Hi r/CFD,
My friend and I wrote a finite difference method solver for truncated power law fluids in Python. As some of you may have guessed, we started down this path after trying our hands at the CFDPython module by Prof. Lorena Barba.
The code runs great for shear-thickening fluids(power law index n>1) and for a Newtonian(n = 1) fluid. We tested it against known analytical solutions for Pressure Driven Channel flows, aka. Poiseuille flows, and the results are quite a good match.
The issue we are facing comes from shear-thinning fluids(n<1). We have only been able to run it successfully for n >=0.8 or a little below and that too for a rather coarse grid of 34 by 34, but it still was very close to the analytical solution. If we even increase the grid fineness to a 51 by 51 grid, the solution diverges. We need some help to get an idea where this instability is coming from and how to get rid of it. We are already using $dt = sigma * dx^(2) / nu$ to make sure our time step is small enough.
I am posting a link to the pdf where I discretize the Momentum equations to account for the variable viscosity. The momentum equations and their discretized forms.
I am also adding the link to my GitHub repository where you can get the Jupyter Notebook: FDM-NonNewt.
Pls help us out. We are quite a bit out of our depth here.
Saw a post showing the main features of non-newtonian fluid and I just thought, surely if this was all around you constantly you'd be invincible.
I don't even know if that is a thing but would a bulletproof vest with non-newtonian fluid inside work? Is it even possibile to make one?
See a non-newtonian fluid gets harder the more force is put to it - so i think it's theoretically possible to stop anything at the point od impact. If making a vest pit of this fluid it would best defense ever.
