The objectives of this course are (1) to provide an advanced level exposition of the various complex aerodynamic problems that are associated with rotorcraft, and (2) to provide some background and familiarization of the computational tools that are used to model these complex aerodynamic flows. The focus will be on basic concepts, observations, applications, and results.

**Prerequisites: ENAE 631 or equivalent. Permission of instructor.**

Instructor:

Dr. J. Gordon Leishman, Room 3179C,

Open. You are welcome to come and consult with the instructor at anytime during regular office hours, workload permitting. If in doubt, call or email first to be sure I'm available.

Students are encouraged to use email as a means of interacting with the instructor. However, please do not expect an immediate response - I get to email as quickly as I can. Class announcements will often be made by email. Click here to email: Dr. J. Gordon Leishman. Please **do not **send homework assignments or other assignments by email (see homework policy below).

Assessment method:

- Homework (1/3)
- Technical Note & Presentation (1/3)
- Final Exam (1/3).

Homework Problem Sets

These will be posted here on this web site.

- Homework Problem Set # 1.
- Homework Problem Set # 2.
- Homework Problem Set # 3.
- Homework Problem Set # 4. Click here.
- Homework Problem Set # 5.

Homework is assigned about every other week, usually on a **Tuesday**. Be sure to check the web page then for homework and any other announcements. There will be 5 homework problem sets. Homework must be submitted one-week after it is assigned. Submission of homework is mandatory. Students taking the course over instructional television (ITV) must submit all their assignments through ITV, or can mail the assignments directly to the instructor by regular US mail if submission through ITV is not possible. The homework must be dated as received by ITV or postmarked by the due date. **DO NOT** send homework by email or by FAX. Time-extensions for homework submissions will be granted, but only on a case by case basis. Late homework submitted without an extension will not be graded.

Technical Note & Class Presentation:

A formal Technical Note from each participating student will be due **in late April.** The essay **title** and a **short abstract** must be submitted for approval**.** The Note must be on an aspect of rotorcraft aerodynamics. Click here for further details on the specifications for the technical note and presentation.

Mid-Term Exam:

There is no mid-term exam for the Spring '05 semester.

Textbooks:

*Principles of HELICOPTER AERODYNAMICS*

J. Gordon Leishman, University of Maryland, College Park. ISBN: 0-5216606-0-2 560 pages, 49 photos, 235 figures, 7 tables 7" x 10" hardbound Click HERE for more details.

There are several textbooks that are useful supplementary reading for this course. The classic text on the subject is: **Aerodynamics of the Helicopter ** by Gessow and Myers. Although the nomenclature is a little out of date, this text provides a solid coverage of the basic material. The main secondary text will be **Helicopter Theory** by Johnson. This is the definitive reference for modern helicopter analyses. An inexpensive Dover publication of this text is now available. Other useful texts are: **Rotary Wing Aerodynamics** by Stepniewski and Keys, **Helicopter Performance, Stability and Control ** by Prouty, and **The Foundations of Helicopter Flight ** by Newman.

Course outline:

**Aerodynamic Design Issues Associated with Helicopters:**Basic aerodynamic design issues associated with main rotors. Summary of the main rotor flow field and key aerodynamic problem areas. Advanced blade tip designs: including the use of sweepback, taper, anhedral, the BERP blade and other advanced rotor blade technology. Introduction to airfoil section requirements. Aerodynamics and design of the fuselage and empennage. Anti-torque devices, including tail rotors, fan-in-fin and other concepts. Advanced rotorcraft designs.

**Aerodynamic Characteristics of Rotor Airfoils:**Recap of blade element concept, pressure loadings on airfoils in subsonic an transonic flow, forces and moments on a typical airfoil, concepts of aerodynamic center and center of pressure, Reynolds number and Mach number and their effects on airfoil characteristics, concept of the boundary layer and viscous effects. Airfoil geometry and summary of effects on aerodynamic characteristics such as lift, drag and pitching moment, effects of thickness and camber, static airfoil characteristics, linear versus nonlinear aerodynamics, flow separation and stall, types of static stalling characteristics, subsonic flows and effects on airfoil characteristics, transonic flows, advanced rotor airfoil design methodology, aerodynamic testing considerations for rotor airfoils.Representing airfoil characteristics in comprehensive rotor analyses.

**Unsteady Aerodynamics:**Classical methods of unsteady aerodynamics, circulatory versus noncirculatory flows, Theodorsen theory, Sears' sinusoidal gust problem, Loewy problem, indicial response, Kussner and Wagner problems, Miles' problem: convecting versus stationary gusts, Duhamel's superposition principle, numerical methods for linear superposition: recursive formulation and state-space representation, indicial response in subsonic flow, piston theory, consideration of compressibility effects in unsteady flows, pitching versus plunging effects, unsteady free-stream effects, blade vortex interactions.

**Dynamic Stall:**A physical discussion of the problem especially as applied to rotors, unsteady separation and leading-edge vortex shedding, effects of dynamic stall on chordwise pressure distributions and sectional airloads, effects of Reynolds number and compressibility effects, sweep effects, three-dimensional effects, difficulties in modeling of dynamic stall and associated separation phenomena, semi-empirical unsteady aerodynamic models for dynamic stall. Consequences of dynamic stall on rotor loads and helicopter performance.

**Rotor Wakes and Wake Modeling:**Rotor wake developments in hover and forward flight, experimental methods used to observe rotor wakes including smoke, schlieren and shadowgraphy, experimental observations of rotor wake geometry including tip vortices and other vortical wake structures, modling of vortical flows, modeling of the wake and its effects on rotor loads and performance, recap on inflow models, classical rigid vortical wake models, prescribed vortex wake models in hover and forward flight, introduction to free-vortex wake models and associated numerical methods.

**Interactional Aerodynamic Phenomena Associated with Rotorcraft:**Summary of the various interaction phenomena between the main and tail rotors, rotor/fuselage interactions, rotor/tail rotor interactions, interference effects on the rotor by the fuselage, flow visualization of interaction phenomena, vortex surface collisions, summary of numerical modeling interactional phenomena such as vortex/surface interactions.

Specialist Topics:

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