Capillary Rise Profile

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By Tom Kodger


Experimental System

2μm beads dispersed in clean 18.2MΩ water at a 1:1000 dilution (2wt% stock concentration). Beads were washed to remove any trace surfactant present in the bead stock. Capillaries with a 400μm ID and 1mm OD.

Imaging System

Particles observed at 100X oil immersion magnification with a Phantom V7.3 camera, with a frame rate of 8000 and a 200μsec interval period. 400umID 100Xoil 5000fps 200us 2.gif

Experimental Question

How does the flow field go from a uniform capillary rise at the interface to a Poiseuille parabolic flow at a distance away from the interface?


Analysis

Use PIV (particle image velocimetry) to find flow field.

Flow field near the interface
Poiseuille far from the interface

Conclusion

The high flow field in the middle (Poiseuille) is driven toward the wall at the interface. This concludes that the flow velocity at the center of the channel is greater than the capillary rise velocity, otherwise this condition would violate conservation of momentum.