Scale model - viscosity

[karimwassef]

I'm building a scale model of my future tank. It's 1/3 so the 12' tank becomes 3', etc...

The intent is to look at flow along the long path (12' down, 8' side, 12' back = 32' travel)...

I'm using the concept of similitude from fluid dynamics so my scale model has an equivalent dynamic viscosity to my water tank:

http://www.springer.com/cda/content/...748-p177097326

But that means that I need to find a liquid that has 3 x the dynamic viscosity of water. Milk is close, but I'd need 150 gallons of milk... $$$

So - I'm thinking of mixing 50:1 splashless bleach to raise the viscosity of the scale model water instead...

https://www.clorox.com/products/clor...SAAEgLk9vD_BwE

thoughts?

[Vinny Kreyling]

Keep any and all clothes far away.

[Wally.B]

Thanks for helping me on the Scrubber Forum, hope this gives you some ideas.

How about diluting some of this or similar product. (Bath Gel, Bath Slime), if it can thicken a BathTub of water, then close to your tank size and costs less than milk. Won't rot.
http://www.zimplistore.com/

Not clear since colored, but will smell better than Bleach.

Here is another Link to Water Gel. Skip the Color part and it might be clear enough.
https://www.stevespanglerscience.com...d-squishybaff/

The Polymer powder they mention may not do the trick since beady, and possibly way thicker than what you need.

But the slime formula might work if diluted right, to thicken water to your requirements.

Not sure if any of these will work for you.
Just some out of the box thinking for you to consider.
Good luck with your Model.

[karimwassef]

thanks! glad for any ideas that could make this scale model more representative of the real system.

I'm sure there's a thickening agent that clorox uses. If I could get just that, it could do the trick.

I don't have a way to measure viscosity, so I'd need to know the properties and get to it by design/mixing.

[Wally.B]

Originally Posted by karimwassef

I'm sure there's a thickening agent that clorox uses. If I could get just that, it could do the trick.

Good luck. Over my head.
http://www.freepatentsonline.com/4839077.html

[karimwassef]

nice searching!
It's over my head too - but this is the chemistry forum... someone might be able to tease it out.

The basic question is "how much of what chemical do I need to mix in to triple the dynamic viscosity of water at room temperature?"

[Dan_P]

Compounds like methyl cellulose increase viscosity and might fit well within your budget. Googling methyl cellulose might lead you to other cheap thickening agents. Food and pharmaceutical preparations often require thickening agents. Food examples include flour and corn starch.

[karimwassef]

Is there an off the shelf product of methyl cellulose?

Found it

https://www.amazon.com/gp/aw/d/B0025...ethylcellulose

Also citrucel is apparently based on the same

https://www.amazon.com/gp/aw/d/B002J...ethylcellulose

[karimwassef]

Is there an easy way to tell when a mixture is 3x the dynamic viscosity of water?

It's = absolute viscosity / density.

I can get density by using a weight scale and graduated container.

That leaves viscosity to be empirically determined.

https://www.google.com/amp/m.wikihow...cosity%3famp=1

I love google. So it's a little complicated, but doable.

Anything easier?

[karimwassef]

What about polyethylene glycol?

https://www.amazon.com/gp/aw/d/B01MT...thylene+glycol

Or plain old food starch?

https://en.m.wikipedia.org/wiki/Starch

[bertoni]

I must admit that I don't know enough chemistry to help much here. The polyethylene glycol will be safe to handle, but I don't know how much to add.

[karimwassef]

I'm getting all three - polyethylene glycol, food starch and methyl cellulose

I'll add the same % and measure dynamic viscosity.

[ReefsandGeeks]

I'd suggest trying to measure the viscosity of water itself several times with your wiki method prior to anything else. If you're not able to get repeatable results, than the method will do you no good. The reason I bring this up is the viscosity of water is very small, and the measuring utensils are cheap and have a fairly large variation, especially for measuring density. This will likely result in large variations in your results. This method would work better for thicker fluids like hydraulic oil, but with substances as thick as water or even a few times thicker, you may find it's not repeatable enough to trust.

With all of that said, I don't know how close you need your viscosity to be in order to meet your needs.

Also, do you plan on doing a mock up of your rockwork for the full size tank to check the flow on the scale model? The rockwork in the tank will play a very significant role in how the fluid flows.

You mentioned your intent is to look at flow along the long path, I'm guessing doing a "U" shaped path around the perimeter. What is the purpose of checking that flow? are you trying to size your pumps/power heads? determine if the flow will be too aggressive in one area vs another? determine power head placement prior to the main tank in case you want them built in? Depending on what your need is, you might be getting carried away with the model where your efforts could be on adjusting the real thing.

[karimwassef]

I'm running a large surge and counter surge system that hasn't been done before.

The tank is 1600 gals with a subterranean section that's 500gal. So the reef is 1100 gals and each surge is 180 gals. So - one event will release the surge on one end and then a counter surge of equal size on the other end ~ 28' away around the U.

A counter surge is when the DT acts as tube surge container and releases the volume into another.

This entire event will take 5 seconds since the openings are 4' x 1'. The intent is for this to repeat every 15 seconds. This is peak mode.

The intent in creating this flow is to create a current loop without substantial loss / either to the overflow, floor or in wasted wave energy. I wanted it to be as directionally uniform as possible. The target flow rate everywhere is to hit a peak of 4in/s and then alternate directions.

My fear is that the positive and negative water waves will take too long to equilibrate and a lot of water energy will be wasted or lost as surface waves instead of a circulating current..

I can adjusting timing/flow.., or make changes to he model to fix this.

[karimwassef]

There's also a second surge under the reef that creates a flow up from the far reef edge.
With 4 channels of flow, there are 16 permutation of flow dynamics.

I will also have powerheads for backup to create loop flow against the back end.

If this was a straight 8 or 10 ft tank, I'd just build it. But this is effectively a 28' x 4' tank with a U channel. Water energy moves too slowly in that scale and I can't predict it's behavior without getting much more capable at fluid dynamics -or- running a finite element simulation -or- building a scale model and trying things out.

I tried the first two options with little success. Before spending a lot of $$, I'm going to experiment.

[karimwassef]

Here's my build thread (one of them).

http://www.reefcentral.com/forums/sh...589632&page=25

The design has changed a lot since page 1 but it's getting closer.

[karimwassef]

[karimwassef]

[BarIzoN]

Corn starch + Wolfram Alpha for the calculations...




Sent from my iPhone using Tapatalk

[karimwassef]

Did I mention free or cheap simulation software?

Can wolfram do 3D fluid dynamics?

[karimwassef]

I was worried that corn starch varied too much over temp. I don't expect massive swings but still.

I guess part of my question in this thread was whether a small additive can effectively change the viscosity of water by 3x?

[karimwassef]

I could not get an accurate measure of water viscosity using the method above. Looks like this range of viscosities needs to be measured using capillary action.

I found a viscometer, but it's $141... for a single use, it's a little pricey for me.

https://www.amazon.com/Fungilab-CV00.../dp/B00K5RJ9QO



looks like I'll have to call some local universities and see if I can use their equipment

[karimwassef]

I'm going to experiment with a DIY capillary measure of viscosity ... will update once I get some pics and data.

If you want to see the full scale plan, I added a video to my main thread http://www.reefcentral.com/forums/sh...589632&page=25

[bice0004]

Glycerol is used to change viscosity of aqueous solutions. we use it in the lab when a series of different viscosities is needed for experiments. It is widely used for this purpose.

I did a quick google search and found this paper.

http://edge.rit.edu/edge/P13051/publ...0Solutions.pdf

[karimwassef]

Great. Thanks. That's perfect.

It points me to about 35%-40% aqueous glycerol by weight.

Unfortunately, it shows me the scale of the problem. I need 60 gallons of water ~ 500lbs so I would need 130lb of glycerol!!

I think that's ~$1000 if I buy it retail. I need a wholesale source of glycerol.