Question

Please make sure to display your thought process? It is imperative to be able to follow how the answer was deduced. Please be as thorough as possible. Please address all parts as they are critical to answering this question correctly:

1) What are the differences between Newtonian fluids and powerlaw fluids?

2) Describe fluids that exhibit chemorheological behavior.

Answer 1

1. Fluids that are following the new law of viscosities called the Newtonian fluids.

according to newton law of viscosities shear stress is proportional to the shear rate. where the proportionality constant is the viscosity of the fluid. The fluids which don't follow the Newton law of viscosity called non-Newtonian fluids. They follow a modified version of the newton law of viscosity.

A power-law fluid, or the Ostwald–de Waele relationship, is a type of generalized Newtonian fluid (time-independent Non-Newtonian fluid) for which the shear stress, τ, is given by:

where:

• K is the flow consistency index (SI units Pa sⁿ),
• ∂u/∂y is the shear rate or the velocity gradient perpendicular to the plane of shear (SI unit s⁻¹), and
• n is the flow behavior index (dimensionless).

2.

Whipped cream with 25% (low‐fat) and 35% (high‐fat) at varying concentrations of RBP from 1% to 3% was used. The samples were conditioned at 10°C for 2 min, and then, the shear rate was increased from 0.1 to 1,000 s⁻¹. Then, the experimental flow curve was plotted in shear stress (τ) versus shear rate (γ). The apparent shear viscosity (η_a) was determined as a function of increasing shear rate in the ramp‐up mode. The rheological behavior of cream with varying amount of RBP was fitted by using different models such as power‐law (Equation 1), Bingham (Equation 2), and Casson (Equation 3) as follows:

(1)

(2)

(3)

where τ₀ is the yield stress, η is the apparent viscosity, k is the consistency index, and n is the power‐law index. The correlation coefficient (R²) was determined to show the goodness of the model.

source: https://onlinelibrary.wiley.com/doi/full/10.1002/fsn3.939