Automatic Conversion of Visually Consistent Digital Maps to Conforming Geometry for Computational Fluid Dynamics

A method for automatic conversion of three-dimensional (3D) digital maps for visual purposes to a conforming geometry for city-scale computational fluid dynamics (CFD) is proposed in this paper. Difficulties in automatic conversion of visually consistent 3D digital maps to a finite-element mesh for city-scale CFD are as follows: (1) representation of the buildings without consistent topological information, (2) independent and inconsistent layers for buildings and the ground surface, and (3) existence of unnecessary and spontaneous minor gaps on the building surface. The proposed automatic conversion method resolves all these problems by a combination of conventional algorithms for computational geometry. The major contribution of this paper is not a proposal of new algorithms in computational geometry but includes the following: (1) clear definition of the problems in automatic conversion of 3D digital maps for visual purposes to the analysis domain for city-scale CFD, and (2) proposal of a solution for the given problems as a combination of existing algorithms. In this paper, problems in 3D digital maps for visual purposes as input data for generating a finite-element mesh for city-scale CFD are discussed. Also, the automatic conversion process and illustrative examples of mesh generation with a city-scale CFD simulation are described in detail.