The present work is concerned with an experimental study of the apparent viscosity of sand used i... more The present work is concerned with an experimental study of the apparent viscosity of sand used in typical foundries. The viscosity of fluidized foundry sand was measured at both Poiseuille (capillary viscometer) and Couette (rotational viscometer) flows. Capillary tube viscometers are obviously to be preferred when the data are to be used for pipe flow problems, and rotational viscometers, which subject the material under test to a precise and uniform rate of shear, have definite advantages in the analysis of complex system, such as in sand molding processes. Data obtained with the Brookfield viscometer show that as either the shear rate or the bed voidage factor (air flow rate) increases, the apparent viscosity decreases. In addition, the measured viscosities are only slightly affected by changes in particle diameter for the diameters investigated. The capillary viscometer data show that the apparent viscosity does not depend on the overall pressure drop at given capillary tube. However the apparent viscosity measurements were significantly affected by the tube length to inner diameter ratio due to the dominant influence of entrance region energy losses.
The displacement of Newtonian fluids by non-Newtonian fluids in a horizontal cylindrical tube has... more The displacement of Newtonian fluids by non-Newtonian fluids in a horizontal cylindrical tube has been investigated both theoretically and experimentally. Theoretical expressions for the breakthrough time, a function of the constitutive constants of the fluids and of the flow parameters and geometry, are derived when the displacing fluids are either of the inelastic viscous or viscoelastic type. The dynamics of the displacement process is studied experimentally using the photometry method and an oil field spacer fluid and glycerol/water mixtures as the displacing and displaced fluids, respectively. The ratio of the zero shear viscosities of the displacing and displaced fluids plays a crucial role both when the displacing fluid is characterized by a viscoelastic and viscoinelastic structure. The density ratio of the displacing and displaced fluids is close to one in our experiments as it may be in most field operations. We show that characterization of this type of spacer fluid by a viscoelastic model at moderate pressure gradients will not lead to good predictions of the breakthrough time when the viscosity of the displaced crude is much smaller than that of the displacing spacer fluid, that is, for high values of the zero shear viscosity ratios which may be desirable for high efficiency displacement processes.
The steady plane, laminar flow of a Newtonian and a viscoelastic fluid in a channel with rectangu... more The steady plane, laminar flow of a Newtonian and a viscoelastic fluid in a channel with rectangular blind cavity on one wall was studied theoretically and experimentally. The data show that the drag coefficient versus Reynolds number first falls and then increases with the coefficient of the reversible elastic strain.
The flow of inelastic and viscoelastic fluids in two porous media of different permeabilities and... more The flow of inelastic and viscoelastic fluids in two porous media of different permeabilities and same priority arranged in series has been investigated both theoretically and experimentally. The fluids are an oil field spacer fluid and aqueous solutions of polyacrylamide. The porous medium is represented by a cylindrical tube randomly packed with glass spheres. Expressions for the friction factor and the resistance coefficient as a function of the Reynolds number have been developed both for shear thinning and viscoelastic fluids based on the linear fluidity and eight constant Oldroyd models, respectively. The authors show that the energy loss is higher if the viscoelastic fluid flows first through the porous medium with the smaller permeability rather than through the section of the cylinder with the larger permeability. This effect is not observed for Newtonian and shear thinning fluids flowing through the same configuration. Energy requirements for the same volume flow rate are much higher than a Newtonian fluid of the same zero shear viscosity as the polymeric solution. Energy loss increases with increasing Reynolds number at a fixed concentration. At a fixed Reynolds number, the loss is a strong function of the concentration and increases with increasing concentration. The behavior ofmore » all fluids is predicted qualitatively except the difference in energy requirements.« less
The preliminary results of the mathematical modeling of the stability of a mushy state in magneti... more The preliminary results of the mathematical modeling of the stability of a mushy state in magnetic field are presented. The problem is applied to the electrical conductivity measurements on liquid metals using rotational technique.
The present work is concerned with an experimental study of the apparent viscosity of sand used i... more The present work is concerned with an experimental study of the apparent viscosity of sand used in typical foundries. The viscosity of fluidized foundry sand was measured at both Poiseuille (capillary viscometer) and Couette (rotational viscometer) flows. Capillary tube viscometers are obviously to be preferred when the data are to be used for pipe flow problems, and rotational viscometers, which subject the material under test to a precise and uniform rate of shear, have definite advantages in the analysis of complex system, such as in sand molding processes. Data obtained with the Brookfield viscometer show that as either the shear rate or the bed voidage factor (air flow rate) increases, the apparent viscosity decreases. In addition, the measured viscosities are only slightly affected by changes in particle diameter for the diameters investigated. The capillary viscometer data show that the apparent viscosity does not depend on the overall pressure drop at given capillary tube. However the apparent viscosity measurements were significantly affected by the tube length to inner diameter ratio due to the dominant influence of entrance region energy losses.
The displacement of Newtonian fluids by non-Newtonian fluids in a horizontal cylindrical tube has... more The displacement of Newtonian fluids by non-Newtonian fluids in a horizontal cylindrical tube has been investigated both theoretically and experimentally. Theoretical expressions for the breakthrough time, a function of the constitutive constants of the fluids and of the flow parameters and geometry, are derived when the displacing fluids are either of the inelastic viscous or viscoelastic type. The dynamics of the displacement process is studied experimentally using the photometry method and an oil field spacer fluid and glycerol/water mixtures as the displacing and displaced fluids, respectively. The ratio of the zero shear viscosities of the displacing and displaced fluids plays a crucial role both when the displacing fluid is characterized by a viscoelastic and viscoinelastic structure. The density ratio of the displacing and displaced fluids is close to one in our experiments as it may be in most field operations. We show that characterization of this type of spacer fluid by a viscoelastic model at moderate pressure gradients will not lead to good predictions of the breakthrough time when the viscosity of the displaced crude is much smaller than that of the displacing spacer fluid, that is, for high values of the zero shear viscosity ratios which may be desirable for high efficiency displacement processes.
The steady plane, laminar flow of a Newtonian and a viscoelastic fluid in a channel with rectangu... more The steady plane, laminar flow of a Newtonian and a viscoelastic fluid in a channel with rectangular blind cavity on one wall was studied theoretically and experimentally. The data show that the drag coefficient versus Reynolds number first falls and then increases with the coefficient of the reversible elastic strain.
The flow of inelastic and viscoelastic fluids in two porous media of different permeabilities and... more The flow of inelastic and viscoelastic fluids in two porous media of different permeabilities and same priority arranged in series has been investigated both theoretically and experimentally. The fluids are an oil field spacer fluid and aqueous solutions of polyacrylamide. The porous medium is represented by a cylindrical tube randomly packed with glass spheres. Expressions for the friction factor and the resistance coefficient as a function of the Reynolds number have been developed both for shear thinning and viscoelastic fluids based on the linear fluidity and eight constant Oldroyd models, respectively. The authors show that the energy loss is higher if the viscoelastic fluid flows first through the porous medium with the smaller permeability rather than through the section of the cylinder with the larger permeability. This effect is not observed for Newtonian and shear thinning fluids flowing through the same configuration. Energy requirements for the same volume flow rate are much higher than a Newtonian fluid of the same zero shear viscosity as the polymeric solution. Energy loss increases with increasing Reynolds number at a fixed concentration. At a fixed Reynolds number, the loss is a strong function of the concentration and increases with increasing concentration. The behavior ofmore » all fluids is predicted qualitatively except the difference in energy requirements.« less
The preliminary results of the mathematical modeling of the stability of a mushy state in magneti... more The preliminary results of the mathematical modeling of the stability of a mushy state in magnetic field are presented. The problem is applied to the electrical conductivity measurements on liquid metals using rotational technique.
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