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  1. vortexman

    DIY golfball dimples?

    Hi AlpineAce, You can probably get away with a simpler process than producing a large number of discrete dimples, especially if you know the predominant flow direction. You could introduce some raised ridges, roughly perpendicular to the airflow. The benefit of dimples is due to the fact that...
  2. vortexman

    A "new" theory of lift ?

    Dan320, I'm not positive that I understand what you mean, but I'll offer the following comments: 1) The Bernoulli Equation "works", in the sense the it always gives the right answer, when used correctly. There is nothing about causality in the Bernoulli Equation or in its application. 2)...
  3. vortexman

    A "new" theory of lift ?

    aeroafrix2, The original post sought an aerodynamicist's opinion about the "new theory" that lift is independent of circulation. That issue, and the related issues that arose in the discussion are very straightforward to deal with the use of very well-established aerodynamic theory. By...
  4. vortexman

    A "new" theory of lift ?

    rb1957, Circulation is a real physical phenomenon. The only context in which you could view it as a "mathematical artifice" is the use of the potential flow approximation to predict real flows. In this situation, one is required to specify the circulation, because the potential equations have...
  5. vortexman

    A "new" theory of lift ?

    aeroafrix2, I don't think I can explain these things to your satisfaction, especially in this limited forum. I can only recommend reading some standard Aerodynamics texts. All this stuff is there, and is standard theory that is widely understood and commonly used in practice. To say "I am...
  6. vortexman

    A "new" theory of lift ?

    IRstuff, I'm kind of running out of ways to explain it. As I said before, the physical basis of one 'theory' is also the physical basis of the other 'theory'. You don't get to pick which phenomenon you think is really happening; they both are. There is downward deflection of the airflow, and...
  7. vortexman

    A "new" theory of lift ?

    IRstuff, Start by considering all the different shaped bodies that could be placed in a uniform flow. Would you expect all of them to result in a flow field with zero circulation? If so, why? This is just as valid as to ask for the physical mechanism that results in non-zero circulation. It...
  8. vortexman

    A "new" theory of lift ?

    IRstuff, Actually, the air on the bottom of the wing moving slower than the air on the top DOES mean that there is circulation. Circulation is a well-defined quantity, and the situation you describe, slower flow on the bottom of the wing, is exactly what will cause that quantity to become...
  9. vortexman

    A "new" theory of lift ?

    KENAT, I'm not quite sure how you see the quarter chord point being involved, but the bound vortex is exactly what the circulation around the wing is. Again reaching back to Fluid Mechanics 101, the Helmholtz theory says that a vortex can't end in 3D space, so it has to be a ring vortex. When...
  10. vortexman

    A "new" theory of lift ?

    aerofrix2: I'm referring to the same Johnson referenced in the original post. I already commented that the spanwise lift distribution of a tapered wing is not necessarily constant. Beyond that, I didn't see any discussion on his pages about the lift distribution. After discovering that he...
  11. vortexman

    A "new" theory of lift ?

    Hi aeroafrix2, I'm not sure I understand what you mean by "constant lift of planforms with tapered ends", but I assume you mean a constant spanwise distribution of lift. Tapered wings don't necessarily have constant spanwise lift distributions, and I don't think anything I said has a bearing...
  12. vortexman

    A "new" theory of lift ?

    Hi rb1957, I haven't read all of his text word for word, but I did look at the color plots of velocity, pressure, and streamwise vorticity, and read the paragraph immediately after. I think this partially explains Professor Johnson's confusion. There are three components of vorticity, just as...
  13. vortexman

    A "new" theory of lift ?

    Professor Johnson's 'theory' is unmitigated nonsense. There is nothing new there, and you might as well spend your time explaining to someone that evolution doesn't violate the second law of thermodynamics. Circulation is a physical reality, in the sense that a wing generation non-zero lift...
  14. vortexman

    Air Baffel design needed to achive laminar flow

    The first question is whether you really need laminar flow, or just plug flow. If you only need plug flow, in the sense that there aren't significant recirculations that could, for example, carry contaminants back upstream, you probably already have that coming out of your filter, as long as...
  15. vortexman

    Is Propeller Spiraling Slipstream a myth or provable fact?

    Majortomski, The helical slipstream doesn't have much effect in the roll axis. The main reason for this is the one pointed out by btrueblood: The engine exerts torque on the air passing through the prop, and then the swirling air partially cancels that torque out by exerting some of it back on...
  16. vortexman

    Is Propeller Spiraling Slipstream a myth or provable fact?

    Majortomski, Why do you think there is no spiraling slipstream? Does it just seem incredible to you, have you done some measurements, did someone knowledgeable make this assertion to you? In your original post, you mentioned a NACA paper that talked about a 3 degree angle of attack on the fin...
  17. vortexman

    Is Propeller Spiraling Slipstream a myth or provable fact?

    thruthefence, Yes, without an asymmetric fin, or any fin, there would be no such effect. vortexman
  18. vortexman

    Is Propeller Spiraling Slipstream a myth or provable fact?

    Dan320, I'm not sure what you want me to explain, so I'll try to clarify both points. First, the P-factor is a phenomenon completely unrelated to gyroscopic precession. P-factor is simply a thrust differential resulting from the propeller operating at a non-zero angle (usually in pitch) to...
  19. vortexman

    Is Propeller Spiraling Slipstream a myth or provable fact?

    Majortomski, You are mistaken about how precession works. Rotation in one axis results in torque about a separate axis. Torque in one axis does not result in rotation in a separate axis. In any case, this phenomenon would not be relevant to your original question. vortexman
  20. vortexman

    Is Propeller Spiraling Slipstream a myth or provable fact?

    The P-factor has nothing to do with precession. It is the differential thrust caused by differential angle attack of the propeller blades as a result of a non-zero pitch angle. vortexman

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