Abstract
Numerical simulations were conducted by using LES（Large Eddy Simulation）with DSM（Dynamic Smagorinsky Model）about the axial flow small fan for cooling electronic devices. In this study, the tested fan has an obstacle located in the suction side. Distance from the fan to obstacle is 20 mm. The flow pattern around the fan blades and RMS of pressure fluctuation on the fan blade surfaces were compared under the conditions of with and without obstacle. The flow direction into fan was axial under the condition of without obstacle. On the other hand the flow direction into fan was radial under the condition of with obstacle. This radial direction inflow to the fan caused the expansion of negative pressure region due to the separation from the top of casing, which enlarged tip vortex region and increased pressure fluctuation on suction side blade surface. Moreover the radial inflow caused the reduction of axial flow velocity at the blade tip, which increased pressure fluctuation on pressure side blade surface due to the interference between tip vortex and blade surface.
