1. 1
Comments on
FLUID MECHANICS
FUNDAMENTALS AND APPLICATIONS
2nd edition (SI Units)
McGraw-Hill, 2010
Yunus. A. Cengel and Michael. A. Boles
By: Mohsen Hassan vand
Saturday, February 28, 2015

2. 2
1. Pg. 2 ,L3-L4
while the branch that deals with bodies in motion is called dynamics.
while the branch that deals with bodies in motion under the action of forces is
called dynamics.
2. Pg. 3, FIGURE 1–3
3. Pg. 10, FIGURE 1–17
National Committee from Fluid Mechanics Films
National Committee for Fluid Mechanics Films
4. Pg. 10, P2, L 4
no-slip condition no-slip condition
5. Pg. 12, P5, L 7
The eddies produce shock waves that move upstream….
The wake produces waves that move upstream…
Please see figure 67 in Van Dyke’s book [An Album of Fluid Motion]
6. Pg. 13, P3, L 7

3. 3
The velocity profile develops fully and remains unchanged after some distance
from the inlet (about 10 pipe diameters in turbulent flow, and less in laminar pipe
flow,
The velocity profile develops fully and remains unchanged after some distance
from the inlet (about 10 pipe diameters in turbulent flow, and more in laminar pipe
flow,
Please see the sentence under the relation (8-7) in page 343. [That is: The entry
length is much shorter in turbulent flow, as expected, and its dependence on the
Reynolds number is weaker.]
7. Pg. 17, under relation (1-1)
…to accelerate a mass of 32.174 lbm (1 slug)
...to accelerate a mass of 1 slug (32.174 lbm)
8. Pg. 18, P3, L5
Therefore, the gravitational acceleration g at a location depends on the local
density of the earth’s crust,….
Therefore, the gravitational acceleration g at a location depends on latitude,…
Note: The local density of the earth’s crust has a very minute or negligible effect
on the gravitational acceleration g.
9. Pg. 21, FIGURE 1–39
It is suggested that the formulae to be separated by commas (,).
10.Pg. 27, EXAMPLE 1–5, P3
this system of two nonlinear equations
this system of equations ( one linear and one nonlinear)
11.Pg. 28, L4
Reporting results in more significant digits implies

4. 4
Reporting results in more significant digits falsely implies….
12.Pg. 31, P1, L2
Regarding this phrase “if the batteries in the stopwatch were weak, its accuracy
could be quite poor”, it seems that until the batteries voltage drop below a certain
threshold value, the stopwatch will be almost pretty accurate. Toward the end of
batteries life, when the batteries voltage falls below that threshold voltage,
stopwatch runs slow and loses its accuracy.
13.Pg. 32, P1, L3
An atomic blast A nuclear blast
14.Pg. 34, in Probs.1-39 and 1-40
converstion conversion
15.Pg. 35, in Prob.1-56
FD=function (C Drag, A front,….) FD=FD (C Drag ,A front,….)
16.Pg. 40, L4 after (2-4)
Ru = 8.314 kJ/kmol Ru= 8.314 kJ/kmol · K
17.Pg. 40, L5 from bottom,
krypton and even heavier gases such as carbon dioxide
carbon dioxide and even heavier gases such as krypton
Note: krypton (83.8 g/mol) is heavier than carbon dioxide (44 g/mol).
18.Pg. 44, L1 after (2-11)
19.Pg. 46, FIGURE 2–13,(a) and (b)
( ) ( ) .P P
V V
T
T T

5. 5
Note: 1T C , and the dimension of
( ) .P
V
T
T is the dimension of volume.
20.Pg. 48, P1,L4
a slight rise in local pressure a slight change in local pressure
21.Pg. 48,
FIGURE 2–14 should be corrected.
22.Pg. 49, L13,
2 2
( )dV dV
Note:
2
2dV VdV
23.Pg. 53, P3, L1 (and Pg. 61,second column, L6)
The viscosity of a fluid is a measure of its “resistance to deformation.”
The viscosity of a fluid is a measure of its “resistance to the rate of deformation.”
24.Pg. 60, EXAMPLE 2-7, last sentence after the formula,
Therefore, if a hole is drilled in the tube, air will leak into the tube rather than
water leaking out.
Therefore, if a hole is drilled in the tube, air will leak into the tube and some water
leaks out, until the free surface (or meniscus) stands on the level where the hole is
drilled.
25.Pg. 61,P2, last L
generating highly destructive, extremely high-pressure waves.
generating highly destructive, extremely high-pressure shockwaves.
26.Pg. 63 , item 3,
Y. A. Cengel Y. A. Cengel

6. 6
27.Pg. 76, FIGURE 3–5
28.Pg. 78, FIGURE 3–9
with distance from the free surface with vertical distance from the free surface
29.Pg. 79, FIGURE 3–12
W rghA W ghA
30.Pg. 84, FIGURE 3–20
31.Pg. 105, relation (3-49) & Pg. 109, relation (3-64)
Pressure variation Pressure distribution
32.Pg. 108, FIGURE 3–57
The distance between limit lines [for showing ,maxsz ] should be shorter and
shifted to the right place.
33.Pg.123, FIGURES P3-112 and P3-113

7. 7
The same modification should also be applied to Figures P3-150, P3-151.
34.Pg. 124, FIGURE P3-118
1 1
7 7
He air He airr r
35.Pg. 126, Prob3-135
It seems that another factor for water overflow from the service tube is bubble
formation (when the water is boiling). Bubbles reduce the water apparent density
[two-phase density], and therefore lift the water to higher elevations, both inside
the teapot and outside the teapot in the service tube).
36.Pg. 127, Prob3-139
The figures in the table should be rearranged.
37.Pg. 131( and in middle parts of page 159)
Reynolds transport theorem (RTT) Reynolds Transport Theorem (RTT)
38.Pg. 135, relation(4-10)
( ) ( , , )
, ,x y z x y z
39.Pg. 136, EXAMPLE 4–2, P5,
We now calculate the acceleration two ways
We now calculate the acceleration in two ways
40.Pg. 137, FIGURE 4–12
, 2 2 , 3 3t dt t t t dt t t t dt t t
Note: Mathematically, 2 3 0dt dt dt adt .
41.Pg. 139,L4

8. 8
computational fluid dynamics (CFD) Computational Fluid Dynamics (CFD)
42.Pg. 139,FIGURE 4–16
( , )dr dx dy dr dx dy
43.Pg. 141,last P, L1
particle image velocimetry (PIV) Particle Image Velocimetry (PIV)
44.Pg. 142,FIGURE 4–23
45.Pg. 155, FIGURE 4–45
Very important: The fluid particles shown in this figure are misleading! Because
one may mistakenly think that these fluid particles are all the same, but in
different locations and moments, and therefore if an individual spherical fluid
particle is followed on its path, that particle keeps its spherical shape and rolls
down with a rotational speed toward downstream . But we know that fluid
particles deform during motion [The overall motion of a particle is a combination
of its rotation and deformation (+translational)].
The vorticity is just a local and instantaneous property or concept, and
therefore we cannot trace a fluid particle in space and time (different locations
and moments) and then to expect that it really rotates with rotational speed .
Please note that in boundary layers the is most often very high and a fluid
particle cannot roll down with that high rotational speed.
46.Pg. 157, in (4-34) and in Pg 158,example 4-9, relation(2)
0 0
47.Pg. 162, P3
In this paragraph it is referred to the Leibnitz theorem without giving any previous
explanation about it. It is suggested to introduce it in a separate paragraph in one-

9. 9
and three-dimensional forms mathematically [because the Leibnitz theorem is
actually the General Transport Theorem], and then derive the Reynolds
Transport Theorem from it as a special form { when the volume under
consideration is a material volume Vm within the surface Sm and sv v .
Leibnitz theorem or General Transport Theorem:
1D:
3D:
where sv = local and instantaneous velocity of the control surface S.
48.Pg. 172, Prob 4-40
The velocity field should be modified as: / 2u K r . In this form, K is the line
vortex strength.
Note: Please see the form of the relation given for line source in Prob 4-41.
49.Pg. 174, FIGURE P4-53,
and
50.Pg. 174, FIGURE P4-56
and
51.Pg. 178, Prob 4-93,

10. 10
2 2 2 2 2 2 2 2
2 2B t A t B t A t
e Ae e AeB B
52.Pg. 179, Prob 4-104
zu u
53.Pg. 185, P2, L8
Regarding the following sentence:
However, in nuclear reactions, the mass equivalence of the amount of energy
interacted is a significant fraction of the total mass involved.
It can easily be shown that even in nuclear reactions, the mass equivalence of the
amount of energy interacted is a small fraction of the total mass involved.
54.Pg. 188, FIGURE 5-8
m per unit mass =m/m=1 m per unit mass = m/ m=1
55.Pg. 190, EXAMPLE 5–1
56.Pg. 192, L4 from bottom of the page,
Note that pressure itself is not a form of energy
Note that pressure itself is not a form of energy but a measure of potential energy
stored per unit volume.
57.Pg. 194, EXAMPLE 5–17
1 1 1 1 2 20 0 atm atm atm atmV V p p p p p p p p
58.Pg. 206, EXAMPLE 5–5
…and thus 1V 0 compared to jV …and thus 1V is negligible compared to jV

11. 11
Note: If, for example, 1V 5and 2V 100
then 1V
is negligible compared to 2V
( we
cannot deduce that 1V 0
, because 1V 5
!)
Pg. 206, EXAMPLE 5–6
…and thus 1V 0 compared to jV
( the tank is very large relative to the outlet)
…and thus 1V
is negligible compared to jV ( the tank diameter is very large
relative to the outlet diameter)
59.Pg. 207,end parts of EXAMPLE 5–6
From conversion of mass From conservation of mass
60.Pg. 219, FIGURE 5-56
61.Pg. 221, EXAMPLE 5–11
…irreversibilities such as friction and swirling, and thus for reversible flow we
have…
irreversibilities such as friction and eddies, and thus for reversible adiabatic flow
we have…
and
62.Pg. 224
63.Pg. 227, left column, last P,
is the dynamic pressure, … is brought to a stop

12. 12
is the dynamic pressure, … is isentropically brought to a stop
64.Pg. 229, FIGURE P5–20
or
65. Pg. 262, FIGURE 6–32 and(Pg. 215, FIGURE 5–50 )
66.Pg. 323, Prob. 7-29,
67.Pg. 344, L1 after relation(8-10)
This phrase “dr, dx 0” is mathematically wrong, because by definition dr, dx are
themselves r , x 0, respectively.
Therefore, it is suggested to replace the first line after relation (8-10) by following
phrase:

13. 13
Considering and
68.Pg. 347, FIGURE 8–15
69.Pg. 347, relation (8-30)
70.Page352, FIGURE 8–21
The turbulent stress profile in practice is nearly vertical in the core region [since
the eddy motion is dominant in this region, and the effect of fluid viscosity is
negligible] and horizontal near the wall [due to viscose effects there], something
like this:
71.Page366, TABLE 8–4

14. 14
72.Page371, FIGURE 8–42
73.Page384, last P
Note that the pressure drop……not…..total pressure drop….
Note that the pressure drop……not…..total pressure loss….
It is suggested to make distinguish between the two terms “pressure drop” and
“pressure loss” by following definition:
“pressure drop” is caused by kinetic or potential energy conversion (kinetic or
potential energy increase) and it is recoverable, but “pressure loss” is caused by
viscosity and it is non-recoverable (or irreversible, and it is completely lost).
74.Page422, relation(9-6)
Note: In Taylor series, is a finite difference (not an infinitesimal difference).
75.Page424, FIGURE 9–6
76.Page425,426, regarding the paragraph after (9-10),

15. 15
From (9-10),
1 D
Dt and .v have the same order of magnitudes. Therefore it is
wrong to say:
“if changes in the density of the material element are negligibly small compared to
the magnitudes of the velocity gradients in .v as the element moves around,
1
0
D
Dt
, and the flow is approximated as incompressible.”
According to the relation
1
.
D
v
Dt (which is used as a criterion to see if a
flow is compressible or not), whenever .v is zero or near zero[ or identically
1 D
Dt
is zero or near zero ], the flow can be considered incompressible.
77.Page 427, P1 after relation(9-15)
It seems that this statement is wrong:
“If the flow is approximated as incompressible, density is not a function of time or
space. Thus
0
t in Eq. 9–5…”
Because when a flow is approximated as incompressible, it means that its material
derivative is zero,
1
0
D
Dt
, not 0
t
.
Very Important:
0
t i n steady state flows or in flows with homogeneous
density ( 0), i.e, when cte .
In incompressible flows
0
D
Dt , or equivalently . 0V
t
. That is,
.V
t (not 0
t
). Therefore, in incompressible flows, density could be a
function of time and space.
78.Page 438, FIGURE 9–26

16. 16
79.Page 443,(9-39)
or
80.Page 443,(9-41)
81.Page 443, FIGURE 9–33
gravity gravityF dF
82.Page 444,(9-42)

17. 17
or
83.Page 445,(9-49)
and in FIGURE 9–36,
84.Page 446, FIGURE 9–37

18. 18
85.Page 446, L1 after (9-52)
It seems that the following sentence is wrong!
“Hydrostatic pressure P in Eq. 9–52 is the same as the thermodynamic pressure”
Because hydrostatic pressure varies with depth, but thermodynamic pressure is a
function of temperature and doesn’t vary with depth, and …………….
86.Page 447, last paragraph, L3
Newtonian fluids, defined as fluids for which the shear stress is linearly
proportional to the shear strain rate.
Newtonian fluids, defined as fluids for which the stress tensor is linearly
proportional to the strain rate tensor.
Please note that in Newtonian fluids we have both linear and shear stresses (i.e.,
stress tensor, and the stress tensor is linearly proportional to the strain rate tensor).
87.Page 447, FIGURE 9–38,
Shear strain rate strain rate , Shear stress Stress , and
shear stress as a function of shear strain rate. Stress as a function of strain rate.
88.Page 447, last sentence of the page:
A fluid that returns (either fully or partially) to its original shape after the applied
stress is released is called viscoelastic.
A fluid that returns (partially) to its original shape after the applied stress is
released is called viscoelastic.
89.Page 462, FIGURE 9–61,

19. 19
Please see comment 84(regarding page 446, FIGURE 9–37)
90.Page 471, FIGURE 9–75,
Please see previous comment and:
/2 (on right face) and /2(on left face)
/ 2(on top face) and / 2(on bottom face)
and P=....
xr xr xr xr xr xr
rx rx rx rx rx rx
d d
d d
91.Page 473, L1 after relation(9)
the error function (Cengel, 2003) the error function
92.Page 476, Prob. 9-9,
Note:
2 3 2
2 and 3 ...dx xdx dx x dx
Also, dx= -0.1 x= -0.1 and f(x0+dx) f(x0+ x)
93.Page 493,
Relation (10-1) is not printed.
94.Page 495,second item under relation (10-6)
a)

20. 20
b)
* * * * *
( . ) and PV V in Eq. 10–6 are also order of magnitude unity
* *
* * *
( . ) and PV V in Eq. 10–6 are also of order of magnitude unity
95.Page 505, in relations (10-19), (10-20), the relation before (10-25), and relation
(10-26) and FIGURE 10–23 and FIGURE 10–26
0 0
96.Page 511, in FIGURE 10–33, is missed.
97.Page 514,L3
For example, if 1and 2 are …, then …. …A and B are arbitrary constants.
For example, if 1 and 2 are …, then 1 2A A C is …. …A and B ,C are
arbitrary constants.
98.Page 531, bottom of the page
CFO CFD
99.Page 535, EXAMPLE 10–9, L2 and in FIGURE 10–84
The line drawn isn’t chord line (The chord line is the straight line connecting
leading and trailing edges.).
100. Page 544, FIGURE 10–102
101. Page 555, in FIGURE 10–122(b)

21. 21
102. Page 560, in FIGURE 10–128 and in relation(10-89)
top topm dm
Since this is an infinitesimal or differential quantity.
103. Page 571, in Prob. 10-15C; I ,II, III, IV should be rearranged.
104. Page 779, FIGURE 14–28
Increasing velocity Increasing viscosity
105. Page 822, L6
steam turbines typically have two stages (high pressure and low pressure)
steam turbines typically have two sections (high pressure and low pressure) and
each section has multiple stages.
Note: Each stage is composed of one row of stator blades and one row of rotor
blades.

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