Experimental characterization of the Taylor-Couette flow submitted to a radial temperature gradient

We have developed a non-intrusive velocity and temperature fields measurement technique using thermochromic liquid crystals which allows to fully characterize the flow produced in a narrow gap and large aspect ratio Couette-Taylor system submitted to a radial temperature gradient. The aspect ratio and radius ratio of the system are respectively equal to 112 and 0.8. The control parameters are the Grashof number \textit{Gr}, related to the radial temperature gradient, and the Taylor number \textit{Ta}, related to the rotation of the inner cylinder. Here, \textit{Gr} is fixed and \textit{Ta} is gradually increased. For small values of \textit{Ta}, the base flow is composed of the circular Couette flow and a vertical flow induced by the radial temperature gradient. Above a critical value of \textit{Ta}, the destabilization of the base flow gives rise to a spiral pattern. While for small \textit{Gr} values it corresponds to traveling inclined vortices, for large \textit{Gr} values it corresponds to a modulated wave-like pattern filling the whole length of the system and rotating at the mean angular velocity of the flow. When \textit{Ta} is further increased, this wave-like pattern is progressively replaced by a counter-rotating vortices pattern. Numerical simulations of the corresponding Boussinesq-Oberbeck equations provide results in good agreement with experiments.