Interference drag

[Omer Kandemir]

Hello,

In the wiki documentation (https://openvsp.org/wiki/doku.php?id=parasitedrag) it is stated that "Parasite drag is a combination of form, friction, and interference drag". But how does PDT accounts for interference drag? Is it somehow included in Form Factors? If so, how it changes when different methods used for the components that have interference?

Thank you for the answers in advance

[Luka Ranđelović]

Hi Omer,

interference drag is added with the Q factor in one of the last columns in the parasite drag tool.

You add it as an educated guess.

Here is info from Brandon Litherland from a previous post:

"The Q factors can also be found in Raymer under "Component Interference Factors" 

Copied from Raymer, "Aircraft Design", 2nd Ed. pp. 284-285: (excuse the OCR copy issues)

Parasite drag is increased due to the mutual interference between components.

For a nacelle or external store mounted directly on the fuselage or

wing, the interference factor Q is about 1.5. If the nacelle or store is

mounted less than about one diameter away, the Q factor is about 1. 3. If it

is mounted much beyond one diameter, the Q factor approaches 1.0. Wing

tip-mounted missiles have a Q factor of about 1.25. . .

For a high-wing, a mid-wing, or a well-filletted low wmg, the mterfere1:1ce

will be negligible so the Q factor will be about 1.0. An unfilletted low wmg

can have a Q factor from about 1.1-1.4. .

The fuselage has a negligible interference factor (Q = 1.0) m _most cases.

Also, Q = 1.0 for a boundary-layer diverter. For tail surfa~es, mterfer~nce

ranges from about three percent ( Q = 1.03) t:or a clean Y_-tatl to about eight

percent for an H-tail. For a conventional tail, four to five percent may be

assumed (Ref. 8)."

Kind regards,

Luka

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[Omer Kandemir]

Hi Luka,

Thank you!