ACTIVITY OUTLINES

The Stability and Numerical Simulation in Thermo-Fluid-Dynamics group is active in both theoretical and computational research fields of hydrodynamic stability and control as well as numerical simulation in thermo-fluid-dynamics.

The group has a consolidated background in theory and methods of hydrodynamic stability. The focus is mainly on linear stability analysis and the methods employed span from classical eigenvalues modal analysis to more modern non modal theories. The applications developed over the past years have been in the analysis of shear and capillary instabilities of two-phase flows, such as the stability of a gravitational liquid sheet subjected to surface tension and of Core-Annular Flow configurations inside a pipe. Recent research activity has focused on confined flows of non-newtonian fluids.

Another research interest is related to the analysis and the development of micro-devices devoted to flow control (and also to heat transfer cooling), the so called synthetic jets and plasma actuators. The group developed a lumped-element physical model to predict the frequency response of a synthetic jet actuator driven by a thin piezoelectric disk. The model was validated through experimental tests carried out on home-made devices having different mechanical and geometrical characteristics. More recently, the spark-jet plasma actuator device has been addressed, from both the theoretical modeling and the experimental viewpoints. Such flow control actuators can be used to modify (delay) the laminar-to-turbulent transition, to prevent or induce separation, and to enhance aerodynamic performances of airfoils (e.g., high lift).

The numerical simulation activity is conducted within two main research fields. The first one is relative to the applications of Volume of Fluid (VOF) techniques to complex two-fluid systems. Examples of recent applications are the study of the impact of drops on thin liquid films and the evolution of isolated nonlinear waves at the interface between two immiscible fluids. The second research topic, related to the numerical simulation activity, is relative to the construction of high order numerical schemes for turbulent simulations. The focus is mainly on the construction of Runge-Kutta time integration techniques with optimal energy conservation properties.

The cooperative activity with the foreign member is documented by the article on international journal:
Interfacial instability of two rotating viscous immiscible fluids in a cylinder. G. Coppola and O. Semeraro. Physics of Fluids, Vol 23, 064105 (2011). http://dx.doi.org/10.1063/1.3599507