Enunciado

Consider a fl at-plate airfoil at an angle of attack of 68. The

Mach number is Ma

` 5 3.2 and the stream pressure p` is

unspecified. Calculate the predicted lift and drag coefficients

by (a) shock-expansion theory and (b) Ackeret theory

Passo 1

Saaaalve, tranquilo? Vamos lá resolver mais uma questão juntos?! 😊

a) Teoria de choque-expansão

Você precisa de um giro de choque na superfície 5 ∘ inferior e um giro 5 ∘ de expansão na superfície superior.

Passo 2

Calcule a força normal.

F   = ( 1.60 - 0.596 ) p ∞ b C   = 1.004 p ∞ b C

Aqui, p ∞ é a pressão. Calcule o coeficiente de força.

C F = F 1 / 2 k M a ∞   2 p ∞ b C

Aqui, é a F força normal, é k a constante, e é M a ∞ o número Mach.

C F   = 1.004 p ∞ b C 1 / 2 k M a ∞   2 p ∞ b C   = 1.004 1 / 2 k M a ∞ 2

Substituindo valores

C F   = 1.004 1 / 2 × × 1.4 × 3.2 2   = 0.14

Passo 3

Calcule o coeficiente de elevação.

C L = C F c o s ⁡ α

Substituindo valores

C L   = 0.14 × c o s ⁡ 6 ∘   = 0.139

Calcule o coeficiente de arrasto.

C D = C F s i n ⁡ α

Substituindo valores

C D   = 0.14 × s i n ⁡ 6 ∘   = 0.0146

Assim, os coeficientes de elevação e arrasto são 0.139 e 0.0146 .

Passo 4

b) Teoria de Ackeret Calcule o coeficiente de elevação.

C L = 4 α M a ∞ 2 - 1

Substituindo valores

C L   = 4 × 0.1047 3.2 2 - 1   = 0.138

Calcule o coeficiente de arrasto.

C D = C L α

Substituindo valores

C D   = 0.138 × 0.1047   = 0.0144

Assim, os coeficientes de elevação e arrasto são 0.138 e 0.0144 .

Resposta

a) C D = 0.0146

b) C L = 0.138   e   C D = 0.0144

Exercícios de Livros Relacionados

A sea-level smokestack is 52 m high and has a square crosssection. Its supports can withstand a maximum side forceof 90 kN. If the stack is to survive 90-mi/h hurricane winds,what is its maximum possi
For those who think electric cars are sissy, Keio University inJapan has tested a 22-ft-long prototype whose eight electricmotors generate a total of 590 horsepower. The “Kaz” cruisesat 180 mi/h (see
The Mars roving-laboratory parachute, in the Chap. 5opener photo, is a 51-ft-diameter disk-gap-band chute,with a measured drag coeffi cient of 1.12 [59]. Mars hasvery low density, about 2.9 E-5 slug/f
The AMTRAK Acela train passes through Kingston, RI, at130 mi/h, scaring all the villagers daily. Its total weight is624 short tons, with a rolling resistance Crr
It is diffi cult to defi ne the “frontal area” of a motorcycledue to its complex shape. One then measures the drag area(that is, CDA) in area units. Hoerner [12] reports the dragarea of a typical moto