Page 32 - Aerodynamics for Engineering Students

Basic concepts and definitions 15

and the entropy change from conditions 1 to 2 is given by

T2 PI
AS = S2 - SI = cvln-+ Rln- (1.29)
T1 P2
With the use of Eqn (1.14) this is more usually rearranged to be
T2
AS
-=ln-+((y- 1)ln- PI (1.30)
cv TI P2
or in the exponential form

(1.31)

Alternatively, for example, by using the equation of state,

(1.32)
These latter expressions find use in particular problems.

1.3 Aeronautical definitions

1.3.1 Wing geometry

The planform of a wing is the shape of the wing seen on a plan view of the aircraft.
Figure 1.4 illustrates this and includes the names of symbols of the various para-
meters of the planform geometry. Note that the root ends of the leading and trailing
edges have been connected across the fuselage by straight lines. An alternative to this
convention is that the leading and trailing edges, if straight, are produced to the
aircraft centre-line.

X CL

Fig. 1.4 Wing planform geometry