Temperature Dependence Of Fluid Viscosity Research Articles

Time Dependence of Viscosity of Alkali-Activated Fly Ash Based Geopolymer Mortar

FA was used as the raw material, and the net slurry of FA base Geopolymer was set as the control group to study the influence of sand content, gradation, reaction temperature and time on the time dependence of the viscosity of alkali-activated fly ash based geopolymer mortar. The experimental results show that the curing reaction of alkali-activated fly ash based geopolymer mortar was affected by the temperature dependence of fluid viscosity and the activation energy of the chemical reaction, which is relatively complex. This paper will divide the whole polymerization process into three stages to elaborate. The increase of sand cement ratio will increase the viscosity of FA base polymer mortar. If the sand is too coarse or too fine, the viscosity of FA base polymer mortar will increase significantly, and the fine sand has a greater impact on the viscosity of FA base polymer mortar than the coarse sand. Increasing temperature will significantly accelerate the reaction speed and increase the influence of chemical reaction activation energy on the viscosity of the system while the too high temperature will make the viscosity of the system decrease more significantly in the reaction. This study will reveal the intrinsic relationship between the viscosity of geopolymer and the reaction process, the reaction mechanism of the curing process so that the reaction stage can be represented by the viscosity state of the slurry.

Influence of Temperature and Pressure on Viscoelastic Fluid Flow in a Plane Channel

The hydrodynamics of a steady-state nonisothermal flow of a viscoelastic polymer medium in a plane channel and heat transfer in it under boundary conditions of the first kind have been investigated. Fluid flow with a low Reynolds number and a high Peclet number was investigated, which made it possible to neglect the gravity and inertial forces, as well as the longitudinal thermal conductivity of the medium. From the rheological viewpoint, the polymer melt represents a viscoelastic fluid; therefore the Phan-Thien–Tanner fluid model was used as a rheological model of the fluid, with viscosity depending on temperature and pressure. A high-viscosity medium was considered; therefore a dissipation term was included into the equation of the energy of its flow. With the use of the indicated rheological model the velocity profile of fluid flow was obtained in an explicit form from the equation of fluid motion. It has been established that the dependence of the fluid viscosity on temperature and pressure exerts a noticeable influence on the distribution of the Nusselt number and of bulk temperature of the fluid along the channel length. It is shown that account for the temperature dependence of fluid viscosity leads to a decrease in the role of energy dissipation of its flow in the process of flow heating and that, conversely, the dependence of the fluid viscosity on pressure considerably enhances the dissipation effect. The problem has been solved numerically by the method of finite differences.

Effects of fluid influx, fluid viscosity, and fluid density on fluid migration in the mantle wedge and their implications for hydrous melting

The migration pathways of hydrous fluids in the mantle wedge are influenced by the compaction of the porous mantle matrix, which depends on the matrix permeability, fluid viscosity, and fluid density. Experimental studies show that when fluids are interconnected, the permeability depends on mineral grain size and porosity, the latter of which depends on the amount of fluids introduced into the system (fluid influx). Here, we investigate the role of fluid influx, fluid viscosity, and fluid density in controlling fluid migration in the mantle wedge, using a 2-D numerical model accounting for the effects of grain-size variation and matrix compaction. Our models predict that fluid influx and fluid viscosity are key controls on fluid pathways, while fluid density plays a secondary role. Temperature dependence of fluid viscosity promotes downdip drag of fluids at the base of the forearc mantle toward the subarc region. High fluid influx at postarc depths promotes updip flow near the base of the mantle wedge, guiding the fluids arcward. The model that is applied to northern Cascadia predicts upward fluid migration focused beneath the arc but cannot explain high electrical conductivity observed slightly west of the upward fluid migration. We estimate the amount of hydrous melt that can be produced in the mantle wedge using calculated fluid distributions. Up to a few percent partial melting is predicted in a relatively small region in the core part of the subarc mantle wedge in most subduction settings, including northern Cascadia, and beneath the backarc in old-slab subduction zones.

Heat Transfer in Hydromagnetic Fluid Flow: Study of Temperature Dependence of Fluid Viscosity

Heat Transfer in Hydromagnetic Fluid Flow: Study of Temperature Dependence of Fluid Viscosity

Theoretical investigation of scaling effects from macro-to-microscale convection due to variations in incompressible fluid properties

We re-examine the governing continuum-based conservation equations for single-phase laminar forced convection of liquids, incorporating temperature dependence of fluid viscosity and thermal conductivity. The effects of property variations become highly significant from macro-to-microscale convection. Further, the effects of property variations along the flow become more significant relative to property variations over the cross section; thereby necessitating consideration of additional convection mechanisms at the microscale, in addition to mechanisms known at the macroscale. The same Brinkman number that determines convection with viscous dissipation, also determines convection with variations in fluid properties; but now the significance in convection increases with decreasing Brinkman number.

Cooling of a viscoelastic film during unsteady extrusion from an annular die

The unsteady extrusion of a viscoelastic film from an annular and axisymmetric die is examined. External, elastic, viscous and inertia forces deform the film, which is simultaneously cooled via forced convection to the ambient air. This moving boundary problem is solved by mapping the liquid/air interfaces onto fixed ones and by employing a regular perturbation expansion for all the dependent variables. The ratio of the film thickness to its inner radius at the exit of the die is used as the small parameter in the perturbation expansion. The fluid mechanical aspects of the process depend on the Stokes, Deborah, Reynolds, and Capillary numbers. The heat transfer in the film and to the environment gives rise to four additional dimensionless groups: the Peclet, Biot and Brinkman numbers and the activation energy, which determines the temperature dependence of fluid viscosity and elasticity. A variable heat transfer coefficient is also considered. For typical fluid properties and process conditions, the Peclet number is very large. In this case it is the ratio of the Biot to the Peclet number, the Stanton number, which arises in the energy conservation equation. It is shown that film cooling becomes important when the Stanton number and/or the activation energy are in the high-end of their typical values. In such cases, the cooling of the parison leads to a more uniform flow and shape for the film. The influence on the process of a variable heat transfer coefficient and the Brinkman number is small.

On the instability of hypersonic flow past a flat plate

The instability of hypersonic boundary-layer flow over a flat plate is considered. The viscosity of the fluid is taken to be governed by Sutherland's formula, which gives a more accurate representation of the temperature dependence of fluid viscosity at hypersonic speeds than Chapman's approximate linear law. A Prandtl number of unity is assumed. Attention is focused on inviscid instability modes of viscous hypersonic boundary layers. One such mode, the ‘vorticity’ mode, is thought to be the fastest growing disturbance at high Mach numbers, M [Gt ] 1; in particular it is believed to have an asymptotically larger growth rate than any viscous instability. As a starting point we investigate the instability of the hypersonic boundary layer which exists far downstream from the leading edge of the plate. In this regime the shock that is attached to the leading edge of the plate plays no role, so that the basic boundary layer is non-interactive. It is shown that the vorticity mode of instability operates on a different lengthscale from that obtained if a Chapman viscosity law is assumed. In particular, we find that the growth rate predicted by a linear viscosity law overestimates the size of the growth rate by O((log M)½). Next, the development of the vorticity mode as the wavenumber decreases is described. It is shown, inter alia, that when the wavenumber is reduced to O(M-3/2) from the O(1) initial, ‘vorticity-mode’ scaling, ‘acoustic’ modes emerge.Finally, the inviscid instability of the boundary layer near the leading-edge interaction zone is discussed. Particular attention is focused on the strong-interaction zone which occurs sufficiently close to the leading edge. We find that the vorticity mode in this regime is again unstable. The fastest growing mode is centred in the adjustment layer at the edge of the boundary layer where the temperature changes from its large, O(M2). value in the viscous boundary layer, to its O(1) free-stream value. The existence of the shock indirectly, but significantly, influences the instability problem by modifying the basic flow structure in this layer.