Scaling of turbulent structures in riblet channels up to Reτ ≈ 550

Results of direct numerical simulations of riblet channels at Re-tau approximate to 550 are presented and compared with previous results at Re-tau approximate to 180. Special attention is given to the scaling of the turbulence phenomena associated to the presence of riblets in the wall, particularly to the length scales and intensities of the coherent spanwise rollers whose appearance has been recently reported. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757669]