Bernoulli and his Principal of AirflowBernoulli and his Principal of AirflowBernoulli and his Principal of AirflowBernoulli and his Principal of Airflow

Within any confined system, total energy Within any confined system, total energy remains constant. If one component of energy remains constant. If one component of energy increases, there must be a corresponding increases, there must be a corresponding decrease in other components.decrease in other components.

Within any confined system, total energy Within any confined system, total energy remains constant. If one component of energy remains constant. If one component of energy increases, there must be a corresponding increases, there must be a corresponding decrease in other components.decrease in other components.

Total pressure within the confined system is Total pressure within the confined system is the summation of static and dynamic pressurethe summation of static and dynamic pressureTotal pressure within the confined system is Total pressure within the confined system is the summation of static and dynamic pressurethe summation of static and dynamic pressure

Venturi TubeVenturi TubeVenturi TubeVenturi Tube

The The volumevolume of air passing any given point per unit of of air passing any given point per unit of time is equal throughout the tube. time is equal throughout the tube. The The volumevolume of air passing any given point per unit of of air passing any given point per unit of time is equal throughout the tube. time is equal throughout the tube.

This is known as This is known as MASS FLOW RATEMASS FLOW RATEThis is known as This is known as MASS FLOW RATEMASS FLOW RATE

(subsonic, incompressible flow)(subsonic, incompressible flow)(subsonic, incompressible flow)(subsonic, incompressible flow)

As air velocity increases, As air velocity increases, static pressure decreases, static pressure decreases, dynamic pressure increasesdynamic pressure increases

Slow velocity of air with Slow velocity of air with equal static and equal static and dynamic pressuresdynamic pressures

Slow velocity of air with Slow velocity of air with equal static and equal static and dynamic pressuresdynamic pressures

AirfoilAirfoilAirfoilAirfoilLets take half of that venturi tube and see what happens Lets take half of that venturi tube and see what happens when we move air across the shape when we move air across the shape Lets take half of that venturi tube and see what happens Lets take half of that venturi tube and see what happens when we move air across the shape when we move air across the shape

Lets assume there is no upper Lets assume there is no upper physicalphysical limit of the tube limit of the tubeLets assume there is no upper Lets assume there is no upper physicalphysical limit of the tube limit of the tube

The flow closest to the airfoil conforms to the shape of theThe flow closest to the airfoil conforms to the shape of theairfoil while the air farthest from the airfoil remains horizontalairfoil while the air farthest from the airfoil remains horizontaland and actsacts like the upper surface of the venturi like the upper surface of the venturi

The flow closest to the airfoil conforms to the shape of theThe flow closest to the airfoil conforms to the shape of theairfoil while the air farthest from the airfoil remains horizontalairfoil while the air farthest from the airfoil remains horizontaland and actsacts like the upper surface of the venturi like the upper surface of the venturi

How is most of the lift produced?How is most of the lift produced?How is most of the lift produced?How is most of the lift produced?

= 9= 9= 9= 9Static = 1Static = 1Dynamic = 8Dynamic = 8Static = 1Static = 1Dynamic = 8Dynamic = 8

Static = 4Static = 4Dynamic = 7Dynamic = 7Static = 4Static = 4Dynamic = 7Dynamic = 7= 11= 11= 11= 11

= 10= 10= 10= 10Static = 5Static = 5DynamicDynamic = 5= 5Static = 5Static = 5DynamicDynamic = 5= 5

Static = 4Static = 4Dynamic = 6Dynamic = 6Static = 4Static = 4Dynamic = 6Dynamic = 6= 10= 10= 10= 10

Low Pressure AreaLow Pressure AreaLow Pressure AreaLow Pressure Area

High Pressure AreaHigh Pressure AreaHigh Pressure AreaHigh Pressure Area

High seeks LowHigh seeks LowHigh seeks LowHigh seeks Low

Since air has a greater distance to travel over the upper surface there is Since air has a greater distance to travel over the upper surface there is a greater velocity increase and pressure decrease over the upper a greater velocity increase and pressure decrease over the upper surface than the lower surface. The higher pressure below the airfoil surface than the lower surface. The higher pressure below the airfoil seeks the lower pressure above causing the airfoil to move up.seeks the lower pressure above causing the airfoil to move up.

Since air has a greater distance to travel over the upper surface there is Since air has a greater distance to travel over the upper surface there is a greater velocity increase and pressure decrease over the upper a greater velocity increase and pressure decrease over the upper surface than the lower surface. The higher pressure below the airfoil surface than the lower surface. The higher pressure below the airfoil seeks the lower pressure above causing the airfoil to move up.seeks the lower pressure above causing the airfoil to move up.

If the differential in pressures produces If the differential in pressures produces mostmost of of the lift, what is producing the the lift, what is producing the restrest of the lift? of the lift?If the differential in pressures produces If the differential in pressures produces mostmost of of the lift, what is producing the the lift, what is producing the restrest of the lift? of the lift?

QuestionQuestionQuestionQuestion

The remaining lift is a result of Newton’s third law of motion,The remaining lift is a result of Newton’s third law of motion,The remaining lift is a result of Newton’s third law of motion,The remaining lift is a result of Newton’s third law of motion,

ActionActionActionAction andandandand ReactionReactionReactionReaction

Questions?Questions?Questions?Questions?