Non-Newtonian Yield Stress Models

Some slurries require a minimum stress, Tj, before flow initiates. This minimum stress is known as the yield stress for the slurry. For example, freshly poured concrete does not flow along an inclined surface until a specific angle relative to the horizontal is reached. Other examples of slurries which exhibit a )deld stress include paints and printing inks. In these cases, there is a critical film thickness below which these slurries will not flow under the action of gravity. 

In the Herschel-Bulkley model, the yield stress, consistency index k, and the flow behaviour index n characterize the slurry. 

the Bingham plastic model is a special case of the Hershel-Bulkley model when = 1. Slurries following the Bingham plastic model will be discussed in more detail in the next section. 

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