Effect of Rotation on Surface Tension Driven Flow During Protein Crystallization

Effect of rotation on surface tension gradient driven flow, which is also known as Marangoni convective flow, during protein crystallization is modelled and studied computationally under microgravity conditions, where the surface tension gradient force is the main significant driving force. The axis of the externally imposed rotation, which is assumed to be either parallel or anti-parallel to the gravity vector, is assumed to be inclined at an angle γ with respect to the axis of the crystal. In addition to the angle γ, the main parameters are the solutal Marangoni number Mc, representing the surface tension gradient force and the Taylor number Ta representing the rotational effect. The numerical computations for various values of the parameters and low gravity levels indicated nontrivial competing effects, due to surface tension gradient, centrifugal and Coriolis forces, on the flow adjacent to the protein crystal interface and the associated solute flux. In particular, for given values of Mc, certain values of Ta were detected where the Sherwood number, representing the convective solute flux, and the convective flow effects are noticeably reduced. These results can provide conditions under which convective flow transport during the protein crystallization approaches the diffusion limited transport, which is desirable for the production of higher quality protein crystals.