課程名稱︰流體力學
課程性質︰大二必修
課程教師︰陳瑤明
開課學院：工學院
開課系所︰機械系
考試日期（年月日）︰2008.Apr.25
考試時限（分鐘）：110 min
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
1.
(a) Express the Bernoulli equation in the way using "Heads" and discuss the
major assumptions of this equation.
(b) What's Kinetic energy correction factor? When is it significant?
(c) Explain the importance of the Reynold transprot theorem and describe how
the linear momentum equation is obtain from it.
2.
Air is flowing through a venture meter whose diameter is 4.2 in at the
enterance part (location 1) and 2.8 in at the throat (location 2). The gage
pressure is measured to be 16.8 psia at the enterance and 15.2 psia at the
throat. Neglecting frictional effects, show that the volume flow rate can be
expressed as
╭ ╮(1/2)
. │ 2(P1-P2) │
V = │────────────── │
│ ρ(1-((A2)^2/(A1)^2)) │
╰ ╯
and determine the flow rate of air. Take the air density to be 0.078 lbm/ft^3.
3.
A ruducing elbow is used to deflect water flow at a rate of 38 kg/s in a
horizontal pipe upward by angle θ=40° from the flow direction while
accelerating it. The elbow discharge water into the atmosphere.
The cross-section area of the elbow is 160 cm^2 at the inlet and 40 cm^2
at the exit. The elevation difference between the center of exit and the inlet
is 45 cm. The mass of the elbow and water in it is 55 kg. Determine the
anchoring force needed to hold the elbow in place. Take the momentum-flux
correction factor to be 1.04.
4.
Consider a centrifugal blower that has a radius of 22 cm and a blade width of
8.4 cm at impeller inlet, and a radius of 48 cm and a blade width of 5.8 cm at
the outlet. The blower delivers air at a rate of 0.79 m^3/s at a rotational
speed 900 rpm. Assuming the air to enter the empeller in radial direction and
to exit at an angle of 50 °from the radial direction, determine minimum power
consumption of the blower. Take the density of the air to be 1.22 kg/m^3.
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