Analysis of scale effects on drag and recirculation zones in hammerhead fairing space launchers

Accurate prediction of drag is essential in space launcher design, but it is complicated by scale effects in wind tunnel testing, due to Reynolds number sensitivity. This CFD study investigates flow recirculation in boattail regions across subsonic to supersonic regimes and their effects on drag generation. Emphasis is placed on how Reynolds number affects flow detachment and reattachment, guiding reliable extrapolation from scaled models to full-scale configurations. Findings indicate that base drag dominates in subsonic flows, while fairing dominates in supersonic flows. In the subsonic regime, the recirculation zone remains unaffected, varying the scale. In supersonic, its size decreases significantly.