Low-Dimensional Models for Turbulent Heat Transfer in Flexible Cylinder Arrays

摘要 提案编号：CTS 9901732主要研究者： G. Karniadakis该奖项与9903346奖项一起用于支持对管束周围流动和传热的研究。从管束的湍流热传递强烈地依赖于所采用的特定几何配置，并且基本上受管可能经受的流致振动的影响。特别是，最近高强度材料的使用已经产生了更细长的结构，这更容易受到振动的影响。 现有的预测传热和流致振动的模型是半经验的，即使是最复杂的模型也严重依赖于时间相关系数，而这些系数很难测量。 在这项工作中，提出了一个模型，表现出一些复杂的湍流传热在灵活的圆柱阵列，但在一个简化的设置。 从实验和直接数值模拟研究的证据表明，尽管他们的复杂性，这种类型的耦合系统表现出低维，并可以有效地模拟使用动力系统技术的近似惯性流形理论的动机，使用非线性Galerkin模型的基础上，从数值和实验数据库中提取的分层模式，使用“快照方法”。这些模型，除了整体力系数和努塞尔数，提供详细的时空描述的速度和温度场。实验和数值数据库将获得在一个代表性的值的Peclet数使用DPIV/T测量和动态光谱模拟在以前的NSF赠款。更具体地说，这笔更新补助金的目标是双重的：首先，开发新的实验和模拟工具，使一般的流/热-结构相互作用问题的时间和空间分辨率高。第二，构建简化的动力学模型，保留完整系统的时空复杂性，并准确预测感兴趣的平均值和波动量。

ABSTRACT Proposal Number: CTS 9901732Principal Investigator: G. Karniadakis This award, in conjunction with award 9903346, is to support an investigation into the flow around and the heat transfer from tube banks. Turbulent heat transfer from tube banks depends strongly on the specific geometric configuration employed, and is influenced substantially by the flow-induced vibrations that the tubes may be subject to. In particular, the recent use of high strength materials has produced more slender structures, which are more susceptible to vibration. Existing models for predicting heat transfer and flow-induced vibrations are semi-empirical and even the most sophisticated ones depend critically on time-dependent coefficients, which are difficult to measure. In this work a model is proposed that exhibit some of the complexity of turbulent heat transfer in flexible cylinder arrays but in a simplified setting. Evidence from experimental and direct numerical simulation studies has shown that despite their complexity this type of coupled systems exhibit low-dimensionality and can be modeled effectively using dynamical systems techniques motivated by the theory of approximate inertial manifolds using nonlinear Galerkin models based on hierarchical modes extracted from numerical and experimental data bases using the ``method of snapshots". These models, in addition to the overall force coefficients and Nusselt number, provide detailed spatio-temporal description of the velocity and temperature fields. The experimental and numerical data bases will be obtained at one representative value of Peclet number using DPIV/T measurements and dynamic spectral simulations developed in a previous NSF grant. More specifically, the objective of this renewal grant is two-fold: First, to develop new experimental and simulation tools that will enable high temporal and spatial resolution of general flow/heat-structure interaction problems. Second, to construct reduced dynamical models that retain the spatio-temporal complexity of the full systems and predict accurately the mean and fluctuating quantities of interest.