دینامیک ذرات استوانه ای در جریان انقباض سیال دوم مرتبه

The finite volume method is used to numerically simulate the dynamics of cylindrical particles in the contraction flow of a second-order fluid. The effects of Stokes number, Deborah number, particle aspect ratio and contraction ratio on the spatial and orientation distributions of cylindrical particles are analyzed. Some numerical results are compared with the available experimental results in the contraction flow of Newtonian fluids. The results show that the spatial and orientation distributions of the particles are dependent on the competition among the inertia, viscoelasticity and effect of confined wall. The result of competition is responsible for the force and torque inducing a cross-streamline migration and rotation of particles. Along the flow direction, the particle spatial distribution in the cross section changes non-monotonically. The particle orientation distribution changes monotonically and particles gradually align themselves with the flow direction, and this phenomenon is more obvious than the case of the Newtonian fluid under the same conditions. High shear rate makes the particles align with their major axis near to the flow direction. With the increase of the Stokes number, the particle spatial distribution becomes more uniform, and orientation distribution function of particles becomes flatter and wider. With the increase of Deborah number and the contraction ratio, the particle spatial distribution becomes more non-uniform, in the meantime, more particles tend to align themselves with the flow direction. With the increases of the particle aspect ratio, the particle spatial distribution in the cross section becomes more uniform, and more particles align with their major axis near to the flow direction. In the parameter region studied here, the particle aspect ratio has a weaker effect on the spatial and orientation distributions of particles than Stokes number, Deborah number and contraction ratio.