Editing Parasitic drag (section)

==Form drag==
'''Form drag''' arises because of the [[shape]] of the object. The general size and shape of the body are the most important factors in form drag; bodies with a larger presented cross-section will have a higher drag than thinner bodies; sleek ("streamlined") objects have lower form drag. Form drag follows the [[drag equation]], meaning that it increases with the square of the velocity, and thus becomes more important for high-speed aircraft.

Form drag depends on the longitudinal section{{what|date=November 2022}} of the body. A prudent choice of body profile is essential for a low [[drag coefficient]]. [[Streamlines, streaklines, and pathlines|Streamlines]] should be continuous, and [[Flow separation|separation of the boundary layer]] with its attendant [[vortex|vortices]] should be avoided.

Form drag includes interference drag, caused by the mixing of airflow streams. For example, where the [[wing]] and fuselage meet at the wing root, two airstreams merge into one. This mixing can cause eddy currents, turbulence, or restrict smooth airflow. Interference drag is greater when two surfaces meet at perpendicular angles, and can be minimised by the use of [[Aircraft fairing|fairings]].<ref>{{Cite web|url=https://www.skybrary.aero/index.php/Interference_Drag|title = Interference Drag - SKYbrary Aviation Safety| date=25 May 2021 }}</ref><ref>{{Cite web|url=https://www.boldmethod.com/learn-to-fly/aerodynamics/how-interference-drag-affects-your-airplane-performance-and-decreases-performance/|title=How Interference Drag Affects Your Plane's Performance}}</ref><ref name="PHAK"/>

[[Wave drag]], also known as supersonic wave drag or compressibility drag, is a component of form drag caused by [[shock wave]]s generated when an aircraft is moving at [[transonic]] and [[supersonic]] speeds.<ref name="Anderson"/>{{rp|25, 492, 573}}

Form drag is a type of pressure drag,<ref name="Anderson"/>{{rp|254}} a term which also includes lift-induced drag.<ref name="Anderson"/>{{rp|65, 319}} Form drag is pressure drag due to separation.<ref name="Anderson" />{{rp|641-642}}<ref name="Anderson Introduction"/>{{rp|256}}