@article{oai:oist.repo.nii.ac.jp:00001046,
 author = {Barros, Julio M. and Christensen, Kenneth T.},
 issue = {2},
 journal = {Journal of Turbulence},
 month = {Mar},
 note = {The structural attributes of turbulent flow over a complex roughness topography are explored using high-frame-rate stereo particle-image velocimetry measurements in the wall-normal–spanwise plane. The roughness under consideration was replicated from a turbine blade damaged by deposition of foreign materials and contains a broad range of topographical scales arranged in a highly irregular manner. Previous results from Barros and Christensen [Observations of turbulent secondary flows in a rough-wall boundary layer. J Fluid Mech. 2014;748] revealed strong spanwise heterogeneity in the flow attributed to the formation of roughness-induced turbulent secondary flows identified by spanwise-alternating low- and high-momentum flow pathways (HMP & LMP, respectively) in the mean flow marked by enhanced Reynolds stresses and turbulent kinetic energy. Frequency spectra of streamwise velocity at fixed wall-normal location presented herein also display strong dependence on spanwise position. In particular, the roughness promotes enhanced energy content of the large-scale and smaller-scale motions (as opposed to very-large-scale ones). Depending on spanwise position, pre-multiplied spectra highlight significant modification of the energy content of the very large-scale motions (superstructures) due to roughness compared to smooth-wall flow. Of note, a shift in both TKE and RSS content to shorter streamwise scales at an LMP was noted, while less of an impact was found coincident with an HMP.},
 pages = {147--173},
 title = {Characteristics of large-scale and superstructure motions in a turbulent boundary layer overlying complex roughness},
 volume = {20},
 year = {2019}
}