2005/01/30 by N. Le Grand, P. Brunet, Philippe Brunet +8
Engineering · Physics and Astronomy · #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Fluid Dynamics and Heat Transfer #Fluid Dynamics and Thin Films #Lattice Boltzmann Simulation Studies #physics.flu-dyn
paper · pdf · doi:10.48550/arxiv.physics/0501153
Submitted to Journal of Fluid Mechanics
arxiv created 2005/01/30 · openalex publication_date 2005/01/30 · arxiv updated 2009/12/01 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/28
We have preformed experiments on a liquid curtain falling from a horizontal, wetted, tube and lateraly constrained by two vertical wires. The fluid motion nearly reduces to a free-fall, with a very low detachment velocity below the tube. Thus, the curtain contains a large subsonic area, i.e. a domain where the sinuous waves travel faster than the fluid. The upper boundary not being constrained in the transverse direction, we have observed the appearance of an up to now unreported instability when the flow rate is progressively reduced: the top of the curtain enters a pendulum-like motion, coupled to a propagative pattern of curtain undulations, structured as a chessboard. Measurements of the phase velocity and frequency of this pattern are reported. Data are in agreement with a simple dimensional argument suggesting that the wave velocity is proportional to the surface tension divided by the mass flux of liquid per unit length. This scaling is also that followed by the fluid velocity at the transonic point, i.e. the point where the fluid velocity equals that of sinuous waves. We finally discuss implications of these results on the global stability of falling curtains.