Flow characteristics around side by side square prisms with control rods are numerically investigated at
different gap ratios (g*) changing between 0.5 and 6 for Re = 73. Four different flow patterns, which
are single street mode, irregular street mode, regular street mode and two street mode, are identified
based on the gap ratio. Maximum drag reduction (%52) is obtained at g* = 6. The mean lift coefficient
has a symmetric variation between these gap ratios for the upper and lower square prisms. It can be
concluded that the control rod is an effective flow control method in terms of drag reduction.