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Exam 1 Questions | Fluid Mechanics | MEEN 3120, Exams of Fluid Mechanics

University of North Texas (UNT)Fluid Mechanics
Prof. Zhi-Gang Feng

Material Type: Exam; Professor: Feng; Class: Fluid Mechanics; Subject: Mechanical and Energy Engineering; University: University of North Texas; Term: Unknown 1989;

Typology: Exams

Pre 2010

Uploaded on 08/19/2009

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MEEN3120:FluidMechanicsExam#1 Name
1 | Page
Fluid Mechanics Exam #1 (Sample)
Close books and notes.
Shear Stress and Shear Force:

; 
Hydrostatic Forces on Plane Surfaces
ApF CG
= or AhF CG
γ
=(account only the gage pressure)
Center of Pressure CP [with respect to the Center of Gravity (CG)]:
Ah
I
Ap
I
y
Ah
I
Ap
I
x
CG
xx
CG
xx
CP
CG
xy
CG
xy
CP
θθγθθγ
sinsin,sinsin −=−=−=−=
Physical Properties of Water and Air:
Water at 20 oC:
Density, ρ=1000 kg/m3 = 1.94 slug/ft3
Viscosity, μ=0.001 kg/m.s=2.09x10-5 slug/ft.s
Constant
Standard acceleration of gravity:
22 /81.9/174.32 smsftg ==
0,
12
3
== xyxx I
bL
I
Conversion factors
1 m =3.28 ft; 1ft =12 inch; inch = 0.00254 m
1 liter =10-3 m3; 1 gallon=0.1337 ft3
1 Pstd=14.696 psi=2116.2 psf=1013 kPa= 1.013 bar
1 psi = 1 lbf/in2 = 144 lbf/ft2 =144 psf.=68.93 kPa
1 hp = 550 ft-lbf/s=746 W;
1 lbf=4.448 N=16 oz; 1 N = 1 kg. m/s2
1 mph = 1.4667 ft/s = 0.447 m/s.
pf3

Partial preview of the text

Download Exam 1 Questions | Fluid Mechanics | MEEN 3120 and more Exams Fluid Mechanics in PDF only on Docsity!

Fluid Mechanics Exam #1 (Sample)

Close books and notes.

Shear Stress and Shear Force : ߬ߤ ൌ ௗ௨ ௗ௬

Hydrostatic Forces on Plane Surfaces

F = pCG A or F = γ hCGA (account only the gage pressure)

Center of Pressure CP [with respect to the Center of Gravity (CG)]:

h A

I

p A

I

y h A

I

p A

I

x CG

xx CG

xx CP CG

xy CG

xy

CP =−γ^ sin^ θ =−sinθ , =−γsinθ =−sin^ θ

Physical Properties of Water and Air: Water at 20 o^ C: Density, ρ=1000 kg/m3 = 1.94 slug/ft^3 Viscosity, μ=0.001 kg/m.s=2.09x10-5^ slug/ft.s

Constant Standard acceleration of gravity: g = 32. 174 ft / s^2 = 9. 81 m / s^2 , 0 12

3 xx =^ Ixy^ =

bL I

Conversion factors 1 m =3.28 ft; 1ft =12 inch; inch = 0.00254 m 1 liter =10 -3^ m3; 1 gallon=0.1337 ft 3 1 Pstd =14.696 psi=2116.2 psf=1013 kPa= 1.013 bar 1 psi = 1 lbf/in 2 = 144 lbf/ft 2 =144 psf.=68.93 kPa 1 hp = 550 ft-lbf/s=746 W; 1 lbf=4.448 N=16 oz; 1 N = 1 kg. m/s^2 1 mph = 1.4667 ft/s = 0.447 m/s.

Part 1: Short answer questions (80 pts)

  1. A fluid is weighted in a laboratory. It is found that 1.49 gallons of the fluid weight 135 ounces. What is the fluid density in kg/m3? Is it likely water or gasoline?
  2. An expression describing the drag force experienced by an object moving through a fluid at

velocity V (its magnitude is V) is: ܨௗ ൌ ଵ ଶ ܸߩ^

ௗ. Here^ ρ^ is the fluid density; A is the cross section area perpendicular to the flow velocity. The constant Cd is the so-called drag coefficient. Determine the dimensions for constant C.

  1. Pipelines are cleaned by pushing through them a close-fitting cylinder called a pig. (The name comes from the squealing noise it makes sliding along). Suppose you want to design a nontoxic pig driven by compressed air for cleaning cosmetic and beverage pipes. The pig diameter is 5 5 ଵହ ଵ଺ in and its length 26 in. It cleans a 6-in diameter pipe at a speed of 1.3 m/s. If the clearance is filled with glycerin at 20o^ C, what the pressure difference, in Pascal, is needed to drive the pig? Assume a linear velocity profile in the oil and neglect air drag. (at 20 o^ C, glycerin viscosity μ=1.49 kg/m.s).
  2. Derive an expression for the capillary height change h, as shown, for a fluid of surface tension Y and contact angle theta between two parallel plates W apart.
  3. Calculate the hydrostatic pressure at point A in the oil based on the piezometer reading. Assume that the oil in the nozzle is not moving. Express the answer as gage pressure.
  4. A square cross section wooden (SG=0.6) rod, 5 cm by 5cm by 10 m long, floats vertically in water at 20oC when 6 kg of solid steel (SG=7.84) are attached to the lower end. How high above the water surface does the wooden end of the rod protrude?
  5. A strong wind has a velocity of 30 m/s. Given that the density of air is 1.2 kg/m3, estimate the force exerting on a 50 m^2 wall which is perpendicular to the wind.