Step Forward for CFD Uncertainty Analysis of Ship Resistance Benchmark Model LHI-007 (original) (raw)
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An uncertainty analysis is performed with the open source CFD toolkit, OpenFOAM, for four different ship models, KCS, DTC, KVLCC2, and JBC. A brief review of the practices in uncertainty analysis in the field of ship CFD is presented. Uncertainty analysis is performed for their resistance, sinkage and trim results using the two most popular uncertainty analysis methods. The study revealed that the two methods differ significantly from each other in total uncertainty prediction, and confirms that both validation and verification studies are case specific.
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The present study describes the viscous flow simula tion of the bare hull ship resistance of the DTMB 5415 model ship. The study includes comput ations for ship resistance as well as free-surface and sinkage and trim prediction for three different Froude numbers. Computations are performed using the ISIS-CFD solver in cluded in Fine/Marine software available under the NUMECA suite where the discretizat ion in space is based on finite volume method using unstructured grid. The Reynolds Average Navier-Stokes equations are numerically solved in a quasi-static approach wh ere the turbulence is modeled by making use of the kω SST model. Four different computational grids were generated for performing a verification and validation study base d on Richardson extrapolation method. Results are compared with the benchmark experime ntal data provided in the Gothenburg workshop on CFD in ship hydrodynamics in 2010. V alidation of the numerical results shows a reasonable agreement with the exper...
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IOP Conference Series: Materials Science and Engineering, 2019
Considering the extensive use of numerical methods in naval design, a question about the accuracy numerical tools that could estimate the flow around the ship and which are the limitations of these tools for practical design applications. In this context, experimental test on scaled models play an important role in validation of numerical simulations. This work is dedicated to validation of the method used to calculate the non-linear potential free-surface flow around the ship. Global quantities, as total resistance, wave resistance coefficient, residual resistance coefficient are flow characteristics concentrated in a single value, and their validation provides a criterion for choosing the optimum hull. Validation of physical phenomena is done using the wave profile, the pressure distribution on the body or the free surface topology. Validations were developed by comparing experimental data published for benchmark test cases, results of the resistance test performed in ICEPRONAV to...
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Recently, there have been active efforts to investigate the effect of hull roughness on ship resistance using Computational Fluid Dynamics (CFD). Although, several studies demonstrated that the roughness modelling in the CFD simulations can precisely predict the increase in frictional resistance due to the surface roughness, the experimental validations have been made only for flat plates which have zero pressure gradient. This means that the validations cannot necessarily guarantee the validity of this method for other ship resistance components besides the frictional resistance. Therefore, it is worth to demonstrate the validity of the roughness modelling in CFD on the total resistance of a 3D hull. In this study, CFD models of a towed flat plate and a KRISO Container Ship (KCS) model were developed. In order to simulate the roughness effect in the turbulent boundary layer, a previously determined roughness function of a sand-grain surface was employed in the wall-function of the CFD model. Then the result of the CFD simulations was compared with the experimental data. The result showed a good agreement suggesting that the CFD approach can precisely predict the roughness effect on the total resistance of the 3D hull. Finally, the roughness effects on the individual ship resistance components were investigated.
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Added resistance of ships in waves is one of increasingly important problems in naval engineering due to energy efficiency regulations. In this work, validation of the Naval Hydro pack in OpenFOAM is performed by conducting simulations of a KRISO container ship (KCS) in calm water and head waves. Steady resistance and dynamic sinkage and trim at different Froude numbers are compared to experimental data. Mesh refinement study has been carried out for design Froude number in order to asses numerical uncertainty. Seakeeping simulations of the ship in head waves are carried out for a number of different wave parameters at design Froude number. Added resistance is compared with experimental results. All simulations are performed with fully non–linear, turbulent, two–phase CFD solver. Wave modelling is performed using Spectral Wave Explicit Navier–Stokes Equations (SWENSE) [1] with implicit relaxation zones [5] that are used to prevent wave reflection. In addition to the validation runs,...
Numerical Investigating the Effect of Water Depth on Ship Resistance Using RANS CFD Method
Polish Maritime Research, 2019
On inland waterways the ship resistance and propulsive characteristics are strictly related to the depth of the waterway, thus it is important to have an understanding of the influence of water depth on ship hydrodynamic characteristics. Therefore, accurate predictions of hydrodynamic forces in restricted waterways are required and important. The aim of this paper is investigating the capability of the commercial unsteady Reynolds–Averaged Navier–Stokes (RANS) solver to predict the influence of water depth on ship resistance. The volume of fluid method (VOF) is applied to simulate the free surface flow around the ship. The hull resistance in shallow and deep water is compared. The obtained numerical results are validated against related experimental studies available in the literature.
Computational and experimental works on ship resistance
IOP Conference Series: Earth and Environmental Science, 2019
Ship engine power is estimated at initial design process to satisfy the required speed. This ship parameter is determined by computation of ship resistance and propulsion parameter from any existing methods or executing ship model test. In fact, the results of ship model tests do not satisfy those of the existing methods. However, for initial design approach this may be used to estimate the engine power. This approach is used in design process for many ships but some methods are not suitable for certain type of ships. Three type of ships were developed and evaluated to prove this issue. They were fishing ship, passenger-cargo coaster and semi-displacement ship. The resistance and propulsion parameters of those ships were determined by the existing methods. Three models of those ships were tested in the towing tank to validate the results of the resistance from existing methods. The results of computation and model test were presented and analyzed. It was found that there were differ...
Brodogradnja
RANS-CFD is a well-established tool with widespread use in maritime industry and research. Valuable information might be extracted from the results of such simulations in terms of ship resistance and flow field variables. With recent advancements in computational power, it became possible to investigate the performance of ships in self-propulsion conditions with RANS method. This paper presents the results of a study in which self-propulsion analyses of a small size product/oil tanker has been carried out at ship scale. The methodology proposed in this study makes use of open water propeller performance predictions, resistance analyses at model scale and self-propulsion computations at ship scale for a minimum of 2 different propeller loadings to obtain the self-propulsion point and respective performance parameters. In order to speed up the time-consuming self-propulsion computations, these cases have been solved with a single-phase approach. Resistance predictions have been compar...