Investigating the characteristics of aerosol trajectory models and the deposition mechanisms of aerosols in the inlet region

• Main Authors: Lin,Ching-Ho, 林清和
• Other Authors: Chang,Len-Fu W.
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/94249028970868642409

博士 === 國立臺灣大學 === 環境工程研究所 === 84 === The contents of this thesis have three major parts: (1) the analysis of dispersion properties inherent in numerical particle trajectory models, (2) simulations of developing turbulent flow in the inlet region of a pipe and the evaluations of inflow turbulence effects on the development of the turbulent flow, and (3) deposition mechanisms and concentration distribution of aerosol particles in the inlet region of a pipe. For the first, nine particle trajectory models were investigated. Based on the mechanisms with each model, the dispersion properties inherent in each models were derived in homogeneous turbulence. How to choice the time interval associated with each model so as to confirm some theoretical results were suggested. In addition, the influences of relaxation time and initial velocity of particle on the particle dispersion were examined. In simulating the developing turbulent flow, we first evaluated the performances of six versions of turbulence models. The results revealed that most models have excellent simulations of the mean velocity; however some discrepancies were found in predicting the turbulent kinetic energy and Reynolds stress in the inlet region. The variations of inflow turbulence had little influence to the develop of boundary layers. In investigating the deposition mechanisms, the results shown that turbulence and lift force are the most important mechanisms to arise the deposition of aerosol particle in the inlet region. The magnitude of inflow turbulent intensity influences the particle depositions deeply; however the turbulent length and time scale have little influence on the particle deposition. And, the turbulent boundary and the turbulence in the free stream are reverent to the distributions of particle concentrations in the inlet region.