基于高精度HDCS格式的复杂喷嘴亚声速射流噪声计算方法研究

The study of jet-noise on complex nozzle configurations by numerical methods has important significance, however, there are two key problems needed to be solved. First, the implementation of high accuracy simulation on complex geometry is needed, because acoustic waves usually have small amplitudes, oftentimes, the sound intensity is three to five orders smaller than the mean flow. Secondly, because jet noise is often generated by turbulent flow, high accuracy simulation of turbulent flow is needed. For the first problem, this project will formulate stable fifth-order interface boundary scheme to implement seventh-order hybrid dissipative compact scheme(HDCS) on three-dimension complex meshes. For the problem of turbulent flow, the relation between the dissipation of seventh-order HDCS and the implicit large eddy simulation will be examined, and the implict large eddy simulation(LES) based on the seventh-order HDCS is obtained. Then the influence of geometry on the noise will be investgated by numerical solutions of jet on nozzle with chevrons.

采用数值方法研究复杂嘴射流噪声具有重要的意义，但是需要解决两个关键问题。第一，噪声脉动比平均流动量低3～5个量级，因此需要在接近复杂外形上实现高精度计算。第二，由于射流噪声有很大一部分是由于湍流引起，因此需要实现湍流的高精度模拟。针对第一个问题，本项目拟建立稳定高阶的对接边界格式，在复杂多块结构网格上实现七阶线性耗散紧致格式（HDCS）。针对湍流问题，项目将研究格式耗散与隐式大涡模拟的关系,建立基于七阶HDCS格式的隐式大涡数值模拟方法。在此基础上，预测带典型边缘喷嘴的射流噪声，分析喷嘴外形对噪声的影响。

发展了气动噪声高精度数值模拟方法，空间导数离散采用了HDCS-E8T7格式及精度与之匹配的边界格式，时间离散方法采用了高精度多步龙格库塔方法和高精度隐式双时间步方法，发展了高精度对接边界算法，将方法推广至多块对接网格以满足解决复杂几何构型问题的需要，采用隐式大涡的概念处理可能出现的湍流问题。在此基础上，研究了几何守恒律对计算结果的影响，展示了复杂网格中高精度计算满足几何守恒律的重要性，完成了等熵涡、双圆柱散射、串列柱翼构型和喷嘴射流等典型噪声问题的求解，所得计算结果展示了所发展的模拟方法具有良好的预测精度和解决复杂构型气动噪声问题的潜力。

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