求解飞机蒙皮耦合热效应的壁面热流函数法

分析了飞机内部换热与蒙皮外辐射换热和气动换热的耦合作用,提出了一种求解飞机内外耦合热效应的工程计算方法。通过构造反映蒙皮外辐射换热和气动换热的壁面热流函数,将蒙皮外热环境转化为浮动的热边界条件,实现了飞机蒙皮外部热环境求解与蒙皮内换热求解的解耦处理,避免了难以实现的直接耦合求解。在验证该方法可靠性的基础上, 采用该方法,并结合热网络法与FLUENT软件对某型飞机外部热环境及结构热响应问题进行了计算。     

红外窗口辐射导热耦合换热研究

针对高速飞行器典型红外窗口材料及气动加热外部热环境特点,建立红外窗口辐射导热耦合换热模型,采用光线跟踪法及有限差分法研究了红外窗口内部温度分布。考察了材料的物性、热边界条件等因素对温度分布的影响。研究结果表明,壁面对流换热系数、光谱吸收系数对红外窗口内部温度分布影响很大。     

有内部热源的非稳态导热与自然对流换热及辐辐射换热耦合问题研究

采用大型通用计算程序ＰＨＯＥＮＩＣＳ（１．４版本）、并结合虚拟密度法,对有内部热的非稳态导热与自然对流换热及辐射换热的耦合问题进行了数值求解。分析和比较了在直角坐标和贴体价值下得到的速度场及温度场及温度场的数值模拟结果,并示出了在两种坐标下发热物质内部靠近中心处的最高温度阴时间的变化趋势。     

微细多孔介质中对流换热研究

本文对空气、氦气和二氧化碳流过微细多孔介质内部的对流换热进行了实验研究和数值模拟。实验段为烧结多孔介质,颗粒的平均直径为40～225μm,通过单吹法的实验方法进行瞬态实验,得到了多孔介质内部对流换热系数。数值模拟了气体流过微细多孔结构内部的对流换热的非稳态过程,得到多孔介质内部对流换热系数。数值结果与实验结果基本一致,并与已有结果基本吻合。     

基于Kriging代理模型的飞行器结构刚度气动优化设计

大飞机具有轻质大柔性特点,使得气动/结构耦合作用增强,在设计过程中需要考虑这种耦合效应,直接调用CSD/CFD方法计算周期长,无法满足工程需要.代理模型方法由于能显著提高工程优化设计的效率,已广泛应用于飞行器气动外形优化设计中.采用Kriging方法建立代理模型,通过求解EI函数最大值得到需添加的样本点以更新代理模型,提高代理模型的拟合精度,结合改进的粒子群最优化方法对大飞机的结构刚度进行了优化设计.结果表明,该优化方法能够处理复杂目标的全局优化问题,在保证升力系数及纵向稳定性能不恶化的前提下,降低飞机巡航状态的飞行阻力.      

多孔介质中超临界C O2对流换热数值模拟

本文对超临界二氧化碳在多孔结构中的对流换热进行了数值模拟研究.结果表明,超临界条件下二氧化碳剧烈的变物性对多孔介质中的对流换热会产生很大影响;局部热平衡条件下对流换热系数的数值计算值比局部非热平衡条件下的计算结果大;对流换热系数随着颗粒直径的增大而增大.     

无尾升力式飞行器Weissman判据图仿真

针对无尾升力式飞行器横航向气动耦合严重的问题,开展了Weissman判据在此类飞行器稳定性设计中的应用研究.采用调整布局的方法获得飞行器布局集,采用基于Newton理论的工程方法获得对应的气动数据集.运用飞行动力学仿真手段分析了飞行器在无控和副翼控制时的横航向飞行稳定性.结合仿真结果和Weissman判据分区规则获得飞行器Weissman判据图.研究表明,无尾升力式飞行器的关键设计点气动稳定性位于Weissman判据图的B区.文章的方法可用于再入机动飞行器的耦合稳定性设计.      

离子风强化平板对流传热的数值模拟

本文应用多物理场耦合计算软件COMSOL对离子风作用下强化平板对流换热的过程进行了数值模拟.研究了空气在高压电场下的对流换热现象,得到线-板电极模型相应的流场和温度场分布,并与文献中的实验结果进行了对比,验证了多物理场耦合数值方法的准确性。通过研究不同电压下传统风扇风冷、离子风和离子风与风扇共同作用下的对流换热系数变化规律,发现空气放电强化传热较传统方式有明显优势。还研究了不同极板距与板长比和不同板长情况下对流换热系数的变化规律.     

飞行器大攻角非定常气动特性神经网络建模

大攻角气动特性预测与气动建模是新型飞行器提升飞行性能的重要内容.以轴对称导弹简化模型为研究对象，首先采用计算流体力学方法，对70°大攻角状态的非定常气动特性进行数值模拟，计算方法基于RANS的N-S方程，湍流模型采用SA模型，对流场采用有限体积法离散，无黏项采用Roe通量差分分裂格式，黏性项采用中心差分，时间推进采用LU-SGS格式的双时间步法.飞行器运动模式采用强迫振荡的方式，对5种不同振荡频率进行了非定常数值计算，并记录每一内迭代周期最终的气动力和力矩数值.其次，以CFD预测结果作为气动建模的样本，采用动导数模型、多项式模型等传统方法，进行气动建模，并分析其有效性和精度.最后采用神经网络方法对大攻角非定常气动力进行建模，并和动导数模型、多项式模型进行精度对比.结果表明，基于神经网络的人工智能气动建模方法具有较高的精度和适应性.该方法为飞行器大攻角非定常非线性气动建模，大攻角飞行稳定性分析与控制提供理论参考.      

水平板自然对流换热的非线性特性

采用SIMPLE算法,QUICK差分方案,对封闭方腔内水平板自然对流换热进行了数值模拟.数值结果显示,低Ra数时流动和换热处于稳态,当Rayleigh数超过某一临界值时,流动和换热就会发生非稳态振荡,此时流动和换热表现出非对称性.对不同Rayleigh数,流动和换热通过单周期分岔从稳态过渡到非稳态,并通过倍周期分岔过渡到混沌.在混沌区,仍然会出现周期性窗口,并且数值结果与初始条件有关.     

类前缘防热层流场与热响应耦合计算研究

本文在以往对类前缘防热层热响应计算分析基础上,进一步研究实现了外流场高超音速NS方程数值计算表面气动加热与防热层结构热响应的耦合计算,这对于常用的非耦合计算方法来说是一进步,也为进一步开展外流场/结构热响应/热应力全耦合一体化计算研究和防热层表面吹气强化传热问题的场协同研究打下了基础。     

空温式翅片管气化器非稳态结霜速率分析

观测了某实际运营的空温式翅片管气化器附近湿空气流动状态。基于热力学理论和湿空气流动状态建立了空温式翅片管气化器表面非稳态结霜模型,推导了非稳态结霜速率的关系式,分析了不同工况下非稳态结霜速率影响因素。非稳态结霜速率随湿空气温度、相对湿度和气流速度增加而增加,其主要影响因素为湿空气温度和相对湿度,而气流速度影响相对较小。非稳态结霜速率分析为精确计算空温式翅片管气化器传热特性提供了一定理论依据。     

低温试验冷库传热系数的测量研究

简述了对于低温冷库传热系数测量所采用的一般方法,采用稳态法对一低温试验冷库进行了测量实验,然后通过非稳态积分法对试验数据进行验证。针对冷风机电机功率较大的特点,本实验采用变频器将电机功率调小,从而成功得出该低温试验冷库的传热系数。并与理论计算的数据进行对比,找出存在差别的原因。     

高超声速飞行器前缘流固耦合计算方法研究

对高超声速流场和结构温度场进行了耦合计算分析, 同时基于准静态假设对结构应力进行了分析. 流场部分采用基于非定常Navier-Stokes (N-S)方程的有限体积法, 湍流模型采用SST k-ω 模型, 固体部分采用基于非稳态热传导方程的有限元法, 同时基于准静态假设对固体结构的应力应变进行了分析. 在流固交界面处, 高速流体从固体结构得到温度边界条件, 固体结构从高速流体得到热流边界条件, 从而实现了流场和固体温度场的紧耦合计算.通过与超声速无限长圆管绕流试验结果进行对比, 验证了该方法的可靠性. 同时对二维圆管结构在气动加热过程中的温度、应力等的变化进行了比较详细的分析. 研究结果表明: 随着气动加热时间的推进, 由于圆管结构的高温区在不断扩大, 导致了结构的热变形在不断地增大; 圆管最小变形区出现在θ为60°处; 同时研究发现在计算时间内圆管热变形对外部流场的影响可以忽略不计.     

非定常激波对气膜冷却影响的数值模拟

利用数值计算的方法研究了非定常激波对下游涡轮叶片表面气膜冷却的影响.冷却气流在激波和尾迹经过的过程中,发生了上扬和重新被压制回壁面的现象.考察了壁面上特定点在有气膜和无气膜情况下的换热量.通过计算发现,有气膜时的换热量有不同程度的下降,而且换热量随时间变化的趋势也发生了很大的变化.气膜的覆盖减小了主流场对壁面换热量的影响.     

The equation of state of quarks and mesons in a renormalization group flow picture

Non-perturbative flow equations within an effective linear sigma model coupled to constituent quarks for two quark flavours are derived and solved. A heat kernel regularization is employed for a renormalization group improved effective potential. We determine the initial values of the coupling constants in the effective potential at zero temperature. Solving the evolution equations with the same initial values at finite temperature in the chiral limit, we find a second-order phase transition at T_c≈150 MeV. Due to the smooth decoupling of massive modes, we can directly link the low-temperature four-dimensional theory to the three-dimensional high-temperature theory. We calculate the equation of state in the chiral limit and for finite pion masses and determine universal critical exponents.     

Prediction of Liner Metal Temperature of an Aeroengine Combustor with Multi-Physics Scale-Resolving CFD

Computational Fluid Dynamics is a fundamental tool to simulate the flow field and the multi-physics nature of the phenomena involved in gas turbine combustors, supporting their design since the very preliminary phases. Standard steady state RANS turbulence models provide a reasonable prediction, despite some well-known limitations in reproducing the turbulent mixing in highly unsteady flows. Their affordable cost is ideal in the preliminary design steps, whereas, in the detailed phase of the design process, turbulence scale-resolving methods (such as LES or similar approaches) can be preferred to significantly improve the accuracy. Despite that, in dealing with multi-physics and multi-scale problems, as for Conjugate Heat Transfer (CHT) in presence of radiation, transient approaches are not always affordable and appropriate numerical treatments are necessary to properly account for the huge range of characteristics scales in space and time that occur when turbulence is resolved and heat conduction is simulated contextually. The present work describes an innovative methodology to perform CHT simulations accounting for multi-physics and multi-scale problems. Such methodology, named U-THERM3D, is applied for the metal temperature prediction of an annular aeroengine lean burn combustor. The theoretical formulations of the tool are described, together with its numerical implementation in the commercial CFD code ANSYS Fluent. The proposed approach is based on a time de-synchronization of the involved time dependent physics permitting to significantly speed up the calculation with respect to fully coupled strategy, preserving at the same time the effect of unsteady heat transfer on the final time averaged predicted metal temperature. The results of some preliminary assessment tests of its consistency and accuracy are reported before showing its exploitation on the real combustor. The results are compared against steady-state calculations and experimental data obtained by full annular tests at real scale conditions. The work confirms the importance of high-fidelity CFD approaches for the aerothermal prediction of liner metal temperature.     

The momentum interpolation method based on the time-marching algorithm for All-Speed flows

The time-marching approach has clear physical meaning and strict mathematical nature and has been applied in computation of compressible flows widely and extended to many uniform algorithms for All-Speed flows. Remedy for its weakness in the problem of checkerboard decoupling of pressure field for incompressible flows is envisaged with the time-marching momentum interpolation method (MIM) taken into account in this paper. Existing preconditioning methods for suppressing decoupling and time-marching MIM are analyzed for this purpose, and algorithms of time-marching MIM are proposed for steady and unsteady flows and for All-Speed flows. Asymptotic analysis shows that the supposed time-marching MIM has at least a third-order accuracy, better than the existing time-marching coupling methods, which only have an accuracy of the same order as the adopted scheme has. Effects of the time step sizes on the ability of the time-marching MIM to suppress the checkerboard pressure decoupling are particularly discussed in terms of the dual-time stepping approach, and it is revealed how the decreased sizes of either the pseudo- or physical-time step increases the possibility of decoupling and how Choi’s modification, in which the history of the interface velocity is decided by itself instead of the arithmetic average of the velocities on its adjacent nodes, removes the unphysical pressure oscillation with small size of the physical time step but leads to divergence with the pseudo-time step as well. As a remedy for the pseudo-time step, such methods are recommended as implicit methods and the local-time step method with a proposed modification of the time-marching MIM preventing accuracy loss due to very large time step size. Numerical experiments support the theoretical analyses and show the validity of the time-marching MIM proposed.     

气动加热下高温陶瓷材料内的瞬态耦合换热

采用控制容积法结合蒙特卡罗法与谱带模型,数值模拟了气动加热下高温陶瓷内的辐射与导热瞬态耦合换热.分析了冷却边界条件、各向同性散射和表面特性对高温陶瓷内瞬态温度分布的影响.结果表明,高温下陶瓷内的辐射换热作用十分明显,陶瓷材料的表面特性对瞬态温度分布影响很大,各向同性散射也有明显影响.     

A high-efficiency aerothermoelastic analysis method

In this paper,a high-efficiency aerothermoelastic analysis method based on unified hypersonic lifting surface theory is established.The method adopts a two-way coupling form that couples the structure,aerodynamic force,and aerodynamic thermo and heat conduction.The aerodynamic force is first calculated based on unified hypersonic lifting surface theory,and then the Eckert reference temperature method is used to solve the temperature field,where the transient heat conduction is solved using Fourier’s law,and the modal method is used for the aeroelastic correction.Finally,flutter is analyzed based on the p-k method.The aerothermoelastic behavior of a typical hypersonic low-aspect ratio wing is then analyzed,and the results indicate the following:(1)the combined effects of the aerodynamic load and thermal load both deform the wing,which would increase if the flexibility,size,and flight time of the hypersonic aircraft increase;(2)the effect of heat accumulation should be noted,and therefore,the trajectory parameters should be considered in the design of hypersonic flight vehicles to avoid hazardous conditions,such as flutter.