Today, we learn the basics of aircraft inlet design.
This November, I was asked to provide a substitute lecture to a senior level propulsion class (AEM 408). For this lecture, I attempted to provide the basics of inlet design by discussing the relevant physics and constraints.
Inlet fan face total pressure was introduced as a way to quantify the performance of an inlet and to diagnose common issues.
The concept of boundary layer growth with the inlet’s adverse pressure gradient was reinforced from an earlier Aerodynamics I course.
What are the possibilities of investigating storm damage with drones? In 2017, I had the opportunity from a team of Civil Engineers at the University of Alabama to demonstrate a rapid deployment to the gulf coast of Florida after Hurricane Irma.
Hurricane Irma formed off the west coast of Africa on the 27th of August 2017. By the 9th of October, Irma was a category 5 storm off the east coast of Cuba. Irma made landfall at the Florida Keys on the 10th of October at noon as a Category 4. Mainland landfall was on the night of the 10th as a Category 3 to 2.
Logistics
The University of Alabama’s Civil Engineering department rapidly put together a team of approx. 12 members with the specific goal of evaluating the performance of “fortified” homes built to a particular standard. Each of the 4 teams included professors, students, and insurance experts. Teams 1-3 consisted of ground based members surveying the damage, documenting structural and personnel reports, and interviewing inhabitants. Team 4 consisted of UAV operations and a LiDAR scanning crew, with Dr. O’Neill as the professor lead.
The primary lead from the Civil Engineering department was Dr. Andy Graettinger (https://eng.ua.edu/people/andrewg/) with Drs. Kreger, Aaleti, and Hainen.
Our equipment was deployed on Wednesday afternoon to be driven to Fort Myers, FL, where the remaining members rendezvoused on Thursday night. We scanned selected locations in Fort Myers south to Marco Island on Friday and scanned the Tampa area on Saturday. The entire crew returned to UA on Sunday and Monday.
The airspace was relatively simple in the Ft Myers area with a mix of uncontrolled, class D, and class C airports. The Tampa area was more complex with class B, and multiple class D airports. I do appreciate the respective ATC facilities for working with us.
Equipment
My aero team brought two UAS platforms with visible and IR cameras.
DJI S900 with an optical camera and IR camera
DJI Inspire with an optical camera
We also brought communications and flight mapping software appropriate for operating small UAS/drones in urban environments.
Operations
Operating in a post-hurricane environment presented several challenges. The most pressing was take-off/landing access; this includes obstacle avoidance of the passive type (e.g. trees, poles, wires, waste piles, etc) and active type (e.g. people, vehicles, animals, wind-shear/rotor-vortex, etc).
A secondary challenge in low-lying areas was water inundation. Bonita Springs was completely flooded up to 2+ ft.
The worst damage surveyed was along the Marco island area south of Ft Myers.
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:
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
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.
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).
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.
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.
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.
