This current work investigates the effect of duct and number of blades on the hydrodynamic performance of
the horizontal axis tidal stream turbine (HATST). The numerical method based on Reynolds averaged Navier-
Stokes (RANS) equations is employed to compare the hydrodynamic performance for various cases of this
device. For validation of the numerical results, a 3-blade HATST without-duct has been compared against
experimental data. The analysis and comparison of the simulation results show that using duct for HATST has
increased the power coefficient, the torque coefficient, the trust coefficient, and the force on the blade. In addition,
the simulation results of the cases with a greater number of blades shows that the trust coefficient increased
and the force on the blade decreased. Therefore, it is recommended to use ducted HATST with a great number
of blades to extract more energy from the tidal stream.