 |
Experimental results of the linear stability of shear-thinning (pseudo-plastic) liquid films flowing under gravity are provided for the first time. We focus on low-concentrated shear-thinning aqueous solutions obeying the Carreau-law. The experimental study essentially consists in measuring wavelengths in marginal conditions, which yields the linear stability threshold for a given slope. In the case of weakly shear-thinning fluids, the experimental results of neutral curves at a given slope are in good agreement with the numerical results obtained by a resolution of the generalized Orr-Sommerfeld equation, and confirm the destabilizing effect of the shear-thinning behaviour in comparison with the Newtonian case (the critical Reynolds number is smaller, and the ratio between the critical wave celerity and an estimation of the flow velocity at the free surface is larger).
