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A method is described for the solution of time-dependent problems concerning the flow of viscous incompressible fluids in several space dimensions. The method is numerical, using a high-speed computer for the solution of a finite-difference approximation to the partial differential equations of motion. The application described here is to a study of the development of a vortex street behind a plate which has impulsively accelerated to constant speed in a channel of finite width; the Reynolds-number range investigated was 15 ≤ R ≤ 6000. Particular attention was given to those features for which comparison could be made with experiments, namely, critical Reynolds number for vortex shedding, drag coefficient, Strouhal number, vortex configuration, and channel-wall effects. The nature of the early stages of flow-pattern development was also investigated.

Monte Carlo results are reported for the structure of molecular clusters consisting of a lithium fluoride ion pair surrounded by 50 water molecules at temperatures of 298 and 500 K using Hartree-Fock interaction potentials that include some three-body terms. It is shown that when separated by distances of between 3 and 4 Å each ion is surrounded by a nearest-neighbor shell of four atoms, hydrogen in the case of the fluoride ion and oxygen in the case of the lithium ion. There is evidence of both secondary hydrogen atom and secondary oxygen atom structure around the ions but there is no evidence of any larger hydration shell. It is tentatively concluded that the coordination number of 4 for each ion is responsible for the behavior of lithium and fluoride ions as ``structure makers.''

The equations of the Boussinesq approximation to the Navier—Stokes equations are solved numerically for the problem of a fluid layer heated from below. Solutions are obtained throughout the range of Rayleigh numbers from critical to R = 107. Free boundary solutions are compared with analysis, and rigid boundary solutions are compared with experiment. The dimensionless heat transport varies as R⅓ for free boundaries and for rigid boundaries a variation of about R0.296 is observed. Excellent agreement is obtained with both analysis and experiments and by an examination of various modal behaviors a number of the observed properties of the flow can be explained.