[MBDyn-users] Aerodynamic Elements - Modeling a Flapping Wing Microsystem

Paolo Mantegazza mantegazza at aero.polimi.it
Thu Jul 1 18:32:59 CEST 2010


Pierangelo Masarati wrote:
> David Cross (Civ, ARL/VTD) wrote:
>> MBDyn Users,
>>
>> I am trying to build a model which matches an experimental setup of a 
>> flapping wing micro-system.  The experimental model uses a 
>> polyethylene film as the wing surface, with only a leading edge spar.
>>
>> Currently I have a 2D mesh representing the wing surface using type 
>> beam2.  The problem is making the energy of this mesh equivalent to 
>> the continuum of the polyethylene film.  I am wondering if there is a 
>> better way to model a continuous surface, say through aerodynamic 
>> beams, which I have seen used in rotor blade examples.  However, I 
>> would not want these beams to model an airfoil, rather a continuous 
>> surface of a prescribed thickness and material.
>>
>> Looking at the documentation and some examples of the aerodynamic 
>> beams being used for rotor blades, I am just a little unsure of the 
>> direction to take my model.  Any suggestions would be greatly 
>> appreciated.
>>
>> Sorry for this being somewhat of a modeling question.  My MBDyn 
>> experience is limited at this point, and would benefit greatly from 
>> other users who have more experience than I.
> 
> I don't quite understand this request, taking into account your initial 
> message.  The "aerodynamic beam" implements aerodynamic forces, so it 
> has little to do with modeling the structure.  With respect to 
> aerodynamics, I infer from your previous message that you are trying to 
> couple MBDyn to an external CFD solver.
> 
> In released versions of MBDyn there is no straightforward way to model 
> shell-like elements from a structural point of view.  I understand that 
> using trusses of beams is not easy.
> 
> We have implemented a shell beam (plate + membrane), and we're 
> validating it.  As soon as we are able to address some minor issues, I 
> think it could be released shortly, say during the summer.  If you like, 
> I can send you a snapshot of the code.
> 
> Implementing a pure membrane element could be an interesting 
> development.  In principle, it would be even easier than the shell 
> element.  However, we had to prioritize the shell element.  I think for 
> some flapping wing microsystem design (insect-like, insect-size), where 
> the wing is essentially modeled using thin films it would possibly be 
> more appropriate than the shell element.
> 
> In any case, regardless of the modeling approach, a wing model that 
> allows the wing camber to change arbitrarily as a consequence of elastic 
> deformation would prevent the use of 2D aerodynamics based on table 
> lookup; for sure, it would not be feasible using 2D aerodynamic models 
> current supported by MBDyn.
> 
> Please let me know if we can be of help.
> 
> Cheers, p.

What about modeling it as a modal mbdyn elements using an external program?

paolo

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