mditerms

Question 1

Various theories exist which can be used to determine aerodynamic
characteristics of airfoils in various shapes along a supersonic flow. The
simplest of these is known as____________

a linearized, first order
theory based on sweeping assumptions

Answer 1

Ackeret Theory

Question 2

Ackeret theory gives good results provided that the

Answer 2

Mach number is not too low and the airfoil section is not too thick

Question 3

the drag calculated using these theories are
confined only to the estimation of

Answer 3

the wave drag

Question 4

Characteristics of Supersonic Airfoil Sections

Answer 4

thinness
Sharp Leading Edge
Maximum thickness at half chord
Symmetry

Question 5

ex thinness

Answer 5

To minimize flow deviations due to thick airfoil sections which bring
about shock losses, a supersonic airfoil should be of thin cross
sections. However, this should be subject to the structural
requirements of the aircraft

Question 6

_____is necessary to keep an attached bow shock
wave on the airfoil section and to avoid losses due to a normal,
detached shockwave. This can be done by employing low thickness
to chord ratio to create a small leading edge angle which is
necessary to ensure shockwave attachment at low supersonic
speeds.

Answer 6

sharp leading edge

Question 7

ensures expansion behind the
maximum thickness point which is similar in value to the
compressions ahead of it and to illustrate that this is conducive to
low values of drag

Answer 7

Maximum Thickness at Half Chord

Question 8

The best wing section in theory for a supersonic flow is an

Answer 8

infinitely thin flat plate

Question 9

For a given thickness to chord ratio, minimum wave drag is achieved using
the

Answer 9

double wedge or diamond airfoil

Question 10

upper and
lower surfaces are formed by equal circular arcs

Answer 10

biconvex airfoils

Question 11

ackeret theory formula for coefficient of pressure

Answer 11

cpu = -2 thetha_net/ sqrt(M^2 - 1)
cpl = -2 thetha_net/ sqrt(M^2 - 1)

where expansion is positive and compression is negative

Question 12

Normal force coefficient formula

Answer 12

CN = 4 a/sqrt(M^2 - 1)

Question 13

cl formula

Answer 13

CL = CN for small angle of attack
cl = 4 a/sqrt(M^2 - 1)

Question 14

cd formula

Answer 14

Cd = 4a^2/sqrt(M^2 - 1)

= 1/4sqrt(M^2 - 1) (cl^2)

Question 15

lift to weight ratio

Answer 15

1/a

Question 16

Airfoil at Zero Degree Angle of Attack

Answer 16

𝐶𝑃1 = 𝐶𝑃2 = − −2𝛿/√𝑀∞^2 − 1
𝐶𝑃1 = 𝐶𝑃2 =2𝛿/√𝑀∞^2 − 1
𝐶𝑃3 = 𝐶𝑃4 = −2𝛿/𝑀∞^2 − 1

Question 17

Airfoil at Angle of attack 𝒂 < 𝛿
Consider the same double wedge ai

Answer 17

𝐶𝑃1 =2(𝛿 − 𝑎)/√𝑀∞^2 − 1
𝐶𝑃2 =2(𝛿 + 𝑎)/√𝑀∞^2 − 1
𝐶𝑃3 = −2(𝛿 + 𝑎)/√𝑀∞^2 − 1
𝐶𝑃4 = −2(𝛿 − 𝑎)/√𝑀∞^2 − 1

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Question 18

Airfoil at Angle of attack 𝒂 = delta

Answer 18

cp1 = 0
cp2 = 4a/√𝑀∞^2 − 1
cp3 = -4a/√𝑀∞^2 − 1
cp4 = 0

Question 19

Airfoil at Angle of attack 𝒂 > 𝛿

Answer 19

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