# Non-Newtonain model using constitutive equation

I am reading the source code of Non-Newtonian solver. I can only find the HBP model parameters be called in function using the "apparent viscosity method" but cannot find in the "constitutive equation method". Could someone help me with this? Can I really use the "constitutive equation method"?

Thanks.

## Comments

Also I cannot find the function to calculate strain rate tensor in SPH formulation in function JSphCpu_NN_SPH. Any could help me find it?

hi

search: else if(tvisco==VISCO_ConstEq) {