气体剪切下液滴临界滑动无量纲准则

Dimensionless Critical Criterion for the Sliding of Droplet on Tilt Surface in Shear Flow

液滴从固体壁面上脱离的临界条件对农作物生长、滴状冷凝换热、燃料电池水管理等具有重要影响。液滴在气体吹拂下临界滑动是液滴重力与气体施加的拖拽力共同克服表面张力的结果。通过建立受力平衡方程,并无量纲化,本文得到适用于气体剪切下不同壁面倾斜角度及不同气-液-固物系下液滴滑动临界的通用准则。该准则可用于计算燃料电池中固定大小液滴滑动的临界风速,与Fan等实验数据对比,其误差在20%以内。另外,该准则用于计算滴状冷凝中固定风速下液滴临界滑动半径,可以完善蒸汽吹拂下的滴状冷凝模型。

Critical condition for the departure of droplet from solid wall is very important for crop growth, dropwise condensation and water management of fuel cell. The gravity together with drag force from shear flow overcome surface tension force to yield the sliding of droplet. Based on force balance equation, dimensionless critical criterion was proposed in this paper for the sliding of droplet on tilt surface in shear flow. For the problem of the critical wind speed to yielding droplet sledding, the error is less than 20% between experimental data and theoretical value by critical criterion. The dimensionless critical criterion is useful to predict the droplet departure diameter for dropwise condensation in the steam flow, which is the important parameter in the dropwise condensation heat transfer model.