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 WAVE RUN-UP PREDICTION VS. MODEL TEST RESULTS: A COMPARISON

1988 ◽  
Vol 1 (21) ◽  
pp. 47 ◽  
Author(s):  
Peter E. Gadd ◽  
Victor Manikian ◽  
Jerry L. Machemehl
Keyword(s):  
Physical Model ◽  
Model Test ◽  
Large Scale ◽  
Physical Model Test ◽  
Roughness Coefficient ◽  
Wave Steepness ◽  
Test Results ◽  
Shore Protection ◽  
Run Up

Large-scale physical model test measurements of wave run-up are compared with wave run-up prediction derived from the Shore Protection Manual (SPM). Noteworthy discrepancies between the results of these two methods have been identified that include substantial overestimation of wave run-up elevations using the SPM approach, and computation of roughness coefficient values that vary as a function of wave steepness. The slope armors tested in the study at model scales of 1:3 and 1:4 include linked concrete matting and overlapped gravel-filled fabric bags.

Wind effects on rough-walled and smooth-walled large cooling towers

2016 ◽  
Vol 20 (6) ◽  
pp. 843-864 ◽  
Author(s):  
XX Cheng ◽  
L Zhao ◽  
YJ Ge ◽  
R Dong ◽  
C Demartino
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Wind Tunnel ◽  
Flow Field ◽  
Atmospheric Boundary Layer ◽  
Model Test ◽  
Full Scale ◽  
Cooling Towers ◽  
Test Results ◽  
Wind Effects

Adding vertical ribs is recognized as a useful practice for reducing wind effects on cooling towers. However, ribs are rarely used on cooling towers in China since Chinese Codes are insufficient to support the design of rough-walled cooling towers, and an “understanding” hampers the use of ribs, which thinks that increased surface roughness has limited effects on the maximum internal forces that control the structural design. To this end, wind tunnel model tests in both uniform flow field with negligible free-stream turbulence and atmospheric boundary layer (ABL) turbulent flow field are carried out in this article to meticulously study and quantify the surface roughness effects on both static and dynamic wind loads for the purpose of improving Chinese Codes first. Subsequently, a further step is taken to obtain wind effects on a full-scale large cooling tower at a high Re, which are employed to validate the results obtained in the wind tunnel. Finally, the veracity of the model test results is discussed by investigating the Reynolds number (Re) effects on them. It has been proved that the model test results for atmospheric boundary layer flow field are all obtained in the range of Re-independence and the conclusions drawn from model tests and full-scale measurements basically agree, so most model test results presented in this article can be directly applied to the full-scale condition without corrections.

scholarly journals Model Test of a 1:8-Scale Floating Wind Turbine Offshore in the Gulf of Maine1

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Anthony M. Viselli ◽  
Andrew J. Goupee ◽  
Habib J. Dagher
Keyword(s):  
Wind Turbine ◽  
Physical Model ◽  
Test Data ◽  
Model Test ◽  
Test Site ◽  
Full Scale ◽  
Scale Construction ◽  
Offshore Wind ◽  
Testing Effort ◽  
Floating Wind Turbine

A new floating wind turbine platform design called VolturnUS developed by the University of Maine uses innovations in materials, construction, and deployment technologies such as a concrete semisubmersible hull and a composite tower to reduce the costs of offshore wind. These novel characteristics require research and development prior to full-scale construction. This paper presents a unique offshore model testing effort aimed at derisking full-scale commercial projects by providing scaled global motion data, allowing for testing of materials representative of the full-scale system, and demonstrating full-scale construction and deployment methods. A 1:8-scale model of a 6 MW semisubmersible floating wind turbine was deployed offshore Castine, ME, in June 2013. The model includes a fully operational commercial 20 kW wind turbine and was the first grid-connected offshore wind turbine in the U.S. The testing effort includes careful selection of the offshore test site, the commercial wind turbine that produces the correct aerodynamic thrust given the wind conditions at the test site, scaling methods, model design, and construction. A suitable test site was identified that produced scaled design load cases (DLCs) prescribed by the American Bureau of Shipping (ABS) Guide for Building and Classing Floating Offshore Wind Turbines. A turbine with a small rotor diameter was selected because it produces the correct thrust load given the wind conditions at the test site. Some representative data from the test are provided in this paper. Model test data are compared directly to full-scale design predictions made using coupled aeroelastic/hydrodynamic software. Scaled VolturnUS performance data during DLCs show excellent agreement with full-scale predictive models. Model test data are also compared directly without scaling against a numerical representation of the 1:8-scale physical model for the purposes of numerical code validation. The numerical model results compare favorably with data collected from the physical model.

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 Seakeeping Performance of a New Coastal Patrol Ship for the Croatian Navy

2020 ◽  
Vol 8 (7) ◽  
pp. 518
Author(s):  
Andrija Ljulj ◽  
Vedran Slapničar
Keyword(s):  
Full Scale ◽  
Coast Guard ◽  
Project Design ◽  
Test Results ◽  
Sea Trial ◽  
Seakeeping Performance ◽  
The World ◽  
Full Scale Tests ◽  
Marine Environmental ◽  
Scientific Purpose

This paper presents seakeeping test results for a coastal patrol ship (CPS) in the Croatian Navy (CN). The full-scale tests were conducted on a CPS prototype that was accepted by the CN. The seakeeping numerical prediction and model tests were done during preliminary project design. However, these results are not fully comparable with the prototype tests since the ship was lengthened in the last phases of the project. Key numerical calculations are presented. The CPS project aims to renew a part of the Croatian Coast Guard with five ships. After successful prototype acceptance trials, the Croatian Ministry of Defence (MoD) will continue building the first ship in the series in early 2020. Full-scale prototype seakeeping test results could be valuable in the design of similar CPS projects. The main aim of this paper is to publish parts of the sea trial results related to the seakeeping performance of the CPS. Coast guards around the world have numerous challenges related to peacetime tasks such as preventing human and drug trafficking, fighting terrorism, controlling immigration, and protecting the marine environmental. They must have reliable platforms with good seakeeping characteristics that are important for overall ship operations. The scientific purpose of this paper is to contribute to the design process of similar CPS projects in terms of the development of seakeeping requirements and their level of fulfillment on an actual ship.

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.

Determining Side-by-Side Current Loads Using CFD and Model Tests

2016 ◽  
Author(s):  
Arjen Koop
Keyword(s):  
Reynolds Number ◽  
Model Test ◽  
Full Scale ◽  
Test Results ◽  
Model Scale ◽  
Moment Coefficient ◽  
The Difference ◽  
The Moment ◽  
Good Agreement ◽  
Shielding Effects

When two vessels are positioned close to each other in a current, significant shielding or interaction effects can be observed. In this paper the current loads are determined for a LNG carrier alone, a Shuttle tanker alone and both vessels in side-by-side configuration. The current loads are determined by means of tow tests in a water basin at scale 1:60 and by CFD calculations at model-scale and full-scale Reynolds number. The objective of the measurements was to obtain reference data including shielding effects. CFD calculations at model-scale Reynolds number are carried out and compared with the model test results to determine the capability of CFD to predict the side-by-side current load coefficients. Furthermore, CFD calculations at full-scale Reynolds number are performed to determine the scale effects on current loads. We estimate that the experimental uncertainty ranges between 3% and 5% for the force coefficients CY and CMZ and between 3% and 10% for CX. Based on a grid sensitivity study the numerical sensitivity is estimated to be below 5%. Considering the uncertainties mentioned above, we assume that a good agreement between experiments and CFD calculations is obtained when the difference is within 10%. The best agreement between the model test results and the CFD results for model-scale Reynolds number is obtained for the CY coefficient with differences around 5%. For the CX coefficient the difference can be larger as this coefficient is mainly dominated by the friction component. In the model tests this force is small and therefore difficult to measure. In the CFD calculations the turbulence model used may not be suitable to capture transition from laminar to turbulent flow. A good agreement (around 5% difference) is obtained for the moment coefficient for headings without shielding effects. With shielding effects larger differences can be obtained as for these headings a slight deviation in the wake behind the upstream vessel may result in a large difference for the moment coefficient. Comparing the CFD results at full-scale Reynolds number with the CFD results at model-scale Reynolds number significant differences are found for friction dominated forces. For the CX coefficient a reduction up to 50% can be observed at full-scale Reynolds number. The differences for pressure dominated forces are smaller. For the CY coefficient 5–10% lower values are obtained at full-scale Reynolds number. The moment coefficient CMZ is also dominated by the pressure force, but up to 30% lower values are found at full-scale Reynolds number. The shielding effects appear to be slightly smaller at full-scale Reynolds number as the wake from the upstream vessel is slightly smaller in size resulting in larger forces on the downstream vessel.

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.

Model Test of a 1:8 Scale Floating Wind Turbine Offshore in the Gulf of Maine

2014 ◽  
Author(s):  
Anthony M. Viselli ◽  
Andrew J. Goupee ◽  
Habib J. Dagher
Keyword(s):  
Wind Turbine ◽  
Physical Model ◽  
Test Data ◽  
Model Test ◽  
Test Site ◽  
Full Scale ◽  
Scale Construction ◽  
Offshore Wind ◽  
Testing Effort ◽  
Floating Wind Turbine

A new floating wind turbine platform design called VolturnUS developed by the University of Maine uses innovations in materials, construction, and deployment technologies such as a concrete semi-submersible hull and a composite tower to reduce the costs of offshore wind. These novel characteristics require research and development prior to full-scale construction. This paper presents a unique offshore model testing effort aimed at de-risking full-scale commercial projects by providing properly scaled global motion data, allowing for implementation of full-scale structural materials, and demonstrating full-scale construction and deployment methods. The model is a 1:8-scale model of a 6MW semi-submersible floating wind turbine and was deployed offshore Castine, Maine, USA in June, 2013. The model uses a fully operational turbine and was the first grid connected offshore wind turbine in the Americas. The testing effort includes careful treatment of the offshore test site, scaling methods, model design, and construction. A suitable test site was identified that provides the correct proportions of wind and wave loading in order to simulate design load cases prescribed by the American Bureau of Shipping Standard for Building and Classing Floating Offshore Wind Turbines. Sample model test data is provided. Model test data is directly compared to full-scale design predictions made using coupled aeroelastic/ hydrodynamic software. VolturnUS performance data from scaled extreme sea states show excellent agreement with predictive models. Model test data are also compared to a numerical representation of the physical model for the purposes of numerical code validation. The numerical model results compare very favorably with data collected from the physical model.

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