黏弹性流体系统附壁液滴剪切变形及运动研究

The deformation and movement of wall-attached droplets are closely related to the microscale displacement efficieney of residual oil. Since both the displacing liquid in polymer flooding and the heavy oil can exhibit viscoelasticity, it is necessary to clarify the influenae of the viseosity-related fluid properties on the behavior of wall-attached droplets in viscoelastic fluid Systems. The two-phase viscoelastic lattice Boltzmann method, combined with the geometric wetting boundary condition, is used to investigate the steady-state deformation and motion of a droplet under shear flow, where either the matrix phase (N/V System) or the droplet phase (V/N System) is the Oldroyd-B viscoelastic fluid while the other phase is the Newtonian fluid. The effects of the two-phase visoosity ratio m and the solvent viscosity ratio of the visco-elastic fluid are studied. Results show that the stretching of polymer molecules in the N/V System is the most pronounced outside the droplet tip and near the advancing contact lines, which aets to promote droplet spreading. The wetting area of the Newtonian droplet in the Oldroyd-B matrix is increased by either decrea-sing (increasing elasticity) or increasing m. The droplet surface area in the N/V System also expands with inereased m, but it reduces with the decrease of . In the N/V System, the sliding velocity of the droplet is enhanced with decreased for m < 1. 5, whereas for m 3:1. 5 the trend is reversed owing to the reduced overall driving foree caused by the much lower droplet height at smallery . In the V/N System,the polymer molecules inside the droplet are stretched more significantly near the reeeding contact lines, which inhibits the droplet's spreading. When m ^ 1, the wetting area is hardly affected by m or, but the wetting area increases with increased m or for m > 1. Under the effects of m and, the variations of the droplet surface area in the V/N System are consistent in trend with those in the N/V System. In both N/V and V/ N Systems, the droplet slides more slowly at a higher m. Unlike the droplet in the N/V System, the droplet in the V/N System with a smaller always moves slightly faster under a given m.