Figure 3.

The two-dimensional axisymmetric mesh used for the CFD simulation. (Inset) Magnified view of the sphere area. The z axis is the axis of symmetry. Both the width (L_W) and height (L_H) of the mesh are 512 μm. The radius of the sphere (R) and the gap distance (L_s) were assigned according to the dimension of V. convallaria. Elements of the midsection move downward as a whole according to Eq. 7. Assigned boundary conditions are the axisymmetric condition for boundaries 1 and 4, the no-slip wall condition for boundary 5 representing the substrate, the moving wall condition for boundaries 2 and 3 representing the zooid, and the open condition for boundaries 6 and 7.