Turbulence and Herschel-Bulkley Model
 

I wanted to run a model using either a realizable k-epsilon or an SST turbulence model with the material viscosity defined using a Herschel-Bulkley model. However, once I've defined the turbulence model it switches the material viscosity to constant and the Herschel-Bulkley model is no longer available. Why is this?