SolidWorks allows a flange to be placed on a curve.  This operation used to be done routinely in sheet  metal shops with bead-rolling equipment.  Nowadays, with so much fabrication and forming processes being automated, the bead-rolling machine is used much less or not at all.  Quick turn shops may not even have this equipement.  Instead of a continuous edge, most automated shops will fabricate a segmented edge on a curve using an Amada or similar automated punch press.  I have found that I can create this type of flange by circumscribing a polygon to the convex side of a circular arc.  Once the arc is replaced with the appropriate number of equal-length segments, a linear edge flange can be created on each segment.  However, I find that there is no way to put relief between these segments.  I suspect that this might be a feature that needs addressing since so much of sheet-metal fab process is today using automated methods.  What do you think?