Question

What is Newtonian fluid? Is water a Newtonian fluid?

Short answer

Explain your answer. Answer: Yes, water is a Newtonian fluid. This is because it has a constant viscosity under varying shear rates or shear stress (at constant temperature and pressure) and exhibits a linear relationship between shear stress and shear rate, fulfilling the criteria for a Newtonian fluid.

Step-by-step solution

Define Newtonian Fluid

A Newtonian fluid is a fluid whose viscosity (resistance to flow) remains constant under different shear rates or shear stress. For a fluid to be classified as Newtonian, its shear stress, τ, should be directly proportional to its shear rate, γ. This can be mathematically expressed as: τ = μ * γ, where μ is the constant of proportionality, known as the dynamic viscosity.

Properties of Newtonian Fluids

Some common properties of Newtonian fluids are: 1. They have a constant viscosity, independent of shear rate or shear stress. 2. They demonstrate linear relationships between shear stress and shear rate. 3. Examples include water, air, and glycerol.

Comparing Water to Newtonian Fluids

Water exhibits the following characteristics: 1. Water has a constant viscosity under various shear rates or shear stress, at constant temperature and pressure. 2. The shear stress of water is directly proportional to its shear rate, following the equation τ = μ * γ (This is true for a wide range of temperature and pressure conditions). Considering these characteristics, we can conclude that water fulfills the criteria of Newtonian fluids.

Verdict

Water is a Newtonian fluid, as it has a constant viscosity and a linear relationship between shear stress and shear rate, fulfilling the criteria for a Newtonian fluid.