摘要
本文經由連續方程式、芮維－史托克運動方程及密度擴散方程式，利用數值分析以變向隱式法（alternative direction implicit scheme）的差分方法建立數值模式，探討二維密度層變流體通過半橢圓之柱體及半圓柱體等障礙物時背面波之形成及流場流況的變化情形。引生的流場變化分三區（即形成於障礙體上游的阻滯區，形成於障礙體下游之分離區以及上述二區外之場內區）分別加以研討。結果顯示背面波的形成及發展受流場的密度福祿數F、雷諾數R及障礙體的高寬比ε所影響。F值減小將使分離區的發展受到壓抑，背前波的發展也將加快，容易造成流場的不穩定，並且使阻滯區向上游延伸。ε小的障礙體，分離區不容易形成，背面波的發展也較快，同時流況受R值的影響相當明顯。減小ε及R值，阻滯區的長度將增長，但並不十分明顯，而R值及ε值的增加將促使近分離區的發展，有助於流場的穩定。
關鍵字
無資料並列摘要
Numerical techniques of ADI method for integrating the time-dependent Navier-Stokes equations, which have proven useful in the study of homogeneous viscous flows, have been extended in this study to investigate the flows of stably stratified viscous fluids over a ridge of semielliptical cylinder of infinite length with the different ratio of height to half-width of the obstacle. Various properties of the flow field and the characteristics of the lee waves formulated are investigated.Results show that the stratification tends to encourage the development of overturning flow regions on the upstream slope (blocking effect) and downstream from the ridge. Lee waves produced for viscous flows of stratified fluid past over obstacles depend on the internal Froude number and the Reynolds number of the flow, and the aspect ratio (i.e. the ratio of height to half-width) of the obstacle to some extent. The existences of upstream influence and the flow seperation induced by the obstacle have a great effect on the development of the lee-wave field for cases of small value of internal Froude number.