Similarity of Rudder Effectiveness and Speed Response of a Free-Running Model Ship

2014 ◽  
Author(s):  
Michio Ueno ◽  
Yoshiaki Tsukada
Keyword(s):  
Correction Factor ◽  
Numerical Approach ◽  
Full Scale ◽  
Scale Model ◽  
Time Varying ◽  
Detailed Method ◽  
Scale Models ◽  
Free Running ◽  
Factor Constant ◽  
Speed Response

The authors had proposed a method, rudder effectiveness correction, to realize full-scale equivalent manoeuvring motion using scale models with the auxiliary thruster. In the method they introduced the rudder effectiveness correction factor to make the effective inflow velocity to rudder defined in a steady straight course similar to a corresponding full-scale ship. The method assumes the factor constant during manoeuvring motion for a model ship running at a constant propeller rate of revolution. In this report the authors propose by a numerical approach a detailed method ensuring more precisely the similarity of manoeuvring motion than the former one. The detailed method takes into account the similarities both of the speed response and rudder effectiveness. The time-varying control both of the propeller rate of revolution and rudder effectiveness correction factor, based on the new method, enables scale model ships to realize the similar manoeuvring motion to full-scale ships more accurately. Simulation calculations using the modular mathematical model of manoeuvring motion clarifies how well the detailed method raise the precision of the full-scale equivalent manoeuvring motion in free-running model ship testing comparing with the former method.

Evaluation of a Small and Fast Planing Boat’s Seakeeping Performance at the Design Stage

2015 ◽  
Author(s):  
Dong Jin Kim ◽  
Sun Young Kim
Keyword(s):  
Model Tests ◽  
Full Scale ◽  
Scale Model ◽  
Design Stage ◽  
Small Scale ◽  
Irregular Wave ◽  
Seakeeping Performance ◽  
Head Waves ◽  
Scale Ratio ◽  
Free Running

Seakeeping performance of a planing boat should be sufficiently considered and evaluated at the design stage for its safe running in rough seas. Model tests in seakeeping model basins are often performed to predict the performance of full-scale planing boats. But, there are many limitations of tank size and wave maker capacity, in particular, for fast small planing boats due to small scale ratio and high Froude numbers of their scale models. In this research, scale model tests are tried in various test conditions, and results are summarized and analyzed to predict a 3 ton-class fast small planing boats designed. In a long and narrow tank, towing tests for a bare hull model are performed with regular head waves and long crested irregular head waves. Motion RAOs are derived from irregular wave tests, and they are in good agreements with RAOs in regular waves. Next, model ships with one water-jet propulsion system are built, and free running model tests are performed in ocean basins. Wave conditions such as significant heights, modal periods, and directions are varied for the free running tests. Motion RMS values, and RAOs are obtained through statistical approaches. They are compared with the results in captive tests for the bare hull model, and are used to predict the full-scale boat performances.

Paper 10: The Influence of Moisture on the Efficiency of a One-Third Scale Model Low Pressure Steam Turbine

1965 ◽  
Vol 180 (15) ◽  
pp. 39-49
Author(s):  
A. Smith
Keyword(s):  
Steam Turbine ◽  
Correction Factor ◽  
Rotational Speed ◽  
Direct Injection ◽  
Maximum Level ◽  
Low Pressure ◽  
Full Scale ◽  
Scale Model ◽  
Supersaturation Ratio ◽  
Multi Stage

The rapid increase in blade-tip diameters and peripheral speeds of low pressure turbines in large 3000 rev/min turbo-generators has presented the designer with many difficult mechanical and aerodynamic problems. To assist in the aerodynamic development of such blading, design studies on an experimental low pressure (l.p.) turbine were started early in 1959. Economic and technical considerations limited the choice to a one-third scale model steam turbine capable of running at three times the normal rotational speed to preserve full-scale working Mach numbers on the blading. Overall output and steam consumption were measured on a hydraulic dynamometer and by volumetric tanking respectively. The inlet steam temperature was controlled by a direct injection desuperheater so that the expansion could be kept dry for traversing or reduced to design inlet temperatures for normal wet running. Three multi-stage sets with last row blade diameters corresponding to 90-in, 120-in, and 136-in full-scale turbines have now been tested in the experimental turbine and the wet performance of the largest forms the subject of this paper. The overall wetness losses on the model 136-in diameter turbine have been assessed from a series of seven tests in which the inlet superheat and rotational speed were varied whilst maintaining fixed inlet and outlet pressure levels. To isolate the stage moisture correction factor (α), however, where a stage-by-stage approach was adopted, in which the dry stage efficiencies were initially established from interstage traverses under dry steam conditions. Two wet steam analyses were made, the first assuming equilibrium and the second supersaturated expansion, but the choice seemed immaterial since the moisture correction factor was almost the same for both. In the case of the supersaturated expansion calculation, it was necessary to establish the point of reversion from supersaturated to near equilibrium expansion (the Wilson point) and supplementary water extraction results were used to establish the maximum supersaturation ratio. These suggest that the maximum level is nearer to 3 in the model turbine than to the value of 4–6 quoted for convergent-divergent nozzles.

scholarly journals Method for calculating technical characteristics and parameters of movement of scale models of wheeled vehicles, ensuring the similarity of the processes during testing

2021 ◽  
Vol 1 (3) ◽  
pp. 23-30
Author(s):  
M.M. Zhileykin ◽  
◽  
M.M. Zhurkin ◽  
Keyword(s):  
Full Scale ◽  
Scale Model ◽  
Simulation Methods ◽  
Main Difficulty ◽  
Experimental Development ◽  
Scale Factors ◽  
Wheeled Vehicle ◽  
Scale Models ◽  
Motion Parameters ◽  
Wheeled Vehicles

Nowadays, when designing new vehicle models, there is a need to test certain solutions for the formation of a technical appearance both by simulation methods and on production samples. Full-scale road tests of vehicles make it possible to maintain full dynamic similarity during the experi-ment, but they can be carried out only after manufacturing of a vehicle prototype, which requires a lot of material costs. One of the ways to solve this problem is to create models that are a reduced copy of the designed vehicle. The main difficulty that appears when testing a scale model of vehicle is the need to accurately reproduce the conditions that occur when driving in real road conditions. The purpose of this paper is to find a relationship between the parameters of a production vehicle and a scale model for experimental development of algorithms for the dynamic stabilization of a wheeled vehicle. A method for calculating the technical characteristics and motion parameters of scale models for real full-scale wheeled vehicles while ensuring the similarity of the ongoing pro-cesses for scale models and for production vehicles is proposed on the basis of the theory of similar-ity. The main dependences for scale factors for force, kinematic and dimensional factors are ob-tained. The similarity of the occurring processes was confirmed by the methods of simulation mod-eling of the movement of a scale model and a full-scale wheeled vehicle.

Instantaneous Leakage Evaluation of Metal Cask at Drop Impact

2006 ◽  
Author(s):  
Hirofumi Takeda ◽  
Norio Kageyama ◽  
Masumi Wataru ◽  
Ryoji Sonobe ◽  
Koji Shirai ◽  
...  
Keyword(s):  
Drop Impact ◽  
Full Scale ◽  
Drop Test ◽  
Leak Rate ◽  
Scale Model ◽  
Storage Facility ◽  
Gas Leakage ◽  
Scale Models ◽  
Helium Gas ◽  
Drop Tests

There have been a lot of tests and analyses reported for evaluation of drop tests of metal casks. However, no quantitative measurement has ever been made for any instantaneous leakage through metal gaskets during the drop tests due to loosening of the bolts in the containments and lateral sliding of the lids. In order to determine a source term for radiation exposure dose assessment, it is necessary to obtain fundamental data of instantaneous leakage. In this study, leak tests were performed by using scale models of the lid structure and a full scale cask without impact limiters simulating drop accidents in a storage facility, with aim of measuring and evaluating any instantaneous leakage at drop impact. Prior to drop tests of a full scale metal cask, a series of leakage tests using scale models were carried out to establish the measurement method and to examine a relationship between the amount of the lateral sliding of the lid and the leak rate. It was determined that the leak rate did not depend on the lateral sliding speeds. Drop tests of a full scale metal cask without impact limiters were carried out by simulating drop accidents during handling in a storage facility. The target was designed to simulate a reinforced concrete floor in the facility. The first test was a horizontal drop from a height of 1 m. The second test simulated a rotational impact around an axis of a lower trunnion of the cask from the horizontal status at a height of 1 m. In the horizontal drop test, the amount of helium gas leakage was calculated by integrating the leak rate with time. The total amount of helium gas leakage from the primary and secondary lids was 1.99×10−6Pa · m3. This value is 9.61×10−9% of the initially installed helium gas. The amount of leakage was insignificant. In the rotational drop test, the total amount of leakage from the primary and secondary lids was 1.74×10−5Pa·m3. This value is 8.45×10−8% of the initially installed helium gas. This value was larger than that of the horizontal drop test. Nevertheless, the amount of leakage was also insignificant. The relationship between the maximum sliding displacement of the lid and the leak rate coincided between the tests of a scale model and a full scale metal cask.

Stopping Test Method for Free-Running Model Ship Equipped With Auxiliary Thruster

2016 ◽  
Author(s):  
Michio Ueno ◽  
Yoshiaki Tsukada
Keyword(s):  
Control Method ◽  
Stopping Time ◽  
Full Scale ◽  
Test Method ◽  
Control Methods ◽  
Safe Side ◽  
Free Running ◽  
Advance Ratio ◽  
Three Degree Of Freedom ◽  
Speed Response

The authors report how to estimate stopping ability of full-scale ships using free-running model equipped with an auxiliary thruster. Theoretical analysis based on a modular mathematical model clarifies the similarity of three-degree-of-freedom stopping manoeuvre of a model ship to full-scale cannot be ensured by the use of auxiliary thruster. The authors, however, propose JSC, propeller advance ratio J and speed correction, ensuring the equality of J and the similarity of speed response of free-running model ship to full-scale during stopping manoeuvre. JSC is a control method of free-running model ship equipped with an auxiliary thruster for estimating stopping ability of full-scale ship from the viewpoint of safety. Numerical simulation confirms JSC gives safe side estimates of stopping ability with regard to the track reach and stopping time with acceptable margin. The analysis shown here proves the advantage of JSC comparing with possible other control methods of free-running model ships.

The Use of Ship Manœuvre Simulators

1975 ◽  
Vol 28 (3) ◽  
pp. 358-362
Author(s):  
Toni B. K. Ivergård
Keyword(s):  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Scale Models ◽  
Function Diagram ◽  
Small Scale Model

It is becoming common for ship's officers and pilots to attend special simulator courses to learn the handling of new ships or the navigation of particular channels. A simulator can be defined as any likeness of an object or objects, thus a simple drawing of a ship's bridge is a form of simulation, as is a function diagram or a small-scale model; full-scale models or ‘mock-ups’ are more advanced types of simulator. However a simulator is more commonly taken to be a more complicated set of full-scale models in combination with small-scale models, which usually have the ability to respond to different manœuvring actions with changes in the instruments or the surroundings.

Effect of mesh on CFD aerodynamic performances of a container ship

2020 ◽  
Vol 20 (3) ◽  
pp. 343-353
Author(s):  
Ngo Van He ◽  
Le Thi Thai
Keyword(s):  
Water Surface ◽  
Reference Model ◽  
Full Scale ◽  
Scale Model ◽  
Container Ship ◽  
Ansys Fluent ◽  
Remarkable Effect ◽  
Aerodynamic Performances ◽  
Mesh Convergence

In this paper, a commercial CFD code, ANSYS-Fluent has been used to investigate the effect of mesh number generated in the computed domain on the CFD aerodynamic performances of a container ship. A full-scale model of the 1200TEU container ship has been chosen as a reference model in the computation. Five different mesh numbers for the same dimension domain have been used and the CFD aerodynamic performances of the above water surface hull of the ship have been shown. The obtained CFD results show a remarkable effect of mesh number on aerodynamic performances of the ship and the mesh convergence has been found. The study is an evidence to prove that the mesh number has affected the CFD results in general and the accuracy of the CFD aerodynamic performances in particular.

Modeling and Assessment of the Produced Water Discharges from Offshore Petroleum Platforms

2007 ◽  
Vol 42 (4) ◽  
pp. 303-310 ◽  
Author(s):  
Zhi Chen ◽  
Lin Zhao ◽  
Kenneth Lee ◽  
Charles Hannath
Keyword(s):  
Random Walk ◽  
Produced Water ◽  
Model Development ◽  
Three Dimensional ◽  
Monitoring Program ◽  
Ecological Monitoring ◽  
Numerical Approach ◽  
Ocean Model ◽  
Scale Model ◽  
Water Stream

Abstract There has been a growing interest in assessing the risks to the marine environment from produced water discharges. This study describes the development of a numerical approach, POM-RW, based on an integration of the Princeton Ocean Model (POM) and a Random Walk (RW) simulation of pollutant transport. Specifically, the POM is employed to simulate local ocean currents. It provides three-dimensional hydrodynamic input to a Random Walk model focused on the dispersion of toxic components within the produced water stream on a regional spatial scale. Model development and field validation of the predicted current field and pollutant concentrations were conducted in conjunction with a water quality and ecological monitoring program for an offshore facility located on the Grand Banks of Canada. Results indicate that the POM-RW approach is useful to address environmental risks associated with the produced water discharges.

Sign in / Sign up

Export Citation Format

Share Document