Drilling Riser Model Tests for Software Verification

2016 ◽  
Author(s):  
Decao Yin ◽  
Halvor Lie ◽  
Massimiliano Russo ◽  
Guttorm Grytøyr
Keyword(s):  
Model Test ◽  
Software Verification ◽  
Cross Flow ◽  
Model Tests ◽  
Dynamic Responses ◽  
Wave Loads ◽  
Regular Wave ◽  
Marine Riser ◽  
Test Program ◽  
Irregular Wave

Marine drilling riser is subject to complicated environmental loads which include top motions due to Mobile Offshore Drilling Unit (MODU), wave loads and current loads. Cyclic dynamic loads will cause severe fatigue accumulation along the drilling riser system, especially at the subsea well head (WH). Statoil and BP have carried out a comprehensive model test program on drilling riser in MARINTEK’s Towing Tank in February 2015. The objective is to validate and verify software predictions of drilling riser behaviour under various environmental conditions by use of model test data. Six drilling riser configurations were tested, including different components such as Upper Flex Joint (UFJ), tensioner, marine riser, Lower Marine Riser Package (LMRP), Blow-Out Preventer (BOP), Lower Flex Joint (LFJ), buoyancy elements and seabed boundary model. The drilling riser models were tested in different load conditions: 1. Forced top motion tests 2. Regular wave test 3. Combined regular wave and towing test 4. Irregular wave test 5. Combined irregular wave and towing test 6. Towing test (VIV) Measurements were made of micro bending strains and accelerations along the riser in both In-Line (IL) and Cross-Flow (CF) directions. Video recordings were made both above and under water. In this paper, the test set-up and test program are presented. Comparisons of results between model test and RIFLEX simulation are presented on selected cases. Preliminary results show that the drilling riser model tests are able to capture the typical dynamic responses observed from field measurement, and the comparison between model test and RIFLEX simulation is promising.

Drilling Riser Model Test for Software Verification

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Decao Yin ◽  
Halvor Lie ◽  
Massimiliano Russo ◽  
Guttorm Grytøyr
Keyword(s):  
Model Test ◽  
Software Verification ◽  
Dynamic Responses ◽  
Wave Loads ◽  
Marine Riser ◽  
Test Program ◽  
Video Recordings ◽  
Severe Fatigue ◽  
Drilling Unit ◽  
Boundary Model

Marine drilling riser is subject to complicated environmental loads which include top motions due to mobile offshore drilling unit (MODU), wave loads, and current loads. Cyclic dynamic loads will cause severe fatigue accumulation along the drilling riser system, especially at the subsea wellhead (WH). Statoil and BP have carried out a comprehensive model test program on drilling riser in MARINTEK's Towing Tank in February 2015. The objective is to validate and verify software predictions of drilling riser behavior under various environmental conditions by the use of model test data. Six drilling riser configurations were tested, including different components such as upper flex joint (UFJ), tensioner, marine riser, lower marine riser package (LMRP), blow-out preventer (BOP), lower flex joint (LFJ), buoyancy elements, and seabed boundary model. The drilling riser models were tested in different load conditions. Measurements were made of microbending strains and accelerations along the riser in both in-line (IL) and crossflow (CF) directions. Video recordings were made both above and under water. In this paper, the test setup and test program are presented. Comparisons of results between model test and RIFLEX simulation are presented on selected cases. Preliminary results show that the drilling riser model tests are able to capture the typical dynamic responses observed from field measurement, and the comparison between model test and RIFLEX simulation is promising.

Model Tests of a Spar-Type Floating Wind Turbine Under Wind/Wave Loads

2015 ◽  
Author(s):  
Fei Duan ◽  
Zhiqiang Hu ◽  
Jin Wang
Keyword(s):  
Wind Turbine ◽  
Model Test ◽  
Wind Wave ◽  
Wave Model ◽  
Offshore Structures ◽  
Model Tests ◽  
Wave Loads ◽  
Scaled Model ◽  
Floating Wind Turbine ◽  
Wave Effects

Wind power has great potential because of its clean and renewable production compared to the traditional power. Most of the present researches for floating wind turbine rely on the hydro-aero-elastic-servo simulation codes and have not been exhaustively validated yet. Thus, model tests are needed and make sense for its high credibility to master the kinetic characters of floating offshore structures. The characters of kinetic responses of the spar-type wind turbine are investigated through model test research technique. This paper describes the methodology for wind/wave model test that carried out at Deepwater Offshore Basin in Shanghai Jiao Tong University at a scale of 1:50. A Spar-type floater was selected to support the wind turbine in this test and the model blade was geometrically scaled down from the original NREL 5 MW reference wind turbine blade. The detail of the scaled model of wind turbine and the floating supporter, the test set-up configuration, the mooring system, the high-quality wind generator that can create required homogeneous and low turbulence wind, and the instrumentations to capture loads, accelerations and 6 DOF motions are described in detail, respectively. The isolated wind/wave effects and the integrated wind-wave effects on the floating wind turbine are analyzed, according to the test results.

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.

Nonlinear Analysis of Vortex Induced Dynamic Response of Marine Riser

2013 ◽  
Vol 353-356 ◽  
pp. 2736-2740
Author(s):  
Lin Lin ◽  
Yan Ying Wang
Keyword(s):  
Dynamic Response ◽  
Cross Flow ◽  
Dynamic Responses ◽  
Marine Riser ◽  
Governing Equations ◽  
Nonlinear Dynamic Response ◽  
Wake Oscillator Model ◽  
Wake Oscillator ◽  
Flow Profiles ◽  
Line Force

Vortex-induced dynamic response is the most important issue influencing marine riser. This paper presents an investigation on the vortex-induced nonlinear dynamic response of marine riser subjected to combined waves,currents and platform movement. The in-line force was solved by Morison equation under combined waves,currents and platform movement while cross-flow force was solved by wake oscillator model. Updated Lagrangianmethod was used to solve the nonlinear problem.The governing equations were discretized by finite element method and solved by Newmark-β method in time domain. Influence of nonlinearity, comparisons of vortex-induced dynamic responses under different boundary conditions and different flow profiles were discussed.

Maneuvering Behavior of Ships in Irregular Waves

2013 ◽  
Author(s):  
Renato Skejic ◽  
Odd M. Faltinsen
Keyword(s):  
Deep Water ◽  
Cross Flow ◽  
Irregular Waves ◽  
Scale Model ◽  
Wave Loads ◽  
Ship Maneuvering ◽  
Slender Body Theory ◽  
Statistical Point ◽  
Irregular Wave ◽  
Mmg Model

Ship maneuvering in waves is analyzed by using a unified seakeeping and maneuvering two-time scale model in irregular sea that has been applied by Skejic and Faltinsen [1] for regular waves. The irregular wave effects are accounted for by Newman’s [2] approximation of the slow-drift 2nd order wave loads valid for deep water (Faltinsen [3], Pinkster [29]). The modular type maneuvering model (MMG model) based on Söding’s [4] nonlinear slender-body theory is used for the maneuvering analysis. Forces and moments due to rudder, propeller, and viscous cross-flow are accounted for as presented by Skejic and Faltinsen [1] and Yasukawa [5, 6]. In particular, the behavior of the propulsive coefficients (the thrust deduction and wake fraction) in waves (Faltinsen et al. [7], Faltinsen and Minsaas [8]) are discussed from the perspective of ship maneuvering characteristics in both regular and irregular wave environments. The unified model of seakeeping and maneuvering for deep-water irregular waves is validated for the ‘S7-175’ (‘SR 108’) container ship in calm water and regular deep-water wave scenarios by comparison with experimental results by Yasukawa [5, 6]. The maneuvering model is applied to a ‘MARINER’ ship performing turning maneuver in irregular waves. The obtained results of the ships main maneuvering parameters are discussed from a statistical point of view.

Green Water on FPSO Predicted by a Practical Engineering Method and Validated Against Model Test Data for Irregular Waves

2014 ◽  
Author(s):  
Rafael Vergara Schiller ◽  
Csaba Pâkozdi ◽  
Carl Trygve Stansberg ◽  
Douglas Gustavo Takashi Yuba ◽  
Daniel Fonseca de Carvalho e Silva
Keyword(s):  
Model Test ◽  
Model Tests ◽  
Irregular Waves ◽  
Green Water ◽  
Wave Impact ◽  
Irregular Wave ◽  
Beam Seas ◽  
Practical Engineering ◽  
The University ◽  
Wave Induced

This paper presents a series of numerical analyses performed with the potential theory-based Green Water engineer tool KINEMA3. KINEMA3 was designed to predict wave-induced impact loads on FPSOs in steep irregular waves, and for use in design load analysis. The purpose of the study presented herein is to validate KINEMA3 green water (deck overtopping) predictions in nonlinear irregular waves with results from model tests performed at the TPN (Tanque de Provas Numérico) laboratory at the University of São Paulo, Brazil. Comparisons are made for a selection of irregular wave cases, for two choices of anchoring conditions (free floating vessel and fixed vessel) and for three wave headings (180°, 225° and 270°: head, quartering and beam seas, respectively). KINEMA3 statistical green water predictions present a general good agreement with observations from the TPN model tests for all wave cases, headings and mooring conditions. Overall, observed trends for occurrence of green water and standard deviation/maximum of relative wave height are successfully reproduced by KINEMA3. In agreement with model test results, it is predicted that green water occurs more frequently for a free floating vessel and for beam seas. Additional comparisons between KINEMA3 predictions using different FPSO panel models (low-order and high-order models) present negligible differences with respect to green water estimates. The results presented herein demonstrate the robustness of the tool towards the prediction of green water for variable wave headings and sea states, and highlight the capability of KINEMA3 to be employed as an engineering-like tool for fast and multiple estimates of green water in early design studies. This work is a part of the research project “Green Water and Wave Impact on FPSO” carried out for and in cooperation with PETROBRAS.

scholarly journals Comprehensive Riser VIV Model Tests in Uniform and Sheared Flow

2012 ◽  
Author(s):  
Halvor Lie ◽  
Henning Braaten ◽  
Vikas Gopal Jhingran ◽  
Octavio E. Sequeiros ◽  
Kim Vandiver
Keyword(s):  
Cross Flow ◽  
Model Tests ◽  
Test Material ◽  
Test Program ◽  
Research Activity ◽  
Good Test ◽  
Vortex Induced Vibrations ◽  
Set Up ◽  
Oil Company ◽  
Made In

Despite of considerable research activity during the last decades considerable uncertainties still remain in prediction of Vortex Induced Vibrations (VIV) of risers. Model tests of risers subjected to current have been shown to be a useful method for investigation of the VIV behavior of risers with and without suppression devices. In order to get further insight on VIV of risers, an extensive hydrodynamic test program of riser models subjected to vortex-induced vibrations was undertaken during the winter 2010 by Shell Oil Company. The VIV-model test campaign was performed in the MARINTEK Offshore Basin Laboratory. A new test rig was constructed and showed to give good test conditions. Three different 38m long riser models were towed horizontally at different speeds, simulating uniform and linearly varying sheared current. Measurements were made In-Line (IL) and Cross-Flow (CF) of micro bending strains and accelerations along the risers. The test program compromised about 400 tests, which give a rich test material for further studies. In the present paper the test set-up and program are presented and selected results are reported.

scholarly journals Model Test of the STC Concept in Survival Modes

2014 ◽  
Author(s):  
Ling Wan ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Model Test ◽  
Extreme Conditions ◽  
Regular Wave ◽  
Wave Load ◽  
Large Wave ◽  
Irregular Wave ◽  
Floating Wind Turbine ◽  
The Mean ◽  
Wave Conditions

The STC (Spar Torus Combination) concept combines a Spar floating wind turbine and a torus-shaped heaving-body wave energy converter (WEC). Numerical simulation has shown positive synergy between the WEC and the Spar floating wind turbine in operational conditions. However, in extreme wind and wave conditions, it is challenging to maintain structural integrity, especially for the WEC. To ensure survivability of this concept in extreme conditions, three survival modes have been proposed. To investigate the performance of the STC in extreme conditions, model tests with a scale factor of 1:50 were carried out in the towing tank of MARINTEK, Norway. Two survival modes were tested. In both modes, the Torus WEC was fixed to the Spar. In the first mode, the Torus WEC is at the mean water surface, while in the second mode, the Torus WEC is fully submerged to a specified position. In the tests, 6 D.O.F rigid body motions, mooring line tensions, forces in 3 directions (X, Y and Z) between the Spar and Torus were measured, wind velocity and wind force were also measured by a sensor in front of the model and a load cell installed on the wind disc. In this paper, the model test set-up for the two survival modes are described, and then decay tests, regular wave tests and the statistical tests for wind only, irregular wave only and irregular wave plus wind are presented, compared and analyzed. In the mean water level survival mode, the Torus had a small draft and large water plane area, so slamming and green water were observed as expected. In addition, Mathieu instability phenomena were observed during the regular wave test. In some large wave conditions in the fully submerged mode, no severe wave load occurred. All the results are presented in model scale unless specified, for direct comparison with numerical simulations later.

The Slow Drift Oscillations of a Moored Object in Random Seas

1972 ◽  
Vol 12 (03) ◽  
pp. 191-198 ◽  
Author(s):  
G.F.M. Remery ◽  
A.J. Hermans
Keyword(s):  
Wave Train ◽  
Model Tests ◽  
Regular Wave ◽  
Regular Waves ◽  
Frequency Oscillation ◽  
Wave Groups ◽  
Irregular Wave ◽  
Random Seas ◽  
Head Waves ◽  
Constant Part

Abstract The phenomenon of the slowly varying drifting force on a mowed object in a random sea is explained and illustrated from the results of several model tests with a rectangular barge. These tests, conducted at the Netherlands Ship Model Basin, were an extension of an object executed program. Using the results of measured or calculated drifting forces on an object moored in regular waves, a prediction can be Made of the drifting forces induced by wave trains consisting of regular wave groups. Also, for an irregular wave train the drifting force on the barge can be computed as a function of time, which makes it possible to calculate the surge motion of the barge. The results of tests and calculations show a reasonable agreement. Introduction In the last few years the problems concerning the mooring of objects in random seas have gained much attention as a result of the necessity to load and discharge big tankers in open sea, or because the sea bottom has to be explored and exploited by vessels operating from the water surface. Generally a floating object moored in waves will be subjected to forces causing horizontal and vertical motions and to moments causing angular motions about the horizontal and vertical axes. Here we will deal with the horizontal surge motion of a rectangular barge moored by means of linear springs in head waves. The surge motion can be split up into a mean excursion, a slowly varying motion, and a higher frequency oscillation around the slowly varying position. The period of the higher frequency oscillation is equal to that of the wave motion; and since a considerable amount of literature is available concerning this part of the motion, it will not be treated in this paper. From the results of model tests in regular waves the mean drifting force on the barge could be determined as a function of the wave frequency. Using these data, the long-periodical surge motion of the barge was calculated for different stiffnesses of the mooring system for the condition in which the barge was moored in a wave train consisting of regular wave groups. The results of these calculations are compared with model test results. From these and earlier executed tests it is clear that resonance phenomena may occur when the period with which the wave groups encounter the barge equals the natural period of the surge motion of the moored barge. period of the surge motion of the moored barge. It also appears to be possible to calculate the drifting force induced by regular wave groups when such a wave train is taken to consist of two regular waves with a small difference in frequency. The regular wave groups, used for a clear demonstration of certain long-periodical phenomena, have mainly educational value. Regular wave groups will seldom occur. Generally the wave height changes irregularly. To estimate the drifting forces exerted on an object in a particular irregular wave train as a function of time, a method exists which produces reasonable results. This method, based on the principle of known drifting force in regular waves, principle of known drifting force in regular waves, will be dealt with. Starting from the obtained drifting force, the surge motion of the object moored in this particular wave train can be calculated. This is illustrated by comparison of some calculated surge motion records with those of measured ones. THE DRIFTING FORCE IN REGULAR WAVES The hydrodynamic forces on an object floating in regular waves may be resolved in an oscillatory part and in a constant part, of which the latter is part and in a constant part, of which the latter is known as the steady drifting force. Maruo shows that, for the two-dimensional case of an infinitely long cylinder floating in regular waves with its axis perpendicular to the wave direction, the steady drifting force Fd per unit length satisfies: Fd = 1/2 pga . SPEJ P. 191

CFD Reproduction of Model Test Generated Extreme Irregular Wave Events and Nonlinear Loads on a Vertical Column

2016 ◽  
Author(s):  
Csaba Pakozdi ◽  
Anders Östman ◽  
Erin E. Bachynski ◽  
Carl Trygve Stansberg
Keyword(s):  
Model Test ◽  
Vertical Cylinder ◽  
Control Signal ◽  
Test Case ◽  
Wave Loads ◽  
Reconstruction Procedure ◽  
Vertical Column ◽  
Irregular Wave ◽  
Wave Maker ◽  
The Waves

Recently, a method for numerical reproduction of measured irregular wave events has been developed. The measured motion of the wave maker flaps defines the wave kinematics at the boundary of the numerical simulation in order to generate the waves as described in (Pakozdi, Kendon, & Stansberg, 2011) and (Ostman, Pakozdi, Stansberg, Fagertun, & Vestbostad, 2015). When such data are not available, the control signal of the wave maker can, instead, be generated from a given free surface elevation following the same procedure as in model tests. Following this procedure automatically gives the possibility to subsequently reproduce the numerical wave experimentally using the obtained control signal. The latter procedure is applied to a model test case with extreme irregular wave events and resulting nonlinear global wave loads on a vertical cylinder (Stansberg, 1997), with the focus on higher-order ringing excitation. The purpose of the investigation is two-fold: 1) to validate the wave reconstruction procedure, and 2) to validate the resulting CFD ringing loads with the given waves. The results show generally good agreement both in the waves and in the loads; discrepancies found in the loads are considered to be mainly originating from corresponding uncertainties in the wave reconstruction. Wave breaking may be one source of uncertainty.

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