Porosity is the most important parameter affecting the efficient of fences, however, the distinct shelter regions varied with different porosity. At high porosities (ε30.3), the dust emission in the middle and lower parts of the pile over the fence decreased significantly, while the shelter mainly reflected in the upper part at low porosities (ε < 0.3). Obtaining effective protection on each site, this research introduced, based on the reduction region of the uniform porosity, a new combination of non-uniform fence with different porosities for the upper and lower halves. The flow flied behind a porous fence was numerically simulated by software Fluent6.3with six typical combinations of the non-uniform fence. Results showed that when the lower fence porosity of the fence (εL) kept consistent and the upper fence porosity (εH) transformed from 0to 0.1, the airflow turbulence weakened distinctly. Considering turbulence structure and stress of the pile, the fence with the upper porosity εH= 0.1was more accepted. Meanwhile, when the upper porosity (εH) remained identical, and the lower porosity (εL) increased from 0.3to 0.6,the speed of attached flow along the surface increased with the increasing porosity, therefore, the optimum porosity of the lower half fence (εL) was set to 0.3. The shelter effect of non-uniform fence was estimated by comparing the preferred combination (εH=0.1/εL=0.3)with uniform fence porosity ε=0.1 and ε=0.3. The analysis indicated the non-uniform porous fence (εH=0.1/εL=0.3) seemed to be the most effective in abating the dust emission, especially in reducing the shear stress of the windward which aroused the maximum dust emission. The shear stress of the non-uniform porous fence, in the middle and lower part, decreased by 85.2% for the uniform fence with porosity ε=0.1, and 84.3% in the upper part for the fence with the porosity ε=0.3, respectively. Besides, the non-uniform porous fence (εH=0.1/εL =0.3) could reduce the surface shear force on the pile around 50% for the two uniform fences.
何鸿展, 宋翀芳, 潘武轩, 雷勇刚. 基于CFD的防风抑尘网非均匀孔隙率的优化研究[J]. 中国环境科学, 2016, 36(6): 1697-1704.
HE Hong-zhan, SONG Chong-fang, PAN Wu-xuan, LEI Yong-gang. Non-uniform porosity design optimization based on CFD simulation for porous fences. CHINA ENVIRONMENTAL SCIENCECE, 2016, 36(6): 1697-1704.
Hao J M, Wang L T, Li L, et al. Air pollutants contribution and control strategies of energy-use related sources in Beijing [J]. 中国科学d辑(英文版), 2005,48(SII):138-146.
[2]
Bi X H, Feng Y C, Wu J H, et al. Source apportionment of PM10 in six cities of northern China [J]. Atmospheric Environment. 2007,41(5):903-912.
[3]
王 鑫,浦 伟,史晋森,等.A comparison of the physical and optical properties of anthropogenic air pollutants and mineral dust over Northwest China [J]. Journal of meteorological research, 2015,29(2):180-200.
Cong X C, Cao S Q, Chen Z L,et al. Impact of the installation scenario of porous fences on wind-blown particle emission in open coal yards [J]. Atmospheric Environment, 2011,45(30): 5247-5253.
[8]
Park C W, Lee S J. Verification of the shelter effect of a windbreak on coal piles in the POSCO open storage yards at the Kwang-Yang works [J]. Atmospheric Environment, 2002,36(13): 2171-2185.
[9]
Chen G H, Wang W W, Sun C F,et al. 3D numerical simulation of wind flow behind a new porous fence [J]. Powder Technology, 2012,230:118-126.
Li B L,Sherman D J. Aerodynamics and morphodynamics of sand fences, A review [J]. Aeolian Research, 2015,17:33-48.
[12]
Zhang N, Lee S J, Chen T G. Trajectories of saltating sand particles behind a porous fence [J]. Geomorphology, 2015,228: 608-616.
[13]
Hong S W, Lee I B, Seo I H. Modelling and predicting wind velocity patterns for windbreak fence design [J]. Journal of Wind Engineering & Industrial Aerodynamics, 2015,142:53-64.
Kim H B, Lee S J. Hole diameter effect on flow characteristics of wake behind porous fences having the same porosity [J]. Fluid Dynamics Research, 2001,28(6):449-464.
[16]
Bofah K K, Al-Hinai K G. Field tests of porous fences in the regime of sand-laden wind [J]. Journal of Wind Engineering & Industrial Aerodynamics, 1986,23:309-319.
[17]
Heisler G M,Dewalle D R. Effects of windbreak structure on windflow [J]. Agriculture Ecosystems & Environment,1988,22/ 23:41-69.
Yaragal S C, Ram H S G, Murthy K K. An experimental investigation of flow fields downstream of solid and porous fences. Journal of Wind [J]. Engineering & Industrial Aerodynamics, 1997,66(2):127-140.
[20]
Lee S J, Lim H C. A numerical study on flow around a triangular prism located behind a porous fence [J]. Fluid Dynamics Research, 2001,28(3):209-221.
Dong Z B, Luo W Y,Qian G Q,et al. A wind tunnel simulation of the turbulence fields behind upright porous wind fences [J]. Journal of Arid Environments, 2010,74(2):193-207.
[23]
Ferreira A D, Lambert R J. Numerical and wind tunnel modeling on the windbreak effectiveness to control the aeolian erosion of conical stockpiles [J]. Environmental Fluid Mechanics, 2011, 11(1):61-76.
Park C W, Lee S J. Experimental study on surface pressure and flow structure around a triangular prism located behind a porous fence [J]. Journal of Wind Engineering & Industrial Aerodynamics, 2003,91:165-184.
[26]
Alhajraf S. Computational fluid dynamic modeling of drifting particles at porous fences [J]. Environmental Modelling & Software, 2004,19(2):163-170.
[27]
Bitog J P, Lee I B, Shin M H, et al. Numerical simulation of an array of fences in Saemangeum reclaimed land [J]. Atmospheric Environment, 2009,43(30):4612-4621.
[28]
Diego I, Pelegry A, Torno S, et al. Simultaneous CFD evaluation of wind flow and dust emission in open storage piles [J]. Applied Mathematical Modelling, 2009,33(7):3197-3207.
[29]
Turpin C, Harion J L. Numerical modeling of flow structures over various flat-topped stockpiles height: Implications on dust emissions [J]. Atmospheric Environment, 2009,43(35):5579-5587.
Launder B E, Spalding D B. The numerical computation of turbulent flows [J]. Computer Methods in Applied Mechanics & Engineering, 1974,3(2):269-289.
[33]
Farouk B, Guceri S I. Laminar and turbulent natural convection in the annulus between horizontal concentric cylinders [J]. Journal of Heat Transfer, 1982,104(4):631-636.
Elghobashi S E, Pun W N, Spalding D B. Concentration fluctuation in isothermal turbulent confined coaxial jets [J]. Chemical Engineering Science,1977,32(2):161-166.
[37]
Patankar S V, Sparrow E M, Ivanovic M. Thermal interactions among the confining walls of a turbulent recirculating flow [J]. Internation Journal Heat & Mass Transfer, 1978,21(3):269-274.
[38]
董纪鹏.强风流过散堆料场的流场模拟与抑尘研究 [D]. 青岛:青岛科技大学, 2009.
[39]
Giannoulis A, Mistriotis A, Briassoulis D. Experimental and numerical investigation of the airflow around a raised permeable panel [J]. Journal Wind Engineering & Industrial Aerodynamics, 2010,98(12):808-817.