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Recent content by MadProf

  1. MadProf

    Why do flags flutter?

    I overlooked one other thing to mention where the vortex street is concerned. There is a flow condition of the Turbulent Laminar kind where the vortices do not alternate, but occur in pairs downstream from the mast. The RE number applicable is higher than that of a purely Laminar flow, but lower...
  2. MadProf

    Why do flags flutter?

    If I can take us back to the vortex street phenomenon one more time, there is something to remark concerning the alternating nature of the vortices that would shed from a mast at an RE of about 500. Assuming dead-steady wind of a velocity that would create the particular flow condition called...
  3. MadProf

    Why do flags flutter?

    Oh, and apologies to all for throwing in a change-of-subject and non-related question. Greg's pointing out 731-376 is noted. It wasn't intended to corrupt the thread, but purely in response to the Nobel Prize reference. Whether I'll put the question to the forum in a different category remains...
  4. MadProf

    Why do flags flutter?

    Yes, in the real system where there are so many variables and different mechanisms operating, the influence of gravity as Greg indicates cannot be ignored and neither can the vortex street per RB1957 & Saskimoto be dismissed. And streaming the flag in the horizontal plane should produce...
  5. MadProf

    Why do flags flutter?

    Thanks PJA! Good observation!
  6. MadProf

    Why do flags flutter?

    Oh, just one other thing regarding vortices shed by a mast. Yes, they'll determine periodicity of the dominant flutterings in the flag, but conditional upon the Reynolds Number (flow condition) operating about the mast. The biggest amplitudes are produced at relatively low RE numbers in the...
  7. MadProf

    Why do flags flutter?

    Hi Saskimoto, The natures of turbulences are underpinned by causes. Turbulences cause the flag to flutter, obviously enough. Ipso facto, whatever causes turbulence also causes the flag to flutter. Merely a different depth of analysis applied to the phenomenon. Prandtl's and Glauert's work should...
  8. MadProf

    Why do flags flutter?

    Hi Greg, Saskimoto, Nobog, Rb1957; Some responses to offer: 1. Greg is correct. There are many mechanisms and they operate on a variety of scales. 2. Saskimoto's vortex street operates on a macro scale, but I hold it to be a bit superficial. It's a mechanism that can cause the flag to flutter...
  9. MadProf

    Why do flags flutter?

    PJA, A worthy comment. The factors you mention bring the obvious considerations of fluid density, viscosity and the rigidity and elasticity of material the body - in these cases, the flag and wing. Bringing consideration of a wing into the discussion throws up more dynamical variables, however...
  10. MadProf

    Calculation of wind drag on Race car

    Greets Gentlemen! rb1957 and sreid are partly correct and partly incorrect on one little detail. cD is indeed a fixed constant in its pure form for a given craft or vehicle, but the change in drag is not influenced by changes in air density alone. Moreover, there is an influence that does...
  11. MadProf

    Why do flags flutter?

    Yes, Sailoday & IRstuff, an interesting point. Invariably, whether flying or hanging, the force of gravity is operating. However, my case claims that the flag will flutter even in the absence of gravity, were such a thing to be possible. This was made clear enough already. Therefore, a more...
  12. MadProf

    Why do flags flutter?

    Gentlemen: 1. With or without the flag pole, the metal sheet would oscillate and the fabric flag would flutter. That is a certainty. 2. Vortices MUST have a cause which relates directly to the presence of the flag in the airflow - forget sheeding vortices off the pole, because although it would...
  13. MadProf

    Aerobatic Airfoils Design Considerations?

    Hi Cludwig and Fellows, My idea may not be a definitive solution to the problem as it throws up several other challenges to be met. However, if one were to start with a biplane configuration having both wings symmetrical, probably laminar flow and neither wing set forward of the other, consider...
  14. MadProf

    Why do flags flutter?

    Hi Nobog & fellows, This question lies close to an area of expertise in which I aspire to become a specialist in future and in which I have a theory regarding the nature and cause of Tolmien-Schlichting waves. First, whilst eddy currents around the flagpole prior to sweeping over the flag's...
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