Download If oil of specific gravity 0.9 and dynamic viscosity 9.6

The Islamic University of Gaza
Civil Engineering Department
Fluid Mechanics-Discussion
Autumn Semester (2011-2012)
Instructors:
Dr. Younes Mogheir
Dr. Mazen AbuAltayef
T.A.
Eng: Mohammed Abu Al-hatal
Eng: Amal Qarroot
Name: ……………………………………..……..……………
ID: …………………………..……..
Homework Chapter (4)
1) Water flow through a pipe 25mm in diameter at velocity of 6 m/s ,
determine whether the flow will laminar or turbulent assuming that
the dynamic viscosity of water is 1.3 * 10−3 Kg./m.s and its
density 1000 Kg/𝑚3 . If oil of specific gravity 0.9 and dynamic
viscosity 9.6*10−2 Kg./m.s is pumped through the same pipe ,
what type of flow will occur ?
2) The velocity distribution in a circular pipe of radius R is given by
𝑟2
V= 𝑉𝑚𝑎𝑥 ( 1- 2 ) , where V is the velocity at radius r , and 𝑉𝑚𝑎𝑥 is
𝑅
the velocity at the center , calculate the mean velocity?
3) If 70 liters of fuel oil are discharged from a tank 50 sec., find the
rate of discharge in 𝑚3 /s, if the discharge place through a pipe
50mm in diameter find the mean velocity of the oil in the pipe ?
4) If the mean velocity in a 30cm diameter id 0.5 m/s , what will be
the velocity in the jet 8cm diameter issuing from the nozzle
attached to the pipe ?
5) Two pipes provide a city with required volume of water which is
equal to 15000 𝑚3 daily , what is the minimum required diameter
to keep the velocity below 5m/s, what will be the diameter if one
pipe is used, compare the two diameter ?
6) An air duct is of rectangular cross- section 300mm wide by
450mm deep, determine the mean velocity in the duct when the
rate of flow is 0.42 𝑚3 /s , if the duct tapers to across- section
150mm wide by 400mm deep, what will be the mean velocity in
the reduce section assuming that the density remains unchanged ?
7) During test on a circular duct 2m diameter it was found that the
fluid velocity was zero at the duct surface and 6m/s on the axis of
the duct when the flow rate was 9 𝑚3 /𝑠. Assuming the velocity
distribution to be given by U=𝑐1 -𝑐2 𝑟 𝑛 , where u is the fluid
velocity at any radius, determine the values of the constant 𝑐1 , 𝑐2
and n, specifying the units of 𝑐1 𝑎𝑛𝑑 𝑐2 . Evaluate the mean
velocity and determine the radial position the mean velocity ?
8) Oil flows between parallel flat plates, which are distance t = 12mm
apart. The velocity of the oil has a maximum value of 0.5 m/s on a
plane midway between the plates and any distance y from this
plane the velocity is U = C(0.25 𝑡 2 - 𝑦 2 ). Calculate the volume rate
of flow per unit width measured perpendicular to the direction of
flow and also the mean velocity. At what distance from the surface
of the plates would the velocity be equal to the mean velocity ?
with best wishes ……..