Ostwald-de Waele power-law

A highly concentrated suspension of flocculated kaolin in water behaves as a pseudo-homogeneous fluid with shear-thinning characteristics which can be represented approximately by the Ostwald-de Waele power law, with an index of 0.15. It is found that, if air is injected into the suspension when in laminar flow, the pressure gradient may be reduced even though the flowrate of suspension is kept constant, Explain how this is possible in slug flow and estimate the possible reduction in pressure gradient for equal volumetric flowrates of suspension and air. 

To the same family of curves belong pseudoplastic materials. These fluids show a decrease in apparent viscosity with an increase in the rate of shear and are typical of the majority of non-Newtonian liquid food products. The way most often used to describe the properties of these materials is an empirical Ostwald-de Waele power law equation ... 

Newtonian Ostwalde-de Waele power-law fluid Shvedov-Bingham... 

The results obtained during the Couette flow of aqueous solutions of polyethylene oxide and other water-soluble polymers appear especially promising since they showed an appreciable increase in the current noise level with shear rate. The current noise level depended also on the viscosity (molecular weight) of the solution. A slight increase of thermal noise was recorded also. The pseudoplasticity exponent n in the Ostwald-de Waele power law formula and the exponent a in the l/f -frequency distribution of the current noise were interrelated. This relation appeared to be generally valid. 

The rheological profile obtained from the viscometer is fitted with Ostwald-de Waele Power law model. This mathematical model has been reported to have lowest standard error. The power law mathematical model is given by ... 

An important quantity for the interaction between polymer solutions and the turbulent flow is the retaxation-time behaviour of the polymer solution. The experimental results of MICHELE [l5] demonstrate that in the upper (Ostwald-de-Waele-)power-law region the measured relaxation times from start up tests are identical with those calculated from the measurements of the first normal-stress difference and the shear stress with a Maxwell model. Therefore effective relaxation times A were calculated by... 

It is obvious that the simple non-Newtonians cannot be treated by Newton s Law of Viscosity. As such, other approaches must be taken which lead to rheological constitutive equations that can be quite complicated. The simplest ones are equation (2-8) (the apparent viscosity expression) and the Ostwald-De Waele Power Law... 

Obtain the velocity profile and volumetric flow rate for a non-Newtonian fluid obeying the Ostwald-De Waele Power Law in a circular tube. 

A non-Newtonian fluid described by the Ostwald-De Waele power law is contained between two concentric cylinders [outer of radius R moves with an angular velocity of inner cylinder of radius (R — b) is stationary]. Find the temperature profile in the annular space between the two cylinders if the inner cylinder is at T and the outer one is at T2. 

The modified Carreau model and the modified Ellis model are limited to relatively low values of shear rates and shear stresses, reflectively, whereas the modified Ostwald-de Waele power-law model is applicable to the higher-shear-rate region where the data points fall in a straight line on the log-log plot of -q X MFI versus y/MFL... 

Tables 6.S-6.8 list the model constants and the range of applicability based on the modified Carreau model, the modified Ellis model, the modified Ostwald-de Waele power-law model, and the General Rheological [11] model, respectively, for the master rheograms of most of the polymers discussed in Chapter 4.

Similarly, the other models may be written as follows Modified Ostwald-de Waele Power-Law Model ... 

For homopolymers, the Ostwald-De Waele power-law relationship maybe extended to include temperature dependence as (Han 2007) ... 

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