The Newtonian Fluid Assumption Will Wreck Your CFD

Added: 2026-05-18

[00:00:00]The Navier-Stokes equations assume your fluid is Newtonian, meaning shear stress is proportional to velocity gradient.

[00:00:07]Water and air? Newtonian.

[00:00:10]But blood is shear thinning.

[00:00:12]Polymer melts are viscoelastic. Drilling muds, paints, slurries, even toothpaste, all non-Newtonian.

[00:00:20]Model any of these as Newtonian and your pressure drop can be 50% wrong.

[00:00:25]The velocity profile changes shape entirely. Newtonian pipe flow gives a parabolic profile. Shear thinning gives a blunted flat profile. Same geometry, same flow rate, completely different wall shear stress. Full breakdown in the video description.