An hybrid method, coupling the direct numerical solution of the Bhatnagar-Gross-Krook (BGK) kinetic equation and a Navier-Stokes model is presented. The computational physical domain is decomposed into kinetic and continuum sub-domains using an appropriate criteria based on the local Knudsen number and proper gradients of macro-parameters, computed via a preliminary Navier-Stokes solution throughout the whole physical domain. The coupling is achieved by matching half fluxes at the interface of the kinetic and Navier-Stokes domains, thus taking care of the conservation of momentum, energy and mass through the interface. The proposed method is used for the simulation of the flow through a micro-slit. Outlet to inlet pressure ratio of 0.1, 0.5 and 0.9 are considered, for a wide range of Knudsen number. The local parameters (density, velocity and temperature) along symmetry axis show satisfactory agreement with those computed by the continuum model.
Coupling kinetic and continuum equations for micro scale flow computations
CROCE, Giulio
2011-01-01
Abstract
An hybrid method, coupling the direct numerical solution of the Bhatnagar-Gross-Krook (BGK) kinetic equation and a Navier-Stokes model is presented. The computational physical domain is decomposed into kinetic and continuum sub-domains using an appropriate criteria based on the local Knudsen number and proper gradients of macro-parameters, computed via a preliminary Navier-Stokes solution throughout the whole physical domain. The coupling is achieved by matching half fluxes at the interface of the kinetic and Navier-Stokes domains, thus taking care of the conservation of momentum, energy and mass through the interface. The proposed method is used for the simulation of the flow through a micro-slit. Outlet to inlet pressure ratio of 0.1, 0.5 and 0.9 are considered, for a wide range of Knudsen number. The local parameters (density, velocity and temperature) along symmetry axis show satisfactory agreement with those computed by the continuum model.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.