Vojislav Ilic

APPEARANCE OF HIGH SUBMERGED CAVITATING JET: THE CAVITATION PHENOMENON AND SONO-LUMINESCENCE

In order to study jet structure and behaviour of cloud cavitation within time and space, visualization of highly submerged cavitating water jet has been done using Stanford Optics 4 Quick 05 equipment, through endoscopes and other lenses with Drello3244 and Strobex Flash Chadwick as flashlight stroboscope. This included obligatory synchronization with several types of techniques and lenses. Images of the flow regime have been taken, allowing calculation of the non-dimensional cavitation cloud length under working conditions. Consequently a certain correlation has been proposed. The influencing parameters, such as; injection pressure, downstream pressure and cavitation number were experimentally proved to be very significant. The recordings of sono-luminescence phenomenon proved the collapsing of bubbles everywhere along the jet trajectory. In addition, the effect of temperature on sono-luminescence recordings was also a point of investigation. [Projekat Ministarstva nauke Republike Srbije, br. TR35046]

Sedimentation of non-spherical particles

Sedimentation rates of settling of single non-spherical particles within a bounded Newtonian fluid were experimentally determined as well as modelled numerically using a fully 3D boundary element method. The numerical study was then extended to the case of the unbounded fluid. Results give confidence as to the utility of the BEM as a modelling technique for sedimentation of single particles at small Reynolds numbers.

Microscopic Observation of Energy Propagation in Polymeric Fluids Crossing a Barrier

A major challenge facing tumour treatment procedures, including hyperthermia, is the inadequate modelling of the bio-heat transfer process. Therefore, an accurate mathematical bio-heat transfer model has to precisely quantify the temperature distribution within a complex geometry of a tumour tissue, in order to help optimize unwanted side effects for patients and minimize (avoid) collateral tissue damage. This study examines the three-dimensional molecular dynamics (MDs) simulation of a Lennard-Jones fluid in the hope of contributing to the understanding of the propagation of a thermal wave in fluids causing phase change i.e. irreversible gelation. It is intended to establish, from such information, a useful benchmark for application to large scale phenomena involving macro scale heat transfer. Specifically, this study examines assemblies of N particles (N = 500 atoms) and analyses the microscopic simulation of double well interaction with permanent molecular bond formation at various temperatures within the range 1–2.5Kb /eT. The dynamics of the fluid is also being studied under the influence of a temperature gradient, dt/dx, where neighbouring particles (i.e. atoms/molecules) are randomly linked by permanent bonds to form clusters of different sizes. The atomic/molecular model consist of an isothermal source and sink whose particles are linked by springs to lattice sites to avoid melting, and a bulk of 500 atoms/molecules in the middle representing the Lennard-Jones fluid. Then, this study simulates the energy propagation following the temperature gradient between the heat source and heat sink at T1 = 2.5 and T2 = 1.5 respectively. The potential equation involved in this study is given by the Finitely Extensible Non Elastic (FENE) and Lennard-Jones (LJ) interaction potential. It is observed that the atoms of the bulk start to form a large cluster (∼ 300 atoms) with long time of simulation estimated by 106 time steps where τ = SQRT(e/mσ2 ) and Δt = 10−3 . It is also obtained that the potential energy of 13.65Kb T across a barrier to establish permanent bonds giving rise to irreversible gel formation. All the parameters used in this study are expressed in Lennard-Jones units.Copyright

Monitoring of the Coalesced Ice Ball in Cryosurgery

In this paper we consider the ice ball formation in a multi-probe cryosurgical procedure. By representation of collocation polynomials and visualisation of individual ice ball formation the radius of thermal propagation from the cryoprobe tip centre can be investigated. This serves as the basis for optimisation of cryoprobe placement to the targeted tissue or the surgeons decision for the cessation of the freezing process during cryosurgery.