汽车车身局部复杂曲面造型的计算方法

本文结合汽车车身复杂外形设计的实际，运用重节点型B样条曲线曲面理论，研究了汽车车身局部复杂曲面的造型方法，阐述了汽车车身局部复杂曲面造型的具体计算方法，为汽车车身复杂曲面的处理提供了一种有效的手段。     

基于序贯回归的小样本测试性验证试验方案

针对现有测试性验证试验方案难以实现较小样本量下满足置信水平要求的测试性评估问题,提出了基于序贯回归的小样本测试性验证试验方案。提出并证明了成败型试验序贯样本回归可行性假设;对序贯样本进行回归分析,实现了小样本下的测试性评估;建立了评估优化方案,实现了满足置信水平要求的测试性评估。实例验证表明:该方法可同时适用于有双方风险要求和置信水平要求的场合,且完所需样本量明显减少,在案例中平均减少了22.3%,最大减少了85%。      

An efficient aerodynamic shape optimization of blended wing body UAV using multi-fidelity models

This paper presents a novel optimization technique for an efficient multi-fidelity model building approach to reduce computational costs for handling aerodynamic shape optimization based on high-fidelity simulation models. The wing aerodynamic shape optimization problem is solved by dividing optimization into three steps—modeling 3D(high-fidelity) and 2D(lowfidelity) models, building global meta-models from prominent instead of all variables, and determining robust optimizing shape associated with tuning local meta-models. The adaptive robust design optimization aims to modify the shape optimization process. The sufficient infilling strategy—known as adaptive uniform infilling strategy—determines search space dimensions based on the last optimization results or initial point. Following this, 3D model simulations are used to tune local meta-models. Finally, the global optimization gradient-based method—Adaptive Filter Sequential Quadratic Programing(AFSQP) is utilized to search the neighborhood for a probable optimum point. The effectiveness of the proposed method is investigated by applying it, along with conventional optimization approach-based meta-models, to a Blended Wing Body(BWB) Unmanned Aerial Vehicle(UAV). The drag coefficient is defined as the objective function, which is subjected to minimum lift coefficient bounds and stability constraints. The simulation results indicate improvement in meta-model accuracy and reduction in computational time of the method introduced in this paper.     

Model Development and Adaptive Imbalance Vibration Control of Magnetic Suspended System

对星载磁悬浮单框架控制力矩陀螺,建立其转子的平动与转动的动力学方程。所建模型反映了转子的动、静不平衡特性,以及转子运动与框架、星体运动的耦合关系。模型是主动磁悬浮控制与动框架效应分析的基础。对动、静不平衡量未知的转子,设计了自适应对中控制器。在分散PD、比例交叉反馈控制器与高低通滤波器的基础上,通过动、静不平衡量的辨识与补偿控制,使转子绕其惯量主轴旋转,衰减角动量交换执行机构高速转子因不平衡而对基座产生的干扰力,消除星上主要颤振源,达到降低卫星姿态抖动的目的。     

空间站的混合自适应控制

本文推导出两板空间站的连续传递矩阵左分解模型;在此基础上,建立了该空间站的一种极点配置混合自适应控制算法,通过计算机仿真验证了该算法的有效性和鲁棒性。     

A mesh optimization method using machine learning technique and variational mesh adaptation

Computational mesh is an important ingredient that affects the accuracy and efficiency of CFD numerical simulation. In light of the introduced large amount of computational costs for many adaptive mesh methods, moving mesh methods keep the number of nodes and topology of a mesh unchanged and do not increase CFD computational expense. As the state-of-the-art moving mesh method, the variational mesh adaptation approach has been introduced to CFD calculation. However, quickly estimating the flow fi...     

Aeroacoustic and aerodynamic optimization of propeller blades

It is of great significance to develop a high-efficiency and low-noise propeller optimization method for new-generation propeller aircraft design. Coupled with free form deformation method, dynamic mesh interpolation technology, optimization algorithm, surrogate model, aerodynamic calculation and aeroacoustic prediction model module, the integrated aerodynamic and aeroacoustic design method of propeller is built. The optimization design for the six-blade propeller is carried out. The non-reduction in efficiency, thrust coefficient and the minimum of aerodynamic noise is treated as the optimization design objective. The spatial vorticity distribution of the propeller before and after the design is also analyzed by using unsteady computational fluid dynamics method. The results show that the optimized propeller can effectively reduce the aerodynamic noise level. The maximum total sound pressure level can be reduced by 5 dB without reducing its aerodynamic performance. The developed method has good application potential in low-noise optimization design of propeller and other rotating machinery.     

热输入对AZ31镁合金FSP试样力学性能的影响

分别利用普通钢制垫板和自制的带有冷水通道的铜制垫板,对AZ31镁合金进行了搅拌摩擦加工。利用光学显微镜(OM)、SEM、显微硬度仪和拉伸设备,研究了被加工件厚度、搅拌头焊接速率和冷却条件对试样搅拌区力学性能的影响。研究表明:试样搅拌区从上层至中层和底层,再结晶晶粒尺寸依次减小。通过减小被加工件厚度、增大搅拌头焊接速率和加快冷却速率等方法,抑制了试样搅拌区晶粒长大。在搅拌头转速和焊接速率分别为800r/min和90mm/min的条件下,得到的搅拌区底部平均晶粒尺寸约为450nm,该区域显微硬度为96HV,与普通钢制垫板制备的试样相比,硬度提高了24HV,其屈服强度、抗拉强度和伸长率分别提高为原材料的1.27倍、1.6倍和2.2倍。     

基于CFD数值仿真技术的飞行器动导数计算

为了研究表征飞行器动态稳定特性的动导数,结合计算流体力学方法,基于滑移网格技术,采用小幅度强迫振动法和差分法两种非定常方法,推导了俯仰组合动导数以及滚转阻尼导数的计算表达式,并结合多参考系模型采用准定常方法计算滚转阻尼导数。建立了基于计算流体力学技术的飞行器动导数计算方法。对国际动导数标模Finner导弹进行了计算验证。两种非定常方法对俯仰组合动导数的计算误差分别为0.65%、6.13%,对滚转阻尼导数的计算误差分别为2.5%、0.06%。求解滚转阻尼的准定常方法对于滚转阻尼导数的计算误差为2.67%。三种方法的计算结果与风洞试验结果吻合的很好。非定常方法计算精度高,准定常方法可以快捷迅速得到结果。本文的数值方法不仅适用于超声速,同样可以用于亚、跨声速时的动导数计算。     

固冲发动机补燃室非稳态沉积过程分析

采用随机轨道模型,基于动网格技术,分析了固冲发动机补燃室非稳态沉积过程中燃气流动边界形状变化对燃气流动及沉积分布的影响,得到了补燃室内壁面的非稳态沉积规律,对直连试验中出现的进气道出口拐角烧蚀沟槽现象进行了理论分析。研究发现,不同粒径的粒子在补燃室内的分布特性差异较大;凸起的沉积块可改变燃气流向,使进气道出口拐角处的高温区变大,易形成沟槽;点火初期,掺混区进气道之间的沉积速率较大。