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空气动力学英文PPT(Chapter_05)

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航空发动机专业英语之空气动力学

航空发动机专业英语之空气动力学

Introduced how to reduce the impact of emissions on aircraft performance and meet environmental regulations by optimizing exhaust emission design and control technologies.
With the continuous improvement of aircraft performance, the aerodynamic design of aircraft engines is affecting more string requirements, including higher take off and landing speeds, longer flight distances, and more complex flight conditions
Detailed description
Definition and Concepts
Understanding the characteristics and classification of fluids helps to gain a deeper understanding of the working principles of aircraft engines.
Air inlet aerodynamics
Explored the effects of aerodynamic phenomena in combustion chambers on combustion efficiency and emissions, including flame propagation speed, combustion stability, and combustion chamber outlet temperature distribution.

空气动力学PPT

空气动力学PPT

第二节 飞行器的运动参数与操纵机构
一、坐标系：
描述飞机的姿态、位置；飞机在大气中飞行，运动复杂，有多 个坐标系描述；美制与苏制，国标——美制 1.地面坐标系（地轴系） Sg og xg yg zg 原点og —地面某一点（起飞点） ogxg —地平面内，指向某方向（飞行航线） ogyg —地平面内，垂直于ogxg，指向右方 y ogzg —垂直地面，指向地心， x o 右手定则 z H 描述飞机的轨迹运动 “不动”的坐标系， ogxg x 惯性坐标系
二、飞机的运动参数（续）

速度向量与机体轴系的关系
1、迎角 速度向量V在飞机对称面上的投影与机体轴ox的夹 角，以V的投影在ox轴之下为正 2、侧滑角 速度向量V与飞机对称面的夹角。V处于对称面之 右时为正
产生空气动力的主要因素 对于飞控是重要的变量
三、飞行器运动的自由度
刚体飞机，空间运动，有6个自由度： 质心x、y、z线运动（速度增减，升降，左右移动） 绕质心的转动角运动 飞机有一个对称面：纵向剖面，几何对称、质量对称 1.纵向运动 速度V，高度H，俯仰角 2.横航向运动 质心的侧向移动，偏航角，滚转角 纵向、横航向内部各变量之间的气动交联较强 纵向与横航向之间的气动交联较弱，可以简化分析 飞机—面对称，导弹—轴对称
1 p V 2 p0 总压 2
V大，p小；V小，p大
四、马赫数M
马赫数：为气流速度(v)和当地音速(a)之比: 音速：微弱扰动在介质中的传播速度。


M
V a
音速：
a 20 T
T:空气的绝对温度
音速a与温度有关，表示空气受压缩的程度,是高度的函数 临界马赫数Mcr 迎面气流的M数超过某数值时，翼面上出现局部的超音速区， 将产生局部激波 ，此时远前方的迎面气流速度V与远前方 空气的音速a之比 Mcr-每种机翼的特征参数

空气动力学英文PPT(Chapter_02)

空气动力学英文PPT(Chapter_02)
Definition of infinitesimal fluid element:
an infinitesimally small fluid element in the flow, with a differential volume.
It contains huge large amount of molecules Fixed and moving infinitesimal fluid element. Focus of our investigation for fluid flow.
Fixed control volume and moving control volume. Focus of our investigation for fluid flow.
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2.3.2 Infinitesimal fluid element approach
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2.3.3 Molecule approach
Definition of molecule approach:
The fluid properties are defined with the use of suitable statistical averaging in the microscope wherein the fundamental laws of nature are applied directly to atoms and molecules. In summary, although many variations on the theme can be found in different texts for the derivation of the general equations of the fluid flow, the flow model can be usually be categorized under one of the approach described above.

空气动力学课件

空气动力学课件

2
N-S方程的解算

理论解法
–非线性问题 –精确解的限制 –初边值条件的适定性 –物理模型 (粘性、热力学模型、 …) –优缺点的比较
N-S方程的解算

计算流体力学 (CFD)
–网格化的流场就是一个离散的世界
J.D. Anderson, “Computational Fluid Dynamics: The Basics with Applications”, McGraw-Hill, 1995

积分形式的连续方程
dV V dS 0 S t V V [ t ( V )]dV 0

微分形式的连续方程 ( V ) 0
t
连续方程

定常流动
( V ) 0

S
V dS 0
u sin / r v cos / r
Vr u cos v sin 0 1 V u sin v cos r 1 Irrotational flow? z V r 0 r V rV r 2 V dl V rd 2

旋度

V
z
v u x y

无旋流

有旋流
From M. van Dyke’s “An album of fluid motion” Video?
角变形率

角变形
2 (1 )

角变形率
xy
d v u dt x y
流线之间的质量流量
c2 c1
d V lim n 0 n dn

(精品)空气动力学(全套1082页PPT课件)

(精品)空气动力学(全套1082页PPT课件)
雷诺（OsborneReynolds， 1842~1921），英国工程师兼物理学家， 维多利亚大学（在曼彻斯特市）教授。
录像\第0章\turbulent_laminarcombo.avi
0.3 空气动力学的发展进程简介
1904年普朗特提出了边界层理论，是 现代流体力学的里程碑论文。
在1910年-1920年期间，其主要精力 转到低速翼型和机翼绕流问题，提出著 名的有限展长机翼的升力线理论和升力 面理论。
陆士嘉长期从事空气动力学和航空工程的 研究和教学工作，倡导漩涡、分离流和湍流 结构的研究。
0.3 空气动力学的发展进程简介
儒可夫斯基简介 儒可夫斯基（Joukowski，
1847～1921），俄国数学家和空气 动力学家，科学院院士。1868年毕 业于莫斯科大学物理系，1886年起 历任莫斯科大学和莫斯科高等技术 学校教授，直至1921去世，一直在 这两所学校工作。
0.3 空气动力学的发展进程简介
• 钱学森（1911-2009） 1938年，他在导师冯卡门指导下，获
得博士学位，1947年任麻省理工学院终 身教授，1955年回国。
钱学森的主要贡献集中在跨、超声速 空气动力学方面。1946年他在一篇重要 的学术论文中首创了Hypersonic（高超 声速）一词，并提出了高超声速相似律。
的建立，流体力学和空气动力学才逐步迈 入理性研究和持续发展的阶段。
0.3 空气动力学的发展进程简介
微积分问世后，流体成为数学家们应用微 积分的最佳领域。
1738年伯努利出版了“流体力学”一书， 将微积分方法引进流体力学中，建立了分 析流体力学的理论体系，提出无粘流动流 速和压强的关系式，即Bernoulli能量方程。
0.2 空气动力学的研究对象

直升机空气动力学介绍(英文版)

直升机空气动力学介绍(英文版)

Thrust
Shock Waves
Aeroelastic Response
Unsteady Aerodynamics
0
Main Rotor / Tail Rotor / Fuselage Flow Interference
90
Tip Vortices
Blade-Tip Vortex interactions
Hinges
Only the lifts were transferred to the fuselage, not unwanted moments. In later models, lead-lag hinges were also used to Alleviate root stresses from Coriolis forces
V
180
270
Dynamic Stall on Retreating Blade
© L. Sankar Helicopter Aerodynamics
2
A systematic Approach is necessary
• • A variety of tools are needed to understand, and predict these phenomena. Tools needed include
© L. Sankar Helicopter Aerodynamics 7
Earliest Helicopter.. Chinese Top
© L. Sankar Helicopter Aerodynamics
8
Leonardo da Vinci (1480? 1493?)
© L. Sankar Helicopter Aerodynamics

航空发动机专业英语之空气动力学


Measurements
• In order to determine if the aerodynamic forces
on an object are sufficient to allow flight, the forces must be measured. The different contributions of the air moving around the object must be categorized and defined, and they must be quantified. There are specific qualities that are used to categorize and define these contributions. In addition, these qualities need a guideline to measure them by. The guidelines are called units, and the qualities are mass, time, length, and temperature.
Unit
• Units are used to define measurements so that
everyone knows exactly how much. They sound very technical, but they are used all over the world in every day examples. It is important to always include the units when talking about measuring a quality. If a bridge designer develops a bridge across a river that is supposed to be 1000 meters long (a measure of length), and one of the builders tells him or her that the bridge is short by 1, what does that mean?

空气动力学chapPPT课件


第5页/共111页
11.2 The Velocity Potential Equation(速度势方程)
STEP 1: VELOCITY POTENTIAL → CONTINUITY
V
ui
vj
i
j
x y
Flow is irrotational
u v
x
y
x-component y-component
steady irrotational
0
t
V 0 V
V
V
V
0
V u u v v 0 x x y y
Does a similar expression exist for compressible flows? Yes, but it is non-linear
infinite boundary condition：
u
x
V
v 0
y
wall boundary condition ： 0
n
第9页/共111页
4） How to use?
Once φ is known, all the other value flow variables are directly
Linearized velocity potential equation
Critical Mach umber
Prandtl-Glauet Compressibilty correction
Improved compressibilty Correction
Drag-Divergence Mach number: Sound Barrier
(1
M
2

空气动力学绪论PPT课件

Third Edition, International Edition. Mechanical Engineering Series, New York: McGaw-Hill, 2001
4
课程学习及考核要求：
1、完成每一章的作业； 2、完成两个实验；
（1）流体力学基础实验（4学时） （2）附面层测量试验 （2学时） 3、保证上课（缺勤不超过3次）； 4、通过考试。
边界层理论极大地推进了空气动力学的发 展。普朗特还把有限翼展的三维机翼理论系统 化，给出它的数学结果，从而创立了有限翼展 机翼的升力线理论。但它不能适用于失速、后 掠和小展弦比的情况。1946年美国的琼期提出 了小展弦比机翼理论，利用这一理论和边界层 理论，可以足够精确地求出机冀上的压力分布 和表面摩擦阻力。
23
0.3 空气动力学的发展进程
纳维(Navier)从分子相互作用的某一假设出发，于 1826年导出粘性流体运动方程。斯托克斯(Stokes)于 1845年在另一国家也独立地导出了粘性流体运动方程.雷 诺(Reynolds)在1876-1883年试验粘性流体在小直径圆 管中的流动时，发现了流体运动的层流和紊流性质， 1895年他导得了雷诺方程—平均N-S方程.
空气动力学基础
FUNDAMENTALS OF AERODYNAMICS
总学时 64
1
课程简介
本课程是空气动力学应用的基础，是从 事飞行器设计重要的专业理论知识，课程 主要内容是介绍流体力学和空气动力学的 基础理论和方法。
要求先期基础知识：
高等数学、计算方法 大学物理、理论力学
2
课程章节内容及学时分配
* 钱翼稷，“空气动力学”，北京航空航天大学出版社，2004 * 陈再新，刘福长，鲍国华，“空气动力学”，航空工业出版社，1993 * 徐华舫，“空气动力学基础”，北京航空航天大学出版社，1987 * 杨岞生，俞守勤，“飞行器部件空气动力学”，航空工业出版社， 1987 * John D. Anderson, Jr.,“Fundamentals of Aerodynamics”，

0空气动力学课件 共82页

基本原理
空气动力学、流体力学
无粘不可压流动
Bernoulli 方程、位流理论、基本解、K-J定理
无粘可压流动
热力学定律、等熵流动、激波理论、高速管流
第二部分课程结构（此处从略）
低速翼型理论
几何特点、K-J后缘条件、薄翼型理论
低速机翼气动特性
B-S定律、升力线（面）理论
钱学森(1911- )
流体介质的物理特性
连续介质假设 流体的密度、压强和温度 完全气体状态方程 压缩性、粘性和传热性 流体的模型化
连续介质假设
分子平均自由程 自由分子流/非连续流动 低密度流动 连续流动 continnum flow (l<<L) 连续介质假设
流体力学发展概述（1800- ）
Osborne Reynolds (1842–1912)
Nikolai Y. Zhukovsky (1847 –1921) K-J theorem
流体力学发展概述（1800- ）
Martin Wilhelm Kutta (1867-1944)
Ludwig Prandtl (1875 –1953)
u
n
流体的粘性
运动粘性系数 kinematic viscosity

适用于空气的萨特兰公式
0

T
1.5
28.185
28.185C TC
流体的粘性
空气粘柱实验模型 （卧式转盘）
n v
v
A
A
空气粘性实验
流体的粘性
流体的热传导特性
Fourier公式
dA 微团面积元的大小
dF dA一侧的法向力
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6. As the lift per unit span is proportional to the circulation, so, the circulation is also a function of y 7. The lift distribution goes to zero at the wing tips.
c, α
will be different.
3. Concept of geometric twist. washout and washin.
α has a distribution along the span direction
4. Concept of aerodynamic twist.
α L =0 has a distribution along the span direction
α eff = α − α i
2 The local lift vector is in the direction perpendicular to the local relative wind. As a subsequence, there is a drag created by the presence of downwash.
※ The two vortices tend to drag the surrounding air with them, and this secondary movment induces a small component is called downwash(下洗）. ※ The downwash velocity combines with the freestream velocity to produce a local relative wind which is canted downward in the vicinity of each airfoil section of the wing. ※ definition of induced angle of attack
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Single horseshoe vortex
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1. The bound vortex induces no velocity along itself 2. The two trailing vortices both contribute to the induced velocity along the bound vortex, and their contributions are in the downward direction. 3. The origin is taken at the center of the bound vortex. 4. The induced velocity at any location of y along the bound vortex by the two trailing vortices is :
中英文日报导航站
中英文日报导航站
中英文日报导航站
Question : why are the aerodynamic characteristics of a wing any different from the properties of its section? Airfoil can be respected as two-dimensional body, but any finite wing is a three-dimensional body. ※Attention should be paid for the flow pattern near the wing tips. And try to understand the reason for such a flow phenomena. ※ For general cases, there is a spanwise velocity component on both top and bottom surface of the wing, but their direction are different. ※ A trailing vortex is created at each wing tip. These wing-tip vortices downstream of the wing induce a small downward velocity in the neighborhood of the 中英文日报导航站 wing itself.
8. The calculation of the lift distribution L′( y ) [or the circulation distribution Γ( y ) ] is one of the central 中英文日报导航站 problems of the finite-wing theory.
中英文日报导航站
Helmholtz’s Theorems For inviscid and incompressible flows 1. The strength of a vortex filament is constant along its length. 2. A vortex filament cannot end in a fluid; it must extend to the boundary of the fluid or form a closed path. Concept of lift distribution along the span of a finite wing 1. L′( y1 ): lift per unit span at location y1
5.3 Prandtl’s Classical Lifting-line Theory
Importance of the Prandtl’s lifting-line theory
bound vortex and free vortex
Replacement of the finite wing with a bound vortex
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中英文日报导航站
Conclusion: the presence of downwash over a finite wing reduces the angle of attack that each section effectively sees, and moreover, it creates a component of drag ---- the induced drag Di . And this drag is not produced by viscous friction. Explanation of induced drag in physical sense a wing-tip vortices destroy the net pressure balance b the wing-tip vortices contain large amount of translational and rotational energy, and this energy serves no useful purpose. In effect, the extra power should be provided by the engine to overcome the the induced drag.
5. As there is different distribution of the chord of the airfoil, geometric angle of attack, and zero lift angle of attack, the lift per unit span at location y2 , L′( y2 ) will 中英文日报导航站 ′( be different from L 1 )
中英文日报导航站
※ Road map and purpose of this chapter ※ Support points for our analysis 1. Curved vortex filament 2. Biot-Savart Law 3. Helmholtz’s vortex theorems
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中英文日报导航站
2. With the different location in the span direction, the chord and attack angle may be different, that means
பைடு நூலகம்
r r r Γ dl × r dV = r3 4π r
Application of Biot-Savart Law 1. To a straight vortex filament of infinite length
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2. To a semi-infinite vortex filament
Chapter 5
Incompressible Flow Finite Wings
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5.1 Introduction
The properties of airfoils are the same as the properties of a wing with infinite span. However, all real airplanes have wings of finite span. In the present chapter, we will apply our knowledge of airfoil properties to the analysis for finite wings. As we have mentioned in the previous chapter, the analysis for the aerodynamics of wings is separated in two steps. Now, we are going on the second step in Prandtl’s philosophy of wing theory.