Catching drops with fibers
The passive filtration of liquid droplets from aerosol streams or emulsions is done by placing a porous (generally fibrous) structure in the path of the mist; in particular, woven nets are used to harvest fresh water from fog, and non-woven entangled fibers are used to filter oil drops from gas streams. In this talk, I will present recent results on the capture of aerosol droplets with an array of parallel fibers.
We identify the key role played by the drop distribution on the fibers on the overall collection efficiency. Due to a growth and coalescence process, this drop distribution evolves toward a regular pattern of uniformly distributed drops, and a balance between capillarity and gravity sets an average drop size.
Accounting for these effects in a simple inertial impaction model allows a quantitative prediction of the collection efficiency. As the droplets accumulate on the fibers, they might merge and bridge adjacent fibers. If the fibers are flexible, they may deform under the capillary forces generated by these liquide bridges. We report and characterize a regime of elasto-capillary adhesion where the fibers are collapsed and form long liquid columns, efficiently capturing the incoming droplets. In addition, we extend our model to take into account the interactions between fibers.