This study examines the flow occurred when a cylindrical tube is set up in swirling flow in a horizontal tube. The working fluid used for numerical analysis is water at 30℃, and in a test tube of 90mm diameter the evaluation was performed at Reynolds number of 10,000, 15,000, 20,000, and 25,000. Unstructured grid, which is the combination of tetrahedron and hexagonal grids, was utilized for this numerical study. Turbulent model applied in this study is k-ε 2 equation model, while standard wall functions were employed to the area adjacent to walls. Recirculation zone, which is arisen owing to the inflow of fluid along a tangential line, is verified.