The added resistance of a ship in waves can be related to ship-generated unsteady waves. In the present study, the unsteady wave-pattern analysis is applied to calculate the added resistance in waves for two modified Wigley models using a Cartesian-grid method. In the present numerical method, a first-order fractional-step method is applied to the velocity-pressure coupling in the fluid domain, and one of volume-of-fluid (VOF) methods is adopted to capture the fluid interface. A ship is embedded in a Cartesian grid, and the volume fraction of the ship inside the grid is calculated by identifying whether each grid is occupied by liquid, gas, and solid body. The sensitivity of the location of measuring position of unsteady waves as well as the number of solution grids is examined. The added resistance computed by direct pressure integration and wave pattern analysis is compared with experimental data. In addition, nonlinear characteristics of the added resistance in waves are investigated with detailed analyses of unsteady flow field and resulting wave pattern.

船舶在波浪中增加的阻力可能与船舶产生的非稳态波浪有关。在本研究中，应用非恒定波动模式分析来使用笛卡尔网格方法计算两个修改的Wigley模型的波动附加电阻。在目前的数值方法中，将一阶分数步法应用于流体域中的速度-压力耦合，并且采用一种流体体积（VOF）方法来捕获流体界面。将船舶嵌入笛卡尔网格中，并通过识别每个网格是否被液体，气体和固体占据来计算船舶在网格内部的体积分数。检查了非恒定波测量位置的位置以及溶液网格的数量的敏感性。通过直接压力积分和波形分析计算出的附加阻力与实验数据进行了比较。此外，还通过详细分析非定常流场和所产生的波型，研究了波浪中附加电阻的非线性特性。