船体风机叶片对中速船水动力性能影响的计算分析

The importance of reducing ship resistance is growing considerably as a result of the increase in atmospheric emissions and the drive towards green shipping through decarbonization.Until this point,Energy Saving Devices(ESD),in particular,Hull Vane®(HV),have been widely applied as a potential technique for reducing wave-making resistance for vessels with higher Froude Number(Fr).The advantages of HV for a medium-speed vessel,where the wave-making component accounts for almost 50%of total resistance,have yet to be investigated.This study presents the computational analysis of the KCS model(1∶75.5);for a particular trim condition by using the VOF method and RANS solver.The hull acts as a candidate vessel for the class of medium-speed characteristics.A total of 36 numerical simulations were carried out to study the changes in resistance and motion characteristics of the vessel with and without HV.To validate the numerical setup,the experimental work of Hou et al(2020)on the DTMB hull was used.The effectiveness of HV can be comprehended by the reduction percentage in total resistance,trim,sinkage,and transom wave height,in comparison to bare hull condition.The reduction in total resistance extends up to 6%for Fr=0.32 with configuration 2 with negative AoF.The CFD results indicate that there is a reduction in trim up to 57%for the maximum speed with a corresponding Fr=0.34 with a positive angle of foil(AoF).The trim correction effect is increasing with the depth of submergence of HV.Concerning sinkage,there occurs nearly a 31%reduction for Fr=0.34 with a positive AoF.There exists a substantial reduction in the height of the transom wave with the inclusion of HV,the results of which are discussed in detail.From the presented results,retrofitting the Hull Vane®is effective in the selected speed range but pronouncing as the speed of the vessel increases.

Application of IITM-RANS3D to free-fall water entry of prismatic and non-prismatic finite wedges

High-speed watercraft and ships undergo coupled motions which make the front portion of the hull exit and violently re-enter water.This induces short-term slamming loads that may compromise the structural integrity of the hull.The slamming of the bow can be modeled as straight wedges of different deadrise angles(DRAs)falling into water from different heights.The advent of computational fluid dynamics has allowed the problem of wedge-slamming to be simulated using the full Navier-Stokes equations thus complementing the pioneering studies based on experiments.Recently,most researchers are opting to use commercial software to simulate the wedge-impact problem as it allows access to overset meshing algorithms which are robust in modeling the wedge as a moving body.Embedded boundary methods(EBMs)offer some advantages over overset meshing in that the mesh only needs to be generated once and Cartesian mesh-based solvers can be implemented.However,the application of EBMs to wedge-impact has been limited in the literature and merits further development.In this context,we investigate the applicability of the fast-fictitious-domain(FFD)based embedded boundary treatment to simulate the violent water-entry of wedges.We extend our in-house Navier-Stokes model IITM-RANS3D to handle floating bodies through integration of a rigid-body dynamics solver and an algorithm to embed three-dimensional stereolithography(STL)geometries as solids over a Cartesian mesh.The proposed algorithm is extensively benchmarked against variable DRA wedge-slamming experiments reported in the literature as well as constant DRA wedge-slamming experiments performed in-house.Very good agreement is reported in terms of the time-history of hydrodynamic impact pressures measured at various locations on the hull as well as the wedge motion responses thus demonstrating the suitability of FFD for simulating the coupled hydrodynamics of slamming for simplified hull geometries.