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		| Paper: | The Marriage of Gas and Dust |  
		| Volume: | 498, Numerical Modeling of Space Plasma Flows ASTRONUM-2014 |  
		| Page: | 177 |  
		| Authors: | Price, D. J.; Laibe, G. |  
		| Abstract: | Dust-gas mixtures are the simplest example of a two fluid mixture. We show that when simulating such mixtures with particles or with particles coupled to grids a problem arises due to the need to resolve a very small length scale when the coupling is strong. Since this is occurs in the limit when the fluids are well coupled, we show how the dust-gas equations can be reformulated to describe a single fluid mixture. The equations are similar to the usual fluid equations supplemented by a diffusion equation for the dust-to-gas ratio or alternatively the dust fraction. This solves a number of numerical problems as well as making the physics clear. |  
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