Sea Spray and Its Feedback Effects: Assessing Bulk Algorithms of Air–Sea Heat Fluxes via Direct Numerical Simulations
Sea Spray and Its Feedback Effects: Assessing Bulk Algorithms of Air–Sea Heat Fluxes via Direct Numerical Simulations
复制标题
海浪及其反馈效应：通过直接数值模拟评估空气-海洋热通量的批量算法
DOI：
10.1175/jpo-d-18-0193.1
复制
发表时间：
2019
影响因子：
3.5
通讯作者：
D. Richter
中科院分区：
文献类型：
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作者：
T. Peng;D. Richter
海雾交换动量、热量和水汽是模拟高风速下海-气表面热通量的主要不确定性因素之一。由于现有模型中的几个未经检验的假设和测量的低保真度，仍然存在关于模拟喷雾对海-气通量影响的适当方法的问题。在这项研究中，我们通过欧拉-拉格朗日模型对湍流中的喷雾液滴进行了理想化的直接数值模拟。然后，我们验证了Fairall等人的整体喷雾模型。和Andreas等人。以及来自域名系统的详细物理信息。我们发现，整体模型的基本假设的质量对控制喷雾微物理和寿命的时间尺度很敏感。虽然这两个模型都假设喷雾经历均匀而稳定的环境条件，但我们的结果表明，这一假设只适用于热力学时间尺度较长和寿命相对较短的液滴。当热力学时间尺度较短时，模型无法正确预测喷雾(如冷凝)的温度和半径变化，从而导致喷雾调节的热通量，从而高估了总热通量。此外，利用我们的双向耦合模拟，我们发现喷雾蒸发引起的负反馈可能在主体模型中缺失，这可能导致当将喷雾介导的通量作为相应界面通量的附加项处理时，对总热通量的进一步高估。我们进一步证明了在不同的流动雷诺数下，反馈效应是一致的，这表明这些结果在实际规模上是相关的。
Sea spray exchanging momentum, heat, and moisture is one of the major uncertainties in modeling air–sea surface heat fluxes under high wind speeds. As a result of several untested assumptions in existing models and low fidelity in the measurements, questions regarding the appropriate method for modeling the effects of spray on air–sea fluxes still exist. In this study, we implement idealized direct numerical simulations (DNS) via an Eulerian–Lagrangian model to simulate spray droplets in turbulent flows. Then, we verify the bulk spray models of Fairall et al. and Andreas et al. with the detailed physics from DNS. We find that the quality of the underlying assumptions of bulk models is sensitive to the time scales governing spray microphysics and lifetime. While both models assume that spray experiences a uniform and steady ambient condition, our results show that this assumption only works well for droplets with long thermodynamic time scales and relatively short lifetime. When the thermodynamic time scales are short, the models fail to predict the correct temperature and radius change of spray (e.g., condensation), thus spray-mediated heat fluxes, which in turn overestimates the total heat fluxes. Moreover, using our two-way coupled simulations, we find a negative feedback induced by the spray evaporation that may be missing in the bulk models, which could lead to further overestimates of the total heat flux when the spray-mediated flux is treated as an add-on to the corresponding interfacial flux. We further illustrate that the feedback effects are consistent under different flow Reynolds numbers, which suggests that the findings are relevant at practical scales.