Transitional wave configurations between Type III and Type IV oblique-shock/bow-shock interactions

The interactions of oblique/bow shock waves are the key flow phenomena restricting the design and aerothermodynamic performance of high-speed vehicles. Type III and Type IV Shock/Shock Interactions(SSIs) have been extensively investigated, as such interactions can induce abnormal aerodynamic heating problems in hypersonic flows of vehicles. The transition process between these two distinct types of shock/shock interactions remains unclear. In the present study, a subclass of shock/shock interaction configuration is revealed and defined as Type IIIa. Type IIIa interaction can induce much more severe aerodynamic heating than a Type IV interaction which was ever reported to be the most serious in literature. The intense aerodynamic heating observed in this configuration highlights a new design point for the thermal protection system of hypersonic vehicles. A secondary Mach interaction between shock waves in the supersonic flow path of a Type III configuration is demonstrated to be the primary mechanism for such a subclass of shock/shock interaction configuration.     

基于数字孪生的航班链延误动态预测模型

针对复杂多变的航班运行环境，提出一种基于数字孪生的航班链延误动态预测模型，以改善传统预测方法的精度及自适应性。模型基于数字孪生航班链系统构建，采用滑动窗口下的多通道特征建模完成单元级航班延误预测，并提出一种混合优化策略进行模型参数的动态优化，最后通过孪生数据驱动的链式分析方法实现了全航班链的延误分析与修正。采用国内航班数据进行实验，得到在各个窗口下的航班延误平均绝对误差（Mean absolute error, MAE）为11.79 min，低于其他基线模型和静态模型；且引入孪生数据驱动分析和修正后，紧随其后的航班预测误差比此前进一步降低了6.44%。结果表明，模型有利于数字孪生航班链系统实现虚实交互，并具有优良的预测精度和自适应性。     

Bayesian uncertainty analysis of SA turbulence model for supersonic jet interaction simulations

The Reynolds Averaged Navier-Stokes(RANS) models are still the workhorse in current engineering applications due to its high efficiency and robustness. However, the closure coefficients of RANS turbulence models are determined by model builders according to some simple fundamental flows, and the suggested values may not be applicable to complex flows, especially supersonic jet interaction flow. In this work, the Bayesian method is employed to recalibrate the closure coefficients of Spalart-Allma...     

多孔介质对圆柱-翼型干涉噪声的影响

采用LES（large eddy simulation）+FW-H（Ffowcs Williams-Hawkings）方程，研究了圆柱表面使用不同PPI（pore number per inch）和厚度的多孔介质对圆柱尾迹及圆柱-翼型干涉噪声的影响，探索了多孔介质的降噪规律和机理。结果表明：多孔介质能稳定圆柱表面的剪切层，抑制旋涡脱落，从而削弱尾迹对下游翼型的影响，圆柱单音噪声最大可降79 dB，翼型单音峰值降低13.22 dB，宽频噪声降低20 dB；多孔材料PPI的变化对降噪效果影响较小，而厚度是影响流场模态、降噪效果及气动性能的一个关键参数；多孔材料厚度合适时，圆柱-翼型流场形态为“剪切层模态”，可有效降低湍流干涉噪声；多孔材料厚度较小时，发现了一种流场形态，即“剪切层-尾迹模态”，导致翼型噪声增大；合适的多孔介质厚度不仅降噪效果显著，对圆柱-翼型的气动性能也有改善作用。     

后排转子直径对对转螺旋桨气动和声学特性的影响

基于非线性谐波法和声类比模型，研究了不同后排转子直径对对转螺旋桨气动特性和噪声的影响规律。首先，利用单排螺旋桨风洞试验结果验证了数值计算方法的可靠性。随后，以某型对转螺旋桨为研究对象，研究了6种具有不同后排转子直径的对转螺旋桨模型。研究发现，对转螺旋桨后排转子直径“裁剪”会降低后排螺旋桨的拉力系数和功率系数，但对效率的影响不明显。随着后排转子直径的减小，前排转子的叶片通过频率下的噪声几乎没有变化，但高阶噪声变化幅度较大。后排转子减小0.25倍直径，后排转子的叶片通过频率下的噪声降低约为9 dB。后排转子直径“裁剪”不仅可以降低后排转子噪声，在一定程度上也可以降低前排转子的噪声。通过叶片“裁剪”，对转螺旋桨气动噪声降低5~6 dB。对转螺旋桨后排转子直径的减小，减弱了对转螺旋桨叶尖涡干涉和尾迹干涉，并减弱了前后排桨叶的势流场干涉，进而降低了对转螺旋桨的噪声辐射。     

模块化月球表层采样力学模型

因不受作业空间的限制，月球表层采样机具设计形式多样，为建模分析带来较大难度。为避免不同结构机具分析时重复建模，建立了一种模块化的月球表层采样力学模型。该模型将复杂的采样机具拆分成若干个基本面单元，基于朗肯土压力理论、最大抗剪强度理论和地基极限承载力理论对面单元在采样过程中的受力进行分析，组合各个面单元所受到的力获得复杂机具的力学模型。基于不同机具形式与贯入角度的模拟月壤贯入试验，对理论模型进行了试验验证，通过引入月壤密度沿深度的影响修正公式，将理论模型的误差率降低至8.2%。结果证明该力学模型和模块化理论可行，为后期月球表层采样机具的设计研发提供了参考。     

Development and coupling test of active spacecraft potential control – Next generation (ASPOC-NG)

The active spacecraft potential control (ASPOC) system developed in the 1990s emits positive ions to neutralise the spacecraft potential, such as used in several missions like Geotail, Equator-S, Cluster, Doublestar and MMS. With the experience gained, the next generation of the active spacecraft potential control (ASPOC-NG) instrument has been developed over the last three years. Thereby, three emission technologies were tested including Liquid Metal Ion Source (LMIS), Liquid Metal Electron Source (LMES) and Solid Metal Electron Source (SMES). The development of the emitter module by FOTEC and the corresponding electronics control unit by IWF is presented. Optimisations were carried out with the focus on the reduction of mass and power consumption to comply with the requirements of future scientific missions. Coupling tests of the modules and the electronics control unit were performed including range, accuracy and lifetime tests. Both ASPOC-NG instruments for positive and negative charge compensation and their performance values show excellent results.     

后桨桨距角对某共轴对转螺旋桨性能影响规律研究

共轴对转螺旋桨的桨距角对前后排桨的桨间气动干扰有重要影响,能够改变螺旋桨的气动性能。为了研究后桨桨距角对共轴对转螺旋桨的气动干扰影响,改善螺旋桨的气动性能,在来流马赫数0.453 的情况下,通过调节后桨桨距角的方式对6×6 构型的共轴对转螺旋桨进行数值计算,数值计算中使用非定常雷诺平均纳维—斯托克斯（URANS）方程结合SST 湍流模型的方法,并采用T-Rex 高质量网格生成技术研究桨距角对共轴对转螺旋桨桨间气动干扰的变化规律。结果表明：后桨在前排桨产生的预旋气流作用下,能够吸收一部分前桨的切向滑流能量,且气动效率高于前桨,前后桨的气动参数在一个旋转周期内出现12 次周期性波动;共轴对转桨的前后桨转速相同时,前桨桨距角不变,减小后桨桨距角,前后桨的气动效率都会增加,后桨效率提升明显。     

基于模型定义的复合材料旁路挤压试验压缩夹具参数化设计

针对民用飞机复合材料许用值试验开展中需要设计大量构型类似而繁杂的试验夹具,为提高夹具设计的效率和准确性、促进设计的标准化,本文总结了 ASTM标准中复合材料旁路挤压试验的压缩试验夹具构型设计和制造等相关信息,采用包含基于模型的定义(Model Based Definition,MBD)信息的CATIA二次开发方法,提出...     

Advanced analytical model for orbital aerodynamic prediction in LEO

The growing interest in low earth orbit (LEO) applications demands for accurate modeling of orbital aerodynamics. But classical analytical models of aerodynamic coefficients in free molecule flow, such as the Sentman’s model, Schamberg’s model and Schaaf-Chambre model, were built upon over simplistic gas-surface interaction models, which degrade the fidelity of aerodynamic prediction. This work presents a new analytical model of orbital aerodynamic coefficients based on the state-of-the-art Cercignani–Lampis–Lord (CLL) gas-surface interaction model, where lobular quasi-specular scattering pattern and separate accommodation degree for different velocity components can be well captured. A key component of the new model is a rigorous function approximation solution of the reflected normal momentum flux based on the CLL model which is derived for the first time and is validated within 1% for any hypothermal flow and surface accommodation conditions. Closed-form analytical solutions of aerodynamic coefficients for simple convex geometries are obtained and exhibit high accuracy (within 0.1%) in typical LEO scenarios. The new analytical model surpasses the classical models in some important aspects, such as overcoming the diffuse scattering hypothesis constraint, considering the variation of normal momentum exchange with the surface incidence angle and being applicable in any hypothermal flow situation. In virtue of the advanced CLL model and feasibility of coupling with the panel method technique, the new analytical model is promising to provide more accurate predictions on the orbital aerodynamic coefficients for LEO applications.