SUMMARYTo resolve the characteristics of a highly complex flow, a lattice Boltzmann method with an extrapolation boundary technique was used in aneurysms with and without transverse objects on the upper wall, and results were compared with the non-stented aneurysm. The extrapolation boundary concept allows the use of Cartesian grids even when the boundaries do not conform to Cartesian coordinates. To ease the code development and facilitate the incorporation of new physics, a new scientific programming strategy based on object-oriented concepts was developed. The reduced flow, smaller vorticity magnitude and wall shear stress, and smaller du/dy near the dome of the aneurysm were observed when the proposed stent obstacles were used. The height of the stent obstacles was more effective to reduce the vorticity near the dome of the aneurysm than the width of the stent. The rectangular stent with 20% height-of-vessel radius was observed to be optimal and decreased the magnitude of the vorticity by 21% near the dome of the aneurysm.

SUMMARYSpray impingement has been a major interest of researchers in the areas of spray cooling, internal combustion, fire suppression and spray cooling, etc. for a long time. Numerous studies have been done in the area of spray cooling. Spray cooling with phase change takes advantage of relatively large amounts of latent heat and is capable of removing high heat fluxes from the surface, which has generated the interest of many researchers. In this paper, the turbulent characteristics of vapor formed during the spray impingement are studied. Water and gasoline are used in the numerical analysis of the two-phase spray impingement on a heated wall. Hybrid turbulence modeling was used for the analysis where the subgrid scale model was employed away from the wall and k-model was used near the wall. Gasoline, at 298 K, was sprayed on the heated wall, kept constant at 650 K. The surrounding temperature was maintained at 400 K at the start of the simulation. In case of water and gasoline at Reynolds number 2750, the heated wall was kept constant at 400 K and the surrounding temperature was maintained at 298 K at the start of the simulations. The nozzle diameter of 100 m was used for this study, with the nozzle plate spacing ratio at 10. The spray was impinged on the flat plate at angles of 0, 15, and 30 • . Root mean-squared velocities and turbulent heat flux were plotted in the water spray impingement for the different angles of impingement. The effect of turbulence on the heat transfer was observed. The effect of vortex motion on the turbulent heat flux values was analyzed using different Reynolds numbers of impingement and at different angles in case of gasoline. The turbulent heat flux attained the maximum values with high vortex formation. Upwash of fluid transported heat away from the wall, producing higher heat flux values in the region.