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Film casting application may require the knowledge of velocity distribution at the exit of a coat hanger die. The flow simulation in a coat hanger die is usually 3D, and the output at the exit of the computational domain is characterised by a non-uniform distribution. How can one transfer a velocity distribution at the exit of a 3D calculation domain into an inlet velocity boundary condition for a subsequent film casting simulation?
The most complete solution consists of defining several transverse lines along the exit boundary, and to perform the apropriate integration in order to extract a velocity data at each node for the subsequent film casting calculation.A faster solution consists of considering the velocity profile along one cross-section defined across the film width. This velocity distribution has to be corrected (scaled) in accordance with the actual flow rate. In other words, let Q and Q' be the actual flow rate out of the coat hanger die and the one resulting from the integration of the above velocity distribution. That velocity distribution has to be scaled with the ratio Q/Q'.
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