ME111: Spring 2008
Exam #2
1
Key to Examination
#2
ME111 – FLUID MECHANICS
Spring 2008 – Section 01
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ME111: Spring 2008
Exam #2
2
1.
Define a
steady flow field
in the Eulerian reference frame.
In such a steady flow, is it possible for a fluid particle to
experience a nonzero acceleration?
Explain.
Yes, the fluid particle can experience a nonzero acceleration.
By definition, a steadyflow process is defined as a process during which a fluid flows through a control volume
steadily.
That is, the fluid properties can change from location to location within the control volume, but at any
location, they remain constant during the entire process.
(
)
V
V
V
V
∇
+
∂
∂
=
=
.
t
dt
d
on
Accelerati
The first term on the righthand side, called local acceleration, is zero for steady flow.
The second term, called the
advective (or convective) acceleration, can be nonzero even for steady flow.
It accounts for the effect of the fluid
particle moving to a new location in the flow, where the velocity field is different.
2.
Consider the following steady, twodimensional velocity field:
V
=
(0.5
+
1.2
x
)
i +
(
−
2.0
−
1.2
y
)
j
Is there a stagnation point in this flow field?
If so, specify its x and y coordinates.
A stagnation point is defined as a point in the flow field where the velocity is identically zero.
Since velocity
V
is a
vector, all of its components must be equal to zero in order for
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 Spring '08
 USaxena
 Fluid Dynamics, 1 m, 5 cm, steady flow, 0 m, 0.5 m

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