Large volume laminar flow machine

[karimwassef]

It says you can use it in salt water..
For speed control you would just need a VFD to run it off of..(Single Phase of course)
But I guess between the cost of the "pump" and the VFD, and a Micro-PLC,,you would probably be about the same cost-wise.. Also it isnt reversable so,, theres another problem..
Would make a hell of a powerhead though...lol....talk about cleaning the gunk out of a tank

The difference between salt water safe and reef aquarium safe is what you're looking to keep "safe".

Salt water safe in the ocean means the pump won't deteriorate much in salt water. It doesn't say what it'll be releasing to the water. Think of a n outboard gasoline boat motor- definitely salt water safe... Not going in a reef tank.

 

[karimwassef]

Karim - I didn't read through the whole thread (bit late for that tonight), but did read through the first 3 pages and the last 2, so I think I understand what you're trying to accomplish.

And there's a way to do it without pumps. And, a very long time ago, I saw it in action. Essentially, you install the "U" shaped channel as you've illustrated in the back of the tank, but the channel is open at the top, and is taller than the tank. In it, a large paddle is installed that forms a fairly close seal to the sidewalls of the channel. This paddle is actuated with a variable-speed electric motor and a cam. The cam bears on the top of the paddle (above the paddle's pivot), until it goes far enough to slip out, whereupon the paddle returns by spring force.

What this does is move a very large amount of water en masse, raising the water level in front of the paddle by 5 or 6 inches. This surge travels down the channel, through the diffuser and into the tank. The spring return of the paddle causes a surge in the opposite direction.

My memory of this is fuzzy; I saw it at an engineering department at a University some 30 years ago. But the water movement in this tank was a very close model of the surge that occurs on a reef crest, and IIRC, that was what its intended purpose was.

Thanks and welcome!

I think the idea of the duct is pretty solid. The actuation by pump or mechanical paddle is a question of design competency and physical space available.

I am a much better programmer and electronics designer than I am a mechanical designer. To find the right balance in design to use weight and springs to move the water volume... is too risky for me and I expect it'll take a lot of room.

The surge is a good idea, but it needs a substantial diffuser to convert that into laminar bulk flow. I have a massive surge (30g x 2 opposing outlets in a 380g DT), but the 2" PVC isn't getting the job done. The surge has the energy... Converting it to laminar is the trick.

 

[karimwassef]

This is very similar to what i Remember from Newport Aquarium Wave TANK....
Thou i was not ALLOWED BEHIND THE SCENES (BOOHOOO) to see how they done it all.. I know there was baffles in each end...

You are in the same kinda Thinking as this thread has been....

Nice work on your tank. If you have a build thread please post ..

Erica Renee.. The Geeky CHIC With lots of power tools..:wavehand:

Where have you been? I needed a carpenter when building my wooden model (two pages ago). Luckily, I'm swamped with work so I didn't get to it yet.

My wood question - I need really really straight plywood 1/4" to make straight vertical baffles on a 1/2" base. I don't have a planing machine or a router...

Any magic answers?

 

[ericarenee]

Where have you been? I needed a carpenter when building my wooden model (two pages ago). Luckily, I'm swamped with work so I didn't get to it yet.

My wood question - I need really really straight plywood 1/4" to make straight vertical baffles on a 1/2" base. I don't have a planing machine or a router...

Any magic answers?

1/4 plywood will warp . masonite or or duro rock is what comes to mind as I'm typing this
As far as to get it to stay a cheap table saw with dato blades .
Dato blades are just staked saw blade to make wider Grove

Life been occupied my last few days will think more on 1/4 inch materials .but search duro rock .[emoji3]

Kinda at the bar now oops

 

[karimwassef]

Found durock

http://m.homedepot.com/p/DUROCK-Next-Gen-1-4-in-x-3-ft-x-5-ft-Cement-Board-170219/202817897/

I assumed can cut this with a jigsaw or table saw?

 

[JamesHolt]

Think cheap ceramic type floor tile for the mockup

 

[karimwassef]

Cheap ceramic tile needs expensive saws to cut. My choice of wood was to make it easy.

I think erica's bar-sourced posting was about a backer-board type material?

 

[salty joe]

Looking at all the different iterations, I can't see a wave not happening unless you either run the opposing flows out of tune or the display is covered. How about a hinged glass cover with bulb type weather stripping for the display?

 

[dkeller_nc]

Thanks and welcome!

I think the idea of the duct is pretty solid. The actuation by pump or mechanical paddle is a question of design competency and physical space available.

I am a much better programmer and electronics designer than I am a mechanical designer. To find the right balance in design to use weight and springs to move the water volume... is too risky for me and I expect it'll take a lot of room.

The surge is a good idea, but it needs a substantial diffuser to convert that into laminar bulk flow. I have a massive surge (30g x 2 opposing outlets in a 380g DT), but the 2" PVC isn't getting the job done. The surge has the energy... Converting it to laminar is the trick.

Yeah, there's no question running a bunch of propeller pumps in reverse sync is simpler in terms of being able to buy already-engineered components off of the shelf.

The advantage to the paddle type of set-up is that by definition, the flow's already laminar because all of the water in the channel is moved at the same time, and at approximately the same velocity. The other difference is that water pumps are very low torque, high velocity devices. The variable speed gearmotor that moves the paddle is a very high torque, low velocity device. So a very large amount of water can be moved all at the same time with little or no turbulence.

With respect to your mock-up; if I understand correctly you want to build the whole thing - channel, diffusers and tank to get the dimensions right before building it in acrylic and/or glass. You could do this in a fairly straightforward manner with 3/4" and 1/4" marine grade plywood (3/4" for the tank/channel walls and 1/4" for the internal components. Properly built, the external walls won't warp if the corner joints are done carefully, and as long as the internal 1/4" thick components are surrounded on all surfaces by water, it won't warp either. Where you get into trouble is relatively thin plywood that has water on one side and is dry on the other - the differential water absorption will warp the sheet as Erica notes.

As far as working with the material, there's a relatively less expensive way than purchasing a table saw. And a whole lot safer if you're not familiar with tables saws - the number one woodworking tool for injuries is the router, followed very closely by table saws. And the nature of those injuries is usually amputation.

Instead, you can get a decent quality circular saw (sometimes called "Skil Saws") with a plywood cutting blade at the home store, and a parallel guide/clamp. The parallel guides come in various lengths from 24" all the way to 112", and is a convenient way to make perfectly straight cuts in plywood. They can be purchased cheaply or expensively, depending on quality and features.

 

[sculpin2]

Karim,

Only one side of the pumps are running at a time (except during the small pump nadir phase). Otherwise, I am willing to bet that they will be causing too much turbulence/sucking air.

I've been wanting to build a faux tidal tank since the early 2000's, when I had to leave the hobby secondary to the birth of my children and work constraints. I'm calling this the 1.0 version, as I am sure it will have bugs to work out. It's a true experimental setup, as I am not that worried about aesthetics. Plus, $40 tank...

In terms of the baffles, I just couldn't come up with a good way to redirect the flowing water/pressure wave without having a bunch of unsightly powerheads in every corner. I plan on making the space behind the baffles a "biologic" area with liverock and easy to care for corals (GSP's, polyps).

By the way, the other impetus with this tank was to minimize leak risk. My wife is none too happy with recent saltwater spillage, and thus the "sumpless" approach.

Sorry I didn't join this thread earlier. I have been working on this build for a couple of months and wanted to show my work!

Mike

 

[ericarenee]

Found durock

http://m.homedepot.com/p/DUROCK-Next-Gen-1-4-in-x-3-ft-x-5-ft-Cement-Board-170219/202817897/

I assumed can cut this with a jigsaw or table saw?

Yes Just be away it prob has silcates in it.. Very easy to cut and even bend to Radious...

See the pond in my Avatar image. The Radius is Masonite . Painted part.. with the Durock Band at top and Bottom where SLATE Tile will go .

The other thing you could use..... Contact cement Two back to back pieces of FRP PANELS TOGETHER.... They would be 100% water tight. frp is super strong and would be quite easily to work with as well.

OHH WAIT....... OPEN CELL PLASTIC Sign board........ THIS THIS THIS

THE PLASTIC SIGN BOARD WOULD BE PERFECT.......



OHH You can cut Duro Rock with a Skill saw i use a worn out Carbide trim blade... Some use a plywood blade . either or works . JUST Do not use a 30.00 new blade because it will be TOAST.......

You can cut with Angle grinder with a diamond blade but if you do i suggest you water source . WEAR A MASK THE DUST HAS SILICATES . AND THEY DO Cause cancer .

 

[ericarenee]

Cheap ceramic tile needs expensive saws to cut. My choice of wood was to make it easy.

I think erica's bar-sourced posting was about a backer-board type material?

Yes but i changed my mind to the Corrugated plastic With a Plywood box.

Do not use hardi-Backer board. it will de laminite in water

 

[prop-frags]

This is a very thought-provoking and ambitious design challenge.
I confess to not reading the entire thread, nor being a physics major, so my comments are not well-grounded. It does seem to me that Professor Clive Greated's video does show that the motion you experience while snorkeling is indeed a wave. I suspect that the laminar 'inhale/exhale' movement of the water is a function of the wavelength and depth.

As far as how to practically duplicate it in a very small tank without using standing wave design is probably not achievable. The water moving back and forth in the tank is a wave, and as that wave strikes the end of the tank, that energy needs to be absorbed, reflected, scattered, etc. I think the closer you can get to creating a standing wave with a very long wavelength and short amplitude, you will get closer to the desired effect.

 

[karimwassef]

Wow, welcome to all the new contributors!!

In terms of wave vs not a wave -

A transverse wave is motion of energy where the particles don't actually move in the direction of energy. It's why you can be floating in the ocean and have a wave come at you at 20mph, it lifts you up 6ft in the air and then brings you down before it continues on its way. The wave has moved forward but you, and the water you're in haven't...

A standing transverse wave is where the wave bounces back or two waves collide in a controlled space so they no longer exhibit a propagating wave. So, instead of the wave pushing you up and down while it moves forward, the waves cancel and now: you move up and down and there is nothing moving forward or backwards.

A longitudinal wave (like a sound wave) is one where the up/down wave action happens to be forward/backward instead. The particles still don't go anywhere in the end, only the wave actually goes. Locally, the particles move forward and backward due to the pressure that they feel as the wave passes them.

A standing longitudinal wave just has particles moving forward and backward without a propagating wave. If you've ever watched people making styrofoam balls dancing with sound.. That's what it is. In concept, this looks like what I want... The problem is that water is hard to compress and acoustic waves in water move very very fast. I went down this path for a few days - it may still be viable but out of scope for now.

All these waves are just the beginning for a real water wave. In water that has an exposed top, a wave is neither transverse or longitudinal only. Basically, the parts of water pushing air are moving differently that water pushing water... This actually causes water to not just move up and down, or forward/backward. It makes the particles go in vertical circles of different sizes as you go up and down the wave's height... This results in a trochoidal wave...
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/watwav2.html

So is an alternating flow the same as a wave? Take the gyre that Mike is working on. Different time scale but it's a circular flow that alternates. There's a wave that gets it started, but once it's running, the flow is just a loop. No up/down. No front/back. So I'd say it's not a wave until he reversed the flow. At that point, the wave is the result of acceleration/deceleration. The reverse flow in the end is also not a wave after it settles.

Keep the idea that a wave moves a lot forward but the particles only go up/down. A standing wave has no motion forward, you only have the particles going up/down.

So an alternating gyre (looping flow) is closest to what I'm trying to do.

Open vs. closed top... Because water is mostly incompressible, if it has no air to push out into, if you push it with a piston or pump in a closed loop sealed pipe, it will all go... Bulk flow. It you open it to air by drilling a hole, it will push out into the air instead. With an open tank, the water pushes up and makes a surface wave. This is why I seal the ducting n the back and use baffles to direct the flow forward with submerged outlets and inlets.

Another significance of the gyre concept is where the water goes when you pump it in. With my surge now, the water level rises by 1.5" before my weir end to end overflow brings it under control. In a gyre, the should be no net upward wave. The water being pumped in is also being pulled out.

But... If you take an example of a very long tank. Say it's s mile long... If you pull water from one end and push it at the other end... Starting the push/pull will not cause the entire bulk of water to move. On the pushing end, a wave of flow will move in. At the other end, a wave of flow will get sucked in. At some point, those waves meet and cancel. Then after enough time of flowing continuously, the bulk will flow without a wave. Basically, the waves are the result of the initiating forces, not the steady flow.

So bulk flow isn't a wave. Making an alternating bulk flow that alternates without creating waves... That's the tricky part.

 

[ericarenee]

Wow, welcome to all the new contributors!!

In terms of wave vs not a wave -

A transverse wave is motion of energy where the particles don't actually move in the direction of energy. It's why you can be floating in the ocean and have a wave come at you at 20mph, it lifts you up 6ft in the air and then brings you down before it continues on its way. The wave has moved forward but you, and the water you're in haven't...

A standing transverse wave is where the wave bounces back or two waves collide in a controlled space so they no longer exhibit a propagating wave. So, instead of the wave pushing you up and down while it moves forward, the waves cancel and now: you move up and down and there is nothing moving forward or backwards.

A longitudinal wave (like a sound wave) is one where the up/down wave action happens to be forward/backward instead. The particles still don't go anywhere in the end, only the wave actually goes. Locally, the particles move forward and backward due to the pressure that they feel as the wave passes them.

A standing longitudinal wave just has particles moving forward and backward without a propagating wave. If you've ever watched people making styrofoam balls dancing with sound.. That's what it is. In concept, this looks like what I want... The problem is that water is hard to compress and acoustic waves in water move very very fast. I went down this path for a few days - it may still be viable but out of scope for now.

All these waves are just the beginning for a real water wave. In water that has an exposed top, a wave is neither transverse or longitudinal only. Basically, the parts of water pushing air are moving differently that water pushing water... This actually causes water to not just move up and down, or forward/backward. It makes the particles go in vertical circles of different sizes as you go up and down the wave's height... This results in a trochoidal wave...
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/watwav2.html

So is an alternating flow the same as a wave? Take the gyre that Mike is working on. Different time scale but it's a circular flow that alternates. There's a wave that gets it started, but once it's running, the flow is just a loop. No up/down. No front/back. So I'd say it's not a wave until he reversed the flow. At that point, the wave is the result of acceleration/deceleration. The reverse flow in the end is also not a wave after it settles.

Keep the idea that a wave moves a lot forward but the particles only go up/down. A standing wave has no motion forward, you only have the particles going up/down.

So an alternating gyre (looping flow) is closest to what I'm trying to do.

Open vs. closed top... Because water is mostly incompressible, if it has no air to push out into, if you push it with a piston or pump in a closed loop sealed pipe, it will all go... Bulk flow. It you open it to air by drilling a hole, it will push out into the air instead. With an open tank, the water pushes up and makes a surface wave. This is why I seal the ducting n the back and use baffles to direct the flow forward with submerged outlets and inlets.

Another significance of the gyre concept is where the water goes when you pump it in. With my surge now, the water level rises by 1.5" before my weir end to end overflow brings it under control. In a gyre, the should be no net upward wave. The water being pumped in is also being pulled out.

So bulk flow isn't a wave. Making an alternating bulk flow that alternates without creating waves... That's the tricky part.

:deadhorse1:



Nice Refresh ....... I may have the stuff to build a mock up on a very small scale with two wave pumps. ..

Do you think a 30x12 inch tank would work.....

 

[karimwassef]

Looking at all the different iterations, I can't see a wave not happening unless you either run the opposing flows out of tune or the display is covered. How about a hinged glass cover with bulb type weather stripping for the display?

The idea is to push/pull exactly out of sync so the ends are guiding the bulk water to circulate in one direction (gyre).

The problem is when we go to reverse the flow. This is why I went with a sine wave to slowly bring the flow to zero before reversing.

A fully sealed system wouldn't have waves, but the core ideas of today's systems- overflow, open sump, etc... All would need to be recreated in a sealed system.

I'm sure a billionaire somewhere has had his jet fitted with an aquarium and hired an engineer to solve these problems... Just out of scope for me now.

 

[karimwassef]

Erica- yes.. The horse is dead but we have lots of new contributors to share it with

When I wanted to scale, I went as small as I could. The problem is that the scaling effects the properties of the fluid you need to use. If you go too small, you need to use things like ether or acetone to simulate a scaled down version of viscosity and surface tension ... That effect flow.

I went with 24 x 48 as a middle ground. I think 12 x 24 would be getting to close to a different fluid. But!!! Anything to get started is better than nothing.

 

[karimwassef]

dkeller- thanks! I have a circular saw and handheld circular saw. I can also use my dad's table saw.

I've built plenty of wood boxes but not ones with small features that need to be perfectly vertical and thin. Thanks for the help.

erica- I like the idea of sign plastic! I think I even have some from another project. I can see cutting grooves in the bottom board to insert it into? Then seal with water sealant?

 

[karimwassef]

This is a very thought-provoking and ambitious design challenge.
I confess to not reading the entire thread, nor being a physics major, so my comments are not well-grounded. It does seem to me that Professor Clive Greated's video does show that the motion you experience while snorkeling is indeed a wave. I suspect that the laminar 'inhale/exhale' movement of the water is a function of the wavelength and depth.

Thanks prop. I think that wave pool is incredible. I think the inhale/exhale has a wave component, but the physical push/pull flow is not a transverse wave.

However, I think this wave pool is awesome enough to share here.

http://www.flowavett.co.uk/

https://youtu.be/RHTcSKkUU8U

https://youtu.be/WffR6HrEqTA

and this one shows the actuators, dampeners, recirculating ductwork, guides, baffles and injection fan-pumps...

https://www.youtube.com/watch?v=ePB7PVA42Fs

Now this one shows the difference between wave makers and flow/current generators... both employed in this pool

https://youtu.be/bCNPkq1Oqi4

"The 5m deep basin contains 2.4 million litres of fresh water and is circumferentially ringed by 168 absorbing wave makers. Additionally, twenty-eight submerged flow-drive units can simultaneously and independently drive current through the 2m deep test volume in any relative direction, with maximum current velocities of up to 1.6 metres per second."

What I want is to duplicate the flow generators... using the same methods, actually... propeller pumps, ducting and baffles!

so... millions of dollars of engineering vs. reefcentral crowdsourcing = same result.

 

[karimwassef]

found this today...

https://www.youtube.com/watch?v=8gDgkNCdgoE

anyone use this device?

https://www.youtube.com/watch?v=uioiwfuEpTo

IMO, It's not that different from a powerhead, except both intake and outlet are wide and straight to get away from the pipe output most pumps generate.

If it works well, it might be that an array of these pumps would direct flow more directionally than an array of propellers in my outlets.

It has an "alternating gyre (reversible) mode" but in that case, only one of the two rotors is pushing at a time.

The flat propellers/rotors also only have 90 degrees for intake and 90 degrees for outlet. That can complicate the structure around them...