The Viscoelastic Rayleigh-Bénard Convection Investigated by Different Optical Methods

The instabilities in horizontal layers of viscoelastic fluids heated from below and cooled from above have been investigated by the present authors in earlier papers [1] applying holographic interferometry. It was shown that the critical Rayleigh number Rac characterizing the onset of laminar steady two-dimensional Rayleigh-Benard convection can be increased in viscoelastic polymer solutions as compared to Newtonian fluids. Subject of this paper are the transitions to three dimensional or time dependent stability regions.