Tackling stiffness in process simulations by modifications to the model

9 Tackling stiffness in process simulations by modifications to the model 

It may seem paradoxical but it is nevertheless true that these two opposite courses of action have essentially the same effect on the stiffness ratio, 5. In the first case, the effect is to raise the value of the smallest 

In the second case, the smallest time constant disappears from consideration, so that the new stiffness ratio is given by the similar formula  

The stiffness ratio is reduced to 8, and the simplification has brought the additional bonus of reducing the number of states from 4 to 2. 

It goes without saying that care is always needed in applying either method above. The modeller needs to keep in mind at all times the ultimate purpose of his simulation, and he must be particularly careful if 

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