Video credit: Stephen Morris, University of Toronto
This video depicts an experiment where a stream of viscous, Newtonian fluid is dropped at a continuous rate onto the center of a moving belt. Through the progression of the video, the belt gradually slows, revealing several surprising stages of rhythms and shapes that the fluid falls into.
I am especially interested in this type of flow because viscous fluids behave in a way that is counterintuitive to me; these fluids seem to possess the mechanics of liquids as well as some properties of solids. In the experiment, it appears the fluid retains its cylindrical shape formed by the nozzle once it has contacted the surface for long enough that the incoming fluid stacks high on top of itself, sending an opposite force up into the downward-flowing column. This causes the column to buckle, and the section of fluid below the buckle is forced to fall onto the surface at an angle. This process happens with such reproducibility that the fluid falls in rhythmic patterns onto the belt. Because of how these fluid flows are at odds with my intuition, along with the way the light is cast through the fluid and how the fluid slowly spreads out on the surface, (as we can see on the right side of the frame) I find the flow of viscous fluids to be very aesthetically appealing.