本文以數值方法探討微圓管內之滑動氣體流場，工作流體為氮氣，若Knudsen值介於10/sup -3/≦Kn≦0.1則流體可假設為連體但邊界須為可滑動，如此才能將邊界上流體切線方向上的動量與能量和管壁不完全交換的情況成功的模擬。雖然本文作者在不久前成功地以解非穩態可壓縮之Navier-Stokes方程式來探討此一問題，但因此方程組之雙曲及拋物線特性使得此一解法非常沒有效率，本研究結果證實滑動氣體流場可由穩態可壓縮之邊界層方程式來求解。由於穩態邊界層方程式為一組拋物線方程組，其解可以快速求得，使得此一解法成為研究滑動氣體流場之高效率精確工具。本研究結果顯示若微圓管流場為滑動層流則其f‧Re的值比傳統大管來的低，滑動邊界是由於氣體分子與管壁動量及能量交換不完全所致，此一滑動邊界對流場速度及質流率均有決定性的影響。 The present work studies the friction characteristics of gaseous slipflow in microtubes. The reduced diameter of microtubes has significantinfluences on the flow. The degree of influence depends on the Knudsennumber. If the Knudsen number is on the range of 10/sup -3/≦Kn≦0.1,the fluid can be assumed to be a continuum but a slip boundarycondition at the tube wall has to be employed to account for theincomplete tangential momentum and energy exchanges between the gasmolecules and the wall. Although slip flow in microtubes can beinvestigated by solving numerically the compressible Navier- Stokesequations, the hyperbolic-parabolic character of the equations makesit very inefficient. The very large length to diameter ratio suggeststhat they can be predicted accurately as well as efficiently bysolving the compressible boundary-layer equations. The paraboliccharacter of the boundary-layer equations renders the present method avery efficient and accurate tool in studying slip flows. The resultsconfirm the findings of earlier investigators that the product off.bcdot.Re is lower for laminar microchannel flows than for largertubes when the flow is in the slip region.
