Effect of near-wall turbulence enhancement on the mechanisms of particle deposition

被引:12
作者
Botto, L
Narayanan, C
Fulgosi, M
Lakehal, D [1 ]
机构
[1] ETH, Swiss Fed Inst Technol, Inst Energy Technol, CH-8092 Zurich, Switzerland
[2] Univ Udine, Dept Energy Technol, Udine, Italy
关键词
particle tracking; deposition; turbulence;
D O I
10.1016/j.ijmultiphaseflow.2005.05.003
中图分类号
O3 [力学];
学科分类号
08 ; 0801 ;
摘要
The modification of deposition mechanisms of small particles in wall turbulence due to enhanced near-wall fluctuations is presented. The direct numerical simulation database of turbulent air flow over a water surface populated by gravity-capillary waves of small wave slope was used to mimic the enhancement in fluctuation intensity. Lagrangian tracking of particles is performed under the assumption of one-way coupling between the particles and the flow. Two sets of particles have been considered with inertial response times of 5 and 15, respectively, normalized using the friction velocity at the air-water interface and the kinematic viscosity of air. Compared to wall-bounded flow, the particle deposition rates on the interface were found to be considerably higher; specifically for the low-inertia particles, an eightfold increase was observed. The deposition rate for particles of higher inertia increased by only 60%. The correlation characterizing particle deposition rates for wall-bounded flows, where the deposition rate is proportional to the square of the particle response time, was found to be invalid for the flow with enhanced near-wall turbulence. Comparison with experimental results on particle deposition onto rough walls showed better correlation. Depositing particles were divided into free-flight and diffusional deposition populations. Since the primary effect of the interfacial waves is to increase the turbulence intensity in the near-interface region with high particle concentration, a remarkable increase in diffusional deposition is observed. As in wall-bounded flows, diffusional deposition is seen to be the dominant mechanism of deposition. The free-flight mechanism, where particles acquire velocities high enough to travel directly to the interface, remains unaffected by enhanced near-wall velocity fluctuations. (c) 2005 Elsevier Ltd. All rights reserved.
引用
收藏
页码:940 / 956
页数:17
相关论文
共 28 条
[1]   TURBULENT DEPOSITION AND TRAPPING OF AEROSOLS AT A WALL [J].
BROOKE, JW ;
KONTOMARIS, K ;
HANRATTY, TJ ;
MCLAUGHLIN, JB .
PHYSICS OF FLUIDS A-FLUID DYNAMICS, 1992, 4 (04) :825-834
[2]   FREE-FLIGHT MIXING AND DEPOSITION OF AEROSOLS [J].
BROOKE, JW ;
HANRATTY, TJ ;
MCLAUGHLIN, JB .
PHYSICS OF FLUIDS, 1994, 6 (10) :3404-3415
[4]   SUB LAYER MODEL FOR DEPOSITION OF PARTICLES FROM A TURBULENT-FLOW [J].
CLEAVER, JW ;
YATES, B .
CHEMICAL ENGINEERING SCIENCE, 1975, 30 (08) :983-992
[5]  
CLIFT R, 1978, BUBBLE DROPS PARTICL
[6]   Direct numerical simulation of turbulent flow over a wavy wall [J].
DeAngelis, V ;
Lombardi, P ;
Banerjee, S .
PHYSICS OF FLUIDS, 1997, 9 (08) :2429-2442
[7]   DIRECT SIMULATION OF PARTICLE DISPERSION IN A DECAYING ISOTROPIC TURBULENCE [J].
ELGHOBASHI, S ;
TRUESDELL, GC .
JOURNAL OF FLUID MECHANICS, 1992, 242 :655-700
[8]   DEPOSITION OF AEROSOL-PARTICLES FROM TURBULENT-FLOW ONTO ROUGH PIPE WALL [J].
ELSHOBOKSHY, MS ;
ISMAIL, IA .
ATMOSPHERIC ENVIRONMENT, 1980, 14 (03) :297-304
[9]   EXPERIMENTAL MEASUREMENTS OF AEROSOL DEPOSITION TO SMOOTH AND ROUGH SURFACES [J].
ELSHOBOKSHY, MS .
ATMOSPHERIC ENVIRONMENT, 1983, 17 (03) :639-644
[10]   DEPOSITION OF SUSPENDED PARTICLES FROM TURBULENT GAS STREAMS [J].
FRIEDLANDER, SK ;
JOHNSTONE, HF .
INDUSTRIAL AND ENGINEERING CHEMISTRY, 1957, 49 (07) :1151-1156