Particle-turbulence interaction in dilute suspensions
Karema, H
42 ENGINEERING; PARTICLES; TURBULENCE; TURBULENT FLOW; EQUATIONS OF MOTION; SUSPENSIONS; FLOW MODELS; TWO-PHASE FLOW; 420400; HEAT TRANSFER AND FLUID FLOW
The interaction between particles and fluid turbulence in dilute suspensions is studied in this work. It is done by dividing the problem into two separate issues where the first one treats the response of a particle to fluid turbulence and the second one the modification of fluid turbulence caused by the particles. The ideas developed on the basis of these two issues are then used to analyse the transversal mixing rate of a passive scalar in an upward fully developed flow of a gas-particle suspension. Special interest in this case is in the capability of the gradient-diffusion model to predict the experimentally obtained changes in the mixing rate. The intention of this work is to indicate the most important parameters of the particle-turbulence interaction with their individual effects. It is done on the base of currently available and verified results intentionally avoiding advanced speculations. Because of the long term interest in a common frame-work of dilute and dense suspension the emphasis is on an Eulerian approach. The governing phenomenon in the turbulent dispersion of particles is the effect of crossing trajectories caused by the drift velocity. The resulting particle diffusion coefficient is considerably lower than the corresponding fluid point diffusion coefficient. Particle inertia has minor importance in producing a slight increase in diffusion coefficient. The importance of the two parameters of interaction, the ratio of the particle diameter to the integral length scale of the fluid and the particle Reynolds number, are strongly supported by experimental observations and theoretical hypothesis. According to these guide lines small particles tend to attenuate turbulence and large particles tend to augment it
Tampere Univ. of Technology (Finland). Thermal Engineering
OSTI; NTIS
Finland
1994-12-31
English
Technical Report
Other Information: PBD: 1993
Medium: X; Size: 79 p.
ON: DE95737624; ISBN 951-722-078-2
TTKK-LT-92
Other: ON: DE95737624; ISBN 951-722-078-2; TRN: FI9503086
FI; SCA: 420400; PA: FI-95:003086; EDB-95:030680; SN: 95001320438
2008-02-12
10115079