Our new Sawtooth dimple design consists of 12 nodes that are precisely clocked to start aerodynamic shearing at a rate of 50Hz at a rider speed of 20mph,” says Zipp’s marketing collateral. “Sawtooth accomplishes this by inducing small sheet vortices that shed at a low magnitude, but at a higher natural frequency, thus decreasing the laminar bubble effect on the aerodynamically shielded side of the rim’s profile to further reduce high yaw drag and improve crosswind stability.”
Bit different from usual, but applicable I think:
http://cyclingtips.com/2016/10/zipp-404-nsw-carbon-clincher-wheelset-review/