2D and Subsonic Airflow

Question 1

What is Venturi’s principle?

Answer 1

Assuming an incompressible atmosphere, what goes in must come out. If we restrict the surface area, the speed of the mass flow must increase proportionally.

Question 2

What is the Mass Equation?

Answer 2

M = rho x V x A = constant

(Mass flow = density x speed x cross. Area)

Density and mass flow are assumed constant and thus speed must change inversely to the cross-sectional area

Question 3

What is Bernoulli’s principle?

Answer 3

Bernoulli’s principle compliments Venturi. If the speed of the air flow increases then the (static) pressure decreases. The (dynamic) pressure increases (relative to the aircraft).

Question 4

What is Bernoulli’s Equation?

Answer 4

Pt = q + Ps = Constant

Q= (rho/2 x V2) thus,

Pt = (rho/2 x V2) + Ps = constant

The total energy of an incompressible flow remains constant. If one goes up, the other goes down.

Question 5

What is deemed an “ideal” or incompressible airflow?

Answer 5

frictionless
steady
below 200kts/M0.3