Effect of bending stiffness on the deformation of liquid capsules enclosed by thin shells in shear flow.

Shear-induced deformation of liquid capsule enclosed by thin shell causes the development of in-plane tensions and bending moments due to the shell thickness or to a preferred three-dimensional unstressed configuration. This paper considers the effect of bending stiffness due to a preferred three-dimensional structure on the deformation and motion of the liquid capsule. To perform the numerical simulations, an improved formulation for computing the forces generated on the capsule surface during deformation is proposed. This formulation takes full account of large deformation kinematics and the development of in-plane tensions and bending moments. The deformation and orientation dynamics of capsules with different reference shapes are studied under various shear rates, viscosity ratios, and bending modulus. The numerical results show that the bending stiffness not only restricts the deformation but also affects the motion mode of the capsules. In addition, raising bending stiffness amplifies the shape deformation oscillations in tank-treading mode but reduces the oscillations in tumbling mode.