Flow Behavior of Bingham Fluid in a Slot Die

It is necessary to provide well-designed geometries of flow channel in a slot die in order to achieve the uniform thickness of coated films for non-Newtonian fluids, especially for the fluids having nonnegligible yield stress. In this work we have studied the flow in the slot die using Bingham fluid. The present paper derives a model equation for the outflow distribution as functions of the yield stress and the geometries inside the die. Furthermore, we suggest a useful design method to predict an optimum geometry to guarantee the uniformity of outflow from die slot in Bingham fluid. The usefulness of the method is confirmed by an experiment conducted using a corresponding fluid.