When tightly curved sections of an imported CAD model are not meshed adequately, you can modify the mesh in these areas by re-importing the model with a defined chord angle.
The chord angle defines how closely the curve is approximated with straight sections. The smaller the angle, the shorter the resulting chord length, and the finer the mesh. If the chord length is greater than the general edge length of the mesh, the general edge length will be used.
Using the chord angle will increase the number of elements in the mesh significantly.