This CFD study aims to simulate the impact of fiber distance and position on fiber-fiber interaction within a bundle. In order to display the filtration performance of fibers at different positions, a hollow fiber membrane filtration setup based on nine fibers arranged in a 3 x 3 square array was constructed. A CFD porous media model approach was employed using the liquid phase as the main phase. The numerical simulation of multiphase flow on the average velocity of each fiber is validated by the experimental results. The presence of "bundle resistance" and "permeate competition" among fibers was confirmed by the axial liquid velocity simulation. When fiber distance was less than the fiber diameter, the interaction between fibers became notable due to "permeate competition". When fiber distance was equal to fiber diameter, the "permeate competition" effect disappeared, while the "bundle resistance" became dominant within the bundle. When the fiber distance was larger than the fiber diameter, both "permeate competition" and "bundle resistance" could be neglected. The variations of fiber flux at different positions along the fiber height also proved the distribution of axial liquid velocity and sludge density in the bundle. These results highlight the difference between fiber distance and position in the bundle that ensured the fouling deposition.