多區間建築物室內懸浮微粒傳輸機制之數值研究

Abstract

本研究之主要目的是以拉格蘭日(Lagrangian)觀點的氣懸微粒軌跡追蹤模式，來模擬多區間建築物室內氣懸微粒傳輸之力學機制。室內環境風場模擬模式係以尤拉（Eulerian）觀點進行風場之境況模擬，使用k-ε紊流模式以計算紊流場。微粒軌跡追蹤模式在計算微粒受力之時，除了傳統採用的阻力與重力外，又增加考慮Saffman昇力與布朗運動作用力對於微粒的影響。本研究首先分析微粒釋放數對質量濃度與粒數濃度計算之影響。模式模擬結果並透過與前人試驗數據的比對，發現在質量濃度的模擬方面準確性相當高。最後模式釋放足夠的微粒數來模擬微粒的傳輸機制。 本研究繼而探討不同粒徑下微粒傳輸的力學機制，將微粒氣動直徑大小依序分為10μm、5μm、2.5μm、1μm、0.5μm、0.1μm、0.05μm等七組。每種粒徑探討阻力、重力、Saffman昇力、布朗運動作用力對微粒傳輸行為的影響。在比較以上各種不同的受力狀況後，隨著微粒粒徑的減小，阻力對其微粒軌跡的影響也依序變小；當微粒粒徑達到0.1μm時，阻力的影響已趨近於零。而昇力的重要性在微粒粒徑介於5μm和2.5μm之間時對微粒軌跡比較明顯，且在微粒粒徑5μm時，昇力的重要性達到最大。在微粒粒徑大於1μm時，布朗運動對微粒軌跡是毫無影響的，而當微粒粒徑小於0.5μm時，布朗運動的考慮與否對微粒傳輸軌跡則會相當的重要。

The main purpose of this research is to investigate the mechanism of airborne particulate matter transport in ventilated multi-room environment from a Lagrangian particle trajectory tracking technique. The flow field is simulated by using the k-ε turbulence model. We not only add the drag force and the gravitational force into the Lagrangian particle tracking model, but also consider the Brownian motion effect and Saffman lift force. Our study first analyzes how the numbers of particle released affect the mass and count concentrations. The numerical model is next verified by the reliable experimental measurement of Lu et al. (1996). The particle mass concentration are in good agreement with the experimental data. Our study includes six scenarios for the particle diameters of 10μm, 5μm, 2.5μm, 1μm, 0.5μm, 0.1μm and 0.05μm to investigate the transport mechanism of airborne particulate matter. For each particle diameter, we apply the drag force, gravitational force, Brownian motion and Saffman lift force in simulating airborne particle transport. The numerical results show that the smaller particle diameter is, the little influence of the drag force is. When particle diameter reaches 0.1μm, the influence of the drag force approach to zero. The Saffman lift force is significantly important to particle trajectory for the particle diameter ranging from 5μm to 2.5μm, and the Saffman lift force is the most important mechanism to the particle diameter of 5μm. Furthermore, the Brownian motion has no effect on particle trajectory for the particle diameter greater than 1μm. And the particle trajectory simulation must take account of the Brownian motion effect for the particle diameter smaller than 0.5μm.