SUPPRESSING CONVECTIVE INSTABILITIES IN PROPAGATING FRONTS BY TUBE ROTATION

Density gradients caused by thermal and solutal gradients often cause double-diffusive and/or Taylor instabilities in propagating fronts. Th ese instabilities manifest themselves as ''fingering'' that can affect the front shape and velocity and, in extreme cases, destroy the front . This is especially a problem with propagating fronts of polymerizati on when a monomer is used that does not produce a cross-linked polymer . We have found that it is possible to suppress the fingering by rotat ing the tube around the long axis of the tube. With the chlorate-sulfi te system and methacrylic acid polymerization system, we found that th e front velocities exhibited a fourth-order dependence on the rotation al frequency, and the front shapes were parabolic. The amplitudes of t he deviation of the fronts from a planar front exhibited a second-orde r dependence on the rotational frequency but not exactly as predicted from the hydrostatic analysis of a rotating fluid.