Amin Najafi, مهدی رایجی, Mohammad Reza Najafi,
Volume 20, Issue 44 (10-2024)
Abstract
The wet surface caused by water spray is one of the factors of creating resistance in high-speed floats. On this basis, the effect of the sprayer appendage in reducing the buoyancy resistance has been investigated and the effect of its geometric characteristics, including the bottom angle, width and number of spray rails, on the hydrodynamic components and the buoyancy resistance has been investigated using a numerical method. The results of numerical simulations have been validated with similar laboratory data for the float without appendages. Taguchi's method has proposed 18 test designs, that each test design is simulated in two general positions of spray rails (in line with the chine and parallel to the keel) for the transverse landing number of 1.99 and 3.33. The results show that the two geometric characteristics of the bottom angle and the number of sprays have a direct relationship with the increase in the landing number of the float, so that in the flight mode, the positive bottom angle with the highest number of rail sprays has caused a greater decrease in the resistance of the float, in addition to the optimal value of the width geometric characteristic The rail spray has decreased with the increase of Froud number, as a result, the width of the rail spray has an opposite relationship with the increase of Froud number. Also, spray rails parallel to the keel have a more effective role in reducing floating resistance than spray rails in line with the chine. The amount of trim and rise of the float for the spray of rails parallel to the keel is less compared to the spray of rails parallel to the chine, which reduces the possibility of longitudinal porpoising instability in the float.
