Spatial resolution effects on measurements in a rough wall turbulent boundary layer

Abstract

Hot-wire probe resolution effects on the measurements of the streamwise velocity fluctuation are assessed in a two-dimensional fully rough wall turbulent boundary layer (TBL). Various viscous-scaled wire lengths $$l^+$$\n ranging from 24 to 168 are used. It is found that, in contrast to results observed in smooth wall TBLs measurements, there is no effect of the wire length on the measurements. Accordingly, no corrections similar to those required for smooth wall TBLs are necessary for fully rough TBLs. In fact, the application of such corrections to fully rough wall TBL measurements can lead to erroneous near-wall behaviour of the variance of the longitudinal velocity component.