在新冠病毒（COVID-19）疫情大流行的背景下，了解病原體在空氣中的傳播行為對於控制流行病至關重要。本研究的目的是通過實驗和數值模擬的方法，探討橫向流對射流中液滴分布和傳播的影響。我們藉由風洞實驗和大渦流模擬（LES）模式，針對不同風速和風向下射流的速度場和濃度場進行了研究。實驗在國立中央大學的風洞設施中進行，使用了不同的橫向流速度和射流速度，並測量了不同位置的射流速度和液滴濃度。模擬結果與實驗數據比對驗證，顯示出良好的一致性。研究結果表明，橫向流的存在顯著影響射流中的液滴濃度分布，在相同距離處(s/D ≈ 10)濃度約為無橫向流的37%。較大的液滴(dp ≥ 100 μm)由於慣性作用，受橫向流的影響較小，沿射流方向保持較高的濃度；而較小的液滴(dp ≤ 10 μm)則更容易被橫向流的影響，分散範圍更廣，相同距離處(s/D ≈ 10D)，粒徑dp = 10 μm的濃度，約為粒徑dp = 100 μm的25%。實驗和模擬還顯示了射流與橫向流之間的複雜相互作用，特別是在非平行風向下，射流出現了分叉現象，形成了雙峰分布。這些結果對噴嚏中液滴和氣溶膠的傳播行為，提供了深入的理解和應用價值。;In the context of the COVID-19 pandemic, understanding the transmission behavior of pathogens in the air is crucial for controlling epidemics. This study aims to explore the impact of crosswind on droplet dispersion in sneeze-induced jet flows through experimental and numerical simulations. The laboratory experiments were performed in the wind tunnel facility of National Central University, and the jet velocities and droplet concentrations were measured under various wind speeds and directions. The experimental results are used to validate the simulation of a Large Eddy Simulation (LES) model. The crossflow could reduced the droplet concentration of the jet flow about 37% at the same distance (s/D ≈ 10). The simulation results indicate that the larger droplets (dp ≥ 100 μm) due to their inertia, are less likely to be influenced by the crosswind and maintain higher concentrations along the jet direction. Whereas smaller droplets (dp ≤ 10 μm) are easier to be carried by the crosswind, resulting in a wider dispersion and lower concentration. The particle concentration for with a diameter dp = 10 μm is approximately 25% (s/D ≈ 10) of that for the particles with a diameter dp = 100 μm. The numerical simulations also reveal the complex interactions between jet flows and crosswind, particularly under non-parallel wind directions, where the jet flow bifurcates, forming a twin-peak concentration distribution. These findings provide valuable insights into the behavior of droplets in jet flows under crosswind conditions.
