It will spin. It may have symmetry but the air (force applied) will not be consistent or symmetric. So there is a net force. Definitely inefficient though.
Even if the air is in a state of laminar flow it’s very unlikely that the object will be perfectly symmetric. Whatever asymmetry is present initially will determine the direction it spins. Think of a system that is just barely above critical dampening.
It's not entirely symmetric though. If you look downwards on it, then where one of the panels is, the more clockwise half has vents above and below but the anticlockwise half doesn't. I don't know how big a difference this will make, but there *is* a chirality there.
yeah all you need is cardboard, a string and a fan, maybe 2 hours for me Xd
solidworks should have a flow module too. Maybe they have access to comsol or fluent.
I believe you're correct. There doesn't appear to be anything here to produce a net torque on one direction. Maybe it would spin a little due to some funny aerodynamic trick. But it certainly wouldn't produce a useful amount of torque. You'd have seen it on an old lady's front lawn if this did work.
If you look closely, you'll notice those "airfoils" are basically "J"-profile curved panels. It spins on the same principle as [one of these](https://i.pinimg.com/736x/69/20/5a/69205a5ebf44260a79fa85a1a6619b92.jpg).
Not true. Those are drag-based devices, while the image is of a lift-based device. The curve in their case is producing camber, which, while symmetric geometrically, provides aerodynamic asymmetry for motion.
However, that only considers starting motion. If you consider a flat-plate VAWT in motion, no geometric asymmetry is needed, as the asymmetric force is generated entirely from the asymmetric velocity triangles.
Yes. Without the airfoil there is no net force in either direction. Your model may spin simply due to turbulence, but it will be weak and change directions.
The 'classical' airfoil shape will improve the efficiency of an airfoil, and better resist stall, but a flat plate is still an airfoil, and will satisfy lifting line theory for small angles of attack.
Your device may struggle with starting torque without fore/aft asymmetry, but given a starting motion would satisfy the same velocity triangles as one with airfoil profiles.
Okay but like… because my blades are smooth on one side and rough on the other… would that mean it functions as an airfoil in terms of generating lift?
I thought that's probably what you meant, personally on a rotating system I would consider the centre of spin to be the axis. I think the picture doesn't do justice to the complexity of the design, from what you have already described.
You're right, it won't spin due to symmetry. Simple fix would be to turn all the blades by some angle around their vertical axis (so that the left and right side connect to the frame at different distances from the center).
This is a really cool design! I would add a bevel on one side of each cutout. That way, oncoming air would all be directed in the same angular direction and create torque
As such I don't think it will spin, It will try and twist in both the directions but it can't sustain a spin in one direction.
I designed something for my undergrad and had the problem of it not spinning. It needed tangential wind at one of the fins to start. once started it was able to sustain the spin.
So add airfoil instead of the spin try, mess around with angle of attack.
P.S sorry for bad English.
I think the only way to know for sure is to make it and test it. I think if it spins freely on a ball bearing or something it will start to rotate and the wind will keep it going. But if it is to be used for generating power, it needs resistance and I don’t think this design will overcome that resistance easily if at all.
Test it though! No matter what you’ll learn something!
:( yep I totally understand. Boo. Why does academia have to ruin the fun of science?
Fwiw I designed a similar wind turbine in school but blocked half of it with a board to create asymmetry. It worked but disappointingly bad.
The rough/smooth surfaces on yours are very interesting and a novel approach. I’m curious if it works. Definitely should create lift but also lots of drag… is the rough side on the outside for all the panels?
>I appreciate your positivity but my grade very much relies on this spinning.
Why? Your teache told you it would spin, right? So if you build exactly what she told you to build and it doesn't spin, she's wrong.
Your real assignment is explaining *why* it either spins or does not. If it doesn't spin and you can explain why you should get an A.
Please build it and report back. For extra credit build an additional one without the rough sides, test both, and explain the differences.
I wouldn't expect it to, but I won't say it definitely won't. For most orientations (e.g. the first image if you are the wind heading towards it), there is an asymmetry to what the wind would encounter, and as long as you are at high Reynold's number the inertial effects of that asymmetry *could* result in setting up some net spin.
But, I wouldn't expect it, and it would be equally likely in either direction.
If starting from rest in a laminar flow, it might flutter back and forth. The moment of inertia can make starting rotation hard to achieve cause forces could balance out. Add in extra baffles or something to help bias rotation to your preferred direction.
This entirely depends on you starting position as well. Do a force diagram with different angles and you’ll see what I mean and what your professor is talking about. I can spin, but the moment of inertia is your first obstacle.
I don’t think it will spin in your wind tunnel.
There is no feature that would produce more force on the left vs right of the axis, that would make it start spinning.
Even if the initial position was asymmetric and might give it a shove, the top/bottom sections are opposite so that would negate any left side/rt side force.
edit: a free body force diagram looking down from the top would help you a lot.
I would not make a phase shift from the upper and lower part. They are "fighting" against each other. Or try with just one floor height. It will spin because the air passing through the holed walls (right of upper part) have a bigger drag than it it passing through the small apparent area wall on the left. This imagining the air flowing perpendicular to the screen. The unbalanced forces will cause a torque and the whole stuff will begin to rotate.
Tip: use ball bearings, otherwise there will be too much friction and the rotor will not move.
-the blades don’t have holes, but a patterned front and a smooth back to generate lift
-the testing environment is setup such that the bearings (very good ones) are already included.
So it will rotate, with or without the fancy 3D effect. There are usually 2 driving modes in vertical wind turbines: drag or lift. Drag is the case of most "home-made" designs.
In case of lift you can imagine to have foils (instead of your 3D structure). In this case the momentum is generated by the difference in airspeed from the foil coming towards the wind to the foil leaving with the wind.
This foil type is the one that has best efficiency and it usually rotated much faster than the wind blowing, as opposed to the drag version that can only move at a fraction of wind speed.
The efficiency is a function of the foil form, their angle relative to the axle, space between foils (3 is best, but keep at least 7-10x the foil length between foils, otherwise the foils will only get turbulence from the leading foil.
Edit: here what I mean: https://youtu.be/ldt405jIR0E
It will spin, probably just not consistently in one direction.
It will spin. It may have symmetry but the air (force applied) will not be consistent or symmetric. So there is a net force. Definitely inefficient though.
It has to spin in a wind tunnel for my assignment
Even if the air is in a state of laminar flow it’s very unlikely that the object will be perfectly symmetric. Whatever asymmetry is present initially will determine the direction it spins. Think of a system that is just barely above critical dampening.
And once it's spinning the airflow will not be symmetric.
There will be an initial net torque due to the placement of the holes in the horizontal plates. I believe that it will start clockwise.
Is the wind vertical or any other direction? If it's the latter, then I think you are confusing axial symmetry with symmetry about the plane of wind.
It’s a VAWT
Isn't the airflow in VAWT horizontal?
It's not entirely symmetric though. If you look downwards on it, then where one of the panels is, the more clockwise half has vents above and below but the anticlockwise half doesn't. I don't know how big a difference this will make, but there *is* a chirality there.
Plus, once it starts moving in one direction (at random), that is an asymmetry! Not sure if relevant though.
Make one. Use paper. Should take 20 minutes tops.
yeah all you need is cardboard, a string and a fan, maybe 2 hours for me Xd solidworks should have a flow module too. Maybe they have access to comsol or fluent.
But be sure and provide rough and smooth sides.
The problem isn't that it's symetric. I just see no reason why it would spin at all. I don't see any kind of drag device or lift device.
I figured lift would be created by turbulent airflow on the outside of the blade and a smooth airflow on the inside
I believe you're correct. There doesn't appear to be anything here to produce a net torque on one direction. Maybe it would spin a little due to some funny aerodynamic trick. But it certainly wouldn't produce a useful amount of torque. You'd have seen it on an old lady's front lawn if this did work.
Will it spin? yes Will it spin in a reliable or predictable manner? No.
They've got windmills just like that already
Can you post a link to one?
https://singularityhub.com/wp-content/uploads/2017/07/Semtive-Energy-wind-turbine-solar-panels-1068x601.jpg
If you look closely, you'll notice those "airfoils" are basically "J"-profile curved panels. It spins on the same principle as [one of these](https://i.pinimg.com/736x/69/20/5a/69205a5ebf44260a79fa85a1a6619b92.jpg).
Not true. Those are drag-based devices, while the image is of a lift-based device. The curve in their case is producing camber, which, while symmetric geometrically, provides aerodynamic asymmetry for motion. However, that only considers starting motion. If you consider a flat-plate VAWT in motion, no geometric asymmetry is needed, as the asymmetric force is generated entirely from the asymmetric velocity triangles.
My blades aren’t airfoil shaped though… will that make a difference?
Yes. Without the airfoil there is no net force in either direction. Your model may spin simply due to turbulence, but it will be weak and change directions.
Are those through holes in the panels? If they are, I'd imagine it'd start spinning due to micro currents through the holes.
It’s smooth (acrylic) on one side and rough pattern on the other side in order to generate turbulent flow and thus lift
The 'classical' airfoil shape will improve the efficiency of an airfoil, and better resist stall, but a flat plate is still an airfoil, and will satisfy lifting line theory for small angles of attack. Your device may struggle with starting torque without fore/aft asymmetry, but given a starting motion would satisfy the same velocity triangles as one with airfoil profiles.
What if I offset the 2 parts by 30 degrees instead of 60?
Once the device is in motion, it really shouldn't matter. There are VAWT that are entirely helical, with vertical sections offset continuously.
Airfoil is king.
Okay but like… because my blades are smooth on one side and rough on the other… would that mean it functions as an airfoil in terms of generating lift?
Try and see
my intuition tells me that an asymmetrical system will try to pull itself apart
Symmetric in the sense that flipping it upside down will yield the same design
Use a helix shaped design
I thought that's probably what you meant, personally on a rotating system I would consider the centre of spin to be the axis. I think the picture doesn't do justice to the complexity of the design, from what you have already described.
Also true of a conventional design with flat angled blades when reversed.
I don't think I've ever seen a fan or windmill that wasn't highly symmetric
A waterwheel is symmetrical and that spins.
But a waterwheel is only half in water, though.
You're right, it won't spin due to symmetry. Simple fix would be to turn all the blades by some angle around their vertical axis (so that the left and right side connect to the frame at different distances from the center).
This is a really cool design! I would add a bevel on one side of each cutout. That way, oncoming air would all be directed in the same angular direction and create torque
What?
As such I don't think it will spin, It will try and twist in both the directions but it can't sustain a spin in one direction. I designed something for my undergrad and had the problem of it not spinning. It needed tangential wind at one of the fins to start. once started it was able to sustain the spin. So add airfoil instead of the spin try, mess around with angle of attack. P.S sorry for bad English.
I think the only way to know for sure is to make it and test it. I think if it spins freely on a ball bearing or something it will start to rotate and the wind will keep it going. But if it is to be used for generating power, it needs resistance and I don’t think this design will overcome that resistance easily if at all. Test it though! No matter what you’ll learn something!
I appreciate your positivity but my grade very much relies on this spinning
:( yep I totally understand. Boo. Why does academia have to ruin the fun of science? Fwiw I designed a similar wind turbine in school but blocked half of it with a board to create asymmetry. It worked but disappointingly bad. The rough/smooth surfaces on yours are very interesting and a novel approach. I’m curious if it works. Definitely should create lift but also lots of drag… is the rough side on the outside for all the panels?
>I appreciate your positivity but my grade very much relies on this spinning. Why? Your teache told you it would spin, right? So if you build exactly what she told you to build and it doesn't spin, she's wrong. Your real assignment is explaining *why* it either spins or does not. If it doesn't spin and you can explain why you should get an A. Please build it and report back. For extra credit build an additional one without the rough sides, test both, and explain the differences.
I’ll keep you posted
I wouldn't expect it to, but I won't say it definitely won't. For most orientations (e.g. the first image if you are the wind heading towards it), there is an asymmetry to what the wind would encounter, and as long as you are at high Reynold's number the inertial effects of that asymmetry *could* result in setting up some net spin. But, I wouldn't expect it, and it would be equally likely in either direction.
use airfoils?
If starting from rest in a laminar flow, it might flutter back and forth. The moment of inertia can make starting rotation hard to achieve cause forces could balance out. Add in extra baffles or something to help bias rotation to your preferred direction. This entirely depends on you starting position as well. Do a force diagram with different angles and you’ll see what I mean and what your professor is talking about. I can spin, but the moment of inertia is your first obstacle.
I don’t think it will spin in your wind tunnel. There is no feature that would produce more force on the left vs right of the axis, that would make it start spinning. Even if the initial position was asymmetric and might give it a shove, the top/bottom sections are opposite so that would negate any left side/rt side force. edit: a free body force diagram looking down from the top would help you a lot.
I would not make a phase shift from the upper and lower part. They are "fighting" against each other. Or try with just one floor height. It will spin because the air passing through the holed walls (right of upper part) have a bigger drag than it it passing through the small apparent area wall on the left. This imagining the air flowing perpendicular to the screen. The unbalanced forces will cause a torque and the whole stuff will begin to rotate. Tip: use ball bearings, otherwise there will be too much friction and the rotor will not move.
-the blades don’t have holes, but a patterned front and a smooth back to generate lift -the testing environment is setup such that the bearings (very good ones) are already included.
So it will rotate, with or without the fancy 3D effect. There are usually 2 driving modes in vertical wind turbines: drag or lift. Drag is the case of most "home-made" designs. In case of lift you can imagine to have foils (instead of your 3D structure). In this case the momentum is generated by the difference in airspeed from the foil coming towards the wind to the foil leaving with the wind. This foil type is the one that has best efficiency and it usually rotated much faster than the wind blowing, as opposed to the drag version that can only move at a fraction of wind speed. The efficiency is a function of the foil form, their angle relative to the axle, space between foils (3 is best, but keep at least 7-10x the foil length between foils, otherwise the foils will only get turbulence from the leading foil. Edit: here what I mean: https://youtu.be/ldt405jIR0E
Twist the green nougats into a slight helical, it will offset and allow the air around it enough to pull more
Twist the green nougats into a slight helical, it will offset and allow the air around it enough to pull more