Fluid-Mechanics

Cats use the dorsal surface of the tongue tip to entrain a liquid column, then close the jaw before gravity and pinch-off remove it. Reis and colleagues modelled the timing with inertia, gravity, a Froude number, and the tongue’s travel geometry. The relevant domestic-cat parameter is a modified Froude number near 0.4—not the simple Froude number near one.

Marc-Antoine Fardin won the 2017 Ig Nobel Prize for a playful application of rheological language to cats. The Deborah number De = τ/T is a standard timescale ratio for materials; assigning a cat a relaxation time is an analogy, not a rigorous material classification.