4
1 The Experimental Approach in Aerodynamic Design
Fig. 1.3 Unmanned combat aircraft vehicle, nEUROn (© Dassault Aviation)
Table 1.1 Aerodynamic coefficients of civil transport aircraft
Cruise
Take off
C L
C D
L/D
C L
C D
L/D
Subsonic transport
0.50
0.027
18.5
1.50
0.130
11.5
Supersonic transport
0.12
0.012
10.0
0.40
0.045
8.9
characterises the flying quality of civil transport aircraft. At takeoff, high lift is sought
at the expense of drag, which is greatly increased; this reduces the lift-to-drag ratio.
In cruise flight, the drag is decreased without sacrificing the lift while operating near
the point of maximum lift-to-drag ratio.
Table 1.2 shows the drag coefficient, C D , of ground vehicles where the drag, D,
is normalised by the frontal area of the vehicle.
Figure 1.4 shows the evolution of the power dissipated by a road vehicle as a
function of speed on a horizontal road. The aerodynamic contribution appears to
be significantly larger than the contribution due to friction between the tyre and the
ground. From the figure on the right, the contribution from aerodynamics quickly
becomes paramount: at 50 km/h, 50% of losses are due to aerodynamic drag already,
and 85% at 130 km/h.
In rail transport, aerodynamics plays a key role in bringing high-speed trains into
service. Thus for these trains running at 300 km/h, the aerodynamic drag represents
80% of the resistance and the progression to the record speed of 575 km/h reached
in April 2, 2007 saw this drag increasing towards 90%. The significance of this
1 The Experimental Approach in Aerodynamic Design
Fig. 1.3 Unmanned combat aircraft vehicle, nEUROn (© Dassault Aviation)
Table 1.1 Aerodynamic coefficients of civil transport aircraft
Cruise
Take off
C L
C D
L/D
C L
C D
L/D
Subsonic transport
0.50
0.027
18.5
1.50
0.130
11.5
Supersonic transport
0.12
0.012
10.0
0.40
0.045
8.9
characterises the flying quality of civil transport aircraft. At takeoff, high lift is sought
at the expense of drag, which is greatly increased; this reduces the lift-to-drag ratio.
In cruise flight, the drag is decreased without sacrificing the lift while operating near
the point of maximum lift-to-drag ratio.
Table 1.2 shows the drag coefficient, C D , of ground vehicles where the drag, D,
is normalised by the frontal area of the vehicle.
Figure 1.4 shows the evolution of the power dissipated by a road vehicle as a
function of speed on a horizontal road. The aerodynamic contribution appears to
be significantly larger than the contribution due to friction between the tyre and the
ground. From the figure on the right, the contribution from aerodynamics quickly
becomes paramount: at 50 km/h, 50% of losses are due to aerodynamic drag already,
and 85% at 130 km/h.
In rail transport, aerodynamics plays a key role in bringing high-speed trains into
service. Thus for these trains running at 300 km/h, the aerodynamic drag represents
80% of the resistance and the progression to the record speed of 575 km/h reached
in April 2, 2007 saw this drag increasing towards 90%. The significance of this