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首页> 外文期刊>Physics of fluids >Nearshore natural convection induced by a periodic thermal forcing at the water surface
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Nearshore natural convection induced by a periodic thermal forcing at the water surface

机译：在水面上通过周期性迫使近岸自然对流引起的

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摘要

Field observations reveal that under calm weather conditions, natural convection resulting from spatial variations in the temperature field plays a significant role in promoting exchanges and mixings in lakes and reservoirs. The present investigation is concerned with natural convection generated by a periodically varying surface temperature within a reservoir model consisting of a sloping nearshore section and a flat offshore section. Three approaches, including derivation of analytical solution, numerical simulation, and scaling analysis, are integrated to reveal the variation of flow response with the intensity of the thermal forcing. The analytical solution reveals that for a sinusoidally varying surface temperature, a cosinusoidally varying surface heat flux is imposed if the duration of the period is sufficiently long. Numerical results show dramatic differences in flow response between conduction-dominated and convection-dominated thermal flow. The former is in phase with the cosinusoidal variation of surface heat flux, whereas the latter is in phase with the sinusoidal variation of surface temperature. The thermal forcing for conduction-dominated and convection-dominated flow is prescribed by surface heat flux and surface temperature, respectively. An evident phase lag is observed shortly after the thermal forcing switches sign. For convection-dominated flow with a Rayleigh number of 2 x 10(7), the maximum velocity during the cooling phase is significantly larger than that during the heating phase owing to the occurrence of flow instability during the cooling phase, which agrees with field observations. The scales for flow velocity and phase lag are derived by scaling analysis and verified by the results of numerical simulations.
机译：现场观察表明，在平静的天气条件下，温度场的空间变化产生的自然对流在促进湖泊和储层中的交换和混合方面发挥着重要作用。本研究涉及由储层模型内的周期性变化的表面温度产生的自然对流，包括倾斜的近海部分和平面近海部分。三种方法，包括分析解决方案的推导，数值模拟和缩放分析，以揭示与热迫使强度的流动响应的变化。分析解决方案揭示了对于正弦变化的表面温度，如果周期的持续时间足够长，则施加含有含有含有变化的表面热通量。数值结果表明了传导主导和对流主导的热流量之间的流动响应的巨大差异。前者与表面热通量的烯化变化相位，而后者与表面温度的正弦变化相位。用于传导支配和对流主导流动的热迫使分别通过表面热通量和表面温度规定。在热锻造开关标志之后不久会观察到明显的阶段滞后。对于具有2×10（7）的瑞利数的对流主导的流量，由于在冷却阶段期间发生流动不稳定性，冷却阶段期间的最大速度明显大于加热阶段期间的最大速度，这与现场观测同意。通过缩放分析和通过数值模拟结果验证的流速和相位滞后的尺度。

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  • 来源
    《Physics of fluids》 |2019年第8期|共15页
  • 作者

    Mao Yadan;

  • 作者单位

    China Univ Geosci Inst Geophys &

    Geomat Hubei Subsurface Multiscale Imaging Key Lab Wuhan 430074 Hubei Peoples R China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 流体力学;
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