Two-phase flow exists in many shell-and-tube heat exchangers and power generation components. The flowing fluid is a source of energy that can induce small-amplitude subcritical oscillations and large-amplitude dynamic instabilities. In fact, many practical system components have experienced excessive flow-induced vibrations. To prevent unacceptable flow-induced vibration, we must understand excitation mechanisms, develop analytical and experimental techniques, and provide reliable design guidelines. Thus, we are conducting a comprehensive program to study structural vibration in components subjected to two-phase flow. This report reviews the current understanding of vibration of circular cylinders in quiescent fluid, cross-flow, and axial flow, with emphasis on excitation mechanisms, mathematical models, and available experimental data. A unified theory is presented for cylinders oscillating under different flow conditions. Based on the theory, future research needs are outlined.

The literature on parameterizations of cloud microphysical processes was reviewed to examine the theoretical bases of those parameterizations and to evaluate their applicability to regional models. New parameterizations were produced by multiple regression upon the solution fields derived from simulations of a cloud model incorporating sophisticated microphysics. The currently available rates for cloud microphysical interactions were generally derived under the assumption that the size distribution functions for various hydrometeors are given. Such parameterizations must therefore be applied with caution because the spectral evolution of various types of hydrometeors in reality varies significantly during the stages of cloud development. Uncertainties exist in assigning values for aerodynamic properties such as the bulk collection efficiency, and the growth processes for various types of ice crystals are not well enough known for accurate multiphase cloud-microphysics parameterizations. The new parameterizations, in general, compare favorably with those currently available and are more efficient and applicable to regional models. The largest discrepancies occur in the autoconversion rates, whereas the accretion rates agree closely when the assumed collection efficiencies in other formulas are smaller than unity.

Weight losses of marble and limestone samples exposed to outdoor environments at field sites in the eastern United States have been monitored in studies initiated in 1984. The procedures are described, and the results are tabulated and discussed. A rate of marble loss approximately equivalent to 16 micrometers of surface recession per year was found in North Carolina, and losses of this order were also observed in New Jersey, New York, and Washington, DC. Limestone weight losses were much higher than for marble in the first year; loss of extraneous materials from the porous limestone appeared to be a likely contributor to the overall loss. The rate of limestone loss diminished in the second year, though it continued to be higher than for marble. Exposures are continuing in a planned 10-yr program of tests.

Report of activities of the Argonne Physics Division, including medium-energy physics research, ATLAS research, theoretical nuclear physics, superconducting LINAC development, and accelerator operations.