On the linear stability of mixed and free convection between inclined parallel plates with fixed heat flux boundary conditions
For the fixed heat fluxes at the boundaries it is shown that if the temperature gradient parallel to the plates is adverse (temperature increasing downward), the flow is unstable for any value of the Rayleigh number. That is, the critical Rayleigh number is zero. This result holds independent of the base velocity and temperature distributions and inclination.
scientific article; zbMATH DE number 404969