Liquid film over a stretchable uniformly heated wall with evaporation–condensation effects
International Communications in Heat and Mass Transfer, cilt.178, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 178
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.icheatmasstransfer.2026.112006
- Dergi Adı: International Communications in Heat and Mass Transfer
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Anahtar Kelimeler: Accelerating–decelerating regimes, Dual solutions, Evaporation–condensation, Heat transfer, Stretching surface, Thin film flow
- Hacettepe Üniversitesi Adresli: Evet
Özet
This study investigates the unsteady flow and heat transfer of a viscous liquid film over a stretching surface, incorporating the combined effects of surface unsteadiness and interfacial phase change. Building upon the hydrodynamic framework of Wang (1990) and the evaporation–condensation formulations of Ajaev (2005) on a uniformly heated surface, we employ a similarity transformation to reduce the governing partial differential equations to a system of nonlinear ordinary differential equations. A key feature of this model is the coupling of the interfacial mass flux with the kinematic boundary condition, assuming a uniform but time - dependent temperature field dissimilar to the thermal treatment in Andersson et al. (2000). Numerical results obtained via a normalized fixed domain transformation reveal a designated shift in film dynamics across different unsteadiness regimes. Analytical and asymptotic derivations are also provided to justify the numerical findings, whose limiting solutions are further validated through available data in the literature. In the accelerated stretching regime, evaporation paradoxically thickens the film and reduces the wall heat flux due to the dominance of stretching induced mass demand. Conversely, in the highly decelerated regime, evaporation acts as a potent thinning mechanism, significantly enhancing the local Nusselt number and increasing skin friction by several orders of magnitude. Furthermore, the study reports the discovery of dual solutions specifically for the condensation case in stretching flows, indicating a bifurcation point where the film may exist in either a quasi-stable stretching state or an ultra- thin high-gradient mode. These results suggest that interfacial phase change serves as a critical control parameter for tuning the thermal and mechanical resistance of liquid films in industrial coating and extrusion processes. In particular, since condensation induces a bifurcation indicating a critical thickness below which the film behavior changes drastically, it may demand focussed attention from engineering view point.