Two balls interact in a bounded shear flow: passing over/under

[Animation]
Two balls are close to each other initially. They pass under/over each other in a bounded shear flow of a Newtonian fluid under creeping conditions.
  • The dimension of computational domain = (-1.5, 1.5)x(-1,1)x(-0.5,0.5).
  • The radii of the balls are 0.1.
  • The density of the balls = 1.
  • The density of fluid = 1.
  • The viscosity = 1.
  • The shear rate = 1.
  • Top wall moves and the bottom wall is at rest .
  • The initial mass centers are at (-0.14112758,0,0.012347063) and (0.14112758,0,-0.012347063), respectively. The initial gap size is 4h.
  • The mesh size for the velocity field h= 1/48
  • The mesh size for the pressure = 1/24
  • The time step=0.001.