Triad interactions investigated by dual wave component injection

IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Experimental Thermal and Fluid Science Pub Date : 2024-05-27 DOI:10.1016/j.expthermflusci.2024.111239
Preben Buchhave , Mengjia Ren , Clara M. Velte
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Abstract

The study of the exchange of momentum and energy between wave components of the turbulent velocity field, the so-called triad interactions, offers a unique way of visualizing and describing turbulence. Most often, this study has been carried out by direct numerical simulations or by power spectral measurements. Due to the complexity of the problem and the great range of velocity scales in high Reynolds number developed turbulence, direct measurements of the interaction between the individual wave components have been rare. In the present work, we present measurements and related computations of triad interactions between controlled wave components injected into an approximately laminar and uniform flow from an open wind tunnel by vortex shedding from two rods suspended into the flow. This results in two-dimensional interactions of three-dimensional turbulence, which makes the analysis of the triadic interactions considerably less complex to analyze than in a fully developed three-dimensional flow. With the information obtained from the computations, we are able to isolate the individual triad interactions contributing to the generated frequency components as the flow develops downstream as well as understanding, mapping out and predicting the strengths of these interactions. The analysis also provides the time constants governing the development of higher order frequency components. We are thus able to see the pattern of frequency combinations, the strengths of the individual mode combinations and the time sequence in which they occur. Any of the higher order combinations is not just the result of a single term in the Navier–Stokes Equation, but a combination of various previous combinations occurring with different strengths and in a varied pattern of generation. The combination of these experiments and computations thus provide unique insight into the inner workings of turbulence and shows how the nonlinear term in the Navier–Stokes equation on average forces the energy towards higher frequencies, which is the reason for the so-called energy cascade.

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通过双波分量注入研究三元组相互作用
研究湍流速度场中波浪成分之间的动量和能量交换,即所谓的三元相互作用,为可视化和描述湍流提供了一种独特的方法。这种研究通常通过直接数值模拟或功率谱测量来进行。由于问题的复杂性以及高雷诺数发达湍流中速度尺度的巨大范围,对单个波成分之间相互作用的直接测量非常罕见。在本研究中,我们介绍了通过悬浮在气流中的两根棒的涡流脱落,从开放式风洞注入近似层流和均匀气流的受控波成分之间的三元相互作用的测量和相关计算。这导致了三维湍流的二维相互作用,使得三元相互作用的分析复杂程度大大低于完全发展的三维流动。利用从计算中获得的信息,我们能够分离出随着流动向下游发展而产生频率成分的单个三元相互作用,并了解、绘制和预测这些相互作用的强度。分析还提供了高阶频率成分发展的时间常数。因此,我们可以看到频率组合的模式、单个模式组合的强度以及它们发生的时间顺序。任何高阶组合都不仅仅是纳维-斯托克斯方程中单个项的结果,而是先前以不同强度和不同生成模式出现的各种组合的组合。因此,这些实验和计算的结合提供了对湍流内部运作的独特见解,并显示了纳维-斯托克斯方程中的非线性项如何平均地迫使能量向更高频率流动,这就是所谓的能量级联的原因。
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来源期刊
Experimental Thermal and Fluid Science
Experimental Thermal and Fluid Science 工程技术-工程:机械
CiteScore
6.70
自引率
3.10%
发文量
159
审稿时长
34 days
期刊介绍: Experimental Thermal and Fluid Science provides a forum for research emphasizing experimental work that enhances fundamental understanding of heat transfer, thermodynamics, and fluid mechanics. In addition to the principal areas of research, the journal covers research results in related fields, including combined heat and mass transfer, flows with phase transition, micro- and nano-scale systems, multiphase flow, combustion, radiative transfer, porous media, cryogenics, turbulence, and novel experimental techniques.
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