CFD를 이용한 Spray Rail 적용 Planing Hull의 성능 특성 연구

Abstract

The spray rail is an appendage attached at the hull bottom in the flow direction. The main reason of adopting the spray rails is to generate additional lift and promote planing, and to deflect spray away from the hull which hopefully acts to reduce resistance. In this study the characteristics of spray rail applied to the modern planing hull was studied by numerical simulation using a commercial code Star-CCM+. At first, the reliability of the numerical analysis technique for the planing hull was verified by comparing with the well-known experimental results with spray rails and without them. To investigate the performance of spray rail and to separate the effect of hull form, the Fridsma model was selected for planing hull form. The hull forms with three different deadrise angles(10, 20, 30 degree) were simulated for finding the relationship between spray rail and hull performance by changing the number of spray rails(1, 2, 3ea) and the size(0.04B/2, 0.07B/2, 0.1B/2 and 0.14B/2). The spray rails on the hull can reduce the resistance, especially during planing posture. For a hull with the large deadrise angle, the performance of the spray rail is better than that of lower deadrise. For the size of the spray rail the case of 0.07B/2 is most effective. It is reasonable to apply two spray rails at high speeds and three rails in the opposite condition. For three types of hull(VPS, VWC, VWS), the simulated results shows the effects of the spray rails for the Fridsma model has almost same trend with three hulls cases. The resistance is reduced and the trim value is increased by the spray rail. Finally, it is confirmed that the spray rails help reducing the resistance and changing the running attitude at planing phase, not reaching the planing phase earlier. Through this study, it is also confirmed that the spray rails increase the longitudinal stability of planing hull.