In order for a flow to be isentropic, it must be what?
Adiabatic and reversible.
The speed of sound in a gas increases with decreasing temperature.
False; it decreases as well because $ a = \sqrt{\gamma R T} $!
The characteristic speed of sound is reached by varying the flow Mach number until it reaches what?
1
If you were to rank gases from lowest to highest speed of sound at the same temperature, how would you rank (A) air, (B) carbon-dioxide, (C) helium, and (D) sulfur hexafluoride?
C > A > B > D
What is constant across a normal shock?
Total temperature ($T_0$)
Is a normal shock adiabatic?
Yes!
What flow parameters increase across a normal shock?
Static temperature, static pressure, static density, and speed of sound.
As the mach number downstream a normal shock increases, how does the mach number upstream change?
It decreases.
As air temperature rises, a normal shock produces more or less total pressure loss?
More.
When is an incoming flow's Mach considered to be the critical Mach number?
When there is a point along the airfoil where the flow first reaches sonic (M = 1) conditions.
Rayleigh flow can be modeled as what?
Incompressible and inviscid.
To mitigate total pressure loss in a subsonic combustor, when should heat be added?
At the low, subsonic M.
Which flow properties increase when heat is added in supersonic Rayleigh flow?
Static temperature, static pressure, static density, and total temperature.
If you had a vacuum cleaner hose in a large room with ambient pressure of 1 atm and ambient temperature of 288 K, how does the static pressure at the hose tip compare to $ P_{amb} $?
In this case, $ P_{amb} $ is actually $ P_0 $, so the static pressure at the hose tip is: $ P < P_0 = 1 $ atm.
Which properties decrease for a subsonic Fanno Flow?
Static temperature, static pressure, static density, and total pressure.
How does skin friction in pipe flow change as Reynolds number decreases?
It increases.
For liquids, how does viscosity change as temperature increases?
It decreases.
For gases, how does viscosity change as temperature increases?
It increases.
As Mach number decreases, the Mach wave angle does what?
It increases.
Given a wedge half-angle, how does Mach number affect the oblique shock angle?
As Mach number increases, the oblique shock angle will decrease.
If a wedge half-angle is greater than the maximum half-angle for an oblique shock solution, what happens?
A bow shock (or normal shock) forms in front of the wedge.
How does the total pressure loss compare in an oblique shock and a normal shock for the same incoming Mach number?
The total pressure loss is lower for an oblique shock.
Which values are constant through an expansion fan?
Total temperature and total pressure.
For a 2D inviscid flow around a symmetric airfoil at 0° angle of attack, is the lift coefficient or the drag coefficient 0?
The lift coefficient is zero because the coefficient of pressure is mirrored across the symmetric airfoil. As for drag, there is a larger pressure in front of the airfoil than in the back, so pressure drag is non-zero!
Supersonic flow always does what in a converging nozzle?
It decreases.
Assume $ \gamma = 1.4 $, air flowing through a converging-diverging nozzle will choke at the throat as long as the nozzle pressure ratio is what?
Greater than 1.89.