Browsing by Subject "Hydrodynamics--Simulation methods"

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A block model for submarine slides involving hydroplaning
(2007) Hu, Hongrui, 1977-; Wright, Stephen G. (Stephen Gailord), 1943-
This dissertation details the development of a block model for the movement of submarine slides with emphasis on possible hydroplaning. Unlike previous models, the block model simulated the mechanism of hydroplaning by monitoring the contact condition between the bottom surface of the slide mass and the underlying ground. The effect of hydroplaning on the movement of the slide mass is considered by changing the forces applied on the slide mass by the underlying ground according to the contact condition. The hydrodynamic stresses applied on the slide mass by the surrounding fluid are determined based on the numerical simulations of the flow around a sliding mass. The sliding process of the block is disretisized in a step-by-step manner using a Newmark scheme. A computer program is also written to implement the block model. The block model is validated by comparisons between the numerical results and data reported by Mohrig, et al (1999) for laboratory experiments on subaqueous slides. An illustrative study is also conducted using the block model for the movement of the sediment slabs during the Storegga Slide. The block model has successfully predicted the occurrence of hydroplaning and run-out distances of subaqueous slides. Numerical results with the block model supports the mechanism of hydroplaning for subaqueous slides with greater run-out distances than comparable subaerial slides.
Continuum simulations of fluidized granular materials
(2004) Bougie, Jonathan Lee; Swift, Jack B.
A successful hydrodynamic theory of granular media could allow scientists and engineers to exploit the powerful techniques of fluid dynamics to describe granular phenomena. We use computer simulations to test a set of continuum hydrodynamic equations for granular media which were proposed by Jenkins and Richman nearly twenty years ago [59]. We use these continuum simulations as well as molecular dynamics (MD) simulations to investigate phenomena in vertically shaken layers of grains. When a layer of grains is shaken vertically by a plate with maximum acceleration greater than the acceleration of gravity, the layer will be thrown off the plate with each cycle of the plate. Continuum and MD simulations show that normal shocks form in the layer upon contact with the plate later in the cycle. We show that increasing the coefficient of restitution of the particles increases the speed of the shock in the layer, and that the limit of perfectly elastic particles is not singular. In addition, deeper layers of particles exhibit denser packing fractions near the plate and higher shock speeds than shallow layers. Pressure gradients produced by these shocks play an important role in the dynamics of standing wave patterns formed in oscillated granular layers. Both continuum and molecular dynamics simulations produce standing waves with wavelengths which agree with previous experiments. Continuum simulations reproduce stripe patterns found in MD simulations of frictionless particles, but do not reproduce square or hexagonal patterns found in experiments and MD simulations of frictional particles. Finally, we show that fluctuations present in molecular dynamics simulations are not captured by our current continuum model. By fit to Swift-Hohenberg theory, we find these fluctuations in MD simulations to be several orders of magnitude larger than fluctuations found in ordinary fluids. Differences between patterns in continuum and MD simulations near onset are found to be consistent with the presence of fluctuations in MD simulations without friction.