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Unformatted text preview: Uniﬁed Engineering
Fluids Quiz 1 (QF5) Fall 2003 Page 1/3 1. (30 %) A proposed winged blimp design ﬂies at some angle of attack �, and uses both
aerodynamic lift and aerostatic lift (buoyancy) to generate its total lift force L. The blimp
has a given shape, but its length c is as yet undecided. � c
a) In addition to the given � and c, list all the remaining physical parameters which signiﬁ
cantly inﬂuence L.
g (L, �, c, . . .) = 0
b) Determine a set of nondimensional parameters (or Pi products) which describe this situ
ation.
c) Identify the nondimensional parameter which determines whether or not the aerodynamic
force is signiﬁcant compared to the buoyancy force. Uniﬁed Engineering
Fluids Quiz 1 (QF5) Fall 2003 Page 2/3 2. (40 %) A toy rocket traveling at steady speed is propelled by a thin water jet with velocity
V1 and crosssectional area A directed ino the rocket’s open bottom end. The water then
p ours out of the b ottom at speed V2 . These velocities are as seen by an observer moving
alongside the rocket. V2
V1
A
a) Draw a suitable control volume for analyzing this ﬂow situation. Determine the mass and
momentum ﬂows for your chosen control volume.
b) What is the vertical thrust force imparted by the water? You may neglect the eﬀect of
gravity on the water velocities. Uniﬁed Engineering
Fluids Quiz 1 (QF5) Fall 2003 Page 3/3 3. (30 %) A 2D velocity ﬁeld is given by
u(x, y ) = x , v (x, y ) = −y a) Determine and sketch the streamline pattern.
b) Determine the circulation around the unitsquare curve shown (Note: This is curve is not
a streamline of this ﬂow) y
1 1 x ...
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 Fall '05
 MarkDrela
 Fluid Dynamics, Force, Aerodynamics, Lift, Airfoil, Fluids Quiz

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