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As seen in this picture, the tip vortices are said to make downwash. Why is that?

I’m also not sure why that’d tilt the lift vector backwards, but that might require a separate question.

Link to the article the picture is from. enter image description here

Wyatt
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1 Answers1

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Your understanding is sophisticated enough that you shouldn't be trying to learn more from websites and other resources intended for pilots and laypersons. These resources do not apply sufficient rigor -- because rigor is not needed for that audience.

Instead, you should be learning from textbooks intended for engineers.

As you know, a wing can be represented by a horseshoe vortex system with a bound vortex at the quarter-chord line and two trailing vortices from the wingtips. These all have the same vorticity and can not exist without one another. Both the bound and trailing vortices contribute to downwash, but I think it is easiest to see how the bound vortex contributes.

I also personally do not like the description of induced drag tipping the lift vector backward -- lift is always perpendicular to the freestream. The total resultant aerodynamic force might be tipped backward, but not the lift vector.

Rob McDonald
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  • I see. So the bound vortex is from the boundary layer, I think, and how would that contribute to downwash? I was going off of what this answer said. – Wyatt Mar 18 '24 at 17:31
  • @Wyatt: The bound vortex has nothing to do with viscosity and boundary layers. It is part of potential flow theory. – Peter Kämpf Mar 18 '24 at 18:15
  • @PeterKämpf oh right, I completely forgot about that haha – Wyatt Mar 18 '24 at 18:21
  • Also, I found this video. Do you think it's accurate? – Wyatt Mar 18 '24 at 19:46
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    @Wyatt Despite appearances, I don't have infinite time to spend here. In particular, I don't have time to watch arbitrary videos and score them for you. Videos like this one are likely mostly good. They probably get 95 or 99% of things correct. However, you tend to ask questions that poke at the last 1% or 0.1% of a subject. This is good -- as it demonstrates that you're really coming to an understanding. However, you can't expect a resource aimed at people who only care about the first 80% to meet your needs. – Rob McDonald Mar 18 '24 at 21:22
  • @Wyatt furthermore, the level of understanding that you're seeking is not something that can be achieved through intuition and hand-waving. To achieve the rigor and subtleness that some of these questions require, you have no choice but to dig into the math and derivations -- something these kinds of resources staunchly avoid. You're pushing beyond the level that the tools you're using are meant for -- you will be constantly frustrated. You need to upgrade to the next level of tools. – Rob McDonald Mar 18 '24 at 21:25
  • @Wyatt -- Are you still in school? If so, what level are you at and how far do you plan on going in your organized education? If you are done with organized education, how far did you get in organized school and what are your goals?

    What country are you in? If you are not at a university, are you in a city or region that has a technical university? (I'm asking to judge the availability of technical libraries etc.)

     – Rob McDonald Mar 18 '24 at 21:29
  • @RobMcDonald I definitely understand not having infinite time. Any help and time that you give me is greatly appreciated. I'm 15, and because of that I haven't gone to any secondary school or anything yet. I really just want to learn as much as I can about this subject, as it's what I'm interested in. I am in the US (Virginia) , and there are some university's in my area. – Wyatt Mar 18 '24 at 22:04
  • Also if you would like, we can continue this discussion in chat. – Wyatt Mar 18 '24 at 22:11