Viscosity Ratio Effect on Drop Deformation in the Boundary Layer

In the present study, the motion of a droplet in the boundary layer is investigated numerically. Volume of Fluid method is employed to solve the governing equations. It is found that the presence of the droplet leads to an increase in the pressure inside the boundary layer and on the wall. The results show that the droplets create a vortex on the bottom surface. The friction coefficient increases due to the presence of the droplets and is reduced before and after the droplet due to the formation of a vortex. It is concluded that increasing the viscosity and reducing the density at the same time will not affect the velocity and friction coefficient. It is shown that increasing the radius of the droplet increases the stress and thus decreases the boundary layer velocity. As the Reynolds number increases, the amount of surface friction coefficient decreases. By adding nanoparticles into the pure water, surface friction coefficient increases, especially in the region where the droplet is present.