Mapped mesh and toroidal extrusion

mapped

It is all about smooth transitions that do not distort elements from rectangles too much.  This is easier if every 90 degrees is split into 3 parts of 30 degrees, both along the fillet and around the revolve. Note, the white lines were made mostly by revolved quilts made into volume regions.  Also note the the inner edges of elements do not have curvature.  As shown, the revolve is split into every 22.5 degrees (only meshed one of them).  And of course when using volume regions remember to set the default interface to bonded.