The usefulness of higher-order constitutive relations for describing the Knudsen layer.
- Brunel University, Uxbridge, UK
- University of Strathclyde, Glasgow, UK
The Knudsen layer is an important rarefaction phenomenon in gas flows in and around microdevices. Its accurate and efficient modeling is of critical importance in the design of such systems and in predicting their performance. In this paper we investigate the potential that higher-order continuum equations may have to model the Knudsen layer, and compare their predictions to high-accuracy DSMC (direct simulation Monte Carlo) data, as well as a standard result from kinetic theory. We find that, for a benchmark case, the most common higher-order continuum equation sets (Grad's 13 moment, Burnett, and super-Burnett equations) cannot capture the Knudsen layer. Variants of these equation families have, however, been proposed and some of them can qualitatively describe the Knudsen layer structure. To make quantitative comparisons, we obtain additional boundary conditions (needed for unique solutions to the higher-order equations) from kinetic theory. However, we find the quantitative agreement with kinetic theory and DSMC data is only slight.
- Research Organization:
- Sandia National Laboratories
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 948262
- Report Number(s):
- SAND2005-1525J
- Journal Information:
- Proposed for publication in Physics of Fluids., Journal Name: Proposed for publication in Physics of Fluids.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Kinetic-theory predictions of clustering instabilities in granular flows: beyond the small-Knudsen-number regime
Parallel Fokker–Planck-DSMC algorithm for rarefied gas flow simulation in complex domains at all Knudsen numbers