Bending MicroChannels

Hello,

I want to simulate a bending microchannel. In the simulation i want to do a parametric swwep of the bending angle in the range(10,5,180).

when creating the geometry of the channel, i used parametric curves for the bending radius. The thing is i want the length of the channel to remain constant when sweeping between angles. So far i created a channel and everything went fine, except for example when the angle is 80, the length of the channel would be different from when the angle is 90 etc. How can i proceeed ?

Thanks for any help.