Model-scale underwater radiated noise measurements: A study of repeatability, sensitivity to loading condition variations and correlation to full scale data

This article provides experimental results and shows comparisons of 90 sideslip performance of a fully skirted air cushion vehicle using theoretical predictions, 1/12th model scale data, and full-scale data. The goal is to establish a relation among the three data sets and draw conclusions for use in future predictions. First, this article presents results and analysis of tow tank data obtained in late 2008. Then, the Froude scaled data are used to obtain an empirical drag coefficient. A comparison is made between this approach and a theoretical prediction proposed in previous work. An iterative, one dimensional deceleration algorithm is then constructed using the coefficients to predict the deceleration of a full-scale craft having similar skirt characteristics. The predictions are performed for three craft weights and the resulting deceleration rates as a function of Froude number are presented. Data obtained from full-scale testing are then compared with the results of both the model-based algorithm and the theoretical prediction. In general, the model-based simulation overpredicts the deceleration rate for a full-scale craft, whereas the theoretical prediction is more accurate. The model simulation is recomputed using a developed correction factor and is plotted against the theoretical and full-scale deceleration, revealing favorable results. Lastly, a review of the technique is described and recommendations for improvements and following work are provided.

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Full scale measurement of underwater radiated noise from a coastal tanker

OCEANS 2015 - Genova ◽

10.1109/oceans-genova.2015.7271771 ◽

2015 ◽

Cited By ~ 2

Author(s):

A. T. Johansson ◽

J. Hallander ◽

R. Karlsson ◽

A. Langstrom ◽

M. Turesson

Keyword(s):

Full Scale ◽

Radiated Noise ◽

Underwater Radiated Noise

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Model-Scale/Full-Scale Correlation of NRC-OCRE’s Model Resistance, Propulsion and Maneuvering Test Results

Volume 8: Ian Jordaan Honoring Symposium on Ice Engineering ◽

10.1115/omae2015-42114 ◽

2015 ◽

Author(s):

Michael Lau

Keyword(s):

Test Data ◽

Model Test ◽

Model Tests ◽

Full Scale ◽

Test Results ◽

Sea Trial ◽

Model Scale ◽

Performance Predictions ◽

Ice Strength ◽

Scale Data

There are a variety of model ices and test techniques adopted by model test facilities. Most often, the clients would ask: “How well can you predict the full scale performance from your model test results?” Model-scale/full-scale correlation becomes an important litmus test to validate a model test technique and its results. This paper summarizes the model-scale/full-scale correlation performed on model test data generated at the National Research Council - Ocean, Coastal, and River Engineering’s (NRC-OCRE) test facility in St. John’s. This correlation includes ship performance predictions, i.e., resistance, propulsion and maneuvering. Selected works from NRC-OCRE on the USCGC icebreaker Healy, the CCGS icebreaker Terry-Fox, the CCGS R-Class icebreakers Pierre Radisson and Sir John Franklin and the CCGS icebreaker Louis S. St. Laurent were reviewed and summarized. The model tests were conducted at NRC-OCRE’s ice tank with the correct density (CD) EGADS model ice. This correlation is based on the concept that a “correlation friction coefficient” (CFC) can be used to predict full-scale ship icebreaking resistance from model test data. The CFCs have been compared for correlation studies using good-quality full-scale information for the five icebreaker models in the NRC-OCRE’s model test database. The review has shown a good agreement between NRCOCRE’s model test predictions and full-scale measurements. The resistance and power correlation were performed for five sets of full-scale data. Although there is substantial uncertainty on ice thickness and ice strength within the full scale data sets that contributes to data scattering, the data suggest a conservative estimate can be obtained to address reasonably this uncertainty by increasing the model prediction by 15% that envelopes most data points. Limited correlation for maneuvering in ice was performed for the USCGC icebreaker Healy. Selected test conditions from the sea trials were duplicated for the maneuvering tests and turning diameters were measured from the arcs of partial circles made in the ice tank. Performance predictions were then compared to the full-scale data previously collected. Despite some discrepancy in ice strength and power level between the model tests and sea trial, the model data agree well with the sea trial data except for three outliers. Otherwise, the maneuvering data show a good correlation between the model test and sea trial results.

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

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090217693418 ◽

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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Correlation of Prototype and Model-Scale Wave Wake Characteristics of a Catamaran

Marine Technology and SNAME News ◽

10.5957/mtsn.2009.46.1.1 ◽

2009 ◽

Vol 46 (01) ◽

pp. 1-15

Author(s):

Gregor J. Macfarlane

Keyword(s):

Experimental Data ◽

Experimental Investigation ◽

Water Depth ◽

Correlation Factor ◽

Scale Height ◽

Full Scale ◽

Scale Model ◽

Model Scale ◽

Speed Range ◽

Scale Data

This paper summarizes an experimental investigation into the correlation of model-scale wave wake measurements against full-scale trial results for a 24-meter long catamaran operating over a range of length Froude numbers. Both full-scale and 1/15th-scale model experiments were conducted over the range of length Froude numbers of approximately 0.3 to 1.0 (full-scale speed range of 6 to 28 knots). The water depth during the experiments was approximately 12 meters, with corresponding depth Froude numbers ranging from subcritical (~0.3), through a transcritical range (~0.8 to 1.1) into low supercritical speeds (up to ~1.3). The results of the investigation confirm that a correlation factor of close to unity be applied when using model-scale experimental data to predict the full-scale height and period of the maximum wave generated by similar catamarans operating within such speed ranges. Consequently, it is expected that the energy of the maximum waves can also be accurately predicted from model-scale data. This paper also provides useful guidance notes for the conduct of full-scale wave wake experiments and highlights some issues regarding the identification of the maximum wave(s) generated when vessels operate at trans and/or supercritical depth Froude numbers.

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