General Weissenberg effect in free surface rheometry. I: Analytical considerations (Q761879)

For non-Newtonian fluids the so-called Weissenberg phenomenon can be used to determine viscometric functions. The problem is treated for a fluid of grade two. The steady free surface motion of a layered viscoelastic fluid driven by a vertical rotating rod and the free surface motion of a simple viscoelastic fluid between vertical eccentric rotating cylinders is solved by means of a domain perturbation approach. It is shown that concentric rotating cylinders present practical problems in measuring rheological properties via Weissenberg phenomenon due to the sensibility against small eccentricity.