Drag polar | Flight Mechanics | GATE Aerospace

For Video Lecture of this presentation: https://youtu.be/NAjezfbWh4Y

The topics covered in this session are, drag, categories of drag, drag polar equation and drag polar graph, drag polar derivation, induced drag coefficient.

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1. FLIGHT MECHANICS DRAG POLAR Presented by - Ganesh Natarajan S Target Audience : Gate Aerospace, Aerospace and Aeronautical Engineering Students, etc.

2. CORE TOPICS: Basics: Atmosphere: Properties, standard atmosphere. Classification of aircraft. Airplane (fixed wing aircraft) configuration and various parts. Airplane performance: Pressure altitude; equivalent, calibrated, indicated air speeds; Primary flight instruments: Altimeter, ASI, VSI, Turn-bank indicator. Drag polar ; takeoff and landing; steady climb & descent; absolute and service ceiling; cruise, cruise climb, endurance or loiter; load factor, turning flight, V-n diagram; Winds: head, tail & cross winds. Static stability: Angle of attack, sideslip; roll, pitch & yaw controls; longitudinal stick fixed & free stability, horizontal tail position and size; directional stability, vertical tail position and size; dihedral stability. Wing dihedral, sweep & position; hinge moments, stick forces. SPECIAL TOPICS: Dynamic stability: Euler angles; Equations of motion; aerodynamic forces and moments, stability & control derivatives; decoupling of longitudinal and lateral-directional dynamics; longitudinal modes; lateral-directional modes. SYLLABUS

3. DRAG POLAR

4. DRAG Definition The aerodynamic force that opposes an aircraft's motion through the air is known as drag. In common there are only two general types of drag namely, Pressure drag - Due to a net imbalance of surface pressure acting in the drag direction. Friction drag - Due to the net effect of shear stress acting in the drag direction.

5. Skin-friction drag: Frictional shear stress integrated over the surface. Form drag: Pressure drag due to flow separation Profile drag: Skin friction drag + Form drag. (2D airfoils / section drag.) Parasite drag: Skin friction drag + Form drag. (Complete airplane configuration.) Interference drag: Total Drag - Drag due to individual component of the airplane. Induced drag: A pressure drag caused by the induced flow ( downwash ) associated with the vortices created at the tips of finite wings. Zero-lift drag: The parasite drag at its zero-lift angle of attack , i.e., Lift = zero. (Complete Airplane Configuration.) Drag due to lift: Parasite drag during non-zero-lift angle of attack + Induced drag Categories of Drag – Subsonic Drag Definitions Book Reference : Aircraft Performance & Design, J.D. Anderson. (2010). Pg.No : 113-114.

6. DRAG POLAR The equation and the graph expressing relation between C D and C L are called the drag polar. Drag polar reflect the aerodynamic information necessary for the performance analysis of an airplane. Total drag = parasite drag + wave drag + induced drag In terms of co-efficient, Drag Polar Equation: Here C D = Total drag coefficient, C D,o = Zero-lift parasite drag coefficient, = Drag due to lift.  

7. DRAG POLAR: Equation & Graph Pressure Distribution Over Thin Airfoil - Gaurav – www.learnpick.in

8. DRAG POLAR: Equation & Graph By TSRL - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19821696 Gopalarathnam , Ashok & Mcavoy , Christopher. (2002). Effect of Airfoil Characteristics on Aircraft Performance. Journal of Aircraft - J AIRCRAFT. 39. 427-433. 10.2514/2.2968.

9. DRAG POLAR: Insights Drag polar is nothing more than the resultant aerodynamic force plotted in polar coordinates -hence the name drag polar . The locus of all such points for all values of α forms the drag polar. Drag polar provides the following information for performance analysis C L /C D , that is, lift-to-drag ratio. The tangent line - point of maximum lift-to-drag ratio for the airplane Design point for the airplane i.e. design lift coefficient for the airplane.

10. DRAG POLAR: Derivation

11. DRAG POLAR: Derivation

12. DRAG POLAR: Derivation Gopalarathnam , Ashok & Mcavoy , Christopher. (2002). Effect of Airfoil Characteristics on Aircraft Performance. Journal of Aircraft - J AIRCRAFT. 39. 427-433. 10.2514/2.2968.

13. Book Reference Aircraft Performance & Design, J.D. Anderson . (2010). Chapter 2 - Aerodynamics of the Airplane: The Drag Polar Pg.No : ( 51-144/596). DRAG POLAR

14. Copyright Notice: Images used in this presentation are sourced from pixabay.com under “ Pixabay License” which are “ Free for commercial use and No attribution required ” category (or) from other sources, in which case appropriate attributions are provided.