The length of the area completely filled with a liquid is designated as s, the coordinate of the flow front in the central layer is x = 1, and the coordinate inside the peripheral layer is y = h(x), as can be seen in Fig.
Then p = 0 at x = l during the first stage of filling (the central layer is not completely filled) and [partial]p/[partial]x = 0 at x = l = L during the second stage (the central layer has been completely filled).
By differentiating Eq 9 and substituting the result into Eq 10 taking into account Eq 8, the following equation in pressure distribution along the central layer can be obtained:
y] is the initial (small) thickness of wetting of the relatively dense peripheral layer during movement of a liquid along the central layer.
Pressure distribution inside the central layer is determined as a solution of the above-formulated boundary problem and depends on time as a parameter.
An impregnating liquid (binder) enters a mold through the central layer.
0x] = permeability coefficient along the x-axis in the central layer.
time of reaching the back wall of a mold in the central layer.
y] = initial (small) width of wetting of the peripheral layers in the movement of a liquid through the central layer.