Scale effects and full-scale ship hydrodynamics: A review

2022 ◽  
Vol 245 ◽  
pp. 110496
Author(s):  
Momchil Terziev ◽  
Tahsin Tezdogan ◽  
Atilla Incecik
Keyword(s):  
Scale Effects ◽  
Full Scale ◽  
Ship Hydrodynamics

MODEL- AND FULL-SCALE RANS SIMULATIONS FOR A DRIFT TANKER

2021 ◽  
Vol 159 (A2) ◽  
Author(s):  
J Yao
Keyword(s):  
Eddy Viscosity ◽  
Scale Effects ◽  
Grid Point ◽  
Computational Grid ◽  
Measured Data ◽  
Full Scale ◽  
Computational Time ◽  
Wall Function ◽  
Ship Hydrodynamics ◽  
Sst Model

The flow around a full-scale (FS) ship can be simulated by means of Reynolds-Averaged Naiver-Stokes (RANS) method, which provides a way to obtain more knowledge about scale effects on ship hydrodynamics. In this work, the viscous flow around a static drift tanker in full scale is simulated by using the RANS solver based on the open source platform OpenFOAM. The k - w SST model is employed to approximate the eddy viscosity. To reduce computational time, wall function approach is applied for the FS simulation. The flow around the ship in model scale is simulated as well, but without using any wall function, i.e., using Low-Reynolds number mode. In order to verify the computations, de- tailed studies on the computational grid including investigation of the sensitivity of computed forces to y+ (dimension- less distance of first grid point to wall) and grid dependency study are carried out. The computed forces are compared with available measured data. The scale effects are analysed and discussed by comparisons.

A Comparison of Several Strategies to Optimize a Ship’s Aft Body

2011 ◽  
Vol 27 (04) ◽  
pp. 202-211
Author(s):  
Auke van der Ploeg
Keyword(s):  
Viscous Flow ◽  
Scale Effects ◽  
Full Scale ◽  
Ship Hull ◽  
Hull Form ◽  
Wake Field ◽  
Hull Forms ◽  
Definition Of

This paper describes a procedure to optimize ship hull forms, based on double body viscous flow computations with PARNASSOS. A flexible and effective definition of parametric hull form variations is used, based on interpolation between basis hull forms. One of the object functions is an estimate of the required power. In this paper we will focus on how to improve this estimate, by using the B-series of propellers. Results of systematic variations applied to the VIRTUE tanker together with scale effects in the computed trends will be discussed. In addition, we will demonstrate how the techniques discussed in this paper can be used to design a model that has a wake field that strongly resembles the wake of a given containership ship at full scale.

Grid requirements for LES of ship hydrodynamics in model and full scale

2017 ◽  
Vol 143 ◽  
pp. 259-268 ◽  
Author(s):  
Mattias Liefvendahl ◽  
Christer Fureby
Keyword(s):  
Full Scale ◽  
Ship Hydrodynamics

Model-Scale and Full-Scale CFD Calculations for Current Loads on Semi-Submersible

2011 ◽  
Author(s):  
Arjen Koop ◽  
Alexei Bereznitski
Keyword(s):  
Wind Tunnel ◽  
Scale Effects ◽  
Full Scale ◽  
Grid Resolution ◽  
Wind Tunnel Experiments ◽  
Force Coefficients ◽  
Model Scale ◽  
Coarse Grids

In this paper results of CFD calculations with the MARIN in-house code ReFRESCO are presented for the JBF-14000 Semi-Submersible designed by Huisman Equipment BV. The objective of the CFD calculations is to investigate the applicability, the costs and the accuracy of CFD to obtain the current coefficients of a semi-submersible for all headings. Furthermore, full scale CFD calculations are carried out to investigate possible scale effects on the current coefficients. An extensive verification study has been carried for the model-scale current loads on a semi-submersible using 10 different grids of different grid type for 3 different headings, i.e. 180, 150 and 90 degrees. These headings represent the main different flow regions around the semi-submersible. The CFD results are compared with the results from wind tunnel experiments and tests in the Offshore Basin for a range of current headings. The results for the force coefficients are not very dependent on grid resolution and grid type. The largest differences found are less than 10% and these are obtained for CX results for 180 degrees. For the results obtained on the same grid type the results change less than 4% when the grid is refined. These verification results give good confidence in the CFD results. For the angles with larger forces, i.e. the range [180:130] for CX and the range [150:90] for CY the CFD results are within 12% or better from the experiments. Full-scale force coefficients are calculated using 5 subsequently refined grids for three different headings, i.e. 180, 150 and 90 degrees. Scale effects should only be determined when the effect of grid refining is investigated. The trend of the force coefficients when refining the grid, can be different for model-scale and full-scale. The use of coarse grids can lead to misleading conclusions. On average the full-scale values are approximately 15–20% lower than for model-scale. However, larger differences for a number of angles do exist.

Experimental Study of Containment Boom Behavior in Waves

1997 ◽  
Vol 34 (01) ◽  
pp. 24-30
Author(s):  
Michael S. Bruno ◽  
Robert L. Van Dyck
Keyword(s):  
Scale Effects ◽  
Weight Ratio ◽  
Breaking Waves ◽  
Full Scale ◽  
Irregular Waves ◽  
Generic Model ◽  
Open Sea ◽  
Scale Breaking ◽  
Heave Motion ◽  
Testing Instruments

An effort to assess containment boom performance in waves is described. New model testing instruments and procedures have been developed to provide a direct measure of boom heave response to wave excitation at several points along the boom. Measurements have been made in reproducible regular, irregular and breaking waves for various generic model boom configurations over a range of wave characteristics, boom buoyancy/weight ratios, and towing speeds. A model scale of 1/8 allows for tests in regular waves up to 12 ft high full scale at 12:1 length/height ratio and irregular waves with significant heights of up to 8 ft full scale. Breaking waves equivalent to over 6 ft height above mean water level are also generated. Measurements include total towing force and heave motion at four locations along each boom. The results of tests of three different size models all scaled to the same 4 ft high prototype boom show no significant scale effects on heave response to the various types of waves. Drag differences found among the models are attributable to differences in full scale lengths, as well as buoyancy/weight ratios. A buoyancy/weight ratio of 10 or greater was found to improve heave conformance with waves at optimum towing speeds of about 0.5 knot. Short wavelength waves, requiring the highest frequency response, are shown to be the most difficult conformance problem. Of particular concern is the fact that a catenary tow shape focuses waves near the vertex, thereby amplifying the wave height and causing excessive motions near the center of the boom. For this reason, light weight, highly flexible booms with maximum buoyancy/weight ratio and sufficient freeboard are recommended for open sea operations.

A Hybrid Empirical-Numerical Method for Hydroelastic Analysis of a Floater-and-Net System

2016 ◽  
Vol 60 (01) ◽  
pp. 14-29 ◽  
Author(s):  
Leixin Ma ◽  
Ke Hu ◽  
Shixiao Fu ◽  
Torgeir Moan ◽  
Runpei Li
Keyword(s):  
Hybrid Method ◽  
Hydrodynamic Force ◽  
Scale Effects ◽  
Fish Farming ◽  
Full Scale ◽  
Hydrodynamic Models ◽  
Load Models ◽  
Hydroelastic Analysis ◽  
Net Cages ◽  
Hydroelastic Response

Because of scale effects and inappropriate hydrodynamic models, the nonlinear hydroelastic response of net cages used for fish-farming cannot be analyzed precisely with traditional model testing or combinations of finite element methods (FEMs) and load models. In this study, an innovative hybrid method is proposed to determine the hydroelastic response of full-scale floater-and-net systems more accurately. In this method, the net for the fish cage was vertically and peripherally divided into similar interconnected sections with different hydrodynamic parameters, which were assumed to be uniformly distributed over each section. A model of a typical section was subjected to various towing velocities, oscillation periods, and amplitudes in a towing tank to simulate the potential motions of all sections in the net under various currents, waves, and floater movements. By analyzing the measured hydrodynamic force from this test section, a hydrodynamic force database for a typical net section under various currents, waves, and floater motions was built. Finally, based on an FEM, the modified Morison equation and the hydrodynamic force database, the hydroelastic behavior of the full-scale fish cage was calculated with an iterative scheme. It is demonstrated that this hybrid method is able to produce correct hydroelastic response for both steady and oscillatory flows. The hydroelastic response of a two-dimensional example of a full-length net panel with steady currents and floater oscillations was studied in detail.

A study on the influence of hull wake on model scale cavitation and noise tests for a fast twin screw vessel with inclined shaft

2017 ◽  
Vol 232 (3) ◽  
pp. 307-330
Author(s):  
Giorgio Tani ◽  
Michele Viviani ◽  
Diego Villa ◽  
Marco Ferrando
Keyword(s):  
Scale Effects ◽  
Full Scale ◽  
Ship Wake ◽  
Radiated Noise ◽  
Wake Field ◽  
Model Scale ◽  
Propeller Noise ◽  
Twin Screw ◽  
Long Time ◽  
The Impact

The study of ship underwater radiated noise is nowadays a topic of great and largely recognized importance. This is due to the fact that in the last decades, the problem of the impact of anthropogenic noise on marine life has been addressed with higher emphasis, giving rise to different efforts aimed to the analysis of its effects on different organisms and, in parallel, to means for the reduction of shipping noise. In this context, attention is focused on the propeller noise, which, in cavitating conditions, may represent the most important noise source of the ship. The propeller noise has been studied for long time with different approaches. One of the most effective approaches is represented by model scale testing in cavitation tunnels or similar facilities. Despite having been adopted for several years, radiated noise experiments in model scale are usually affected by significant scale effects and technical issues. One of these aspects is represented by the correct modelling of the propeller inflow; different techniques are adopted, depending on the facility, in order to reproduce a certain target wake. One of the main problems is to define this target wake, which should in principle coincide with the ship wake; as it is well known, it is usually derived from model scale towing tank measurements, with the necessity for the prediction of the full-scale wake field. Starting from the outcomes of a previous work on the influence of different approaches for the prediction of the full-scale wake field for a single screw ship, in this work, attention is focused on the case of a fast twin screw vessel, analysing the different issues which may be connected to this hull form.

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