When comparing the efficiency of different wind turbine blade designs, [AdamEnt] found using a hair dryer wasn’t the best tool for the job. Enter his new 3D-printed wind tunnel.
After several prototypes, [AdamEnt] decided on a design that exploits slicer infill to create a flow straightener without having to do any tedious modeling of a lattice. Combined with a box on both ends of the straightener to constrain the flow, he has a more controllable air source with laminar instead of turbulent flow for testing his wind turbines.
The BLDC motor driving the air is attached to a toroidal blade of MIT fame. We get a little bit of the math behind calculating wind turbine efficiency and see a quick test of a blade placed next to the outlet of the air source at the end of the video.
If you’re planning on building your own wind tunnel, we’ve covered a few. We’ve even seen one that goes up to Mach 20, although that probably wouldn’t be useful for wind turbine design!
I first saw the video was 14 minutes and thought, I don’t have the time for that.
But I think he did a great job explaining the problems and solutions encountered, as well as the reasons for redoing his initial experiment.
TL;DR: vertical turbine blades get pushed by the wind on one side, but braked by the wind on the other, so you need to hit it evenly on both sides to simulate real wind.
This is a good first step, but I want to see efficiency here eventually — or even just how much power you can get out of each of the designs.
Yeah!
this is another of those examples of “you used 3d printing for WHAT???” wind tunnels and air flow straighteners have been made out of cardboard, wood, plastic, what-have-you, for years. it isn’t such a complicated shape so it’s easy to build it out of bulk materials.
i always marvel when someone wants a flat smooth 150mm x 150mm x 2mm plate and the best tool they can think of is a 3d printer. people go through so much filament!
I mean, I get your point, I used to think the same, but if you need that plate right here right now for a prototype and you don’t have any other materials around it’s the easiest way to get it. Made from PLA this would weight ~56g which is not a lot at all (<$1 in filament).
So spend your money on flat stock that can sit on a shelf for a decade instead of filament you have to keep in a climate controlled box.
“I needed to do it with what I had on hand” is a great excuse for a trail fix, where you know it is temporary and literally need to fix it or walk out.
It is NOT an excuse for 3d printing a flat plate because you WANT it now and we’re unprepared.
3d printers are great at a few specific jobs.
They are also hugely wasteful, and encourage bad behavior when you can push a button and get a thing that SHOULD be made another way.
hahah i totally agree with you but i wouldn’t go quite so far as “should”. i know some people take themselves more seriously than i do but from my perspective i’m just another fool using whatever tool is in my hand at the moment, like everyone else.
personally the #1 thing that motivates me is i attend my prints. i run downstairs and visually inspect the printer every 10 minutes. i have to come manually advance the coil of filament, or eventually it jams. i could fix that but i want to maintain this hard limit that i do not run it unattended. so i hardly ever print anything more than 2 hours worth in one step.
plus, my printer has a small 4″x4″ build area and again i could adjust that but i don’t *want* to print big things and wait for them. so i save my printer for small cases and brackets, little things. i have a basement so i have a good amount of space for scraps of lumber, pipe, metal, fasteners, etc.
but as far as “the right tool for the job”, for this i’d probably use posterboard cereal boxes, blue painter’s tape, and a stick of thin wood around the perimeter one way or the other for shape. and my real concession to quality and durability would be that i would at least use a ruler to make the cuts straight. :)
How about something a bit simpler. At the Langley Cryogenic Wind Tunnel, they use tens of millions of drinking straws glued together to make a flow straightener. The results were better than they could have imagined. Lower pressure drop, and far better laminar air flow.
Your flow straightener is too coarse to produce laminar flow in a short distance. Window screen would be a better choice. However, a much simpler solution is to reverse the motor direction so the test chamber has an open intake. The Wright brother’s table-top wind tunnel was open intake and good enough to accurately measure the lift of wing cross-sections.
Also, the test turbine needs to be significantly smaller than the test chamber in order to avoid interactions between their boundary layers. With these two changes, your apparatus will be ready for research!
See “Appendix A” of https://www.mdpi.com/2673-7264/3/4/40 for a description and calculations for a table-top open-intake wind tunnel.
The flow might be straight, but its not laminar. His duct seems to be about 200mm on a side, so his critical velocity is about 0.17 m/s. Even if the duct is a bit smaller than that, he’s still several times above the critical velocity for laminar flow. James idea about drinking straws would likely get you there, if you willing to deal with the tedium of gluing a thousand straws together (not exaggerating).
aw jeeze it’s like you’re saying someone should read the wikipedia article on reynolds number before designing a wind tunnel. i hear ya :)
So… 3d printed a box instead of using cardboard and straws.
Quite the hack.
Totally worthy of a HaD article.
Though, like almost every HaD article involving 3d printing, it should be framed as an admonishment not an accolade.
I wish I understood it a bit more, this gentleman did a great job and is making the most of his abilities. Good job.