International Shipbuilding Progress - Volume 60, issue 1-4

Authors: Larsson, Lars

Article Type: Other

DOI: 10.3233/ISP-130103

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 1-1, 2013

Authors: Stern, Frederick | Yang, Jianming | Wang, Zhaoyuan | Sadat-Hosseini, Hamid | Mousaviraad, Maysam | Bhushan, Shanti | Xing, Tao

Article Type: Research Article

Abstract: 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. Show more

Keywords: CFD, ship hydrodynamics, free-surface/interfacial flow, motion, turbulence, high-fidelity simulation, V&V, captive and free running, wave breaking, spray and air entrainment

DOI: 10.3233/ISP-130090

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 3-105, 2013

Authors: Eça, L. | Hoekstra, M.

Article Type: Research Article

Abstract: This paper discusses Verification and Validation for CFD applications. It emphasizes the differences between the mathematical problem of “solving the equations right” (Verification) and the science/engineering activity of “solving the right equations” (Validation). A clear distinction is made between Code Verification (error evaluation) and Solution Verification (error estimation) and procedures based on grid refinement studies are presented and discussed for both activities. The paper presents examples of Code Verification for Reynolds-Averaged Navier–Stokes solvers using the Method of the Manufactured Solutions; Solution Verification exercises including the KVLCC2 tanker at model and full scale Reynolds number and two examples of the application …of the ASME V&V 20 Validation procedure. This paper is written to stimulate a conscientious approach to CFD in marine applications. Show more

Keywords: Verification, validation, CFD, grid refinement, uncertainty quantification

DOI: 10.3233/ISP-130083

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 107-141, 2013

Authors: Fu, T.C. | O'Shea, T.T. | Judge, C.Q. | Dommermuth, D. | Brucker, K. | Wyatt, D.C.

Article Type: Research Article

Abstract: Over the past few years much progress has been made in Computational Fluid Dynamics (CFD) in its ability to accurately simulate the hydrodynamics associated with a deep-V monohull planing craft. This work has focused on not only predicting the hydrodynamic forces and moments, but also the complex multiphase free-surface flow field generated by a deep-V monohull planing boat at high Froude numbers. One of these state of the art CFD codes is Numerical Flow Analysis (NFA). NFA provides turnkey capabilities to model breaking waves around a ship, including both plunging and spilling breaking waves, the formation of spray and the …entrainment of air. NFA uses a Cartesian-grid formulation with immersed body and volume-of-fluid methods. The focus of this paper is to describe and document a recent effort to assess NFA for the prediction of deep-V planing craft hydrodynamic forces and moments and evaluate how well it models the complex multiphase flows associated with high Froude number flows, specifically the formation of the spray sheet. This detailed validation effort was composed of three parts. The first part focused on assessing NFA's ability to predict pressures on the surface of a 10 degree deadrise wedge during impact with an undisturbed free surface. Detailed comparisons to pressure gauges are presented here for two different drop heights, 15.24 cm (6 in) and 25.4 cm (10 in). Results show NFA accurately predicted pressures during the slamming event. The second part examines NFA's ability to match sinkage, trim and resistance from Fridsma's experiments performed on constant deadrise planing hulls. Simulations were performed on two 20 degree deadrise hullforms of varying length to beam ratios (4 and 5) over a range of speed-length ratios (2, 3, 4, 5 and 6). Results show good agreement with experimentally measured values, as well as values calculated using Savitsky's parametric equations. The final part of the validation study focused on assessing how well NFA was able to accurately model the complex multiphase flow associated with high Froude number flows, specifically the formation of the spray sheet. NFA simulations of a planing hull fixed at various angles of roll (0, 10, 20 and 30 degrees) were compared to experiments. Comparisons to underwater photographs illustrate NFA's ability to model the formation of the spray sheet and the free surface turbulence associated with planing boat hydrodynamics. Overall these three validation studies provide a detailed assessment on the current capabilities of NFA to predict the hydrodynamics of a deep-V planing hull. Show more

Keywords: CFD, planing craft, hydrodynamics

DOI: 10.3233/ISP-130087

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 143-169, 2013

Authors: Chase, Nathan | Michael, Thad | Carrica, Pablo M.

Article Type: Research Article

Abstract: Simulations of the free running submarine model DARPA Suboff in a horizontal overshoot maneuver are presented. To perform the simulations, the fully appended hull was fitted with the conceptual submarine propeller E1619. The overset flow solver CFDShip-Iowa v4.5 was used to perform the computations, including coupling with the propeller code PUF-14. Propeller open water curves were obtained for two grids over a wide range of advance coefficients covering high to moderately low loads, with results compared to available experimental data. The open water curves were also simulated with the coupled CFDShip-Iowa/PUF-14 approach. While computations are performed with delayed detached-eddy …simulation (DDES), simulations with Reynolds-averaged Navier–Stokes (RANS), detached-eddy simulation (DES) and with no turbulence model were also performed. Results show that RANS overly dissipates the wake while the solution with no turbulence model shows unphysical instability in the tip vortices. Overall, open water curves are predicted well by the discretized propeller and by the coupled CFDShip-Iowa/PUF-14 approach. The towed DARPA Suboff hull fitted with sail, rudders and stern planes was simulated and results were compared against experimental data, showing satisfactory results. Self-propulsion computations of the DARPA Suboff fitted with the E1619 propeller were performed and the resulting propeller performance analyzed, both using a rotating gridded propeller and the CFDShip-Iowa/PUF-14 approach. A 20/10 overshoot maneuver is demonstrated with both approaches, showing that the results are similar when the propeller remains close to straight-ahead conditions, but trends between approaches tend to diverge for large wake distortions and low advance ratios. A more complex simulation of a surfacing maneuver of the submarine in waves is demonstrated showing the potential of the approach to tackle simulations including massive free surface deformations in a realistic environment. Show more

Keywords: Overset grids, submarine, propeller, self-propulsion

DOI: 10.3233/ISP-130088

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 171-205, 2013

Authors: Kim, Sung-Eun | Rhee, Bong Jae | Miller, Ronald W.

Article Type: Research Article

Abstract: This study is concerned with the turbulent shear flow around the DARPA SUBOFF body undergoing a turning maneuver at drift. Steady Reynolds-averaged Navier–Stokes (RANS) equations were solved in a rotating frame of reference down to viscous sub-layer using two different k–ω turbulence models. Grid-convergence of the numerical solutions was ascertained using three systematically refined grids with up to 19 mln elements. The Wilcox' k–ω model predictions closely reproduce the salient features of the flow such as the cross-flow separation, the streamwise vortices, and the resultant force and moment acting on the body. The change in the effective drift angle along …the body in turning strengthens cross-flow on the aft body and augments side force. It still remains a challenge to accurately resolve the sail vortex over a long distance. The computations showed measurable effects of the sting on the force and moment. Show more

Keywords: RANS, SUBOFF, maneuvering, drift, turning

DOI: 10.3233/ISP-130100

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 207-231, 2013

Authors: Kim, Keunjae | Leer-Andersen, Michael | Werner, Sofia | Orych, Michal | Choi, Youngbok

Article Type: Research Article

Abstract: With environmental concerns becoming one of the most important issues facing the shipping/ship-building industry today, SSPA has witnessed strong demand for the development of energy saving devices (ESD). SSPA anticipates that the demand will be greater to respond to new requirements set by the IMO regulation on energy efficient design index (EEDI). SSPA has been involved in many joint research projects in developing energy saving solutions. Daewoo Shipbuilding and Marine Engineering Co. Ltd. (DSME) has developed several ESDs in cooperation with SSPA, where SSPA has tested most of the ESDs designed by DSME over the last 10 years. The …pre-swirl stator (PSS) is a device mounted on the stern boss just upstream of the propeller (see Fig. 6 or Fig. 33). It is designed to generate pre-swirl flow to the propeller in order to gain a favorable interaction with the propeller that improves the propulsive efficiency and results in a power reduction. This paper is a full description of one of the developments of PSS from the early design stage, optimization phase, and confirmation by model tests to validation through sea trial tests. Show more

Keywords: Hydrodynamic optimization, Energy Saving Device (ESD), Pre-swirl Stator (PSS), Computational Fluid Dynamic (CFD)

DOI: 10.3233/ISP-130092

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 233-276, 2013

Authors: Kandasamy, Manivannan | Peri, Daniele | Tahara, Yusuke | Wilson, Wesley | Miozzi, Massimo | Georgiev, Svetlozar | Milanov, Evgeni | Campana, Emilio F. | Stern, Frederick

Article Type: Research Article

Abstract: The present work focuses on the application of simulation-based design for the resistance optimization of waterjet propelled Delft catamaran, using integrated computational and experimental fluid dynamics. A variable physics/variable fidelity approach was implemented wherein the objective function was evaluated using both low fidelity potential flow solvers with a simplified CFD waterjet model and high fidelity RANS solvers with discretized duct flow calculations. Both solvers were verified and validated with data for the original hull. The particle swarm optimizer was used for single speed optimization at Fr=0.5, and genetic algorithms were used for multi speed optimization at Fr=0.3, 0.5 and 0.7. …The variable physics/variable fidelity approach was compared with high fidelity approach for the bare-hull shape optimization and it showed an overall CPU time reduction of 54% and converged to the same optimal design at Fr=0.5. The multi-speed optimization showed design improvement at Fr=0.5 and 0.7, but not at Fr=0.3 since the design variables were obtained based on sensitivity analysis at Fr=0.5. High fidelity simulation results for the optimized barehull geometry indicated 4% reduction in resistance and the optimized waterjet equipped geometry indicated 11% reduction in effective pump power required at self-propulsion. Verification was performed for the optimized hull form and its reduction in powering will be validated in forthcoming experimental campaign. Show more

Keywords: Simulation-based design, ship design, waterjet propulsion, variable fidelity

DOI: 10.3233/ISP-130098

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 277-308, 2013

Authors: Zou, L. | Larsson, L.

Article Type: Research Article

Abstract: A ship travelling in canals or narrow channels may encounter hydrodynamic forces and moments caused by a nearby side bank. Since most canals are shallow the effect of the bottom can also be considerable. Knowledge of these effects is crucial for safe navigation. The present paper introduces a study in the framework of a project applying Computational Fluid Dynamics (CFD) in the prediction of confined water effects. Using a steady state Reynolds Averaged Navier–Stokes solver, this study investigates the shallow-water and bank effects on a tanker moving straight ahead at low speed in a canal characterized by surface piercing banks. …The tanker is fitted with a rudder and a propeller at a zero propeller rate and at self-propulsion. In the systematic computations, a series of cases are considered with varying water depth and ship-to-bank distance, as well as different canal configurations. In the computations, the double model approximation is adopted to simulate the flat free surface. The non-rotating propeller is treated as an appendage composed of shaft and blades, while the operating propeller is approximated by body forces, simulated by a lifting line potential flow model. Validation of forces and moments against experimental data has been performed in previous studies. The emphasis of the present paper is placed on the effects on the flow field and the physical explanation of these effects. Show more

Keywords: Confined water effects, computational fluid dynamics, hydrodynamic forces and moments, verification and validation, flow field analysis

DOI: 10.3233/ISP-130101

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 309-343, 2013

Authors: Bark, Göran | Bensow, Rickard E.

Article Type: Research Article

Abstract: In this paper we consider development of cavitation erosion having its origin in sheet cavitation. The discussion includes generation of cloud cavitation from sheet cavitation and how a cloud collapse can be enhanced by energy cascading from the collapse of a glassy sheet cavity into the collapse of a cloud. A decomposition of the cavitation process into crucial parts results in formulation of a conceptual model for description and analysis of the generation of erosion by mixed glassy and cloud cavitation.

Keywords: Sheet and cloud cavitation, cavitation erosion

DOI: 10.3233/ISP-130097

Citation: International Shipbuilding Progress, vol. 60, no. 1-4, pp. 345-374, 2013