Turbulence & Mixing in Shelf Seas

Menai Strait.

The Menai Strait is a narrow channel which separates the island of Anglesey from the UK mainland.

We have deployed a 1200kHz RDI ADCP in the Menai Strait for three days to investigate some of the turbulent characteristics of the tidal flow in the Strait and to examine the dynamical balance in the Strait.

The position of the ADCP is marked with a green dot on the map. Two tide gauges (TG) were also deployed to allow the surface slope to be estimated.

Using the method of Stacey et al, (1999) the Reynolds stresses were calculated from the variances of the along-beam velocities of two opposite beams by splitting them into a mean and a fluctuating component.

The rate of turbulent kinetic energy production can then be calculated directly from the Reynolds stresses and the vertical velocity shear.

Rate of Production of Turbulent Kinetic Energy.

The results show the cycle of turbulent kinetic energy production associated with the flood and ebb of the tide.

Reference.

T.P. Rippeth, E. Williams and J.H. Simpson. (2002). Reynolds stress and turbulent energy production in a tidal channel. Journal of Physical Oceanography, 32(4), 1242-1251.

Stacey, M. T., S. G. Monismith and J. R. Burau (1999), Measurements of Reynolds stress profiles in unstratified tidal flow. Journal of Geophysical Research, 104, 10933-10949.