Mean flow

Spatial variation of mean flow near the wall.

• Flows follow the meandering path in the interstices.
• The lowest U occurs above the forward crestline, maximum U occurs above the center of side ridges.
• Maximum W occurs above the center of forward face.

Turbulence Statistics

Spatial variation of Reynolds stresses.

• Substantial spatial variation of Reynolds stresses occurs within 2k.
• <u’u’> shows the shooting-up pattern across the entire roughness wavelength.
• The shooting-up pattern for -<u’v’> and <v’v’> is localized at the forward face of the roughness.

TKE production

• Maximal production occurs above the forward face of pyramid.
• The spatial variation is dictated by the

TKE budget terms

• Dissipation is 50% of the true dissipation due to limited out-of-plane resolution.
• Both production and dissipation very near the wall.
• In the outer-layer, the dissipation is higher than the production.
• Transport term is only substantial below ~ 2k.

Spatial TKE spectra

TKE energy spectra

• Growing contribution of large scale turbulence with increasing distance from the wall.
• Spectra flatten indicating excessive energy in k-3k range.
• The same trend observed in the ocean boundary layer measurements. (Hackett et al. JGR, 2010)

Compensated energy spectra

• Spectra bump appears distinct peaks in compensated spectra.
• Low wavenumber spectral peaks appear in the outer-layer.

Sample of Instantaneous realizations

Instantaneous realizations

• Large scale shear layer marked by CW vortices can be observed across the entire domain.
• Near-wall vortices appear to be lifted by the large scale structure in the outer-layer.

Conditional averaging

Instantaneous realizations

• Large scale shear layer marked by CW vortices can be observed across the entire domain.
• Near-wall vortices appear to be lifted by the large scale structure in the outer-layer.