Meaning
Dynamic stalls occur when a material slows down in thin wall sections while choosing the path of least resistance through thicker regions. Avoiding flow hesitation is a priority for designers who must maintain continuous forward motion to prevent cold slugs or surface streaks. This issue disappears once all paths reach a similar resistance or the cavity is completely full.
Stagnation Probability
Cooling occurs rapidly in restricted gates or thin fins where flow hesitation is most likely to initiate a freeze up. Once the material stops moving, it requires immense pressure to restart the flow front, which usually creates a visible mark on the part surface.
Thin Geometry
Mechanical design must provide enough volume to allow the front to pass narrow gaps without dropping below critical velocity. If flow hesitation persists, the local temperature drops and the material solidifies before the rest of the cavity finishes filling.
Pressure Requirement
High speed injection helps push through potential stall points by reducing the time material spends in contact with cold walls. Sustained velocity ensures that flow hesitation does not lead to structural weaknesses at the join points of different flow streams. Continuous motion preserves thermal homogeneity inside the part.
