09458 - Fluid Dynamics

Learning outcomes

The objective is to give the students the basic information in fluid mechanics and gas dynamics required to understand the behavior of all the airbreathing propulsion systems.

Course contents

Module 1: Fluid Dynamics

Introduction to tensorial analysis. Eulerian/Lagragian description. Reynolds transport theorem. Conservation of Mass. Conservation of Momentum. Conservation of Energy. Constitutive relations for Newtonian and non Newtonian fluids. Entropy balance. 

System of equations for fluid mechanics. Non dimesional analysis. Finite difference methods for convection-diffusion. Natural and forced convection. Low Reynolds number flows, Stokes flow. High Reynolds number flows. Euler equations. Irrotational flows: vorticity and circulation. Potential flows.

Boundary layer. Solution methods. Blasius solution.

Outer solutions for compressible flows. Small perturbation approach for subsonic and supersonic flows. Shock equations.

Module 2:  Thermodynamic System

Classification of machinery. 
Water as a potential fluid: characteristics and Ts and hs diagrams. 
Conservation of mass. Energy conservation: first principle for a closed system and for an open system (mechanical and thermal). Entropy and enthalpy. 
Ideal gas and ideal fluid: definition, major transformations and their representation on the Ts, hs diagrams. Work  and efficiency, polytropic and isentropic efficiency for a compression and an expansion. 
Combustion: definition of stoichiometric air, excess air, lower heating value. 

Gas turbine thermodynamic cycle 
Generality, Brayton cycle, simple plant configuration and  cycle representation on the diagram Ts. Conditions for the representability of the cycle in the Ts diagram. Thermodynamic analysis of gas turbine self-sustaining condition. Assessment of performance. Condition of maximum useful work and maximum efficiency. 
Regenerative cycle, thermodynamic diagrams, problems and limitations in employment. 
Cycle  with separated compression phases (inter-cooling): Schematic diagram and thermodynamic conditions. Complete inter-cooling, condition of maximum useful work, problems and limitations in employment. 
Post-combustion cycle: Schematic diagram and thermodynamic process. 

Compression refrigeration cycle 
Definition of COP. Cycle at saturated vapor compression cycle (biphasic with intercooler, dual-separator, dual-separator with bubbler), biphasic compression cycle with two temperatures of vaporization. Characteristics of fluids for refrigeration equipment and their classification. 
Applications of refrigeration cycles to liquefaction of hydrogen and oxygen.

Readings/Bibliography

Lecture notes of Prof. Piva

Sistemi energetici e loro componenti, 2a ed., G. Negri di Montenegro, M. Bianchi, A. Peretto, Pitagora Editrice Bologna

Assessment methods

The final exam will be divided in two different phases:

1) module 1 - written examination followed by an oral discussion  
2) module 2 - oral examination

Office hours

See the website of Elisabetta De Angelis

See the website of Stefania Falfari