The strakes are small wings placed upstream a main wing, that are used to modify the downstream vortical flow. A typical application is in agile aircraft (e.g. fighters). The strakes are one of those examples where the interference can be largely beneficial both from the aeodynamic point of view (lift) and control (effects on rolling and bending moments, see below). Similar effects can be achieved with a long leading edge extension (which makes a smooth wing-body combination).
Figure 1: Strakes
Flow Separation and Vortex Dynamics
Vortex formation (and buffeting) on a wing is a direct consequence of the strakes.
The vortices have a well defined and nearly steady structure in a wide range of
angles of attack.
Typical lift and rolling moment coefficients are shown in Fig. 2 and Fig. 3
at two different transonic Mach numbers.
Typical lift and rolling moment coefficients are shown in Fig. 2 and Fig. 3 at two different transonic Mach numbers.