Screws Working in Behind and Prediction of the Performance of Full Ships

1990 ◽  
Vol 34 (04) ◽  
pp. 262-282
Author(s):  
Christopher Grigson
Keyword(s):  
Velocity Field ◽  
Scale Effect ◽  
Open Water ◽  
Full Scale ◽  
Constant Speed ◽  
Water Characteristics ◽  
Torque Coefficient ◽  
Ship Propeller

Constant speed propulsion tests of full models are investigated. The propulsion factors are found to vary with propeller speed, n. When the tests extend to idling conditions, the nominal wake fraction and the complete propeller-hull behind characteristics ϕ(u/nd) are determined. Fifteen designs of hull and screw are investigated. In some, the coupling between the velocity field of the hull and that of the screw is found to be strong. The behind characteristics depend both on the design of the screw and on the design of the hull. The same design of screw may efficiently power hulls of quite different form. A second kind of behind characteristic, ψ[(1 -ω)u/nd], is introduced. It is obtained from ϕ and it can be compared directly with the open-water characteristics. It is shown experimentally that in a full ship the open-water characteristics are not generally an accurate substitute for the behind ones. Therefore ϕ or ψ ought to be used when predicting ship propeller speed Ν and power. A condition for running the propulsion test is derived in which, after correction for the scale effect of blade friction on torque, the full-scale behind torque coefficient may be found from the model one. Furthermore, in this test condition Ν may be rigorously scaled from n, measured on the model. Thus full-scale performance is determined. Limited tests of the method appear accurate.

An Investigation Into the Effect of Biofouling on Full-Scale Propeller Performance Using CFD

2019 ◽  
Author(s):  
Soonseok Song ◽  
Yigit Kemal Demirel ◽  
Mehmet Atlar
Keyword(s):  
Open Water ◽  
Full Scale ◽  
Roughness Effect ◽  
Thrust Coefficient ◽  
Propulsion Performance ◽  
Negative Effect ◽  
Precise Prediction ◽  
Torque Coefficient ◽  
Open Water Performance ◽  
Propeller Performance

Abstract The negative effect of biofouling on ship resistance has been investigated since the early days of naval architecture. However, for more precise prediction of fuel consumption of ships, understanding the effect of biofouling on ship propulsion performance is also important. In this study, CFD simulations for the full-scale performance of KP505 propeller in open water, including the presence of marine biofouling, were conducted. To predict the effect of barnacle fouling on the propeller performance, experimentally obtained roughness functions of barnacle fouling were employed in the wall-function of the CFD software. The roughness effect of barnacles of varying sizes and coverages on the propeller open water performance was predicted for advance coefficients ranging from 0.2 to 0.8. From the simulations, drastic effects of barnacle fouling on the propeller open water performance were found. The result suggests that the thrust coefficient decreases while the torque coefficient increases with increasing level of surface fouling, which leads to a reduction of the open water efficiency of the propeller. Further investigations into the roughness effect on the pressure and velocity field, surface pressure and wall shear stress, and propeller vortices were examined.

SPH Simulations of Ship Propeller Induced Harbour Bed Erosion

2012 ◽  
Author(s):  
Christian Ulrich ◽  
Thomas Rung
Keyword(s):  
Open Water ◽  
Local Flow ◽  
Stress Criterion ◽  
Counter Measures ◽  
Water Characteristics ◽  
Bed Erosion ◽  
Particle Hydrodynamics ◽  
Suspension Layer ◽  
Smoothed Particle ◽  
Ship Propeller

The paper reports on the predictive prospects of Smoothed-Particle-Hydrodynamics (SPH) for simulations of ship propeller induced scours in harbours. Such erosions represent unpleasant phenomena, especially if they occur close to quay walls, and generate cost intensive counter measures. These measures are usually based on a rather weak background knowledge. SPH simulations can help to analyse the erosional processes and to understand the interaction between ship, water, soil and structure. In the present research, a body-force propulsor model based on the open water characteristics is used to represent the ship’s propeller. The evolution of the liquid and granular phase particles is obtained from an SPH-integration of the continuity and momentum equations. The fluid is considered to be Newtonian and the viscosity of the soil-phase is modelled in line with the Mohr-Coulomb yield stress criterion. Water and soil particles interacting in a suspension layer are assigned to a viscosity that is derived from a Chézy-relation between the shear stress and the local flow velocity. A variable particle resolution strategy is applied to handle large domains, in which the areas around the ship hull demand a fine resolution. A complex full-scale application example included refers to the starting sequence of a container ship propeller.

scholarly journals Numerical Simulations Of Hydrodynamic Open-Water Characteristics Of A Ship Propeller

2016 ◽  
Vol 23 (4) ◽  
pp. 16-22 ◽  
Author(s):  
Judyta Felicjancik ◽  
Sebastian Kowalczyk ◽  
Karol Felicjancik ◽  
Krzysztof Kawecki
Keyword(s):  
Numerical Methods ◽  
Numerical Simulations ◽  
Experimental Research ◽  
Open Water ◽  
Research Centre ◽  
Model Data ◽  
Kinematic Data ◽  
Water Characteristics ◽  
Ship Propeller ◽  
Real Scale

Abstract The paper presents the results of numerical simulations of ship propeller operation bearing the name of Propeller Open Water (POW) Tests. The object of tests was a sample ship propeller (PPTC1), the geometrical and kinematic data of which are available, along with the results of model tests, on the official page of the research centre involved in the measurements. The research aimed at verifying the correctness of results of numerical simulations performed in the model and real scale. The results of numerical analyses performed in the model scale were confronted with those measured in the experiment. Then, making use of dimensionless coefficients which characterise propeller’s operation, the recorded model data were extrapolated to real conditions and compared with corresponding results of simulations. Both the numerical simulations and the experimental research were performed for the same propeller load states. The reported research is in line with other activities which aim at developing advanced numerical methods to support the process of ship propeller designing.

scholarly journals CFD Simulation for Estimating Efficiency of PBCF Installed on a 176K Bulk Carrier under Both POW and Self-Propulsion Conditions

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1192
Author(s):  
Dong-Hyun Kim ◽  
Jong-Chun Park ◽  
Gyu-Mok Jeon ◽  
Myung-Soo Shin
Keyword(s):  
Cfd Simulation ◽  
Open Water ◽  
Navier Stokes ◽  
Water Efficiency ◽  
Ocean Engineering ◽  
Bulk Carrier ◽  
Incompressible Viscous Flow ◽  
Korea Research Institute ◽  
Torque Coefficient ◽  
Viscous Flow Field

In this paper, the efficiency of Propeller Boss Cap Fins (PBCF) installed at the bulk carrier was estimated under both Propeller Open Water (POW) and self-propulsion conditions. For this estimation, virtual model-basin tests (resistance, POW, and self-propulsion tests) were conducted through Computational Fluid Dynamics (CFDs) simulation. In the resistance test, the total resistance and the wake distribution according to ship speed were investigated. In the POW test, changes of thrust, torque coefficient, and open water efficiency on the propeller according to PBCF installation were investigated. Finally, the International Towing Tank Conference (ITTC) 1978 method was used to predict the effect of PBCF installation on self-propulsive coefficient and brake horsepower. For analyzing incompressible viscous flow field, the Reynolds-Averaged Navier–Stokes (RANS) equation with SST k-ω turbulence model was calculated using Star-CCM+ 11.06.010-R8. All simulation results were validated by comparing the results of model tests conducted at the Korea Research Institute of Ships and Ocean Engineering (KRISO). Consequently, for the self-propulsion test with the PBCF, a 1.5% reduction of brake horsepower was estimated in the simulation and a 0.5% reduction of the brake horsepower was estimated in the experiment.

scholarly journals A study into the scale effect on the strength properties of polymer composite materials

2019 ◽  
Vol 5 (2) ◽  
pp. 103-108
Author(s):  
Valentina V. Kiryushina ◽  
Yuliya Yu. Kovaleva ◽  
Petr A. Stepanov ◽  
Pavel V. Kovalenko
Keyword(s):  
Composite Materials ◽  
Polymer Composite ◽  
Scale Effect ◽  
Mechanical Characteristics ◽  
Full Scale ◽  
Sample Thickness ◽  
Polymer Composite Materials ◽  
Test Machine ◽  
Test Results ◽  
Laboratory Sample

Polymer composite materials (PCM) are used extensively and are viewed as candidates for application in various industries, including nuclear power. Despite a variety of methods and procedures employed to investigate the mechanical characteristics of PCMs, the use of the laboratory sample mechanical test results to design and model large-sized structures is not always fully correct and reasonable. In particular, one of the problems is concerned with taking into account the scale parameter effects on the PCM strength and elastic characteristics immediately in the product. The purpose of the study is to investigate the scale effects on the mechanical characteristics of glass reinforced plastics using phenolformaldehyde and silicon-organic binders and a fabric quartz filler. Samples of four different standard sizes under GOST 25604-82 and GOST 4648-2014 were tested for three-point bending using an LFM-100 test machine to estimate the scale effect. The thicknesses of the model samples were chosen with regard for the wall thicknesses of full-scale products under development or manufactured commercially and the test machine features, and varied in the limits of 1.6 to 7.5 mm. The tests showed that strength decreased as the sample thickness was increased to 3 mm and more both at room and elevated (200 to 500 °C) temperatures, which can be described by an exponential function based on the Weibull statistical model. The values of the Weibull modulus that characterizes the extent of the scale effect on the strength of the tested materials were 4.6 to 6.7. The average bend strength in the sample thickness range of 3 mm and less does not vary notably or tends to increase slightly as the thickness is increased. This fact makes it possible to conclude that estimation of allowable stresses in a thin-wall product requires the use of test results for samples with a thickness that is equal to the product wall thickness since standard samples may yield overestimated allowable stress values and lead, accordingly, to incorrect calculations of the strength factor. The results obtained shall be taken into account when defining the allowable levels of operation for full-scale products and structures of polymer composites based on the laboratory sample strength data as well as when estimating their robustness as a characteristic of the product’s fail-safe operation.

Estimation of Fluctuating Propeller Torque of Full-Scale Ship Using Free-Running Model in Waves

2015 ◽  
Author(s):  
Michio Ueno ◽  
Yoshiaki Tsukada
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Full Scale ◽  
Engine Torque ◽  
Engine Model ◽  
Frequency Components ◽  
Free Running ◽  
External Forces ◽  
Ship Propeller ◽  
Ship Speed

The authors propose a method to estimate full-scale propeller torque consisting of low-frequency and high-frequency components in waves using measured data of free-running model ship. The duct fan auxiliary thruster (DFAT) [1] and the rudder-effectiveness and speed correction (RSC) [2,3] ensure similar model ship motion to full-scale in external forces, where RSC controls the model ship propeller rate of revolution and the auxiliary thrust depending on measured model ship speed. Analyzing a fluctuating component of effective inflow velocity to propeller due to waves, the method estimates full-scale fluctuating propeller torque in waves. This method also makes it possible to adopt into free-running model ship tests any engine model simulating interaction between propeller torque and engine torque. Trial application of the method exemplifies the property of full-scale fluctuating propeller torque comparing with that of model ship.

Oil Skimming Efficiency of the SOS: Scaling From GeoSim Model Tests to Full Scale Prototype Operations

2012 ◽  
Author(s):  
Günther F. Clauss ◽  
Sascha Kosleck ◽  
Florian Sprenger ◽  
Laura Grüter
Keyword(s):  
Flow Pattern ◽  
Oil Recovery ◽  
Open Water ◽  
Model Tests ◽  
Full Scale ◽  
Polluted Water ◽  
Water Separation ◽  
Weathering Processes ◽  
River Elbe ◽  
Hydrodynamic Effects

The severe ecological and economical aftermath of the 2010 ‘Deepwater Horizon’ catastrophe in the Gulf of Mexico clearly shows the insufficiency of current oil recovery systems which cannot operate in wave heights above 1.5m. To prevent emulsification and weathering processes, it is necessary to skim the oil film off the sea surface shortly after the accident. The autonomous SOS (Sea State-independent Oil Skimming System) developed within the framework of the research project SOS3 features high transit velocities, the capability of operating in rough seas and a massive intake of oil polluted water — and is therefore a unique technology. The oil water separation process of the SOS is purely based on hydrodynamic principles involving vortex evolution and a special flow pattern inside the internal moon pool. These requirements for efficient oil skimming operations depend on various hydrodynamic effects that would imply model testing in compliance with Froude’s and Reynolds’ law simultaneously — a physically impossible condition. Therefore GeoSim model tests with the SOS at model scales of 1:16, 1:25 and 1:36 are conducted with discrete particles of the correct density substituting the oil phase. The tendencies in flow pattern evolution and oil skimming efficiency are compared and extrapolated to full scale. Results from open water tests with the prototype of the SOS in the mouth of river Elbe serve for validation of the extrapolated results.

Benchmark Case Study of Scale Effect in Self-Propelled Container Ship Squat

2020 ◽  
Author(s):  
Zhen Kok ◽  
Jonathan Duffy ◽  
Shuhong Chai ◽  
Yuting Jin
Keyword(s):  
Scale Effect ◽  
Body Force ◽  
Full Scale ◽  
The Body ◽  
Water Model ◽  
Container Ship ◽  
Confined Water ◽  
Cfd Model ◽  
Empirical Prediction ◽  
Model Scale

Abstract A URANS CFD-based study has been undertaken to investigate scale effect in container ship squat. Initially, CFD studies were carried out for the model scale benchmarking squat cases of a self-propelled DTC container ship. In this study, a quasi-static modelling approach was adopted where the hull was fixed from sinking and trimming which is computationally more efficient than dynamic mesh methods that models actual motion directly. Instead, the quasi-static approach allows estimation of the squat base on the recorded hydrodynamic forces and moments. Propulsion of the vessel was modelled by the body-force actuator disc method. Upon successful verification and validation of the model scale self-propelled CFD model against benchmark data, full scale investigations were then undertaken. Validation of the full scale set-up was demonstrated by computing the full scale bare hull resistance in deep, laterally unrestricted water and comparing against the extrapolated resistance of model scale benchmark resistance data. Upon validating the setup, it was used to predict full scale ship squat in confined waters. The credibility of the full scale confined water model was checked by comparing vessel resistance in confined water against the Landweber empirical prediction. To quantify scale effect in ship squat predicitons, the benchmarking squat cases were computed by adopting the validated full scale CFD model with body-force propulsion. Comparison between the full scale CFD, model scale CFD and model scale benchmark EFD squat results demonstrates that scale effect is negligible.

Leaching Scale Effect for Cement-Waste Forms

1988 ◽  
Vol 127 ◽  
Author(s):  
J. C. Nomine ◽  
A. Billon ◽  
G. Courtois
Keyword(s):  
Scale Effect ◽  
Practical Method ◽  
Full Scale ◽  
Time Limit ◽  
Waste Form ◽  
Leaching Tests ◽  
Local Policy ◽  
Waste Package ◽  
Waste Forms

The confinement ability of a waste package is one of the major safety characteristics to consider in shallow land burial. In order to determine if the confinement is acceptable, in accordance with local policy, one way is to proceed to leaching tests. The practical method, for sake of simplicity, cost and time limit, is to carry out the leaching tests on laboratory samples which are easier to prepare than full-scale blocks, but the representativity of which needs to be treated with caution; it is in this context, that one of the aspect of our work concerns what is known as the “scale effect”.This study has been conducted using blocks the volumes of which are respectively of 200, 20, 2 and 0, 2 1, and made with the same cement-waste form (13 Cs) system.

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