A new design capability for hypersonic flight vehicles and microscale devices?

摘要

Traditionally, the Navier-Stokes equations are used for modelling all applications of the transfer of heat and momentum in fluid flows. They have been successfully applied to problems ranging from liquids in capillaries to the atmosphere of planets. However, these equations make poor predictions (in comparison with experiment) of the essential features of low-density hypersonic gas flows - impacting on, for example, high-altitude high-speed aerodynamic design. Neither are they a good model for predicting the characteristics of fluid (usually gas) flows in the rapidly-developing technology of micro-scale devices. In both cases this is due to the relatively large mean free path of the gas molecules when compared with a characteristic length scale in the system. However, by revisiting the fundamental gas kinetic equation it is possible to derive additional, higher-order equations appropriate for these two scenarios, but until recently it has been exceptionally difficult to solve them. This paper describes new solutions of these equations and applications to two important problems in aerodynamics and microfluidics. The encouraging results indicate that a new paradigm is emerging for design and modelling problems for which the Navier-Stokes equations fail.