 # Summary Aerodynamics

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Remember faster, study better. Scientifically proven. • ## 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?
1. Continuity equation
2. Euler equation
3. Bernouli 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 an actual gas?
By the Berthelot 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. 1
Compute 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
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