A feedwell for a thickener/clarifier includes a feedwell body (40), a feedwell inlet (41), a sidewall (42), and a discharge opening (48). At least one infeed conduit (21) is connected at an upstream end of the feedwell inlet (41). The sidewall (42) has a non-cylindrical curved peripheral surface defining a radially-outermost fluid boundary surface for an influent stream (60). The non-cylindrical curved peripheral surface may include portions of a volute surface, coil surface, helical surface, compound curve surface, spline curve surface, or spiral surface. Feedwells according to the invention provide a uniform settling tank feeding flux around exiting portions of the feedwell, control velocity gradients and shear rates, protect flocculated aggregates, normalize sedimentation conditions in the settling tank, and prevent large local accelerations and flow non-uniformities.