0
$\begingroup$

There was a similar question posted on this topic previously where it was agreed that the deflection of a rotating blade was decreased once the blade began rotating due to the centrifugal force. But I don't see why centripetal force can't also counteract blade deflection.

If we have a blade that is attached to the centre of rotation at a joint/hinge then when stationary the blade will naturally deflect downwards due to the mass of the blade. For simplicity I assumed that the load due to the mass of the blade is acting downwards at the very end of the blade. Due to this deflection there is some tension in the blade. The vertical component of the tension would be equal to the weight of the blade while the horizontal component of the tension would be the centripetal force. Now, as the angular velocity of the blade increases the centripetal force (Horizontal Component) will also increase in magnitude however the vertical component of the tension will remain constant. As a result, the angle at which the tension is acting act relative to the horizontal will decrease. Since the tension is supplied through the blades the angle of the blades relative to the horizontal must also decrease and hence the deflection must also decrease.

$\endgroup$
0

1 Answer 1

1
$\begingroup$

Sure, you can always convert between centrifugal force in a rotating frame of reference and centripetal force in a non-rotating frame. You just have to consider all the acceleration effects. Not sure I followed your explanation but it seems to be missing the tension due to the inward acceleration.

Here's how I would think of it: there's a drooping helicopter blade, which is being accelerated straight inward (toward the pivot point) by the centripetal force. Consider two finite elements that are next to each other on the blade. There's tension between them, such that the inner finite element is pulling the outer finite element inward. But because of the droop, it actually is pulling it both inward and upward. Thus, as the centripetal acceleration increases, the droop will tend to straighten out. Just like a bent rope will tend to straighten if you rapidly pull one end toward you.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.