<p>Large-scale compressed gas storage is a critical part of green hydrogen production with offshore renewable energies. Compared with traditional floating onboard storage, subsea storage is a safer, all-weather and long-term alternative. This study presents a subsea hydrogen storage accumulator concept with a low aspect ratio (AR = 0.5). The hydrodynamics of accumulators with different free ends, namely flat tip (FT), radiused tip (RT), and approximate hemispherical tip (AHT) are investigated. The Reynolds number is about 3.3 × 10⁶. The large-eddy (LES) turbulence model is used in the numerical simulation. The time-averaged and transient flow structures, force characteristics, and surface pressure coefficient of three accumulators are compared and analyzed. In addition, the strength and influence range of the horseshoe vortex around the accumulators are quantified by the time-average bed pressure coefficient and bed shear stress amplification for the study of local scour. The results show that complex and abundant flow structures have formed in the wake of the three accumulators, including obvious arch-type vortex and hairpin vortex. The dominating frequency of vortex shedding is not obvious, and the lift coefficient also indicates a non-zero lateral force exerted on the accumulators. The main reason is that the flow is in the regime of supercritical transition. The mean lift coefficient and drag coefficient of the three accumulators are 0.63/0.30 (FT), 0.66/0.21 (RT), and 0.70/0.19 (AHT), respectively. On comparing the AHT and RT accumulators, the influence range of the horseshoe vortex in front of the FT accumulator is larger, and the fluid recirculation and downwash behind the tank are stronger. To some extent, the AHT design reduces the fluid recirculation and downwash in front and behind the accumulator, and has an inhibitory effect on local scour.</p>