2019/03/09 by Maziyar Jalaal, Carola Seyfert, Jacco H. Snoeijer +1
Engineering · Physics and Astronomy · #Amplitude #Capillary action #Capillary wave #Fluid Dynamics and Heat Transfer #Fluid Dynamics and Thin Films #Heat Transfer and Boiling Studies #Lubrication #Lubrication theory #Ripple #Thin film #Viscous liquid #physics.flu-dyn
paper · pdf · doi:10.1017/jfm.2019.734
9 pages, 4 figures
arxiv created 2019/03/09 · openalex created_date 2019/03/22 · openalex publication_date 2019/10/09 · arxiv updated 2020/10/07 · openalex updated_date 2026/08/05
Capillary ripples in thin viscous films are important features of coating and lubrication flows. Here, we present experiments based on digital holographic microscopy, measuring with nanoscale resolution the morphology of capillary ripples ahead of a viscous drop spreading on a prewetted surface. Our experiments reveal that upon increasing the spreading velocity, the amplitude of the ripples first increases and subsequently decreases. Above a critical spreading velocity, the ripples even disappear completely and this transition is accompanied by a divergence of the ripple wavelength. These observations are explained quantitatively using linear wave analysis, beyond the usual lubrication approximation, illustrating that new phenomena arise when the capillary number becomes of the order of unity.