A NUMERICAL STUDY FOR REDUCTION OF RUDDER

초록

In recent practices, a half circular prismatic bar protruding beyond the concave surface of the horn facing the gap has been formed along the centerplane of a rudder to lessen the gap flow between the horn and movable portion of the rudder system. If a flow through the gap of a rudder is reduced considerably through this approach, previous numerical studies indicate that not only the gap flow but also the rudder cavitation can be noticeably diminished. In the present study, numerical simulations on two-dimensional rudder sections are performed to show that the blocking ability of the single centre bar can be improved with proper choice of the sectional shapes. Moreover, a pair of blocking bar attached symmetric to the centerplane on the opposite convex surface of the movable portion is suggested in the study as well to circumvent the difficulties arise in practical application of the single centre bars. The bars are placed near the outer edges of the gap easily accessible at the maximum rudder angle to allow simple installation of the device even in a maintenance period of a ship. It is found that the pair of blocking bar further improves the blocking effects and application to a practical three-dimensional rudder also backs up the fact.