Aerospace Practicum: Lecture 2 - Introduction to Basic Aerodynamics, Slides of Aerospace Engineering

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AEROSPACE PRACTICUM

Lecture 2: Introduction to Basic Aerodynamics 1

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READING AND HOMEWORK ASSIGNMENTS

• Reading: Introduction to Flight, 7 th^ Edition, by John D. Anderson, Jr.
  • For this week’s lecture: Chapter 4, Sections 4.1 - 4.
  • For next week’s lecture: Chapter 4, Sections 4.10 - 4.21, 4.
• Lecture-Based Homework Assignment:
  • Problems: 4.1, 4.2, 4.4, 4.5, 4.6, 4.8, 4.11, 4.15, 4.
    • DUE: Friday, January 25, 2013 by 11am
    • Turn in hard copy of homework
  • Also be sure to review and be familiar with textbook examples in

Chapter 4

• Laboratory Week #2: MATLAB
• Laboratory Assignment #1: Due January 18, 2013 Docsity.com

REVIEW OF BASIC CONCEPTS

Review: Introduction to Flight by Anderson Chapter 2: 2.1-2. Chapter 3: 3.1-3.

Be sure that you are familiar with example problems

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REVIEW OF BASIC DEFINITIONS (2.1-2.3)

• Streamline (2.1)
  • Set of points that form a line that is everywhere tangent to local velocity vector
  • No flow across streamlines
  • For a steady flow, moving fluid element traces out a fixed path in space
• Stream tube
  • A set of streamlines that intersect a closed loop in space
• Steady Flow : A flow that does not fluctuate with time (all flows in MAE 1202)
• Unsteady Flow : A flow that varies with time
• Equation of State for a Perfect Gas (2.3), applies at a point
  • Ideal Gas Law: p = ρ RT or pv = RT (v = 1/ρ)
  • R universal = 8,314 J/kg mole K
    • R for air = 8,314 / 28.96 = 287 J/kg K (or 1,716 ft lb / slug R)
• If you do not remember these concepts review Section 2.1-2.

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HARRIER INSTANTANEOUS STREAMLINES

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WATER STREAMLINES ON F-16 MODEL

http://www.aerolab.com/water.html Docsity.com

LAMINAR VERSUS TURBULENT FLOW

• Two types of viscous flows
  • Laminar : streamlines are smooth and regular and a fluid element moves smoothly along a streamline
  • Turbulent : streamlines break up and fluid elements move in a random, irregular, and chaotic fashion

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FRCTION EXAMPLE: AIRFOIL STALL (4.20, 5.4)

• Key to understanding: Friction causes flow separation within boundary layer
  1. Boundary layers are either laminar or turbulent
  2. All laminar B.L. → turbulent B.L.
  3. Turbulent B.L. ‘fuller or fatter’ than laminar B.L., more resistant to separation
• Separation creates another form of drag called pressure drag due to separation
  • Dramatic loss of lift and increase in drag

We will examine these airfoils next lecture in detail

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CYCLING AERODYNAMICS

• Bike and rider aerodynamics
• Peloton vs. single rider

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BOBSLED AERODYNAMICS

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DENSITY DISCONTINUITY: SHOCK WAVES

Photograph of a T-38 at Mach 1.1, altitude 13,700 feet, taken at NASA Wallops in 1993. Schlieren photography (from German word for "streaks") allows visualization of density changes, and therefore shock waves, in fluid flow Schlieren techniques have been used for decades in laboratory wind tunnels to visualize supersonic flow about model aircraft, but not full scale aircraft until recently. Dr. Leonard Weinstein of NASA Langley Research Center developed first Schlieren camera, which he calls SAF (Schlieren for Aircraft in Flight), that can photograph shock waves of a full sized aircraft in flight. He successfully took a picture which clearly shows shock waves about a T-38 aircraft on December 13, 1993 at Wallops Island, MD. Docsity.com

KEY TERMS: CAN YOU DEFINE THEM?

• Streamline
• Stream tube
• Steady flow
• Unsteady flow
• Viscid flow
• Inviscid flow
• Compressible flow
• Incompressible flow
• Laminar flow
• Turbulent flow

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WHY STUDY AERODYNAMICS?

• Study of aerodynamics is important to determine forces and

moments (torques) acting on flying vehicles

• Forces and moments are caused as a result of interaction between

a body (airplane, rocket, etc.) and air surrounding it

• Interaction depends on flow conditions (fluid properties, relative

velocity, pressure, temperature, etc.) and body shape (geometry)

• GOALS:
  • Develop foundation of theoretical development (mathematical)
  • Gain insight into physical phenomena taking place

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3 FUNDAMENTAL PRINCIPLES

1. Mass is neither created nor destroyed (mass is conserved)

• Conservation of Mass
• Often also called: ‘Continuity’

2. Sum of Forces = Time Rate Change of Momentum (Newton’s 2 nd^ Law)

• Often reduces to: Sum of Forces = Mass x Acceleration ( F = m a )
• Momentum Equation
• Bernoulli’s Equation, Euler Equation, Navier-Stokes Equation

3. Energy neither created nor destroyed (energy is conserved)

• Can only change physical form
• Energy Equation (1 st^ Law of Thermodynamics)

How do we express these statements mathematically?

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