Infra-Red Signature Suppression for Marine Gas Turbines: Comparison of Sea Trial and Model Test Results for the DRES Ball IRSS System

1992 ◽  
Author(s):  
A. M. Birk ◽  
D. Vandam
Keyword(s):  
Model Test ◽  
Gas Turbines ◽  
Flow Model ◽  
Full Scale ◽  
Scale Model ◽  
Test Results ◽  
Sea Trial ◽  
Infra Red ◽  
Plume Temperature ◽  
Better Than

Sea Trials have recently been underway for Canada’s new City Class Patrol Frigate (CPF). These trials provided the first opportunity to measure the performance of the new DRES Ball Infra-red Signature Suppression (IRSS) system installed on a ship. Prior to these trials 1/4 scale hot flow model test and computer simulation performance results were available. The CPF DRES Ball IRSS systems are installed on the exhaust uptakes of the GE LM2500 main gas turbines. The DRES Ball provides both metal surface cooling for all view angles and plume cooling. The DRES Ball significantly reduces the IR signature of the LM2500 exhaust. This paper presents a comparison between the 1/4 scale hot flow model test results with the full scale sea trial results. Performance variables included in the comparison are; metal surface temperatures, back pressure, plume temperature distribution, and surface static pressures. Because of the confidential nature of the DRES Ball system performance, all classified data has been nondimensionalized so that only relative comparisons can be made between the full scale and 1/4 scale data. The results show that the full scale system performs better than the 1/4 scale model because of Reynolds number effects. The plume temperature, surface temperatures and back pressure were all lower (better) than in the 1/4 scale model tests. One of the original concerns with the installation was that relative wind would degrade the performance of the DRES Ball onboard a ship. The wind effect was found to be benign during the trials.

Infrared Signature Suppression for Marine Gas Turbines: Comparison of Sea Trial and Model Test Results for the DRES Ball IRSS System

1994 ◽  
Vol 116 (1) ◽  
pp. 75-81 ◽  
Author(s):  
A. M. Birk ◽  
D. VanDam
Keyword(s):  
Model Test ◽  
Gas Turbines ◽  
Flow Model ◽  
Full Scale ◽  
Scale Model ◽  
Test Results ◽  
Sea Trial ◽  
Infrared Signature ◽  
Plume Temperature ◽  
Better Than

Sea Trials have recently been underway for Canada’s new City Class Patrol Frigate (CPF). These trials provided the first opportunity to measure the performance of the new DRES Ball Infrared Signature Suppression (IRSS) system installed on a ship. Prior to these trials 1/4-scale hot flow model test and computer simulation performance results were available. The CPF DRES Ball IRSS systems are installed on the exhaust uptakes of the GE LM2500 main gas turbines. The DRES Ball provides both metal surface cooling for all view angles and plume cooling. The DRES Ball significantly reduces the IR signature of the LM2500 exhaust. This paper presents a comparison between the 1/4-scale hot flow model test results with the full-scale sea trial results. Performance variables included in the comparison are: metal surface temperatures, back pressure, plume temperature distribution, and surface static pressures. Because of the confidential nature of the DRES Ball system performance, all classified data have been nondimensionalized so that only relative comparisons can be made between the full-scale and 1/4-scale data. The results show that the full-scale system performs better than the 1/4-scale model because of Reynolds number effects. The plume temperature, surface temperatures, and back pressure were all lower (better) than in the 1/4-scale model tests. One of the original concerns with the installation was that relative wind would degrade the performance of the DRES Ball onboard a ship. The wind effect was found to be benign during the trials.

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

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.

Correlation Allowances in Model Tests Results: A Delicate Balance Between Performance, Accuracy and Commercial Interests?

2016 ◽  
Author(s):  
Gerco Hagesteijn ◽  
Patrick Hooijmans ◽  
Karola van der Meij
Keyword(s):  
Model Test ◽  
Performance Prediction ◽  
Model Tests ◽  
Full Scale ◽  
Test Results ◽  
Power Performance ◽  
Low Light ◽  
Sea Trial ◽  
Performance Accuracy ◽  
Full Scale Tests

Model tests at ballast and design draught are used to convert the sea trial results from the ballast trial draught to the contractual design draught. Correlation allowances in model test results and their effect on the trial performance prediction are of major importance. Nowadays it is not only typical to verify the contract speed but also the EEDI certification requires a verification of the speed power performance of the vessel. The use of a to favorable CA-value may lead to attractive performance figures, but also leads to higher fuel consumption figures than expected. Furthermore the design point of the propeller is affected, which leads to a too low light running margin and in some cases to erosive cavitation. During a study, large spreading in the values of the correlation allowances for design draughts have been found for merchant vessels tested at different model test institutes, but at ballast trial draught the spreading is much less. Can it happen that some institutes select favorable correlations allowances on the basis of inaccurate trial data of shipyards? Or should we accept a large spreading in correlation allowances and have these indeed been confirmed by sea trials at design draught? This paper will present a discussion using the experience of a large full scale trial database as well as the accuracy of model and full scale tests.

scholarly journals Full-Scale/Model Test Comparisons to Validate the Traditional ABL Wind Tunnel Simulation Technique: A Literature Review

2017 ◽  
Author(s):  
X.X. Cheng ◽  
J. Dong ◽  
Y. Peng ◽  
L. Zhao ◽  
Y.J. Ge
Keyword(s):  
Wind Tunnel ◽  
Literature Review ◽  
Model Test ◽  
Full Scale ◽  
Simulation Technique ◽  
Scale Model ◽  
Test Results ◽  
Wind Tunnel Simulation ◽  
Measurement Results ◽  
New Research

Full-scale/model test comparison studies to validate the traditional ABL wind tunnel simulation technique are reviewed. According to the literature review, notable discrepancies between full-scale measurement results and model test results were observed by most performed comparison studies, but the causes of the observed discrepancies were not revealed in a scientific way by those studies. In this regard, a new research scheme for future full-scale/model test comparison studies is proposed in this article, which utilizes the multiple-fan actively controlled wind tunnel simulation technique. With the new research scheme, future full-scale/model test comparison studies are expected to reasonably disclose the main problems with the traditional ABL wind tunnel simulation technique, and the technique can be improved correspondingly.

Benchmarking of Truss Spar Vortex Induced Motions Derived From CFD With Experiments

2005 ◽  
Author(s):  
John Halkyard ◽  
Senu Sirnivas ◽  
Samuel Holmes ◽  
Yiannis Constantinides ◽  
Owen H. Oakley ◽  
...  
Keyword(s):  
Scale Up ◽  
Vertical Cylinder ◽  
Reynolds Numbers ◽  
Full Scale ◽  
Scale Model ◽  
Current Direction ◽  
Test Results ◽  
Helical Strakes ◽  
Truss Spar ◽  
Scale Data

Floating spar platforms are widely used in the Gulf of Mexico for oil production. The spar is a bluff, vertical cylinder which is subject to Vortex Induced Motions (VIM) when current velocities exceed a few knots. All spars to date have been constructed with helical strakes to mitigate VIM in order to reduce the loads on the risers and moorings. Model tests have indicated that the effectiveness of these strakes is influenced greatly by details of their design, by appurtenances placed on the outside of the hull and by current direction. At this time there is limited full scale data to validate the model test results and little understanding of the mechanisms at work in strake performance. The authors have been investigating the use of CFD as a means for predicting full scale VIM performance and for facilitating the design of spars for reduced VIM. This paper reports on the results of a study to benchmark the CFD results for a truss spar with a set of model experiments carried out in a towing tank. The focus is on the effect of current direction, reduced velocity and strake pitch on the VIM response. The tests were carried out on a 1:40 scale model of an actual truss spar design, and all computations were carried out at model scale. Future study will consider the effect of external appurtenances on the hull and scale-up to full scale Reynolds’ numbers on the results.

scholarly journals A COMPARISON BETWEEN MODEL AND PROTOTYPE WAVES IN HARBOURS

1978 ◽  
Vol 1 (16) ◽  
pp. 38
Author(s):  
Sverre Bjordal ◽  
Alf Torum
Keyword(s):  
Physical Model ◽  
Model Test ◽  
Field Measurements ◽  
Full Scale ◽  
Common Method ◽  
Test Results ◽  
Open Coast ◽  
The World ◽  
Mooring Forces ◽  
Absolute Basis

A common method of estimating the sheltering effects of different breakwater locations and layouts is to carry out physical model wave disturbance tests. Such tests have been carried out in different laboratories throughout the world for many years. But to our knowledge no reports are available in the literature showing comparison between model measurements and field measurements. The trend is that we know more and more on the wave cl imate along our coasts. Hence we have a better basis to make our economical calculations on breakwaters. We therefore also want to operate our models on a more absolute basis rather than on a comparative basis. The trend in recent years has also been to study breakwater locations and layouts in order to minimize mooring forces and ship movements. On this background VHL found a comparison between model test results and field measurements necessary. Full scale measurements of waves were carried out in two harbours by VHL during the winter 1976/77. This paper will present the results of the comparison of the model and the full scale measurements in Berlevag and Vard0 fishing harbours on the open coast of Finnmark in the northern part of Norway (Fig. I) . The model tests, as well as the full scale measurements, have been sponsored by the Norwegian State Harbour Authorities.

scholarly journals FULL-SCALE MODEL TEST ON THE APPLICABILITY OF L-SHAPED GEOSYNTHETIC DRAIN SYSTEM TO TERRE ARMÉE WALL AGAINST HEAVY RAINFALL

2013 ◽  
Vol 28 (0) ◽  
pp. 353-360
Author(s):  
Je-Min BAEK ◽  
Satoru SHIBUYA ◽  
Jin-Suk HUR ◽  
Takefumi OGATA ◽  
Byeong-Su KIM ◽  
...  
Keyword(s):  
Model Test ◽  
Heavy Rainfall ◽  
Full Scale ◽  
Scale Model
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