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 Wi...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 to 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 by detailed analyses of unsteady flow field and resulting wave pattern.展开更多
在黏性流动模拟中,近壁流动在物面法向方向上的速度梯度远大于切线方向,呈现出显著的各向异性特征.传统的各向同性笛卡尔网格方法在捕捉边界层流动细节时面临网格数量剧增和计算效率下降的挑战.针对这一问题,提出了一种基于自适应法向...在黏性流动模拟中,近壁流动在物面法向方向上的速度梯度远大于切线方向,呈现出显著的各向异性特征.传统的各向同性笛卡尔网格方法在捕捉边界层流动细节时面临网格数量剧增和计算效率下降的挑战.针对这一问题,提出了一种基于自适应法向射线加密(adaptive normal ray refinement,ANRR)的笛卡尔网格黏性流体仿真方法.该方法的核心要义在于,根据物面切线方向上的角度变化程度来自适应生成法向射线种子点,在法向射线附近进行网格加密,以精确捕捉边界层流动特征,同时在射线之间采用较粗糙的网格过渡,从而在保证计算精度的前提下有效减少整体网格数量.然后利用插值构建了射线间的高效信息传递技术,确保流场求解过程中的准确性.最后,对层流平板、低雷诺数圆柱绕流以及NACA0012翼型绕流等典型算例进行模型验证.结果表明,与传统几何自适应加密网格方法相比,ANRR网格方法在边界层流动区域显著减少了网格规模,在保持高精度的同时提升了计算效率,为自适应笛卡尔网格的黏性流动问题高效求解提供了新的解决方案.展开更多
基金the research in the promotion program for international collaboration supported by Osaka Universitysupported by the Ministry of Trade,Industry and Energy(MOTIE),Korea,through the project“Technology Development to Improve Added Resistance and Ship Operational Efficiency for Hull Form Design”(Grant No.10062881)+1 种基金the Lloyd’s Register Foundation(LRF)-Funded Research Center at Seoul National UniversityAdministrative support was also received from RIMSE and ERI at the Seoul National University.
文摘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 to 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 by detailed analyses of unsteady flow field and resulting wave pattern.
文摘在黏性流动模拟中,近壁流动在物面法向方向上的速度梯度远大于切线方向,呈现出显著的各向异性特征.传统的各向同性笛卡尔网格方法在捕捉边界层流动细节时面临网格数量剧增和计算效率下降的挑战.针对这一问题,提出了一种基于自适应法向射线加密(adaptive normal ray refinement,ANRR)的笛卡尔网格黏性流体仿真方法.该方法的核心要义在于,根据物面切线方向上的角度变化程度来自适应生成法向射线种子点,在法向射线附近进行网格加密,以精确捕捉边界层流动特征,同时在射线之间采用较粗糙的网格过渡,从而在保证计算精度的前提下有效减少整体网格数量.然后利用插值构建了射线间的高效信息传递技术,确保流场求解过程中的准确性.最后,对层流平板、低雷诺数圆柱绕流以及NACA0012翼型绕流等典型算例进行模型验证.结果表明,与传统几何自适应加密网格方法相比,ANRR网格方法在边界层流动区域显著减少了网格规模,在保持高精度的同时提升了计算效率,为自适应笛卡尔网格的黏性流动问题高效求解提供了新的解决方案.
