**Fluids Section
**Director: G.Bergeles

__Subject__

Fluids properties and definitions (density, compressibility, viscosity). The fundamental laws of fluid mechanics: continuity, momentum, energy and moment of momentum equations for one or multiple phase flows expressed in inertial and rotating reference system. Ideal-fluid flow, boundary layer concepts, adiabatic flow, non steady flow, shock waves, flow in pipes, hydraulic transient and water hammer. Energy conversion in turbomachinery and theory of turbomachines, hydraulic and thermal. Airfoil theories, cascades, subsonic and supersonic flow. Flight theory, propulsion systems. Environmental fluid mechanics. Bio-fluid mechanics, non-Newtonian fluids.

__Subjects offered by the Fluids Section__

**FLUID MECHANICS I [4(O)]**

Historical review, achievements - Physics and Chemistry of fluids - Continuum mechanics - Kinematics - Basic laws in integral and differential form: balance of mass, momentum, moment of momentum energy(1st and 2nd law) - Constitutive relations - Newtonian and non-Newtonian fluids - Applications, simplifications: equations of Euler and Bernoulli - Equations of Navier-Stokes - Analytic solutions of Navier-Stokes equations (laminar flow in pipes) - Similarity laws - Flow stability - Turbulent flows - The concept of boundary layer - Laminar boundary layer of flat plate (Theory of Blasius) - Turbulent flow in pipes - Pipe networks - Forces on moving bodies - Moving frames of reference - Discontinuities.

**FLUID MECHANICS II [5 EME(O), CME, PE, AME(O)]**

Laminar and turbulent boundary layers of incompressible fluid - Approximate boundary layer theories - Inviscid flowfields (Solution methods, conformal mapping, Joukowski airfoils) - Vorticity theorems - One dimensional compressible flow - Normal shock waves - Fanno and Rayleigh lines - Converging and diverging nozzle flow - Free surface flows - Two phase flows.

**HYDRAULIC MACHINES I AND LABORATORY [6 EME(O), CME(O), PE(O), AME]**

Introduction to hydraulic turbomachines - The fundamental equations for compressible and incompressible fluid - Principles of operation and shape of turbomachinery - Relative motion in the case of rotating impeller, equations of motion and velocity triangles - Fundamental equations, efficiency coefficients and operation characteristic curves of centrifugal pumps - Cavitation - Geometric and dynamic similarity laws and specific speed - Dimensionless parameters - Description of a typical hydroelectric plant and of different types of hydraulic turbines - Fundamental equations, efficiency coefficients, velocity triangles, characteristic curves and cavitation of hydraulic turbines - Estimation of the main dimensions of hydraulic turbines.

**AERODYNAMICS [6 EME(O), AME(O)]**

Introduction to Aerodynamics. Steady, potential flow around airfoils. Theodorsen - Trefftz transformation. Aerodynamic coefficients of lift, drag and moment, center of pressure, center of lift, drag and moment, center of pressure, center of lift, influence of viscosity, stall conditions. Performance and design of airfoils. Families of airfoils. Theory of cascade flow. Application for blowers. Steady flow around bodies of revolution. Introduction to the panel method. Applications to the flow around airfoils. The method of boundary elements in 2-D flow and applications.

**ENVIROMENTAL FLUID MECHANICS [6 EME(O), AME(O)]**

Introduction to meteorology - Plume rise and influence of nearby surface obstructions - Gaussian plume dispersion models from instantaneous and continues sources; applications in the dispersion of effluents from stacks - Gradient type models for the dispersion of pollutants and their use in cities - Dispersion model for cooling tower plumes - Antipollution equipment as electrostatic precipitators, bagfilters, cyclones, desulphurisation plants.

**ONE DIMENSIONAL ANALYSIS OF THERMAL TURBOMACHINES [7 EME(O), CME(O),
PE(O), AME(O)]**

Familiarization of the student with the layout, operation and aerothermodynamics of the Thermal Turbomachines - Basic equations and theory of mean line analysis in turbomachines - One dimensional analysis and design of compressors and turbines - Similarity laws and performance maps - Operation of single and multistage compressors and turbines - Thermodynamic cycles and typical machine configurations.

**COMPUTATIONAL FLUID MECHANICS [7 EME, CME, AME(O)]**

Numerical solution of fluid flow equations - Methods of solution of algebraic systems of equations; numerical solution of ordinary differential equations, Runge-Kutta methods - Elliptic, Parabolic and Hyperbolic partial differential equations and descretization methods to finite difference equations - Application of finite difference methods to Potential flows (Laplace equations), non viscous flows (Euler equations) and viscous flows (Navier-Stokes equations) - Mathematical models of turbulence - The nature of turbulence, the energy cascade, the energy spectra.

**LOW-SPEED AIRCRAFT AERODYNAMICS [7 EME, AME(O)]**

Introduction to Aerodynamics of the Low Speed Aircraft (lift and drag). Simple lift and drag force calculations. The steady three-dimensional flow of an inviscid fluid: (a) The flow around a fuselage, (b) The flow around a wing (lifting line theory, Prandtl’s equation, calculation of the aerodynamic coefficients - the compressibility effect) (c) The flow around a propeller (momentum theory, blade element theory - lifting line theory. The performance and the design problem of an aircraft propeller) - Vortex-Lattice methods (d) The flow around an aircraft. Static theory of flight and stability. Current numerical methods for aerodynamic problems and applications.

**HYDRAULIC MACHINES II [7 EME, CME, AME]**

Calculation and design of centrifugal pumps; different types of pumps, selection of design parameters, calculation of the main dimensions and design of impeller and spiral casing - Flow analysis in the meridional and blade-to-blade sections - Selection of materials, tolerances, shaft calculation - Study and design of axial flow pumps: theoretical analysis, equations or radial equilibrium, cascade’s theory, design of the impeller and of the principal elements - Small hydroelectric plants: general description, review of the recent developments in Greece and world-wide, treatment of hydrologic data, technical and economic analysis, standardize electromechanical equipment, automatization. FLUID MECHANICS LABORATORY [7 EME, AME]

A number of Laboratory exercises are carried out (8 to 10) where students are familiarized with several fluid mechanics measuring techniques like Pitot, Prandtl, Hot-wire, Laser-Doppler-Anemometry, Ultrasonic, torque meters, manometers, 6-component balance - The theory of the above techniques is presented in hourly lectures as well as the communication between the measuring devices and a personal computer through an A/D converter.

**INTRODUCTION TO THE AIRCRAFT AND ITS SUBSYSTEMS [7 AME(O)]**

Aircraft subsystems. Structural characteristics. Introduction to flight dynamics.

Principles of aircraft stability and control. Automatic pilot system. Application of adaptive control to aircraft flight systems.

The principle of operation of the aircraft gas turbine and the reasons for its prevalence over the internal combustion engine is examined. Its evolution until today and future perspectives are described.

Systems of the aircraft, historical developments, statistical data, FAR 23 regulations, preliminary aircraft sizing. Principles and operation of the propulsion system. Principles of dynamic stability and control, automatic pilot. Introduction to the aircraft structures and materials.

Introduction to aerospace technology materials, conventional (metals) and non-conventional (ceramics, polymers, composites, sandwich) materials and their machinability. Crash analysis of aerospace structures.

**COMPRESSIBLE FLOW AERODYNAMICS [8 EME, AME(O)]**

Discontinuities in Aerodynamics - Laws of vorticity for compressible flows - Linear and non linear theories of two-dimensional flow field - Prandtl - Mayer flow - Oblique shock waves - Mach lines - One dimensional unsteady, compressible flow - Theory of thin bodies in compressible flow (supersonic flow) - Linear theory of wings in compressible flow - Non-equilibrium gas flows - Gas kinetics - Computational methods in high speed Aerodynamics - Introduction to supersonic airplane Aerodynamics.

**UNSTEADY AERODYNAMICS [8 EME, AME(O)]**

The unsteady aerodynamic phenomena and their significance in Aeronautics. Helmholtz theorem. Singular vortex distributions and their kinematics and dynamic behavior. Unsteady flow around an airfoil. The vortex particle method. The vortex flows as a dynamic system. Unsteady flow around a wing. Introduction to Aeroelasticity. The typical flexible airfoil (two elastic degrees of freedom) - Wing in bending and torsion. Linear theory of Aeroelasticity: Hamilton’s principle, formulation and solution of the aeroelastic equations. Introduction to non-linear Aeroelasticity.

**INTRODUCTION TO AIRCRAFT ENGINES I [8 AME(O)]**

Fundamentals of aircraft propulsion. Comparative study of the various types of engines. Description of engine components, analysis calculation of overall engine performance. Component characteristics and matching, engine operating line. On wing engine performance for various flight conditions. THREE DIMENSIONAL FLOW IN THERMAL TURBOMACHINES [8 EME, AME]

General considerations upon the requirements for the analysis and design of Thermal Turbomachines. Development of the 3D flow equations and presentation of the quasi-3D models on the basis of which the analysis/design of turbomachines is performed (S1 and S2 surfaces). Corresponding equations and numerical solutions. Physical description of the flow through turbomachinery components and semi-empirical relations for calculations of blading characteristics.

**HYDRODYNAMIC INSTALLATIONS [8 EME, AME]**

Unsteady hydraulic phenomena. Theory of rigid fluid column. Water hammer equations. Speed of the wave. Method of characteristics and solution of the water hammer equation by the graphical and numerical method. Complete examination of the water hammer in pipes and installations with pumps or turbines. Methods for water hammer protection.

Pumping installations: pipes, fittings, flanges, valves, general layout of various types of pumping installations, sensors. Different methods for flow rate modification, automatization, design of the suction sump, noise and temperature rise. Start-up procedure. Pipe networks.

**WIND ENERGY [9 EME(O), CME, PE, AME(O)]**

Meteorological wind data - Wind energy potential. Types and subsystems of Wind Turbines. Aerodynamic design of Horizontal and Vertical Axis Wind Turbines. Electric generators of Wind Turbines and connection to the power grid. Sitting. Aerodynamic analysis and optimal design of wind parks. Empirical choice of Wind Turbines. Wind Energy applications and their economics.

**MATHEMATICAL AND NUMERICAL METHODS IN AERODYNAMICS [9 EME(O), AME(O)]**

Mathematical formulation of problems in physics. Numerical, analytical methods. The theory of successive approximations. Analysis of linear problems: (a) Elliptic problems (integral equations, boundary element methods, variational formulation, finite element methods). Applications to Aerodynamics (potential flows, Stoke’s flows, the least square method, the penalty method, hybrid variational formulation). (b) Unsteady problems: the diffusion equation, the wave equation, the finite difference method, the finite element method, the vortex particle method). Analytic methods: Regular and singular asymptotic problems, application to the flow around an airfoil and a wing.

**GAS AND STEAM TURBINE OPERATION [9 EME(O)]**

Cycle analysis, component characteristics and engine performance, component matching. Operation for different external loads, operational limits. Equilibrium running line and transient performance. Control systems and instrumentation for engine supervision, starting and operating line displacement. Principles of maintenance practices, engine monitoring, fault diagnosis. Use of computers for simulation, monitoring, fault diagnosis and engine management.

**TOPICS IN JET ENGINE OPERATION [9 AME(O)]**

Methods and systems for Jet Engine condition monitoring, fault diagnosis and integration in maintenance practices. Gas path analysis and principles of fast response measurement methods. Instrumentation and data collection for engine monitoring. Test cells, test procedures and engine certification. Principles of operation of auxiliary systems. Engine noise and emissions. Use of computers for simulation and engine monitoring.

**VISCOUS FLOWS IN TURBOMACHINES [9 AME, EME]**

Development of the boundary layer theory. Connection with what has already been presented in other courses. Development of viscous models for turbomachinery applications and their relation with those already presented in Thermal Turbomachines II course. Boundary layers developing along the suction and pressure sides of compressor and turbine blades. Secondary floes and their calculation. Special problems related to viscous flows appearing in the turbomachinery field.

**BIOFLUID - MECHANICS [9 EME, AME]**

Elements of anatomy and physiology of the circulatory system - Blood rheology - Structure and mechanical properties of the blood vessels wall - Wave propagation in arteries - Pulsating blood flow in arteries - The circulatory system, regulation, modeling - The heart as a pump - Microcirculation - Fluid mechanics of thrombogenesis and atherogenesis - Measurements in circulatory system. Biomedical technology related to circulation, artificial heart and valves, arterial grafts, blood flow assist devices - Urodynamics - Biofluidmechanics of respiration, of hearing, smelling-Diagnostics in Biofluid Mechanics.