Large volume laminar flow machine

[Michael Hoaster]

Well, we're on page 17. I think it goes without saying you've dug in!

Don't be too hard on yourself, buddy. Your system is already a technological marvel. You could sit back and relax. Or focus on something less technical, like going to Mars or Saturn…

 

[Floyd R Turbo]

Floyd,

What are you doing here, slumming? Actually, I agree. I would think that the flow will be a bit anemic, especially when driven by propeller pumps.

Lol I just clicked a link from the Acrylics thread and wasn't paying attention and didn't realize there were many previous pages! This looks really interesting, but unfortunately I don't think I have enough time to read the whole thread and absorb all of this. Ugh

 

[karimwassef]

Here's the latest... I got the head pressure down to under 2ft

<a href="http://s1062.photobucket.com/user/karimwassef/media/0_zps11kel6mi.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/0_zps11kel6mi.jpg" border="0" alt=" photo 0_zps11kel6mi.jpg"/></a>

I think I'm close to optimum because the bottleneck is now the fine comb at the end and the 1/4" transition just before it. Almost all the pressure drop is there. The next biggest drops are in the 1.5" wide section and the 1" wide section after it, followed by the 2.5" inlet.

If I increase the box distance, I can reduce it further.

The next question is... how low does the pressure have to be to make this work?

 

[salty joe]

Here's the latest... I got the head pressure down to under 2ft

<a href="http://s1062.photobucket.com/user/karimwassef/media/0_zps11kel6mi.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/0_zps11kel6mi.jpg" border="0" alt=" photo 0_zps11kel6mi.jpg"/></a>

Wow, you really cut the resistance down to size!

I'm probably missing something, but this has me bugged.
The water flowing in that 5 1/2"x 1 1/2" channel wants to favor going left. Why not remove the restrictor on the right and adjust the restrictor on the left to achieve even flow?

 

[karimwassef]

Your idea is logical.

I don't really know how effective those little deflectors are. I think I need them but I don't have any good design rules. If I'm symmetric, I know I'm forcing "more equal" flow- once I go asymmetric to offset a biased force, I have no idea how much offset would tip too far.

 

[karimwassef]

Here's a funky bit of math... The resistance is a function of hydraulic diameter and that's a function of the geometry. The bigger the hydraulic diameter, the lower the resistance.

For a pipe, it's the same as real diameter. 2" PVC for example.

For a square duct, it's the length of a side. 2" acrylic tube for example.

But for a wide duct, it's 2ab/(a+b) where a and b are the dimensions.
What messes up my wide duct resistance is that a is 2" and b is 15", so the hydraulic diameter is only ~ 3.5" ... So 11.5" of the duct is basically wasted in reducing friction.

http://www.engineeringtoolbox.com/hydraulic-equivalent-diameter-d_458.html

So... What if I break out the vertical sheets into 7 sections with 2" high vertical sections separated by 1/8" sheets??

Here's the math... Hydraulic diameter = 2" for each section, but the flow is only 1/7th...

So, I think I can reduce the friction more by adding horizontal sheets. Going to run the full calcs, but I think this could work.

 

[karimwassef]

Hey Floyd- can I etch 1/8" acrylic sheet with muratic acid?

 

[karimwassef]

11 feet? Ouch. Though i have never really thought about how well a powerhead would handle head that seems like a lot.

There are prop pumps built that can handle more than that in head, but generally they seem to be the same size as the pipe.


Now that im on a deeper pass of this idea i actually wonder how well props multiply outputs... They have a fixed maximum velocity they can impart on the water, based on the pitch and rpm. If all the water in the channel is at that velocity any more simply won't help (basically be free wheeling). It is a big channel, and lots of restriction so you probably aren't hitting it, but its something to keep in mind.

Gorgon, I guess I see it as multiple parallel flows.. Each fan has an invisible duct cross-section in front of it that it's feeding. I could force that by putting sheets of eggcrate in front and behind them.

In fact, I'm starting to consider 1/4" thick, 1/2" opening eggcrate as a potential alternative to acrylic for the diffuser box... Still formative, but the concept is that by stacking and offsetting, it may be possible to get the same effect with less plastic in the way... May be easier too.

 

[karimwassef]

So, here's the impact of creating horizontal layers:

<a href="http://s1062.photobucket.com/user/karimwassef/media/0_zpswofagrdg.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/0_zpswofagrdg.jpg" border="0" alt=" photo 0_zpswofagrdg.jpg"/></a>

So, there's a point of diminishing returns and going overboard is actually counterproductive. I think 5 layers at 3" each is manageable.

This should also relieve the stress of having to build a 15" high vertical construction that doesn't flex or twist or bend. The 3" is a viable DIY build geometry, I think.

Now that we're at less than 0.3ft head, do we still feel that the propellers will struggle?

 

[theatrus]

Hey Floyd- can I etch 1/8" acrylic sheet with muratic acid?

No, acrylic is resistant to most acids: https://www.tapplastics.com/uploads/pdf/acrylite_chem_resist.pdf

Acetic acid at 100% does... Something to it.

 

[karimwassef]

acetic acid? same stuff as vinegar?

I was thinking of creating an inverse image of the placements in a 1/8" or 1/16" sheet. Then put that on top of a base 1/8".

Since this build is highly repetitive, I'm looking for a way to speed things up and make sure the pieces consistently line up.

I need to make 10 layers (5 per side) of the 10" x 38" sheet.

<a href="http://s1062.photobucket.com/user/karimwassef/media/0_zpsfxhzxhya.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/0_zpsfxhzxhya.jpg" border="0" alt=" photo 0_zpsfxhzxhya.jpg"/></a>

 

[karimwassef]

This layout repeated 5x per stack (two stacks, one of either side of the tank), results in a head of 5" per side.

I think since there's a pressure drop at the intake and outlet, it's additive, so 10" of head?

That means that the original design was 22 feet of head? Wow... come a long way.

<a href="http://s1062.photobucket.com/user/karimwassef/media/0_zps8mhymn4w.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/0_zps8mhymn4w.jpg" border="0" alt=" photo 0_zps8mhymn4w.jpg"/></a>

<a href="http://s1062.photobucket.com/user/karimwassef/media/1_zpsajotktd0.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/1_zpsajotktd0.jpg" border="0" alt=" photo 1_zpsajotktd0.jpg"/></a>

<a href="http://s1062.photobucket.com/user/karimwassef/media/2_zpsfobov1sv.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/2_zpsfobov1sv.jpg" border="0" alt=" photo 2_zpsfobov1sv.jpg"/></a>

 

[karimwassef]

salty joe - I kept the little deflectors symmetric but I created small offsets in the travel length. The forward direction now has a little more path (more resistance) vs. the turning path.

The first is after the first T.
The right path (same as inlet flow) has 5.5" of path. The left path (turned) has 4.75"

The next turns have the same effect: 2.25" direct vs. 1.75" turned.

And the next: 0.75" direct vs. 0.5" turned.

I really couldn't do any more with 0.25" resolution... The bias becomes 100% one side vs. the other. That deep in, I don't think it has as much of an effect.

 

[karimwassef]

I'm thinking of leaving these stacks unglued to each other. Basically, they're just held down by the box around them and spacers.

 

[dcforester1]

I am following this thread, but not following the idea. I just think its so interesting that someone wants to create something, and I am hoping at some point I figure out what that is LOL

Good Luck Derek

 

[karimwassef]

It's a way to create water motion that effects all the water in the tank at the same time. It moves it all to the right, then moves it all to the left. It does that by circulating the water behind the tank's overflow.

 

[karimwassef]

No feedback on the pressure drop or the latest stackable design?

 

[thejuggernaut]

Hey Floyd- can I etch 1/8" acrylic sheet with muratic acid?

Use a laser cutter. Most things that will melt or haze acrylic makes it craze on the surface.

 

[karimwassef]

Is there a home use laser cutter?

 

[thejuggernaut]

If you had a couple grand to spend you could get this made on a printer.