Modelling a Herschel Bulkley fluid with yield stress proportional to fluid pressure
 

I am currently trying to use OpenFOAM to simulate a open channel fluid flow case with the rheological property as follows:

Shear stress: yield stress (as a function of the fluid pressure) + K * (shear rate)^n

I note that the yield rate is inputted as a constant in OpenFOAM. Would that be possible for such rheological property be implemented in it? Thanks for helping.