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TURBULENCE MODULATION IN PARTICLE-LADEN CHANNEL FLOW

Lihao Zhao
Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, Norway

Helge I. Andersson
Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, Norway

Jurriaan J. J. Gillissen
J. M. Burgerscentrum, Department of multi scale physics Delft University of Technology, 2628CA Delft, The Netherlands

Аннотация

Particle suspensions have been studied extensively for several decades since such flows are common both in the environment and in a variety of industrial fields. The present work aims to investigate the modulations on the turbulence of the carrier fluid due to the presence of tiny inertial spherical particles in a turbulent channel flow, especially the influences of the particle volume fraction and the particle response time. Five cases with different particle loadings and response times were studied and the comparisons between the particle-laden flows and a particle-unladen channel flow were made. The results of the cases with large response times or particle loadings indicate that the presence of the particles leads to an increase of the mean bulk velocity in the channel flow. Additionally, the streamwise turbulent fluctuations is augmented whereas the spanwise turbulent fluctuations and, in particular, the Reynolds shear stress are attenuated compared with the unladen flow. Moreover, the small-scale eddies around walls have been damped and the flow comprises larger eddies than a flow without particles. However, the cases with small amounts of particles or low particle response times did not show obvious modulations on turbulence. To explore in detail the interaction between the particles and fluid, the kinetic energy conversion was examined by means of conditional averaging. The analysis of the mechanical energy transfer between the fluid phase and the particles indicates the particles redistribute the kinetic energy inside flow, i.e. receiving the kinetic energy from fluid in the central channel but transferring the kinetic energy back to the fluid close to the wall regions..