Premium
Observations of the space‐time structure of flow, turbulence, and stress over orbital‐scale ripples
Author(s) -
Hare Jenna,
Hay Alex E.,
Zedel Len,
Cheel Richard
Publication year - 2014
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2013jc009370
Subject(s) - turbulence , physics , mechanics , vorticity , amplitude , oscillation (cell signaling) , turbulence kinetic energy , reynolds stress , vortex , classical mechanics , optics , biology , genetics
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.