Static mixers do not need an introduction anymore since they now cover a wide range of industrial applications. However, despite these numerous uses, the principle of action or in simple words, the way they work, is still to demonstrate. This paper presents an example of useful information that can be extracted from simulations results. It is also discussed why local values of power and shear at various points in the mixer are the only true useful information in the understanding of a mixer＇s performance. It is then concluded that computational fluid dynamics software will tend to become essential for this investigation since experiments can hardly provide precise and versatile means of local measurements with such complex geometries as the ones povided by static mixers.