摘 要 本研究以實驗方式來探討排放角度和底床邊界對單管浮昇射流之影響。實驗在一靜止的水槽中以台車拖曳排放鹽水的射流管來模擬橫向流場中的浮昇射流，實驗採用雷射引致螢光法配合CCD攝影機以連續擷取射流之影像，經由影像處理可得射流的軌跡和濃度場。實驗結果顯示：在無邊牆效應、有橫向流的狀況下，於同一下游距離，排放角度愈大，則射流的稀釋率會愈大。當豎管接近底床時，角度變化是否產生附著現象，由排放角度與豎管高度決定。若排放角度 時，附著現象便會發生，然而散佈係數會隨著橫向流流速的增加而變小。當附著現象發生時，邊界會抑制浮昇射流的混合，導致射流的稀釋情形變差。實驗結果並與美國環保署所發展之模式CORMIX比較，發現該模式無法準確地預測邊界效應及附著現象的稀釋情形。本研究之結果可供設計海洋放流管的排放角度參考。 Abstract An experimental study of discharge angle and boundary effect on buoyant jets is presented. The experimental setup comprises a towed single jet discharging salt water into a laboratory tank with a horizontal plexiglass plate close to the diffuser port. Trajectories and concentration distributions of buoyant jets were measured by the planner laser-induced fluorescence (PLIF) method. It was found, due to the Coanda effect, buoyant jets will cling to the boundary when discharge angle , where β is the spreading coefficient. This phenomenon has a marked effect on the jet trajectory and its near-field dilution. Results of this study also showed that the near-field model CORMIX fails to predict above phenomenon.
