NON-DIMENSIONALISATION OF LATERAL DISTANCES BETWEEN VESSELS OF DISSIMILAR SIZES FOR INTERACTION EFFECT STUDIES

2021 ◽  
Vol 159 (A4) ◽  
Author(s):  
N Jayarathne ◽  
D Ranmuthugala ◽  
Z Leong ◽  
J Fei
Keyword(s):  
Interaction Effect ◽  
Hydrodynamic Interaction ◽  
Interaction Effects ◽  
Full Scale ◽  
Correlation Technique ◽  
Effect Data ◽  
Scale Interaction ◽  
Model Scale ◽  
Interaction Studies ◽  
Lateral Distance

To date, most of the hydrodynamic interaction studies between a tug and a ship during ship assist manoeuvers have been carried out using model scale investigations. It is however difficult to establish how well results from these studies represent full scale interaction behaviour. This is further exacerbated by the lack of proven methodologies to non- dimensionalise the relative distances between the two vessels, enabling the comparison of model and full scale interaction effect data, as well as between vessels of dissimilar size ratios. This study investigates a suitable correlation technique to non-dimensionalise the lateral distance between vessels of dissimilar sizes, and a scaling option for interaction effect studies. It focuses on the interaction effects on a tug operating around the forward shoulder of a tanker at different lateral distances during ship assist operations. The findings and the non-dimensioning method presented in this paper enable the interaction effects determined for a given ship-to-tug ratio to be used to predict the safe operational distances for other ship-to-tug ratios.

Non-Dimensionalisation of Lateral Distances Between Vessels of Dissimilar Sizes for Interaction Effect Studies

2017 ◽  
Vol 159 (A4) ◽  
Author(s):  
N Jayarathne ◽  
D Ranmuthugala ◽  
Z Leong ◽  
J Fei
Keyword(s):  
Interaction Effect ◽  
Hydrodynamic Interaction ◽  
Interaction Effects ◽  
Full Scale ◽  
Correlation Technique ◽  
Effect Data ◽  
Scale Interaction ◽  
Model Scale ◽  
Interaction Studies ◽  
Lateral Distance

To date, most of the hydrodynamic interaction studies between a tug and a ship during ship assist manoeuvers have been carried out using model scale investigations. It is however difficult to establish how well results from these studies represent full scale interaction behaviour. This is further exacerbated by the lack of proven methodologies to non-dimensionalise the relative distances between the two vessels, enabling the comparison of model and full scale interaction effect data, as well as between vessels of dissimilar size ratios. This study investigates a suitable correlation technique to non-dimensionalise the lateral distance between vessels of dissimilar sizes, and a scaling option for interaction effect studies. It focuses on the interaction effects on a tug operating around the forward shoulder of a tanker at different lateral distances during ship assist operations. The findings and the non-dimensioning method presented in this paper enable the interaction effects determined for a given ship-to-tug ratio to be used to predict the safe operational distances for other ship-to-tug ratios.

Calculation of the Hydrodynamic Interaction Between Two Encountering Bodies in Coupling Multi-Freedom Motions

2015 ◽  
Vol 157 (A4) ◽  
pp. 219-226
Keyword(s):  
Hydrodynamic Interaction ◽  
Interaction Effects ◽  
Numerical Results ◽  
Motion Equations ◽  
Flow Equations ◽  
Close Proximity ◽  
Lateral Distance ◽  
Body Sizes ◽  
Two Bodies ◽  
Good Agreement

"The sway and yaw motion will be induced additionally due to the interaction effects when two encountering bodies sail in close proximity, which may lead to the collision accident. In the present study, two ellipsoids are taken as an example. By coupling the motion equations of the two bodies and the fluid flow equations, the interaction forces and moments are calculated, and the tracks are predicted. The numerical results for the model fixed motion (only free to surge) at constant speed are compared with those published in literature for the validation of the method proposed in this paper, and good agreement is found. On this basis, more complicated multi-degree of freedom motions in surge, sway and yaw directions induced by the interaction effects are simulated. By systematically comparing and analyzing the numerical results obtained at different speeds, lateral distances and body sizes, the influences of speed and lateral distance and body size on the hydrodynamic forces are elucidated."

CALCULATION OF THE HYDRODYNAMIC INTERACTION BETWEEN TWO ENCOUNTERING BODIES IN COUPLING MULTI-FREEDOM MOTIONS

2021 ◽  
Vol 157 (A4) ◽  
Author(s):  
H M WANG ◽  
L WANG ◽  
L Q TU ◽  
C H ZHAO
Keyword(s):  
Hydrodynamic Interaction ◽  
Interaction Effects ◽  
Numerical Results ◽  
Motion Equations ◽  
Flow Equations ◽  
Close Proximity ◽  
Lateral Distance ◽  
Body Sizes ◽  
Two Bodies ◽  
Good Agreement

ellipsoids are taken as an example. By coupling the motion equations of the two bodies and the fluid flow equations, the interaction forces and moments are calculated, and the tracks are predicted. The numerical results for the model fixed motion (only free to surge) at constant speed are compared with those published in literature for the validation of the method proposed in this paper, and good agreement is found. On this basis, more complicated multi-degree of freedom motions in surge, sway and yaw directions induced by the interaction effects are simulated. By systematically comparing and analyzing the numerical results obtained at different speeds, lateral distances and body sizes, the influences of speed and lateral distance and body size The sway and yaw motion will be induced additionally due to the interaction effects when two encountering bodies sail in close proximity, which may lead to the collision accident. In the present study, two on the hydrodynamic forces are elucidated. 

A New Method of Modeling Underexpanded Exhaust Plumes for Wind Tunnel Aerodynamic Testing

1989 ◽  
Vol 111 (4) ◽  
pp. 748-754
Author(s):  
V. Salemann ◽  
J. M. Williams
Keyword(s):  
Wind Tunnel ◽  
Free Stream ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Area Ratio ◽  
Full Scale ◽  
New Method ◽  
Thrust Coefficient ◽  
Model Scale ◽  
Exhaust Plumes

A new method for modeling hot underexpanded exhaust plumes with cold model scale plumes in aerodynamic wind tunnel testing has been developed. The method is applicable to aeropropulsion testing where significant interaction between the exhaust and the free stream and aftbody may be present. The technique scales the model and nozzle external geometry, including the nozzle exit area, matches the model jet to free-stream dynamic pressure ratio to full-scale jet to free-stream dynamic pressure ratio, and matches the model thrust coefficient to full-scale thrust coefficient. The technique does not require scaling of the internal nozzle geometry. A generalized method of characteristic computer code was used to predict the plume shapes of a hot (γ = 1.2) half-scale nozzle of area ratio 3.2 and of a cold (γ = 1.4) model scale nozzle of area ratio 1.3, whose pressure ratio and area ratio were selected to satisfy the above criteria and other testing requirements. The plume shapes showed good agreement. Code validity was checked by comparing code results for cold air exhausting into a quiescent atmosphere to pilot surveys and shadowgraphs of model nozzle plumes taken in a static facility.

Development of a Scaled Rotor Blade for Tank Tests of Floating Wind Turbine Systems

2018 ◽  
Author(s):  
Paul Schünemann ◽  
Timo Zwisele ◽  
Frank Adam ◽  
Uwe Ritschel
Keyword(s):  
Wind Turbine ◽  
Rotor Blade ◽  
Turbine Rotor ◽  
Full Scale ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Model Scale ◽  
Floating Wind Turbine ◽  
Hydrodynamic Effects ◽  
Wind Turbine Rotor

Floating wind turbine systems will play an important role for a sustainable energy supply in the future. The dynamic behavior of such systems is governed by strong couplings of aerodynamic, structural mechanic and hydrodynamic effects. To examine these effects scaled tank tests are an inevitable part of the design process of floating wind turbine systems. Normally Froude scaling is used in tank tests. However, using Froude scaling also for the wind turbine rotor will lead to wrong aerodynamic loads compared to the full-scale turbine. Therefore the paper provides a detailed description of designing a modified scaled rotor blade mitigating this problem. Thereby a focus is set on preserving the tip speed ratio of the full scale turbine, keeping the thrust force behavior of the full scale rotor also in model scale and additionally maintaining the power coefficient between full scale and model scale. This is achieved by completely redesigning the original blade using a different airfoil. All steps of this redesign process are explained using the example of the generic DOWEC 6MW wind turbine. Calculations of aerodynamic coefficients are done with the software tools XFoil and AirfoilPrep and the resulting thrust and power coefficients are obtained by running several simulations with the software AeroDyn.

A Three-Dimensional Time-Dependent Icing Model for a Stern Trawler

1998 ◽  
Vol 42 (04) ◽  
pp. 266-273
Author(s):  
K. K. Chung ◽  
E. P. Lozowski
Keyword(s):  
Three Dimensional ◽  
Grid Cell ◽  
Full Scale ◽  
Time Dependent ◽  
Trajectory Modeling ◽  
Model Scale ◽  
Droplet Trajectory ◽  
Dangerous Condition

A full-scale spray flux equation has been derived for ship-generated spray using spraying data obtained from model-scale experiments. Using this equation, droplet trajectory modeling, and spray mass continuity, a full-scale spraying model, which includes the effect of wind drag, has been developed for the stern trawler Zandberg. This spraying model has been incorporated into an icing model for the same vessel. A three-dimensional grid cell mesh is superimposed on the surface of the ship so that the local spray flux and icing rate on each grid cell can be calculated using the combined spraying and icing models. The disappearance of the Blue Mist II is used as a case study to illustrate the performance of the icing model. Under these severe icing conditions with off-head winds, the model predicts an icing rate of more than 13 tonnes per hour for the Zandberg, and the ice distribution is highly asymmetrical. This ice loading is the most dangerous condition for the ship's stability.

Reduction of frictional resistance by air bubble lubrication

2009 ◽  
Author(s):  
E. J. Foeth ◽  
R. Eggers ◽  
I. van der Hout ◽  
F. H. H. A. Quadvlieg
Keyword(s):  
Frictional Resistance ◽  
Full Scale ◽  
Air Injection ◽  
Environmental Footprint ◽  
Propulsive Efficiency ◽  
Air Bubble ◽  
Model Scale ◽  
Air Lubrication ◽  
Series Of Experiments ◽  
Performance Gains

The reduction of resistance and the increase of propulsive efficiency are major drivers for ship designers both for economic reasons and increasingly for reducing the ship’s environmental footprint. Reducing the frictional resistance by air injection below the ship in combination with special coatings is an active area of research; anecdotally, performance gains are usually large. The paper gives an overview of some model scale and full scale measurements results of ships with one type of air lubrication—air bubble lubrication—performed by MARIN. The experiments were performed under the SMOOTH project. The first series of experiments focused on an inland shipping vessel that was tested both on model scale and on full scale, with and without air lubrication. A second series of tests consisted of maneuvering and seakeeping tests with a model painted with different coatings and with and without air lubrication. No appreciable effects of air bubble lubrication were found during the resistance and propulsion tests at either model or full scale and no significant effects of air bubble lubrication on maneuvering and seakeeping model tests could be determined.

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.

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