共查询到20条相似文献,搜索用时 101 毫秒
1.
本文采用四阶精度紧密格式研究了壁面冷却和抽吸对超声速高超声速旋转圆锥三维边界层横流不稳定性的影响,最大M=7.5。数值结果证明:壁面冷却和抽吸对第一模式有稳定作用,但这一作用比二维边界层显著减弱,抽吸使第二模式增长率减小,冷却使第二模式增长率增大,不稳定频率升高;直到M=7.5可以用壁面抽吸使得因为壁面冷却而变得更不稳定的第二模式重新趋于稳定,但M数越高所需的抽吸量越大。 相似文献
2.
本文的研究目的是了解沿圆管内发展的高超声速流的结构。实验是在加拿大多伦多大学的高超声速炮风洞内完成的,风洞的自由射流马赫数M_∞=8.30,总温T_(t∞)=1000K,总压P_(t∞)=26.5MPa单位雷诺数R_e=3.2×l0 ̄7。壁面静压以及内流中的若干截面内的皮托压力和静压测量结果揭示,管内产生的激波主要是斜激波形态,而且存在着较强的激波与边界层的相互干扰。实验发现,近管中心线的高超声速流动有不稳定现象;壁面的边界层,基本上是湍流边界层,特别是干扰区的下游;圆管出口的周向内壁面的顶壁面静压对管的攻角异常敏感。本文提供的结果,可以指导高超声速流的计算流体力学的方法和进展。 相似文献
3.
本文给出M_∞=7.8和6.72,Re=3.5×10 ̄7/m和5.4×10 ̄7/m气流绕迎角为20°、30°和35°尖前缘翼运动时,平板锥型干扰区的壁面压力和热流率分布。结果表明:(1)平板锥型干扰区的特征几何尺度与无粘激波角β_0和翼迎角α相关,而壁面压力和热流率的峰值与法向马赫数M_n相关。(2)翼面压力和热流率分布由于受拐角涡影响,前者在翼根部呈波谷状,而后者呈波峰状,影响尺度与翼前缘处来流边界层厚度有关。 相似文献
4.
5.
壁面温度控制对平板边界层影响的数值研究 总被引:2,自引:0,他引:2
通过对零压力梯度的平板边界层流动施加温度控制,展开壁面温度控制对平板层流边界层和湍流边界层影响的研究,探索温度控制对平板转捩雷诺数和壁面摩擦阻力的影响规律。采用带有转捩模式的三方程湍流模型对平板边界层流动进行数值模拟,重点考察了壁面摩阻系数、平板转捩雷诺数、湍流边界层流动随壁面温度变化的规律。计算结果表明在壁面温度从288 K 增大到432 K 时,边界层转捩雷诺数增大约36%,表面摩擦阻力减少约9.6%。研究分析表明:加热控制使层流区域温度边界层内粘性作用增强,雷诺切应力和湍动能减小,流动更加稳定;而湍流区域边界层内粘性底层中速度梯度和粘性切应力减小,导致壁面处摩擦切应力减小。因此壁面加热控制可以延迟边界层转捩,减小湍流区摩阻系数,并减小平板摩擦阻力。 相似文献
6.
钝缘舵高超音速湍流分离特性 总被引:1,自引:0,他引:1
给出由半圆柱前缘舵诱导的高超音速湍流分离的实验结果。实验气流Mach数为7.8,单位长度Re数为3.5×107m-1。结果表明:钝缘舵诱导的湍流分离极不稳定,分离激波出现大尺度低频振荡,使壁面压力和热流率无量纲标准偏差在主分离线附近达最大值。Mach数愈高,最大无量纲标准偏差值越大。在前缘区前缘直径是控制分离流场尺度和平均壁面压力、热流率分布的主要参数 相似文献
7.
本文在M∞=1.58及湍流边界层厚度δ/D=0.1条件下,用实验方法研究了管长L/D=6方管内的三维超声波湍流场及其沿程的发展和反压的影响,讨论了壁面边界层沿流向和展向的主要变化特征;指出管内横截面的三维静压场特点,文中最后探讨了超声速湍流流动的方管内旋涡的测量技术。 相似文献
8.
为了进一步优化压气机的整体性能,提出三种叶片开缝和边界层抽吸的耦合流动控制方案。首先,利用数值模拟的方法,研究叶片开缝或边界层抽吸对跨声速轴流压气机流场结构的影响机理。然后,详细研究了边界层抽吸分别与三种不同叶片开缝的耦合流动控制方案对压气机整体性能的影响。研究结果表明,与叶片开缝或边界层抽吸的单独应用相比,三种耦合流动控制方案都使压气机实现了更宽的稳定裕度。全叶片开缝与边界层抽吸的耦合方案稳定裕度改进量为1.27%,中间叶高开缝的耦合方案和上半叶高开缝的耦合方案稳定裕度改进量分别为1.67%和1.35%;在近失速点处,相比较全叶片开缝与边界层抽吸的耦合方案,局部开缝与边界层抽吸的耦合方案应用后,总压损失和效率降低;上半叶高开缝的耦合方案在三种耦合方案中稳定裕度最高,所以叶片开缝和边界层抽吸的耦合方案是可行的。 相似文献
9.
10.
11.
差值法与比值法对不同测量系统的误差修正效果不一样。本文将两种方法的比较用一个比值来描述,并用推得的公式进行量化表示。在进一步的应用研究中,理论分析与实验数据相互印证,同时得到许多有益的结论,有助于全面掌握测量系统的误差来源,从而灵活选择各种修正方法以获得更加准确的测量结果。 相似文献
12.
李稷 《民用飞机设计与研究》2010,(4):33-36,41
飞控系统主作动器电子控制装置(P-ACE)是现代电传飞控系统的核心部件。飞控系统主作动器电子控制装置仿真器采用数字仿真模块扩展模拟电路接口的仿真技术,具有与真件功能相似、接口相同的特性,可以代替飞控系统主作动器电子控制装置真件,参与飞控系统的调试和试验,对研究飞控系统的功能和性能具有重要意义。 相似文献
13.
14.
15.
Now extinct short-lived radioactive isotopes were apparently extant in the early solar system. Their abundances can be inferred
from isotopic effects in their daughter nuclei in primitive meteorites, and the deviation of these abundances from expectations
from continuous galactic nucleosynthesis yields important information on the last nucleosynthetic events that contributed
new nuclei to the solar system and on the general circumstances of the Sun's birth. In this paper we present a rudimentary
model that attempts to reconcile the abundances of ten short-lived radioactivities in the early solar system. In broad outlines,
the picture requires 1) that Type Ia supernovae maintained a steady ISM supply of 53Mn and 146Sm, 2) that the r-process events that slowly admixed new 107Pd, 129I, 182Hf, and 244Pu nuclei to the solar system occurred over an interval of several hundred million years prior to solar system formation,
and 3) that a massive star, by injecting only material outside its helium-exhausted core into the proto-solar nebula, contributed
26Al, 36Cl, 41Ca, 60Fe, and 182Hf no more than one million years prior to the Sun's birth. In this picture, the live 182Hf present in the early solar system was not due to r-process production but rather to a fast s-process in helium or carbon
burning shell in the massive star. We conclude with a possible chemical-memory explanation for the putative 53Cr/52Cr gradient in the solar system.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
K. B. Panfilovich 《Russian Aeronautics (Iz VUZ)》2014,57(1):71-74
In this paper, a physical model of gas flows through the channels is refined. The influence of gas absorbed by the walls of a channel on its conductance is shown. The experimentally obtained minimum on the channel conductance-pressure dependence (as the Knudsen paradox) is interpreted. 相似文献
17.
In this paper, we consider the concept of the impact of an action or human error. We begin from an informal definition of impact as: the effect that an action or sequence of actions has on the safe and successful operation of a system; and develop a quantitative measure of the impact of specified behaviours. It is important that human-machine interface designers should understand the relationship between operator actions and the hazards associated with a system. We demonstrate how impact can be assessed prior to, or in parallel with, the design of the human-machine interface, and show how impact assessments could be used to allow risk analysts to inform designers about the relationship between operator actions and system hazards. To illustrate our approach we present a simple case study, 相似文献
18.
Donald D. Clayton 《Space Science Reviews》1979,24(2):147-226
This review concentrates on recent ideas involving a relationship between the early solar system and supernova explosions. It summarizes briefly the data that has helped inspire those ideas. Because the true relationship is still unknown and generates controversy, the distinct ideas are introduced singly in the historical context of their origins, and the active sense of surprise and controversy is visible. Quotations from pivotal papers are used as part of the exposition. The subject involves equally the isotopic anomalies detected in meteorites and the dynamic events of galactic evolution, nucleosynthesis, and protosolar collapse. Whatever the correct situation is, new connections have been found between the origin of the elements and the formation of the solar system. The objective of this review is to enable interested space scientists to quickly identify the competing points of view and the experiments and theories that have led to them. 相似文献
19.
20.
吸尘器振动与噪声试验分析 总被引:1,自引:0,他引:1
针对某型号吸尘器噪音和振动大的问题进行试验研究,用声强法对吸尘器的噪音进行测量分析,同时对吸尘器的振动进行了测量并对振动信号用DASP软件进行了频谱分析,识别了吸尘器的主要振动源和噪声源.在试验分析的基础上,提出了一些改善其振动和噪音性能的措施. 相似文献