It commonly assumed that the flow is turbulent in the shot sleeve, runner system, and the duration of the filling of the cavity. Further, it also assumed that the model can reasonably represent the turbulence structure. These assumptions are examined herein. We examine the flow in 1) the shot sleeve, 2) the runner system, and 3) the mold cavity. Note, that even if the turbulence is exist in some regions it doesn't necessarily mean that all the flow field is turbulent.
Clearly, the flow in the substrate (a head the wave) is still
(almost zero velocity) and therefore the turbulence does not exist.
The number behind the wave is above the critical number (which is
in the range of 2000-3000).
The typical time for the wave to travel to the end of the shot sleeve are in the range
of a second.
At present there are no experiments on the flow behind the wave10.
To discuss the free interface as oppose to solid interface.
The estimation can be done by looking
at what is known in the literature about the
transition to turbulence in instantaneous starting pipe flow.
It has been shown [#!flow:wygy!#] that the flow changes from a laminar flow to
turbulent flow occurs in an abrupt meaner for a flow with supercritical number.
A typical velocity of the propagating front (transition between laminar to turbulent) is about at same velocity as the mean velocity of the flow. Hence, it is reasonable to assume that the turbulence is confined to a small zone in the wave front since the wave is traveling in a faster velocity than the mean velocity. should we insert a graph about the relation between the mean velocity and wave velocity in the shot sleeve Note that the thickness of the transition layer is a monotone increase function of time (traveling distance). The number in the shot sleeve based on the diameter is in a range of which means that the boundary layer has not developed much. Therefore, the flow can be assumed as almost a plug flow with the exception of the front region. what about the solid layer the skimmed to ``increase'' the plunger head and effects on the flow.