基于湍流结构的风沙颗粒起动动态演化的概念模式

A Concept Model of Dynamic Evolution of Aeolian Sand Particles Entrainment in Terms of Turbulence Structure

从驱动沙粒群起动的湍流结构入手,提出了基于气固两相流自调节机制的风沙颗粒起动的概念模式。受风沙边界层湍流相干结构的产生、消亡、湍流的随机脉动和运动沙粒群碰撞过程的动量损失等因素的控制和影响,风沙两相流始终处于不平衡—平衡—不平衡的动态演化之中,在此过程中,存在着普通的空气动力学起动、典型的冲击起动、湍流猝发起动等多种起动方式的循环交替的动态演化。上述多种的沙粒起动方式能够根据风沙边界层边壁区的湍流运动应力和沙粒群碰撞过程的动量损失来界定。该概念模式需要综合利用相位多普勒粒子动态分析测速技术、粒子图像测速技术和高速数字摄影技术等手段来进一步验证。该概念模式的提出,将为深入理解沙粒起动的力学机制提供新的思路。

A concept model of dynamic evolution of aeolian sand particles entrainment in terms of turbulence structure is proposed.Wind-sand two phase flows always evolve dynamically from an equilibrium state to a non-equilibrium and returning to a new equilibrium state when the two phase flows are controlled alternatively by occurrences of burst-sweep cycles,turbulence random fluctuations,momentum losses of saltation particles＇ collision.During the dynamic processes,averaged aerodynamic entrainment could alternate with typical collision entrainment,turbulence burst entrainment.These types of sand particles entrainment can be identified on basis of kinematic shear stress of wall and momentum losses of saltation particles＇ collision.The model need being validated by making use of technologies of Phase Doppler Particle Analyzer,Particle Imagine Velocimetry and High-speed Digital Photography.