Shear thinning worked example

Problem 6.3(a) (Worked Example) At what critical shear rate do you expect the onset of shear thinning in a 40% (by volume) suspension of hard spheres of radius 1 tim in water at room temperature (Hint use the data of Fig, 6-4, plus scaling principles.)... 

Problem 6.7(a) (Worked Example) Estimate the first normal stress difference Ni for a suspension of long, thin particles (approximated as spheroids) with p = 100 and L = 0.1/ m, if the solvent viscosity is 1 P, the shear rate y is 100 sec, and the particle concentration is 0 = 0.001, which is in the dilute regime. 

The final means for carbohydrate taste interactions to occur is through their effect on mass transfer in the mouth. While hydrocolloids are quite tasteless, they are often used to contribute viscosity to a food and thereby reduce mass transfer from the food to the taste receptors. Pangbom et al. [29] reported that a sample viscosity greater than 12-16 cP results in a significant reduction in sweemess. Work by Vaisey et al. [30] showed that not only is intrinsic viscosity important but the overall rheological properties of the food. For example, hydrocoUoids that readily shear thin (e.g., Gelan gum) reduce sweetness less than those hydrocolloids that do not shear thin. 

The discussion in this section is confined to the behaviour of inelastic, shear thinning fluids in porous media. Xanthan biopolymer is taken as the main example, and virtually all of the papers on the flow of this polymer through porous media are related to its importance in oil recovery. Work on the in-situ rheology of xanthan has been reported for flow through sandstone cores, sandpacks, bead packs and other unconsolidated material. 

Naturally formed polymer products have the advantage over petrochemical products that they are renewable and often bio-degradable. For example, it has been shown that oils extracted from vegetables can be polymerized into polymers that can be used to make products. In addition, it has been shown that proteins can be extracted from vegetables, such as soybeans or corn, and denatured by solvents and shear thinning to produce polymer substrates [1]. The latter method of making natural polymers is the focus of this work and thus a more detailed background is provided. 

Implicit in this model is the assumption that molecular diffusivity and Henry s Law constant are directly and inversely proportional, respectively, to the gas flux across the atmosphere-water interface. Molecular diffusion coefficients typically range from 1 x 10-5 to 4 x 10-5 cm2 s-1 and typically increase with temperature and decreasing molecular weight (table 5.3). Other factors such as thickness of the thin layer and wind also have important effects on gas flux. For example, wind creates shear that results in a decrease in the thickness of the thin layer. The sea surface microlayer has been shown to consist of films 50-100 pm in thickness (Libes, 1992). Other work has referred to this layer as the mass boundary layer (MBL) where a similar range of film thicknesses has been... 

A system based on the CGS method offers several advantages for curvature measurements for thin films and layered solids. The measurement provides all the normal and shear components of the curvature tensor. It also provides full field information from the entire area of the substrate—film system. The measurement area could also be scaled as necessary from a few millimeters to hundreds of millimeters so that large wafers and flat panels with thin film deposits are tested. The method involves non-contact measurements which are carried out with an adjustable working distance, and performed in-situ and in real time as, for example, during thermal cycling. 

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