Applied Aerodynamics - I

Transcription

1 Applied Aerodynamics - I o Course Contents (Tentative) Introductory Thoughts Historical Perspective Flow Similarity Aerodynamic Coefficients Sources of Aerodynamic Forces Fundamental Equations & Principles Inviscid & Incompressible Flow Incompressible flow over Airfoil and Finite Wing Wing Body Combination Aircraft Performance 1

2 Applied Aerodynamics - I o Course Evaluation Quizzes 20% Assignment 5% Mid-Term Exam 25% Final Term Exam 50% Resources: Lecture & Slides Book: Fundamentals of Aerodynamics John D. Anderson Aircraft Performance and Design John D. Anderson 2

3 o Aerodynamics 3

4 o Preview Read section 1.1 IMPORTANCE OF AERODYNAMICS from the book Fundamentals of Aerodynamics What is fluid? Hydrodynamics, Gas Dynamics and Aerodynamics? 4

5 o Preview Douglas DC-3, one of the most famous aircraft of all time, is a low-speed subsonic transport designed during the 1930s Without a knowledge of low-speed aerodynamics, this aircraft would have never existed 5

6 o Preview Boeing 707 opened high-speed subsonic flight to millions of passengers beginning in the late 1950s Without a knowledge of high-speed subsonic aerodynamics, most of us would still be relegated to ground transportation 6

7 o Preview The Bell X-1 became the first piloted airplane to fly faster than sound, a feat accomplished with Captain Chuck Yeager at the controls on October 14, 1947 Without a knowledge of transonic aerodynamics (near, at, and just above the speed of sound), neither the X-1, nor any other airplane, would have ever broken the sound barrier 7

8 o Preview Lockheed F-104 was the first supersonic airplane point-designed to fly at twice the speed of sound, accomplished in the 1950s 8

9 o Preview Lockheed-Martin F-22 is a modern fighter aircraft designed for sustained supersonic flight Without a knowledge of supersonic aerodynamics, these supersonic airplanes would not exist 9

10 o Preview An innovative new vehicle concept for high-speed subsonic flight is the blended wing body Blended-wing-body promises to carry from 400 to 800 passengers over long distances with almost 30 percent less fuel per seat-mile than a conventional jet transport This would be a renaissance in long-haul transport 10

11 o Preview Primary objectives of studying aerodynamics: External Aerodynamics: The prediction of forces and moments on, and heat transfer to, bodies moving through a fluid (usually air) Internal Aerodynamics: Determination of flows moving internally through ducts 11

12 o Preview 12

13 o Fundamental Aerodynamic Variables 13

14 o Fundamental Aerodynamic Variables 14

15 o Fundamental Aerodynamic Variables 15

16 o Fundamental Aerodynamic Variables 16

17 o Fundamental Aerodynamic Variables 17

18 o Fundamental Aerodynamic Variables 18

19 o Fundamental Aerodynamic Variables 19

20 o Fundamental Aerodynamic Variables 20

21 o Fundamental Aerodynamic Variables Streamlines A moving fluid element traces out a fixed path in space. As long as the flow is steady (i.e., as long as it does not fluctuate with time), this path is called a streamline of the flow Drawing the streamlines of the flow field is an important way of visualizing the motion of the gas 21

22 o Fundamental Aerodynamic Variables Shear Stress The shear stress τ is the limiting form of the magnitude of the frictional force per unit area, where the area of interest is perpendicular to the y axis Shear stress acts tangentially along the streamline 22

23 o Fundamental Aerodynamic Variables Shear Stress Value of the shear stress at a point on a streamline is proportional to the spatial rate of change of velocity normal to the streamline at that point For the flow, dv/dy is the velocity gradient τ dv/dy The constant of proportionality is defined as the viscosity coefficient (μ) 23

24 o Units 24

25 o Aerodynamic Forces and Moments Aerodynamic forces and moments on the body are due to only two basic sources: 1. Pressure distribution 2. Shear stress distribution No matter how complex the body shape may be, the aerodynamic forces and moments on the body are due entirely to the above two basic sources The only mechanisms nature has for communicating a force to a body moving through a fluid are pressure and shear stress distributions on the body surface 25

26 o Aerodynamic Forces and Moments The net effect of the p and τ distributions integrated over the complete body surface is a resultant aerodynamic force R and moment M on the body The flow far away from the body is called the freestream, and hence V is also called the freestream velocity 26

27 o Aerodynamic Forces and Moments 27