This paper describes a continuum-based CFD solution for flow in a microchannel using near-wall scaling and first-order slip conditions. This near-wall scaling approach is used in an attempt to capture the Knudsen layer effects. The near-wall scaling itself requires the distance to the nearest wall as an input parameter and this distance is calculated using a simple technique which involves the solution of a diffusion equation for a scalar value φ of the form div(gradφ) = −1. The wall distance is then deduced for this scalar field and implemented in the near-wall scaling function. In order to demonstrate the efficacy of the wall distance/near-wall scaling technique the methodology is applied to two practical cases. The first case describes Poiseuille flow in a microchannel (for which analytical solutions exist) and the second considers flow in a microchannel with two 90° bends. The results show that the implementation of the wall distance procedure is relatively straightforward and that the use of the near-wall scaling increases the mass flow rates in both of the cases considered.
- Nanotechnology Institute
A Procedure for Calculating Wall Distance in Arbitrary Microchannel Geometries
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Scanlon, TJ, Reese, JM, & O’Hare, L. "A Procedure for Calculating Wall Distance in Arbitrary Microchannel Geometries." Proceedings of the ASME 4th International Conference on Nanochannels, Microchannels, and Minichannels. ASME 4th International Conference on Nanochannels, Microchannels, and Minichannels, Parts A and B. Limerick, Ireland. June 19–21, 2006. pp. 363-368. ASME. https://doi.org/10.1115/ICNMM2006-96037
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