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A snapshot of the summary  Aerodynamics

1 Aerodynamics

1.1 Fundamental Equations

By which fundamental quantities can we characterize the flow?
 Pressure
 Velocity
 Temperature
 Density
And the derivatives of these quantities (changes in time) 
What are the three fundamental equations?
 Continuity equation
 Euler equation
 Bernouli equation
 Continuity equation

What is pressure and how can we describe it?The pressure is the norme force per unit area on a surface.

How can a perfect gas be described?A perfect gas is a gas in which intermolecular forces are negligible.

How can the equation of state be
approximated for anactual gas?By theBerthelot equation. 
When does the difference between the Berthelot equation and the equation of state become te smallest?The difference with the equation of state for a perfect gas becomes smaller as p decreases or T increases.
So when the distance between the molecules increases. 
Ex. 1Compute the temperature in a point on a wing of a Boeing 747, where pressure and density are given to be:
0.7 x 10^5 N/m2 and 0.91 kg/m3
(about3000m standard atmosphere)Perfect gass > P = ρRT
P = 0.7 x 10^5 N/m2
ρ = 0.91 kg/m3
R = 287.0 J/kg K
T = P / ( ρR)
T= 0.7 x 10^5 / (0.91 * 287) = 268.0 K 
What are the pressure, denisity and temperature at sea level / standard conditions?Ps = 1.01325*10^5 N/m2
ρs = 1.225 kg/m3
Ts = 288.15 K 
Ex. 2
Compute the total mass of air in a room of
30 m x 15 m x 5 m under standard atmospheric
conditions at sea level.
ρ = m / V
m = V * ρ
V = 30 x 15 x 5 = 2250 m3
ρ = 1.225 kg/m3
m = 2756 kg 
Ex. 3
Compute the density and specific volume of air in a wind tunnel at P = 1.0 bar, and 100 C.Pv = RT because
P = RTρ with ρ = 1 / v
P = 1*10^5 kg / m2
T = 100 + 273.15 = 173.15 K
R = 287.0 J/ kg K
v = RT / P
v = 287.0 * 173.15 / 101325 = 0.50 m3/kg
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