aero midterm Flashcards
Temperature is a measure of the average ______ energy of the particles in a gas
kinetic
A perfect gas is one in which intermolecular forces are negligible.
True
the equation of state for a perfect gas is given by…
p = rhoRT
What are the sources of aerodynamic forces acting on a body
pressure distribution and shear stress distribution over the surface
In isothermal regions of the standard atmosphere, temperature s said to change as altitude changes
False
in both the gradient and isothermal regions of the standard atmosphere, the pressure ____ with an increase in altitude
decreases
The continuity equation for steady fluid flow states that
rho1A1V1 = rho2A2V2
For incompressible flow
rho1 = rho2
You are given a convergent duct for which the inlet area A1 is greater than the outlet area A3. Assuming that flow in this duct is incompressible, the velocity of the flow will _____ as it moves through the duct.
increase
An inviscid flow is one that is frictionless
true
An isentropic process is one that is both adiabatic and reversible. Thus, an isentropic process is one in which there is _____ .
neither heat exchange nor any effects due to friction
the speed of sound in a perfect gas depends only on the temperature of the gas.
true
Mach number is the ratio of the flow velocity to the speed of sound. If a flow has M = 1, the flow is said to be ____ .
sonic
Consider a subsonic wind tunnel with a typical upstream-to-downstream arrangement consisting of a reservoir, nozzle, test section, and diffuser. In such a wind tunnel, the test section pressure is ______ than the reservoir pressure.
smaller than
In a subsonic wind tunnel, a manometer is used to measure the _____ difference between the nozzle and test section.
pressure
The ____ at a given point in a flow is the pressure that would exist if the flow were slowed down isentropically to zero velocity.
total pressure
A pressure gauge connected to a pitot static probe measures the difference between the ____.
total and static pressure
Flow speeds below M = 0.3 are
incompressible
Flow speeds above M = 0.3 are
compressible
shock waves are very thin regions of the flow across which some severe changes in the flow properties take place. Assuming that the perfect gas assumption exists, as a fluid element flows through a shock wave, the total temperature T0 _____.
stays the same
Consider an airplane flying at some true airspeed at some altitude. It’s equivalent airspeed at this condition is defined as the velocity at which it would have to fly at standard sea level to experience the dame dynamic pressure.
True
The area velocity relation states that, for supersonic flows (M>1), the cross sectional area must _____ for the velocity to increase.
increase
Flow speeds below Mach 0.3 are typically treated as incompressible because the ____ is essentially constant at these speeds.
density
flow that consits of friction is known as _____ flow
viscous
flow that consists of friction is known as _____ flow
viscous
The flow in a boundary layer consists of a velocity profile which exhibits a change in flow velocity between the object’s surface and the outer edge of the boundary layer. Let the velocity at the surface be given by V1 and the velocity at the outer edge of the boundary layer be given by V2. Which of the following describes the velocity profile in the boundary layer?
V1 < V2
Consider viscous flow over a flat plate. As the air flows across the surface from the leading edge to the trailing edge (ie. front to back), one would expect the thickness of the boundary layer to _______.
increase
Laminar flow is one in which the streamlines break up and a fluid element moves in a random, irregular, and tortuous fashion.
False
Consider viscous flow over a surface. The flow in the boundary layer may be categorized as laminar or turbulent. The presence of fiction creates a shear stress at the surface tau-w . Let tau-w-laminar represent this shear stress in the case of laminar flow and tau-w-turbulent represent this shear stress in the case of turbulent flow. Which of the following is accurate?
tau-w-laminar < tau-w-turbulent
Under the same flow conditions, a turbulent boundary layer will be thicker than a laminar boundary layer.
True
Consider a flat plate boundary layer in a compressible flow. In such a case, for a constant Reynolds number, the effect of increasing the freestream Mach number M_inf is to _______ the local skin friction coefficient c_f_x.
decrease
The major consequences of flow separation over an airfoil are _______ .
a large decrease in lift and a large increase in drag
In the presence of an adverse pressure gradient, fluid elements along a streamline within the boundary layer tend to _______ .
slow down
Skin friction drag is caused by flow separation at the surface of the object.
False
Pressure drag due to separation can be reduced by establishing a turbulent boundary layer on the surface.
True
The lift of an airfoil L is always defined as the component of the aerodynamic force _______ to the _______.
perpendicular/ relative wind
The normal and axial forces of an airfoil may be related to the lift and drag of the airfoil through the angle of attack.
True
The moment coefficient c_m is obtained by dividing the moment M by which of the following?
q_infSc
The lift slope is given by the slope of the linear portion of a plot of:
cl vs alpha
A positively cambered airfoil will have a non-zero value of cl at zero angle of attack.
true
At some angle of attack larger than that corresponding to cl_max , the flow around an airfoil typically remains attached.
False
At high subsonic Mach numbers in a flow, the associated compressibility effects have no influence on the low-speed pressure coefficient.
False
Consider a flat plate at a positive angle of attack in a flow field with freestream velocity of M_inf > 1. At the leading edge on the upper surface of this flat plate, one would observe a/an _______ .
expansion wave
At subsonic speeds below the drag-divergence Mach number, one would expect to have a significant amount of wave drag.
false
For values of Mach number between M = M_dragdivergence and M = 1 , one would expect _______ in the drag coefficient cd.
an increase
The only two sources of Aerodynamic forces on a body are
Pressure and Shear Stress
Total Pressure is the pressure you would feel if you were traveling along with a fluid element in a flow
False
Static Pressure is the pressure you would feel if you were traveling along with a fluid element in a flow
True
Compressible flows that are isentropic (adiabatic and reversible) have constant static temperatures throughout the flow since both heat addition and friction are ignored
False
As altitude increases in the troposphere below the tropopause, the speed of sound
decreases
At sea level, the true and equivalent velocities are equal
True
Assuming compressible, steady, isentropic flow, and a constant mass flow rate, if the flow entering a duct is supersonic, to decrease its velocity, you must ____ the area along the direction of the flow.
decrease
when you have achieved choked flow in the throat of a nozzle you can continue to increase the mass flow rate by continuing to decrease the pressure at the exit of the nozzle.
False
The equation of state for an ideal gas states the relationship between pressure, temperature, and density of an ideal gas at different points in the same flow
false
The assumptions used to derive both Bernoulli’s Equation and the energy equation result in both total pressure and total temperature being constant along a streamline.
True
Aerodynamics is defined as the science that deals with the transfer of energy
False
Pressure is a scalar quantity and can be defined in cartesian space by one component
True
velocity is just another word for speed; there is no technical difference between them.
False
The static pressure at a given point is the pressure we would feel if the flow were brought isentropically to rest at that point.
False
The conservation of momentum is another form of Newton’s Second Law of motion
True
The velocity always increases in a convergent nozzle
False
Because there is no heat transfer in an isentropic process, the temperature of the flow must remain constant everywhere in the flow.
False
The total pressure and total temperature remain constant across a shock wave.
False (total pressure decreases)
