Abstract: This paper employs Computational Fluid Dynamics (CFD) methods to numerically simulate the dispersion behavior of chemical agents injected into a water pipeline through the discharge orifices of a circular-flow chemical dosing skid. It investigates the impact of the geometric shape, area and inclination angle of these orifices on the dispersion effectiveness of the agents. The results indicate that the geometric shape of the orifices has a relatively minor impact on the dispersion range of the chemical agent, while significantly influencing the intensity of its concentration distribution; circular orifices without sharp edges thereby facilitate more effective dispersion of the agent at relatively high volume fractions within the water pipelines. When the shape of the orifices is the same, increasing the single orifice area to enhance the total outflow area of the chemical agent in the multi-orifice ring pipe can improve the volume fraction of the chemical agent at a specific point. However, this approach is not conducive to improving the axial dispersion of the chemical agent in the pipelines. Conversely, reducing the orifice area diminishes the propensity for radial dispersion of the chemical agent while enhancing its axial dispersion along the pipelines. Increasing the orifice count to expand the total discharge area enhances the axial dispersion propensity of the chemical agent while diminishing its radial dispersion propensity. Larger orifice inclination angles intensify the radial dispersion propensity of the chemical agent along the pipelines while correspondingly weakening axial dispersion, whereas smaller angles preferentially enhance axial dispersion. To maximize the protective effect of the agent against marine biofouling on pipeline walls, it is essential to suppress undesirable radial dispersion while sustaining desirable axial dispersion; therefore, circular orifices with small diameters should be adopted for the annular dosing pipe, arranged with small inclination angles in a multi-point uniform distribution configuration.

Key words: water pipelinelcircular-flow chemical dosing skidldosing orificeldispersionlnumerical simulation