An airfoil in a low-speed wind tunnel has a minimum pressure coefficient (Cp,0) of -0.5. Using the graphical method described in the chapter, this value would be used to plot which curve to find the critical Mach number?
Explanation
The critical Mach number for an airfoil can be estimated graphically by finding the intersection of two curves: 1) a universal curve of critical pressure coefficient versus Mach number (which is the same for all flows) and 2) a curve showing how the specific airfoil's minimum pressure coefficient changes with Mach number (calculated using the Prandtl-Glauert rule).
Other questions
What is the primary function of a swept-back wing on a subsonic aircraft?
In the context of airfoil nomenclature, what is the 'chord' of an airfoil?
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What is the primary cause of the phenomenon known as airfoil stall at high angles of attack?
For a thin airfoil in supersonic flow at a small angle of attack alpha, what is the approximate formula for the wave drag coefficient, cd,w?
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What is the 'critical Mach number' (Mcr) for an airfoil?
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For a finite wing with a general planform, the total drag coefficient (CD) is the sum of which two components, as shown in Equation (5.58)?
An NACA 23012 airfoil is at an angle of attack of 8 degrees. According to the data provided in the text for Example 5.6, what are the section lift and drag coefficients (cl and cd)?
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An airplane is flying at 100 meters per second at an altitude of 3 km. The pressure coefficient at a point on the fuselage is -2.2. Given that standard conditions at 3 km are p_inf = 7.0121 x 10^4 N/m^2 and rho_inf = 0.90926 kg/m^3, what is the absolute pressure at that point?
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For supersonic flow at Mach number M, what is the formula for the Mach angle, mu?
What is the primary aerodynamic advantage of using a 'supercritical airfoil' on a transonic aircraft?
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An airplane wing has an aspect ratio of 10 and a span efficiency factor (e) of 0.95. At a lift coefficient (CL) of 0.8, what is its induced drag coefficient (CD,i)?
The aerodynamic force on an airfoil can be resolved into components perpendicular and parallel to the chord line. What are these components called?
What is the primary purpose of deploying flaps on an airplane wing during takeoff and landing?
The first person to introduce the concept of a fixed-wing aircraft in 1799, separating the principles of lift and propulsion, was:
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For a finite wing with an elliptical lift distribution and an aspect ratio of 6, what is its induced drag coefficient (CD,i) when the lift coefficient (CL) is 0.5?
What is the defining characteristic of the 'aerodynamic center' of an airfoil?
Who were the first to bring order and logic to airfoil design in the United States with their 1933 report on 78 related airfoil sections and the introduction of the NACA four-digit series?
An airplane has a weight of 20,000 N, a wing area of 20 square meters, and is flying at an altitude where the air density is 1.0 kg/m^3. To achieve a lift coefficient of 0.5, what must its velocity be?
An airplane weighs 40,000 N, has a wing area of 20 square meters, and is flying at an altitude where the air density is 1.25 kg/m^3. To achieve a lift coefficient of 0.8 in level flight, what must its velocity be?
On a finite wing, the downward velocity component induced by the wing-tip vortices in the neighborhood of the wing is called what?
What was the designation of the first manned airplane to officially fly faster than the speed of sound?
How does increasing the aspect ratio of a subsonic wing generally affect its induced drag coefficient (CD,i) and its lift curve slope (a)?
A flat plate in supersonic flight at Mach 3 is at an angle of attack of 5 degrees. The lift coefficient is 0.123. What is its wave drag coefficient?
Who is credited with being the 'grandparent of the modern airfoil' for his pioneering work and patents on double-surface, cambered airfoils in 1884?
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What is the primary aerodynamic design consideration for supersonic wings that is different from subsonic wings?
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What is the purpose of the dimples on a golf ball?
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The X-15 hypersonic research aircraft had wings with a low aspect ratio of 2.5 and a thin airfoil section of 5 percent thickness. Why were these design features chosen?
What is the relationship between the zero-lift drag coefficient (CD,0) and the induced drag coefficient (CD,i) for an airplane flying at the velocity for maximum lift-to-drag ratio?
What fundamental principle of physics is violated by the 'equal transit time' theory of lift, which claims air particles must meet simultaneously at the trailing edge?
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Why does a swept-forward wing pose a greater structural challenge than a swept-back wing?
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What is the defining feature of a 'delta wing' airplane?
For a propeller-driven airplane, maximum range is achieved when which aerodynamic ratio is at its maximum?