本研究採用大渦模式(LES)結合拉格朗日顆粒追蹤法研究通風環境中液滴射流的擴散行為，並以風洞實驗數據進行驗證模擬結果。研究成果發現當橫向風(θ = 90)，風速由Ua = 1 m/s增加至6 m/s時，特徵射流長度由Lm = 13.8D降至2.3D，射流的側向擴散範圍變小從14D減少至4D (D: 噴嘴直徑)。當速度比Ua/Ujet < 0.3時，射流發生分歧現象，顆粒分佈逐漸由單股轉為雙股。當速度比Ua/Ujet > 0.3時，橫風抑制渦旋形成，分歧現象減弱。且液滴粒徑大小會影響其分佈特性，在橫向風向下，粒徑為1-10 μm的液滴濃度會呈現雙峰對稱分佈；粒徑為100-200 μm內，濃度稍具不對稱性分佈；粒徑500 μm時，則濃度因重力迅速衰減。在風速Ua = 3 m/s下，同向風場(θ = 0)會使粒徑dp = 10 μm液滴在距離 x/D = 30處，濃度變為C/C ≈ 0.2；逆向風場(θ = 180)下，則使濃度在x/D = 15處降為C ≈ 0。由於側風與重力的共同作用下，滴徑dp = 100 μm在橫向風(θ = 90)，s/D = 60處的濃度幾乎是同向風狀況下的兩倍。此外，液滴蒸發速率會隨粒徑增加而明顯變小，液滴粒徑由10 μm增加至粒徑100 μm時，蒸發速率約降一個數量級。這些研究結果提供室內通風設計與傳染風險控制重要的規範依據。;This study employed a Large Eddy Simulation (LES) model and a Lagrangian particle tracking method to simulate droplet jets in windy environments. The simulation results were validated against the results of wind tunnel experiments. The simulation results reveal that the jet width decreased from 14D to 4D (D: nozzle diameter) as the crosswind (wind direction θ = 90) velocity increased from 1 m/s to 6 m/s. When Ua/Ujet > 0.3, the particle distributions shifted from twin- to single-peak, indicating that jet bifurcation was suppressed in higher wind velocity. Additionally, particle size affects the droplet distribution. The concentration exhibits a twin-peak distribution for droplet diameters of dp = 1-10 μm; an asymmetric profile for dp = 100-200 μm; and a rapid decay concentration for dp = 500 μm. Under co-current wind condition (Ua = 3 m/s, θ = 0), the concentration reaches C/C ≈ 0.2 at a distance of x/D = 30; while under counter-current wind (Ua = 3 m/s, θ = 180); the concentration drops to C = 0 at x/D = 15. Due to the combined effects of crosswind and gravity, the concentration of droplets size dp = 100 μm under crosswind (θ = 90) at s/D = 60 is nearly twice that observed under co-current winds. Furthermore, the droplet’s evaporation rate decreases with increasing droplet size, dropping by an order of magnitude when the diameter increases from 10 μm to 100 μm. These findings provide insights for indoor ventilation and infection risk control strategies.
