A study of start-up flow of thixotropic fluids including inertia effects on an inclined plane

作者：Liu, Wenwen^*; Zhu, Ke-Qin

来源：Physics of Fluids, 2011, 23(1): 013103.

DOI：10.1063/1.3536654

• PIPE

Despite the practical importance of thixotropic fluids, there is no reliable way at present to predict the onset of thixotropic flow. The start-up flow of thixotropic fluids including inertia effects falling down along an inclined plate is studied in this paper. The effects of the unsteady term in the NS equations on the start-up process are clarified and a criterion parameter A is presented to measure this unsteady effect. The parameter A is defined as the ratio of the Reynolds number and generalized Weissenberg number W, where W is the ratio of the characteristic time of microstructure changes and the characteristic time of flow. According to flow characteristics, we classify the motion into three cases. In case 1, avalanche happens and the initial viscosity is big. The start-up process is divided into two stages: creep and flow. Velocity profiles of both stages are discussed. In this case, if A is small enough, the inertia effects could be neglected. Otherwise, the inertial unsteady term will protract the start-up process, decrease the velocity of the free surface, and bring a thicker unyield region. In case 2, the avalanche happens and initial viscosity is small. Similar inertial unsteady effects are observed. Moreover, the unsteady term in the NS equations could delay the critical time at which the flow happens or even prevent the thixotropic material from flowing. In case 3, the avalanche could not happen. The inertial unsteady effect is only present in the start period and has no influence on the later motion.

• 出版日期2011-1
• 单位清华大学