Darbo metu apžvelgiami metodai pereinamiesiems procesams vamzdyne realizuoti. Aprašyta vamzdyno tėkmės pereinamųjų procesų dinamika matematinės lygtys ir sudarytas baigtinių elementų modelis skaitiniam vamzdynų pereinamųjų procesų modeliavimui. Panaudojant atgalinį slėgio bangos modeliavimą esant idealizuotam slėgio bangos sklidimo modeliui, sudaromas slėgio impulso vietos nustatymo algoritmas ir įvertinamos atsirandančios paklaidos. Realizuota programine įranga patikrinamas sudarytų modelių ir algoritmo teisingumas, bei pateikiami pasiūlymai, atsiradusioms paklaidoms mažinti. / During this research, the methods to realize the transient processes in piping systems are overviewed, also finite element method and idealized wave propagation of pressure mathematical models are set up. Using the backward pressure wave modelling at idealized pressure wave propagation model, piping system rupture location algorithm and the assessment of estimated errors are set up. With released software, the developed models and correctness of the algorithm are verified, and suggestions to reduce the resulting errors are presented.

Computational Fluid Dynamic Simulation of Intracranial Aneurysms Analysis of time-dependent changes of hemodynamic parameters - the road the clinical use Hemodynamics are involved in the genesis of intracranial aneurysms and time- dependent changes of their parameters lead to aneurysm growth, stabilization or rupture. Definition of these changes using computational fluid hemodynamics could significantly contribute to the understanding of aneurysmal development and rupture and could enable the routine use of mathematical simulations. In this study, computational fluid dynamics were performed for nine incidental aneurysms. Five aneurysms were monitored throughout time and factors leading to aneurysm rupture were analyzed. In four aneurysms the influence of the hemodynamics on the growth was defined. Major growth occurred in areas of low wall shear stress and oscillatory index. These areas increased in size during growth time. Contrary to this, neck shape remodeling occurred in areas with large wall shear stress and pressure. Throughout the follow-up of ruptured aneurysms, the minimal wall shear stress decreased, and the area of low wall shear stress increased significantly. The results indicate that decreasing values of minimal wall shear stress and increasing values of low wall shear stress area...