Assistant Professor John S.
Anagnostopoulos
School of Mechanical Engineering
National Technical University of Athens
9 Heroon Polytechniou ave., Zografou 15780, Athens
Greece
E-mail: anagno@fluid.mech.ntua.gr
Abstract: Mesh-free methods are
gaining in popularity since they are both computationally and numerically
efficient, as well as easy to implement and use even in complex problems
difficult for traditional grid-based methods. In particle methods a
continuous field is represented by sum of weighting functions centered on
particles, and the physical properties of the medium are smoothed over some
physical length.
The Smoothed Particle Hydrodynamics (SPH) method was originally developed in
1977 for the simulation of stars and asteroids movement in astrophysics, by
Bob Gingold and Joe Monaghan, and independently by Leon Lucy. It is a
powerful mesh-free particle method, which employs a representative number of
discrete particles that span a dynamic mesh used to discretize and solve the
continuum equations. A smoothing kernel function is introduced to sum up an
approximate value of the field functions from the surrounding particles.
Since its inception, the method has been applied for the simulation of many
problems in different areas, including solid, soft and granular materials,
and fluid flows. Important industrial applications range from medical
training, machinery and vehicle simulators, to special effects for movies
and electronic games. To some researchers it might constitute the next
generation simulator to replace finite element method and affect strongly
the computational field.
SPH method is now commonly used in computational fluid dynamics (CFD) and
appears to be promising for the reproduction of very complex and even
extreme flow conditions. The fluid flow equations are replaced by particle
motion equations and the particles move with the fluid, approximating the
continuous flow field. Starting from general dynamic fluid flows, SPH has
been used to simulate floating bodies, breaking waves, fluid-structure
interaction, shock wave phenomena, explosions etc., and appears to be ideal
for unsteady or transient multi-phase flows with moving boundaries and
interfaces.
However, there are several points that need further development and certain
problems that have to be addressed, like the numerical instabilities under
some conditions, the reduced accuracy of the computed pressure field, the
application of solid boundary conditions, and the turbulence modelling in
complex flows. Moreover, the large number of particles required in 3D
simulations entails large number of interactions thus increasing
computational demands. For specific applications SPH can be more
computationally expensive than the grid-based Navier-Stokes solvers.
The presentation contains the fundamentals of SPH theory, a brief review of
recent applications in fluid dynamic problems, and some current research
directions for further development.
Brief Biography of the Speaker:
John Anagnostopoulos is assistant professor in the School of Mechanical
Engineering at the National Technical University of Athens (NTUA), Greece.
He received his BS in Mechanical Engineering (1985), and his Ph.D. in
Computational Fluid Mechanics (1991) from the NTUA. He worked for several
years as principal researcher in various research projects and as R&T
consultant. He specialized in the numerical modelling of the flow field and
flow mechanisms in various industrial and physical processes, including
pulverized coal combustion, fouling, coal grinding, electrostatic
precipitation, atmospheric flows and pollutant dispersion, pollutant
formation and photochemical kinetics, pulsating flows, steel continuous
casting, metal thermal spraying, mechanical erosion wear, centrifugal pumps
and pumping installations, impulse hydro turbines.
He has developed several computer codes: COal Combustion Algorithm (COCA),
Modeling of Atmospheric Pollution (MAP), COal Grinding Algorithm (COGA),
Simulation of ELectrostatic Filters (SELF), FLow Automated Solver (FLAS),
Fast Lagrangian Solver (FLS), Hybrid Power Systems Operation Simulator (HYPSOS),
and he has been involved in feasibility studies for various industrial
innovations.
His current interests include the flow analysis and hydrodynamic design
optimization in hydraulic turbomachinery using Eulerian and Lagrangian
methods, as well as the optimal sizing and design of hydroelectric,
pumped-storage, and hybrid power plants.
