Study On The Dust Suppression Property And Mechnism Of The Porous Fence With Deflectors

Porous fence,which is an effective method to abate dust emission,has been used for many practical applications and aroused extensive attention in academic fields.In this paper,the commercial software of CFD,Fluent,was used to simulate the flow field behind the porous fence with deflectors on the base of the previous studies.Simultaneously,the wind tunnel experiment was made to verify the simulated results.Besides,the DPM model from Fluent software was employed to predict the moving tracks of particles behind the wind fence.The expression of shearing force acting on single particle on the slope was also deduced by refering to the Shields criterion.The detailed work of this paper is as follows:The velocities in the flow field was measured by wind tunnel experiment under different oncoming velocities and different porosities(20%、30%、40%、50%).The analysis of the measurement results showed that the new form porous fence had a good performance on weakening wind erosion.When the velocity of oncoming flow was 10 m·s-1,the minimum velocity behind the fence decreased to 2 m·s-1 reduced by 80 percent.In additon to reduce the velocity behind the fence,the fence also weakened the velocity before the fence.Compared with other porosities,the fence with 30%porosity had best performance.Three different turbulence models(Standard k-ε model、RNG k-s model、Realizable k-ε model)were developed to simulate the flow field behind the porous fence with deflectors.The simulated results were compared with the observational data.The results showed that the simulation of the three models had slight difference.The performance of any of these models against the wind tunnel data was basically identical.The simulated data in y<2h area was particully good against the experimental data while it was not good in y>2h area.On the whole,standard k-εand realizable k-ε turbulence models had better performance than RNG k-εturbulence model.The dust suppression property of the new form porous fence was studied by using the standard k-s turbulence model in order to investigate the influence on the prism surface by changing porosity,fence height and location of the wind fence.In addition,the study on the performance of three different kinds of porous fences was carried out.According to the simulated results,the porous fence with a porosity of 30%,height of 150mm and location of 150mm,as well as the wind fence with deflectors totally installed,seems to be most efffective in attenuating the pressure,velocity and turbulence intensity acting on the prism surface.Using discrete phase model,moving tracks of the particles with different diameters on the prism behind the wind fence were predicted based on the above-mentioned simulations.The results indicated that the movements of the small size particles were more stochastic due to the influence of the bleed flow region and the quiet zone.However,with the increase of the particle size,the movements became more regular.The expression of shearing force acting on the single particle on the slope manifested that the shearing force was a function of particle Renolds number.When the slope angle was 0°,the expression converted to criterion of horizontal surface.