The document discusses the transonic area rule, which was developed by Dr. Richard Whitcomb. The area rule states that two aircraft with the same longitudinal cross-sectional area distribution will experience the same wave drag, regardless of how area is distributed laterally. Whitcomb experimented with different axisymmetric bodies and wing-body combinations, finding that drag was directly related to changes in cross-sectional area from nose to tail. Applying the area rule involves narrowing the fuselage at the wing location to produce a smooth area distribution and reduce drag.
2. Transonic Area Rule
• Two airplanes with the same longitudinal cross-
sectional area distribution have the same wave
drag.
• It is independent of how the area is distributed
laterally.
• To avoid the formation of strong shock waves,
this total area distribution must be smooth.
• As a result, aircraft have to be carefully arranged
so that at the location of the wing, the fuselage is
narrowed or "waisted", so that the total area
does not change much.
4. Development of area rule
• Dr. Richard Whitcomb developed the area
rule.
• Whitcomb experimented with several
different axisymmetric bodies and wing-body
combinations in a transonic wind tunnel.
• What he found was that the drag created on
these shapes was directly related to the
change in cross-sectional area of the vehicle
from the nose to the tail.
5. Whitcomb area rule test models
(a) cylindrical fuselage
(b)fuselage with wings
(c) Bulged fuselage
(d)waisted fuselage with wings
7. • Wave drag is related to the second-derivative (or
curvature) of the volume distribution of the vehicle.
• Addition of wings to the basic cylinder produced twice
as much drag as the cylinder alone.
• Drag increased by the same amount if a simple bulge
were added to the cylinder, the bulge being of
equivalent volume as the wings.
• When the cross-sectional area of the fuselage is
reduced over the region were the wings are attached,
shown as body "D," the total drag was about the same
as that of the cylinder alone.
8. Conclusion
• Shaping the vehicle to create a smooth cross
sectional area distribution from the nose to the
tail could drastically reduce the drag on an
aircraft.
• The area rule tells us that the volume of the body
should be reduced in the presence of a wing, tail
surface, or other projection so that there are no
discontinuities in the cross-sectional area
distribution of the vehicle shape.
