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.
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