The objective of this study is to understand and control the phenomena generated by a plume in a semi-ventilated enclosure using velocity fields. The enclosure has a rectangular cross-section and twenty openings located near the floor on two side walls. Each side wall has ten openings distributed over two horizontal rows on the axis (0y) in equal number. The plume is created by a linear source. The study is carried out in a steady state. To solve the mass and momentum conservation equations, the Direct Numerical Simulation (DNS) method and the finite volume method were used to discretize the differential equations. The fine non-uniform regular mesh was chosen to reduce calculation errors, to have a rapid convergence of the conservations equations and a stable result which approaches reality. As discretization scheme, we used the QUICK scheme and schema "Body Strength weighted for the resolution of the pressure. We have shown the influence of the reduced Grashof number on the fields of mean velocity, velocity along the (0z) w axis, velocity along the (0x) u axis and on the differential static pressure profiles. We compared the dimensionless differential static pressure results against the relevant experimental and the numerical calculations results. The results obtained showed that the velocity plume w can take the positions centered, tilted to the left and tilted to the right in the enclosure according to the increase in the number of reduced Grashof The velocity plume w reaches the ceiling where it is destroyed and go back down to the bottom of the enclosure. The maximum absolute values of the velocity w in the plume and u at the openings increase with the increase in the reduced Grashof number. The neutral height has for value <i>z+=0.05</i>. At the openings, cool air enters the enclosure through openings near the floor and below neutral height, and hot air exits through openings above neutral height. The comparison of the dimensionless differential static pressure results with against the relevant experimental and numerical calculations results is concordant.