93749 - Applied Aerodynamics

Course Unit Page

SDGs

This teaching activity contributes to the achievement of the Sustainable Development Goals of the UN 2030 Agenda.

Quality education Decent work and economic growth Industry, innovation and infrastructure Climate Action

Academic Year 2021/2022

Learning outcomes

The student will be able to apply the fundamental concepts of the physics of viscous flows in order to assess the flow behaviour around aerodynamic and bluff bodies, to estimate the aerodynamic loads, to propose flow control methods and to be capable to perform an aerodynamic conceptual design.

Course contents

1. THE FLUID AND ITS MOTION Elements of physics of fluids. Fluid properties. The Navier-Stokes equations. The equations for incompressible flows. Potential flow. The boundary layer. The Prandtl equations. Iterative procedure potential flow-boundary layer equations.

2. BLUFF BODY AERODYNAMICS Boundary layer separation. Aerodynamic and bluff bodies: main definitions. Iterative procedure for bluff bodies. Pressure in separated regions. Helmoltz model. Link between drag and energy in the Trefftz plane. Wake instability phenomena. Convective and absolute instability. Wake topology. Characteristic parameters. Vorticity contained in a boundary layer and its flux. Theorem of conservation of the total vorticity. Energy in the wake and link with intensity, dimension and topology of the vortices contained. Cd-Re curve for 2D bodies. Influence of roughness and turbulence in the free stream. Influence of geometry. Active and passive Flow control techniques for 2D bodies. The “boat tailing”. 3D bluff bodies. The Morel body. Cd behaviour and flow topology. Active and passive Flow control techniques for 3D bodies. Interference effects.

3. AERODYNAMIC OF VEHICLE Introduction. The role of aerodynamic in the design of a ground vehicle. The aerodynamic design: different approaches. Historical Background. Application of the basic concepts of bluff body aerodynamics to vehicles. Optimization, boat-tailing, base bleed, rear corners. Methodologies for the control of aerodynamic loads on ground vehicles. Numerical and experimental methods for the evaluation of aerodynamic loads. Aerodynamics of commercial vehicles. Race vehicle aerodynamics. Historical background. Tools for the generation of downforce in a racing vehicle. The aerodynamic design of a racing vehicle.

4. INDUSTRIAL AERODYNAMICS. Introductory remarks. The buffeting. Response of a system to buffeting. Correlation functions and correlation lengths. Response to a generic spectrum of forces. Aerodynamic admittance. Methods to reduce the response to buffeting. Galloping. Critical speed of galloping. Bodies at galloping. The phenomenon of vortex shedding and associated fluctuating forces. The phenomenon of lock-in. Response to vortex shedding. Methods for controlling the response to vortex shedding. Force due to acceleration. The adjoint mass. Evaluation of the adjoint mass with potential flow methodologies. General expression of kinetic energy and adjoint mass in 3D. Froude-Krylov force. Notes on flutter.

5. AERODYNAMICS OF VERTICAL TAKE-OFF VEHICLES Introduction. Historical aspects. Aerodynamics of the rotor. Equations of motion for the Hovering. Disk loading and Power Loading. Velocity induced in the disc. Coefficients of thrust and power. Comparing theoretical results with experimental measurements. Effects of non-ideal flow. Losses related to the wingtip vortices. Figures of merit. Estimation of non-ideal effects through measures on the rotors. Solidity of the rotor and load factors of the blade. Balance in ascent and descent flight conditions. Different regimes in the descent phase. Power required for the ascent and descent. The autorotation. Balance in horizontal flight. Numerical solutions to the equations of inflow. Validity of the equation of inflow. Blade elements analysis. Blade Element Theory. Ideal twist. Notes on the numerical simulation. The optimal rotor.

6. WIND TURBINES AERODYNAMICS. Introductory remarks. Historical aspects. Available power. The theory of the actuator disk. The Betz limit. Blade Element Model for wind turbines. The "Blade Element Momentum Theory". Effect of the number of blades. Effects of viscosity. Losses related to the tip. Effect of a stall. Airfoils for wind turbines. Notes on the wake vorticity.

7. SAIL BOATS AERODYNAMICS. Introductory remarks. Historical aspects. Basic definitions. Aerodynamic and hydrodynamic forces in sailing boats. Design issues. Performance analysis.

Readings/Bibliography

Elements of Fluid Dynamics – G. Buresti – Imperial College Press - ISBN-13 978-1848168893

Road Vehicle Aerodynamic Design: An Introduction - Mechaero Publishing; ISBN-13: 978-0954073404

Principles of Helicopter Aerodynamics - J.G. Leishman - Cambridge University Press- ISBN-13: 978-1107013353

Slides and Lecture notesavailable on IOL

Teaching methods

Lectures and exercises given by the docent. During the course, seminars and integrative courses, given by highly distinguished lecturers, will be organised. They will be focused on specific aerodynamic topics for the Aerospace and Industrial Engineering. These arguments will be part of the program and can be the part of the final exam.

Assessment methods

The exam consists of a single session in which the student should show a sufficient skill in writing down and commenting the mathematical and physical models as well as the different experimental techniques.

Teaching tools

Blackboard and power point presentations.

Office hours

See the website of Alessandro Talamelli