The Archimedes spiral hydrokinetic turbine (ASHT), as a novel type of horizontal-axis hydrokinetic turbine, is well suited for deployment in the low-speed ocean current environment. Besides, integrating hydrokinetic turbines within a duct stands out as a prospective approach to enhance the efficiency of energy harvesting. In this study, a duct is implemented with the aim of enhancing the performance of ASHT. Using the commercial code program ANSYS-FLUENT, the Reynolds-averaged Navier-Stokes (RANS) equations are solved along with the SST k-ω turbulence model to elucidate the distinctive hydrodynamic characteristics of ASHT and its ducted configuration (DASHT). The findings revealed a consistent outperformance of the DASHT over the ASHT, achieving a notable maximum improvement of 122% in the power coefficient (CP). The ASHT exhibits turbulence near the blade tips, generating large spiral tip vortex, while the DASHT, with its duct, induces significant turbulence, resulting in a wider range of vortex structures. Furthermore, the DASHT shows better energy harvesting due to enhanced diffusion under yawed flow. The wake asymmetry and increased turbulence are observed as the yaw angle increases, affecting vortex structures differently in ASHT and DASHT. At higher yaw angle, the DASHT vortex splits into two parts, contributing to a more complex wake structure.