UNCOUPLED 3D LATTICE ANIMATION: A NEW VISUALISATION OF FLOODPLAIN INUNDATION EVENTS

摘要

Fundamental problems with existing unsteady 3D (three-dimensional) floodplain modelling are discussed using as an example dambreak simulations through Havelock North, New Zealand. Geographical mapping approaches tend to rely on solution methods analogous with terrain modelling, denying the fundamental hyperbolic nature of flood wave propagation. Alternatively, conventional 2D models adapted for coastal modelling are used, but these cannot resolve incised channels at a horizontal grid spacing less than the depth. In both cases, gross errors tend to result, leading to dangerous underdesign of drainage channels. However, if the flow direction is known, long established parallel flow analysis uncouples vertical and lateral cross-dimensions from the resolution limit set by turbulent length scales. CELL Integrals then allow full wave propagation solutions to be developed over a 3D lattice, with each instantaneous level/flow solution expressed numerically on grids suitable for multi-layered map presentation and animation. Mathematical limits are noted within which a warped hyperbolic surface can smoothly connect the free surfaces of a series of channel cross-sections through curved channels.