A preliminary investigation was conducted to evaluate the slosh-damping effectiveness of positive-expulsion bags and diaphragms in a 9.5-inch-diameter spherical tank. The hags were installed with the liquid outside and the ullage inside. The maximum slosh forces that occurred at the first natural mode were approximately 50 to 60 percent lower than the forces with the unrestricted liquid. The bags and diaphragms eliminated a lower force peak at the second natural mode. Damping ratios (or logarithmic decrements) as high as 0.28 were measured and liquid swirl, which was observed at the natural modes for the unre-stricted liquid, was completely suppressed.
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