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<p>This experimental study identifies the coherent structures of turbulent eddies over two different types of rough beds with roughness elements arranged in regular and staggered patterns. The changes in coherent structures are examined for superimposed surface waves on the steady flow. The instantaneous three-dimensional velocity signal is recorded by an Acoustic Doppler Velocimeter (ADV) in the proximity of a roughness element for a flow depth (<i>h)</i> = 20&#xa0;cm. Furthermore, changes in the sizes of larger eddies are analyzed against flow depth by the computed values of integral length scales. The larger eddies are found in the wave-current case with a lower wave frequency. Furthermore, the changes in Reynolds stress and all the stress fractions (inward interaction, outward interaction, ejection, and sweep) are explored against the water depth. The evaluation of the joint probability distribution density functions verified the results of the contributions of all stress components in the different quadrant events. For a fixed time window, the changes of eddy scales for two fixed depths (above the crest level) at the location of the strongest turbulence generation are described using wavelet decomposition.</p>

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Coherent Structures of Turbulent Eddies in a Wave-Current Co-existing Flow

  • 期刊论文

  • 发表日期：

    2025年7月1日

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  • Jayanta Shounda,
  • Kapil Roy,
  • Krishnendu Barman,
  • Koustuv Debnath,
  • Bijoy Singha Mazumder

摘要

This experimental study identifies the coherent structures of turbulent eddies over two different types of rough beds with roughness elements arranged in regular and staggered patterns. The changes in coherent structures are examined for superimposed surface waves on the steady flow. The instantaneous three-dimensional velocity signal is recorded by an Acoustic Doppler Velocimeter (ADV) in the proximity of a roughness element for a flow depth (h) = 20 cm. Furthermore, changes in the sizes of larger eddies are analyzed against flow depth by the computed values of integral length scales. The larger eddies are found in the wave-current case with a lower wave frequency. Furthermore, the changes in Reynolds stress and all the stress fractions (inward interaction, outward interaction, ejection, and sweep) are explored against the water depth. The evaluation of the joint probability distribution density functions verified the results of the contributions of all stress components in the different quadrant events. For a fixed time window, the changes of eddy scales for two fixed depths (above the crest level) at the location of the strongest turbulence generation are described using wavelet decomposition.