課程名稱︰流體力學
課程性質︰機械系必修
課程教師︰陳瑤明
開課學院：機械系
開課系所︰機械系
考試日期（年月日）︰2007.4.27
考試時限（分鐘）：兩小時
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
1.
Please answer the following questions:
1.1 What is continuum? Under what condition a substance can be treated as a
continuum?(10%)
1.2 What is the momentum-flux correction factor? For which type of flow is
it significant: laminar flow or turbulent flow?(10&)
2.
Derive the conservation for linear momentum and angular momentum using the
Reynolds transport theorem.(20%)
3.┌──────╢
∣ │ ║←sluice gate
V1∣ │y1 ║
→∣ │ ╙───────
∣ │ │y2 V2→
└─────────────
A sluice gate, which controls flow rate in a channel by simply raising
or lowering a vertical plate, is commonly used in irrigation systems.
A force is exerted on the gate due to the difference between the water
heights y1 and y2 and flow velocity V1 and V2 upstream and downstream
from the gate,respectively. The water density is ρ. Disregarding the wall
shear forces at the channel surfaces, develop relations for V1,V2 and
the force acting on a sluice gate of width w during steady and uniform flow
(20%)
4.
A lawn sprinkler with three identical arms is used to water a garden by
rotating in a horizotsal plane by the impulse caused by water flow.
Water enters the sprinkler along the axis of rotation at a rate of 40L/s
and leaves the 1.2cm diameter nozzles in the tangential direction.
The bearing applies a retarding torque of T=50(N*m) due to friction at
the anticipated operating speeds. For a normal distance of 40cm between
the axis of rotation and the center of the nozzles, determine the angular
velocity of the sprinkler shaft. (20%)
5.
A tank of 0.1(m^3) volume is connected to a high-pressure air line; both
line and tank are initially at a uniform temperature of 20(度C).The initial
tank gage pressure is 100kPa. The absolute line pressure is 2.0MPa; the
line is large enough so that its temperature and pressure may be assumed
constant. The tank temperature is monitored by fast-response thermocouple.
At the instant after the valve is opened, the tank temperature rises at
the rate of 0.05(度C/s). Determine the instantaneous flow rate of air into
the tank if heat transfer is neglected. (20%)
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