摘要
Particle coagulation by Brownian motion is an important but difficult research topic.When particle volume concentration is larger than 0.1%,the classic SMOLUCHOWSKI equation is not applicative anymore.The high concentration coagulation,with HEINE＇s correction,source terms for the Taylor-series expansion method of moments（TEMOM） are firstly driven in this paper.Ultra-fine particle（d0？100 mm） with initial volume fraction f？1% coagulation in a planar jet turbulence flow is simulated via the large eddy simulation（LES）.The instantaneous and time-averaged particle distributions and the high concentration enhancement are given out.The particle number concentration distribution results show that the coagulation is more intense comparing to dilute case in previous research,especially near the nozzle exit.After jet flow is fully developed,the effect is much more obvious at the region between vortexes.The time-averaged γ（the high concentration enhance factor） distributes sharply and symmetrically about the jet centerline at the upstream,but becomes broad and flat at downstream where the cross-stream averaged γ fluctuates drastically.As a new attempt,this paper shows Brownian coagulation with high concentration also can be calculated via TEMOM appropriately,and the coagulation at the region between vortexes is about 1.38 times intensive of the dilute result calculated by the classic Smoluchowski theory.
Particle coagulation by Brownian motion is an important but difficult research topic.When particle volume concentration is larger than 0.1%,the classic SMOLUCHOWSKI equation is not applicative anymore.The high concentration coagulation,with HEINE＇s correction,source terms for the Taylor-series expansion method of moments（TEMOM） are firstly driven in this paper.Ultra-fine particle（d0？100 mm） with initial volume fraction f？1% coagulation in a planar jet turbulence flow is simulated via the large eddy simulation（LES）.The instantaneous and time-averaged particle distributions and the high concentration enhancement are given out.The particle number concentration distribution results show that the coagulation is more intense comparing to dilute case in previous research,especially near the nozzle exit.After jet flow is fully developed,the effect is much more obvious at the region between vortexes.The time-averaged γ（the high concentration enhance factor） distributes sharply and symmetrically about the jet centerline at the upstream,but becomes broad and flat at downstream where the cross-stream averaged γ fluctuates drastically.As a new attempt,this paper shows Brownian coagulation with high concentration also can be calculated via TEMOM appropriately,and the coagulation at the region between vortexes is about 1.38 times intensive of the dilute result calculated by the classic Smoluchowski theory.
基金
supported by National Natural Science Foundation of China (Grant No. 50976107)
National Key Technology R&D Program of China (Grant No. 2009BAF39B01)
the Science Foundation of Zhejiang Sci-Tech University (ZSTU) of China (Grant No. 1003808-Y)
