Observations of the Space-time Structure of Flow and Stress over Orbital-scale Ripples
Title | Observations of the Space-time Structure of Flow and Stress over Orbital-scale Ripples |
Publication Type | Journal Article |
Year | 2014 |
Authors | Hare, J, Hay, AE, Zedel, L, Cheel, R |
Journal | J. Geophys. Res. |
Volume | 119(3) |
Pages | 1876-1898 |
Date Published | March 3 |
The spatial and temporal structure of flow, turbulence, and stress over equilibrium orbital-scale sand ripples are investigated at turbulence-resolving scales with a wide-band coherent Doppler profiler (MFDop) and an oscillating tray apparatus. The oscillation period and horizontal excursion were 10 s and 0.5 m. A single trial was also executed at 0.6 m excursion. Ripple wavelength and amplitude were 25 and 2.2 cm. Ensemble-averaged velocity profiles were acquired with 3 mm vertical resolution at 42 Hz. The spatial pattern of flow as a function of oscillation phase was determined by combining the phase-averaged velocity measurements from trials with the MFDop at different positions relative to a particular ripple crest. The MFDop measurements are used to investigate the coevolution of the lee vortex, turbulent kinetic energy, Reynolds stress, and turbulence production as a function of phase. Shear stress is determined from the vertically integrated vorticity equation and the double-averaged momentum equations. Friction factors obtained from the two methods are comparable and range from 0.1 to 0.2. | |
DOI | 10.1002/2013JC009370 |