Calm-Water Resistance Research Of A Longitudinal Flow Type Semi-Planning Craft

In order to meet the needs of domestic civilian transportation,a longitudinal flow type semi-planning craft is proposed based on the development status of high-speed craft at China and abroad,and the calm-water resistance performance of the longitudinal flow type semiplanning craft was studied.Firstly,a model test was designed for the proposed semi-planning craft to explore the calmwater resistance performance characteristics of the semi-planning craft.At the same time,the influence of different longitudinal position of the gravity centers on the calm-water resistance performance was studied.Based on the model test,the predicting method of the calm-water resistance of semiplanning craft was carried out.Based on STAR-CCM+software,motion domain method and overlapping grid method were used to establish two reasonable calm-water resistance performance prediction models.After comparing the results of the two numerical methods with the results of the model test,it was found that the overlap grid method not only has more advantages in simulating the calm-water resistance and capturing the flow field details of the longitudinal flow type semi-planning craft but also has high precision.Via the above work,a reliable predicting model for optimization of the the resistance performace of the craft was provided.After obtaining a reliable predicting model,the effects of the dead rise of the side planning surface,the length of the central planning surface and the stern and the width of the craft on the calm-water resistance and running attitude of the semi-planning craft were explored.According to the results of the wave making at the ship stern,distribution of the fluid pressure and the percentage of the air at the bottom of the craft,the cause of various ship geometrical parameters on the calm-water resistance performance of the semi-planning craft was analyzed.Due to the better optimization effect of the stern flap on the resistance of semi-planning craft,the paper choosed some kinds of stern flaps with different sizes,different installation angles and different installation positions to analyze the influence on the calm-water resistance of the craft.By comparing the influence of different installation schemes on the wave making conditions around the semi-planning craft and the variation of resistance,the best installation schemes of stern flap is selected.Finally,the full scale ship resistance and the effective horse power of the semi-planning craft were estimated following Froude’s hypothesis.In order to reflect the influences of the airliquid mixed layer at the ship bottom,the fluid density and frictional resistance coefficient were reasonably corrected.