6 research outputs found
The rise of the imams of Sanaa /
"A revision of a thesis presented to the University of Edinburgh in 1918."--Pref.Based chiefly on an anonymous work ascribed to Sayyid Aḥmad ibn Muḥammad ibn Ṣalāḥ al-Sharafī.Mode of access: Internet
Measurements of pore-scale water flow through snow using fluorescent particle velocimetry
Fluorescent Particle Tracking Velocimetry (FPTV) measurements of the pore-scale
water flow through the pore space of a wet-snow sample are presented to demonstrate the
applicability of this measurement technique for snow. For the experiments, ice-cooled water
seeded with micron sized fluorescent tracer particles is either sprinkled on top of a snow
sample to investigate saturated and unsaturated gravity-driven flow or supplied from a
reservoir below the snow sample to generate upward flow driven by capillary forces. The
snow sample is illuminated with a laser light sheet and the fluorescent light of the particles
transported with the water in the pore space is recorded with a high-speed camera equipped
with an optical filter. Tracking algorithms are applied to the images to obtain flow paths and
flow velocities. A flow loop found in a pore space for the case of saturated gravity flow
together with the tortuosity of the particle trajectories indicate the three-dimensionality of
the water flow in wet snow. The average vertical flow velocities in the pore spaces were
11.2 mm s1 for the downward saturated gravity flow and 9.6 mm s1 for the upward flow
that is driven by capillary forces for the limited cases presented as examples of the
measurement technique. In the case of unsaturated gravity-driven flow, the average and the
maximum flow velocities were found to be 30 times smaller than for the saturated gravity
flow. Velocity histograms show that the fraction of the total water flowing against the main
flow direction was about 3–5%, and that the horizontal velocities average to zero for both
the saturated gravity-driven and the capillary flow