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| The convection of a pure fluid in rotating spherical shells is well studied, but not much is known for binary fluids. The aim of this work is to study the influence of an externally forced concentration gradient on the onset of convection of a mixture of two components. To solve this problem two numerical methods are applied. The first computes the eigenvalues by evolving the linearized equations a selected time interval, and the second is based on a double complex shift.
The results are compared with those obtained previously for a pure fluid of the same Prandtl number. For negative concentration gradients the critical thermal Rayleigh number, the precession frequency of the waves, and the azimuthal wave number, start to increase significantly when the compositional Rayleigh numbers are at least one order of magnitude larger than the thermal. On the contrary, for positive and sufficiently large concentration gradients, the thermal Rayleigh number decreases and suddenly changes sign indicating that the compositional gradients can trigger the convection even in presence of stabilizing temperature gradients. Then, the convection becomes almost stationary. |
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