Integrated Computational and Experimental Method for Flow Problems

数值分析和实验是流动分析的常用手段。然而，每种方法都有自己的缺点。数值分析的结果本质上依赖于数学模型和计算网格。数值解的一致性验证方法尚未建立。实验结果的评价相对容易，但通常只能给出有限的整个流场信息。因此，需要建立一种新的分析方法，将数值方法和实验方法相结合，以弥补它们的不足。本文将自动控制理论中的“观测器”概念应用到流动问题中。在观测器中，物理系统的状态由实时反馈测量数据的数学模型渐近估计。采用基于simpler的数值模拟算法作为数学模型，并根据实验测量结果与计算结果的差异修改边界条件和/或外力项。通过对方形管道内湍流流动的数值分析，验证了该观测器的有效性。并对其应用于湍流控制的可能性进行了研究。研究了数值方法的基本网格收敛特性，以及可折叠管流动系统中流动与管变形相互作用的特性，为今后的研究奠定了基础。这些结果为建立新的方法来处理传统的实验或计算方法不能有效适用的特别复杂的流动问题提供了基本信息。

Numerical analysis and experiment are common tools in flow analysis. Each of these methods, however, has own shortcomings. The result of numerical analysis inherently depends on the mathematical model and the computational grid. A consistent way of validation of numerical solutions has not been established yet. Evaluation of result is relatively easy in experiment, but it usually gives only limited information of the whole flow field. It is, therefore, desirable to establish a new analysis methodology in which the numerical and experimental methods are integrated to compensate their shortcomings.In the present research the concept of "observer" in automatic control theory is applied to flow problems. In the observer the state of the physical system in asymptotically estimated from the mathematical model to which the measurement data are fed back in real time. The SIMPLER-based numerical simulation algorithm is used as the mathematical model and the boundary condition and/or external force terms are modified based on the difference between the experimental measurement and computational result. Validity of the present flow observer was examined through numerical analysis for the turbulent flow in a square duct. Possibility in application to turbulent flow control was also studied. The fundamental grid convergence property of numerical methods, and characteristics of the collapsible tube flow system, in which the flow and the tube deformation interact, were investigated as the basic understandings of the future research.These results give fundamental information in establishing the new methodology to deal with especially complex flow problems to which conventional methods in experiment or computation do not apply effectively.