高超声速乘波飞行器气动特性研究

用计算流体力学和风洞试验的方法对以锥导乘波体为基础生成的高超声速乘波飞行器的气动性能进行了研究。结果表明，以马赫数6，攻角4度为设计状态的乘波体，在马赫数5～7，攻角4～6度的范围内，都具有良好的气动特性，升阻比接近4。最后，提出了一个简单的以参考温度方法为基础的粘性阻力分析方法。该方法配合使用风洞试验和计算流体的结果，可以用来验证计算流体中难以计算准确的粘性阻力，也可以用来分析在风洞试验难以直接得到的粘性阻力。对于工程上的粘性阻力分析是一个有用的办法。     

Waveform-based spaceborne GNSS-R wind speed observation: Demonstration and analysis using UK TechDemoSat-1 data

This paper explores two types of mathematical functions to fit single- and full-frequency waveform of spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R), respectively. The metrics of the waveforms, such as the noise floor, peak magnitude, mid-point position of the leading edge, leading edge slope and trailing edge slope, can be derived from the parameters of the proposed models. Because the quality of the UK TDS-1 data is not at the level required by remote sensing mission, the waveforms buried in noise or from ice/land are removed by defining peak-to-mean ratio, cosine similarity of the waveform before wind speed are retrieved. The single-parameter retrieval models are developed by comparing the peak magnitude, leading edge slope and trailing edge slope derived from the parameters of the proposed models with in situ wind speed from the ASCAT scatterometer. To improve the retrieval accuracy, three types of multi-parameter observations based on the principle component analysis (PCA), minimum variance (MV) estimator and Back Propagation (BP) network are implemented. The results indicate that compared to the best results of the single-parameter observation, the approaches based on the principle component analysis and minimum variance could not significantly improve retrieval accuracy, however, the BP networks obtain improvement with the RMSE of 2.55 m/s and 2.53 m/s for single- and full-frequency waveform, respectively.     

无动力飞行器的制导与控制系统

提出了考虑常值风影响时无动力飞行器的动力学方程。基于变结构控制策略设计了三维的制导律和控制律，以此高度非线性、强耦合、时变的模型为基础进行了六自由度仿真，仿真结果表明这种考虑了风影响的动力学模型更接近实际，制导律和控制律是有效的，具有工程应用价值。     

微下冲气流数值模拟

从大气动力学角度建立了三维冰雹云数值模型，利用此模型模拟研究了发生在美国丹佛机场的一起微下冲气流风切变，并与美国国家航空航天局公布的ＴＡＳＳ模型模拟结果进行了对比分析，得到一些重要结论，并指出了模拟工作中存在的问题。     

The scientific payload of the space-based Solar and Heliospheric Observatory (SOHO)

The space-based Solar and Heliospheric Observatory (SOHO) is a joint venture of ESA and NASA within the frame of the Solar Terrestrial Science Programme (STSP), the first Cornerstone of ESA's long-term programme Space Science — Horizon 2000. The principal scientific objectives of the SOHO mission are: a) a better understanding of the structure and dynamics of the solar interior using techniques of helioseismology, and b) a better insight into the physical processes that form and heat the Sun's corona, maintain it and give rise to its acceleration into the solar wind. To achieve these goals, SOHO carries a payload consisting of 12 sets of complementary instruments which are briefly described here.     

风场对重力波的滤波现象

对MillstoneHill台站数字测高仪DGS－256漂移探测数据进行的分析表明，背景风场对重力波扰动具有明显的滤波作用．这种滤波效应主要表现为：扰动传播方向具有顺时针旋转的日变化特征，扰动相对出现率峰值出现在扰动传播方向与背景风场方向之间的夹角为180°－225°之间．扰动时空尺度越小，其传播越趋向于逆风场方向．     

A quantum inspired genetic algorithm for multimodal optimization of wind disturbance alleviation flight control system

This paper develops a Quantum-inspired Genetic Algorithm (QGA) to find the sets of optimal parameters for the wind disturbance alleviation Flight Control System (FCS). To search the problem domain more evenly and uniformly, the lattice rule based stratification method is used to create new chromosomes. The chromosomes are coded and updated according to quantum-inspired strategies. A niching method is used to ensure every chromosome can converge to its corresponding local minimum in the optimization process. A parallel archive system is adopted to monitor the chromosomes on-line and save all potential feasible solutions in the optimization process. An adaptive search strategy is used to gradually adjust the search domain of each niche to finally approach the local minima. The solutions found by the QGA are compared with some other Multimodal Optimization (MO) algorithms and are tested on the FCS of the Boeing 747 to demonstrate the effectiveness of the proposed algorithm.     

Experimental characteristics of oblique shock train upstream propagation

The structure and dynamics of an oblique shock train in a duct model are investigated experimentally in a hypersonic wind tunnel. Measurements of the pressure distribution in front of and across the oblique shock train have been taken and the dynamics of upstream propagation of the oblique shock train have been analyzed from the synchronized schlieren imaging with the dynamic pressure measurements. The formation and propagation of the oblique shock train are ini-tiated by the throttling device at the downstream end of the duct model. Multiple reflected shocks, expansion fans and separated flow bubbles exist in the unthrottled flow, causing three adverse-pressure-gradient phases and three favorable-pressure-gradient phases upstream the oblique shock train. The leading edge of the oblique shock train propagates upstream, and translates to be asym-metric with the increase of backpressure. The upstream propagation rate of the oblique shock train increases rapidly when the leading edge of the oblique shock train encounters the separation bubble near the shock reflection point and the adverse-pressure-gradient phase, while the oblique shock train slow movement when the leading edge of the oblique shock train is in the favorable-pressure-gradient phase for unthrottled flow. The asymmetric flow pattern and oscillatory nature of the oblique shock train are observed throughout the whole upstream propagation process.     

Developing an engineering-statistical model for estimating aerodynamic coeffcients of helicopter fuselage

The design of the geometric shape of a helicopter fuselage poses a serious challenge for designers. The most important parameter in determining the shape of the helicopter fuselage is its aerodynamic coefficients. These coefficients are determined using two methods:wind tunnel test and computational fluid dynamics (CFD) simulation. The first method is expensive, time-consuming and limited. In addition, estimates in regions away from data can be poor. The second method, due to the limitations of numerical solution, the number of nodes and the used solution, is often inaccurate. In this paper, with the aim of accelerating the design process and achieving results with reasonable engineering accuracy, an engineering-statistical model which is useful for estimating the aerodynamic coefficients was developed, which mitigated the drawbacks of these two methods. First, by combining CFD simulation and regression techniques, an engineering model was pre-sented for the estimation of aerodynamic coefficients. Then, by using the data from a wind tunnel test and implementation of statistical adjustment, the engineering model was modified and an engineering-statistical model was obtained. By spending less time and cost, the final model provided the aerodynamic coefficients of a helicopter fuselage at the desired angles of attack with reasonable accuracy. Finally, three numerical examples were provided to illustrate the application of the pro-posed model. Comparative results demonstrate the effectiveness of the engineering-statistical model in estimating the aerodynamic coefficients of a helicopter fuselage.     

Study of parachute inflation process using fluid–structure interaction method

A direct numerical modeling method for parachute is proposed firstly, and a model for the star-shaped folded parachute with detailed structures is established. The simplified arbitrary Lagrangian–Eulerian fluid–structure interaction(SALE/FSI) method is used to simulate the inflation process of a folded parachute, and the flow field calculation is mainly based on operator splitting technique. By using this method, the dynamic variations of related parameters such as flow field and structure are obtained, and the load jump appearing at the end of initial inflation stage is captured. Numerical results including opening load, drag characteristics, swinging angle, etc. are well consistent with wind tunnel tests. In addition, this coupled method can get more space–time detailed information such as geometry shape, structure, motion, and flow field. Compared with previous inflation time method, this method is a completely theoretical analysis approach without relying on empirical coefficients, which can provide a reference for material selection, performance optimization during parachute design.