Doing the DTU coursera wind energy certificate and this helped a lot to understand the aerodynamics module. This simulation model is amazing. Thank you!
That's great to hear, please tell your friends, and your teachers! And you can try Ashes for yourself for 2 weeks by downloading it for free form www.simis.io
Haha if there was a million 'love comment' button I'd click that one! Great that you liked it, you should download Ashes (www.simis.io) and try the velocity triangle yourself!
@@AshesWindTurbineSimulation I really appreciate your explanation, it help me alot , Do you have facebook or whatsapp , I am doing my final project of graduation, and it's about savinous wind turbine and need some point to be explained , thank you bro for everything you've done so far in your channel 😊🌹
@@ibrahimhamoud15 Wr're not experts in vertical axis, but you could try asking in our forum, and we'll see if we can answer. Here's the link: www.simis.io/q-and-a/
Very nice explanation. And interesting to see the thrust force, which comes with a lot of consequence, and unfortunately the lift force is not increasing over distance. That would really create a lot of torque. What is your idea of a variable pitching VAWT, like we demonstrate in our channel?
Sorry for late reply. We haven't looked at VAWTs at all, but are vey interested to do that in the future. Looking for the right context/project that will put VAWT loading to the top our our (very long) priority list (aka Trello boards). About thrust - I think it's fascinating that you cannot get rid of it by improving design - it's a consequence of first principles.
Hi I have a question. So according to your extremely well presented explanation, the rotational velocity of the wind is the main cause of the rotation of the blades because it is the one that induces Ftotal. (Mostly using Flift). The Ftotal causes Ftorque that rotates the blades. However, suppose the blades are not rotating at all and the wind starts to blow. How does the wind turbine even start rotating from a complete stop? Are there different forces at work during the startup?
Good question! The main contributor to the relative velocity is, as you said, the rotational velocity, but the incoming wind velocity also contributes. When the turbine is not rotating, only the incoming wind velocity will produce aerodynamic loads. These loads will be much smaller than when the turbine is in operation (i.e. rotating), but strong enough to start rotating the turbine. So the turbine will start rotating very slowly, which will produce a very small rotational velocity, which will increase the aerodynamic loads, which will make the turbine rotate a bit faster, which will increase the rotational velocity and so on. But the best way to understand this would be to use the free trial period of Ashes and try to do it yourself (you could try to do something similar to our video, with an initial rotational velocity of 0 RPM). You can get the software at www.simis.io, and please let us know if it worked!
Thanks for the comment - We are happy you found it useful. You can play around with the velocity triangle yourself during the 2 weeks evaluation of Ashes. Register and download the full version from simis.io.
thanks, excellent explanation, have you any video about flat blade turbines? since such a airfoil profile is not possible for small home made ones, but if you help we can diy better small turbines, 🙏🙏🙏
Great video! Are you able to quantify how much larger the thrust force is than the torque, are the visual lengths true? To me the difference between the two appears to be too large, given that Betz' law in an impossibly ideal turbine would limit the difference to 59.3%/(1-59.3%)-1 = 45.7% (i.e. the energy left in the wind passing the turbine could be at minimum 45.7% larger than what's converted to electricity).
The visual lengths are proportional, but we don't recommend using them for numerical values. Instead, use sensors that give you live numerical values (that can be exported) and live graphs if you want that. For example, there is a sensor field for efficiency, ie mechanical power (torque * rotational speed) divided by incoming power in the wind. For a well designed wind turbine the max value is around 50% < Betz limit of 59%. I don't think understand your reasoning about efficiency/Betz. Seems like you don't take the rotational velocity into account? To get power, that is necessary. Please, elaborate, or better yet - try ASHES with the 2 w evaluation license and look at sensors, and then elaborate. Or are you studying wind turbines at university, and already using ASHES in class?
Thank you for your video. Is it possible to have a negative pitch angle in the low wind speed region? what effect does this create on the WT performance?
Generally, for low wind speeds, the controller will make the rotor rotate at a speed that will provide the optimal tip speed ratio (the ratio of the blade tip velocity over the wind speed). This is done so that the angle of attack is the best one in terms of lift to drag ratio. So a low wind speed will generally not produce a negative angle of attack
I am wondering how the pitch plays a role in this velocity triangle. Does increasing pitch always lead to an decrease in power or are there instances where increasing pitch actually ends up increasing power. Would this not depend on the turbine regimes? Another question about the ASHES software, I was browsing through the documentation but did not find anything related to user defined wind functions, I know you can but I am not sure how. I want to model wind velocities that are different from the logarithmic wind law
Great question. The way the controller works for commercial wind turbines is that for low wind speeds (under the rated wind speed) it tries to keep the rotational speed of the rotor such that the angle between the airfoil and the total wind is optimal. So in that context, any pitching of the blades would move you away from the optimal point and thus decrease the power. But you could design and mount the blade so that it is not operating at the optimal angle of attack, and then pitch the blades when you want that to happen. About the wind speed, what type of wind are you trying to model?
@@yashdagade1240 Low-level jet winds can be generated with TurbSim, which is included in Ashes. You will have to use the Turbulent wind creator for that (see www.simis.io/docs/user-manual-turbulent-wind-creator) and select te relevant parameters
XFoil comes with the software, so you could generate different polars for your airfoils for different surface roughnesses and then compare how they perform
Glad you liked it! The rotor plane is a plane that is perpendicular to the main shaft and goes through the hub. So if the cone angle was 0, all blades would be in the rotor plane. There is an illustration of the rotor plane in our theory manual, here: www.simis.io/help/#52d585d6f04f4e8e8fc587730bc4213d
We have a benchmarking framework where we run tests and compare results with other software, full-scale data, experimental data and results from previous versions of Ashes. We add new tests on a daily or weekly basis, every time we want to test something new (for example when there is a new feature). By running the tests every night we make sure that the results are always up to date. The tests are run every night and published every new release (see www.simis.io/docs/validation-benchmarks-latest-reports for the latest reports). We think it is crucial that the tests are public and fully reproducible, so all the data needed to run the tests yourself are available as well. This video explains how to understand and reproduce the tests: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-GkoBcUybSos.html And this blog post gives more details about how the whole thing works: www.simis.io/pages/blog/
Well, not really... The concept of the velocity triangle does apply, but since Savonius wind turbines are vertical axis turbines, things would look quite different
How can you sum up absolute velocity (wind speed) and rotational velocity to get the relative velocity? Wasn't it always u+w=v? What I want to say is that "u" should be turned the other way around
Hi Jesus The rotational velocity is the apparent velocity 'felt' by the blade element as it moves through the air, so it is in the opposite direction of the motion of the element (and correctly drawn in this animation). But maybe we have different definitions of rotational velocity?
Certainly! You can change the yaw angle under Analysis parameters-> Initial conditions. I suggest you post your question on our forum (www.simis.io/q-and-a/) so we can answer more in detail.
essential questions remain unanswered: why does one accept such huge thrust-forces with relatively little torque? it is torque you want in the end... so why does one not turn the airfoil more parallel to the wind direction? that would turn its liftforce more into the right direction (ideally parallel to the rotational plane). ok, this would increase drag, but you said it's very small. so why not accept some increase in drag in exchange for more torque and less useless, even counterproductive thrust?! secondly it remains entirely unclear why the wings of a modern windmill are so long and slender and why they taper towards the end, leaving a lot of wind(-force) unused that can pass through the rotation plane without meeting a blade...? intuitively one would broaden the wing towards the outer edge and incline it at an angle of something like 45 degrees to the wind direction, so that more wind is 'caught' and more torque is generated by turning the lift force towards the rotational plane? could you please answer these questions (without maths!) just using the visual force vectors and/or ideally experiments? thanx a lot!
Those are indeed excellent questions. Unfortunately we don’t have the capacity to prioritise making new videos at the moment, but I’ll try to reply here:
About rotating the airfoil: the direction of the lift (and the drag) is defined by the direction of the relative wind: the lift is perpendicular to the relative wind, and the drag is parallel. So if you rotated the airfoil (in any direction), you would not change the direction of the lift (because the relative wind would not change (at least initially, but let’s keep that for another time)). In the conditions shown in the video, the angle between the airfoil and the incoming wind is optimised to get the best lift-over-drag ratio. If we had more drag, the torque would be reduced and we would be producing less energy. If you have the time, you should definitely try this with Ashes, it would be very obvious if you tried to reproduce the velocity triangle and pitch the blades!
About modifying the blade towards the tip: at the tip, the relative wind is almost parallel to the rotor plane (and thus perpendicular to the wind velocity), so if you pitched the blade 45 degrees you will actually drastically increase the drag, again, not what you want. And you are totally right that broadening the airfoils towards the tip would increase power production, but then you would have to reinforce the rest of the blade a lot for it to handle the deflections due to the increased aerodynamic forces and weight. There would also be an issue with the torque distribution along the blade: with the way blades are currently designed, it is more or less homogeneous, but with your suggestion you would have much larger forces at the tip, which would increase shear stresses within the blade. So even though your suggestion makes a lot of sense from an aerodynamical point of view, there are structural reasons that make it more economical to have slender blades.
@@AshesWindTurbineSimulation hello, one thing that is not clear is what put in rotation the turbine (0' 33" start the white arrow). I mean: you made an analysis of the rotational velocity and his effect on the blade shape, but how the wind velocity put in rotation the blade in order to have a rotational velocity? Because I'm not an expert, and I was doing the same objection of Hilmar. Second consideration the lift force: looking the aircraft and at their wings shapes, it looks that the lift fforce is opposite to the one you show in the video (the reason why the plane fly). do I mistake? Tanks in advance Marco
Hi Satish We have removed the floating module in the current version, but it will be available in a few weeks again. If you send us an email with your details at support@simis.io, we can keep you updated
what is happening on the windward surface of the blade? It's shape camber(?) looks as if it could also produce lift which would obviously oppose the lift generated by the other side of the blade..
Hi, I'm not sure what you mean. Which one is the windward surface? The lift comes from a pressure difference between the suction and the pressure sides of the airfoil, so there is only one lift force for a given airfoil in a given condition.
@@AshesWindTurbineSimulation The windward side is the side facing the the wind. It just seems like both sides would potentially create 'lift' given their shape . One side is obviously going to produce more lift to create the required difference, it just seems odd to me that the higher pressure side would have such a bulging shape (potentially lift positive) . I know this is a garbled statement..wish I could be standing in front of a blackboard drawing out what I mean. Thanks for your response.
@@r.roddick7585 A side does not produce lift, it's the difference of pressure between two sides that produces lift (and drag). But I think I know what you mean: intuitively we tend to think that the 'bulgng' side is the pressure side, when it is actually the opposite! The bulging side is the suction side, and that is why the aerodynamic loads are in that direction. But you would be surprised how many models of wind turbine have this wrong...
The angle of attack is noted 'alpha' in the video, in the velocity triangle window. You can see it in the Blade station sensor also. For more info, check our manual here www.simis.io/help/#12b215b5ed3c45109db85b64c854876a
Hi Yassin, that sounds great! You can start by downloading and trying Ashes for free for two weeks here www.simis.io. If you send us an email explaining your project at support@simis.io we can also see how Ashes could best fit your needs
Hi Zyad. Unfortunately we don't have the possibility to implement vertical axis turbines yet. In which context do you need to simulate one? You can also send us a mail to support@simis.io if you want to discuss about your project. Cheers, The simis team
Definitely! You'll just have to create the polars and the blades yourself, but as long as you're doing a horizontal axis turbine there shouldn't be any problem.
In what context do you need to use it for the university? If you are lecturing or giving a class you'll need an educational version. If you're a student feel free to use the 2-week triel version from www.simis.io. There isn't really a simulation that we can share, we just use the template model and use the velocity triangle feature, you should be able to reproduce it if you follow the steps in this video
Betz limit is about harnessing wind energy from the wind - you can always increase the available power in the wind through the use of diffusers, but that is different
According to Betz no wind turbine can extract more than 59.26% of the winds energy even if you design the most aerodynamic blades you will fail using the most advanced shaping possible you will fail why because Betz limit does not take into account the blade shape only the swept area of the turbine but the fact is that the wind pushes what it touches it can not push on the gaps between the blades regards Graham Flowers MEng
Interesting video, at least for viewers who know how to deal with forces represented as vectors. It is however very irritating to hear you say: "OK?" so many times, as you are not in direct contact with your viewers, so it's totally irrelevant to ask this question. It's not like we can say: "No, please explain it a litter better or slower!" If you did your job well, then you will probably get some likes. If you didn't, you'll probably find a lot of questions in the comments. Now this video is about five years old, so I hope you have learned a better way of presenting meanwhile. If not, then please consider what I just wrote.
