Last week the Tectonics class I’m TAing had an extra “throwaway” lecture. We decided to let the students build their own experiments to gain some intuition about Low Reynolds number flows, and what the Reynolds number means.
First we showed them a video produced by the National Committee for Fluid Mechanics Films which was an awesome NSF funded project to develop and film these complex and/or expensive experiments (which can be found on YouTube).
One of my favorite aspects of flow is the phenomenon of low Reynolds number flows. Low Reynolds number flows are flows where inertia plays only a small roll.
The Reynolds number is a dimensionless number that can be characterized as:
Re = (Density * Length * Velocity) / Viscosity
Re = Inertia / Viscosity.
Generally if the Reynolds number is below 2000 the flow is laminar, greater than 2000 the flow is turbulent.
To tie it to geology we helped the students work through an order of magnitude calculation of mantle viscosity. Try it for yourself: Density = 3300 kg/m^3, Length = 3 X 10^6 m, Velocity = 1 cm/yr, Viscosity = 10^21 Pas. What do you get? Is the mantle a turbulent or laminar flow?
After the video we gave the students a set of ingredients and beakers to play with: canola oil, molasses, water, food coloring, and glycerin. Fun fact about glycerin, the pharmacy only sells small bottles and employees will give you VERY strange looks when you ask for a liter of the stuff.
Here are the experiments the students came up with. You’ll here conversation about flows, mantle winds, and non-school stuff in the background.
First up we have molasses poured into glycerin:
and a small amount of molasses…
My favorite: a two layer system. Bottom layer is glycerin and top layer is oil.
And a turbulent flow for good measure…
Some things to take away from the student’s experiments: our containers were too small in height for the low Reynolds number plumes to fully develop before hitting the bottom. This would also require much more glycerin, and more weird looks.
And for fun here’s a video I found of a low Reynolds number (~1000) vortex ring collision. Science is so sexy.
I by no means am offering solutions to this. Instead I hope readers in the comments will help out by posting their past experiences with this situation and detailing how they’ve handled it. That said, I need your help to make this post work! First, my poster experience.
My poster session at #AGU11 went really well. I was at my poster for the full four hours and never got a chance to leave. I was talking the whole time and getting great, positive feedback on my research, and some ideas of where to take it further.
One gentleman did attack my work. The primary discrepancy came in the fact that he disagreed with outcrop features that I had interpreted as being cross-cutting. He had not personally been to the outcrop, but it was difficult to continue the discussion into the more interesting parts of my research because he would continually cut me off with “that’s not cross cutting.” Basic outcrop information that I had gotten across to everyone before (and after) was not getting to him. I must say it caught me off guard. This was my first time presenting a poster, and I was not sure how to handle this situation. I did my best to have a discussion with him, but it was very frustrating.
Overall my first poster presentation was a positive experience, and it reignited my drive to finish my #SciWrite manuscript.
So please, readers and fellow GeoBloggers, if you (and/or research) has been attacked at a poster session please post the story and your insights in the comments section!
The above talk titled: “Great Earthquake Ruptures in the Age of Seismo-Geodesy” is given by Professor Thorne Lay of UC Santa Cruz. As an undergraduate freshman at UCSC, I took Thorne Lay’s intro GE course Earth Catastrophes. It was your generic GenEd course geared to students of all majors. My major was then undeclared.
Thorne Lay’s lecturing style greatly impressed me. I never missed a single lecture; they were always, engaging, insightful, and fun. By the end of my Freshman year I had declared as an Earth and Planetary Science major. Thorne Lay’s course had been pivotal in interesting me in geology.
He is one of the better lecturers I can think of and even if you do not study earthquakes or geology, it is very informative and enjoyable.
The lecture begins at 5 min.
This is pretty cool. The Royal Society, the world’s first peer-reviewed journal has opened their archives to the public. Approximately 60,000 articles are dating back as far as the 1600s are available via a searchable archive.
Included in this archive is early geological work from Charles Darwin which features incredible sketches and maps.
The text is 47 pages long, but thankfully there is a short(ish) abstract also available
. The paper details Darwin’s study of lineaments, referred to as “roads” along Glen Roy and Lochaber. Previous authors concluded that the lineaments are lacustrine deposits from a time when lake levels were higher (Darwin 1837). Darwin goes on to put forth his theory for the lineaments: marine deposits made by uplift of the land, with a subsiding sea, subject to tides carving the valleys (Darwin 1837).
Observations on the Parallel Roads of Glen Roy, and of other Parts of Lochaber, with an Attempt to Prove That They Are of Marine Origin.Proc. R. Soc. Lond. 1837 4:127–129; doi:10.1098/rspl.1837.0057