计及船体姿态变化的水池阻塞效应数值研究

Numerical study on the blockage effect of a towing tank considering ship motion

在水池进行船模试验,特别在水池尺度较小、船模尺度相对较大时,必然遇到阻塞效应问题,必须予以修正。本文以KCS船为对象,计及自由度,计算无限域及1.5%、1.8%、2.2%、3.0%阻塞比的船模阻力以及船体的升沉和纵摇,另外计算了船宽、池宽比为0.16、0.18、0.21的船模阻力,分析了船宽池宽比对阻塞效应的影响。随阻塞比的增大,船模总阻力变化更加明显;通过不同公式的修正结果对比,建议在阻塞比小于1.5%的拖曳水池进行阻力试验,且当船阻塞比小于1.8%时,推荐斯科特公式和基于平均横剖面积的平均流修正公式作为主要的修正手段,船宽、池宽的比值也是阻塞效应修正不可忽略的因素。

When performing experiments in a towing tank, if the tank is small relative to the ship′s model, the block-age effect cannot be neglected and must be corrected. Using a KCS ship as the object, taking a finite degree of free-dom into account, and using the ship′s resistance with 1.5%, 1.8%, 2.2%, and 3.0% blocking ratios, the heave and pitch of the ship were calculated. In addition, the resistance of the ship, with ship breadth to tank breadth ratios of 016, 0.18, and 0.21, was calculated, and the influence of ship breadth to tank breadth ratio on the blockage effect was analyzed. Along with an increase in the blockage ratio, the total change in resistance was obvious. According to the results of this correction, the blockage ratio should be less than 1.5%. When the blockage ratio is less than 1.8%,the Scott formula and average flow formula based on the average transverse section are suggested as the major means of correction. The ratio of ship breadth to tank breadth cannot be ignored in the correction of the blockage effect.