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  1. badoumba

    Gliding object - Wind tunnel procedure?

    Thanks for sharing the doc. As L/D varies both with AoA and speed, I am using at the moment a dichotomic approach to first determine the AoA with a guessed speed, and then refine it by playing around with different speeds. The final values give me the L/D, so the gliding angle. The speed is...
  2. badoumba

    Gliding object - Wind tunnel procedure?

    I guess the answer is simply in this Lift equation: https://www.grc.nasa.gov/WWW/K-12/airplane/lifteq.html Extracting V. But it doesn't take in account the wingload (ballast addition which increases forward speed).
  3. badoumba

    Gliding object - Wind tunnel procedure?

    Hi guys, Back on my investigations after a short break. Here is what I managed to have so far: Using DOE (design of experiments) features of some cloud computing services, I measured the L/D ratio for a complete matrix of speed and AoA. Among all the measures, there is a specific speed (V0)...
  4. badoumba

    Wind tunnel cost

    Thank you guys, @tbuelna thanks for your details. Prices are on these website actually along with all the practical details.
  5. badoumba

    Wind tunnel cost

    Hi everyone, Does anyone can give me an idea of the prices of a wind tunnel session for testing a car aerodynamics? I guess there might be a range of prices depending on the wind tunnel size and capabilities. Thanks!
  6. badoumba

    Gliding object - Wind tunnel procedure?

    Thanks @Lnewqban The most simple but comprehensive presentation I found is this one : http://www.rjplancaster.net/documents/PrinciplesOfGliderFlight-LiftDragPerformance.pdf But as we can deduce from slides 12, 13 and 34, we have to much variables for solving the equation. Lift is proportional...
  7. badoumba

    Gliding object - Wind tunnel procedure?

    Hi rb, In this page http://www.free-online-private-pilot-ground-school.com/Aerodynamics_in_flight.html, if you look at the paragraph between fig 5 and 6, it says "Note that the maximum lift/drag ratio, (L/D max) occurs at one specific angle of attack and lift coefficient. If the airplane is...
  8. badoumba

    Gliding object - Wind tunnel procedure?

    Maybe a drawing is more clear :) - From an initial speed (how to choose?), I can determine the Cl and Cd for a range of attack angles - From these 2 graphs I can draw the Cl/Cd over attack angle and determine the angle which would represent the best L/D ratio - With this angle in...
  9. badoumba

    Gliding object - Wind tunnel procedure?

    I don't know this book you are referring to - but ordered, thanks. I however read many extensive pdf files here and there describing the physics of the glider flight. Not a mathematician but I guess I understand most of it. However I am still not able to build a CFD procedure. I make myself...
  10. badoumba

    Gliding object - Wind tunnel procedure?

    Hi experts! I am trying to qualify the flight performances of a non-powered aircraft in CFD. I have no idea about how it is done in a real wind tunnel, but to calculate the Cl and Cd coefficients of the aircraft, I had to provide an incidence angle (which I assume to be 0° without any thrust)...
  11. badoumba

    AC location

    The AC is for the bird. Actually CFD software needs the precise location of the AC to compute lift and drag coefficients. I was concerned about choosing the CG by default. Is the bird tail different from the plane's stabs? I would be interested in reading some related articles if you have - I...
  12. badoumba

    AC location

    Mhmmm... inline OK, but not collocated. Flight is straight and stable in our simulation, yes. Section 3.2 here (http://www.aerostudents.com/files/flightDynamics/theAerodynamicCenter.pdf) as in other documents I read report that the more the AC is aft in respect to the CG, the more stable is the...
  13. badoumba

    AC location

    Dear rb, The shape is indeed not fixed, but it is for the 3D model I am studying. We know where is the CG and at which speed/altitude he is flying. According to you, this should be enough to tell me where the AC is located? I would need more explanation if you don't mind. BTW, is my practical...
  14. badoumba

    AC location

    Hi experts, I am a CFD consultant and I have a customer who studies birds flights. For one of the 3D model we have (a very specific and unusual flight configuration of the bird), we know where is the center of mass. But we are now looking for a way to determine the torque in the 3 axis...
  15. badoumba

    Clamped-free bar frequencies

    Thanks Tomirvine and Hacksaw for your tips and documents. I have everything I need to continue now!
  16. badoumba

    Clamped-free bar frequencies

    -Hi I found the attached formula on the book "The science and application of acoustics" of R.Raichel (isbn 038798907-2) unfortunately not avaliable any longer. Thus I don't know which are the terms of that equations that seems to illustrate the non natural frequency scale of a clamped-free bar...

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