Computer modeling of multiscale fluid flow and heat and mass transfer in engineered spaces

Design and analysis of fluid flow and heat and mass transfer in engineered spaces require information of spatial scales ranging from 10^{- 7} m to 10³ m and time scales from 10^{- 1} s to 10⁸ s. The studies of such a multiscale problem often use multiple computer models, while each of computer models is applied to a small range of spatial and time scales. Accurate solution normally requires exchanging information between a macroscopic model and a microscopic model that can be done by coupling the two models. With the approach, it is possible to obtain an informative solution with the current computer memory and speed. This paper used a few examples of fluid flow and heat and mass transfer in engineered spaces to conclude that a coupled macroscopic and microscopic model is likely to have a solution and the solution is unique. A stable solution for the coupled model can be obtained if some criteria are met. The information transfer between the macroscopic and microscopic models is mostly two ways. A one-way assumption can be accepted when the impact from small scale on large scale is not very significant.