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Unformatted text preview: 98 Dynamics of an Incompressibie, Inviscid Flow Field Chap. 3 Relative drag lone Separation point (a) Flat plate broadside to the now (height = d). Red : 105 Separation point Skin friction drag component Pressure drag component (b) Large cylinder with subcriticel flow (diameter = d), Red = 105 v
(c) Streamlined body (thickness = d), Red = 105 Separation point M Same total drag (:1) Small cylinderwith subcrlticai ﬂow (diameter = 0.1d), Red = 105 Separation point (e) Large cylinder with supercrltical ﬂow (diameter = d), Red = 107 Figure 3.21 Comparison of the drag components for various shapes and ﬂows.
(From Ref. 3.4) Note that, for a conﬁguration of inﬁnite span, a force per unit span would be divided
by the reference area per unit span. Ideally, the force coefﬁcient would be independent of size and would be a function of conﬁguration geometry and of attitude only.
However, the effects of viscosity and compressibility cause variations in the force lWS. uld be divided
is in the force Sec. 3.14 Lift and Drag Coefficients as Dimensionless Flow-Field Parameters 99 coefﬁcients. These effects can be correlated in terms of parameters, such as the
Reynolds number and Mach number. Such variations are evident in the drag coefﬁ-
cient measurements presented in this chapter. From equation (3.53), it is clear that an aerodynamic force is proportional to the
square of the free-stream velocity, to the free—stream density, to the size of the object,
and to the force coefﬁcient. An indication of the effect of conﬁguration geometry on
the total drag and on the drag coefﬁcient is given in Figs. 3.21 and 3.22, which are taken
from Ref. 3.4. The actual drag for several incompressible ﬂow condition/conﬁguration Sonar-lion point m Fm pine brondsida lo the flow (height = :1). Re. = 10’ Saturation point (b) Luge cylinder with subcrincal flow (diam-tar = d), Re, = 105 Noam ic) Straomlined body llhlckness = d'l. lie, = 10’ Separation pom!
,, . (d) Smali cylinder with subcrincal ﬂow [diameter = Odd). R9, = 105 O
«.7 COO c. = 0.6 . . .
V Figure 3.22 Comparison of section drag ~_\—"'—— coefﬁcients for various shapes and ﬂows. (9) Large cylinder with supercvitical ﬂow (diameter = d). R3, = 10' (From Ref. 3.4) ...
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- Summer '07