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首页> 外文期刊>The Aeronautical Journal >Rotorcraft downwash impact on ship airwake: statistics, modelling, and simulation
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Rotorcraft downwash impact on ship airwake: statistics, modelling, and simulation

机译：旋翼飞机下水道对船舶空中航行的影响：统计，建模和模拟

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Helicopter downwash impact on ship airwake is addressed from a three-pronged approach: (1) Analysis of one-point statistics of autospectrum and two-point statistics of cross-spectrum and coherence from a Computational Fluid Dynamics database of flow velocities effected by helicopter downwash and shipboard airwake; (2) Development of a mathematical framework for extracting interpretive turbulence models in closed form from these autospectral statistics; and (3) Simulation through white-noise-driven filters for the extracted models. The framework begins with an earlier-exercised perturbation-type series expansion of the autocorrelation for all three velocity components, where the first term of the series has a form of the von Karman longitudinal or lateral correlation function. After transformation into equivalent series of autospectrum, the coefficients in the series are evaluated by satisfying theoretical constraints and fitting a curve on a set of selected autospectral data points generated from the database. The framework represents a sensible combination of series expansion, exploitation of a database, and theoretical constraints to provide a foothold on airwake-downwash phenomenon for engineering analysis. It ensures that the extracted model and the autospectral data points have the same time scale, mean square value, and asymptotic decay according to the Kolmogorov -5/3 Law. The framework's strengths and weaknesses, and its major advancement over the earlier series-expansion schemes are also addressed. Finally it is shown that downwash increases airwake energy (mean square value) by one order of magnitude, and almost all of this airwake-downwash energy is concentrated within the bandwidth (0.16 < f(Hz) < 1.6) that affects flight mechanics.
机译：直升机下冲对船舶空中航行的影响可以通过三方面的方法解决：（1）通过直升机下冲影响流速的计算流体动力学数据库，分析自动光谱的单点统计数据和交叉光谱和相干性的两点统计数据和舰载空中唤醒； （2）开发数学框架，从这些自动光谱统计数据中以封闭形式提取解释性湍流模型； （3）通过白噪声驱动的滤波器对提取的模型进行仿真。该框架从对所有三个速度分量的自相关的较早执行的摄动类型级数展开开始，其中级数的第一项具有冯·卡曼纵向或横向相关函数的形式。转换成等效的自动光谱序列后，可通过满足理论约束并在从数据库生成的一组选定的自动光谱数据点上拟合曲线来评估该系列中的系数。该框架代表了系列扩展，数据库开发和理论约束的合理组合，从而为工程分析提供了空前冲刷现象的立足点。根据Kolmogorov -5/3定律，它确保提取的模型和自动光谱数据点具有相同的时间标度，均方值和渐近衰减。还讨论了该框架的优点和缺点，以及与早期系列扩展方案相比的主要进步。最终表明，向下冲刷将空中唤醒能量（均方值）提高了一个数量级，并且几乎所有这种空中唤醒-冲刷能量都集中在影响飞行力学的带宽（0.16

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