流体剪切与絮团的粘性分维数

Abstract

本文在已建立的絮凝体系表观粘度与不同形态絮团粘性分维数关系的理论模型基础上，实验考查了絮凝平衡状态下单体颗粒、线状絮团、面状絮团及体状絮团的粘性分维数、特征粘度、絮团的粘性组成等随流体剪切速率的变化情况。研究表明，流体剪切作用的强化增大了线状、面状及体状絮团的粘性分维数,但所有絮团的特征粘度与流体剪切速率无关，线状、面状及体状絮团的特征粘度彼此之间依次具有一个数量级的差异。所有絮团的粘性组成都与剪切速率有关，也与固相浓度有关，且不同絮团的组成具有不同的变化态势。文中对主要的实验结果从絮团形成与碎裂的双重机制给予了定性解释。 On the basis of the model developed by authors to relate the apparent viscosity of flocculated sus-pensions with the viscous fractal dimensions of flocs being of various morphologies, the fractal dimensions, specific viscosities and compositions of the single particles, linear flocs, planar flocs and volumetric flocs are investigated experimentally at different fluid shearing conditions and stable flocculation progress. The results show that the viscous fractal dimensions of linear, planar and volumetric flocs increase rapidly at first and gradually then with the reinforcement of shearing rate, but the specific viscosities of all kind of flocs including single particles are independent of the shearing rate, and the specific viscosities of linear, planar and volumetric flocs differ from each other by a order of magnitude in turn. The viscous compositions of all flocs and single particles are the function of both shearing rate and solid concentration, and different composition behaviors are revealed. The main experimental results are analyzed and explained qualitatively by considering the double mechanism of floc formation and breakage resulted from the fluid shearing.