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  1. joedunai

    Constantinesco Gearless Torque Converter

    While doing some research on power acoustics, stumbled upon a curiosity that is quite interesting. George CONSTANTINESCO who was a genius inventor in the beginning of nineteen hundreds has invented an automatic continuously variable gearless transmission, which was publicly demonstrated in one...
  2. joedunai

    Acoustic Attenuation in Thin Tubes

    Thanks for the useful tip Hacksaw, I will take a look at it. Joe
  3. joedunai

    Acoustic Attenuation in Thin Tubes

    After some more pondering of this subject of the “boundary layer not being fully developed”, I have got the point, and now understand its consequences on the viscous power dissipation of acoustic waves. IRstuff was hinting on it, but SomptingGuy expressed it more clearly. Let me summarize what...
  4. joedunai

    Acoustic Attenuation in Thin Tubes

    IRstuff, in theory there can be such thing as a slip boundary condition, which is often used in first approach simulations. This corresponds to an ideal fluid which has got zero viscosity. But in practice I am not aware of any common fluid that would not have at least a little viscosity, and...
  5. joedunai

    Acoustic Attenuation in Thin Tubes

    Thanks for the comments Greg and IRstuff. Yes, the mechanism of dissipation is not a mystery to me, as mentioned in the first post. Kinetic energy is getting converted into heat due to viscous friction of the molecules; to some degree in the bulk fluid, but especially in the narrow boundary...
  6. joedunai

    Acoustic Attenuation in Thin Tubes

    I am studying the acoustic wave attenuation in thin tubes. One of the classic papers that discuss the subject is “On the propagation of sound waves in cylindrical tubes” by H. Tijdeman. It contains all the formulas and tables needed to calculate the attenuation in thin tubes filled with air...
  7. joedunai

    Passive Intensity-Dependent Acoustic Transmission (Power Limiter)

    Greg, the device has to work only at one single frequency. It does not need to have a broadband transfer function without attenuation. It is OK to have a small attenuation at low intensities something like below 10%, while having a nonlinear increase of attenuation much greater than 10% at high...
  8. joedunai

    Passive Intensity-Dependent Acoustic Transmission (Power Limiter)

    Greg, did you mean that the SPL would be limited by the nonlinear shock wave formation that would manifest at lower SPL at lower ambient pressure?
  9. joedunai

    Passive Intensity-Dependent Acoustic Transmission (Power Limiter)

    I have just seen your second reply Greg after submitting my last post. “Another approach would be to insert a tube, sealed at each end with light diaphragms, into the duct. Extract most of the air from the sealed chamber. It will be able to transmit low amplitude signals but not high amplitude...
  10. joedunai

    Passive Intensity-Dependent Acoustic Transmission (Power Limiter)

    Good idea Greg! I have thought of that one already with a slight difference. Membranes transmit sound nonlinearly at high intensities and naturally limit the transmitted sound intensity. Take a look at Figure 2-10, Page 92 in the book “Nonlinear Acoustics” by Robert T. Beyer which can be...
  11. joedunai

    Passive Intensity-Dependent Acoustic Transmission (Power Limiter)

    Thanks Mike for the suggestion. What you are describing is actually a type of silencer that reflects/absorbs sound regardless of its intensity. Although this is not what I was looking for originally, I would be interested to see a drawing of your silencer with dimensions, if there is one. The...
  12. joedunai

    Passive Intensity-Dependent Acoustic Transmission (Power Limiter)

    I am looking for a solution that would limit the transmitted sound intensity/power in a passive way. There actually already exists such natural limiter caused by the nonlinear sound propagation at high intensities in waveguides. But the required intensity to reach that limit is very high. I...
  13. joedunai

    Robert CarrÆs Intenal Wing

    Thanks everyone for the comments. As rb1957 pointed out, the internal wing is certainly impractical as the main source of lift for an aircraft, due to dead weight of surfaces that don’t generate lift. The remark of btrueblood that “the idea isn't too nuts” is also important, because the...
  14. joedunai

    Robert CarrÆs Intenal Wing

    Robert Carr has patented his idea about internal wings in 1986 (US Patent # 4,568,042; and US Patent 4,579,300) which can be found on the page http://www.rexresearch.com/carrcoan/carrcoan.htm . The man is obviously not an expert of fluid dynamics, but his idea is still interesting. There is a...
  15. joedunai

    Joint force error - Bad 3D Contact

    Thanks GregLocock for the tip; though I am convinced the Autodesk support monitors the related important fora (it would be a mistake not to). But now with your contribution we have got the solution advice from rollupswx. Thank you rollupswx for finally revealing the trick why the Inventor was...
  16. joedunai

    Joint force error - Bad 3D Contact

    Now after a month of presenting the problem there is still no suggested solution how to get Inventor to perform this simple simulation. Therefore I will conclude that this is a bug in the software, or it is was not designed for simulations, and just ditch the idea to use it. We will have to...
  17. joedunai

    Joint force error - Bad 3D Contact

    Dear Rollupswx, Thanks for taking a look at this problem and for your advice. The parts and assembly files are now attached to this post. I have solved the same simulation in SolidWorks without any problems, but Inventor appears to be less intuitive and user friendly. Anyway, I want to...
  18. joedunai

    Joint force error - Bad 3D Contact

    Hi Experts, I am trying to run a trivially simple simulation, a ball moving within a cone. If I don't add a 3D Contact - Force Joint between the ball and cone wall then the ball will fly through the wall. If I add the Force Joint then I get the following error message: "Joint force error: No...

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