Numerical Simulation And Analytical Methods Of Spray Resistance Of The High-speed Planning Craft

The weight of traditional displacement ship is supported by hydrostatic force, while planing craft is supported by hydrostatic and hydrodynamic force. In the high speed,planing craft is sailing with strong spray, which has a significant impact on its resistance and motion performance. Therefore, simulating spray characteristics and determining spray resistance for planing craft are of great importance to determine dynamic load and optimize hull form.3D prismatic planing craft model was used in this paper, which was same with the test model.Then the restrained sailing of prism planing craft in still water and in the waves were numerically simulated and analyzed.The software FLUENT was used for numerical simulation of planing craft under constraint. The simulation was completed in the condition that the trim angle is 3°and5°with the speed from 1.0m/s to 6.0m/s. The hydrodynamic characteristics of restrained prism planing craft in still water were researched. The resistance, flow field and bottom dynamic pressure of planing craft under the different trim angles and speeds were analyzed.These results were consistent with the test. When the speed is greater than 2m/s, the error of numerical value and trial value is less than 5%. The results show that the method proposed in the paper has better precision in research of high volume Fronde number.The spray properties of restrained prismatic planing craft in still water were researched based on the simulated results. The parameter characteristics of planing craft spray area and bottom dynamic pressure were analyzed. By using self-compiled post-processor the shape of spray area of planing craft was drawn. Meanwhile, the spray area and resistance were calculated. The relationship between average speed of sprary area and ship speed is approximately linear. The spray resistance accounts for 12~19 percent of the total resistance with the 3°trim angle, while it is 25~30 percent with the 5°trim angle.The environment of wave was simulated by using the wave-generating method of velocity boundary. Under the conditions of a certain speed、a wavelength of 2.1m 、a wave height of 0.2m, the sailing of planing craft in the wave was simulated. The spray properties of restrained prismatic planing craft in the wave which take the air load into account were researched under six cases for the 0m/s~5.0m/s speed. The bottom static pressure and the distribution of water volume fraction were analyzed. The spray shape of planing craft was drawn, and the spray resistance under different speed was calculated. When the speed is0m/s, the spray resistance is negligible, and it accounts for about ten percent of the total resistance under other speed.According to the internal mechanism of spray phenomenon and the empirical formula derived from experiments at home and abroad, the separation method of spray area was proposed in the paper. At the same time, the geometric parameters in spray area and the formulas for spray resistance were derived. Ultimately, the computing model of spray parameters and resistance of prism planing craft was established, that offered a feasible method for researching spray resistance of planing craft.