Category Archives: Uncategorized

Airfoil Characteristics

Recently, someone asked a good question.

How can I find the aerodynamic properties of an airfoil?

Here’s my quick suggestion:

Simple low-fidelity incompressible (camber line only, but works amazingly well):

Medium low fidelity incompressible (camber and thickness)

Numerical incompressible with boundary layers

Expensive computational

  • CFD (don’t unless you need a compressible viscous solution)

Flight Dynamics and Control 1 (AEM 368)

AEM 368 is an introduction to aircraft dynamics including performance and stability and control. Dr. O’Neill taught this course in the Spring of 2017.Example Lectures:

Required Books:

  • Flight Stability and Automatic Control, R. Nelson, McGraw-Hill, 2nd ed, 1998.
  • Aircraft Performance and Design, John Anderson, McGraw-Hill, 1999.

Goals:

By the end of the course, students should be able to:

  • Understand basic aircraft performance and stability and control (S&C) terminology
  • Estimate aircraft performance in steady and accelerated flight mission phases
  • Size S&C surfaces of an aircraft
  • Demonstrate a physical and mathematical understanding of aircraft flight modes

Topics:

We will cover S&C and performance topics in the textbooks. Selected topics and sources supplement the text.

  • Aircraft Nomenclature, Atmosphere, Instruments
  • Static stability and control (FSAC, Chap 1)
  • Aircraft equations of motion (FSAC, Chap 2)
  • Longitudinal motion (FSAC, Chap 3)
  • Lateral motion (FSAC, Chap 4)
  • Steady Flight (APD, Chap 5)
  • Accelerated Flight (APD, Chap 6)
  • Aircraft Performance and Control Projects

GES 554: Partial Differential Equations

At the University of Alabama, I taught the GES 554 course Partial Differential Equations from 2014-2017. The course investigated theory, classification, formulation, relevancy, analysis, and solutions of PDEs. Both analytical and computational methods were studied with a special focus on PDEs commonly seen in engineering.

Textbook: Partial Differential Equations for Scientists and Engineers, S. Farlow, Dover ($12 from Amazon) Reviewed here

Notes: The course notes are available for free at: https://charles-oneill.com/ges554/.

2D Wave Equation on a square domain

Topics: The class covered all lessons and problems in Farlow’s book with selected topics and sources supplemented as necessary.

  • Classification and canonical forms
  • Parabolic and diffusion equations, Laplace and Fourier methods
  • Elliptic, BVP equations, Green’s functions
  • Hyperbolic, wave, and non-linear conservation equations
  • Numerical and approximate methods
  • Error analysis and verification & validation
  • Monte Carlo, perturbation and conformal mapping methods
  • Topics at instructor’s discretion
1D Heat Equation with a Fourier Expansion

Aerodynamics I

In the Fall of 2016 (and later in 2017), I taught AEM 313 Aerodynamics I.

Objectives:   Introduction to subsonic aerodynamics, including properties of the atmosphere; aerodynamic characteristics of airfoils, wings, and other components; lift and drag phenomena; and topics of current interest.

Required Book:     Fundamentals of Aerodynamics, John Anderson, McGraw-Hill, 5th ed, 2010

Topics:  

We will cover subsonic and transonic topics in the textbook. Selected topics and sources supplement the text.

  • Conservation Equations
  • Similarity Parameters
  • Flow Kinematics
  • Euler and Bernoulli Equation
  • Velocity Potential and Stream Function
  • Elementary Potential Flows
  • Laminar and Turbulent Boundary Layers
  • Airfoil and Wing Geometry
  • Thin Airfoil Theory
  • Lifting Line Theory (Example: Lesson16-PrandtlLiftingLine)
  • Lift, Drag and Pitching Moment
  • Low-Re and High-Alpha Effects
  • Subsonic Compressible Flow
  • Transonic and Supercritical Airfoils
  • Aircraft Aerodynamic Design Project (MemoAEM313Project)

Student Evaluations (Fall 2016): 16C Charles O’Neill (AEM 313-001 Aerodynamics)

One happy son

My son’s class has a stuffed animal as a class mascot, a worm named…. Wormie. Each child takes the worm home for a few days and shows the class what adventures Wormie had at home.

We decided to take Wormie up for a flight over Tuscaloosa. And this is not just any flight, but a aerobatic flight into the sunset. The result is one very happy son (and some neat photos).

Yes, the worm increased the drag considerably.

Prandtl Lifting Line Tool

Prandtl Lifting Line theory remains an excellent tools for preliminary design and gaining intuition about the aerodynamics of unswept wings.

Implementing a PLL solver is relatively simple; I made this version in a few hours with Fortran. The solver generates SVG files displaying the wing geometry, gamma and lift distributions as well as the integrated lift and drag coefficients for arbitrary wing geometries (as approximated by linear sections). The program and input files are available at: https://charles-oneill.com/code/prandtl/prl2.zip

A flat elliptical wing demonstrates the flat sectional lift coefficient distribution resulting from an elliptical lift distribution.

pll-elliptical

The beauty of the Prandtl lifting line theory is the ability to modify the wing geometry and airfoil sections. For example, given a 20% flap deflected 20 degrees on inner wing sections, the sectional lift distribution reflects the flap deflection. Of particular interest is that the shed vorticity is proportional to the slope of the green lift distribution.

Prandtl Lifting Line

The PLL theory is also instructive for understanding control surface behaviors. In the following image, the 20% ailerons are deflected approximately +-10 degrees (Thin airfoil theory is used to determine the equivalent zero lift line.). Of particular concern is that aileron deflections at high AOA can push the local angle of attack into a stalled state.

pll-aileron