Large volume laminar flow machine

karimwassef said:
so these are called "cross-flow" fan blades
Click to expand...

I don't know them by that name, but probably everyone has one in their car (with AC)... High efficiency furnaces probably have one too, usually simple called the blower.

I know them as squirrel cage fans.

But yes, available in lots of models im sure.
 
herring_fish said:
I’m doing this for fun so I don’t want to argue about what Webster said a wave is.:lol:
It's a very loose definition. I may not be a monkey but I am a primate.


You don’t want a pulse of water that is likely to go upward rather than forward. Quick waves can be like pulses and long wave can, in some cases, create flow. You have explicitly said this in earlier posts.

Less have fun.
Click to expand...

I know. I didn't mean to sound testy (reading it again - I kinda sound like that)

:)

Yes. I did say that. I can go back and say that I don't fully understand something I thought I did...

This is probably the one gap I still have... longitudinal non-acoustic surface water waves. Was it an illusion caused by an alternating circular current?

It bugged me so much that I reached out to a physics professor friend of mine to get the scoop... he's working on something big, so no call-back. :(

I think the idea is first to get to the point of gyre flow... that's step one. The next step is to work out the alternating circulation without creating waves.
 
Here's the current view. I think this naturally creates relatively directional laminar flow using acrylic, PVC, plastic cross-flow blades, and then 1/8" baffles to spread the flow.

It uses a lot of DC propellers that are reversible and programmable - modified to cross-flow.

Here's the total build - 1' smaller in each dimension. The old design needed a lot of room for internal baffles. The blades do the work here, so it's a lot more compact. Inside is still 3' x 8'

<a href="http://s1062.photobucket.com/user/karimwassef/media/0_zpsaxgwo4ip.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/0_zpsaxgwo4ip.jpg" border="0" alt=" photo 0_zpsaxgwo4ip.jpg"/></a>

<a href="http://s1062.photobucket.com/user/karimwassef/media/1_zpsefzk5oir.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/1_zpsefzk5oir.jpg" border="0" alt=" photo 1_zpsefzk5oir.jpg"/></a>

The eggcrate front is optional now

<a href="http://s1062.photobucket.com/user/karimwassef/media/2_zpsbnbpky4x.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/2_zpsbnbpky4x.jpg" border="0" alt=" photo 2_zpsbnbpky4x.jpg"/></a>

These thin acrylic baffles should be easier to heat shape
<a href="http://s1062.photobucket.com/user/karimwassef/media/3_zpsdg2kutdn.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/3_zpsdg2kutdn.jpg" border="0" alt=" photo 3_zpsdg2kutdn.jpg"/></a>

top view showing the directional acrylic and PVC encasing. There are slots for intake and output

<a href="http://s1062.photobucket.com/user/karimwassef/media/4_zpsw0ibs65j.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/4_zpsw0ibs65j.jpg" border="0" alt=" photo 4_zpsw0ibs65j.jpg"/></a>

I think this shows how the flow is directional and the baffles spread it from the 1" opening per fan to cover the ~2.5" opening.

<a href="http://s1062.photobucket.com/user/karimwassef/media/5_zpsi9ydc4aw.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/5_zpsi9ydc4aw.jpg" border="0" alt=" photo 5_zpsi9ydc4aw.jpg"/></a>

Here's the view from the back - showing the intakes

<a href="http://s1062.photobucket.com/user/karimwassef/media/6_zpsjqh3xe6s.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/6_zpsjqh3xe6s.jpg" border="0" alt=" photo 6_zpsjqh3xe6s.jpg"/></a>

There's 1" of clearance behind the fans

Here's the front outlet slots with acrylic guides

<a href="http://s1062.photobucket.com/user/karimwassef/media/7_zpsvfphigzw.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/7_zpsvfphigzw.jpg" border="0" alt=" photo 7_zpsvfphigzw.jpg"/></a>

This shows the same directional output PVC and acrylic from behind the PVC

<a href="http://s1062.photobucket.com/user/karimwassef/media/8_zpsonnx93ja.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/8_zpsonnx93ja.jpg" border="0" alt=" photo 8_zpsonnx93ja.jpg"/></a>

This is the retrofit of the propeller pump into a cross-flow blade... this one needs testing.

I think this solves all the issues and generates the bulk flow gyre without a lot of risk.

What do you think?
 
I think you are asking a ton out of those motors. The gyre is small, with something like 2 4" x 1" dia fans in it at 50W on the 150, says the internet. The RW20s are about the same wattage as best i can tell. Turning a 14+?" x 2-3" diameter fan will bog them down. Not to mention kill the bearing (if any) and possibly damage the rotor/shaft and rotor well walls without a second bearing on the far end of the fan.

I'm also not sure they will work as drawn, with the openings front and back they can output to either side just as well. I know the gyre is built like this, but thats not how squirrel cage fans are designed to operate. Intake is in the center, axially, output is a tangent. In most applications the housing is a pretty volute as well, though thats harder to make... Intake is still axial though.

If you want lateral intake and output you need a Voith Schneider Propeller, at which point the carriage paddle deal seems easier to implement.

You could make them half as tall, plug up the back opening, and connect them all to a pvc manifold connected to the far side for cross tank intake though. But a big closed loop feeding a manifold diffuser would probably work similarly with much less effort.

On the other hand, if you could get some really long fans like that, as tall as the display is wide, and stack as many of the vertically as fits, you might have a winner. They would need a bearing in the front face of the tank, with the motor in the back on as long a shaft as you can fit to keep the intake as open as possible. With the cross tube as the motor location and intake (with only holes for the fan housings) all the water has to come from the other side. I think the biggest problem here would be that the further along the fan you get, towards the front of the tank, the fan may begin to starve for water... Hmm. And while i did just shoot down my own idea as fast as i typed it i won't remove it because then i just feel silly.
 
Thanks!

Yes, I know the top needed a centering bearing/shaft assembly to keep the blades steady and in place.

Good point about the axial intake! I missed it. I was looking at the gyre, but couldn't resolve intake to output... I can't reproduce a volute exactly, but changing the offset of the PVC casing against the axis of the blades should reproduce the effect?

In terms of horizontal vs. vertical... I thought of that and maybe even doubling up on the pumps- one on either end. The mechanism opening is 3" off the tank floor (sandstorms) and 3" from the water top (waves), so with the water already 3" down in a 24" high, that leaves only 13" of fan needed. Going horizontal takes that almost end to end per fan ~30" on a 36" deep (forward-backward) tank. That felt ... extreme. I also don't know if a two pump-one impeller shaft is a viable DIY even though the attachment is purely a magnetic clutch.

In terms of maintenance, I was working on individual fan housings to remove each at a time. This works vertically but not horizontally... At least not for the bottom fan.

If it's more reliable, then maybe maintenance is at a rack-level. All fans in a removable rack are removed at once for maintenance at the same time.

In terms of gyre, by having 10 fans on each side, I'm basically creating a pull/push that's 10x what a double fan can do. This should be enough to create a powerful vacuum in the ductwork and push the volume. Like a v20 engine- each doing a lot, combined doing a massive job.

The issue with a starving blade end (undriven side) can be solved with baffles... or a manifolds ductwork. The problem is complexity - internal baffles I cannot get to. External baffles are easy to maintain. That's actually why I like these long blades. They already create a sheet of flow. I'm just stacking sheets.

The furthest front fan has to work harder to pull water in, but it's driven, so it doesn't need baffles.

I'll offset the PVC for a volute like casing + axial intake + draw in the axial attachment top bearing + a rack assembly for maintenance.

Thanks for the detailed feedback!
 
Yeah maintenance wise vertical is the way to go indeed. And 30" vs 13" is pretty extreme. Offsetting the fan might be enough, but even centered it will work as long as the only opening is the outlet.

The gyre comment was mainly to say that the fans a 50W gyre has are maybe 1/4 the size together of one of these monsters also on 50W motors. You might need something with real muscle. Vertically you could also house the motors in the space above the tank, with just the shaft going into the tank through the top bearing into a bottom bearing with the fan in between. You wouldn't need to only go after waterproof motors then, opening up options to the entire RC world of BLDC motors among others... Lots of motors with enough power to rotate those things then.
 
That's exactly what I did! I was about to post the new drawings and you're thinking of the same thing.

The RW-20 pumps are pretty powerful.

I changed the opening and ran the axis of the fan blades through the acrylic with teflon rings.

Here's the latest that I think incorporates the concepts into a viable structure that I think can be maintained.

<a href="http://s1062.photobucket.com/user/karimwassef/media/0_zpshxrdmvd2.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/0_zpshxrdmvd2.jpg" border="0" alt=" photo 0_zpshxrdmvd2.jpg"/></a>

So. The ducting is mostly glass with two plastic boxes.. the fan box and the baffle box. These are removable once the 3 glass cap sections are removed. I still haven't figured out how to lock down the glass covers.

<a href="http://s1062.photobucket.com/user/karimwassef/media/1_zpsa3haw2l7.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/1_zpsa3haw2l7.jpg" border="0" alt=" photo 1_zpsa3haw2l7.jpg"/></a>

Here's the view from the inlet duct side

<a href="http://s1062.photobucket.com/user/karimwassef/media/10_zpskah1zupg.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/10_zpskah1zupg.jpg" border="0" alt=" photo 10_zpskah1zupg.jpg"/></a>

and from the outlet

<a href="http://s1062.photobucket.com/user/karimwassef/media/3_zps2lvhdo1b.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/3_zps2lvhdo1b.jpg" border="0" alt=" photo 3_zps2lvhdo1b.jpg"/></a>

Here's the acrylic, PVC, shaft, fan and pump assembly.

<a href="http://s1062.photobucket.com/user/karimwassef/media/6_zpslpsoqvta.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/6_zpslpsoqvta.jpg" border="0" alt=" photo 6_zpslpsoqvta.jpg"/></a>

Here's the offset shaft and acrylic guides into the output slot

<a href="http://s1062.photobucket.com/user/karimwassef/media/7_zpsgdk2dnlv.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/7_zpsgdk2dnlv.jpg" border="0" alt=" photo 7_zpsgdk2dnlv.jpg"/></a>

<a href="http://s1062.photobucket.com/user/karimwassef/media/8_zpsjckdyaqn.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/8_zpsjckdyaqn.jpg" border="0" alt=" photo 8_zpsjckdyaqn.jpg"/></a>

<a href="http://s1062.photobucket.com/user/karimwassef/media/9_zpsohyowtkp.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/9_zpsohyowtkp.jpg" border="0" alt=" photo 9_zpsohyowtkp.jpg"/></a>

The pumps should be removable from the top and serviceable too.
 
You want the pinch point on a volute right after the outlet, in yours it may just mean rotating the offset 90-180 degrees. The idea being to gather more and more water and throw it out the outlet en masse.
 
I see. So this creates impedance against just rotating the flow. It forces the expulsion before the pinch.

So that means that these are not really reversible. Maybe it's an efficiency hit? Or no reversal at all?

How about if the cross-blade fins were straight?
 
As far as i know these are completely not reversible, except if you force water into the fan from the outlet you can make it a generator...

You can look up videos of the gyre run backwards without changing the paddles to the alternate set and see its basically no real flow. The water local to the fan will be blended just like you were using an electric mixer but thats not what you are after.

With straight blades you would make it an impeller, the housing would have to be changed to a unisex version instead of a proper volute and you would have a standard AC pump on your hands. But then the flow is one direction no matter the rotation instead of reversing... Impellers are also axial intake as well.
 
offset to pinch after the opening

<a href="http://s1062.photobucket.com/user/karimwassef/media/0_zpskf0akkup.jpg.html" target="_blank"><img src="http://i1062.photobucket.com/albums/t496/karimwassef/0_zpskf0akkup.jpg" border="0" alt=" photo 0_zpskf0akkup.jpg"/></a>
 
With one side running, the flow naturally reverses through the other side, but I wouldn't be driving it.

I may need to watch any voltage generated in case they turn.

Also need the consider the impedance that an inactive fan to the flow.
 
So, silly question - why could you not simply run gyre pumps in your design, mounted vertically? My understanding is that the Gyre pumps produce their concentrated bulk flow by using the water surface as a constraint, so one gets a very wide, but somewhat shallow flow field across the top of a tank (when mounted and run in a horizontal orientation).

It seems to me that your baffles would serve the same purpose as the water line in a typical Gyre installation, and you probably don't need the PVC shell with intake slots.

Using off-the-shelf gyre pumps would allow you to concentrate your efforts on the configuration of the channel and baffles, without introducing the complexity of messing with modding pump motors and possibly running into issues with self-destructing bearings and/or excessive rotor/stator wear. Not to mention the expense of having a long centrifugal fan custom-made for your application.
 
It looks like the pump motors are above the water line. IDK for sure, but I think those motors need to be submerged-the water being the heatsink for electronics that are cast in the epoxy. I wonder if a pulley system with a single motor on each side would work. Maybe acrylic for the base and top using Teflon bearings and high grade stainless shafts. Just a thought.
 
They submerged. The entire system needs to be submerged and directed with a top baffle for 6" to stop the flow from turning into a wave. The pumps also need water to cool and lubricate.

Off the shelf parts won't take water from the duct channel and push it forward and out. They would just recirculate abs pull water from the left to push to the right... Or top bottom. I need to take water from behind and push forward.

The blades aren't custom. They're actually very common. The final size will depend of the ones I find most economical and serve the function. The PVC allows me to direct the flow through the slots in the acrylic side walls.

The exit baffles just take the ten ~1.25" wide sheets of flow that are separated by ~1.5" of plastic and spreads them to fill the ~2.75" space. This way they don't spin back in the space between layers and cause local vortices or loops. There may be a simpler way to do this.

Also, my preferred pump is an RW20 which is more powerful and a fraction of the cost.
I have a big tank and this design is bigger. I need 20 fans. At the current model prices, that's ~$4000? and still need to be fitted. The RW with blades attached are half of that.

I also need to program and sync them all. I can do that on the RW20s with an Apex mod box or an arduino. No idea if I can run the off the shelf parts that way.
 
salty joe said:
It looks like the pump motors are above the water line. IDK for sure, but I think those motors need to be submerged-the water being the heatsink for electronics that are cast in the epoxy. I wonder if a pulley system with a single motor on each side would work. Maybe acrylic for the base and top using Teflon bearings and high grade stainless shafts. Just a thought.
Click to expand...

While drawing these in, the symmetry forces you to see that concept- but I had to resist... Mechanical structures next to saltwater... Just doesn't click for me. These also need to accelerate and decelerate quickly. I just don't know how to make that work with the inertia if the water flow pushing against the gear it pulley assembly. My past DIY attempts with forced drive pulleys failed when the band or chain jump. An axial shaft with rotated gears may work but back to lubricants, etc...

Would be cheaper :) but probably more expensive later when it fails and I buy the propellers.
 
Gorgok said:
As far as i know these are completely not reversible, except if you force water into the fan from the outlet you can make it a generator...

You can look up videos of the gyre run backwards without changing the paddles to the alternate set and see its basically no real flow. The water local to the fan will be blended just like you were using an electric mixer but thats not what you are after.

With straight blades you would make it an impeller, the housing would have to be changed to a unisex version instead of a proper volute and you would have a standard AC pump on your hands. But then the flow is one direction no matter the rotation instead of reversing... Impellers are also axial intake as well.
Click to expand...

So cross flow blades are non reversible. DC pumps and powerheads with impellers are also non-reversible. Are propeller pumps reversible?

Is the answer to have two in the same housing with large openings to allow the assembly to push and pull?
 
Last edited:
It seams like your making things to complicated.

I have thought how to do this before. Easiest way is to use a closed loop system.

You use alot of bulkhead a bulkhead every 4 sq inches.

And then on the other side of the tank you put your outlets every 3 sq inches. The thing is you may need to brace your tank more or use a thicker glass.

Basic ly your just making a large closed loop and if you wanted you could use two pumps m8xed with outlet and inlets on both side then just get some jeabo DC pumps plug them into a rw controller and have them alternate on a long spaced sequence.

2 jabeos dc 8000 120 each
1 controller 65
12 bulkheads and some plumbing and Teflon and your done.
 
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