Model Testing for Vortex Induced Motions of Spar Platforms

2004 ◽  
Author(s):  
Mehernosh Irani ◽  
Lyle Finn
Keyword(s):  
Gulf Of Mexico ◽  
Model Test ◽  
State Of The Art ◽  
Model Testing ◽  
Model Tests ◽  
The State ◽  
Test Results ◽  
Test Set ◽  
Vortex Induced Vibrations ◽  
Set Up

The state-of-the art in model testing for Vortex Induced Vibrations (VIV) of Spars is presented. Important issues related to Spar VIV model testing are highlighted. The parameters that need to be modeled including hull geometry, strake configuration, mass and mooring properties and, considerations of test set-up and instrumentation are discussed. Results are presented from model tests of an as-built Spar deployed in the Gulf of Mexico. It is shown that the model test results compare well with the VIV responses measured in the field.

Improved Strake Design for Vortex Induced Motions of Spar Platforms

2005 ◽  
Author(s):  
Mehernosh Irani ◽  
Lyle Finn
Keyword(s):  
Model Test ◽  
Model Tests ◽  
Test Results ◽  
Test Program ◽  
Test Set ◽  
Test Methodology ◽  
Spar Platforms ◽  
Truss Spar ◽  
Set Up

An extensive model test program was conducted to explore the effectiveness of alternate strake designs to reduce Truss Spar VIV response. Different strake configurations were tested to minimize VIV response. The paper presents results of the model tests. The model test set-up is described, important parameters that are modeled (including hull and truss geometry, strake configuration, mass and mooring properties) and considerations of instrumentation and test methodology are discussed. The paper also describes the analysis of the test results and shows the effectiveness of new strake design. The present results are compared with VIV response of existing Truss Spars with conventional strake design.

A Novel Passive Riser Tensioning System for a Dry Tree Spread Moored Barge

2004 ◽  
Author(s):  
Amit Katarya
Keyword(s):  
Model Test ◽  
Vertical Motion ◽  
Model Tests ◽  
Test Results ◽  
Test Set ◽  
Payload Capacity ◽  
Set Up ◽  
Floating Systems ◽  
Moon Pool ◽  
Fully Coupled

Dry tree risers on floating systems are presently supported either by TLPs or SPARs, both of which have limited payload capacity and no storage. A spread-moored barge having dry trees, storage and integrated drilling facilities has been developed. Model tests were performed for the riser tensioning system used on such a barge for offshore West Africa conditions. The risers are attached to a rectangular platform in a moon pool of the barge. This platform is supported by means of an articulated Rocker Arm System (RAS) located on the vessel main deck. The RAS has built-in counter weights hinged on pedestals fixed to the barge deck. In this arrangement gravity is used to tension the risers and when the barge heaves, the counterweights in the rocker arm system essentially decouple the barge vertical motion from the riser platform. This system provides a heave-restrained platform for dry trees with minimal dynamic loading of the risers. The model tests confirmed the feasibility of the new design. The paper describes the basic components of the gravity tensioning system. The model test set up and results from the model test are shown. Comparison of model test results with a fully coupled analytic model consisting of the barge and articulated tensioning system is also presented.

Model Test Data Correlations With Fully Coupled Hull/Mooring Analysis for a Floating Wind Turbine on a Semi-Submersible Platform

2014 ◽  
Author(s):  
Bonjun Koo ◽  
Andrew J. Goupee ◽  
Kostas Lambrakos ◽  
Ho-Joon Lim
Keyword(s):  
Wind Turbine ◽  
Model Test ◽  
Model Tests ◽  
Test Results ◽  
Scaled Model ◽  
Floating Wind Turbine ◽  
Mooring Dynamics ◽  
Set Up ◽  
Fully Coupled ◽  
Turbine Model

The DeepCwind floating wind turbine model tests were performed at MARIN (Maritime Research Institute Netherlands) with a model set-up corresponding to a 1:50 Froude scaling. In the model tests, the wind turbine was a scaled model of the National Renewable Energy Lab (NREL) 5MW, horizontal axis reference wind turbine supported by three different generic floating platforms: a spar, a semi-submersible and a tension-leg platform (TLP) (Ref. [1] and [2]). This paper presents validation of the MLTSIM-FAST [3] code with DeepCwind semi-submersible wind turbine model test results. In this integrated program, the turbine tower and rotor dynamics are simulated by the subroutines of FAST [4], and the hydrodynamic loads and mooring system dynamics are simulated by the subroutines of MLTSIM. In this study, fully coupled hull/mooring dynamics and second-order difference-frequency response are included in MLTSIM-FAST. The analysis results are systematically compared with model test results and show good agreement.

Development and Verification of Modeling Practice for CFD Decay Calculations to Obtain Roll Damping of FPSO

2021 ◽  
Author(s):  
Arjen Koop ◽  
Pierre Crepier ◽  
Sebastien Loubeyre ◽  
Corentin Dobral ◽  
Kai Yu ◽  
...  
Keyword(s):  
Model Test ◽  
Test Results ◽  
Cfd Modelling ◽  
Roll Damping ◽  
Natural Period ◽  
Computational Mesh ◽  
Safety Studies ◽  
Offshore Industry ◽  
Decay Tests ◽  
Set Up

Abstract Estimates for roll damping are important input parameters for simulation studies on vessels operating at sea, e.g. FPSO mooring in waves, wind and current, workability and operability investigations, Dynamic Position studies, ship-to-ship operations and safety studies of vessels. To accurately predict the motions of vessels this quantity should be determined with confidence in the values. Traditionally, model experiments in water basins using so-called decay tests are carried out to determine the roll damping. With recent advancements in CFD modelling, the offshore industry has started using CFD as an alternative tool to compute the roll damping of FPSO’s. In order to help adopt CFD as a widely accepted tool, there is a need to develop confidence in CFD predictions. Therefore, a practical CFD modelling practice is developed within the Reproducible CFD JIP for roll decay CFD simulations. The Modelling Practice describes the geometry modelling, computational mesh, model set-up and post-processing for these type of CFD calculations. This modelling practice is verified and validated by three independent verifiers against available model test data. This paper provides an overview of the developed modelling practice and the calculated CFD results from the verifiers. The CFD modelling practice is benchmarked against available model test results for a tanker-shaped FPSO. By following this modelling practice, the CFD predictions for the equivalent linear damping coefficient and natural period of the roll motions are within 10% for all verifiers and within 10% from the model test results. Therefore, we conclude that when following the developed modelling practice for roll decay simulations, reliable, accurate and reproducible results can be obtained for the roll damping of tanker-shaped FPSOs.

scholarly journals AI Feynman: A physics-inspired method for symbolic regression

2020 ◽  
Vol 6 (16) ◽  
pp. eaay2631 ◽  
Author(s):  
Silviu-Marian Udrescu ◽  
Max Tegmark
Keyword(s):  
Neural Network ◽  
Artificial Intelligence ◽  
Success Rate ◽  
Unknown Function ◽  
State Of The Art ◽  
Practical Interest ◽  
Symbolic Regression ◽  
The State ◽  
Np Hard ◽  
Test Set

A core challenge for both physics and artificial intelligence (AI) is symbolic regression: finding a symbolic expression that matches data from an unknown function. Although this problem is likely to be NP-hard in principle, functions of practical interest often exhibit symmetries, separability, compositionality, and other simplifying properties. In this spirit, we develop a recursive multidimensional symbolic regression algorithm that combines neural network fitting with a suite of physics-inspired techniques. We apply it to 100 equations from the Feynman Lectures on Physics, and it discovers all of them, while previous publicly available software cracks only 71; for a more difficult physics-based test set, we improve the state-of-the-art success rate from 15 to 90%.

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.

Motion Comparison Between a Conventional Deep Draft Semi-Submersible and a Dry Tree Semi-Submersible

2009 ◽  
Author(s):  
Anis Hussain ◽  
Edwin Nah ◽  
Rain Fu ◽  
Apurva Gupta
Keyword(s):  
Gulf Of Mexico ◽  
Model Test ◽  
Significant Influence ◽  
Extreme Environments ◽  
Test Results ◽  
Numerical Computations ◽  
Deep Waters ◽  
Second Tier ◽  
Motion Characteristics ◽  
Heave Motion

One of the major requirements for a floating vessel designed to support top tensioned risers is to have the heave response within a minimum specified range in extreme environments. The heave has a significant influence on the riser stroke. Usually floater designs aim to use conventional riser tensioners, available commercially, which typically have a maximum stroke range in the order of 30 to 35ft. One of the limitations of traditional Semi-submersible designs to support dry trees is that the heave ranges seen in central Gulf of Mexico (GoM) are outside the range that can apply a conventional tensioner. The Extendable Semi-submersible (E-Semi) utilizes a retractable Second Tier Pontoon (STP) to suppress heave motions and reduce its heave motion in order to support top tensioned risers in central GoM ultra deep waters. The design is based on an established deep draft Semi-submersible with the STP attached. This paper presents a comparison between motion characteristics of the deep draft Semi-submersible with and without the STP attached. The comparison is based on numerical computations to predict the responses together with model test results in the same environments. The analysis essentially shows the effectiveness of the STP is suppressing the heave motion.

Field Trial of Vortex-Induced Vibration Suppression Technology for Drilling Riser Buoyancy

2019 ◽  
Author(s):  
Phillip P. Kurts ◽  
Hayden Marcollo ◽  
Andrew A. Kilner ◽  
Daniel Johnstone ◽  
Andrew E. Potts ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Eddy Current ◽  
Field Trial ◽  
Field Trials ◽  
Model Tests ◽  
Scale Model ◽  
Base Case ◽  
Test Results ◽  
Hydrodynamic Parameters ◽  
Viv Suppression

Abstract Instrumented field trials of Longitudinally Grooved Suppression (LGS) VIV suppression buoyancy modules have been completed on deep water drilling risers in the Gulf of Mexico. The field trials were used to validate the performance of the technology, which had previously been evaluated using prototype scale model tests. The measured riser responses over two drilling campaigns spanning more than six months were compared with each other and the outputs of computational riser modeling to validate the hydrodynamic parameter set derived through scale model tests and provide validated assessments of the suppression technology performance. The measured response of drilling risers equipped with LGS buoyancy has been compared with a publicly available dataset for the VIV response of a conventionally buoyed riser, showing reduced VIV response in agreement with model test results. Measured flex joint angles, current profiles and riser accelerations were used to validate the hydrodynamic parameters used in numerical riser analysis. Using the validated hydrodynamic parameters, the VIV and drag suppression performance was demonstrated by comparison with the model predictions for risers equipped with conventional buoyancy modules. Eddy current occurrence statistics for a location in the Gulf of Mexico were used to calculate the expected annual operability performance for both configurations. For the base case parameters, 12 days of annual operability improvement was predicted when using LGS buoyancy modules. A sensitivity study determined the effect of varying analysis assumptions on the predicted operability improvements. Measured current data from 2014 was also used to determine the operability benefits which could be realized within a year in which severe eddy current activity occurred. The analysis performed serves to validate the previous laboratory tests as well as answer questions about the applicability of high Reynolds Number test results to VIV suppression devices in the field. The use of previously validated testing and analysis methods is shown to provide reliable estimates of suppression technology performance which are borne out by testing in the field. This paper presents the first published field trial of shaped buoyancy type VIV suppression, a group of technologies which have until now only been demonstrated using scale model tests and Computational Fluid Dynamics simulations.

scholarly journals Seeking for the Maximum Symmetric Rank

Mathematics ◽  
2018 ◽  
Vol 6 (11) ◽  
pp. 247 ◽  
Author(s):  
Alessandro De Paris
Keyword(s):  
State Of The Art ◽  
Symmetric Tensor ◽  
Upper Bounds ◽  
The State ◽  
Tensor Rank ◽  
Symmetric Tensors ◽  
Lower And Upper Bounds ◽  
Symmetric Tensor Rank ◽  
Set Up ◽  
Divided Powers

We present the state-of-the-art on maximum symmetric tensor rank, for each given dimension and order. After a general discussion on the interplay between symmetric tensors, polynomials and divided powers, we introduce the technical environment and the methods that have been set up in recent times to find new lower and upper bounds.

scholarly journals METHODOLOGY FOR NON-DESTRUCTIVE IDENTIFICATION OF THICKNESS OF UNILATERALLY ACCESSIBLE CONCRETE ELEMENTS BY MEANS OF STATE-OF-THE-ART ACOUSTIC TECHNIQUES

2013 ◽  
Vol 19 (3) ◽  
pp. 325-334 ◽  
Author(s):  
Krzysztof Schabowicz
Keyword(s):  
Heat Pipe ◽  
State Of The Art ◽  
The State ◽  
Ultrasonic Tomography ◽  
Test Results ◽  
Impact Echo ◽  
Acoustic Techniques ◽  
Concrete Shell ◽  
Concrete Elements ◽  
Non Destructive

The paper presents a methodology for comprehensive use of ultrasonic tomography and impact-echo – the state-of-the-art acoustic techniques – for non-destructive identification of the thickness of unilaterally accessible concrete elements. Since the techniques are not commonly used, they are little known. Therefore, a brief description of the techniques is given to facilitate the understanding of the subsequently presented methodology. The article gives a practical example of the use of the methodology, which demonstrates its suitability for non-destructive identification of the thickness of concrete elements, particularly those only accessible from one side. In the example, the concrete shell of a heat pipe, carrying tunnel located under a river was tested using the ultrasonic tomography and impact-echo techniques. The tests were carried out according to the proposed methodology. It should be noted that the test results yielded by the two methods were similar. In this way, the proposed methodology has been validated.

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