Abstract
Coastal upwelling fronts have been generated around the outer edge of a cylindrical tank, filled with a two-layer fluid system and driven by a surface stress. Initially, an axisymmetric front was observed which subsequently became unstable to small baroclinic eddies. These eddies continued to grow until, eventually, they reached an equilibrium size. Under some circumstances, cyclonic eddies pinched-off from the fully developed front and moved away from the mean position of the front into the fluid interior. Streak photographs of the fully-developed, flow field were digitized to generate a velocity field interpolated onto a regular grid. A direct two-dimensional FFT was performed on the turbulent kinetic energy deduced from such images and one-dimensional energy (E) wavenumber (K) spectra were extracted. Consistently, K −5/3 energy spectra were found at lower K and approximately K −5 spectra at higher K. In any given experiment, the two spectral slopes meet close to a wavenumber K w = 2π/λ w (where λ w is the mean diameter of a frontal eddy). According to classical theories, K w would be the input wavenumber and the range of K with a K −5/3 spectrum the inverse energy cascade which yielded a Kolmogorov constant (C) that varied within the limits 3.6 ≤ C ≤ 6.3. The approximately K −5 range, which is much steeper than that predicted by the theories, is consistent with those found frequently in numerical experiments.
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Narimousa, S., Maxworthy, T., Spedding, G.R. (1991). Experiments On Forced, Quasi-Two-Dimensional Turbulence at Upwelling Fronts. In: Metais, O., Lesieur, M. (eds) Turbulence and Coherent Structures. Fluid Mechanics and Its Applications, vol 2. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-7904-9_21
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DOI: https://doi.org/10.1007/978-94-015-7904-9_21
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