DEM Simulation of the Impact of Ultrafine Glass Particles on the Partition Wall of the Multichannel Cyclone RAIMONDAS JASEVIC ˇ IUS, 1,2 PRANAS BALTRE ˙ NAS, 1 RIMANTAS KAC ˇ IANAUSKAS, 3 and RAIMONDAS GRUBLIAUSKAS 1 1 Research Institute of Environmental Protection, Vilnius Gediminas Technical University, Vilnius, Lithuania 2 Department of Software Engineering, Vilnius University, Vilnius, Lithuania 3 Institute of Mechanics, Vilnius Gediminas Technical University, Vilnius, Lithuania This article focuses on the simulation of the impact of ultrafine particles on the rigid partition wall of the multichannel cyclone by applying the discrete element method (DEM). Ultrafine particles with diameters ranging from 0.1 to 10 mm are assumed to be most dangerous pollutants because of their property to easily penetrate the human circulatory system through the respiratory tract. An emphasis is placed on demonstrating the stick-rebound behavior of glass pollutant particles. The numerical experiment simulating the oblique impact load induced by mechanically generated inlet air flow has been numerically conducted. Hertz contact and short-range van der Waals attraction are the main forces describing normal contact, while their tangential counterpart is defined according to Coulomb friction law and by considering normal compression and attraction. Both normal and tangential models are modified to comprise the effect of energy dissipation due to adhesion hysteresis. Simulation results provide a theoretical framework for designing of the cyclone when a device is applied to capture ultrafine pollutant particles. Keywords: Adhesion, critical velocity, DEM, microparticles, multichannel cyclone, oblique impact Introduction Ultrafine particles (0.1–10 mm) are supposed to be the most dangerous due to their property to easily enter the human circulatory system through the respiratory tract (Herring et al. 2013). Because of the low weight of the particles, air cleaning devices encounter severe difficulties in catching them. Therefore, the evaluation of particle behavior is a crucial aspect. In order to gain higher air cleaning effective- ness, the assessment of pollutant behavior is important for designing air cleaning devices (Hoffmann 2000; Baltre ˙nas and Zagorskis 2010; Vaitieku ¯nas and Jak stoniene ˙ 2010; Pushnov and Berengarten 2011; Baltre ˙nas et al. 2012; Luca and Ioan 2012). Microparticles in the above-introduced equipment most frequently precipitate under the influence of sedimentation processes taking place in the multichannel cyclone and stick to the partition wall of the device. Since the size of the particles decreases, various field forces start con- tributing to inter-particle behavior. Therefore, the interac- tion between the ultrafine particles and the partition wall must be properly assessed. While omitting the physical aspects of intermolecular van der Waals attraction, we simply remind that a discussion on normal single-asperity interaction dates back to two models. One of those presented by Johnson, Kendall, and Roberts (Johnson et al. 1971), or the JKR model, assumes that the attraction between particles is of an infinitely short range and acts only over the contact area. The model developed by Derjaguin, Muller, and Toporov (Derjaguin et al. 1975), or the DMT model, predicts that a half of interaction force occurs in the outside located annular area at the perimeter closed by the contact. Different approaches and various illustrations of bilateral adhesive interactions have been provided by Thornton (1991), Dominik and Tielens (1997), Johnson (1998), Sridhar and Sivashanker (2003), Tomas (2004, 2007a, 2007b), Brilliantov et al. (2007), Luding (2008), and Severson et al. (2009). The characterization of tangential behavior during the oblique impact in the presence of van der Waals forces is even more complicated than normal interaction. A detailed study on the action of adhesion force on tangential slip was first made by Savkoor and Briggs (1977). Beek et al. (2006) published the findings of experimental research on the oblique impact of a 50 mm particle on the background. The paper proposed the relationship between the coefficient of friction and the impact angle. Ibrahim et al. (2004) ana- lyzed the rebound of metal particles from the glass surface under turbulent air flow. Konstandopoulos (2006) studied the effect of adhesion under an oblique impact of an aerosol particle on a cylindrical-spherical collector. Address correspondence to: Raimondas Jasevic ˇius, Research Institute of Environmental Protection, Vilnius Gediminas Technical University, Saule ˙tekio Ave 11, Lithuania. E-mail: raimondas.jasevicius@vgtu.lt Particulate Science and Technology, 32: 576–587 Copyright # 2014 Taylor & Francis Group, LLC ISSN: 0272-6351 print=1548-0046 online DOI: 10.1080/02726351.2014.933145