Spatial resolution issues in rough wall turbulence

Abstract The question whether spatial resolution effects should be accounted for when performing hot-wire (or particle image velocimetry) measurements in turbulent wall-bounded flows over rough surfaces the fully regime is addressed and answered by exploiting an existing direct numerical simulation database of open-channel at $$Re_\tau =500$$ R e τ = 500 a surface consisting randomly distributed roughness elements. results show sizeable attenuation streamwise velocity fluctuation intensity, similar to smooth-wall with up 70% wire width around 100 viscous units. A suitable correction scheme applied successfully compensate effects. Both indicate that are relevant also can corrected posteriori state-of-the-art criteria on sensor size cannot achieved experiments. Graphical