Fuselage profile drag

Fuselage profile drag is considered as drag of an equivalent body of revolution. The amendments are entered for the account of fuselage design features which distinguish it from the body of revolution.

Factor of fuselage profile drag

(13.14)

where - profile drag of an equivalent body of revolution, which is determined as follows:

, (13.15)

where - friction drag coefficient of one side of a flat plate in an incompressible fluid flow at identical with the specified fuselage Reynolds number and coordinate of point in which laminar boundary layer becomes turbulent .

If to accept, that the fuselage is streamlined by completely turbulent flow (), that a little bit overestimate the drag, then

. (13.16)

The number is calculated on fuselage length and flight parameters and :

, , , .

The factors and in the formula (13.15) define the contribution of pressure forces and compressibility effect in fuselage profile drag:

or , . (13.17)

The ratio of the area of the lateral (wetted) fuselage surface to the area of midsection can be approximately calculated by the formula

. (13.18)

The account of fuselage design features is carried out by summing of additional drag factors .

The increment of the factor of fuselage profile drag caused by tail fairing or tapered rear part at subsonic speeds of flight is calculated by the formula

, (13.19)

If the jet stream outflows from the blunt base then , at absence of a jet stream . The factor depends on the shape of rear part generative line: for an ellipse , for other curves (particular case - hemisphere) . If tapering of the rear part then value of the factor .

Beveled or bended rear part causes an additional drag

(13.20)

where - angle of deflection of the rear part mean line, at , at .

The influence of canopy is estimated by such values:

- for a passenger or transport airplane ;

- for a manoeuvrable airplane ;

- the fairings of main landing gears located on the lateral fuselage surface increase drag on size ;

- side or ventral air intakes increase drag on size , where - summarized area of all air intakes.

Дата добавления: 2014-12-16