Basic Aerodynamics

The continuity equation, which describes the conservation of mass in a fluid flow, is derived from which fundamental physical principle?

Assuming an incompressible flow, if air enters a convergent duct with an inlet area of 6 square meters and a velocity of 15 meters per second, what is the exit area of the duct if the velocity at the exit is 60 meters per second?

What is the defining characteristic of an incompressible flow?

Below which Mach number can the flow of air generally be treated as incompressible, with density changes being less than 5 percent?

Bernoulli's equation, in the form p + (1/2)ρV^2 = constant, is applicable only to what type of flow?

Euler's equation is a differential relation that describes the motion of a fluid element in an inviscid flow. It relates an infinitesimal change in pressure (dp) to the density (ρ), velocity (V), and an infinitesimal change in which other property (dV)?

What does the first law of thermodynamics, δq + δw = de, express?

For a perfect gas, the thermodynamic property of enthalpy (h) is a function of which single variable?

An isentropic process is one that is defined as being both which two types of processes?

In a perfect gas, what single property does the speed of sound depend on?

Calculate the speed of sound for air at a temperature of 300 K. Assume the ratio of specific heats (γ) is 1.4 and the specific gas constant (R) is 287 J/(kg)(K).

The Mach number is a dimensionless quantity used to define different regimes of aerodynamic flows. How is it defined?

What is the term for a flow regime where the Mach number is less than 1?

What is the primary function of a Pitot tube in aerodynamics?

In an incompressible flow, the total pressure is equal to the sum of the static pressure and what other quantity?

Calculate the dynamic pressure (q) for an airflow with a density of 0.8 kg per cubic meter and a velocity of 300 meters per second.

According to the area-velocity relation for an isentropic flow, what must a subsonic flow (M < 1) do to increase its velocity?

According to the area-velocity relation for an isentropic flow, what must a supersonic flow (M > 1) do to increase its velocity?

To expand a gas from rest in a reservoir to supersonic speeds, what shape of duct must be used?

In a real, viscous flow, what is the velocity of the fluid right at the surface of a solid body due to the effects of friction?

The shear stress at the wall (τw) in a viscous flow is given by the product of the absolute viscosity coefficient (μ) and what other property of the flow?

What type of viscous flow is characterized by streamlines that break up and fluid elements moving in a random, irregular, and tortuous fashion?

When comparing laminar and turbulent boundary layers under the same flow conditions, which one results in a higher skin friction drag?

The transition from a laminar to a turbulent boundary layer on a surface is governed by a critical value of what dimensionless parameter?

Calculate the local Reynolds number for airflow at a point 0.2 meters from the leading edge of a flat plate. The flow conditions correspond to standard sea level (density = 1.225 kg per cubic meter, viscosity = 1.7894 x 10^-5 kg per meter second) and the velocity is 150 meters per second.

For an incompressible laminar boundary layer over a flat plate, how does the boundary layer thickness (δ) grow with distance (x) from the leading edge?

How does the growth rate of a turbulent boundary layer compare to that of a laminar boundary layer under the same flow conditions?

What is the term for a region in a flow where the pressure increases with distance along the flow, and what effect does it have on the boundary layer?

What are the two major aerodynamic consequences of flow separation over an airfoil, such as at a high angle of attack?

The energy equation for a frictionless, adiabatic flow, h + (1/2)V^2 = constant, can be written in terms of temperature (T) and velocity (V) for a perfect gas as:

What physical phenomenon occurs in a supersonic flow that causes the total pressure to decrease as the flow passes over an object?

An airplane is flying at an altitude where the ambient temperature is 220 K and the free-stream velocity is 800 m/s. What is the stagnation temperature on the leading edge of the wing? Assume air is a perfect gas with cp = 1008 J/(kg)(K).

What is the key difference between static pressure and total pressure in a moving fluid?

For a flow with heat addition, such as in a jet engine combustor, the energy equation is modified from its adiabatic form. What term is added to account for the heat?

An airplane is flying in conditions where the air density is 0.002 slug/ft^3. Its true airspeed is 400 ft/s. What is its equivalent airspeed if standard sea-level density is 0.002377 slug/ft^3?

How does the viscosity of a gas like air change with an increase in temperature?

For a laminar incompressible boundary layer on a flat plate, the local skin friction coefficient (cfx) is inversely proportional to what?

What is the reason that a laminar boundary layer is more prone to separation in an adverse pressure gradient than a turbulent boundary layer?

The total drag caused by viscous effects on an aerodynamic shape is the sum of which two components?

In his pioneering 1883 pipe flow experiments, what did Osborne Reynolds observe that indicated the transition from laminar to turbulent flow?

The area-velocity relation, dA/A = (M^2 - 1)dV/V, is derived by combining the continuity equation, the momentum equation, and the assumption that the flow is of what type?

A supersonic wind tunnel is designed to produce a Mach 2 flow in its test section. If the temperature in the test section is to be 250 K, what must the temperature in the reservoir (T0) be? Assume γ = 1.4.

What happens to the total temperature (T0) of a perfect gas as it flows isentropically through a convergent-divergent nozzle?

A jet is flying at an altitude where the ambient pressure is 26,500 N per square meter and the temperature is 223 K. A Pitot tube on the aircraft measures a pressure of 42,400 N per square meter. What is the flight Mach number? Assume isentropic, subsonic compressible flow and γ=1.4.

A vehicle is moving at 1000 m/s through the air at a temperature of 300 K. What is the Mach number of the vehicle? (γ=1.4, R=287 J/kg K)

What is the reason a turbulent boundary layer is more resistant to flow separation compared to a laminar one?

The local skin friction coefficient (cfx) for an incompressible turbulent flow over a flat plate is inversely proportional to what power of the local Reynolds number (Rex)?

How does increasing the free-stream Mach number (compressibility) affect the skin friction coefficient for a flat-plate boundary layer at a constant Reynolds number?

If the critical Reynolds number for transition on a flat plate is 500,000, and the plate is in a sea-level airflow (density = 1.225 kg/m^3, viscosity = 1.7894 x 10^-5 kg/(m s)) at a velocity of 50 m/s, at what distance from the leading edge will transition occur?

A low-speed subsonic wind tunnel has a test section velocity of 50 m/s, and the air conditions are standard sea level. A Pitot tube in the test section is connected to a pressure gauge. What pressure does the Pitot tube measure? (p_sea_level = 1.01325 x 10^5 N/m^2, rho_sea_level = 1.225 kg/m^3)