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Verification and validation of computational fluid dynamic simulations are performed at model and full scales for the high-speed littoral combat ship (LCS) surface combatant, including the effects of hook, interceptors, and water-jet propulsion. Predictions of the body force thrust, sinkage, and trim use a speed controller for attaining self-propulsion. Two methods for water-jet performance are used: 1) evaluation of forces based on integration of the stress over the wetted area of the hull and water-jet duct, pump casing, and nozzle (integral method) and 2) ITTC (2005) water-jet test procedure (control volume method). The comparison errors at model (resistance, sinkage, and trim) and full (power and trim) scales are satisfactory using both Froude (Fr) scaled model- and full-scale trial data, including the effects of the interceptors and water jets (WJ) on resistance/power, sinkage, and trim. For the model-scale model without WJS, the negative bottom hydro-dynamic pressure near the water-jet inlets are observed without and with the hook simulations, and experiments with the hook. The negative bottom vertical force near the water-jet inlets forthe simulations without the hook supports Savitsky's (2014) assertion that semi-displacement monohulls do not exhibit hydrodynamic lift and disproves Giles' (1992) assertion to the contrary. The hook and interceptors do not affect the pressure distribution significantly near the water-jet inlets. Forthe full scale model, the WJs induce bow up trim for the simulations and interpolated (between conditions)- and Fr scaled model-scale experiments. The negative bottom pressure and vertical force near the water-jet inlet forthe simulations disprove Giles' (1992) assertion that the WJs provide additional hydrodynamic lift. This is further supported by the comparisons of the vertical force % thrust vs. inlet velocity ratio forthe LCS, with results shown in Bulten (2005) for a high-speed motor yacht. Bulten (2005) shows positive vertical force for inlet velocity ratios ≥ 1.25. However, LCS operates in the regime of an inlet velocity ≤ 1.2; thus, consistent with Bulten (2005), the vertical force is negative. The nonlinear effects between the interceptors and WJs are small such that a linear combination can provide a reasonable approximation. [ABSTRACT FROM AUTHOR]

CFD computations are validated for course keeping and maneuvering of ONRT ship hull advancing at Froude number 0.2 in regular waves. The course keeping computations are conducted for various wave headings (0, 45, 90, 135, 180deg) with λ/L=1.0 and H/λ=0.02. The maneuvering computation is performed for a turning maneuver with 35 deg rudder deflection for the ship located initially in head waves with λ/L=1.0 and H/λ=0.02. The 6DOF motions/velocities and wave elevation are validated against available experimental data. For course keeping, the validation study focuses on the Oth, 1st and 2nd harmonic amplitude of motions/velocities. The effective and propeller power are also investigated using CFD results. For the turning maneuver, the validation study focuses on the characteristics of turning trajectory in waves and low and high frequency of motions/velocities. For course keeping, the 0"' and 2nd harmonic of motions show an average error of 30%DR whereas 1st harmonic amplitude predictions show a smaller error with an average value of 12%DR over all the wave headings. For all harmonics, the largest error value was for the stern quartering wave and the smallest value was often for the head wave conditions. The study on the propeller performance in course keeping showed that the effective power required for the ship was largest in head waves, about 30% more than the power required in calm water. The effective power decreased bv increasing the wave heading such that the values were close to the effective power in calm water for wave heading > 90 deg. The propeller efficiency was found to be higher in waves. The increase of the propeller efficiency was largest for wave heading of 45 deg, about 10% increase compared to calm water. For the turning maneuver, the trajectory was well predicted with E=2.9%D and 3.7%D for the advance distance and tactical diameter, respectively. The drift distance was under predicted by 9%D and the drift angle is predicted 87 deg whereas the experimental data shows 55 deg. The comparison of course keeping and turning showed the low frequency values are significantly affected by turning. The low frequency values of the experimental heave and pitch showed the wave is distorted by the ship motion for the second and third turning cycles. The high frequency values of turning and course keeping are similar for the heave and pitch motions and different for other motions/velocities. CFD shows good agreement for the high frequency values of heave, pitch and roll motions and low frequency values of most motions/velocities excluding heave and pitch. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics for ship hydrodynamics has made monumental progress over the last ten years, which is reaching the milestone of providing first-generation simulation-based design tools with vast capabilities for model- and full-scale simulations and optimization. This is due to the enabling technologies such as free surface tracking/capturing, turbulence modeling, 6DoF motion prediction, dynamic overset grids, local/adaptive grid refinement, high performance computing, environmental modeling and optimization methods. Herein, various modeling, numerical methods, and high performance computing approaches for computational ship hydrodynamics are evaluated thereby providing a vision for the development of the next-generation high-fidelity simulation tools. Verification and validation procedures and their applications, including resistance and propulsion, seakeeping, maneuvering, and stability and capsize, are reviewed. Issues, opportunities, and challenges for advancements in higher-fidelity two-phase flow are addressed. Fundamental studies for two-phase flows are also discussed. Conclusions and future directions are also provided. [ABSTRACT FROM AUTHOR]