Dispersion & Transport Phenomena in Urban Environments

Jyh-Ming Lien, Fernando Camelli, David Wong, Yanyan Lu, Stephen Donnelly, Evan Behar

The marks of Geographic Information Science and technology (GISc & T) can be found in many aspects of everyday’s life. Data with 3D information are rarely stored explicitly as 3D data in GIS (with the exception of TIN), but are often stored as 2D data with the third dimension information stored as an attribute in the table. As a result, GIS are often criticized of 2.5D in nature. The third dimension is highly relevant in today’s world, ranging from the dispersion of volcanic ashes from Iceland all over the Europe where the clouds are 3D objects, to the pumping of oil from the broken pipe in the Gulf of Mexico where the traces are 3D clusters.

Since the introduction of the concept of “Digital Earth,” almost every major international city has been re-constructed in the virtual world. A large volume of geometric models describing urban objects has become freely available in public domain via software like Google Earth. Although mostly created for visualization, the urban models from GIS can benefit many applications beyond visualization including video games, city scale evacuation plan, traffic simulation and earth phenomenon simulations. However, these urban models are mostly loosely structured and implicitly defined and require tedious manual preparation that usually take weeks if not months before they can be used.

Examples: Lower Manhattan
Water-tight mesh for CFD simulation generated by our new algorithm.
There are 1,161,850 vertices, 2,310,610 triangles, and 5,397 buildings in this example. The input composed of 45,496 polygons.

NYC water-tight mesh

Examples: Downtown Oklahoma City
In the following video, the green cloud represents an isosurface of 0.0001, and the brown cloud is an isosurface 0.00001. The release is continuous, and with a rate of 1 meter per second. The location is south of the public library in an area where there is a building currently. The inflow is a westerly wind with a wind speed of 5 m/s at 10 meters above ground level. The movie represents 500 seconds of real time from the moment that the release started. The Navier-Stokes equations and the transport and dispersion equations were integrated for 500 seconds (real time) using a mesh of 40 million tetrahedra, and 7 million points.

Comparing Four Different CFD Approaches to Simulate Transport and Dispersion in Oklahoma City, Fernando Camelli, Rainald Lohner, Jyh-Ming Lien and David Wong, 17th Conference on Air Pollution Meteorology with the A&WMA, part of the 92nd AMS Annual Meeting, Jan. 2012
Web Site / BibTeX
Generating Seamless Surfaces for Transport and Dispersion Modeling in GIS, Fernando Camelli and Jyh-Ming Lien and Dayong Shen and David W. Wong and Matthew Rice and Rainald Lohner and Chaowei Yang, Geoinformatica, April 2012
Web Site / Paper (pdf) / Link / BibTeX
Fast and Robust Generation of City Scale Urban Ground Plan, Jyh-Ming Lien and Fernando Camelli, and David Wong, Proc. Computer Graphics International (CGI), June 2011
Web Site / Paper (pdf) / BibTeX
Creating Building Ground Plans via Robust K-way Union, Jyh-Ming Lien and Fernando Camelli and David Wong and Yanyan Lu and Benjamin McWhorter, Visual Computer, in press 2011
Web Site / Paper (pdf) / BibTeX
Fast and Robust Generation of City-Scale Seamless 3D Urban Models, Yanyan Lu and Evan Behar and Stephen Donnelly and Jyh-Ming Lien and Fernando Camelli, and David Wong, Computer-Aided Design, volume 43, issue 11. Also in Proc. SIAM Conference on Geometric and Physical Modeling (GD/SPM), Nov. 2011
Web Site / Paper (pdf) / SPM presentation / BibTeX
Computer Science @ George Mason University