An investigation into the effects of complex topography on particle dry deposition

Abstract

There is a requirement to predict the spatial variation of particle dry deposition following a nuclear accident. The interaction of landscape features, atmospheric flow and particle dry deposition has been investigated with this in mind. Wind tunnel studies have been used with computational fluid dynamics to predict the deposition rate relative to a flat landscape. Good quantitative agreement was seen for this relative deposition rate. Landscape shapes showed significant effects on deposition rate, increasing it by more than two in some cases, over limited areas. The effect of turbulence intensity, in the absence of landscape features, was also studied and a weak relationship to dry deposition was observed. Computational fluid dynamics methods used in wind tunnel comparisons were extended to a wide range of landscape cases. Deposition rates varied spatially around the landscape features. In general, for hills and ridges, deposition was seen to increase on the windward face, decrease on the leeward face and near wake, and increase in the further wake, before returning to the flat case value. The computational results were applied to a real landscape with the use of a customised geographical information system. Good general agreement was seen when compared with a test case.