Showing papers on "Herschel–Bulkley fluid published in 1982"
TL;DR: In this paper, the authors derived constitutive equations for the rapid shear flow of a mixture formed from granular solids in a fluid, where the stress state within the mixture is considered to be created by the momentum exchange between colliding solids.
Abstract: Constitutive equations are derived for the rapid shear flow of a mixture formed from granular solids in a fluid. The stress state within the mixture is considered to be created by the momentum exchange between colliding solids. The constitutive equations describe the shear and normal stresses as a function of the velocity gradient, friction and restitution coefficients of the solids, the fluid drag coefficient for the particle shape and the density of the solid and fluid constituents. The theoretical results agree well with the results obtained from numerous laboratory experiments.
77 citations
TL;DR: In this article, the run-up in an incompressible viscoelastic fluid contained between infinite parallel rigid plates which are simultaneously given equal parallel velocities is analyzed in terms of the disturbances which spread from the boundaries into the fluid and are reflected back and forth at the boundaries.
Abstract: The problem is discussed of run-up in an incompressible viscoelastic fluid contained between infinite parallel rigid plates which are simultaneously given equal parallel velocities. The problem is analyzed in terms of the disturbances which spread from the boundaries into the fluid and are reflected back and forth at the boundaries.
27 citations
TL;DR: In this paper, the authors used the laser Doppler technique to study flow characteristics in the vicinity of a reentrant corner for both Newtonian and elastic liquids, and found that near the reenterrant corner the flow characteristics are virtually independent of both fluid inertia and fluid elasticity.
Abstract: The Laser Doppler technique is used to study flow characteristics in the vicinity of a re-entrant corner for both Newtonian and elastic liquids. An L-shaped channel is chosen as the test geometry and a constant-viscosity Boger fluid as the elastic liquid. It is found that near the re-entrant corner the flow characteristics are virtually independent of both fluid inertia and fluid elasticity. The observed influence of fluid inertia is in agreement with existing theoretical predictions, whilst that of fluid elasticity is consistent with the elastic liquid behaving asymptotically like a Newtonian viscous liquid near the corner, suggesting the use of Oldroyd- (rather than Maxwell-) type models in future simulation studies. Numerical predictions for the Newtonian cases using finite-difference techniques are in satisfactory agreement with experiment, whilst those for an Oldroyd model are in qualitative agreement with experiment results for the Boger fluid.
27 citations
TL;DR: In this paper, the buckling process of a viscous fluid falling against a flat plate was modeled as a discontinuity, and a simple model was developed that indicates a loss of energy in the fluid buckling.
Abstract: A jet of viscous fluid falling against a flat plate may become unstable and buckle. The buckling process is postulated as a discontinuity, and a simple model is developed that indicates a loss of energy in the fluid buckling. Experimental values of the energy loss coefficient are presented.
17 citations
01 Jan 1982
TL;DR: The chapter focuses on the severe problems associated with attempts to describe a non-Newtonian fluid by means of a one-point measurement.
Abstract: This chapter focuses on viscosity and consistency. Unfortunately, the distinction between solid and fluid is not sharp and clear. The tendency of a fluid to flow easily or with difficulty has been a subject of great practical and intellectual importance to mankind for centuries. Laminar flow is streamline flow in a fluid. Turbulent flow is fluid flow in which the velocity varies erratically in magnitude and direction. The chapter highlights the difference between laminar flow and turbulent flow and also presents the factors affecting viscosity. There is usually an inverse relationship between viscosity and temperature and a direct nonlinear relationship between the concentration of a solute and viscosity at constant temperature. The chapter focuses on the severe problems associated with attempts to describe a non-Newtonian fluid by means of a one-point measurement. Under certain conditions it is possible to use a one-point measurement as a quality control technique for non-Newtonian fluids. In some highly standardized systems the change in viscous properties during processing moves in a reproducible manner along a predetermined path. A one-point measurement may satisfactorily determine the endpoint in such a system.
15 citations
TL;DR: In this paper, a nonlinear evaluation of all velocities and stresses represented in the Navier-Stokes equations and in the general stress tensor is presented, where the information required is essentially that for solution of linearized forms.
9 citations
01 Jan 1982
TL;DR: The chapter focuses on the severe problems associated with attempts to describe a non-Newtonian fluid by means of a one-point measurement.
Abstract: Publisher Summary
This chapter focuses on viscosity and consistency. Unfortunately, the distinction between solid and fluid is not sharp and clear. The tendency of a fluid to flow easily or with difficulty has been a subject of great practical and intellectual importance to mankind for centuries. Laminar flow is streamline flow in a fluid. Turbulent flow is fluid flow in which the velocity varies erratically in magnitude and direction. The chapter highlights the difference between laminar flow and turbulent flow and also presents the factors affecting viscosity. There is usually an inverse relationship between viscosity and temperature and a direct nonlinear relationship between the concentration of a solute and viscosity at constant temperature. The chapter focuses on the severe problems associated with attempts to describe a non-Newtonian fluid by means of a one-point measurement. Under certain conditions it is possible to use a one-point measurement as a quality control technique for non-Newtonian fluids. In some highly standardized systems the change in viscous properties during processing moves in a reproducible manner along a predetermined path. A one-point measurement may satisfactorily determine the endpoint in such a system.
5 citations
5 citations
TL;DR: In this article, the authors examined elastic and viscous effects during the study of extensional flow by the spinning technique, using the experiment in which a fluid is extruded from a nozzle (or spinneret) and elongated at constant rate by a rotating drum.
Abstract: This paper describes attempts to examine elastic and viscous effects during the study of extensional flow by the spinning technique. That is, using the experiment in which a fluid is extruded from a nozzle (or spinneret) and elongated at constant rate by a rotating drum [1–3]. This is different in several fundamental aspects from constant rate of strain or constant stress methods. They are only suitable for extremely viscous fluids such as molten polymers. The sample, preferably pre-relaxed, is held in a constant temperature bath and slowly elongated so that the stretch history of each part of the fluid is the same and an equilibrium stress [4] or rate of strain [5] is apparently attained. The most notable differences between the spinning method and these other methods is that in the former the rate of strain varies along the thread-line, stretch history is different although constant with time at any point from any other point and much higher rates of strain can generally be attained. As a result of this rapid rate of deformation. Vinogradow and co-workers [6] have recently stressed this aspect. In order to investigate the effect, the deformation behaviour of a Newtonian (in shear) fluid and a highly elastic solution have been examined by high speed photography and the results correlated with fluid profile measurements. In a supplementary set of experiments the effect of experimental variables was also examined. The influence of drum take-up speed and filament length on the axial stress/total strain curves was considered. Preliminary results on attempts to produce a master curve of such plots are also described.
4 citations
01 Mar 1982
TL;DR: A knowledge of surface shear stress is essential in determining the drag on submerged bodies, the energy losses in internal flows, local surface heat transfer rates in both internal and external flows, flow separation, cavitation, and unsteady flow behavior in rotating machinery as mentioned in this paper.
Abstract: : Fluid shear stress is one of the most important quantities characterizing the interaction between a flowing fluid and a solid body. A knowledge of surface shear stress is essential in determining the drag on submerged bodies, the energy losses in internal flows, local surface heat transfer rates in both internal and external flows, flow separation, cavitation, and unsteady flow behavior in rotating machinery. (Author)
3 citations
TL;DR: In this article, the dispersion of a soluble matter in a plastic fluid flowing through a tube and a channel has been analyzed by taking into account the variations of viscosity, diffusivity and yield stress.
Abstract: The dispersion of a soluble matter in a plastic fluid flowing through a tube and a channel has been analysed by taking into account the variations of viscosity, diffusivity and yield stress. It has been shown that in the special case of a Bingham fluid, surrounded by a peripheral layer of a Newtonian fluid, the effective dispersion coefficient with which the solute disperses across a plane moving with the mean speed of the flow decreases with the viscosity of the peripheral layer fluid but increases as the molecular diffusion coefficient of this layer decreases. Further, the effective dispersion coefficient also decreases as the yield stress of the Bingham fluid increases.
TL;DR: The effects of wall conductance on the steady state laminar flow of a newtonian fluid between two circular disks in relative motion were studied in this paper, where the fluid energy, momentum and continuity equations were coupled to the heat conduction equation for the disk to represent the problem.
TL;DR: In this paper, the effect of the presence of particles in flow of a viscoelastic fluid past convexly curves boundaries is studied by focussing attention on the limiting cases for which the principal curvatures of a wall segment are approximately equal and vastly different, respectively.
Abstract: The effect of the presence of particles in flow of a viscoelastic fluid past convexly curves boundaries is studied by focussing attention on the limiting cases for which the principal curvatures of a wall segment are approximately equal and vastly different, respectively. The corresponding sections are thus approximated by a spherical cap and a hyperbolic cylinder, respectively. The fluid is modelled as a second order fluid which requires a rheologically slow flow and/or a slightly elastic fluid. The analysis thus considers to some extent non-linear fluid properties and to some extent the complexities of possibly highly irregular walls (e.g. pores in a porous medium). According to our calculations a locally non-uniform distribution of matter is predicted, a non-uniformity which, depending upon the details of the system can get enhanced or diminished in the non-neutrally bouyant case.
01 Aug 1982
TL;DR: In this paper, the authors give a mathematical theory for a visco-elastic fluid exhibiting a hysterisis loop in the shear stress vs. shear rate plane, and use a local shock structure theory to pick out the admissible solutions in loading and unloading of the applied driving force.
Abstract: : This paper gives a mathematical theory for a visco-elastic fluid exhibiting a hysterisis loop in the shear stress vs. shear rate plane. The main rheological idea is to introduce a constitutive equation of rate type whose steady shear stress vs. shear rate locus is non-monotone. The main mathematical idea is to use a local shock structure theory to pick out the admissible solutions in loading and unloading of the applied driving force. (Author)
TL;DR: In this article, a hydrodynamic analysis was carried out for the propagation of shear vibrations in a layer of a nonlinear viscous power-law fluid, and the results showed that the shear propagation was independent of the density of the fluid.
Abstract: A hydrodynamic analysis was carried out for the propagation of shear vibrations in a layer of a nonlinear viscous “power-law” fluid.