Velocities, turbulence, and skin friction in a deep‐sea logarithmic layer

Speed, turbulence, skin friction, and drag measurements made with metal‐clad hot wires, epoxy‐coated hot films, and Savonius rotors are reported for a deep‐sea boundary layer at a water depth of ∼5000 m. They include data from heights z < 30 cm, a region hitherto only investigated in detail by Chriss and Caldwell (1982) for a shelf site. A mean speed logarithmic layer was observed at 3 < z < 200 cm. The difference between the friction velocity u *log determined from the speed profiles and the skin friction u *skin measured by flush‐mounted hot films was statistically significant at the 95% level in five out of eight analyzed burst intervals. This result suggests form‐drag influence on the vertical mean flow profile. Although identified from the mean speed data as a hydrodynamically rough boundary layer, the turbulence and bottom stress intensities at the deep‐sea site were found to be reduced by more than 40% compared to smooth‐wall open‐channel flow and planetary boundary layers. Applicability of the universal law of the wall has not been confirmed for this deep‐sea boundary layer.