Experiments are conducted to study the vertical film width and downcomer gap effects on impingement upon the vertical flat wall simulating the core barrel in the APR 1400 (Advanced Power Reactor 1400 MWe). This work is being carried out in ALPHA (Accelerated Liquid Phase Hydrodynamics Apparatus) at the Seoul National University. The results are to be integrated into a system code THEOS (Thermomechanics Hydrodynamics Eutectics Online Simulator). At larger distances from stagnation to the injection nozzle, the gap effect falls off. The data suggest that, for impingement proximate to the stagnation point, the flow velocities can be computed by applying a turbulent correction factor to the laminar value calculated for velocities having the same pressure distribution as that present in the impingement region. To find the correction factor, one needs to obtain the liquid film thickness and breakup factors related to the turbulent flow. This is in contrast to the laminar flow, in which the liquid film thickness is uniform and the breakup is nonexistent. This work is particularly concerned with the liquid film thickness. Previous ALPHA experiments with varying nozzle diameters advocate that the correction factor is found to be a function of the injection speed rather than the Reynolds number. This paper documents on measurement of the radial liquid film thickness fluctuations and their point wise values at the same vertical height. It additionally reports on results of numerical calculation for the liquid film profiles.

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