- •Chapter I introduction
- •1. The subject of hydraulics
- •2. Historical background
- •3. Forces acting on a fluid. Pressure
- •4. Properties of liquids
- •Chapter II hydrostatics.
- •5. Hydrostatic pressure
- •6. The basic hydrostatic equation
- •7. Pressure head. Vacuum. Pressure measurement
- •8. Fluid pressure on a plane surface
- •Fig. 12. Pressure distribution on a rectangular wall
- •9. Fluid pressure on cylindrical and spherical surfaces. Buoyancy and floatation
- •Fig. 18. Automatic relief valve.
- •Relative rest of a liquid
- •10. Basic concepts
- •11. Liquid in a vessel moving with uniform acceleration in a straight line
- •12. Liquid in a uniformly rotating vessel
- •The basic equations of hydraulics
- •13. Fundamental concepts
- •14. Rate of discharge. Equation of continuity
- •15. Bernoulli's equation for a stream tube of an ideal liquid
- •16. Bernoulli's equation for real flow
- •17. Mead losses (general considerations)
- •18. Examples of application of bernoulli's equation to engineering problems
- •Chapter V flow through pipes. Hydrodynamic similarity
- •19. Flow through pipes
- •20. Hydrodynamic similarity
- •21. Cavitati0n
- •Chapter VI laminar flow
- •22.Laminar flow in circular pipes
- •23. Entrance conditions in laminar flow. The α coefficient
- •24. Laminar flow between parallel boundaries
- •Chapter VII turbulent flow
- •25. Turbulent flow in smooth pipes
- •26. Turbulent flow in rough pipes
- •27. Turbulent flow in noncircular pipes
- •Chapter VIII local features and minor losses
- •28. General considerations concerning local features in pipes
- •29. Abrupt expansion
- •30. Gradual expansion
- •31. Pipe contraction
- •32. Pipe bends
- •33. Local disturbances in laminar flow
- •34. Local features in aircraft hydraulic systems
- •Chapter IX flow through orifices, tubes and nozzles
- •35. Sharp-edged orifice in thin wall
- •36. Suppressed contraction. Submerged jet
- •37. Flow through tubes and nozzles
- •38. Discharge with varying head (emptying of vessels)
- •39. Injectors
- •Relative motion and unsteady pipe flow
- •40. Bernoulli's equation for relative motion
- •41. Unsteady flow through pipes
- •42. Water hammer in pipes
- •Chapter XI calculation of pipelines
- •43. Plain pipeline
- •44. Siphon
- •45. Compound pipes in series and in parallel
- •46. Calculation of branching and composite pipelines
- •47. Pipeline with pump
- •Chapter XII centrifugal pumps
- •48. General concepts
- •49. The basic equation for centrifugal pumps
- •50. Characteristics of ideal pump. Degree of reaction
- •51. Impeller with finite number of vanes
- •52. Hydraulic losses in pump. Plotting rated characteristic curve
- •53. Pump efficiency
- •54. Similarity formulas
- •55. Specific speed and its relation to impeller geometry
- •56. Relation between specific speed and efficiency
- •57. Cavitation conditions for centrifugal pumps (according to s.S. Rudnev)
- •58. Calculation of volute casing
- •59. Selection of pump type. Special features of centrifugal pumps used in aeronautical and rocket engineering
CONTENTS
Page
NOTATION AND ABBREVIATIONS …………………………………………….9
CHAPTER I. INTRODUCTION
The Subject of Hydraulics .....................................................................11
Historical Background ……………………………........................13
Forces Acting on a Fluid. Pressure………………………………………………...........................17
Properties of Liquids ……………………………………………18
CHAPTER II. HYDROSTATICS
Hydrostatic Pressure …………………………………………………….........25
The Basic Hydrostatic Equation ……………………………………………27
Pressure Head. Vacuum. Pressure Measurement ……………………………………………28
Fluid Pressure on a Plane Surface ……………………………………………33
Fluid Pressure on Cylindrical and Spherical Surfaces. Buoyancy and Floatation…………………36
CHAPTER III. RELATIVE REST OF A LIQUID
Basic Concepts ……………………………………………42
Liquid in a Vessel Moving with Uniform Acceleration in a Straight Line ………………….........43
12. Liquid in a Uniformly Rotating Vessel ……………………………………………44
CHAPTER IV. THE BASIC EQUATIONS OF HYDRAULICS
Basic Concepts …………………………………………....49
Rate of Discharge. Equation of Continuity ………………………………………........51
Bernoulli's Equation for a Stream Tube of an Ideal Liquid……………………………………..52
Bernoulli's Equation foi Real Flow ……………………………………………57
Head Losses (General Considerations) ……………………………………………60
Examples of Application of Bernoulli's Equation for Engineering. Problems…………………..64
CHAPTER V. FLOW THROUGH PIPES. HYDRODYNAMIC SIMILARITY.
Flow Through Pipes ....................................................................69
Hydrodynamic Similarity..................................................................................................................72
Cavitation ....................................................................77
CHAPTER VI. LAMINAR FLOW
Laminar Flow in Circular Pipes ……………………………………………80
Entrance Conditions in Laminar Flow. The a Coefficient……………………………………84
Laminar Flow Between Parallel Boundaries………..……………………………………………87
CHAPTER VII. TURBULENT FLOW
Turbulent Flow in Smooth Pipes ……………………………………………92
Turbulent Flow in Rough Pipes……….. ……………………………………………97
Turbulent Flow in Noncircular Pipes…………………………………………………………..101
CHAPTER VIII. LOCAL FEATURES AND MINOR LOSSES
General Considerations Concerning Local Features in Pipes…………………………………...104
Abrupt Expansion ………………………………………...105
Gradual Expansion ………………………………………...107
Pipe Contraction ………………………………………...111
Pipe Bends ……………………………………….113
33. Local Disturbances in Laminar Flow ………………………………………...118
34. Local Features in Aircraft Hydraulic Systems ………………………………………...122
CHAPTER IX. FLOW THROUGH ORIFICES, TUBES AND NOZZLES
35. Sharp-Edged Orifice in Thin Wall ………………………………………...124
36. Suppressed Contraction. Submerged Jet ………………………………………...129
37. Flow Through Tubes and Nozzles ………………………………………...132
38. Discharge with Varying Head (Emptying of Vessels)………………………………………137
39. Injectors……………………. ………………………………………......140
CHAPTER X. RELATIVE MOTION AND UNSTEADY PIPE FLOW
40. Bernoulli's Equation for Relative Motion …………………………………………149
41. Unsteady Flow Through Pipes …………………………………………151
42. Water Hammer in Pipes ……………………………………........155
CHAPTER XI. CALCULATION OF PIPELINES
Plain Pipeline …………………………………………162
Siphon …………………………………………166
Compound Pipes in Series and in Parallel …………………………………………167
Calculation of Branching and Composite Pipelines …………………………………………170
Pipeline with Pump …………………………………………172
CHAPTER XII. CENTRIFUGAL PUMPS
General Concepts …………………………………………182
The Basic Equation of Centrifugal Pumps ……………………………………........183
Characteristics of Ideal Pump. Degree of Reaction ……………………………………........187
Impeller with Finite Number of Vanes ……………………………………........190
Hydraulic Losses in Pump. Plotting Rated Characteristic Curve………………….…………..193
Pump Efficiency ……………………………………………196
54.Similarity Formulas ………………………………………….197
55. Specific Speed and Its Relation to Impeller Geometry…………………………………….202
56. Relation Between Specific Speed and Efficiency……………………………………..........205
57. Cavitation Conditions for Centrifugal Pumps (According to S. S. Rudnev)………………………210
Calculation of Volute Casing ………………………………………….214
Choice of Pump Type. Special Features of Centrifugal Pumps Used in Aeronautical and Rocket Engineering …………………………………………..216
CHAPTER XIII. DISPLACEMENT PUMPS
General Considerations. …………………………………………..222
Types of Rotary Pumps. …………………………………………..224
62. Characteristics of Rotary Displacement Pumps …………………………………………..230
CHAPTER XIV. HYDRAULIC TRANSMISSIONS
Translational Hydraulic Actuator …………………………………………..236
Follow-up Systems and Boosters …………………………………………..239
Rotary Hydraulic Transmissions …………………………………………..248
Rotodynamic Transmissions …………………………………………..253
APPENDIX. DIFFERENTIAL EQUATIONS OF IDEAL FLUID FLOW
AND THEIR INTEGRATION …………………………………………..257
Index ..................................................................268
Notation and abbreviations
a — acceleration
a — celerity of water-hammer pressure wave
A — parameter characterising injector
geometry
Aeq — equivalent injector parameter
—relative width of pump impeller
C — constant of integration
°C — degrees centigrate
D, d — diameter
—relative diameter of pump impeller
e — specific energy
E — energy, work
g — acceleration of gravity
G — weight of a fluid
G — weight rate of discharge
h — capillary rise or depression
h — piezometric head
h — loss of energy or head
hcon — loss of head due to contraction
hexp — loss of head due to expansion
hf — loss of head due to friction
hin — inertia head of liquid moving with
acceleration
hl — local losses
H — total head
Hav — available head
Hin — inertia head of liquid in accelerated
channel
Htz — head generated by idealised centrifugal
pump with definite number of vanes
Ht — head generated by idealised centrifugal
pump with infinite number of vanes
Hm — mean total head
Hreq — required head
Ht — theoretical or ideal head
i — resultant of body forces
i — acceleration of moving fluid
Jx — moment of inertia about an axis x
k — capillarity
k — roughness size of projections
k — any coefficient
keq — absolute roughness equivalent to
Nikuradse’s granular roughness
K — volume or bulk, modulus of elasticity
K — pipe entrance factor
—relative roughness
l — length
lent — entrance, or transition,length of pipe
leq — equvalent pipe length
M — mass
M — mass rate of discharge
n — rate of divergence of diffuser
n — speed of rotation
ns — specific speed
nx — tangential g-load
nv — normal g-load
N — power
N o — shaft, or brake, horsepower
Nx — tangential acceleration
Ny — normal acceleration
p — pressure
Pab — absolute pressure
Patm — atmospheric pressure
Pb — buoyancy force
Pf — pressure loss due to friction
pg — gauge pressure
pf — local loss of pressure
pt — saturation vapour pressure
Pvac — vacuum negative, presure
Pwh — water-hammer pressure
P — pressure force
Q — volume rate of discharge
Q — delivery, or capacity, of pump
Qt — theoretical, or ideal, delivery of
pump
r — radius
R — surface force
R — radius of curvature
RH — hydraulic radius, or hydraulic mean
depth
Re — Reynolds number
Recr — critical Reynolds number
Ret — theoretical, or ideal, Reynolds
number
S — area
t — temperature
T — friction, or shear, force
T — torque
u — peripheral velocity at pump
impeller
v — velocity
vcr — critical velocity
vm — mean velocity
vi — theoretical, or ideal, velosity of
efflux
w — relative velocity at pump impeller
W — volume
y — distance
z — number of vanes in pump impeller
z — vertical distance from any datum
level, elevation
α(alpha)— diffuser divergence angle
α — dimensionless coefficient accounting
for nonuniform velocity distribution
β(beta) — vane angle
βp — coefficient of compressibility
βi — coefficient of thermal expansion
γ(gamma) — specific weight
γef — effective, specific weight
Г(gamma) — circulation
δ (delta) — specific gravity
δ — pipe bend angle
δ — thickness
δe — laminar sublayer thickness
ε (epsilon) — coefficient of contraction of a jet
ζ (dzeta) — loss coefficient
ζ f — friction loss coefficient
η (eta) — efficiency
ηf — hydraulic efficiency
ηm — mechanical efficiency
ηv — volumetric efficiency
λ(lambda) — friction factor
λl — friction factor for laminar flow
λt — friction factor for turbulent flow
μ (mu) — coefficient of discharge of orifice
μ — vane number coefficient
μ — dynamic viscosity
ν(nu) — kinematic viscosity
ξ(xi) — form coefficient of orifice
π(pi). — perimeter
ο (rho) — density
σ (sigma)— stress
σ — cavitation parameter
τ (tau) — shear stress
φ (phi) — coefficient of velocity of an orifice
ψ (psi) — coefficient taking into account
stream contraction by pump
impeller vanes or hub
ω(omega) — angular velocity
ABBREVIATIONS
atm — atmosphere = 14.7 Ib/sq. in.
cm — centimetre=0.3937 in.
est — centistoke
g — gram = 0.03527 oz (avdp)
hr — hour
kg — kg = 1,000 2 = 2.205 lb (avdp)
lit — litre=0.2642 gal
In — natural (Napierian) logarithm
log — common (Briggs) logarithm
m — metre = 100 cm = 1,000 mm= 3.281ft
mm — 0.03937 in.
rpm — revolutions per minute
sec — second
kg-m — kilogram-metre = 0.009 btu
Chapter I introduction
1. The subject of hydraulics
The branch of mechanics which treats of the equilibrium and motion of liquids and gases and the force interactions between them and bodies through or around which they flow is called hydromechanics or fluid mechanics. Hydraulics is an applied division of fluid mechanics covering a specific range of engineering problems and methods of their solution. It studies the laws of equilibrium and motion of fluids and their applications to the solution of practical problems.
The principal concern of hydraulics is fluid flow constrained by surrounding surfaces, i.e., flow in open and closed channels and conduits, including rivers, canals and flumes, as well as pipes, nozzles and hydraulic machine elements.
Thus, hydraulics is mainly concerned with the internal flow of fluids and it investigates what might be called "internal" problems, as distinct from "external" problems involving the flow of a continuous medium about submerged bodies, as in the case of a solid body moving in water or in the air. These "external" problems are treated in hydrodynamics and aerodynamics in connection with aircraft and ship design.
It should be noted that the term fluid as employed in hydromechanics has a broader meaning than generally implied in everyday life and includes all materials capable of an infinite change of shape under the action of the smallest external forces.
The difference between a liquid and a gas is that the former tends to gather in globules if taken in small quantities and makes a free surface in larger volumes. An important property of liquids is that pressure or temperature changes have practically no effect on their volume, i.e.,for all practical purposes they can be regarded as incompressible. Gases, on the other hand, contract readily under pressure and expand infinitely in the absence of pressure, i. e., they are highly compressible.
Despite this difference, however, under certain conditions the laws of motion of liquids and gases are practically identical. One such condition is low velocity of the gas flow as compared with the speed of sound through gas.
The science of hydraulics concerns itself mainly with the motion of liquids. The internal flow of gases is studied only insofar as the velocity of flow, is much less than that of sound and, consequently, their compressibility can be disregarded. Such cases are frequently encountered in engineering, as for example, in the flow of air in ventilation systems and in gas mains.
Investigation of the flow of liquids, and even more so gases, is a much more difficult and complicated task than studying the motion of rigid bodies. In rigid-body mechanics one deals with systems of rigidly connected particles; in fluid mechanics the object of investigation is a medium consisting of a multitude of particles in constant relative motion.
To the great Galileo belongs the maxim that it is easier to study the motion of remote celestial bodies than that of a stream running at one's feot. Because of these difficulties, fluid mechanics as a science developed along two different paths.
The first was the purely theoretical path of precise mathematical analysis based on the laws of mechanics. It led to the emergence of theoretical hydromechanics, which for a long time existed as an independent science. Its methods provided an attractive and effective means of scientific research. A theoretical analysis of fluid motion, however, encounters many stumbling blocks and does not always answer the questions arising in real situations.
The urgent requirements of engineering practice, therefore, soon gave rise to a new science of fluid motion, hydraulics, in which researchers took to the second path, that of extensive experimenting and accumulation of factual data for application to engineering problems. At its origin, hydraulics was a purely empirical science. Today, though, whenever necessary it employs the methods of theoretical hydromechanics for the solution of various problems; and, conversely, in theoretical hydromechanics experiments are widely used to verify the validity of its conclusions. Thus, the iifference in the methods employed by either science is gradually lisappearing, and with it the boundary line between them.
The method of investigating fluid flow in hydraulics today is essentially as follows. The phenomenon under investigation is first amplified and idealised and the laws of theoretical mechanics are tpplied. The results are then compared with experimental data, the [iscrepancies are established and the theoretical formulas and solutions adjusted so as to make them suitable for practical application.
Many phenomena are so involved as to practically defy theoretical analysis and are investigated in hydraulics on the sole basis of experimental measurement, the results being expressed in empirical formulas Thus, hydraulics can be called a semiempirical science.
At the same time it is an applied, engineering, science insofar as it emerged from the demands of life and is widely used in engineering. Hydraulics provides the methods of calculating and designing a wide range of hydraulic structures (dams, canals, weirs and pipelines for transporting fluids), machinery (pumps, turbines, fluid couplings) and other devices used in many branches of engineering, in machine-tool design, foundry practice, the manufacture of plastics, etc. Modern aircraft design, with its fluid drives, fuel and lubricating systems, hydraulic shock absorbers, etc., relies extensively on the science of hydraulics.