Nuclear power plants or steam power plants need water to remove heat. During water pumping process vortex or swirl can occur which can cause strong turbulence in the pump inlet as well as in the air intake. Vibration and noise can also occur, which at times can damage the pump. The occurrence of vortices in pump sumps and their effects are the most common and difficult problem to encounter. The free surface vortex appears on the water surface level. In order to minimize the effect of vortex and to ensure the safety of the system, a curtain wall has to be installed to prevent a free surface vortex according to the Hydraulics Institute Standards (HIS). Currently the HI standard specifications for the installation of the curtain wall to prevent the free surface vortex is only minimal. In particular the HI standard installation guide is inadequate when it comes to diverse pump systems and also experiments show that it is inappropriate to install the guide lines inside the pipe. Hence, in order to get an optimal result, we focus on three different parameters of length (0.5D, 1D and 1.5D) and four different cases of depth (2D, 2.5D, 3D and 3.5D) and angle (30, 45, 60 and 90 degrees) for the curtain wall installation from the center of the intake pipe and from the minimum liquid level to find the optimal curtain wall installation condition in the flow characteristics inside the pipe. In this study, instead of a single-phase flow of water, a two phase flow model of both water and air is introduced into the pump inlet. The behavior of the volume ratio of water and air is checked, by means of both quality and quantity. By the installation of the curtain wall based on the new cases, the flow of free surface vortex around the pump intake is stabilized but shows differences in the internal flow of the intake due to differences in parameters. Among the different curtain wall installations, the particular case of length 2D, depth 1D and angle 90 degrees shows to be the optimal case of installation to control the free surface vortex and the internal flow of the pipe.