Paul Guard

An analytical model for bore-driven run-up

We use a hodograph transformation and a boundary integral method to derive a new analytical solution to the shallow-water equations describing bore-generated run-up on a plane beach. This analytical solution differs from the classical Shen–Meyer runup solution in giving significantly deeper and less asymmetric swash flows, and also by predicting the inception of a secondary bore in both the backwash and the uprush in long surf. We suggest that this solution provides a significantly improved model for flows including swash events and the run-up following breaking tsunamis.

Modelling sheet flow sediment transport using convolution integrals

Existing simple, practical models used to predict the transport rate of cohesionless sediment in the sheet flow regime have obvious shortcomings. They generally relate the transport rate directly to the velocity just outside the boundary layer or to an estimate of the instantaneous bed shear stress. Such models neglect important unsteady flow effects such as phase lags between the flow forcing and the bed shear stress and between the bed shear stress and the transport rate. Most also fail to account for the influence of the acceleration time history on the magnitude of the bed shear stress. In this paper a new simple, practical model is developed that aims to provide similar prediction accuracy as more complex process-based models without the computational expense. Convolution integrals are employed to obtain solutions for the governing differential equations in the time domain while accounting for the important unsteady flow effects.

Sheetflow Sediment Transport Modeling: Including Boundary Layer Streaming

A two-phase sheetflow sediment transport model is extended to account for boundary layer streaming due to the horizontal non-uniformity present in real-world progressive waves. The model predictions are compared with experimental results obtained in a large-scale wave flume facility (which include boundary layer streaming) and with results from wave tunnel facilities (which do not include boundary layer streaming). The experimental and modeling results both highlight the importance of boundary layer streaming for real-world sediment transport modeling.

Sheet flow sediment transport modelling using convolution integrals

A new method for the prediction of instantaneous sediment transport rates in the sheet flow regime is presented based on the use of convolution integrals. The convolution integral technique allows solution of the governing differential equations in the time domain while accurately representing important unsteady flow effects. This technique overcomes many of the limitations of simple quasi-steady sediment transport models and does not require the computational effort of more detailed process-based models. The present model has been parameterised using results from a more detailed process-based two-phase model. Preliminary results indicate that the technique is successful in predicting net transport rates in oscillatory flow tunnel experiments in the sheet flow regime. Extension of the model to other sediment transport regimes and incorporation of real-wave effects such as boundary layer streaming is possible.