Korteweg-De Vries-Burgers方程的级数解

本文给出了KdV-Burgers方程行波解的如下边值问题: d²u/(dz²)-Am(du)/(dz)+u²-u=0, u(-∞)=1,u(+∞)=0的级数解.求解的方法是把整个解分解成三个区域的级数解,然后利用对接条件(函数和导数连续)构成一个整体级数解.与精确解的比较表明,精度可达到任意位小数.对方程中的参数A_m的任意值均可给出相应的级数解.特别对A_m<2的情况,第一次给出了振荡型激波的级数解.     

弱激波冲击无膜重气柱和气帘界面的实验研究

研制了一个改进的激波管设备,对马赫数为1.2的弱激波冲击作用下空气中SF6气柱和气帘界面的演变过程进行了初步的实验研究。通过设计激波管实验段、烟雾发生器、气体箱、进气吸气系统和激波管尾段,控制混合气体中SF6的峰值浓度和初始气流速度,建立了稳定、可重复的无膜气柱和气帘初始界面形成技术。利用高速摄影技术,在水平面内观测了气柱和气帘的初始界面图像,沿垂直方向观测了界面RM(Richtmyer-Meshkov)不稳定性的演变过程。气柱演变图像显示了典型的对涡结构,气帘演变图像显示了早期的多蘑菇形结构和后期的相邻波长干扰效应。图像后处理表明,气柱的高度和宽度、气帘的宽度均随时间单调增加,且宽度比高度增加快得多。从二维涡量动力学方程出发,对图像中涡的演变过程进行了初步解释。     

高速流场对光传输特性的影响

利用一座小型跨超声速风洞进行了高速流场光传输特性试验研究。光束在高速流场中传输时,由于流场密度变化,光波波前会发生畸变。利用风洞提供0.7,2.0和3.0等气流马赫数的流场条件,采用基于夏克-哈特曼波前传感器的光学测量系统,对光束在风洞流场中传输时的波前畸变进行了测量。试验结果表明:随着风洞流场马赫数增加,流场对光波传播的影响增大,光波波前畸变量显著提高。因此,在利用风洞进行气动光学试验研究之前,有必要消除风洞流场本身对光波传输的严重干扰。     

高超声速风洞短时气动力智能辨识算法研究

风洞测力试验是高超声速飞行器研发的重要环节,随着这项技术的发展,试验模型的大尺度化成为高超声速风洞试验的趋势.在几百毫秒的有效测试时间内,大尺度测力系统刚度减弱等问题会严重导致气动力辨识精度变差,试验模型大尺度化对短时脉冲燃烧风洞精确气动力辨识带来了挑战.对此本文提出了一种新的基于传统信号处理结合深度学习的智能气动力辨...     

一类二维单个守恒律方程的Riemann问题

本文研究一类二维单个守恒律方程的Riemann问题.用广义特征分析方法研究了这类方程,给出了基本波的分类,解决了初值为两片常数的二维Riemann问题,给出了Riemann解.     

第14届亚洲物理奥林匹克竞赛实验试题与中国队学生实验能力分析

介绍了第14届亚洲物理奥林匹克竞赛实验试题,并针对参赛学生在竞赛中的失分情况分析了竞赛评分规则,指出了实验数据处理方法中的重点和存在的问题。     

煤油裂解产物/空气与煤油/空气在宽温度范围内点火延迟的对比研究

Kerosene is an ideal endothermic hydrocarbon. Its pyrolysis plays a significant role in the thermal protection for high-speed aircraft. Before it reacts, kerosene experiences thermal decomposition in the heat exchanger and produces cracked products. Thus, to use cracked kerosene instead of pure kerosene, knowledge of their ignition properties is needed. In this study, ignition delay times of cracked kerosene/air and kerosene/air were measured in a heated shock tube at temperatures of 657–1333 K, an equivalence ratio of 1.0, and pressures of 1.01 × 10⁵–10.10 × 10⁵ Pa. Ignition delay time was defined as the time interval between the arrival of the reflected shock and the occurrence of the steepest rise of excited-state CH species (CH*) emission at the sidewall measurement location. Pure helium was used as the driver gas for high-temperature measurements in which test times needed to be shorter than 1.5 ms, and tailored mixtures of He/Ar were used when test times could reach up to 15 ms. Arrhenius-type formulas for the relationship between ignition delay time and ignition conditions (temperature and pressure) were obtained by correlating the measured high-temperature data of both fuels. The results reveal that the ignition delay times of both fuels are close, and an increase in the pressure or temperature causes a decrease in the ignition delay time in the high-temperature region (> 1000 K). Both fuels exhibit similar high-temperature ignition delay properties, because they have close pressure exponents (cracked kerosene: τ_ign∝P^-0.85; kerosene:τ_ign∝P^-0.83) and global activation energies (cracked kerosene: E_a = 143.37 kJ·mol^-1; kerosene: E_a = 144.29 kJ·mol^-1). However, in the low-temperature region (< 1000 K), ignition delay characteristics are quite different. For cracked kerosene/air, while the decrease in the temperature still results in an increase in the ignition delay time, the negative temperature coefficient (NTC) of ignition delay does not occur, and the low-temperature ignition data still can be correlated by an Arrhenius-type formula with a much smaller global activation energy compared to that at high temperatures. However, for kerosene/air, this NTC phenomenon was observed, and the Arrhenius-type formula fails to correlate its low-temperature ignition data. At temperatures ranging from 830 to 1000 K, the cracked kerosene ignites faster than the kerosene; at temperatures below 830 K, kerosene ignition delay times become much shorter than those of cracked kerosene. Surrogates for cracked kerosene and kerosene are proposed based on the H/C ratio and average molecular weight in order to simulate ignition delay times for cracked kerosene/air and kerosene/air. The simulation results are in fairly good agreement with current experimental data for the two fuels at high temperatures (> 1000 K). However, in the low-temperature NTC region, the results are in very good agreement with kerosene ignition delay data but disagree with cracked kerosene ignition delay data. The comparison between experimental data and model predictions indicates that refinement of the reaction mechanisms for cracked kerosene and kerosene is needed. These test results are helpful to understand ignition properties of cracked kerosene in developing regenerative cooling technology for high-speed aircraft.     

跨音速轴流风扇转子叶顶泄漏流的数值研究

采用数值模拟方法研究了不同间隙,不同流量工况下叶顶泄漏流非定常流动特征,发现在研究的三个间隙中,只有当间隙大于或等于设计间隙时,流动才会出现非定常性.随着流量的减小,泄漏涡轨迹前移,当泄漏涡轨迹到达相邻叶片压力面时,影响压力面压力分布,打破流场静态平衡,引起叶顶流场及激波位置、强度发生非定常波动.