Experimental and numerical study on the scale effect of stern flap on ship resistance and flow field

The hydrodynamic performance of a ship with and without a stern flap was comprehensively investigated based on model tests and model- and full-scale simulations. The stern flap led to an increase in the stern pressure and improved the transom stern flow field, which resulted in a change in the ship attitude and decrease in resistance. The stern flap performance obtained using the full-scale ship simulation was associated with a larger drag reduction range and drag reduction effect than the extrapolated value. The scale effect of the stern flap was notable owing to the different effects exerted by the stern flaps with different scales on the hull hollow and rooster tail. In addition, the stern flap was observed to increase boundary-layer thickness near its installation location whilst lowering velocity across the propeller disk. However, this velocity reduction effect was over-predicted at the model scale compared to that at the full scale.