复合固体推进剂燃烧性能模拟计算的神经网络方法

在总结已有燃烧模型的基础上，重点考虑压强、氧化剂的重均粒径、氧化剂的质量浓度三种主要影响因素，提出了一种基于误差反传（ＢＰ）神经网络的复合固体推进剂燃烧性能模拟计算方法，计算结果和实验值吻合较好，这为推进剂配方的计算机辅助设计提供了一种新方法。     

空间光学系统技术发展探讨

文章总览国际典型大科学工程和计划，对空间光学系统技术在过去20年的发展做出了简要的归纳和总结。同时通过跟踪一些领域前沿和技术生长点，指出了一些可能对未来空间光学系统带来重大改变的方向。     

Analysis on capabilities of density-based solvers within OpenFOAM to distinguish aerothermal variables in difusion boundary layer

Open source feld operation and manipulation（OpenFOAM）is one of the most prevalent open source computational fluid dynamics（CFD）software.It is very convenient for researchers to develop their own codes based on the class library toolbox within OpenFOAM.In recent years,several density-based solvers within OpenFOAM for supersonic/hypersonic compressible flow are coming up.Although the capabilities of these solvers to capture shock wave have already been verifed by some researchers,these solvers still need to be validated comprehensively as commercial CFD software.In boundary layer where diffusion is the dominant transportation manner,the convective discrete schemes＇capability to capture aerothermal variables,such as temperature and heat flux,is different from each other due to their own numerical dissipative characteristics and from viewpoint of this capability,these compressible solvers within OpenFOAM can be validated further.In this paper,frstly,the organizational architecture of density-based solvers within OpenFOAM is analyzed.Then,from the viewpoint of the capability to capture aerothermal variables,the numerical results of several typical geometrical felds predicted by these solvers are compared with both the outcome obtained from the commercial software Fastran and the experimental data.During the computing process,the Roe,AUSM＋（Advection Upstream Splitting Method）,and HLLC（Harten-Lax-van Leer-Contact）convective discrete schemes of which the spatial accuracy is 1st and 2nd order are utilized,respectively.The compared results show that the aerothermal variables are in agreement with results generated by Fastran and the experimental data even if the1st order spatial precision is implemented.Overall,the accuracy of these density-based solvers can meet the requirement of engineering and scientifc problems to capture aerothermal variables in diffusion boundary layer.     

非均匀笛卡尔坐标系网格优化频散相关保持格式研究

为克服传统频散相关保持格式 (即 DRP格式 )在数值求解非均匀网格问题时由于寄生波的产生而导致的数值不稳定的问题 ,Cheong &Lee提出了一种网格优化频散相关保持格式 (即 GODRP格式 )。根据其优化思想 ,在非均匀笛卡尔坐标系网格条件下 ,推导得到了更为通用的 GODRP格式优化系数公式。针对 Cheong&Lee文中算例比较不是在同一基准上进行的不足之处 ,设计了一个极端恶劣条件下的非均匀笛卡尔网格 ,采用 GODRP格式和 DRP格式分别求解了二维初始扰动波传播的算例。计算结果表明 ,由于 GODRP格式具有与网格相关的自带粘性 ,不用再另外加入人工粘性便可获得精度较高的数值结果 ,避免了传统 DRP格式在给定粘性时人为经验的影响因素。对于非均匀笛卡尔网格 ,GODRP格式确实比传统 DRP格式更加通用 ,并可以得到更为准确的数值模拟效果      

Improvement of Baldwin-Lomax turbulence model for supersonic complex flows

Entropy represents the dissipation rate of energy. Through direct numerical simulation (DNS) of supersonic compression ramp flow, we find the value of entropy is monotonously decreasing along the wall-normal direction no matter in the attached or the separated region. Based on this feature, a new version of Baldwin-Lomax turbulence model (BL-entropy) is proposed in this paper. The supersonic compression ramp and cavity-ramp flows in which the original Baldwin-Lomax model fails to get convergent solutions are chosen to evaluate the performance of this model. Results from one-equation Spalart-Allmaras model (SA) and two-equation Wilcox k-x model are also included to compare with available experimental and DNS data. It is shown that BLentropy could conquer the essential deficiency of the original version by providing a more physically meaningful length scale in the complex flows. Moreover, this method is simple, computationally efficient and general, making it applicable to other models related with the supersonic boundary layer.     

ACOUSTIC PROPAGATION IN SHEARED MEAN FLOW USING COMPUTATIONAL AEROACOUSTICS

Acoustic propagation problems in the sheared mean flow are numerically investigated using different acoustic propagation equations, including linearized Euler equations （LEE） and acoustic perturbation equations （APE）. The resulted acoustic pressure is compared for the cases of uniform mean flow and sheared mean flow using both APE and LEE. Numerical results show that interactions between acoustics and mean flow should be properly considered to better understand noise propagation problems, and the suitable option of the different acous- tic equations is indicated by the present comparisons. Moreover, the ability of APE to predict acoustic propagation is validated. APE can replace LEE when the 3-D flowqnduced noise problem is solved, thus computational cost can decrease.     

随机编码感知的高分辨遥感光谱计算成像

传统遥感光谱成像系统的空间分辨率和光谱分辨率是衡量成像品质的重要指标,而它们受制于探测传感器的点阵密度,提高遥感光谱成像传感器的性能代价非常巨大。另一方面,在入射光能量一定的条件下,由于高分辨光谱的窄波段成像与低窄带辐射能量接收之间的矛盾,传统遥感光谱成像方法的空间分辨率和光谱分辨率往往难以兼得。如何利用普通探测器获得...     

微重力条件下部分充液贮箱中流体动力学行为的三维计算

简要介绍一个用于常重及微重力环境条件下，计算充液贮箱中非定常流体动力学行为的三维程序，该程序具有多种选择，提供了一个广泛应用的可能。文中亦给出了对充液４０％模型贮箱中非定常流体动力学行为的计算结果，计算是在ＣＲＡＹ－ＸＰ超高速计算机上完成的。     

自由场气动声学相似理论与实验研究

气动声学相似理论为现代叶轮机械气动声学设计提供了分析手段，其相似律包括频率相似准则和源强度相似准则两大类，在叶轮机械中离散噪声和宽频噪声分别源于不同的机理，因而其相似性质也不一样，并且还证明Ｒｅ修正是必需的。实验结果证明了理论分析，二者结合构成了自由场气动声学相似研究的基本框架。     

Erosion degradation characteristics of a linear electro-hydrostatic actuator under a high-frequency turbulent flow field

The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator (LEHA). Rather than the traditional statistical methods based on degradation data, the method proposed in this paper firstly analyzes the dominant progressive failure mode of the LEHA based on the working principle and working conditions of the LEHA. The Computational Fluid Dynamics (CFD) method, combining the turbulent theory and the micro erosion principle, is used to establish an erosion model of the rectification mechanism. The erosion rates for different port openings, under a time-varying flow field, are obtained. The piecewise linearization method is applied to update the concentration of contaminated particles within the LEHA, in order to gain insight into the erosion degradation process at various stages of degradation. The main contribution of the proposed model is the application of the dynamic concentration of contamination particles in erosion analysis of Electro-Hydraulic Servo Valves (EHSVs), throttle valves, spool valves, and needle valves. The effects of system parameters and working conditions on component wear are analyzed by simulations. The results of the proposed model match the expected degradation process.