Flow fields around a PC cooling fan in a narrow space are studied with the experimental measurements using a hot-wire of 45-slanting sensor type and the unsteady Reynolds-averaged Navier-Stokes computations. Effects of the distance between the fan and the cooling target object downstream of it on the fan performances are focused. The numerical results agree with the experimental data. The fan characteristics between the static pressure and the volume flow rate changes greatly as the gap between the fan and the target become below a certain value. It is shown that reversed flow penetrates into the hub region of the fan casing and the effect of tip leakage vortex becomes remarkable as the gap decreases.
