A. Fatsis

Creep sagging analysis of pressure pipes

Computational Materials Science, 2006

ABSTRACT A new concept is developed to predict the mechanical behavior of pipes under the combina... more ABSTRACT A new concept is developed to predict the mechanical behavior of pipes under the combination of internal pressure and elevated temperature. A non-linear differential equation is formulated to approximate the stress/displacement distribution in these pipes, which are reinforced by rigid rings uniformly distributed along their axis. The proposed model incorporates a non-linear time-dependent stress–strain material behavior rule derived by uniaxial tests. Taking into account equilibrium equations and boundary conditions, a general analytical expression for the case of biaxial creep loading is formulated. Numerical solution and results of a typical example are included.

A new class of exact solutions of the Navier–Stokes equations for swirling flows in porous and rotating pipes

by A. Fatsis and J. Statharas

Advances in Fluid Mechanics VIII, 2010

Performance Assessment of Single and Two Shaft Gas Industrial Turbines Using Fuels of Different Calorific Values

by A. Fatsis, A. Tourlidakis, and A. Polyzakis

International Journal of Turbo and Jet Engines, 2010

Computer Simulation of Performance and Economic Assessment of a Single Shaft Gas Turbine Combined Heat Cooling and Power Plant

by A. Fatsis and A. Polyzakis

International Journal of Turbo and Jet Engines, 2010

Experimental survey of the pressure cone and temperature field of an A/T missile system

Computational Ballistics III, 2007

ABSTRACT This paper describes the characteristics of the temperature and pressure fields measured... more ABSTRACT This paper describes the characteristics of the temperature and pressure fields measured downstream of the launcher of the Russian \“FAGOT” anti-tank missile system. The experimental data were used to establish the proper location of the launcher on a vehicle used by the Greek Army. The pressure field developing at the rear of the missile launcher has the characteristics of a conical shock wave. The field was measured with an array of piezoelectric pressure transducers and a fast computer-based data acquisition system. The extent of the temperature field was established with high speed video and infra-red still photography and was confirmed with miniature thermocouple sensors. The results showed that the pressure cone intersects the ground level at a distance of 1.5 to 2.5 m behind the launcher. Typical overpressure of the shock wave was of the order of 1 to 1.8 bar. The conical shock wave breaks down into several smaller shock waves at a distance of 3 m and extends up to 15 m behind the launcher. The diameter of the cone at this location is 2.5–3.0 m. Keywords: missile launcher, measurements, pressure field, temperature field.

On the exact solution of incompressible viscous flows with variable viscosity

by A. Fatsis and J. Statharas

Advances in Fluid Mechanics IX, 2012

LNG dispersion over the sea

by A. Fatsis and J. Statharas

Air Pollution XVI, 2008

ABSTRACT A numerical study of heavy gas dispersion over sea from an LNG storage facility at Renyt... more ABSTRACT A numerical study of heavy gas dispersion over sea from an LNG storage facility at Renythousa Island in Greece is examined for the various hazards imposed on the population of the surrounding areas. The study is done by using the code ADREA-HF solving the conservation equations of mass, momentum and energy for the mixture of the heavy gas and air, as well as the mass fraction of heavy gas. Distributions of methane, ethane and propane concentrations for various time instants after the gas release are obtained, identifying the riskiest zones using scenarios based on weather forecast data. Thus the contribution of this work is to show how the available time for the authorities to safely evacuate the nearest affected areas can be evaluated. Keywords: heavy gas dispersion, Navier-Stokes equations, turbulence model, flammable plume zone. 1 Introduction Large quantities of substances that are hazardous for the public and for the environment are produced or utilized in large quantities by most modern process industries that are often sited near populated areas. These substances being toxic, radioactive, flammable or explosive during an accident in the production process, transportation or storage may provoke a release of gas (or gas-liquid) clouds or plumes that are denser than air. The density difference of the formulated \“heavy gas” introduces buoyant forces that can distort significantly

An exact solution of the Navier-Stokes equations for swirl flow models through porous pipes

Advances in Fluid Mechanics VI, 2006

ABSTRACT An exact solution of the Navier-Stokes equations for laminar flow inside porous pipes si... more ABSTRACT An exact solution of the Navier-Stokes equations for laminar flow inside porous pipes simulating variable suction and injection of blood flows is proposed in the present article. To solve these equations analytically, it is assumed that the effect of the body force by mass transfer phenomena is the ‘porosity’ of the porous pipe in which the fluid moves. The resultant of the forces in the pores can be expressed as filtration resistance. The developed solutions are of general application and can be applied to any swirling flow in porous pipes. The effect of porous boundaries on steady laminar flow as well as on species concentration profiles has been considered for several different shapes and systems. In certain physical and physiological processes filtration and mass transfer occurs as a fluid flows through a permeable tube. The velocity and pressure fields in these situations differ from simple Poiseuille flow in an impermeable tube since the fluid in contact with the wall has a normal velocity component. In the new flow model, a variation of the solutions with Bessel functions based on Terrill’s theoretical flow model is adopted. Keywords: exact solution, Navier-Stokes equations, pipe flow, laminar flow, porous media, blood flow characteristics.

A 3D Simulation of Unsteady Flow Inside Centrifugal Compressor Impellers

International Journal of Turbo and Jet Engines, 2006

Evaluation of an Euler Code with Non-Reflecting Boundary Conditions for the Analysis of 3D Flow in Compressors

International Journal of Turbo and Jet Engines, 1995

Airflow modeling analysis of the Athens airport train station

by M. Vrachopoulos and A. Fatsis

Determination of the thermal and cooling needs of the broader region of Athens

by A. Fatsis and Andronikos Filios

Renewable Energy, 2008

An original method to determine the thermal and cooling loads of the broader region of Athens is ... more

A computational method for pressure wave machinery to internal combustion engines and gas turbines

by M. Vrachopoulos, F. Layrenti, and A. Fatsis

Advances in Fluid Mechanics VI, 2006

The home of the Transactions of the Wessex Institute collection, providing on-line access to pape... more

Unsteady flow modelling of a pressure wave supercharger

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2006

Pressure wave machinery constitutes a promising device in a wide variety of applications such as ... more Pressure wave machinery constitutes a promising device in a wide variety of applications such as superchargers in automobile engines and topping devices in gas turbines. A very attractive feature is the built-in exhaust gas recirculation which provides a substantial reduction in NO x emissions of the engine. The present work presents a simple numerical model based on shock tube flow, accounting for viscous and thermal losses inside the rotor of the supercharger as well as leakage losses at the extremities of the rotor. It is validated against available experimental data of shock tube flow and on a three-port wave rotor, called a pressure divider. The model is then applied on a configuration suited for automobile engine supercharging. Comparisons with experimental data show that the present method can analyse the basic flow patterns inside the rotor, providing a useful tool for pressure wave supercharger flow predictions.

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Three-Dimensional Unsteady Flow and Forces in Centrifugal Impellers With Circumferential Distortion of the Outlet Static Pressure

Journal of Turbomachinery, 1997

This paper describes the numerical investigation of the centrifugal impeller response to downstre... more This paper describes the numerical investigation of the centrifugal impeller response to downstream static pressure distortions imposed by volutes at off-design operations. An unsteady three-dimensional Euler solver with nonreflecting upstream and downstream boundary conditions and phase-lagged periodicity conditions is used for this purpose. The mechanisms governing the unsteady flow field are analyzed. A parametric study shows the influence of the

Creep sagging analysis of pressure pipes

Computational Materials Science, 2006

ABSTRACT A new concept is developed to predict the mechanical behavior of pipes under the combina... more ABSTRACT A new concept is developed to predict the mechanical behavior of pipes under the combination of internal pressure and elevated temperature. A non-linear differential equation is formulated to approximate the stress/displacement distribution in these pipes, which are reinforced by rigid rings uniformly distributed along their axis. The proposed model incorporates a non-linear time-dependent stress–strain material behavior rule derived by uniaxial tests. Taking into account equilibrium equations and boundary conditions, a general analytical expression for the case of biaxial creep loading is formulated. Numerical solution and results of a typical example are included.

Mathematical Formulation of 3D Non‐Reflecting Boundary Conditions for Hyperbolic Equations for Internal Flows in Thermal Engines

ABSTRACT This article presents the development of inlet/outlet non-reflecting boundary conditions... more ABSTRACT This article presents the development of inlet/outlet non-reflecting boundary conditions for solving partial differential equations, applied on internal flows. The proposed method is based on Fourier decomposition of the outgoing characteristics at the inflow and outflow boundaries. The influence of non-reflecting boundary conditions on the accuracy of the flow field predictions is evaluated. Computations carried out reveal that convergence to steady state is reached faster when non-reflecting boundary conditions are used compared to the reflecting type. In case of unsteady flows, it has been found that non-reflecting boundary conditions absorb pressure waves incident to the inlet and outlet planes without creating any reflection that could contaminate the solution.

A Practical Method to Predict Performance Curves of Centrifugal Water Pumps

Applied Engineering in Agriculture, 2008

Thermodynamic analysis of gas turbines topped with wave rotors

Aerospace Science and Technology, 1999

ABSTRACT Wave rotors constitute promising gas turbine topping devices. In order to evaluate the p... more ABSTRACT Wave rotors constitute promising gas turbine topping devices. In order to evaluate the potential benefit of these configurations, thermodynamic cycle analyses are carried out for various types of gas turbines including a four-port wave rotor. The parameters chosen to vary are the efficiencies of compression and expansion processes inside the rotor, the wave rotor compression ratio and the mixing and pressure losses in the ducts connecting the wave rotor to the adjacent components of the engine. The results obtained show that almost all the engines under study benefit from the wave rotor addition and that the most significant gain is obtained for gas turbines for which the compressor pressure ratio is moderate (∼5) and the turbine inlet temperature is fairly high (&gt; 1600 K).

Preliminary analysis of the flow inside a three-port wave rotor by means of a numerical model

Aerospace Science and Technology, 1998

... Article Outline. References. ELSEVIER Abstract Clinical Eye and Vision Care 7 (1995) 129132... more

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