This paper establishes a three-dimensional turbulence model using the CFD method in OpenFOAM. It compares and analyzes the effects of spacing ratios (L/D = 1.5~6.0) at Reynolds number Re = 3900 on the wake flow characteristics, force coefficients, Strouhal number, mean pressure coefficient, and mean velocity distribution together with the flow mechanims, for both the single-row three-cylinder and the three-row three-cylinder configurations. The research results show that the wake flow patterns are classified into four types: reattachment flow (reverse flow reattachment), reattachment flow (reverse flow without reattachment), narrow wake impact, and synchronized detachment. The critical spacing ratio for the three-row three-cylinder configuration is L/D = 3.5, which is smaller than the critical spacing ratio of L/D = 4.0 for the single-row three-cylinder configuration. The drag coefficient, Strouhal number, and lift coefficient root-mean-square values of the three-row three-cylinder are generally higher than those of the single-row three-cylinder structure, and a desynchronized Strouhal number phenomenon is observed in the three-row three-cylinder configuration. The trend of mean pressure coefficient distribution of the single-row three-cylinder is similar to that of the central column of the three-row three-cylinder. For the outer columns of the three-row three-cylinder at small spacing ratios, the location of positive pressure is closer to the central column side. The gap flow mean velocity in the three-row three-cylinder configuration is relatively higher. This study provides a reference for the hydrodynamic calculation of pile groups in engineering applications.