AAE 334 EXAM 1 REVIEW QUESTYIONS WITH CORRECT ANSWERS LATEST UPDATE 2026
Blunt body and Slender body flow regime preferred? - Answers Slender body: Df >> Dp
Laminar flow is preferable for minimization of total drag
blunt body: Dp >> Df
Turbulent flow is preferable for minimization of total drag
Physical reason for downwash? - Answers Imbalance of pressure between upper and lower surfaces
of wing
Causes flow to "leak" upwards around wing tips
Causes creation of trailing vorticies
Induce downward component of air velocity along wing span
Physical reason for induced drag? - Answers lift vector aligned perpendicular to local wind direction
trailing vorticies induce downwash
tilts local wind direction from vinf
tilts lift vector and causes appearance of component of lift force in inf
mathematical expression justifying statement that induced drag is drag due to lift? - Answers Di = Li
sin(alpha)
how does downwash very spanwise? (elliptic loading distribution?) - Answers Downwash is constant
spanwise for elliptic loading disribution
What quantities must balance to make the camber line a streamline? - Answers The component of the
freestream velocity normal to the camber line must be balanced by the velocity induced by the vortex
sheet.
Why does a starting vortex appear when an airfoil starts from rest? - Answers Kelvins theorem:
circulation around a material curve is constant in inviscid flow
since circulation is initially zero, the circulation around the airfoil must be balanced by a starting
vortex of the opposite sign
What is the kutta condition for a finite-angle trailing edge? - Answers The kutta condition requires
that the velocity at a finite trailing edge be zero. It is a a stagnation point
Give two explanations of why an airfoil produces lift - Answers 1. low pressures on the upper surface
near the leading edge
2. momentum change resulting from the downward deflection of wake
3. net circulation around the airfoil
lift can be explained by: - Answers 1. circulation: faster flow on top vs bottom leads to pressure
differences
2. force: lower pressure on top (LE suction) and higher pressure on bottom lead to upward force
3. Acceleration: freestream is diverted down by airfoil, so it feels upward reaction
induced drag is caused by - Answers wake vorticity, induced downwash on the wing
leads to rotation of the lift vector, thus a component in the drag direction
for a cambered airfoil, where is the center of pressure when alpha = alpha zl - Answers center of
pressure is located at Xcp/c = 1/4[ 1+ pi/cl(A1-A2)]
cambered airfoil A1 =! 0 and A2 =! 0
so when alpha --> alpha zl and Cl --> 0 then Xcp/c --> infinity
SOOO center of pressure lies at infinity
what is the fundamental assumption of boundary layer theory? - Answers boundary layer is thin δ/L
<< 1
this condition occurs at high reynolds number
what is the physical meaning of displacement thickness? - Answers increment by which external
streamlines are deflected by the presence of the boundary layer.
body shape plus displacement thickness is the effective shape that the outer irrational flow sees.
what is downwash? - Answers velocity induced on the airfoil by the trailing vorticity in the wake
changes the effective angle of attack experienced by the airfoil
why does a starting vortex appear when an airfoil starts from rest? - Answers Kelvins theorem:
circulation around a material curve is constant in inviscid flow
since circulation is initially zero, circulation around the airfoil must be balanced by a starting vortex of
the opposite sign
Blunt body and Slender body flow regime preferred? - Answers Slender body: Df >> Dp
Laminar flow is preferable for minimization of total drag
blunt body: Dp >> Df
Turbulent flow is preferable for minimization of total drag
Physical reason for downwash? - Answers Imbalance of pressure between upper and lower surfaces
of wing
Causes flow to "leak" upwards around wing tips
Causes creation of trailing vorticies
Induce downward component of air velocity along wing span
Physical reason for induced drag? - Answers lift vector aligned perpendicular to local wind direction
trailing vorticies induce downwash
tilts local wind direction from vinf
tilts lift vector and causes appearance of component of lift force in inf
mathematical expression justifying statement that induced drag is drag due to lift? - Answers Di = Li
sin(alpha)
how does downwash very spanwise? (elliptic loading distribution?) - Answers Downwash is constant
spanwise for elliptic loading disribution
What quantities must balance to make the camber line a streamline? - Answers The component of the
freestream velocity normal to the camber line must be balanced by the velocity induced by the vortex
sheet.
Why does a starting vortex appear when an airfoil starts from rest? - Answers Kelvins theorem:
circulation around a material curve is constant in inviscid flow
since circulation is initially zero, the circulation around the airfoil must be balanced by a starting
vortex of the opposite sign
What is the kutta condition for a finite-angle trailing edge? - Answers The kutta condition requires
that the velocity at a finite trailing edge be zero. It is a a stagnation point
Give two explanations of why an airfoil produces lift - Answers 1. low pressures on the upper surface
near the leading edge
2. momentum change resulting from the downward deflection of wake
3. net circulation around the airfoil
lift can be explained by: - Answers 1. circulation: faster flow on top vs bottom leads to pressure
differences
2. force: lower pressure on top (LE suction) and higher pressure on bottom lead to upward force
3. Acceleration: freestream is diverted down by airfoil, so it feels upward reaction
induced drag is caused by - Answers wake vorticity, induced downwash on the wing
leads to rotation of the lift vector, thus a component in the drag direction
for a cambered airfoil, where is the center of pressure when alpha = alpha zl - Answers center of
pressure is located at Xcp/c = 1/4[ 1+ pi/cl(A1-A2)]
cambered airfoil A1 =! 0 and A2 =! 0
so when alpha --> alpha zl and Cl --> 0 then Xcp/c --> infinity
SOOO center of pressure lies at infinity
what is the fundamental assumption of boundary layer theory? - Answers boundary layer is thin δ/L
<< 1
this condition occurs at high reynolds number
what is the physical meaning of displacement thickness? - Answers increment by which external
streamlines are deflected by the presence of the boundary layer.
body shape plus displacement thickness is the effective shape that the outer irrational flow sees.
what is downwash? - Answers velocity induced on the airfoil by the trailing vorticity in the wake
changes the effective angle of attack experienced by the airfoil
why does a starting vortex appear when an airfoil starts from rest? - Answers Kelvins theorem:
circulation around a material curve is constant in inviscid flow
since circulation is initially zero, circulation around the airfoil must be balanced by a starting vortex of
the opposite sign
