箱体式活动沙障风沙流场特征

Characteristic of wind-sand flow field of box-type movable sand barrier

研究在野外调查的基础上,采用计算流体力学三维数值建模方法并结合室内风洞试验,分析了箱体式活动沙障在孔隙率与风速变化作用下的控沙特点及其周围风沙流场的演化过程。分析结果表明:在沙障的控制下,顺着风向在沙障前后依次出现减速区、减速上扬区、加速区与障后涡流区,在沙障腔体内形成明显的腔内减速区与涡流区,过境风沙流在沙障的减速区、障后涡流区与腔体内发生沉落,可见箱体式活动沙障发挥了控沙作用;随着风速增大,障前减速上扬区高度增大,但沙障迎风侧孔隙率的变化对减速上扬区高度没有影响;当沙障迎风侧横板孔隙率小于5%时,对来流的消减效果显著,积沙在沙障前卸载,不能充分发挥沙障背风侧涡流区的控沙作用;当孔隙率大于25%时,沙障能够充分发挥控沙作用,在沙障的迎风侧、背风侧与腔体内都有积沙卸载;当孔隙率继续增大至30%时,沙障控沙效果没有明显提高;选定孔隙率为30%条件下,随着风速的增大,沙障后积沙增加,沙障腔体内积沙减少,而沙障迎风侧积沙出现先增加后减少的变化趋势。

On the basis of field investigation,the sand-controlled characteristics of box-type movable sand barrier and the evolution process of wind-sand flow field around the barrier were analyzed by using computational fluid dynamics three-dimensional numerical modeling method and indoor wind tunnel test under the effect of changeable porosity and wind velocity.Analysis result indicates that under the control of sand barrier,there are deceleration zone,deceleration uptrend zone,acceleration zone,and vortex zone successively before and after sand barrier along the direction of wind.Deceleration zone and vortex zone form obviously in the cavities of sand barrier,the transient wind-sand flow sinks down in deceleration zone,vortex zone behind and the cavities of sand barrier,so the box-type movable sand barrier plays an important role in sandcontrol.As the increase of wind velocity,the height of deceleration uptrend zone increases,but the porosity change of windward side of sand barrier does not cause any effect to the height of deceleration uptrend zone.When the porosity of windward side of sand barrier is less than 5%,the flow weakens observably,and the sand deposites in the front of sand barrier,which can not make full use of the sand-control function of vortex zone behind sand barrier.When the porosity is more than 25%,the sand barrier can play full sand-controlled role,sand deposites in thewindward side,leeward side and cavities of sand barrier.When the porosity continues to increase to 30%,the sand-controlled effect does not improve obviously.Under the condition that the porosity is 30%,when the wind velocity continues to increase,the sand accumulation increases behind the sand barrier and decreases in the cavities of sand barrier,however,the tendency of decrease after the first increase occurs in the windward side of sand barrier.