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frequency and force

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2015-09-13
2015-10-07
  • rakesh kumar

    rakesh kumar - 2015-09-13

    hi Sir,
    in the new version of Qblade(v0.09b) where i can get the ForceN vs Radius graph and how can i get the frequency value from Qblade with different modes??

     
  • David

    David - 2015-09-14

    Hello,

    to get the normal over the radius you have to set the graph to a "blade graph". The Eigenfrequencies are shown in the GLView of the QFEM module.

    Regards,

    David

     
  • Anonymous

    Anonymous - 2015-09-18

    Hi David
    First to thank for all you that giving me a helpful reply :)
    while working in Qblade i got two doubt which are as :
    1-why the given twisted blade angle is not as same as exported file ?(i hv attached the pictures ,1st two are from Qblade and the last one is from the exported data).

    2- why the forcing value is giving at the C.G. (almost) of the element but not at the end of each element ??

    Thanking you)

     
  • David

    David - 2015-09-19

    Hi,

    to answer your questions:

    1. The blade definitions between QBlade and FAST are slightly different. When exporting a QBlade blade definitions to FAST some interpolations are necessary due to these differences. FAST (AeroDyn) always defines twist angles at the center of an element, in QBlade these angles are defined at the element angles so that the twist distributions is continuous in the blade design. In the file angle.JPG you are showing a blade.dat file from FAST. These files usually have evenly distributed elements for the structural properties and thus the interplation and the different values.
    2. I am not sure what you mean here. I am guessing youre asking why the forces are calculated for an elements center? In the LLT module of QBlade the force values are calculated for the center of an element and this value is then taken for the whole area of that element and it is assumed to be constant. To use constant element wise force distributions is one of more possible approaches and was implemented due to its simplicity.

    Regards,

    David

     
  • rakesh kumar

    rakesh kumar - 2015-09-29

    hi David Sir
    I am unable to match the frequency value with the matlab coding (following as given in source code of Qblade and Sir Scoot larwood dessertion ). I got the Imaginary vlaue of frequency .
    If you wish to see my matlab code then i will mail you in your i'd .

    thank you :)

     
  • David

    David - 2015-10-01

    Hi Rakesh,

    unfortunately I am lacking the time to check your code. But setting up the correct structural model with sectional parameters and the local section coordinate systems is a quite challenging task.

    Regards

    David

     
  • rakesh kumar

    rakesh kumar - 2015-10-07

    Hi David Sir,
    Thanks for your nice reply ,Sir the formulation is given in the "Dynamic Analysis Tool Development for
    Advanced Geometry Wind Turbine Blades,Scott Larwood" dessertation ,is enough to get the frequency and mode shapes ? and i checked with the Qblade source code too i follow the same but can't able to find that why i'm not getting the same frequency what i got in Qblade .....I'll wait for your another helpfull reply .

    thank you .

     

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