新型排翼式浮升一体化飞艇的布局设计和气动研究

以传统的NACA系列翼型为基准,设计一类实用高效的新型排翼式浮升一体化飞艇.通过数值计算,对浮升一体化飞艇的气动问题和布局设计展开系统的研究,综合分析和评估各气动布局形式的浮升特性.研究结果表明:排翼式浮升一体化飞艇不仅具有接近常规飞艇的体积效率,而且利用后翼对前翼下表面气流形成的阻滞和排翼重叠区域之间的气流加速作用,其总体升阻比较单排翼增大50%以上,当速度大于30 m·s^-1之后可以使飞艇的自重降低,有效载荷提高;同时,排翼式飞艇的弦向尺寸较小,可有效降低材料的表面张力,为高空飞艇表面柔性材料提供了较宽的选择范围.     

电动水上飞机低噪声螺旋桨翼型优化

为降低翼型的气动噪声,以某型电动水上飞机螺旋桨所使用的RAF-6翼型为研究对象,首先通过CFD/FW-H方法计算得到翼型的升、阻力系数以及气动噪声;其次使用型函数线性叠加描述翼型的几何形状;进而,为使翼型获得设计状态下较好的声学与气动性能,由翼型的气动噪声与升阻比构成优化目标,以型函数系数为变量,以保证翼型升、阻力系数变化不超过10%为约束,使用引入响应面模型的遗传算法对翼型进行降噪优化。通过优化翼型与基准翼型的对比可知,设计状态的优化翼型气动噪声声压级降低了2.17 dB,升阻比提高1.12%,且优化翼型在小攻角状态下具有较为优异的声学与气动性能。优化结果表明,该优化方法具有一定应用价值,可为螺旋桨噪声控制研究提供参考。     

CFD/CSD耦合飞行器多学科优化设计新方法

文章以飞行器巡航外形为设计对象, 构建了一种新的飞行器的气动和结构特性评估方法, 即结构模型反迭代方法.该方法较传统的松耦合静气动弹性方法效率提高了4倍以上.以此为基础建立了一种新的飞行器气动/结构耦合多学科优化设计框架, 将优化效率提高4倍以上.采用数值求解N-S方程和结构有限元方程方法作为气动和结构学科的分析工具, 保证了设计结果的可信性.算例表明以巡航外形作为设计对象能够获得与传统方法一致的飞行器气动与结构特性, 以此为基础开展的无人机气动外形优化设计也获得了良好的设计结果.      

基于遗传算法的升力体外形优化设计

升力体由于低热流率再入物理特性和高效的内部容积利用率，是高超声速飞行器气动外形的一种典型布局.文章对升力体飞行器进行参数化数值建模，并提取其表征外形的参数作为设计变量，综合考虑飞行器再入过程中的气动力、气动热、容积利用率及稳定性等性能指标.运用多目标混合遗传算法对升力体进行了多变量、多约束下的气动外形优化设计，获得了再入飞行器外形的最优Pareto解.数值模拟结果表明，典型状态下最优Pareto解与CFD结果相差12%，验证了优化结果的准确性.      

使用类别形状函数的多目标气动外形优化设计

在飞行器的气动外形优化设计中, 参数化方法和优化算法具有十分重要的作用, 对优化的计算时间设计空间的数学特性有着深刻的影响.类别形状函数(class and shape transformation, CST)方法是一种简洁高效的参数化方法, 但对于复杂曲面很难使用统一的CST方法进行拟合.文章首先介绍了CST方法的三维实现, 分析了其数学性质, 提出了分块CST参数化方法, 保留CST方法的特性, 实现了分块曲面之间的光滑连接.针对气动外形优化设计的复杂情况, 需要根据具体的飞行任务提出设计目标, 并处理不同目标的矛盾问题.其次采用Pareto策略自动寻找最优方案集, 并基于分块CST参数化方法遗传算法和气动力快速计算方法, 对类乘波翼身组合飞行器进行了优化设计, 并改变原有问题的设定条件优化得到了全新外形.研究结果表明分块CST方法参数少, 精度高, Pareto策略处理多目标准确有效, 是气动外形优化设计中非常有用的工具.      

气动外形表面雷达吸波涂层问题电磁散射场的数值模拟

研究了将无覆盖区域分裂与精确控制法相结合、用于气动外形表面雷达吸波涂层问题电磁散射场的数值求解方法.无覆盖区域分裂是按空气和涂层两种不同介质物理分区要求进行的,子域交界处离散网格彼此之间可以是非匹配的,以便处理不同介质的不同网格尺度要求.电磁波通过子域交界面的约束条件是通过引入Lagrange乘子而弱满足.整个求解过程包含基于精确控制的外迭代和基于Lagrange乘子控制的区域分裂内迭代.最后计算给出了二维翼型气动外形涂层问题的电磁散射场,并与对应的无涂层外形的计算结果进行了比较,反映出表面涂层对电磁散射场的影响.     

基于径向基函数和Delaunay图映射的高效高鲁棒性的非结构网格变形方法

对于气动外形优化、气动弹性计算等涉及更新流场计算网格的问题,网格变形方法的效率和鲁棒性对整个研究过程有显著影响。其中径向基函数(radial basis function, RBF)方法能够保证较高的网格质量,但是当空间及物面网格数量较多时效率极低。而Delaunay图映射(Delaunay graph mapping, DGM)方法效率很高,但在大变形时网格质量会迅速下降。因此,将结合RBF和DGM两种方法的优点,利用网格聚合方法自动生成背景网格,通过RBF方法更新背景网格,解决DGM方法无法适用于物面大变形的问题,利用DGM方法提高变形效率,建立一种高效高鲁棒性网格变形方法。通过对比,网格变形质量方面该方法能够和RBF方法基本保持一致,且对于本文三维网格算例,网格变形效率较RBF方法能够提升90%以上。     

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基于介质阻挡放电等离子体的体积力气动激励机理,仿真研究了等离子体增升减阻技术对沿螺旋桨桨径方向均匀分布的10个叶素气动特性的改善效果.采用叶素理论,对比分析了等离子体对螺旋桨整体气动性能的提高效果.主要结论有:桨尖和桨叶根部的叶素容易发生气动分离现象,其中根部叶素处于负攻角的工况中;采用介质阻挡放电等离子体流动控制技术可以完全抑制流动分离不太严重的桨叶中部区域的叶素气动分离,对桨尖处翼型的严重气动分离不能完全抑制但也有改善作用,但对处于负攻角工况的叶素作用不大;等离子体增升减阻技术确实可以提高螺旋桨的气动性能,对本文所研究的情况,螺旋桨的拉力和效率分别提高了28.27％和 12.3％.     

DLR-F6翼身组合体阻力计算

采用"亚跨超CFD软件平台"(TRIP2.0)数值模拟DLR-F6翼身组合体构型,采用的多块对接网格、测压和测力的试验结果均来自美国AIAA阻力计算小组,对比计算结果采用CFL3D的结果.详细研究网格密度、湍流模型对DLR-F6翼身组合体构型的总体气动特性和压力分布的影响,计算结果与相应的试验结果较一致.采用SST两方程模型得到网格收敛结果;不同的湍流模型对压差阻力影响较小,对摩擦阻力影响较大;不同的网格密度和湍流模型对压力分布影响较小.     

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基于介质阻挡放电等离子体体积力气动激励机理,数值研究了两种等离子体流动控制方案对螺旋桨桨径根部处于负攻角工况下叶素气动性能的改善效果.结果显示,激励器布置在下翼面时等离子体体积力大于其布置在叶素前后缘时的情况;激励器布置在下翼面时,可抑制流动分离,使得螺旋桨桨根部位叶素产生更大的负拉力,但会减小螺旋桨的扭矩;激励器布置在前后缘时,会使螺旋桨根部叶素拉力增大,提高螺旋桨总拉力,但不能抑制流动分离,所以会增大螺旋桨的扭矩.     

Propeller sheet cavitation noise source modeling and inversion

Propeller sheet cavitation is the main contributor to high level of noise and vibration in the after body of a ship. Full measurement of the cavitation-induced hull pressure over the entire surface of the affected area is desired but not practical. Therefore, using a few measurements on the outer hull above the propeller in a cavitation tunnel, empirical or semi-empirical techniques based on physical model have been used to predict the hull-induced pressure (or hull-induced force). In this paper, with the analytic source model for sheet cavitation, a multi-parameter inversion scheme to find the positions of noise sources and their strengths is suggested. The inversion is posed as a nonlinear optimization problem, which is solved by the optimization algorithm based on the adaptive simplex simulated annealing algorithm. Then, the resulting hull pressure can be modeled with boundary element method from the inverted cavitation noise sources. The suggested approach is applied to the hull pressure data measured in a cavitation tunnel of the Samsung Heavy Industry. Two monopole sources are adequate to model the propeller sheet cavitation noise. The inverted source information is reasonable with the cavitation dynamics of the propeller and the modeled hull pressure shows good agreement with cavitation tunnel experimental data.     

基于分解策略的飞行器气动隐身优化设计研究

为了综合提高飞行器的气动性能与隐身性能,文章利用基于分解策略的梯度优化方法,对某跨声速机翼进行气动隐身综合优化设计.采用Tchebycheff方法,将气动隐身多学科多目标优化问题分解为多个单目标优化子问题,再对每个单目标子问题进行梯度优化.通过求解离散伴随方程获得气动目标对设计变量的梯度,采用自动微分方法对物理光学法（physical optics,PO）程序进行微分,即可得到雷达散射截面（radar cross section,RCS）对设计变量的梯度.经过综合优化,获得优化解集中各给定权重系数对应下的分支解,相比初始机翼,优化机翼的阻力系数减小,升阻比提高,重点方位的雷达散射截面均值减小,验证了该优化设计方法具有较好的实用性.      

Minimisation of the sound power radiated by a submarine through optimisation of its resonance changer

An important cause of sound radiation from a submarine in the low frequency range is fluctuating forces at the propeller. The forces are transmitted to the hull via the shaft and the fluid. Sound radiation occurs due to hull and propeller vibrations as well as dipole sound radiation caused by the operation of the propeller in a non-uniform wake. In order to minimise sound radiation caused by propeller forces, a hydraulic vibration attenuation device known as a resonance changer can be implemented in the propeller/shafting system. In this work, cost functions that represent the overall radiated sound power are investigated, where the virtual stiffness, damping and mass of the resonance changer were chosen as design parameters. The minima of the cost functions are found by applying gradient based optimisation techniques. The finite element and boundary element methods are used to model the structure and the fluid, respectively. The adjoint operator is employed to calculate the sensitivity of the cost function to the design parameters. The influence of sound radiation due to propeller vibration on the optimisation of the resonance changer as well as the influence of the reduction in amplitude for higher harmonics of the blade-passing frequency on the control performance is investigated.     

Non-cavitating propeller noise modeling and inversion

Marine propeller is the dominant exciter of the hull surface above it causing high level of noise and vibration in the ship structure. Recent successful developments have led to non-cavitating propeller designs and thus present focus is the non-cavitating characteristics of propeller such as hydrodynamic noise and its induced hull excitation. In this paper, analytic source model of propeller non-cavitating noise, described by longitudinal quadrupoles and dipoles, is suggested based on the propeller hydrodynamics. To find the source unknown parameters, the multi-parameter inversion technique is adopted using the pressure data obtained from the model scale experiment and pressure field replicas calculated by boundary element method. The inversion results show that the proposed source model is appropriate in modeling non-cavitating propeller noise. The result of this study can be utilized in the prediction of propeller non-cavitating noise and hull excitation at various stages in design and analysis.     

基于Kriging代理模型的飞行器结构刚度气动优化设计

大飞机具有轻质大柔性特点,使得气动/结构耦合作用增强,在设计过程中需要考虑这种耦合效应,直接调用CSD/CFD方法计算周期长,无法满足工程需要.代理模型方法由于能显著提高工程优化设计的效率,已广泛应用于飞行器气动外形优化设计中.采用Kriging方法建立代理模型,通过求解EI函数最大值得到需添加的样本点以更新代理模型,提高代理模型的拟合精度,结合改进的粒子群最优化方法对大飞机的结构刚度进行了优化设计.结果表明,该优化方法能够处理复杂目标的全局优化问题,在保证升力系数及纵向稳定性能不恶化的前提下,降低飞机巡航状态的飞行阻力.      

微尺度色谱通道截面形状优化

本文将基于体积平均方法的理论模型与拓扑优化工具结合,以减小弥散系数为优化目标对微尺度色谱通道的截面形状进行了优化。优化结果表明色谱通道截面形状优化可以明显削弱通道内弥散过程。优化得到的截面形状明显不同于常见的矩形截面,具体形状取决于流动阻力系数的数值,流动阻力系数越大,截面的宽高比越大。将优化截面用于微尺度色谱设计可以显著改善分离速度及分离精度。     

Visualization of the inflow ahead of a rotating propeller attached to a container ship model

The inflow ahead of a rotating propeller attached to a container ship model was visualized using a two-frame particle image velocimetry (PIV) technique. For illuminating the inflow region, a transparent window was installed at the stern of the ship model. Ensemble-averaged mean velocity fields were measured at four different blade phases under the design loading condition. The characteristics of the inflow in the upper plane above the propeller axis are quite different from those below the propeller axis. In the far upstream region above the propeller axis, most of the inflow comes from the hull wake and the axial velocity is very small. As the inflow moves toward the propeller plane, its axial velocity component increases rapidly. In addition, the variation of the inflow characteristics with respect to phase angle becomes apparent. The thick hull boundary layer and out-of-plane motion resulting from the propeller rotation produce a large turbulent kinetic energy around the tip of the propeller blade in the upper inflow region. The axial velocity distribution of the propeller inflow is asymmetric with respect to the vertical center axis, exhibiting different axial velocities on the port and starboard sides.     

Active control of sound radiated by a submarine in bending vibration

This paper theoretically investigates the use of inertial actuators to reduce the sound radiated by a submarine hull in bending vibration under harmonic excitation from the propeller. The radial forces from the propeller are tonal at the blade passing frequency and are transmitted to the hull through the stern end cone. The hull is modelled as a fluid loaded cylindrical shell with ring stiffeners and two equally spaced bulkheads. The cylinder is closed by end-plates and conical end caps. The actuators are arranged in circumferential arrays and attached to the prow end cone. Both Active Vibration Control and Active Structural Acoustic Control are analysed. The inertial actuators can provide control forces with a magnitude large enough to reduce the sound radiated by the vibrations of the hull in some frequency ranges.     

融合插值点优化的多项式结构宽带波束形成器设计方法

多项式结构设计方法是主瓣指向可调宽带波束形成器设计的一类重要方法。多项式结构的阶数是有限的,导致主瓣实际指向与期望指向之间存在偏差,因而影响了波束形成器的指向性指数。针对这一问题,该文提出了一种基于插值点优化的多项式结构宽带波束形成器设计方法。首先,引入多项式结构插值点处阵列响应的空间导数约束,以减小主瓣指向偏差;进而利用粒子群优化算法对多项式结构中的插值点进行优化,以充分利用插值点位置提供的自由度进一步提升多项式结构宽带波束形成器的性能。优化设计结果表明,与现有设计方法相比,该文提出的方法不仅降低了主瓣的指向偏差,同时也提高了指向性指数,有效改善了多项式结构宽带波束形成器的性能。