Data from direct numerical simulations of disperse bubbly flows in a vertical channel are used to study the effect of the bubbles on the carrier-phase turbulence. We developed a new method, based on an extension of the barycentric map approach, that allows us to quantify and visualize the anisotropy and componentiality of the flow at any scale. Using this we found that the bubbles significantly enhance anisotropy in the flow at all scales compared with the unladen case, and that for some bubble cases, very strong anisotropy persists down to the smallest scales of the flow. The strongest anisotropy observed was for the cases involving small bubbles. Concerning the energy transfer among the scales of the flow, our results indicate that for the bubble-laden cases, the energy transfer is from large to small scales, just as for the unladen case. However, there is evidence of an upscale transfer when considering the transfer of energy associated with particular components of the velocity field. Although the direction of the energy transfer is the same with and without the bubbles, the behaviour of the energy transfer is significantly modified by the bubbles, suggesting that the bubbles play a strong role in altering the activity of the nonlinear term in the flow. The skewness of the velocity increments also reveals a strong effect of the bubbles on the flow, changing both its sign and magnitude compared with the single-phase case. We also consider the normalized forms of the fourth-order structure functions, and the results reveal that the introduction of bubbles into the flow strongly enhances intermittency in the dissipation range, but suppresses it at larger scales. This strong enhancement of the dissipation-scale intermittency has significant implications for understanding how the bubbles might modify the mixing properties of turbulent flows.

中文翻译：

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含气泡湍流中与尺度相关的各向异性、能量传递和间歇性

来自垂直通道中分散气泡流的直接数值模拟的数据用于研究气泡对载流相湍流的影响。我们基于重心地图方法的扩展开发了一种新方法，该方法使我们能够量化和可视化任何尺度的流动的各向异性和分量。利用这一点，我们发现与空载情况相比，气泡在所有尺度上都显着增强了流动的各向异性，并且对于某些气泡情况，非常强的各向异性持续到流动的最小尺度。观察到的最强各向异性是针对涉及小气泡的情况。关于流动尺度之间的能量转移，我们的结果表明，对于充满气泡的情况，能量转移是从大尺度到小尺度的，就像在空载的情况下一样。然而，当考虑与速度场的特定分量相关的能量转移时，有证据表明存在高档转移。尽管有和没有气泡的能量转移方向相同，但能量转移的行为被气泡显着改变，这表明气泡在改变流动中非线性项的活动方面起着重要作用。速度增量的偏度也揭示了气泡对流动的强烈影响，与单相情况相比，它的符号和大小都发生了变化。我们还考虑了四阶结构函数的归一化形式，结果表明，将气泡引入流动中极大地增强了耗散范围内的间歇性，但在更大范围内抑制了它。