Recently, various simulations of two-phase flows are widely accepted in many applications of flow-related designs. Among them is Hard Disk Drive (HDD) application of air flow simulation with particle trace. Air flow simulation in the cavity of HDD is one of critical areas in HDD design since it is closely tied with analysis of air flow induced vibrations and particle-driven contamination resulting in HDD failures. In this paper, the filter performance for particle collection is investigated with the effect of filter's permeability as well as the impact of air dam in HDD cavity. A imulation model is validated with the test results of cleanup time in two different cavity designs of HDD. A redesigned air dam is also found to be helping a recirculation filter collect more particles through tests and simulations.