Resistance to shear; Newtonian fluids have shear stress proportional to velocity gradient.
Dynamic viscosity μ relates shear stress τ=μ du/dy (Newtonian fluids). Kinematic viscosity ν=μ/ρ. Liquid viscosity drops with temperature, gas viscosity rises. Non-Newtonian fluids (ketchup, blood, polymers) show shear-thinning or thickening.
Honey is thousands of times more viscous than water.
Newtonian fluids have a constant viscosity, which makes calculations straightforward, and many common fluids behave this way.
Resistance to shear; Newtonian fluids have shear stress proportional to velocity gradient.
Newtonian fluids have a constant viscosity, which makes calculations straightforward, and many common fluids behave this way.
Shear stress is proportional to the velocity gradient, so the viscosity is constant regardless of shear rate.
Paints, blood, polymer melts and many slurries have shear-dependent viscosity, so they need non-Newtonian models.
Typical applications include calculating the shear stress in a lubricant film between two plates, checking whether water or oil can be treated as Newtonian in a pipe model and designing a flow test for a fluid used in a process.
Study "Fluid properties" first (topic 45 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
Units Pa·s and m²/s. Water μ≈1 mPa·s. Oil SAE grades.
Honey is thousands of times more viscous than water.
The next topic is "Fluid statics", which builds directly on this one.
It is classed as Intermediate in Thermodynamics & Fluids (topic 46 of 105). It is an intermediate topic. Work through the beginner topics in Thermodynamics & Fluids first.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.