[mister_mitch]

Hello,

The computation of non-newtonian viscosity seems to be inconsistent in units. For example, the Herschel-Bulkley model is set up to provide a kinematic viscosity below the yield stress threshold, while calculating a dynamic viscosity above the yield stress threshold:

nu = min ( nu0, (tau0 + k*gamma_dot^n)/(gamma_dot))

The output is specified as kinematic viscosity units, so clearly the equation is not correct if tau0 units are N/m^2 and gamma_dot units are s^-1.

https://www.openfoam.com/documentati...8C_source.html

The documentation I can find online seems to ignore this inconsistency when describing input parameters:
https://doc.cfd.direct/openfoam/user...sport-rheology

Unless I'm missing something, the solution should be providing the tau0 and k parameters already divided by density. If true, this is straight forward but lacking/unclear in the documentation.

I am hoping to confirm this with the community before I implement.

Cheers

[Martin_Sz]

There is the inconsistency in units for non-Newtonian viscosity calculations in the Herschel-Bulkley model. The inconsistency arises because the model expresses shear stress (tau) in units of N/m^2 (Pascals), while the shear rate (gamma_dot) is in units of s^-1 (reciprocal seconds).

More at
https://howtooansys.blogspot.com/202...es-in-non.html