Open capillary siphons

Abstract

Flow in the inverted U-shaped tube of a conventional siphon can be established and maintained only if the tube is filled and closed, so that air does not enter. We report on siphons that operate entirely open to the atmosphere by exploiting surface tension effects. Such capillary siphoning is demonstrated by paper tissue that bridges two containers and conveys water from the upper to the lower. We introduce a more controlled system consisting of grooves in a wetting solid, formed here by pressing together hook-shaped metallic rods. The dependence of flux on siphon geometry is systematically measured, revealing behaviour different from the conventional siphon. The flux saturates when the height difference between the two container's free surfaces is large; it also has a strong dependence on the climbing height from the source container's free surface to the apex. A one-dimensional theoretical model is developed, taking into account the capillary pressure due to surface tension, pressure loss due to viscous friction, and driving by gravity. Numerical solutions are in good agreement with experiments, and the model suggests hydraulic interpretations for the observed flux dependence on geometrical parameters. The operating principle and characteristics of capillary siphoning revealed here can inform biological phenomena and engineering applications related to directional fluid transport.

Wenn das Wasser bergauf fließt

“…Aus Dochtschnüren gefertigte Siphons können daher völlig offen zur Atmosphäre arbeiten. In Fachpublikationen ordnet man sie den „Open Capillary Siphons“ zu [1]. Darin kommt zum Ausdruck, dass die hier umschriebenen Kapillarkräfte für ihre Funktion maßgeblich sind.…”

“…Eine physikalische Beschreibung des Docht‐Siphons wird durch seinen komplexen Aufbau erschwert. Um sein Betriebsverhalten dennoch zu charakterisieren, fertigten die Autoren von [1] ein Modell davon an, das die vielen verzweigten Strömungskanäle durch einen einzelnen Flüssigkeitsfaden ersetzt. Zur Führung dient eine Rinne, deren gut benetzbare Seitenwände im spitzen Winkel aufeinandertreffen (Abbildung 5).…”

“…Von daher ist die Durchflussrate bei einem klassischen Rohr‐Siphon proportional zu . Bei einem Rinnen‐Siphon steigt sie dagegen zunächst proportional zu h an, bis bei größeren Werten von h ein Übergang zu konstanten Werten stattfindet [1].…”

Study on high span motion characteristics and drag coefficient of airborne dust particles

“…In the traditional physical model, it is pointed out that the resistance of an object in the air is f=k 1 v+ k 1 v 2 . The air resistance can be considered as f=k 1 v 2 when the velocity is not large, and as f=k 1 v 2 when the velocity increases to a certain extent, where k1 and k2 are air drag coefficient; the Reynolds number Re is introduced into fluid mechanics to characterize fluid flow, which can be used to study the drag coefficient of objects with large size and fast movement velocity [6] ; however, for dust particles with a size of 10 -7 ~10 -5 m, the macroscopic disturbance to the airflow can be almost ignored when they move in the air. Therefore, the dynamic model of particles can be established based on the molecular kinetic theory, and the drag coefficient of particles moving in the air can be derived.…”

Dynamics of the capillary rise in tilted Taylor-Hauksbee cells

“…Natural functional surfaces like peristome surface give inspiration for designing and fabricating functional surfaces and materials with wide applications including water transport for agricultural drip irrigation over long distances, controllable self-lubrication and smart and controllable microfluidic devices [5], to name a few. Implementations of V-grooves in devices at a larger scale has been done to improve the heat transfer capacity of heat pipes [6] as well as open capillary siphons [7]. Coincidently, it has recently been proposed that capillary corner flow is also an important transport mechanism during the spreading of viruses and bacteria [8,9].…”