AERODYNAMICS

Question 1

“the property of fluid to resist shearing stress”

Answer 1

VISCOSITY

Question 2

“the sticky or adhesive characteristic of a fluid”

Answer 2

VISCOSITY

Question 3

It can also be described in terms of a fluid’s thickness.

Answer 3

VISCOSITY

Question 4

In real life there is a drag force on the sphere tending to retard the motion of the sphere.

Answer 4

REAL FLOW

Question 5

The flow separates on the rear surface of the sphere, setting up a complicated flow in the wake and causing the pressure on the rear surface to be less than that on the forward surface. Hence, a drag force is exerted on the sphere

Answer 5

REAL FLOW

Question 6

This is a concept used in physics and engineering to study the behavior of fluids under idealized conditions.

Answer 6

FRICTIONLESS FLOW

Question 7

In reality, all fluids experience some degree of friction and viscosity, which affects their flow and energy transfer.

Answer 7

FRICTIONLESS FLOW

Question 8

useful as a starting point to understand the basic principles of fluid mechanics, but it is not applicable to real-world situations.

Answer 8

FRICTIONLESS FLOW

Question 9

Another region of __________ (sometimes called potential flow) outside the boundary layer.

Answer 9

FRICTIONLESS FLOW

Question 10

Fluid that experiences no friction or viscosity, meaning that there is no resistance to the flow of the fluid.

Answer 10

FRICTIONLESS FLOW

Question 11

The region of viscous flow which has been retarded owing to friction at the surface.

Answer 11

BOUNDARY LAYER

Question 12

Friction is important. It is the layer near the surface.

Answer 12

BOUNDARY LAYER

Question 13

Thickness grows as the flow moves over the body

Answer 13

BOUNDARY LAYER

Question 14

More and more of the flow is affected by friction as the distance along the surface increases.

Answer 14

BOUNDARY LAYER

Question 15

The presence of friction creates a shear stress at the surface “τw”.

Answer 15

BOUNDARY LAYER

Question 16

This shear stress has dimensions of force/area and acts in a direction tangential to the surface.

Answer 16

BOUNDARY LAYER

Question 17

Τw gives rise to a drag force called “skin friction drag”.

Answer 17

BOUNDARY LAYER

Question 18

Where μ is called the ____________ (viscosity of the gas). It has dimensions of mass/(length)(time).

Answer 18

Absolute viscosity coefficient

Question 19

For liquids, μ decreases as T increases. “Oil gets thin when Temp Increases.

Answer 19

Absolute viscosity coefficient

Question 20

But for gases, μ increases as T increases (Air gets “thicker” when temperature is increased).

Answer 20

Absolute viscosity coefficient

Question 21

Constant value of absolute viscosity coefficient IN METRIC SYSTEM

Answer 21

𝜇 = 1.7894x10^−5 𝑘𝑔/𝑚. 𝑠

Question 22

Constant value of absolute viscosity coefficient IN ENGLISH SYSTEM

Answer 22

𝜇 = 3.7373x10^−7𝑠𝑙𝑢𝑔/𝑓𝑡. s

Question 23

TWO BASIC TYPES OF VISCOUS FLOWS

Answer 23

LAMINAR FLOW
TURBULENT FLOW

Question 24

Flow in which the streamlines are smooth and regular and the fluid element moves smoothly along the streamline.

Answer 24

LAMINAR FLOW

Question 25

-Smooth motion fluid elements in a laminar flow.

Answer 25

LAMINAR FLOW

Question 26

- Flow in which the streamlines break up and a fluid element moves in a random, irregular, and tortuous fashion.

Answer 26

TURBULENT FLOW

Question 27

Tortuous, irregular motion of fluid elements

Answer 27

TURBULENT FLOW

Question 28

Less skin friction drag; pressure drag predominates.

Answer 28

LAMINAR FLOW

Question 29

Unstable, tends to favor flow separation

Answer 29

LAMINAR FLOW

Question 30

Transition region is closer to leading edge

Answer 30

LAMINAR FLOW

Question 31

Thinner boundary layer

Answer 31

LAMINAR FLOW

Question 32

Greater skin friction drag.

Answer 32

TURBULENT FLOW

Question 33

More stable; disorder is favored by nature

Answer 33

TURBULENT FLOW

Question 34

Transition region is farther aft

Answer 34

TURBULENT FLOW

Question 35

Thicker boundary layer

Answer 35

TURBULENT FLOW

Question 36

It is a measure of the ratio of inertia forces to viscous forces.

Answer 36

REYNOLD’S NUMBER

Question 37

Helps determine whether the flows in a body and its scaled version are aerodynamically similar.

Answer 37

REYNOLD’S NUMBER

Question 38

Can be applied in determining whether all, or portion of boundary layer is laminar or turbulent.

Answer 38

REYNOLD’S NUMBER

Question 39

Dimensionless, It varies linearly with X. Sometimes called a local Reynolds number, because it is based on the local coordinate X.

Answer 39

REYNOLD’S NUMBER

Question 40

REYNOLD’S NUMBER FORMULA

Answer 40

𝑅𝑒𝑥 = ρ∞V∞x/µ∞

Question 41

The flow always starts out from the leading edge as laminar. Then, becomes unstable and small “bursts” of turbulent flow begin to grow in the flow.

Answer 41

TRANSITION

Question 42

Over a certain region called the ________ region, the boundary layer becomes completely turbulent.

Answer 42

TRANSITION

Question 43

Transition is said to take place is the critical value xcr. In turn, xcr allows the definition of a critical Reynolds number for transition as

Answer 43

Rexcr = ρ∞V∞cr/µ∞

Question 44

FACTORS AFFECTING TRANSITION FROM LAMINAR TO TURBULENT

Answer 44

1. Increased surface roughness 2. Increased turbulence in the free stream 3. Adverse pressure gradients 4.Heating of the fluid by the surface 5. Similarity parameters of the flow (Mach Number and Reynold’s Number)

Question 45

Friction also causes another phenomenon, called ___________, which, in turn, creates another source of aerodynamic drag, called pressure drag due to separation (Form Drag).

Answer 45

FLOW SEPARATION

Question 46

Two Major Consequences of Separated Flow Over an Airfoil

Answer 46

1. A drastic loss of lift (stalling). 2. A major increase in drag, caused by pressure drag due to separation.

Question 47

A condition wherein the angle of attack increases beyond a certain point such that the lift begins to decrease.

Answer 47

STALL

Question 48

Occurs when the critical angle of attack of the airfoil is exceeded.

Answer 48

STALL

Question 49

Typically about 15 degrees, but it may vary significantly depending on the fluid, and Reynolds number.

Answer 49

STALL

Question 50

An ideal type of flow in which there is no friction.

Answer 50

Frictionless flow

Question 51

The Karman Vortex Street was named after aerodynamicist ________________.

Answer 51

Theodor Von Karman

Question 52

A ____________ is a repeating pattern of swirling vortices caused by the unsteady separation of a fluid around blunt bodies.

Answer 52

Karman vortex street

Question 53

An _______ is a streamlined body which when set at a suitable angle of attack, produces more lift than drag while also producing a manageable pitching moment.

Answer 53

Airfoil

Question 54

An airfoil is said to be _________ if the upper and lower cambers are equal in shape.

Answer 54

SYMMETRICAL

Question 55

An airfoil is said to be ___________ if the upper and lower cambers are not equal in shape.

Answer 55

ASYMMETRICAL

Question 56

The Precise distance from the Leading edge measured along the chord line.

Answer 56

Chord

Question 57

A straight line connecting the leading and trailing edges of an airfoil.

Answer 57

Chord Line

Question 58

Locus of all points equidistant from the top and bottom of the airfoil.

Answer 58

Mean Camber Line

Question 59

The maximum distance between the chord line and the mean camber line.

Answer 59

Camber

Question 60

Maximum distance between the top and bottom surfaces of the wing.

Answer 60

Thickness

Question 61

Is the maximum thickness-to-chord ratio.

Answer 61

Thickness Ratio

Question 62

The most forward points of the mean camber line.

Answer 62

Leading Edge

Question 63

The most rearward points of the mean camber line.

Answer 63

Trailing Edge

Question 64

The distance from wing tip to wing tip.

Answer 64

Wingspan

Question 65

The area of the projection of the actual outline on the plane of the chord.

Answer 65

Wing Area

Question 66

The ratio of the span to the chord. If the wing is not rectangular in shape, it is the square of the spane to the area.

Answer 66

Aspect Ratio –

Question 67

Angle between the relative wind and the chord line.

Answer 67

Angle of Attack

Question 68

Defined as the component of aerodynamic force perpendicular to the relative wind.

Answer 68

Lift

Question 69

Defined as the component of the aerodynamic force parallel to the relative wind.

Answer 69

Drag

Question 70

The air far upstream of the airfoil.

Answer 70

Relative Wind

Question 71

Developed by the National Advisory Committee for Aeronautics

Answer 71

NACA AIRFOIL

Question 72

These are airfoil shapes for aircraft wings.

Answer 72

NACA AIRFOIL

Question 73

The shape is described by a series of digits followed by the word _____. Can either be 4, 5, or 6 – digits.

Answer 73

NACA