In the present study, Computational Fluid Dynamics (CFD) is used to investigate the roll decay of the benchmark surface combatant DTMB-5512 ship model appended with bilge keels, sailing in calm water at different speeds (Fr = 0.0, 0.138, 0.2, 0.28 and 0.41) and with different initial roll angles. The numerical simulations are carried out using the viscous flow solver ISIS-CFD of the FINE^TM/Marine software provided by NUMECA. The solver uses the finite volume method to build the spatial discretization of the transport equation to solve the unsteady Reynolds-Averaged Navier–Stokes equations. Two-phase flow approach is applied to model the air–water interface, where the free surface is captured using the volume of fluid method. The closure to turbulence is achieved by making use of the blended Menter shear stress transport and the explicit algebraic Reynolds stress models. First, a systematic validation against the experimental data at medium speed and initial roll angle of 10° are performed; then, the effect of the initial roll angle and ship speed is later studied. Numerical errors and uncertainties are assessed using grid and time step convergence study based on Richardson Extrapolation method. A special focus on the flow in the vicinity of the bilge keels during the simulation is also investigated and presented in the form of velocity contours and vortical structure formations. The resemblance between the CFD results and experimental data for roll motion and flow characteristics are within a satisfactory congruence; however, some discrepancies are recorded for the over predicted roll amplitudes in the second and, sometimes, the third roll cycle, which appeared mostly in the cases with high initial roll angles.

中文翻译：

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基于URANSE的DTMB舰船模型自由滚动衰减数值预测

在本研究中，使用计算流体动力学（CFD）研究基准水面战斗舰DTMB-5512船模附加舱底龙骨的侧倾衰减，并以不同的速度在平静水中航行（Fr = 0.0、0.138、0.2、0.28和0.41），并且具有不同的初始侧倾角。使用FINE ^TM的粘性流动求解器ISIS-CFD进行数值模拟NUMECA提供的/ Marine软件。求解器使用有限体积方法来构建运输方程的空间离散化，以求解不稳定的雷诺平均Navier–Stokes方程。两相流方法用于模拟空气-水界面，其中使用流体体积法捕获自由表面。通过使用混合的Menter剪切应力传递和显式代数雷诺应力模型，可以实现对湍流的封闭。首先，针对中等速度和10°初始侧倾角的实验数据进行了系统验证；然后，研究初始侧倾角和船速的影响。使用基于理查森外推法的网格和时间步收敛研究评估数值误差和不确定性。还研究了在模拟过程中对舱底龙骨附近流动的特别关注，并以速度轮廓和涡旋结构形式的形式呈现。CFD结果与横摇运动和流动特性的实验数据之间的相似度在令人满意的范围内；但是，在第二个滚动周期（有时是第三个滚动周期）中记录了一些过高的侧倾幅度差异，这种差异主要出现在初始侧倾角较高的情况下。