3. Thin film flow: Hele-Shaw model

In many situations, injection-molded parts have a regular thickness that is smaller than other dimensions. They can be likened to a thin shell. From a CAD model of the part's surfaces, we need to extract an average surface with a thickness at each point. This is all that is needed for mechanical calculation, and we will see in paragraph 3.1 that we can move from a general problem with the three components of the velocity field and pressure as unknowns, to a problem with pressure as the only unknown. Even on a part where the overall thickness is smaller than the other dimensions, there may be regions where...