. (14)

Finite element formulation

The 2.5D FEM element attached with the screw channel depth (H =R bR s) is employed to discretize the problem domain, as shown in Figure 2. Particular elements such as notch and pin mixing elements can be expressed directly by changing the wall thickness, H , attached to the element.
In the 2.5 D FEM element, the pressure and coordinates are interpolated using a shape function