40 x 41f] cm square duct
P717 Air at 20°C and 1 atm enters a 40- Boundary layers
cm—square duct as in Fig. P17. Using the
“displacement thickness“ concept of Fig. 7.4.
estimate (a) the mean velocity a
5.15The wall shear stress w in a boundary layer is assumed to be a function of stream velocity
U, boundary layer thickness , local turbulence velocity u, density , and local pressure gradient
dp/dx. U
P4.2 Flow through the converging nozzle
in Fig. P42 can be approximated by the
one-dimensional velocity distribution
\
2 x
Hal/g[l+—
U 2 0 11‘ 2 0
X
(a) Find a general expression for the ﬂuid
accele
P4.43 For the draining liquid fihn of Fig.
P436. what are the appropriate boinldary
conditions (a) at the bottom is : 0 and (b) at
the s1u‘face_1-'= if?
Fig. P436
Solution: The physically realistic
This is a mistake in the solutions. Kerosene has a viscosity of 0.00192. A viscosity of 0.0192 is closer to
that of ethylene glycol, which has a viscosity of 0.0214.
2.149 The waterwheel in Fig. P2149 lifts
water with l-ft-dianleter half-cylinder
blades. The wheel rotates at 10 r/nn'n. What
is the water surface angle 6* at pt. A‘?
Solution: Convert Q = 10 Ifnlin =
2.86 The quarter circle gate BC in
Fig. P2.86 is hinged at C. Find the
horizontal force P required to hold the gate
stationary. The width E) into the paper
is 3 m. Neglect the weight of the gate.
So
P2.4 Pressure gages. such as the Bourdon gage
in Fig. P24= are calibrated with a deadweight piston.
Ifthe Bourdon gage is designed to rotate the pointer q
,_ cm
diameter
10 degrees for ever 2 psig o