Effect of variable winds on current structure and Reynolds stresses in a tidal flow: analysis of experimental data in the eastern English Channel

Abstract

Abstract. Wind and wave effects on tidal current structure and turbulence throughout the water column are examined using an upward-looking acoustic Doppler current profiler (ADCP). The instrument has been deployed on the seafloor of 18-m mean depth, off the north-eastern French coast in the eastern English Channel, over 12 tidal cycles, and covered the period of the transition from mean spring to neap tide, and forcing regimes varied from calm to moderate storm conditions. During storms, we observed gusty winds with magnitudes reaching 15 m s −1 and wave heights reaching up to 1.3 m. Analysis of velocity spectra revealed a noticeable contribution of wind-induced waves to spectral structure of velocity fluctuations within the subsurface layer. Near the surface, stormy winds and waves produced a significant intensification of velocity fluctuations, particularly when the sustained wind blew against the ebb tide flow. As during wavy periods, the variance-derived Reynolds stress estimates might include a wave-induced contamination, we applied the Variance Fit method to obtain unbiased stresses and other turbulent quantities. Over calm periods, the turbulent quantities usually decreased with height above the seabed. The stresses were found to vary regularly with the predominantly semidiurnal tidal flow. The along-shore stress being generally greater during the flood flow (∼ 2.7 Pa) than during the ebb flow (∼ −0.6 Pa). The turbulent kinetic energy production rate, P , and eddy viscosity, A z , followed a nearly regular cycle with close to a quarter-diurnal period. As for the stresses, near the seabed, we found the maximum values of estimated quantities of P and A z to be 0.1 Wm −3 and 0.5 m 2 s −1 , respectively, during the flood flow. Over the storm periods, we found the highest unbiased stress values (∼ −2.6 Pa) during ebb when tidal currents were opposite to the southwesterly winds while, during the flood, the surface stresses slightly exceeded those estimated for a calm period. A comparison of obtained results gives a good agreement with those of other researchers working on direct measurements of turbulence in tidal flows.

Potencialidade Do Uso De Método Matemático Para Previsão De Maré Astronômica No Porto Da Cidade De Belém-Pa

“…Entretanto no intervalo de 420 a 510 minutos os resultados ficaram bastante diferentes das medições. Esta diferença é atribuída a alguns fatores que influenciaram nas medidas experimentais como: pressão atmosférica (CARVALHO & AMORIM, 2014), vento (KOROTENKO et al, 2012), hidrodinâmica do porto e a proximidade da régua linimétrica com a descarga do canal de água residuária dos bairros de Belém.…”

Effects of bottom topography on dynamics of river discharges in tidal regions: case study of twin plumes in Taiwan Strait

“…Rippeth et al, 2003;Souza and Howarth, 2005;Wiles et al, 2006;Korotenko et al, 2012Korotenko et al, , 2013. The simulated time series of the vertical structure of TKE for Sites 1 and 2 are depicted in Fig.…”

“…Rippeth et al, 2002Rippeth et al, , 2003Korotenko et al, 2012Korotenko et al, , 2013. As the tidal current flows across the shoal of small depth, the current velocity increases due to the conservation of mass.…”

Simultaneous measurements of tidal straining and advection at two parallel transects far downstream in the Rhine ROFI

“…Therefore, this approach can be used qualitatively on in situ data to investigate the competing processes responsible for changing the stratification. Korotenko (2012) and Korotenko et al (2014) show that vertical mixing due to tide, wind, waves and bottom topography is important for the vertical density structure. They show that bottom topography (a 5 m deep plateau) can play an important role for producing turbulence.…”