Turning Back Time With Reversible Laminar Flow





Introduction: Turning Back Time With Reversible Laminar Flow

This is a nifty physics demo that was made popular (as far as I can tell) by John DeMoss and Kevin Cahill at the University of New Mexico. The apparatus used in the link is available for purchase for $550 (see linked video description). This is my attempt to make one for under $100. Going off of the original youtube video this is what I came up with and I am pretty pleased with the results:


Step 1: Materials

This is what I used

- Round wood for the base (It doesn't actually have to be round but I would recommend getting a piece of wood that is 1'' thick so you can cut pretty deep grooves with the Dremel)
- Clear Acrylic Pipes (I used one pipe with 6'' outer diameter and another with 4'' outer diameter)
- Piece of wood for the handle (I used the long darker piece of particle board that I found in a scrap pile but anything will do)
- Gorilla wood glue
- Silicone sealant (not pictured)
- Corn syrup
- Food Coloring
- Cups & Straw

- Dremel
- Drill with 4'' circular bit
- Hack Saw
- Clamps

If you have access to a laser cutter or a 3D printer I would recommend using those tools to create a much more precise base and handle for this apparatus. I am convinced that if I had a handle that I could have turned with out shaking the whole setup as much as I did then the final result would have came out better. That being said you can achieve pretty amazing results with the setup that I have here so if all you have is a drill or a Dremel don't be discouraged!

Step 2: Preparing the Base

So the first thing that you will need to do before installing the pipes will be preparing the base. The base essentially consists of two concentric circles that need to be cut wide enough for your pipes to fit into the base. the outer tube will be sealed into its groove and the inner tube will be left to freely rotate so it is okay to cut the inner tube with a little extra room so that the inner tube can rotate easily. 

To prepare the wood to be cut with a Dremel I traced the inside and outside of the pipe onto the wood with a pencil and then set the groove depth on the Dremel and proceeded to hallow out the outline. The nicer job that you do here the nicer the final product will look but as soon as the pipes fit you are free to stop. 

Step 3: Cutting the Pipes

So I choose to make my 6'' pipe 6'' tall and then left my 4'' pipe 9'' inches tall. The important thing is to cut your 4'' pipe to be taller that your 6'' pipe by 2-3 inches. 

Taping the pipe with painters tape really helps you keep the cut straight.

Step 4: Sealing the Outside Pipe

Since the outer pipe will be stationary it will need to be sealed to create a water tight (well actually corn syrup tight) seal. To achieve this I first used wood glue to fill up the groove and then went along the inside of the pipe with silicone sealant to make sure that no moisture can penetrate the seal. Make sure to let everything dry and cure for the appropriate time. 

Step 5: Preparing the Inner (spinning) Pipe and Its Handle

So you should have left the 4'' pipe 2-3 inches longer than the 6'' pipe. To prepare the handle I used the Dremel to cut another groove that would fit over the outside pipe. Then I used the 4'' circular drill bit to cut a hole in the middle of the groove to create a flush fit with the 4'' pipe.

This will have to slide on and off of the apparatus because you will have to add the food coloring to the corn syrup without the handle on and then replace the handle and turn everything around... There is definitely room for further innovation here!

Step 6: Preparing the Corn Syrup

So to make the effect really cool you will need three different colors of corn syrup. I mixed in food coloring to three different cups of corn syrup and stirred them up. Then you need to fill the apparatus up with corn syrup. I found that filling up the outer pipe with corn syrup and then sliding in the inner pipe yielded the best results. So to be clear your inner pipe is also filled with corn syrup.

Be careful with corn syrup!!! It is very sticky can can easily cause a mess if you mishandle it. 

Step 7: Performing the Demo

To actually perform the demo you will need to get three colored drops into the mix of clear corn syrup. I just but a straw in my mouth and sucked up some of the colored corn syrup and then blew the colored corn syrup into the clear mix. If you are using this method be careful not to get any air bubbles into the mix or it will mix up the colors. 

Once you have each of the three colored drops in place slowly turn the handle clock-wise 5 times. Then pause and turn the handle counter-clockwise 5 times. Hopefully if you didn't shake it too much you should see something pretty cool!! This seeming reversal is related to the viscosity of the corn syrup which creates a pretty low reynolds number allowing us to "reverse" the process. To learn more about this phenomena I would start with this wikipedia link.



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great instructable, as a practical use I often use lamella clarifiers to separate solids and clean-up waste water

This is brilliant! it's like; "Screw you, entropy".

I've seen this demo several times, since I was very young, using a variety of fluids though I'm pretty sure they were mostly oil based when I was at school.

FYI, "Corn Syrup" seems to be a peculiarly American product, and I've never seen it available in the UK, but it's obtainable as"Glucose Syrup", which can be bought from a Pharmacist if you can't find it anywhere else.

That doesn't surprise me. The U.S. has a ridiculously out-of-control corn-growers lobby and subsidy system and, as a result, farmers grow a lot of corn that's been engineered to be either animal feed stock or a substitute for sugar cane.

Hence why High-Fructose Corn Syrup (HFCS for short) is ridiculously common in processed goods in America.

If you can find it, there's a good documentary on the topic named King Corn.

There's also "Food Inc.", a very interesting documentary about the American food industry. Have you seen that? Horrifying...

I'm not sure. I've seen several but I'm having trouble matching names to memories.

I do know that, if I haven't seen it, it's on my TODO list.

This is amazing and I will be building one for our home school coop science class.

One question though: why do you need syrup in the inner cylinder? Aren't you putting the colored syrup between the inner and outer walls?



Syrup isn't necessary on the inner cylinder... I just noticed that when I didn't fill the inside with syrup it was harder to see the mixing on the other side of the inner cylinder. I also didn't make an attempt to seal the bottom of the inner cylinder so some syrup would always leak in. After a couple of runs I just let the inner cylinder fill up completely and it yielded the nicest result so I stuck with it. Good luck building this for your home school science class and feel free to contact me if you have any more questions.

Fluid dynamics is witchcraft.