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.
LIN PeifengWU DichongYU MingzhouWANG ChaoZHANG LiteZHU Zefei
The motion of micro-particles with different mass flow rate in the planer turbulent jet flow has been simulated,using LES method to obtain the flow vorticity evolution and Lagrangian method to track micro-particles.The results showed that when the flow rate is small,the particles more likely to present in the vortex periphery,the distribution pattern is similar to the flow pattern.When the flow rate is high,some particles will escape from the motion region to the original static region,so that in the jet region,particles are relatively evenly distributed.When the flow field is full developed,the particles average concentration in the y direction affected by the mass flow rate relative slightly,the normalized mean particles concentrations at different flow rate were similar to Gaussian shape.
