受不同风况影响的单色波下的湍流场

IF 4.5 2区 工程技术 Q1 ENGINEERING, CIVIL
Fabio Addona, Luca Chiapponi
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引用次数: 0

摘要

风波的相互作用影响着空气-水界面的动量、能量和化学物质的传递。在这项研究中,我们报告了实验室单色波下的湍流流场在不同的风速和方向(顺或反)下。流场被分解为三个主要部分:平均项、膨胀项和波动项,后者包括风致波纹和湍流的影响。在简要介绍了平均场和波动场之后,我们将注意力集中在波动湍流场上。我们的研究结果表明,湍流应力随着水摩擦力的增加而增加,并且在较深的水位处,风与膨胀相反的条件导致动量传递增强。波动动能(TKE)沿膨胀阶段的分布表明在槽处最大,这是前人对自由表面运动学的研究。此外,我们通过假设波以刚性平移传播来研究二维能量方程中有助于TKE产生的所有项。仔细观察TKE预算表明,在所有风况下,在槽前的背风面产生的TKE都是正的,随着风的膨胀,TKE风向被破坏,可能是由于遮蔽效应。然而,对于逆风,在膨胀阶段几乎无处不在的正产量,这将证明在特定条件下更大的平均TKE产量是合理的。讨论这些发现,以解决可能的原因;TKE收支的相位依赖行为归因于膨胀引起的加速度、波峰上的风切变、风波的随机相位偏移和微尺度破碎的共同作用。象限分析突出了动量转移的主要方向,并有助于爆发的个性化,即支持高动量转移的强事件。正如预期的那样,由于波动分量造成的净动量转移是从空气到水,条件平均(即波动速度的象限图)证实了这一发现。最后,对波动主应力张量的分析表明,各向异性随着水摩擦的增加而增加,尽管系统在空气-水界面以下趋于各向同性。对于跟随膨胀的风,主轴以−π/4的角度接近自由表面,这是在表面附近剪切流占主导地位时的典型特征。这些发现的重要意义包括提供进一步的数据,以改进海浪预报和对涌浪和风况的预测。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Turbulent field beneath monochromatic waves subjected to varying wind conditions
Wind-wave interaction affects momentum, energy, and chemicals transfer at the air–water interface. In this study, we report on the turbulent flow field beneath laboratory monochromatic waves subjected to different wind speeds and direction (following or opposing). The flow field is decomposed into three main components: a mean, a swell-induced, and a fluctuating term, the latter including the effects of wind-induced ripples and turbulence. After a brief survey on the mean and wave-induced fields, we focus our attention on the fluctuating-turbulence field. Our results show that the turbulent stresses increase with increasing water friction, and that the condition of wind opposing the swell results in enhanced momentum transfer at deeper water levels. The distribution of fluctuating kinetic energy (TKE) along the swell phase indicates a maximum at the trough, which was addressed to the kinematics of the free surface by previous researchers. Furthermore, we investigate all the terms in the 2D energy equations that contribute to the TKE production by assuming that waves propagate with a rigid translation. A close look to the TKE budget suggests positive production of TKE on the leeside before the trough for all wind conditions, with destruction of TKE windwards for wind following the swell, possibly due to a sheltering effect. For opposing wind, however, positive production is almost ubiquitous along the swell phase, and this would justify larger mean TKE production for that particular condition. These findings are discussed to address possible causes; the phase-dependent behavior of TKE budgets are attributed to the combined action of swell-induced acceleration, wind shear on the crest, the stochastic phase offsets of the wind waves, and microscale breaking. A quadrant analysis highlights the main direction of momentum transfer and helps the individuation of the bursts, i.e., of strong events that support high momentum transfer. As expected, the net momentum transfer due to the fluctuating components is from air to water, with conditional averages (i.e., the quadrant map of the fluctuating velocities) confirming that finding. Finally, the analysis of the fluctuating principal stresses tensor reports that anisotropy increases for increasing water friction, although the system tends to isotropic conditions immediately below the air–water interface. For wind following the swell, the principal axes approaches the free surface with an angle π/4, which is typical when a shear current is dominant near the surface. Important implications of these findings include the availability of further data to improve wave forecasting and prediction of swell and wind conditions.
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来源期刊
Coastal Engineering
Coastal Engineering 工程技术-工程:大洋
CiteScore
9.20
自引率
13.60%
发文量
0
审稿时长
3.5 months
期刊介绍: Coastal Engineering is an international medium for coastal engineers and scientists. Combining practical applications with modern technological and scientific approaches, such as mathematical and numerical modelling, laboratory and field observations and experiments, it publishes fundamental studies as well as case studies on the following aspects of coastal, harbour and offshore engineering: waves, currents and sediment transport; coastal, estuarine and offshore morphology; technical and functional design of coastal and harbour structures; morphological and environmental impact of coastal, harbour and offshore structures.
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