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.

Full-Scale Model Test for Anchorage Zone of Pylon of Cable-Stayed Bridge

2012 ◽  
Vol 238 ◽  
pp. 728-732
Author(s):  
Xiao Lin Yu ◽  
Bu Yu Jia ◽  
Wei Feng Wang ◽  
Quan Sheng Yan
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Full Scale ◽  
Scale Model ◽  
Deformation Condition ◽  
Zone Model ◽  
Construction Technology ◽  
Test Results ◽  
Cable Stayed Bridge ◽  
Cable Force

In this paper, the construction technology for main pylon of cable-stayed bridge is researched through test of full-scale model of anchorage zone of pylon of Guangzhou Bridge. Stress distribution and deformation condition of model under prestressed tendons and cable force are analyzed. Numerical simulation on this anchorage zone model is carried out. By comparing FEM results to the test results, some important conclusions are drawn out and give some advices to the optimum design of the bridge pylon. Parts of the achievements have been applied to actual bridge work and obtained successful engineering experience.

The Effect of Mooring System and Sheared Currents on Vortex Induced Motions of Truss Spars

2003 ◽  
Author(s):  
Radboud R. T. van Dijk ◽  
Arjan Voogt ◽  
Paul Fourchy ◽  
Saadat Mirza
Keyword(s):  
Gulf Of Mexico ◽  
Mooring System ◽  
Test Results ◽  
Current Profile ◽  
Scaled Model ◽  
Production Platform ◽  
Helical Strakes ◽  
Truss Spar ◽  
Set Up ◽  
Program Show

Since 1996 Spars have been used as production platform in the Gulf of Mexico. Spar Vortex Induced Motions (VIM) in strong currents like the hurricane and loop currents are an important consideration for the design of the mooring system and risers. This is important for the extreme offsets as well as fatigue in risers and the mooring system. This paper compares the VIM behavior of a truss Spar in sheared currents, like the Hurricane current in the Gulf of Mexico, with tow test results. Experiments have been carried out on a scaled model in both a complete mooring system and in a towing set-up with a simplified horizontal mooring. The Spar model consists of a hard tank with removable helical strakes, a truss section and a square soft tank. The results of this model test program show that both the choice of the mooring system and current profile have a significant influence on the VIM response of the Spar. The paper discusses the results of this research and also addresses important issues and considerations for VIM model tests.

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.

Study on Safety of the Fastener Tubular Steel Scaffolding

2011 ◽  
Vol 368-373 ◽  
pp. 771-776 ◽  
Author(s):  
Chang Ming Hu ◽  
Fang Fang Song ◽  
Xiao Zhou Fan
Keyword(s):  
Finite Element ◽  
Initial Imperfection ◽  
Full Scale ◽  
Scale Model ◽  
Test Results ◽  
Lateral Loads ◽  
Safety Control ◽  
Research Results ◽  
Initial Imperfections ◽  
Finite Element Software

Based on analysis of five different conditions’ full scale model tests of the fastener tubular steel scaffolding, the paper introduces that notional lateral loads can imitate the effect which generalized imperfections of the falsework(initial imperfections, node semi-rigid and so on) give the bracket’s stability capacity. According to the finite element software ANSYS, the falseworks’ stability capacities of different conditions have been imitated and analysed, Analysis results compare with test results. The final result indicates that it is reasonable that notional lateral loads in certain scope can imitate generalized initial imperfection. Research results can be used for on-site t technical personnels’ design and safety control.

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.

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

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.

CFD Simulation of Truss Spar Vortex-Induced Motion

2006 ◽  
Author(s):  
Sampath Atluri ◽  
John Halkyard ◽  
Senu Sirnivas
Keyword(s):  
Cfd Simulation ◽  
Turbulence Modeling ◽  
General Purpose ◽  
Scale Model ◽  
Cfd Simulations ◽  
Model Experiments ◽  
Helical Strakes ◽  
Induced Motion ◽  
Truss Spar ◽  
Hydrodynamic Effects

Helical strakes are used to suppress the Vortex-Induced Motion of Truss Spars. Model experiments have demonstrated the efficiency of strakes in the Truss Spar design but also indicate that the VIM response is sensitive to the details of strake design and placement of appurtenances around the Spar hull. It is desirable to study these hydrodynamic effects using CFD. The following paper is a continuation of some of the earlier CFD simulations on this subject (see, J. Halkyard, et al., “Benchmarking of Truss Spar Vortex-Induced Motions Derived from CFD with Experiments”, Proceedings of OMAE’05). This paper in particular deals with the effect of holes in the strakes and appurtenances and their placement. All the simulations were done at model scale (1:40 scale model of an actual Truss Spar design) to compare the motions with experimental results. Mesh sensitivity and turbulence modeling issues are also discussed. Calculations were done using general purpose CFD code Acusolve™.

Model Mobile Load Simulator Testing at National Center for Asphalt Technology Test Track

2003 ◽  
Vol 1832 (1) ◽  
pp. 182-190 ◽  
Author(s):  
André de Fortier Smit ◽  
Fred Hugo ◽  
Dale Rand ◽  
Buzz Powell
Keyword(s):  
Full Scale ◽  
Scale Model ◽  
Climatic Data ◽  
Test Results ◽  
Test Track ◽  
Wheel Tracking Test ◽  
Load Simulator ◽  
Wheel Tracking ◽  
Prediction Approach ◽  
Semicircular Bending

One-third-scale model mobile load simulator (MMLS3) testing was conducted at the National Center for Asphalt Technology test track. Dry and wet-heated MMLS3 tests were done on five sections. The rutting performances of the sections under MMLS3 trafficking were compared with that under full-scale truck trafficking (truck test sections). A synthesis of the research included evaluation of results from laboratory tests done on cores taken from the MMLS3 test sections within and outside trafficked wheelpaths. Tests on the cores included wet and dry Hamburg wheel tracking, Superpave® shear tester frequency sweep, and semicircular bending (SCB) strength testing. Investigations included the evaluation of full-scale rutting data, laboratory wheel-tracking test results, and climatic data monitored on the track during full-scale truck trafficking. The project validated the rut prediction approach developed to compare MMLS3 and full-scale rutting performance and indicated that the MMLS3 may be used to estimate full-scale rutting at the track under specific conditions. Distress due to wet trafficking was also quantified as reduction in tensile strength as measured by the SCB. Conclusions were drawn and recommendations made for MMLS3 as well as continued full-scale testing at the track. Comparative full-scale rutting performance of the track sections evaluated may be quantified and ranked by the MMLS3 performance of these sections.

Suppressing Full-Scale Riser VIV With the VT Suppressor

2013 ◽  
Author(s):  
Roger King ◽  
Andrew Brown ◽  
Henning Braaten ◽  
Massimiliano Russo ◽  
Rolf Baarholm ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Experimental Tests ◽  
Reynolds Numbers ◽  
Full Scale ◽  
Test Results ◽  
Cylindrical Structures ◽  
Novel Device ◽  
Critical Reynolds Numbers ◽  
Viv Suppression ◽  
Special Arrangement

The paper reports on recent full scale experimental tests with The Ventilated Trouser (VT), a novel device for VIV suppression of cylindrical structures exposed to external fluid flow. The VT suppressor is a loose fitting sleeve in the form of a light flexible net with integral bobbins in a special arrangement (Fig 1). It is omni-directional, rugged, and made from materials compatible with the offshore environment. The tests reported here, originated in an invitation from Statoil to test the VT on a slick riser section. They were undertaken at Marintek, Norway, with a 0.53m diameter riser in current velocities up to 2.3m/s, equivalent to post-Critical Reynolds Numbers of up to 1.2 × 106. The VT suppressed the maximum VIV amplitude of the slick joint by over 90%. This was consistent with the suppression performance of the VT from previous tests with model risers varying in size from 0.1m diameter to 0.3m diameter. The test results suggest the VT is a candidate suppressor fully capable of competing with conventional suppression devices.

Sign in / Sign up

Export Citation Format

Share Document