Why I'm in Belgium

I'm learning about fluvial hydraulics. I'm basically helping a PhD student, Rui, with his research on dam breaks. Ryan, from South Carolina, in the same program as me is also in the group. What he's already done is assess the velocity profile of the water in his model when a gate separating two different depths drops. What we are doing now is adding a sediment layer to see how that affects the flow of water and to see how the sediment is transported. We work in a basement lab called the Cave. Each experience (that's what they call experiments) takes 4ish hours to set up and 10 seconds to run.

This next bit may be a little boring, but checkout the pics & videos.

The typical lab day goes as follows:

1. attempt to plug the leaks in the pneumatic gate with silicone strips from a caulk gun and play-doh (they were calling it plasticite and i thought it was a super-technical polybonding something..... until they gave it to me to use and i realized that it was edible and came with cookie cutters). we have yet to do this successfully, but the volume of the dipping is relatively small compared to the volume of water in the tank.

2. Create a Uniform and Compacted Sediment Layer.

We put a lot of sand, our sediment of choice, (for my soils friends, i'd give it a visual classification of a uniformly graded largish sand, i think i'm trying to forget about that class so i don't know if thats actually a possibility). have this board that hangs 10 cm above the bottom of the tank so we drag it across the top of the sand, so it's all the same depth. Then we (okay not really “we” more like “the guys”) drop a 40ish pound hammer three times on a square piece of wood as wide as the tank, this is repeated over the entire surface of the sand. {it ends up being about 100 lifts & drops per experiment run}. I move the wood square between drops. Then, we use the leveling board again, add more sand if needed, level that out. if lots of sand was added, we have to do the compaction all over.

3. Fill the tank. it's like watching paint dry. A diffuser, like one you would use in a garden, is used so the sand is only minimally deformed. The downstream half of the tank, is filled just to saturate/cover the sand. The upstream section is filled to 32.5 cm above the top of the sediment.

4. Play with Cameras, angles and lighting. Attach probes.

The space we have kind of stinks (literally, but here i”m talking figuratively), so everyday we have to make sure the camera lens is is parallel to the tank (so our distance measurements aren't distorted. The position and reflection of the lighting also has to be tweaked and the aperture adjusted.

Right now, We have 4 depth probes (1 before the gate and 3 after) and will move two of them further down the tank to get more readings. They are clamped to the top of the tank and transmit a signal, which has to be converted (or something...something about ac/dc, and volts to digital...i don't know) to the computer.

5. Lunch. Still struggling with getting what I want when I order. But i did have a traditional Belgain dish,Vol au Vent, that had been vegetarianized by the school cafeteria. A biscuit covered in some a thick white buttery sauce with fake chicken and a side of mashed potatoes. Um yummm, but very white. I can't really cook here, so i'm hurting for some good green veggies, but “salad” they put in sandwiches should suffice (for awhile at least).
   

6. Lights, Camera, Action! After distributing some plastic balls of varying densities in the Tank. Turn on the lights above the tank. Start the Camera; it takes 50 images a second for 15 second. Drop the gate. WHOOOSH! Keep seeding particles in the upstream section. When we analyze the data, we will use software that will track the individual particles so we can do velocity calculations.

   
   
   
   

7. Separation. The downstream end of the tank is open, so all of the water and some of the sand spills out. It lands on some mesh over a plastic tank to separate the sand and plastic from the water. We then get to separate plastic from the sand, so that the sand can be dried and weighed. this is done by placing the soilds in a bucket and spraying water into it. the agitation causes the plastic to rise; then we fish it our with a net or skim the top off with mesh.

8. Clean up.

Put away cameras & lights. Pull the sand away from the gate. remove all the stuff we stuffed down the sides of the gate to try to stop the leak.....gross (soggy play-doh mixed with WD40).