Engineering, 2015, 7, 597-609 Published Online October 2015 in SciRes. http://www.scirp.org/journal/eng http://dx.doi.org/10.4236/eng.2015.710054 How to cite this paper: Saber, A., Lundström, T.S. and Hellström, J.G.I. (2015) Turbulent Modulation in Particulate Flow: A Review of Critical Variables. Engineering, 7, 597-609. http://dx.doi.org/10.4236/eng.2015.710054 Turbulent Modulation in Particulate Flow: A Review of Critical Variables Ammar Saber 1,2 , T. Staffan Lundström 1 , J. Gunnar I. Hellström 1 1 Fluid and Experimental Mechanics Division, Luleå University of Technology, Lulea, Sweden 2 Mechanical Engineering Department, University of Mosul, Mosul, Iraq Email: ammar.hazim@ltu.se , staffan.lundstrom@ltu.se , gunnar.hellstrom@ltu.se Received 29 July 2015; accepted 13 October 2015; published 16 October 2015 Copyright © 2015 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract A review of the main mechanisms influencing turbulent modulation in the presence of spherical and non-spherical particles is presented. The review demonstrates the need for more numerical and experimental work with higher accuracy than obtained so far and the need to resolve the flow near the surface of particles with the aim to re-evaluate the quantitative effect of different para- meters on turbulent modulation. The review reveals that non-spherical particles have more ad- verse effect on turbulence as compared to spherical ones, for the same ambient conditions. Keywords Two Phase Flow, Turbulent Modulation, Non-Spherical Particle, Stokes Number, Particle Reynolds Number, Length Scale, Density Ratio 1. Introduction Turbulent flows can be found everywhere in nature and industry, but a unifying theory of turbulence does not exist. When spherical particles are suspended into such a flow, the flow becomes even more intricate and the resulting interactions between the particles and turbulent structures are not fully understood. For non-spherical particles that often appear in fluids in industrial processes, like paper making, iron ore pelletization, pneumatic conveying [1], cyclone filters [2] [3], and biomass gasification and combustion, the interactions of the particles and the fluid in turbulent flow are extremely complex while theories exist for creeping flow [4]-[8]. In turbulent flow, the particles will wobble or move chaotic, depending on their size and density [9]. Hence, the carrier phase turbulence alters the dispersed phase translational and rotational motion and the particles influence the detailed and overall flow of the carrier phase. It is important to study turbulent modulation, or in other words the influence of the dispersed phase on the