Abstract
本實驗以拍照的方式研究旋轉槽流之渦捲流不穩定特性，拍照的方式分成切面照和側面照。切面照片結果顯示（１）在靜止不轉時，較小渦捲已很清楚地產生，這是因為煙霧垂直地由圓孔注入主流，造成渦流的產生。（２）當轉速為１５ｒｐｍ時，渦流開始沿著流向成長，而渦流數目也從原本靜止時的１５個變成１１個。（３）當轉速為２４ｒｐｍ時，渦流沿著流向成長得太大，以至於渦流之間發生擠壓和合流效應，這時渦流變得不對稱，且個數也變少了。側面照片結果顯示（１）當轉速大於１５ｒｐｍ時，渦流開始沿著流向成長，邊界層也跟著成長。（２）當轉速大於３０ｒｐｍ時，渦流沿著流向成長得太快，以至於在出口前渦流就散亂了。 同時，側面照片能直接量測渦流成長的發生位置，如此得到的發生位置是比Ｍａｔｕｂａｒａ等學者的猜測較可靠的。從葛特勒數（Ｇｏｅ－ｒｔｌｅｒ）與無因次波數（ｄｉｍｅｎｓｉｏｎｌｅｓｓ ｗａｖｅｎｕｍｂｅｒ）關係圖顯示，本實驗與其他學者的理論分析還算吻合。The purposes of the experimental study are to understand theflow pattern and to obtain the critical parameters for theonset of longitudinal vortices in rotating boundarylayer. The cross-section photos show that (1) roll-cells atrotation speed 0 rpm are induced by the smoke injection flow.(2) At rotation speed 15 rpm, the roll-cells grow up alongthe flow direction and the number of the roll-cells iseleven. (3) At rotation speed 24 rpm, the roll-cells grow upquicker. The repulsion and coelescence of the roll-cellsstart and the roll-cells become asymmetric in the downstreamof the vortex onset position. The side-view photos show that(1) at rotation speed larger than 15 rpm, the smoke boundarylayer grows up along the flow direction (2) at rotation speedlarger than 30 rpm, the vortices grow up so guickly that roll-cells break down before passing the exit. For the side-viewphotos, it is possible to determine the onset position oflongitudinal vortices in the rotating boundary layer flow.The comparison of present and previous studies is made.The relationship of critical Goertler Number vs. thedimensionless wave number in this experiment fit thoseof theoretical calculations of Hwang, Lin, and Lin inpreparation in reasonal error range.