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Old   December 24, 2010, 02:03
Default three linked swimmer simulation
s Kumar
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I am trying to do a swimming creature with three links and two joints.
I have created three 'boxes' and tried to give coupled motion in GMO model.

It swims in highly viscous fluid by flapping wings.

I have problem in giving flapping motion to the wings.

It is coupled motion. But how to give flapping effect ( beating and reversing of wings)?

Please some one help me.
Thanks in advance

Last edited by doctsh; December 24, 2010 at 03:23.
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Old   December 27, 2010, 18:23
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Jeff Burnham
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I haven't tried to do this myself, but here's one approach that may work for you (at least it seems so in theory). Note that the options described below are as they are presented in v9.4.2.

(1) define three components, all of them 'coupled-motion' GMO w/ 6 degrees of freedom (requires GMO physics package to be activated).

(2) connect the 'wings' to the 'body' using either (a) one 'compression and extension spring' and one 'torsion spring' for each wing, or (b) two 'compression and extension' springs (one at the top and one at the bottom of the wing). Search the User Manual for 'springs' to find the description of the parameters: you'll want to set the end points, spring coefficient, free length, and block length such that the connection acts as a hinge of fixed length. I think option (b) would be easier.

(3) for the two 'wings', add 'control forces/torques', using the 'define multiple forces and application points' option. Make sure that the control forces are in the 'body system', and the 'initial application point' (which will then move with the wing) is correct. Use 'tabular' data to get the sinusoidal motion you're looking for.

I'd run the simulation in a simplified fashion first, to check the motion seems reasonable, before turning the thing loose in a complex flow field. Good luck, and no promises to whether this will work! If it does, please let me know.
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