The Effect of Counter Length on Hull Resistance

1989 ◽  
Author(s):  
Andrew R. Claughton
Keyword(s):  
Regression Analysis ◽  
Wave Profile ◽  
Full Scale ◽  
Hull Form ◽  
Towing Tank ◽  
Scale Resistance ◽  
Analysis Methods ◽  
Sinkage And Trim ◽  
Resistance Curves ◽  
Resistance Data

Towing Tank tests on a single 2.4 m LOA model hull form with 3 alternative counter lengths, and 2 alternative rudder configurations have been carried out in the Southampton Towing Tank. The results were used to derive predictions of full scale resistance curves for a 10m L WL racing yacht. In addition to the resistance data, sinkage and, trim were measured. Wave profile measurements were also made to determine the influence of counter length on the hull generated waves. The resistance curves are presented for the 5 configurations investigated and the results are compared with published regression analysis methods of estimating hull resistance based on geometric hull parameters.

Uncertainty Assessment for Towing Tank Tests With Example for Surface Combatant DTMB Model 5415

2005 ◽  
Vol 49 (01) ◽  
pp. 55-68 ◽  
Author(s):  
Joe Longo ◽  
Fred Stern
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Uncertainty Assessment ◽  
Wave Profile ◽  
Assessment Methodology ◽  
Towing Tank ◽  
Measurement Systems ◽  
Sinkage And Trim ◽  
Surface Combatant ◽  
Wave Elevations

Uncertainty assessment methodology, procedures, and results are presented for most typical towing tank tests using a 3.048 m geosym of naval combatant DTMB model 5415, which is an established benchmark for computational fluid dynamics validation. The tests include resistance, sinkage and trim, wave profile, wave elevations, and nominal wake. The procedures are summarized and follow International Towing Tank Conference Quality Manual Procedures. The facility and measurement systems are briefly described, and detailed uncertainty assessment examples for each test are provided with descriptions of bias and precision limits and total uncertainties.

scholarly journals Estimation of Great Lakes Bulk Carrier Resistance Based on Model Test Data Regression

1973 ◽  
Vol 10 (04) ◽  
pp. 364-379
Author(s):  
Peter M. Swift ◽  
Horst Nowacki ◽  
Joseph P. Fischer
Keyword(s):  
Regression Analysis ◽  
Great Lakes ◽  
Test Data ◽  
Model Test ◽  
Full Scale ◽  
Bulk Carrier ◽  
Scale Resistance ◽  
Data Regression ◽  
Bulk Carriers

Tank data have been collected, analyzed, and standardized for 50 tests of Great Lakes bulk carriers. Regression analysis has been applied in order to estimate the coefficient of residuary resistance of such vessels in terms of their nondimensional form parameters. The results are presented for Froude numbers from 0.11 to 0.18 in the form of coefficients obtained by three different regressions, and in the form of charts at Froude numbers 0.14 and 0.16. Examples illustrate the use of the regression formulas in estimating the full-scale resistance.

HYDRODYNAMIC PERFORMANCES OF WARPED HARD CHINE DISPLACEMENT HULL FORM

2014 ◽  
Vol 156 (B1) ◽  
Author(s):  
E Begovic ◽  
C Bertorello ◽  
A Bove ◽  
S Pennino
Keyword(s):  
Experimental Tests ◽  
Full Scale ◽  
Wave Steepness ◽  
Regular Waves ◽  
Hull Form ◽  
Realistic Condition ◽  
Sinkage And Trim ◽  
Reported Data ◽  
Resistance Tests

The results of experimental tests relative to resistance, seakeeping and roll decay of a warped hard chine hull form, suitable for large yacht design are reported. To better investigate the effect of hard chine, a round bilge identical model has been tested. Resistance tests have been performed at FV ranging from 0.90 to 4.14, for three different LCG. Results for resistance, sinkage and trim are given. For the most realistic condition dynamic wetted surface is determined separating pressure and whisker spray areas to allow reliable full scale powering predictions. For the same static trim condition, heave, pitch and accelerations have been measured for head sea at FV = 1.35 and 1.89 in regular waves for different /Lratios at constant wave steepness H/ = 1/50. Roll decay at five speeds and roll at zero speed were investigated. The reported data and considerations represent a reference for the implementation of hard chine hull form in the design of displacement and semidisplacement large yachts.

Limitations in Scaling Towing Tests for Simple Pontoon Shapes

2017 ◽  
Author(s):  
Jan Willem Krijger ◽  
Dimitris Chalkias
Keyword(s):  
Reynolds Number ◽  
Form Factor ◽  
Full Scale ◽  
Test Results ◽  
Number Range ◽  
Towing Tank ◽  
Scale Resistance ◽  
Resistance Prediction ◽  
Cylinders And Spheres ◽  
Typical Model

For merchant vessels full scale resistance is determined by extrapolating the towing tank tests using Hughes’ method. For blunt and simple shapes this approach might not be valid due to significant Reynolds dependency. In this paper a study is presented on two semi-submersible pontoon shapes and one drillship. The resistance for these hulls was calculated using URANSE simulations. Four different scales: 1:1, 1:10, 1:20 and 1:40 were investigated for all the different hull shapes. The goal of the study was to determine a form factor to use when scaling towing test results to full scale. However due to the simple shapes of the pontoons it was found that there was a significant Reynolds dependency at all the different scales. This Reynolds dependency had much more influence on the full scale resistance than a form factor. For the drillship no significant Reynolds dependency was found and applying ITTC 1978 method [1] with a form factor improved the accuracy of the resistance prediction compared to using the Froude method which is not using a form factor. The simple pontoon shapes used were based on a combination of boxes, cylinders and spheres. The cylindrical and spherical shapes have a Reynolds regime where a drag crisis occurs. For all the shapes the drag crisis regimes were right in the same Reynolds number range at which typical model tests would be performed. Therefore performing towing tests and making accurate full scale resistance predictions for these simple shapes is not straightforward. Applying the ITTC 1978 method does not provide the same level of accuracy as it does for merchant vessels. The paper identifies limitations involved in scaling towing test results for typical offshore hull shapes. Further possible solutions are proposed to improve the accuracy of the resistance predictions.

Numerical Investigation for Resistance Characteristics of LNG Carrier

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
A. Y. Sian ◽  
A. Maimun ◽  
A. Priyanto ◽  
Yasser M. Ahmed ◽  
M. Nakisa ◽  
...  
Keyword(s):  
Free Surface ◽  
Free Surface Flow ◽  
General Purpose ◽  
Surface Flow ◽  
Liquefied Natural Gas ◽  
Wave Profile ◽  
Navier Stokes ◽  
Hull Form ◽  
Towing Tank ◽  
Calm Water

Reynolds Averaged Navier-Stokes (RANS) computations are conducted with general purpose CFD solver Fluent to examine the resistance and viscous free surface flow of Liquefied Natural Gas (LNG) carrier hull form in calm water. Shear-stress transport k-w turbulence model and multiphase volume of fluid (VOF) free surface employed. The resistance characteristics and wave profile of the LNG model also investigated. Model tests were conducted in towing tank for validation of the computed results. Overall results agree fairly well with experimental data, reveals the feasibility of RANS method in practical prediction of LNG resistance characteristics.

DETERMINATION OF WAVE SLAMMING LOADS ON HIGH-SPEED CATAMARANS BY HYDROELASTIC SEGMENTED MODEL EXPERIMENTS

2021 ◽  
Vol 153 (A3) ◽  
Author(s):  
J Lavroff ◽  
M R Davis ◽  
D S Holloway ◽  
G Thomas
Keyword(s):  
Relative Motion ◽  
High Speed ◽  
Wave Profile ◽  
Full Scale ◽  
Bending Moments ◽  
Towing Tank ◽  
Segmented Model ◽  
Wave Slamming ◽  
Dynamic Wave

A 2.5m hydroelastic segmented catamaran model has been developed based on the 112m INCAT wave-piercer catamaran to simulate the vibration response during the measurement of dynamic slam loads in head seas. Towing tank tests were performed in regular seas to measure the dynamic slam loads acting on the centre bow and vertical bending moments acting in the demihulls of the catamaran model as a function of wave frequency and wave height to establish the operational loads acting on the full-scale 112m INCAT catamaran vessel. Peak slam forces measured on the bow of the model are found to approach the weight of the model, this being similar to the findings of full-scale vessel trials. A review of the motions of the hydroelastic segmented catamaran model found that the heave and pitch motions give a good indication of slamming severity in terms of the dimensionless heave and pitch accelerations. The dynamic wave slam forces are closely related to the relative motion between the bow and the incident wave profile.

Development and Assessment of a Total Resistance Optimized Bow for the AE 36

1994 ◽  
Vol 31 (02) ◽  
pp. 149-160
Author(s):  
Donald C. Wyatt ◽  
Peter A. Chang
Keyword(s):  
Experimental Data ◽  
Optimization Procedure ◽  
Wave Resistance ◽  
Scale Model ◽  
Optimization Approach ◽  
Nonlinear Constraints ◽  
Total Resistance ◽  
Hull Form ◽  
Final Design ◽  
Resistance Data

A numerically optimized bow design is developed to reduce the total resistance of a 23 000 ton ammunition ship (AE 36) at a speed of 22 knots. An optimization approach using slender-ship theory for the prediction of wave resistance is developed and applied. The new optimization procedure is an improvement over previous optimization methodologies in that it allows the use of nonlinear constraints which assure that the final design remains within practical limits from construction and operational perspectives. Analytic predictions indicate that the AE 36 optimized with this procedure will achieve a 40% reduction in wave resistance and a 33% reduction in total resistance at 22 knots relative to a Kracht elliptical bulb bow design. The optimization success is assessed by the analysis of 25th scale model resistance data collected at the David Taylor Research Center deepwater towing basin. The experimental data indicate that the optimized hull form yields a 51% reduction in wave resistance and a 12% reduction in total resistance for the vessel at 22 knots relative to the Kracht bulb bow design. Similarly encouraging results are also observed when comparisons are made with data collected on two other conventionally designed AE 36 designs.

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