Primary instability of a shear-thinning film flow down an incline: experimental study


ALLOUCHE M. H. , BOTTON V., MILLET S., HENRY D., DAGOIS-BOHY S., Guzel B. , ...Daha Fazla

JOURNAL OF FLUID MECHANICS, cilt.821, 2017 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 821
  • Basım Tarihi: 2017
  • Doi Numarası: 10.1017/jfm.2017.276
  • Dergi Adı: JOURNAL OF FLUID MECHANICS

Özet

The main objective of this work is to study experimentally the primary instability of non-Newtonian film flows down an inclined plane. We focus on low-concentration shear-thinning aqueous solutions obeying the Carreau law. The experimental study essentially consists of measuring wavelengths in marginal conditions, which yields the primary stability threshold for a given slope. The experimental results for neutral curves presented in the (Re, f(c)) and (Re, k) planes (where f(c) is the driving frequency, k is the wavenumber and Re is the Reynolds number) are in good agreement with the numerical results obtained by a resolution of the generalized Orr-Sommerfeld equation. The long-wave asymptotic extension of our results is consistent with former theoretical predictions of the critical Reynolds number. This is the first experimental evidence of 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 the flow velocity at the free surface is larger.