Details

Autor(en) / Beteiligte

• Thorens, Louison
• Måløy, Knut J
• Flekkøy, Eirik G
• Sandnes, Bjørnar
• Bourgoin, Mickaël
• Santucci, Stéphane

Titel

Capillary washboarding during slow drainage of a frictional fluid

Ist Teil von

• Soft matter, 2023-12, Vol.19 (48), p.9369-9378

Ort / Verlag

England: Royal Society of Chemistry

Erscheinungsjahr

2023

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Numerous natural and industrial processes involve the mixed displacement of liquids, gases and granular materials through confining structures. However, understanding such three-phase flows remains a formidable challenge, despite their tremendous economic and environmental impact. To unveil the complex interplay of capillary and granular stresses in such flows, we consider here a model configuration where a frictional fluid (an immersed sedimented granular layer) is slowly drained out of a horizontal capillary. Analyzing how liquid/air menisci displace particles from such granular beds, we reveal various drainage patterns, notably the periodic formation of dunes, analogous to road washboard instability. Considering the competitive role of friction and capillarity, a 2D theoretical approach supported by numerical simulations of a meniscus bulldozing a front of particles provides quantitative criteria for the emergence of those dunes. A key element is the strong increase of the frictional forces, as the bulldozed particles accumulate and bend the meniscus horizontally. Interestingly, this frictional enhancement with the attack angle is also crucial in small-legged animals' locomotion over granular media. Combining experiments, theory and numerical simulations, we elucidate the emergence of various drainage patterns arising when an immersed granular bed in a capillary tube is displaced by a liquid/air meniscus as the liquid is slowly drained out.