 # Discussion Forum

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

## Circular rotation

Hi

I am a new user of COMSOl and have a very basic simple model to simulate, I have imported a spring coil from Autocad and want to apply a circular force in order to rotate it, Can anyone help me with this circular force problem because i am able to apply force in any one direction by defining force in x,y,z direction but i need to define it in circular path but not in a circular path

5 Replies Last Post Oct 29, 2010, 8:59 AM EDT

there is no thing as a circular force. If you want to apply a torque M you must find how to define the Force vector F according to the vector equation M = F x r. M, F, r are all vectors.

Regards
Edgar

Thanx Edgar,

But can you please elaborate your answer. lets say i have a circular plate of radius r and height h and i want to apply twist of an angle Theta, what should i do ?

you would probably set one face of your disc to the boundary condition fixed and calculate the displacements of the other face according to the twist angle Theta.
Say the axis of your disc points in z direction, then your displacements are:
Rz = 0
Rx and Ry are to be calculated as functions of x, y and Theta for the other face of the disc. You can enter such expressions into the Constraint fields in the prescribed displacement boundary condition.

An example: along the x-axis you have:
Rx = x . sin(Theta)
Ry = x . (1 - cos(Theta))

Now generalize these expressions for the x-y-plane and you are done.

Regards
Edgar

Hi

as a good example take the moment load in the 3.5a structural application mode documentation

--
Good luck
Ivar