煤尘表面摩擦风速的计算方法

Calculation on wind-blown friction velocity passing mine piles

露天煤场风蚀扬尘量的估算需要确定煤尘表面的摩擦风速.采用数值计算方法,通过对风蚀作用下煤垛流场的计算,得出煤垛各细小表面处的摩擦风速.当风速为3.3 m/s时,计算得出最大摩擦风速为0.168 m/s,最小为0.063 m/s,平均0.110 m/s.当外界风速增至10.0 m/s时,煤垛各表面摩擦风速随之增大。各表面平均风速为0.294 m/s.计算结果与文献风洞实验值吻合很好,表明其计算的可信性.根据EPA排放模式,以年均风速3.3 m/s,每3 d扰动1次的11万m^2的煤场为例,计算统计结果:煤垛表面起尘率为14.5%,风蚀扬尘量为671.4 t/a,这与实际煤场每年的煤尘风蚀损失量约700 t较为接近.

Numerical calculation method was adopted based on fluid computational dynamics to obtain the velocity field and achieve the corresponding friction velocities of their surfaces, because the wind erosion emission estimation needed the friction velocities. The maximum, minimum and average surface friction velocity is 0. 168, 0. 063 and 0. 110 m/s, respectively at the 3.3 m/s windspeed by calculation way and its average friction velocity enhances to 0. 294 m/s when windspeed increases to 10. 0 m/s. By comparison the calculation results and wind tunnel experiment ones in literature, it shows the numerical values are pretty close to the experiment outcomes. So the numerical method is right and credible. According to the EPA emission mode, as the mine piles with 11 ten thousand square meters an example, the probability of erosion emmision on divided small surfaces is calculated 14.5% and the whole wind erosion emission quantity is amounted to 671.4 t/a, which is near to actual erosion emmision 700 t/a when yearly average wind velocity is 3.3 m/s and piles are disturbed every 3 days.