay and immersed in a fast, unidirectional water flow. Although commonly viewed as a smoothing process, we find that erosion sculpts pointed and cornerlike features that persist as the solid shrinks. We explain these observations using flow visualization and a fluid mechanical model in which the surface shear stress dictates the rate of material removal. Experiments and simulations show that this interaction ultimately leads to self-similarly receding boundaries and a unique front surface characterized by nearly uniform shear stress. This tendency toward conformity of stress offers a principle for understanding erosion in more complex geometries and flows, such as those present in nature.”