受橫流影響的衝擊噴流，在噴流與橫流的交界處上游會產生一至兩個馬蹄型渦旋，在應用上時常會因為有馬蹄型渦旋而產生負面的影響。本研究使用實驗方法探討受橫流影響之傾斜衝擊噴流的流場特性。在一拖曳式水槽中安裝噴流與壁面設備，改變噴流後傾角度(α = 0° ~ 50°)以及噴流對橫流速度比(Ru ≡ uj /uc = 3 ~ 85)，使用雷射光頁輔助質點軌跡流動可視化技術觀測噴流與壁面間垂直面與水平面的流場特徵行為，再以質點影像測速儀量測速度場，進行流動拓樸分析，並計算渦度及紊流強度。受橫流影響之傾斜衝擊噴流的流場狀態，在垂直對稱面出現三種特徵模態：(1)無衝擊、(2)輕微衝擊、(3)衝擊效應主宰。在相同噴流對橫流速度比的情況下，隨著傾斜角度的增加，噴流對壁面的撞擊影響減弱，當速度比小於7，噴流的後傾斜角度小於50度時，噴流對壁面的影響較弱，為無衝擊模態；當速度比大於20，噴流的後傾斜角度可以有效的控制渦旋數量的產生。在相同傾斜角時，隨著噴流對橫流速度比增加，噴流對壁面的撞擊影響增強。水平面流場觀測結果顯示，無衝擊模態中，在靠近壁面的位置並無特殊流場結構；輕微衝擊模態中，靠近壁面處噴流輕微衝擊壁面會產生側向噴流擴張；衝擊效應主宰模態中，在距離壁面較近的水平面會產生馬蹄型渦旋，三種模態在圓管與噴流出口下游處皆會有渦旋逸放的現象。渦度與紊流強度分佈顯示，於衝擊效應主宰模態中，因橫流對衝擊噴流而產生的渦流附近會呈現較大的渦度與紊流強度。

An impinging jet in crossflow would generate one or two horseshoe vortices around upstream corner of the jet and crossflow. The horseshoe vortices often caused negative effects in engineering applications. The flow characteristics of an inclined impinging jet in crossflow was studied experimentally in a towing water tank. The water jet flow was provided via a system composed of a pump and a stainless-steel tube. The wall subject to the impingement of the water jet was an acrylic flat plate installed at a distance under the exit of the water jet. The tube and acrylic flat plate were linked together and immersed in the water of the towing water tank. The towing motion applied to the tube and flat plate induced the crossflow which would influence the flow field of the impinging jet. Two dominant physical and geometric non-dimensional parameters were varied: (1) the jet-to-crossflow velocity ratio (Ru ≡ uj /uc = 3 – 85) and (2) the jet inclination angle (α = 0° ~ 50°). The laser-light sheet particle tracking flow visualization technique was used to obtain images of tracer particles seeded in the flow. A particle image velocimetry (PIV) was applied to measure the velocity field. The velocity vectors, streamlines, topological flow patterns, vorticity distributions, and turbulence intensities were calculated and analyzed. Three characteristic flow modes: no impingement, slight impingement, and impingement effect dominated modes were observed in the domain of Ru and α in the vertical symmetry plane. In the no impingement mode, the jet-to-crossflow velocity ratio was low so that the jet was brought to the downstream area without hitting the wall surface. In the slight impingement mode, the jet-to-crossflow velocity ratio was higher than that of the no impingement mode so that the jet impinged slightly on the wall before flushed downstream by the crossflow. No particular flow structures were observed. In the impingement effect dominated mode, the jet-to-crossflow velocity ratio was higher than that of the slight impingement mode so that the jet strongly impinged on the wall and was flushed downstream by the crossflow. One or two vortices might appear upstream the bent jet, which were induced by the interaction between the impingement of the jet on the wall and the crossflow at mid to high values of Ru and α. In the horizontal plane, no specific flow structures were found in the no impingement mode. In the slight impingement mode, the slight impingement of the jet on the wall would cause lateral expansion of the jet flow. The horseshoe flow structure appeared in the impingement effect dominated mode. The vorticities and turbulence intensities revealed notably high values around the area of the vortices.

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