Theoretical and Experimental Studies of Selected Topics in the Rheology of Fluids

摘要

Theoretical and experimental studies of the consequences of short-term elastic response in liquids. Theoretical studies include analysis of the origins of viscosity in relaxing elasticity, the analysis of equations of motions according to type; e.g., hyperbolic or elliptic, with particular attention to problems of identification of physical phenomena and numerical analysis of flow associated with (1) change of type from subcritical to supercritical conditions in steady flow (transonic problems), (2) loss of well-posedness or short wave length instabilities in unsteady flow, (3) regularization of short wave instabilities with viscosity. A wave speed meter enables us to measure the effective shear modulus in liquids. The wave are developing an instrument to measure the speed of shear waves into a sheared media. We discovered delayed die swell and demonstrated experimentally that it is a critical phenomenon which appears to be like a hydraulic jump with speed greater than the shear. The fluidization of particles at finite, but even small Reynold numbers was dominated by local mechanisms associated with wakes and turning couples on long bodies. One sphere falls in the wake of another, they kiss, then tumble by the action of the turning couple which turns long bodies broadside onto the stream. These mechanisms lead to a stable arrays of spheres aligned perpendicular to the stream giving a physical foundation to the mathematical assumption that there are regimes of flow governed by one dimensional equations. A complete linearized analysis of the stability of water lubricated pipelining of viscous oils includes all of the main physical mechanisms underway, except gravity. The theory appears to be in good agreement with experiments. (jhd)