Rheology drag force

Here, as usual, h and R denote the film thickness and radius, and R is the curvature radius of the spherical part of the particle surface. The dependence of the dimensionless drag coefficient, fy, on the distance h for different values of the ratio R/R is illustrated in Figure 5.49. The increase of R/R and the decrease of hlR may lead to an increase of the drag force,/j, by an order of magnitude. That is the reason the film between a deformed particle and a wall can be responsible for the major part of the energy dissipation. Moreover, the formation of doublets and flocks of droplets separated by liquid films seems to be of major importance for the rheological behavior of emulsions. 

Sedimentation (MICROSCOPIC PROCESS) motion of particles in viscous media due to gravitation or centrifugal fields (also settling), the term refers frequently to the state in which the field forces are counterbalanced by the drag force this state is almost instantaneously achieved in the case of colloidal suspensions the sedimentation of an individual particle depends on its size, the density contrast, the rheological fluid properties, the field strength, and the viscous interactions with other particles. 

The study of the flow properties of liquids is called rheology. The thickness or runniness of liquids is characterized by their viscosity. Consider a liquid between two parallel surfaces (with area A). The bottom surface is fixed and the top one moves at a constant velocity (v). A force (F) is applied to the top plate to keep it moving. The liquid is dragged along with the moving plate due to its viscosity with a velocity that is largest close to the top plate and decreases with the distance from it. This... 

As shown in Eqn. (6), the drag coefficient of a cylindrical fiber imder cross flow condition is a function of the Reynolds Number, which is generally expressed as Re = pUp,hd/p (i.e. the ratio of inertial force to viscous force). This definition holds true for Newtonian fluids, where shear stress < shear rate. However, the fluids that are often utilized in fiber sweep applications are non-Newtonian. Hence, the Reynolds Number must be redefined using the apparent viscosity function as Re = pUp>d/papp. The viscosity for Newtonian fluids is independent of the shear rate. However, for non-Newtonian fluids, the apparent viscosity varies with shear rate. Applying the Yield Power Law (YPL) rheology model, the apparent viscosity is expressed as ... 

What we are trying to do is examine how macromolecular structural features are altered by hydrodynamic forces and how this in turn affects the macroscopic rheology of the bulk fluid containing them. What macromolecular features are we trying to include At the least, we should examine the dynamics of a model that stretches and aligns like a random coil, has viscous drag interactions with the solvent, and has the springiness or entropy elasticity associated with macromolecular conformation. The tools we use to formulate our model will be those of statistical mechanics, but they should be readily comprehensible. 

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