Pergamon 0021-8502(94)00105-7 J. Aerosol $ci., VoL 26, No. 2, pp. 187-199, 1995 Copyright © 1995 Elaevier Science Ltd Printed in GreatBritain. All rightsresm-ved 0021-8502/95 $9.50 + 0.00 AGGLOMERATE STRUCTURE AND GROWTH RATE BY TRAJECTORY CALCULATIONS OF MONOMER-CLUSTER COLLISIONS Andreas Gutsch, Sotiris E. Pratsinis* and Friedrich L6ffler Institut fiir Mechanische Verfahrenstechnik und Mechanik, Universit/it Karlsruhe (TH), D-76128 Karlsruhe, Germany (First received 10 October 1993; and in final form 18 July 1994) A~tract--The evolution of the detailed structure of agglomerate particles made by monomer- cluster coagulation is described by single-particle trajectory calculations based on the "Langevin differential equation". This method is used also to determine the collision frequency between agglomerate and spherical particles undergoing Brownian coagulation from the free molecular to the continuum regime. A new analytical function is proposed for the collision frequency between agglomerate and spherical particles. NOMENCLATURE a stochastic acceleration A stochastic acceleration cv aerosol volume concentration C Cunningham correction df volume-based fractal dimension d~ diameter of particle i d=~, diameter of the smallest particle Fex t external force Fi. j inter-particle force G mean squared value of velocity H mean squared value of velocity and location i number of primary particles I mean squared value of location J stationary particle flux kB Boltzmann's constant k,~. ~ collision frequency of agglomerate and sphere of size j k,. j collision frequency of spheres of size and j k~.,o n collision frequency of sphere of size i and collector particle Kn Knudsen number m particle mass m,,~, mass of the smallest particle n number of collisions N number concentration rp primay particle radius r distance R stochastic location vector t time t~ collision time tm,a, mean collision time T temperature v particle velocity V stochastic velocity vector w fluid velocity X bivariate probability variable Y Gaussian probability variable Greek letters /3 friction coefficient * On sabbatical leave from the Department of Chemical Engineering, University of Cincinnati, Cincinnati, OH 45221-0171, U.S.A. 187