The flow of thin films occurs in a variety of situations in the course of a loss of coolant accident. These can include flow in the annular downcomer during injection of emergency core cooling water, flow along the fuel rods in the course of the flowdown, and flow along the fuel rods as a result of upper head injection. This report summarizes research completed during the period November 1977 to October 1978 on related problems. (1) The flooding process, (2) motion and size of drops during upward annular flow, and (3) interfacial structure and momentum interactions for upward film flow. (1) Generalized solutions of the film flow equations are obtained which demonstrate the variety of possible mechanisms for flooding. The possibility that the physical condition which exists oscillates between one or more of these states is explored. (2) A new optical technique is presented for simultaneous measurement of drop size as well as radial and axial velocity in the presence of a liquid film. (3) Experimental data are reported for upward film flow in an air-water system. Included are entrainment and film rates, pressure drop and film structure data. The results are interpreted in terms of wall and interfacial shearmore » stress and friction factors.« less
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