Investigation of Transonic Drag Computations in Aerodynamic ...

Investigation of Transonic Drag Computations in APAS
important factor in the conceptual design of an RLV, thus the ability to accurately
calculate and understand transonic drag effects becomes important.
2.0 Transonic Drag and Wave Drag Theory
The drag rise that occurs as a vehicle nears the speed of sound is caused by the
development and presence of shock waves that result in wave drag. Figure 1 shows the
development of local shock waves which lead to a Mach wave as the sound barrier is
broken. Local shock waves begin to develop on certain parts of an aircraft as the
freestream Mach number approaches 0.85-0.9.
Mach Wave
U inf
M ~ .7 M ~ 1.1
Figure 1. Shock Wave Development
These shock waves and the resulting shock induced boundary layer are the biggest
contributors to transonic drag. The drag continues to increase in magnitude until the flow
is fully supersonic, at which point it begins to taper off. This behavior can be seen in
Figure 2, which shows a typical transonic drag rise.
Jeff Miller 2