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4.9 - 98 Dynamics of an Incompressibie Inviscid Flow Field...

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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 re independent attitude only. 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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