Mississippi State University has a subsonic closed return wind tunnel facility with an open test section configuration. This research analyzes the test section flow quality using a numerical approach and explain how the diffuser's collector suppresses unsteadiness. Previous experiment assessed the flow quality at the wind tunnel without the collector, and velocity was measured using a pitot-static probe and hot wire. The results show a numerical comparison between the two configurations, with and without the collector, understand the effect of the diffuser 's collector on steadiness and uniformity. This paper will describe the wind tunnel facility and give further details about the measurements tools and the set up, and then introduce the numerical method used and analyze the cases of study and their results.