COMPUTING FACILITIES

The Laboratory Complex, in addition to the main computer center of the University, has available various computer systems for theoretical investigations, which include (in order of CPU speed) :
  Two Hewlett-Packard 710 Workstations, one 80486 PC equipped with an i-860 accelerating card, four SONY-RISC Workstations, a DEC 3100 and a SPARC+1 Engineering workstations, two 80486 PCs, on 80386 PC equipped with Weitek math co-processor, two 80386 PCs equipped with 80387 math co-processors, several 80286 and 8086 based PCs with corresponding math co-processors, mainly used for educational purposes while several plotters and digitizers are also available.
   The staff of the Laboratory has developed unique computational tools in the field of computational Aerodynamics for solving Navier - Stokes and Euler equations on curvilinear coordinates in complex configurations, for compressible and incompressible flows (finite difference and finite volume methods) and boundary element methods for full aircraft configurations.




Computational grid and pressure distribution over a vehicle.











A computer drafted topography of the greater Athens area.












Predicted velocity field over the Skiathos island (3d code).

Concentration contours over the Athens basin at 10m above ground level, at 10:00.


Examples of such activities are studies on the effects of spoilers on the lift of airfoils, slotted airfoils, pulsating flows in ducts, flows around propellers, both steady and unsteady, flows in complex terrains for siting of wind generators, flows around fuselages, flows around vehicles and flows around full aircraft configurations.









Computational grid and velocity distribution
over a simplified airplane geometry.

















Computational grid for the investigation of the aerody-
namic behavior of a highly skewed propeller.

C-type orthogonal grid around a NACA 0012
airfoil and stream function at 20 incidence.



Unsteady, compressible flow around a NACA - airfoil.

The research activities in the field of low and high speed Aerodynamics led to the development of efficient and reliable Navier - Stokes codes. The codes are based either on central finite difference descretization, or upwind flux vector splitting and flux difference splitting or Riemann methodologies. The applications concern mainly external and internal flows for aeronautical industries and contain subsonic, transonic, supersonic and hypersonic, viscous, inviscid, steady and unsteady flows. Control of the flow field, real gas effects, thermal effects, with heat addition, wall interference effects, as well as, turbulent effects are included. The compressible flow codes are extended also to incompressible ones using the artificial compressibility techniques. The incompressible versions of the code are mainly used in the field of biomedical engineering such as blood flow in arteries, urinary flows etc. Modeling of such flows help the medical diagnosis. The codes have been extended also for non-Newtonian fluids having also viscoelastic behavior, with applications in molten polymer technology, such as the die swelling problems during the process of extrusion.






                       Modelling of the anatomy of the cerebral arterial system
                       of man and the corresponding mean-velocity pulses of
                       the blood flow.















  Computational mesh and isomach lines for the viscous,
  hypersonic flow around an hyperbola (M=10, Re= 1.2 104).










                                                                                                                                             Unsteady wall shear distribution for the pulsating flow in
                                                                                                                                             arterial bifurcation.


Within the last six years there is a significant research activity of the Laboratory in the area of numerical modeling of turbulent reactive flows, two-phase flows and pulverized solid fuel combustion. The combustion research team of the Laboratory is a highly trained university based group with many years of experience in the numerical computation of hat and fluid flow problems.
This group has for long worked on the numerical simulation of turbulent two-phase reacting or isothermal flows, as well as on the modeling of combustion of gaseous, liquid and pulverized solid fuels in axisymmetric and fully 3-D burner arrangements.
                                                                                                                                                      An axisymmetric burner and the numerical grid.

The most recent achievement of the team is the development of the COCA (Coal Combustion Algorithm) computer code which mainly addressed to the advanced technology Power Industry as a useful and reliable engineering tool for the prediction of practically all the important features of pulverized coal combustion within industrial scale or semi-industrial scale furnaces operating on pulverized fossil fuels. Recently the code has been extended to calculate the in - cylinder flow of an internal combustion engine.


     Predicted contours of stream function and temperature.












                              Particle trajectories within the axisymmetric burner.
                 









    Predictions of the in-cylinder fluid motion of a motoring
    axisymmetric reciprocating Internal Combustion Engine.









                                                                                                                                                                                            3-D view of particle trajectories.


Recent Ph.D. THESES 

Name                Project                                                              

                                                                                         

Mixos A.            "A Contribution on the Aerodynamic study of a vertical axis wind     
                    generator of Darrieus type", 1985                                    

Voutsinas S.        "Theoretical and numerical analysis of 3D inviscid subsonic flows",  
                    1990                                                                 

Glekas J.           "Development of a 3D method for the dispersion of passive            
                    contaminants over complex  terrains (Athens basin case)", 1989       

Ageridis G.         "Experimental and numerical simulation of the adiabatic wind flow    
                    field over the Athens basin", 1990                                   

Papakonstantinou T. "Experimental and numerical study of the flow field around a         
                    horizontal axis wind generator", 1990                                

Thomadakis M.       "Numerical solution of compressible flows using central difference   
                    Schemes", 1991                                                       

Drikakis D.         "Development of Upwind Numerical Methods for High Speed              
                    Aerodynamics", 1991                                                  

Trifonopoulos D.    "Numerical solution of atmospheric flow field over complex           
                    terrain", 1991                                                       

Anagnostopoulos J.  "Numerical solution of concentration equation of two-phase flows in  
                    axisymmetric burners", NTUA, 1992                                    

Morfiadakis V.      "Contribution to the theoretical and experimental investigation of   
                    non-steady phenomena in turbomachines", 1992                         

Mouzakis F.         "Numerical prediction of the behavior of airfoils and wings of wind  
                    generators", 1993                                                    

Sarianos N.         "Two-phase flows with burning in 3-D geometries of boilers", 1993    

Stefanatos N.       "Analysis of the response of a Horizontal axis windturbine in a non  
                    uniform flow field", 1993                                            

Dakos K.            "Turbulent flow around airfoils using single and multi-grid          
                    methodology", 1993                                                   

Rossis K.           "Experimental and numerical study of the flow field around           
                    vehicles", 1993                                                      

Papadakis G.        "Numerical simulation of the aerodynamic and thermodynamic flow      
                    field of coal burners", 1993                                         

Alexakis M.         "Investigation of the aerodynamic behavior of highly skewed          
                    propeller"                                                           

Despotis G.         "Unstructured elements and application in the extrusion of molten    
                    polymers"                                                            

Pentaris A.         "Unsteady effects in aerodynamic flows"                              

Kaliakatsos Chr.    "Influence of the mechanical properties of the blood cells on the    
                    blood flow"                                                          

Burrys D.           "Effects of fouling on the efficiency of heat exchangers in lignite  
                    utility boilers"                                                     

Theodorakakos A.    "Development of finite volume method for 3-D fluid flows in          
                    reciprocating internal combustion engines"                           

Papou Th.           "Development of numerical method for the calculation of unsteady     
                    flows in moving boundaries"                                          

Ferlias G.          "Development and construction of a flowmeter using the principle of  
                    vortex shedding"



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