流体力学复习资料及英文专有名词解释

Chapter 1 Fluid statics 流体静力学

1. 连续介质假定(Continuum assumption)：The real fluid is considered as no-gap continuous

media, called the basic assumption of continuity of fluid, or the continuum hypothesis of

fluid.流体是由连续分布的流体质点(fluid particle)所组成，彼此间无间隙。它是流体力学中最基本的假定，1755年由欧拉提出。在连续性假设之下，表征流体状态的宏观物理量在空间和时间上都是连续分布的，都可以作为空间和时间的函数。

2. 流体质点（Fluid particle ）: A fluid elementthat is small enough with enoughmoles to make

sure that the macroscopic meandensity has definite valueis defined as a Fluid Particle.宏观上足够小，微观上足够大。 3. 流体的粘性（Viscosity ）: is an internal property of a fluid that offers resistance to shear

deformation. It describes a fluid's internal resistance to flow and may be thought as a measure of fluid friction.流体在运动状态下抵抗剪切变形的性质，称为黏性或粘滞性。它表示流体的内部流动阻力，也可当做一个流体摩擦力量。The viscosity of a gas increases with temperature, the viscosity of a liquid decreases with temperature.

4. 牛顿内摩擦定律（Newton’s law of viscosity ）：

5. The dynamic viscosity （动力黏度）is also called absolute viscosity （绝对黏度）. The kinematic

viscosity （运动黏度）is the ratio of dynamic viscosity to density.

6. Compressibility （压缩性）：As the temperature is constant, the magnitude of

compressibility is expressed by coefficient of volume compressibility (体积压缩系数) к , a relative variation rate （相对变化率） of volume per unit pressure.

The bulk modulus of elasticity (体积弹性模量) E is the reciprocal of coefficient of volume compressibility к.

7. 流体的膨胀性(expansibility; dilatability)：The coefficient of cubical expansion (体积热膨胀

系数) αt is the relative variation rate of volume per unit temperature change.

8. 表面张力Surfacetension : A property resulting from the attractive forces between

du dz

τμ=μ

νρ

=

molecules.σ-----单位长度所受拉力

9. 表面力 Surface force ——is the force exerted on the contact surface by the contacted fluid

or other body. Its value is proportional to contact area.作用在所研究流体外表面上与表面积大小成正比的力。Stress （应力） is the surface force on per unit area.

10. 质量力Mass force ——The force acting on every fluid mass particle within the control body.

Its value is proportional to its mass. Mass force is also known as body force. 作用在流体的每一个流体质点上，其大小与流体所具有的质量成正比。 11. Euler Equilibrium Equations 欧拉平衡微分方程（分量式） 1775年

Physical Meaning:

For the fluid in equilibrium, surface force components per mass fluid are equal to mass force

components per mass fluid. Pressure variation rate in axes directions are equal to mass force components per unit volume in axes directions respectively

12. constant-pressure Surface(等压面)——a surface that the pressure of every point in liquid

is equal. Common constant-pressure surfaces are free liquid surface and interface of two

unmixed fluids in equilibrium.平衡流体中压强相等的点所组成的平面或曲面。

13. Pressure Distribution in the Static Fluid

Conclusions:

1. Pressure at a point in a static fluid under gravity increases linearly with depth.

2. Pressure at a point in a static fluid under gravity is equal to the sum of the pressure at the free surface and the fluid specific weight timing depth.

3. constant-pressure surface in a static fluid under gravity is a horizontal plane.

4. Extended: while the pressure at a point and the depth difference between two points are known, the pressure at another point can be calculated.

14. Absolute pressure(绝对压力), Gage pressure(相对压力, 又称“表压力”), and Vacuum(真

空度): 表压力＝绝对压力－大气压力; 真空度＝大气压力－绝对压力

15. Fluid in Relative Equilibrium (相对静止流体) Equation of constant-pressure surface(等压面

方程):

a) Uniform Linear Acceleration 等加速度直线运动流体: (,,)p p p

x y z

??????(,,)x y z f f f ρρρ 0

p C dp ==或cos d (sin )d 0

a y a g z αα+-=

b) Uniform Rotation about a Vertical Axis 等角速度旋转流体:

Chapter 2 basic equations of fluid mechanics

16. 迹线pathline ：the trace after a single particle travels in a field of flow over a period of time.

流体质点的运动轨迹曲线

17. 流线streamline ： a curve that show the direction of a number of particles at the same

instant of time.某一时刻处处与速度矢量相切的空间曲线--瞬时性。

18. Stream-tube (流管)——Consider a closed curve(not streamline) in the flow field, then draw

streamlines through every point on it, so as to form a tube-shaping space whose walls are streamlines. This tube is called the stream-tube. 在流场中任取一个有流体从中通过的封闭曲线，在曲线上的每一个质点都可以引出一条流线，这些流线簇围成的管状曲面称为流管。

19. Tube-flow 流束——Fluid fulling the stream tube is called the tube-flow and the limit of a

tube-flow is a streamline.流管内的全部流体称为流束。

20. Mini stream-tube 微小流束——The stream tube with an infinitesimal section is said to be

mini-stream tube. Streamline is the extreme case of mini-stream tube.截面无穷小的流束。

21. Total flow 总流——Total of countless mini-stream tubes is called total flow.包含流动中所

有的微小流束。

22. Cross section (过水断面)---The section is perpendicular to the direction of fluid flow. (such

as pipe flow and channel flow) 与流束或总流流线成正交的断面。

23. Discharge (流量)---Amount of fluid pass through a cross section per unit time (such as the

section in the channel or pipe).单位时间内通过某一过水断面的流体体积称为体积流量，简称流量。

24. Mean velocity 断面平均流速---The velocities of points on the same cross section in the

total flow are different, so usually an average velocity is used instead of the real velocity over the cross section, this average velocity is called the mean velocity.

(,,,)(,,,)(,,,)dx dy dz

u x y z t v x y z t w x y z t ==

()()()

dt t z y x w dz

t z y x v dy t z y x u dx ===,,,,,,,,,,dA A

25. Uniform flow 均匀流：is defined as uniform flow when in the flow field the velocity and

other hydrodynamic parameters do not change from point to point at any instant of time (in which the cross section of each stream tube remains unchanged. 流场中每一空间点的各运动参数（速度，压力）不随空间位置而变化。

26. Nonuniform flow 非均匀流：Flow such that the velocity varies from place to place at any

instant.

27. Steady flow 恒定流：the flow whose motion factors don ’t change with time. 流场中所有

的运动要素不随时间变化.

28. Unsteady flow 非恒定流：the flow that at least one of its motion factors changes with time.

流场中至少有一个运动要素随时间变化.

29. One dimensional flow (一元流动) -- all main variables in the flow field can be completely

specified by a single coordinate if the variation of flow parameters transverse to the

mainstream direction can be neglected.流动参数只与一个坐标变量有关。

30. Two dimensional flow(二元流动)- fluid motion factors are function of two space

coordinates. 流动参数与两个坐标变量有关。

31. Three-dimensional Flow (三元流动): Fluid flow ’s motion factors are functions of three

space coordinates.流动参数与三个坐标变量有关。

32. System （系统）——is a set of definite fluid particles selected in the interest of researcher.

由确定的流体质点组成的流体团或流体体积V(t)。系统边界面S(t)在流体的运动过程中不断发生变化。反映了拉格朗日观点

33. Control volume (控制体 CV)——is defined as an invariably hollow volume or frame fixed

in space or moving with constant velocity through which the fluid flows.相对于坐标系固定不变的空间体积V 。是为了研究问题方便而取定的。反映了欧拉观点

For a CV :

1) its shape, volume and its cscan not change with time. 2) it is stationary in the coordinate system. (in this book) 3) there may be the exchange of mass and energy on the cs.

34. Control surface 控制面 : the surface area completely encloses the CV. 边界面S 称为控制

面。

35. differential form of continuity equation 微分形式的连续性方程

()0?Φ=v 0

y x z v v v t x y z

ρρρρ????+++=????

For incompressible fluid

For 2-D incompressible flow

Physical meaning: The net mass discharge entering the control volume is equal to the mass increased in unit time due to the change in density.

Fit for: Steady flow, unsteady flow, compressible and incompressible fluid, ideal fluid and real fluid.

36.

Physical meaning ：在单位时间内，由于控制体内密度变化引起的质量变化量（增加量或减

少量）与通过控制体表面的质量净流出量（流出与流入的质量差）之和等于零。

Steady flow 定常流动

incompressible fluid 不可压缩流体

37. Motion Differential Equation 运动微分方程 For IDEAL FLOW

for Viscous Flow

0y x

z

v v v x y z

???++=

???0n CS

v dS ρ=?

n

CS v dS =?

1122v S v S =222222

222222222222

1()1(1()x x x x x x x x x y z y y y y y y y y x y z

z z z z z z z z x y z

v v v v v v v p f v v v x t x y z x y z v v v v v v v p

f v v v y t x y z x y z v v v v v v v p

f v v v z t x y z x y z νρνρνρ????????-+++=+++????????????????-+++=+++????????????????-+++=+++????????

38. Bernoulli Equation 伯努利方程

（1）steady flow 定常流动

（2）incompressible flow 不可压缩

（3）integration along a streamline 沿流线积分 （4）mass force is a potential force 质量力有势 For streamline

For compressible flow in gravity field

For compressible flow with fluid machinery in gravity field

z (m) —— the elevation height above datum surface o-o, called the elevation head (位置水头).

p /(ρg)——rising height of fluid with unit weight under the action of pressure P , called the pressure head (压力水头).

u 2/(2g) ——rising height of fluid with unit weight under the action of velocity V , called the velocity head (速度水头), denoted as hu

—— the lost mechanical energy from 1 to 2 points per unit weight fluid

——The effective energy obtained after the unit weight of the liquid flows through the pump.单位重量液体流经泵后获得的有效能量。Head of delivery 扬程 The sum of them is called the total head (总水头) , denoted as H .

Pump power 泵功率：

For the ideal-fluid total flow 理想流体总流的伯努利方程

for the real-fluid total flow 实际流体总流的伯努利方程

39. momentum integral equation 动量积分方程

For CV

f

h

2

2

212121

H 2ρ--=++-p p v v z z g g

w T P H Q γ

=22

1122112222ααρρ++=++p v p v z z g g g g

——sum of the fluid momentum change in CV and the net outflow momentum in CS, is

equal to the resultant force.

Steady flow ：

40. Moment-of-momentum integral equation 动量矩积分方程

For steady flow ：

[流出动量矩]CS – [流入动量矩]CS = [合外力矩]CV+CS

41. Forces on bend (弯头）

42. fluid jets on deflector(导流板）

43. Sprinkler(喷水器） 角速度：

固定所需力矩

Chapter 3 Pipe Flow and Boundary Layer Theory (管流和边界

层概述)

()d d S

n S

S S

ρ++

???

??v v n p ()d d d n

S

V

S

S V S

ρρ?=+???????v v n f p 乙

()()d ()d ()d n S

S

V

S V S

ρρ??=?+

???

?????

r v v n r f r p 乙211122(cos )()()cos a a x Q v v p p A p A F p ρθθ--+---'=222sin ()sin a y Qv p F p A ρθθ---'=2y 22sin ()sin ’

ρθθ--=-a Qv p R p A 211’

122(cos )()()cos ρθθ

--+-=--a a x Q v v p p A p p A R 121222222

1212()4()()

v r r Q r r r r d r r ωπ++==++

44. Laminar flow (层流) ： In the fluid flow the fluid particles move along smooth path in

layers without transverse velocity in the direction of main flow, one layer glides smoothly over an adjacent layer.

45. Turbulent flow (紊流, 湍流) or Turbulence ：If the fluid particles have a transverse velocity

normal to the main flow direction, that leads to particles mixing up each other, with a violent transverse interchange of momentum. This is turbulent flow (紊流, 湍流) or turbulence.

46. Reynolds number 雷诺数：is used to describe the characteristic of flow.

47. Wetted perimeter (湿润长度)：The length of wall contacted with liquid.

48. the hydraulic diameter (水力直径) D H : The characteristic dimension of noncircular tube. 49. Head Loses （能头损失，或水头损失)：the total energy losses per unit weight （单位重

量流体所损失的机械能为能头损失(水头)）, which due to the resistance between two sections of gradually varied flow. （流体流动,克服粘性内摩擦力,消耗机械能为热能.）

50. Friction Loss 沿程水头损失(h λ): In the flow through a straight tube with constant cross

section, the energy loss increases linearly in the direction of flow and the loss is called

friction loss . (原因: 粘性内摩擦力,以及与管壁的摩擦阻力)

Darcy-Weisbch (达西-韦斯巴赫) Equation:

λ: the coefficient of friction loss 沿程阻力系数,与流态和壁面有关

51. Local losses 局部水头损失(h ξ) ：When the shape of flow path changes, such as section

enlargement and so on, it will give rise to a change in the distribution of velocity for the

flow. The change results in energy loss, which is called minor loss or local loss . 原因: 流速急剧变化,流体质点剧烈撞击和摩擦.

ζ：minor loss coefficient or local loss coefficient 为局部阻力系数,与障碍物形式有关

52. Head losses 总能量损失(h f =h λ+h ξ)

53. LAMINAR FLOW THROUGH CIRCULAR TUBE 圆管中的层流 Velocity distribution in cross section

2

2λλ

=L v h D g

2

2ξζ

=v h g

λξ

=+∑∑

f h h h 22

()()4μ?∴=

-p u r R r L

2

14τμ????=

-??

???????

w

D r R

Discharge

—Hagen-Poiseuille (哈根-泊肃叶) equation.

Distribution of shear stress 切应力分布：

壁面剪切力

54. Head loss along the path 沿程能量(阻力)损失

pressure drop 压强损失

Head loss 水头损失：

the coefficient of friction loss ：

Power loss(功率损失)：

55. Pulsation Phenomenon （脉动现象）：The phenomenon that the physical parameter

fluctuates around a certain average value is called pulsation phenomenon （脉动现象）.

u=ū+ u'

2max 4μ?

∴=p u R L ()2v dq udA u r rdr

π==0()2R v v q dq u r rdr π==??

220

()24R

p R r rdr L πμ?=

-?

4 8R p L πμ=?2max

2

R u π=2 π==v q vA v R =?

v A q udA ()220

24πμ?=-?

R

p R r rdr L 48πμ=?R p L 4128πμ=?D p

L

()

22

4μ?=-?

A p R r dA L 2τμ

?=-=du p

r dr L

2τ?=w

p R L 2

8Re ρ=v

2τπ=w F RL 22π?=pR RL L 2π=?R p 228μπ=Lv R R 8πμ=Lv

48νπv L q gR 4128νπ=v L q gd 28ν=Lv

gR 232ν=Lv gd λρ=v W gh q =?=?v pq pAv 22

448128μμππ==

v v

L q L q R d

where: ū is time-average velocity (时均速度); u' -the component of random fluctuating velocity(脉动速度).

56. hydraulic smooth (水力光滑): If viscous sublayer δmore than absolute roughness ε(ie. δ>ε),

the effect of ε for the core of turbulent flow is very little, namely, the influence of εin the energy loss is very little.

57. hydraulic rough (水力粗糙): If viscous sublayer δless than absolute roughness ε(ie. δ<ε), the

fluid particles with certain velocity impact or crash the roughness projections of pipe wall,

so the velocity of these particles changes radically. It causes eddy (涡流) or vortex (漩涡) locally. Meantime the influence is transferred to the core of turbulent flow. So ε plays an important role in the energy loss.

58. Parallel lines 并联管路——By a few simple lines or tandem line which inlet side and outlet

piping connected respectively.

59. Pipeline in series/ tandem lines(串联管路）：——By a couple of different diameter or

different roughness pipe line.

60. Boundary Layer 边界层:The fluid particles on a solid boundary must adhere to (粘着，附着)

the solid wall in spite of (不论) the Reynolds number Re in the flow. The velocity of fluid near the boundary varies rapidly in a steep (陡的) velocity gradient (速度梯度) outward normal to the wall where the fluid has a zero velocity. The velocity gradient sets up (产生) shear force near the boundary and for this reason the effect of viscosity can not be neglected in the region. This region called Boundary layer.

The larger the Reynolds number is, the thinner the boundary layer is.

Chapter 4 Orifice Outflow and gap flow(孔口出流与缝隙流动)

61. Thin-walled orifice (薄壁孔口) ：,the edge thickness slightly effects the jet flow,

and only minor loss was considered, the contracted section located at d/2 after the hole.

/2l d ≤12==

=f f f h h h 12discharge =++Q Q Q L L 22

112211221222λ?λ?????=++++

? ?????∑

∑

f l v l v h d

g d g 1122Total discharge ===Q v A v A L

L

62. Thick-walled orifice(厚壁孔口)：, also named long orifice(长孔口)/nozzle(管嘴) .

The edge thickness distinctly effects the jet flow, and the flow was first contracted and then diffused until contacting the wall. Both frictional loss and minor loss should be considered.

63. big orifice （大孔口）：H /d <=10，the head, pressure, velocity on the section will be changed

with the height.

64. small orifice （小孔口）：H /d >10，the head, pressure, velocity on the section will NOT be

changed with the height.

65. free outflow （自由出流）：the jet flows into atmosphere directly, the pressure on the

contracted section was BAR, p c =p a .

66. submerged outflow （淹没出流）：the jet flows down to the water.

67. Contracted section 收缩断面：the streamlines were contracted after the hole, and the

section reached the minimum at d/2, which was the contracted section C —C.

68. contraction coefficient 收缩系数：the ratio between the contracted section area and the

hole area, labeled as C c :

69. The discharge calculation of steady free flow in orifice 孔口恒定自由出流流量计算

Cvis the velocity coefficient 流速系数

discharge coefficient 流量系数

70. gap flow between stationary 固定平板间的缝隙流动

velocity distribution

discharge

2/4l d <≤/1

c c C A A =

C gH v v c 2211

=+=ζr c v C C C =2

12

1d 2d p u z C z C x μ=++2

2

/max

8h L

p u h z μ?=

=2003d ()d 212h h v B p B p q B u z hz h z z L L μμ??==-=??

2

12v v q q h p v A hB L

μ?=

==

average velocity

pressure loss

71. gap flow between relatively moved parallel plates 具有相对运动的两平行平板间的流动 velocity

discharge

压差与平板运动方向相同取正号；方向相反取负号

72. gap flow between concentric cylinders 同心圆环间的缝隙流动

discharge

Chap. 5 Similitude and Dimensional Analysis 相似理论和量纲

分析

73. The three similarities are essential conditions of Dynamic Similitude of Fluid Motion(流动

相似), in which, at any time, all the parameters of the model and prototype are in the same ratio throughout the entire flow field.Dynamic Similitude of Fluid Motion(流动相似) includes Geometric similarity 几何相似, Kinematic similarity 运动相似, and Dynamic similarity 动力相似; Geometric similarity 几何相似 is the basicand the most obvious requirement; Kinematic similarity 运动相似 is the result; Dynamic similarity 动力相似 is the conditions.

dynamic similarity includes kinematic similarity, while kinematic similarity includes geometric similarity. Hence, ratios of force, time and length are same under dynamic similarity, and other quantities are also equal. 动力相似包括运动相似，而运动相似又包括几何相似。所以动力相似包括力、时间和长度三个基本物理量相似。两系统的其它物理量由它们决定，也必然相似。

The initial conditions(初始条件)and boundary conditions(边界条件) also must be coincident for dynamic similitude of fluid flow except above three similarities.

74. Newton number(牛顿数),

3

12v

Lq p Bh μ?=2

()2p U u hz z z L h

μ?=-±3122

v Bh p UBh q L μ?=±3

122v

dh p dUh

q L ππμ?=±

75. Reynolds number 雷诺数

76. Froud number 弗劳德数

77. Strouhal number 斯特洛哈尔数

78. Euler number 欧拉数

79. Dimension 量纲[ ]：Unit types of physical variables (物理量测量单位的类别); For one

quantity, only one dimension, but different units(同一量,可以有不同的单位,单仅有一个量纲).

80. Dimensional Homogeneity 量纲齐次性/Dimension concordant principle 量纲和谐原理）:

The dimensions on both sides of equation are correspondingly equal.(等式两边各项的量纲对应相等)

81. π-theorem (π-定理): The number of independent dimensionless groups ofvariables needed

to correlate the variables in a given process is equal to n-m , where n is the number of variables involved and m is the number dimensions included in the variables.若一个物理现象可由 n 个物理量构成的物理方程式描述，在n 个物理量中有m 个独立的物理量，则该物理现象也可以用这些量组成的（n －m ）个无量纲群的关系来描述。

Chapter 6 1-D compressible gas flow 可压缩气体的一元流动

82. isothermal process 等温过程

Ne v

l F

=2

2

ρ =∝convective inertial force

local inerti vt St al L

force

83. adiabatic process 绝热过程

等熵过程

85. The speed of sound 声速 is defined as the rate at which an infinitesimal

disturbance

(pressure pulse)propagates in a medium with respect to the frame of reference of that

medium.

Which shows how to the pressure and density change across the wave.声速是反映流体压缩性大小的物理参数，声速c 越小，流体的可压缩性越大。

86. Mach-number 马赫数：ratio of the inertial to elastic forces acting on the fluid. 定义流场中某一点的速度与该点的当地声速之比为马赫数。 For ideal gas

87. Mach angle(马赫角)：The half-vertex angle of Mach cone (马赫锥) is called Mach angle(马

赫角) .

88. 1.Integral form of continuity equation 连续性方程积分形式

89. differential form of continuity equation 连续性方程微分形式

90. Energy equation of Isentropic flow 等熵流动的能量方程

0=dQ nstant or k pv =Constant u

Ma c =

1sin c V Ma θ==111222u A u A ρρ=uA c

ρ=ln()ln ln ln uA u A C ρρ=++=d d d 0u A

u A

ρρ++=