We present some developments in the particle finite element method (PFEM) for analysis of complex coupled problems in mechanics involving fluid---soil---structure interaction (FSSI). The PFEM uses an updated Lagrangian description to model the motion of nodes (particles) in both the fluid and the solid domains (the later including soil/rock and structures). A mesh connects the particles (nodes) defining the discretized domain where the governing equations for each of the constituent materials are solved as in the standard FEM. The stabilization for dealing with an incompressibility continuum is introduced via the finite calculus method. An incremental iterative scheme for the solution of the non linear transient coupled FSSI problem is described. The procedure to model frictional contact conditions and material erosion at fluid---solid and solid---solid interfaces is described. We present several examples of application of the PFEM to solve FSSI problems such as the motion of rocks by water streams, the erosion of a river bed adjacent to a bridge foundation, the stability of breakwaters and constructions sea waves and the study of landslides.

Possibilities of the particle finite element method for fluid---soil---structure interaction problems

Observational and numerical modeling methods for quantifying coastal ocean turbulence and mixing

: This report is the second in a series on the numerical model SBEACH (Storm-induced BEAch CHange). SBEACH calculates dune and beach erosion produced by storm waves and water levels; bar formation and movement produced by breaking waves are also simulated. The model is empirically based and was originally developed from a large data set of net cross-shore sand transport rates and beach profile change observed in large tanks. The empirical formulation, model sensitivity tests, and a field validation case are described in Report 1. In the present report, Report 2, the capability of the model to simulate berm and dune erosion is evaluated using recently acquired field data from both US east and west coasts. Hypothetical storm events are also simulated to demonstrate model applicability and potential uses for predicting initial adjustment of beach fill and its response to storm action, including poststorm recovery. A complete description of the mathematical formulation of the model is provided with numerical algorithms comprising the solution scheme. Improvements of the model are also presented. The associated wave model has been generalized by using complete linear wave theory everywhere on the profile without shallow-water approximations, a capability important in general applications for irregular bottom profiles subjected to waves of widely ranging characteristics. Refraction has been included, and an option is provided to randomize the wave input for better representing forcing conditions in the field.

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SBEACH: Numerical Model for Simulating Storm-Induced Beach Change. Report 2. Numerical Formulation and Model Tests

We apply a model for sand dunes to calculate formation of dunes on Mars under the present Martian atmospheric conditions. We find that different dune shapes as those imaged by Mars Global Surveyor could have been formed by the action of sand-moving winds occuring on today's Mars. Our calculations show, however, that Martian dunes could be only formed due to the higher efficiency of Martian winds in carrying grains into saltation. The model equations are solved to study saltation transport under different atmospheric conditions valid for Mars. We obtain an estimate for the wind speed and migration velocity of barchan dunes at different places on Mars. From comparison with the shape of bimodal sand dunes, we find an estimate for the time scale of the changes in Martian wind regimes.

http://www.comphys.ethz.ch/hans/p/447.pdf

Dune formation on the present Mars.

This paper presents the results of a comprehensive experimental program focused on the impact of extreme hydrodynamic forces on structural models generated by a turbulent hydraulic bore. The parameters investigated include: (1) bore depth-time history; (2) initial flume-bed conditions (dry bed versus wet); and (3) damping effect of mitigation walls on the hydrodynamic forces. At impact, the maximum inundation (bore) depths varied between 250 mm and 450 mm and the bore front velocity ranged from 2.6 m/s to 5.0 m/s. High-speed video recordings of the bore-structural model interaction were captured simultaneously with the base shear force-, pressure-, base overturning moment-, and top lateral displacement-time histories experienced by the structural models. Three force components were identified in the bore-induced force-time histories: impulsive, run-up (transient hydrodynamic force), and quasi-steady hydrodynamic. The impulsive or run-up force was the maximum force component experienced by the structural m...

Experimental Modeling of Extreme Hydrodynamic Forces on Structural Models

The Journal of Waterway, Port, Coastal, and Ocean Engineering presents information regarding the engineering aspects of dredging, floods, ice, pollution, sediment transport, and tidal wave action that affect shorelines, waterways, and harbors. The development and operation of ports, harbors, and offshore facilities, as well as deep ocean engineering and shore protection and enhancement, are also covered. Other topics include the regulation and stabilization of rivers and the economics of beach nourishment.

Tokuo Yamamoto

Papers

Journal of Waterway, Port, Coastal, and Ocean Engineering