In
aerodynamics,
aerodynamic drag is the
fluid drag force that acts on any moving solid body in the direction of the fluid
freestream flow. From the body's perspective (near-field approach), the drag comes from forces due to pressure distributions over the body surface, symbolized
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=927)
, and forces due to skin friction, which is a result of viscosity, denoted
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=1158)
. Alternatively, calculated from the flowfield perspective (far-field approach), the drag force comes from three natural phenomena:
shock waves, vortex sheet, and
viscosity.