飞行性能仿真中风场模型的研究

为提高飞机飞行动力学系统的仿真逼真度,本文根据实际飞行中的风场类型.重点对影响飞行性能的微下冲气流及大气紊流进行深入研究,提出两种风场的数学模型.其中重点介绍了时不能直接用于仿真模拟的von Kaman大气紊流模型进行有理化处理,改变了以前基于Dryden模型的建模方法.得出逼近于Von Karman模型的新的紊流模型.确定新的滤波器参数,从而在时域内实时生成大气紊流.通过频域上的分析比较和时域的仿真计算.结果表明该模型生成的紊流比以往的Dryden模型更好地符合了大气数理统计特性,并解决了von Karnlan的仿真实现问题.该文的数值模拟算法可直接应用于模拟器的空气动力学运动方程,从而使飞机在风场中的模拟更加真实,对模拟器的研制具有实际意义.     

飞行仿真系统中三维大气紊流模型仿真研究

为提高飞机飞行动力学系统的仿真逼真度,提出1种新的大气紊流模型,并研究出在实时飞行仿真系统中的实现技术。改变了以前基于Dryden模型的建模方法,对不能直接用于仿真模拟的Von．Karman大气紊流模型进行有理化处理,得出逼近于Von．Karman模型的新的紊流模型,确定新的滤波器参数,从而在时域内实时生成大气紊流。通过频域上的分析比较,结果表明该模型生成的紊流比以往的Dryden模型更好地符合了大气数理统计特性,并解决了Von．Karman的仿真实现问题。最后,将提出的数值模拟算法直接应用于某型飞机飞行仿真系统中,从而使飞机在风场中的模拟更加真实,对模拟器的研制具有实际意义。     

基于Von Karman模型的三维大气紊流仿真

为提高飞机飞行动力学系统的仿真逼真度，提出一种新的大气紊流模型，并研究出在实时仿真中的实现技术。改变以前基于Dryden模型的建模方法。对不能直接用于仿真模拟的Von Karman大气紊流模型进行有理化处理，得出逼近于Von Karman模型的新的紊流模型，确定新的滤波器参数，从而在时域内实时生成大气紊流。通过频域上的分析比较和时域的仿真计算。结果表明该模型生成的紊流比以往的Dryden模型更好地符合了大气数理统计特性，并解决了Von Karman的仿真实现问题。数值模拟算法可直接应用于模拟器的空气动力学运动方程，从而使飞机在风场中的模拟更加真实。对模拟器的研制具有实际意义。     

基于Frenet标架下三维元胞自动机的航母舰载机集群运动建模

航母舰载机运动包括二维甲板上的运动和三维空域内的运动.二维甲板面易受海面复杂扰动而发生运动,三维空域涉及区域又非常大,这使得实现航母舰载机集群运动建模成为一项具有挑战性的问题.目前国内外公开的研究工作很少有涉及舰载机集群运动的,可以借鉴的关于飞行器集群方面工作中又很少有涉及整个飞行空域内集群运动的模拟.针对上述问题,提出了一种基于Frenet活动标架下的三维元胞自动机模型来实现舰载机集群运动模拟,通过沿舰载机预定航线轨迹构建Frenet活动标架,基于该标架进行元胞剖分并采用三维元胞自动机模型建模求解整个空域内舰载机之间的运动,最终实现整个空域内舰载机集群运动的模拟.在PS机上基于各种虚拟数据集对舰载机的运动进行实验模拟,结果表明,文中方法可以较好地模拟舰载机在多种环境下的起降以及巡航行为,并且针对5 km的航线,可以实时计算模拟约8万架次舰载机的运动状态.     

大气紊流影响下飞艇水平面内运动分析

大气扰动是影响高空飞艇水平面内运动的重要原因.研究紊流风速对飞艇飞行性能的影响时,大都采用Taylor冻结场假设,但这样建立的紊流风场模型,不适用于飞艇这类低动态飞行器,需要考虑时间变化对紊流风速的影响.首先给出大气紊流的一般性描述,包括相关函数、频谱函数、尺度和强度的选取,然后建立含扰动风参数的水平面内飞艇动力学仿真模型.最后分别将不考虑时间变化的扰动风和考虑时间变化的扰动风加到飞艇动力学模型上,进行仿真分析.仿真结果表明,考虑时间变化后的紊流风速模型能真实反映飞艇对大气紊流响应的随机特性.     

某型航母舰载机机库内调运方法设计

航母机库是存放、检修维护舰载机和进行飞行前准备工作的重要场所。舰载机在机库内的调运效率直接影响其出动率,因此需要结合调运小组和各调运设备,设计合理的方法来保证调运流程的顺利进行。本文分析国外某型航母舰载机机库内调运流程,将其划为5个阶段,并参考操作系统中进程调度的概念,使用短进程优先的方法设计出2种调运方法,并对这2种方法进行了分析。     

基于FPGA的大气紊流模拟器设计

为了克服在利用软件模拟大气紊流的过程中所遇到的软件兼容性差和数据传输不方便等缺点,采用FPGA技术,设计了大气紊流模拟器。模拟器以大气紊流Dryden模型为理论基础,将Box-Muller算法与LFSR方法结合,利用Quartus II软件设计了Gauss白噪声生成模块,并利用Dsp builder设计的成形滤波器将Gauss白噪声滤波,从而产生大气紊流信号。通过串口将大气紊流信号实时进行传输。通过使用模拟器进行多次模拟实验,利用Labview和Matlab软件接收模拟器模拟数据并进行分析,发现产生的大气紊流信号符合Dryden模型的相关函数特性,可以模拟各种状态的大气紊流环境,符合设计要求。该模拟器具有使用方便、实时性较高等特点,可以用于单个飞行器飞行环境模拟,具有很高的实用价值。     

考虑舰面纵摇的舰载机弹射起飞动力学分析

针对舰面纵摇运动对舰载机弹射起飞过程影响较大的问题,根据舰面纵摇特性建立舰载机弹射起飞动力学模型;分析计算不同纵摇初始相位角对舰载机弹射起飞性能的影响.研究结果表明,舰面纵摇改变舰载机离舰时的速度、下沉量和攻角等.为保证飞行安全,需要确定安全弹射起飞的纵摇初始相位角的范围.     

大气扰动下无人机输出反馈控制律设计及仿真

针对无人机在飞行过程中容易受到大气环境干扰的问题,干扰主要来自外部扰动,主要研究了大气紊流对无人机飞行过程的影响,建立了基于Dryden模型的纵向小扰动线性运动方程.为抑制大气紊流对无人机运动的干扰,保证飞行过程中飞机的稳定性,应用输出反馈H∞控制算法设计了干扰抑制控制器进行仿真.仿真结果表明,采用的控制方法能够有效的抑制大气紊流对无人机运动的干扰,使飞控系统具有良好的稳定性和鲁棒性.     

舰载机着舰侧向回路的滚动时域控制

舰载机着舰问题是一个十分复杂的难题.由于航母的斜角甲板只有几十米宽,故而舰载机要降落在航母上需要十分精确的控制.在横测向控制中,最重要的是控制偏心距.为保持期望的着舰姿态,建立了舰载机横侧向着舰的非线性动力学模型,通过设定期望的着舰位置与姿态,将舰载机横侧向动力学模型的状态转化为误差状态,在攻角为11.7°,空速为70m/s的平衡点设计控制器,采用滚动时域预测控制来解决舰载机着舰的横侧向控制问题,用VC++构建三维仿真平台,在MATLAB上建立控制器模型,运用网络通信发送到三维仿真平台上,控制舰载机实现自动着舰.仿真结果表明滚动时域优化算法可以很好的实现舰载机着舰侧回路非线性系统的航迹跟踪与姿态跟踪.     

Divergence-Free Wavelet Analysis of Turbulent Flows

In this paper we study the application of divergence-free wavelet bases for the analysis of incompressible turbulent flows and perform several experiments. In particular, we analyze various nominally incompressible fields and study the influence of compressible perturbations due to experimental and computational errors. In addition, we investigate the multiscale structure of modes obtained from the Proper Orthogonal Decomposition (POD) method. Finally, we study the divergence-free wavelet compression of turbulent flow data and present results on the energy recovery. Moreover, we utilize wavelet decompositions to investigate the regularity of turbulent flow fields in certain non-classical function spaces, namely Besov spaces. In our experiments, we have observed significantly higher Besov regularity than Sobolev regularity, which indicates the potential for adaptive numerical simulations.     

Status and verification of edge plasma turbulence code BOUT

The BOUT code is a detailed numerical model of tokamak edge turbulence based on collisional plasma fluid equations. BOUT solves for time evolution of plasma fluid variables: plasma density Ni, parallel ion velocity V‖i, electron temperature Te, ion temperature Ti, electric potential ?, parallel current j_‖, and parallel vector potential A_‖, in realistic 3D divertor tokamak geometry. The current status of the code, physics model, algorithms, and implementation is described. Results of verification testing are presented along with illustrative applications to tokamak edge turbulence.     

A flux-coordinate independent field-aligned approach to plasma turbulence simulations

This work illustrates a new approach to field-aligned coordinates for plasma turbulence simulations which is not based on flux variables. The method employs standard Cartesian or polar coordinates to discretize the fields. Parallel derivatives are computed directly along a coordinate that follows the local field, and poloidal derivatives are computed in the original Cartesian frame. Several advantages of this approach are presented. The tests on a drift-wave model demonstrate that the method is well suited to exploit the flute property of small parallel gradients by minimizing the number of degrees of freedom needed to treat a given problem in an accurate and efficient manner.     

A novel numerical forcing for homogeneous stratified turbulence in full energy equilibrium

A new numerical method to simulate stationary, homogeneous, and stratified turbulence was developed with an arbitrary energy dissipation rate. Conventional numerical simulations for homogeneous stratified turbulence were accomplished by given mean shears and generated turbulence field either developed or decayed with time. In order to keep stationary turbulence, a linear forcing method for anisotropic turbulence was developed to apply stratified turbulence, where shear was calculated dynamically to satisfy the condition of energy equilibrium. The present method was implemented to direct numerical simulations to realize the generation of small-scale eddy fields, in which the Reynolds number based on the Taylor microscale was about 50. It was confirmed that simulated flow field successfully maintained energy equilibrium with keeping the given dissipation rate. The gradient and flux Richardson numbers determined by the balance of turbulence intensity and stratification were also found to be constant with time. As an application, diffusion of massless dye was numerically simulated in the reproduced turbulent field. The calculated vertical diffusivity was found to be well comparable with that of active heat estimated by a conventional model.     

垃圾焚烧余热锅炉汽包水位变形的三冲量串级调节

由于城市垃圾的组成极为复杂,不像一般燃煤的性质稳定。故在垃圾焚烧发电厂中,若余热锅炉汽包水位采用传统的三冲量控制方式,很难达到生产要求。所以在这次设计中我们重点对汽包水位的自动控制部分的程序进行了多次的改进,以达到调节的需要,解决假水位现象造成的锅筒水位急剧变化问题,同时减少燃料、负荷波动带来的锅筒水位波动,锅筒水位在正常时控制在±10cm以内,外部发生大波动时控制在±30cm以内,保持稳定连续补水过程,并能满足主阀故障时旁路阀的自动调节。     

Stencil Adaptation Properties of a WENO Scheme in Direct Numerical Simulations of Compressible Turbulence

Weighted essentially non-oscillatory (WENO) methods can simultaneously provide the high order of accuracy, high bandwidth-resolving efficiency, and shock-capturing capability required for the detailed simulation of compressible turbulence. However, rigorous analysis of the actual versus theoretical error properties of these non-linear numerical methods is difficult. We use a bandwidth-optimized WENO scheme to conduct direct numerical simulations of two- and three-dimensional decaying isotropic turbulence, and we evaluate the performance of quantitative indicators of local WENO adaptation behavior within the resulting flow fields. One aspect of this assessment is the demarcation of shock-containing and smooth regions where the WENO method should, respectively, engage its adaptation mechanism and revert to its linear optimal stencil. Our results show that these indicators, when synthesized properly, can provide valuable quantitative information suitable for statistical characterization.     

基于CPU/GPU异构系统架构的高超声速湍流直接数值模拟研究

【目的】高超声速湍流直接数值模拟(DNS)对空间及时间分辨率要求高,计算量非常大。过大的计算量及过长的计算时间是导致DNS难以在工程中被大范围应用的重要原因。为加快计算速度,作者设计并开发了一套CPU/GPU异构系统架构(HSA)下的高性能计算流体力学程序OpenCFD-SCU。【方法】该程序以作者前期开发的高精度有限差分求解器OpenCFD-SC为基础,经GPU系统的移植及优化而得。GPU程序的计算部分使用CUDA编程,确保所有算术运算都在GPU上完成。【结果】利用GPU程序OpenCFD-SCU,进行了来流Mach数6,6°攻角钝锥边界层转捩的直接数值模拟,得到了转捩过程中的时空演化流场。针对这一算例,GPU程序OpenCFD-SCU与CPU程序OpenCFD-SC相比,实现了60倍的加速效果(单GPU卡对单CPU核心),大大加速了DNS计算过程。【结论】未来,相信会有更多高超声速湍流模拟选择在GPU上开展。     

Particle-in-Cell Simulations with Kinetic Electrons

A new scheme, based on an exact separation between adiabatic and nonadiabatic electron responses, for particle-in-cell (PIC) simulations of drift-type modes is presented. The (linear and nonlinear) elliptic equations for the scalar fields are solved using a multigrid solver. The new scheme yields linear growth rates in excellent agreement with theory and it is shown to conserve energy well into the nonlinear regime. It is also demonstrated that simulations with few electrons are reliable and accurate, suggesting that large-scale, PIC simulations with electron dynamics in toroidal geometry (e.g., tokamaks and stellarators plasmas) are within reach of present-day massively-parallel supercomputers.     

大气紊流的数字仿真

为提高大气紊流数字模拟的精度,分析Dryden紊流模型的数字仿真技术,发现仿真中采用的高斯白噪声序列的生成精度是影响大气紊流模拟精度的重要因素.在不改变随机数序列均值、方差以及概率密度特性的情况下,采用双随机交换最小化方法对高斯噪声序列进行白化处理,使得随机数序列的白化程度提高,从而使紊流模拟的精度提高,而且模拟精度受采样间隔的影响降低.采用双随机交换最小化方法对高斯白噪声序列进行改进是提高紊流模拟精度的1种直接有效的手段.     

Simulation of anomalous transport in tokamaks using the FACETS code

The development of a new parallel framework for integrated modeling of tokamak plasmas is a primary objective of the SciDAC Framework Architecture for Core-Edge Transport Simulations (FACETS) project. The FACETS code will be used to predict the performance of tokamak discharges and to optimize tokamak discharge scenarios. Novel parallel numerical algorithms and solvers have been developed in the FACETS project in order to simulate the multi-scale dynamics of tokamak plasmas. The status of development of modules for anomalous transport in the FACETS code is described in this paper. Mechanisms that are used for coupling 1D anomalous transport in the plasma core together with 2D transport in the plasma edge (in near separatrix and scrape-off-layer regions) are considered. Results of the first verification studies based on predictive modeling of several analytical and experimental equilibria are presented.