Mold filling front region

The third region of flow near the front is of special interest. The important feature of this region is the fountain effect, which must be considered in modelling all types of mold filling. It is important not only for estimating the hydrodynamic flow pattern, but also because the deformation of the macromolecules near the front influences their orientation and the properties of the end product. 

Figure 4.59. Distribution of the relative velocity vector in the front region during mold filling.

Fig. 13.7 Schematic representation of the flow patterns during the filling of an end-gated rectangular mold whose width is much greater than its thickness, (a) Width direction flow fronts at various times, (b) Velocity profiles in the fully developed region, and schematic representation of the fountain effect in the front region.

We discuss some of these regions in detail below. In addition, we concern ourselves with the overall flow pattern during filling. Recall that the manner in which a mold is filled— that is, the location of the advancing melt front—affects the weld-line location and the orientation distribution and may be responsible for poor mold filling conditions. 

Many times transition region exists between the two, where air and resin coexist in varying coneentrations. Multiphase flow model ean be developed for the RTM flow simulation to ineorporate the effeets of both the phases. This model not only provides visuals of resin flow (flow front) in the mold but also depiets the transient behavior of flow of two phases (air and resin) where the initial air phase is replaced by the resin during mold fill proeess. 

A complete mold-filling computer simulations requires the calculations of the velocity and temperature profiles throughout the flow region, including the position and shape of the advancing melt front in the cavity. 

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