An approach to the calculation of drag and fall or rise velocity of a solid and Newtonian fluid spheres in viscoplastic fluids and to the calculation of pressure drop in viscoplastic fluid flow through random fixed beds of particles is suggested. It is based on the application of the modified Rabinowitsch-Mooney equations together with corresponding relations for consistency variables and on the application of the relationship of Hadamard-Rybczynski valid for both the fluid and solid spheres. The solution is concretized for Bingham, Casson and Robertson-Stiff flow models, and in the case of fixed beds also for Herschel-Bulkley flow model.
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A theoretical aspect of lubrication of a curvilinear thrust bearing by conducting and magnetic viscoelastic fluids is considered. The effects of centrifugal (rotational) inertia forces on the pressure distribution in the presence of a magnetic field, normal to the bearing surfaces, are examined. The examples of flows in the bearings modelled by two disks and two concentric spheres are discussed. The obtained results show that the fluid inertia forces and magnetic field have significant effects on the pressure distribution.
The steady laminar flow of molten polymer modelled by viscoplastic fluid is considered, through a narrow space between two fixed surfaces of revolution. The problem is described by boundary layer equations. Using the method of averaged inertia one obtains the formulae expressing the pressure distribution. Generally, the flow of viscoplastic fluids given by the nonlinear model of Shulman is considered. The flows of polymers modelled by the viscoplastic fluids of Vočadlo, Herschel - Bulkley, Ostwald - de Waele and Newtonian are discussed in detail. Numerical examples of pressure distributions in the clearance between parallel disks and concentric spherical surfaces are presented.
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