, (16)
where ξ L, η L, andζ L represent the local coordinates in the flowing plane and the thickness direction, respectively, as shown in Figure 2.ζ L = 0 corresponds to the screw surface andζ L = 1 to the barrel surface. The approximation ignoring the dependence of the pressure along the r -direction is described in the interpolation equation of Eq. (15). The origin ofθ and r differ between the twin screws and are set for each screw. In the TSE, the flow rate balance of the self-wiping portion cancels out, and the exchange of the flow rate between the twin screws is dominant.
To determine the pressure, the continuity equation (Eq. (1)) is used. According to the weighted residual method, Eq. (1) is discretized using Eq. (16) as a weight function, and the following discrete equation is obtained.