NUMERICAL STUDY ON THE ROTATION OF AN ELLIPTICAL PARTICLE IN SHEAR FLOW

A thorough understanding of the behavior of particles freely suspended in a shear flow is fundamentally important for understanding and predicting flow behavior of particle suspensions. The motion of particles is very complex when the fluid inertia is taken into account. In the present study, the lattice Boltzmann method has been used to simulate the rotation of an elliptical particle in simple shear flow at intermediate Reynolds numbers. Firstly, the effect of the Reynolds number (0 < Re≤170) has been studied. Results show that the particle rotates periodically when Reis smaller than a critical value. The orientation of the particle at which the particle has its minimum angular velocity decreases as Reincreases, which has a piecewise linear relationship with Re. Moreover, the rotation period has a power-law relationship with Re. The larger Reis, the larger the rotation period is. However, when Reis greater than the critical value, the elliptical particle will reach a steady state. Results show that the final orientation of the elliptical particle has a power-law relationship with Refor the steady state. The larger Reis, the smaller the orientation is. Secondly, the effect of the ratio of major axis/minor axis α(1≤ α≤10) has also been studied. It shows that there is also a power-law relationship between the rotation period and α. The larger the value of αis, the smaller the rotation period is. Similarly, when αis greater than a critical value, the elliptical particle does not rotate. The final orientation of the elliptical particle has a power-law relationship with α. The larger the value of αis, the smaller the orientation is. Furthermore, it also shows that the overshoot is observed when the elliptical particle is rotating if Reis larger enough.