Question:
Newtonian flow is characterized by
Newtonian flow is characterized by
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In rheology, fluids are classified by how their viscosity (resistance to flow) behaves when you stir or push them harder (i.e., change the shear rate). Newtonian fluids are the simplest case.
Updated On: Jun 24, 2026
- Viscosity increases with shear rate
- Viscosity decreases with shear rate
- Constant viscosity irrespective of shear rate
- Presence of yield value
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The Correct Option is C
Solution and Explanation
Concept:
In rheology, fluids are classified by how their viscosity (resistance to flow) behaves when you stir or push them harder (i.e., change the shear rate). Newtonian fluids are the simplest case.
Step 1: For a Newtonian fluid, the shear stress is directly proportional to the shear rate, and the proportionality constant is the viscosity.
Step 2: Because that ratio stays fixed, the viscosity remains constant no matter how fast you shear the fluid. Water and simple oils behave this way.
Why the others are wrong: Viscosity rising with shear rate describes dilatant (shear-thickening) fluids; viscosity falling with shear rate describes pseudoplastic (shear-thinning) fluids; a yield value (a minimum stress needed before flow begins) is the hallmark of plastic/Bingham systems. None of these are Newtonian. A Newtonian fluid simply keeps a constant viscosity.
Answer: Option (3) — Constant viscosity irrespective of shear rate.
In rheology, fluids are classified by how their viscosity (resistance to flow) behaves when you stir or push them harder (i.e., change the shear rate). Newtonian fluids are the simplest case.
Step 1: For a Newtonian fluid, the shear stress is directly proportional to the shear rate, and the proportionality constant is the viscosity.
Step 2: Because that ratio stays fixed, the viscosity remains constant no matter how fast you shear the fluid. Water and simple oils behave this way.
Why the others are wrong: Viscosity rising with shear rate describes dilatant (shear-thickening) fluids; viscosity falling with shear rate describes pseudoplastic (shear-thinning) fluids; a yield value (a minimum stress needed before flow begins) is the hallmark of plastic/Bingham systems. None of these are Newtonian. A Newtonian fluid simply keeps a constant viscosity.
Answer: Option (3) — Constant viscosity irrespective of shear rate.
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