riblets

A riblet is an alternative to ribs. The actual riblet is the portion of a loin back rib (or baby back rib) that is cut off at the top (nearest the back bone) to give the rib a more uniform look.

Riblets
On the effect of riblets in fully developed laminar channel flows
Turbulent Boundary Layer Drag Reduction Using Riblets
Turbulent boundary layer drag reduction using riblets
Optimization and application of riblets for turbulent drag reduction
Direct numerical simulation of turbulent flow over riblets
Experiments with three-dimensional riblets as an idealized model of shark skin
Near-wall structure of a turbulent boundary layer with riblets
Optimization and application of riblets for turbulent drag reduction - 22nd Aerospace Sciences Meeting (AIAA)
Choi, K.-S.: Near-wall structure of a turbulent boundary layer with riblets. J. Fluid Mech. 208, 417-458