Primary instability of a shear-thinning film flow down an incline: Experimental study
Journal of Fluid Mechanics, cilt.821, 2017 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 821
- Basım Tarihi: 2017
- Doi Numarası: 10.1017/jfm.2017.276
- Dergi Adı: Journal of Fluid Mechanics
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Anahtar Kelimeler: Instability, Non-Newtonian flows, Thin films
- İstanbul Gelişim Üniversitesi Adresli: Hayır
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, fc) and (Re, k) planes (where fc 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.