Assistant Professor of
Computational Fluid Dynamics
Dynamics and Stability of Interfaces in Stratified and Dispersed flow. Suspension Mechanics, Bubble Dynamics and Biomechanics. Transition to turbulence. Numerical Techniques, Finite Elements, Boundary Elements and Parallelization. Bifurcation Theory & Dynamical Systems.
 Effect of rainfall
on the flight characteristics of an airfoil: PENED (2002- Funding Organization: Greek Secretariat
of Research and Technology. Partners:
Ph.D. Thesis: Ms. Maria Vlachomitru
The goal of the project is the investigation of the dynamic development of liquid films due to shear from the surrounding boundary layer, as is the case for flow past a wing section under rainfall conditions. The experimental and numerical study of such a flow field is intended to reveal the way instabilities grow in space and time for both linear2 and nonlinear disturbances and to capture boundary layer separation and transition. Finally, an estimate of the effectiveness of the wing section under such weather conditions will be obtained and suggestions for remedial steps will be made.
of the motion and deformation of contrast agents, blood cells and capsules:
HRAKLEITOS (2003- Funding Organization: Ministry of Education of
Ph.D Thesis: Dr. Kostas Tsiglifis
Contrast agents are bubbles normally coated by a membrane in order to avoid clustering and to prevent gas dissolution. Upon application of ultrasound the bubbles exhibit strong scatter, which distinguishes them from tissue and allows for better flow visualization. Laser bubbles are also very important in the context of sonoluminescence. Red blood-cells and capsules1 are essentially drops that are also enclosed by an elastic membrane. Cell filtration, shear triggered release of an active agent in a solution, among other examples, require knowledge of the mechanical properties of capsules. Proper combination of the finite with the boundary element method is used, for the study of the interaction between contrast agents and ultrasound, and for the interaction between a capsule or a red blood cell and different flow fields5 representing different aspects of the physiological environment.
 Stability analysis of magnetohydrodynamic flows: EURATOM (2003- Funding Organization: European Commission. Partners: Greek and European EURATOM Associations.
A central issue in nuclear fusion is proper removal of the excessive amount of heat that is generated. Thus, the core of the reactor is surrounded by a mantle in which the refrigerating fluid is circulated. In this region, normally consisting of a liquid crystal melt, an interesting coupling between heat and momentum transfer takes place in the presence of the magnetic field that is generated in the core. The stability of different operation modes is very important for the optimal design of the reactor. A finite elements analysis is undertaken in order to ascertain the connectivity of different solution branches in the parameter space defined by the Grashof and Hartmann numbers. Different dynamic states are identified where static equilibrium or periodicity prevails. The same approach has already been applied for the linear stability analysis of electric bridges3 where it is the electric field that balances viscous and surface tension forces at the interface between a liquid crystal melt and air.
1. N. A. Pelekasis & J. A. Tsamopoulos "Linear stability of a gas boundary layer flowing past a thin liquid film that grows over a flat plate", J. Fluid Mech. 436, pp. 321-352, (2001).
2. N. A. Pelekasis C. Economou & J. A. Tsamopoulos, "Linear oscillations and stability of a liquid bridge in a DC electric field:" Phys. Fluids 13 (12): 3564-3581 (2001).
3. N. A. Pelekasis, Α. Gaki, A. Doinikov & J. A. Tsamopoulos, “Secondary Bjerknes forces and the phenomenon of acoustic streamers” J. Fluid Mech. 500, 313-347, (2004).
4. E Lac, D. Barthes-Biesel N. A. Pelekasis & J. Tsamopoulos "Deformation and break-up of capsules in simple shear flow." J. Fluid Mechanics 516 303-334, (2004).
5. K. Tsiglifis & N. Pelekasis, ‘Non-linear oscillations and collapse of elongated bubbles subject to weak viscous effects’, Physics of Fluids, 17(10) pp 1-18, (2005).