Application of Flow Control Devices to Improve Propeller Cavitation Performances

摘要

For blunt aft-body shape of the vessels such as large tankers, there sometimes have been reported the existence of considerably unstable flow behavior around propeller aperture. In order to improve the wake characteristics around the propeller disk, a pair of vortex generators was adopted as the flow control devices. Extensive model tests have been performed to investigate the effect of flow control devices on the propeller cavitation performances together with serial tests to determine the shape and the optimal position of the generator to re-duce the wake peak as much as possible. Numerical computations are also carried out to investigate the effect of the vortex generator on the wake field and its hydrodynamic performances. Reynolds averaged Navier-Stokes (RANS) equations in conjunction with a Reynolds-stress turbulence model and wall function were solved. Through the application of the vortex generator to those vessels, the underlying unstable flow patterns were completely vanished. The observed cavity extents as well as the pressure fluctuation amplitudes were significantly reduced, which imply that the cavity behavior were considerably stabilized. In full scale, the sea trials for Aframax tankers were carried out to confirm the effect of the vortex generators. The pressure amplitudes and the vibration levels were measured and compared with those of model tests.