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首页> 外文期刊>International journal of numerical methods for heat & fluid flow >Numerical study and POD snapshot analysis of flow characteristics for pulsating turbulent opposing jets
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Numerical study and POD snapshot analysis of flow characteristics for pulsating turbulent opposing jets

机译：脉动湍流相对射流流动特性的数值研究和POD快照分析

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Purpose The purpose of this study is to investigate the coherent structures of pulsed opposing jets by large eddy simulation (LES) model and proper orthogonal decomposition (POD) snapshot method. Flow pulsation as an active flow control method is considered for the enhancement of transport phenomena in impinging jets. The effect of flow pulsation parameters such as pulsation signal shape and frequency on the vortical coherent structures, the energy content of primary modes and their variation are studied numerically.Design/methodology/approach In this study, flow field of turbulent pulsating opposing jets has been simulated using LES. The result of the simulation in different time steps (snapshots) are stored and POD is applied on the snapshots. In this study, the POD method and calculation of spatial modes has been done using OpenFOAM, and time coefficients have been calculated using a MATLAB code.Findings The results of this study show that the flow excitation has a great effect on the coherent structure formation and the energy containment of fundamental modes of the flow. When the flow was excited by a harmonic sinusoidal or step function, the turbulent kinetic energy accumulated in the set of primary modes. On the other hand, the pulsed opposing jets had more regularity compared to the steady jets. The shapes, patterns and energy values of dominant modes depended on the inlet pulsation signal. An increase in pulsation frequency leads to an augmentation in energy content of the primary modes.Research limitations/implications The predictions may be extended to include various pulsation conditions such as: various amplitudes, Reynolds number and aspect ratio.Practical implications The results of this study are a valuable source of information for active control of transport phenomena in opposing jet configurations which is used in different industrial applications such as cooling, combustion, reactors, heating and drying processes.Originality/value In this study, the coherent structures and energy content of primary modes was studied for the first time by LES model and POD snapshot method and a comprehensive discussion on numerical results is provided.
机译：目的本研究的目的是通过大涡模拟（LES）模型和适当的正交分解（POD）快照方法研究脉冲对置射流的相干结构。为了增强撞击射流中的传输现象，人们考虑将流量脉动作为一种主动流量控制方法。数值研究了脉动信号的形状和频率等脉动参数对旋涡相干结构，一次模态能量含量及其变化的影响。设计/方法/方法在本研究中，湍流脉动对置射流的流场为使用LES模拟。存储不同时间步长（快照）的模拟结果，并将POD应用于快照。本研究使用OpenFOAM进行了POD方法和空间模态的计算，并使用MATLAB代码计算了时间系数。研究结果表明，流激励对相干结构的形成和形成具有很大的影响。流动基本模式的能量约束。当通过谐波正弦波或阶跃函数激发流动时，湍流动能累积在一组主要模式中。另一方面，与稳定射流相比，脉冲反向射流具有更大的规律性。主导模式的形状，模式和能量值取决于入口脉动信号。脉动频率的增加会导致初级模态能量的增加。研究局限/含意预测可能会扩展到包括各种脉动条件，例如：各种振幅，雷诺数和纵横比。实际意义本研究的结果是主动控制相反射流配置中的传输现象的有价值的信息来源，该配置用于不同的工业应用中，例如冷却，燃烧，反应堆，加热和干燥过程。原始数据/值本研究中，相干结构和能量含量通过LES模型和POD快照方法首次研究了主要模式，并对数值结果进行了全面讨论。

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