Comparison Between Numerical Prediction and Model Tests Measurements on the Centerwell Tank of a Radial Wellbay Spar

2012 ◽  
Author(s):  
Edmund Muehlner ◽  
John Murray ◽  
Surya Banumurthy ◽  
Chandan Lakhotia
Keyword(s):  
Time Domain ◽  
Accurate Estimate ◽  
Model Tests ◽  
Scale Model ◽  
Inertia Effect ◽  
Primary Difference ◽  
Truss Spar ◽  
Interior Walls ◽  
Six Degree Of Freedom ◽  
Semi Empirical

The radial wellbay (RAW) Spar is, for the most part, based on conventional Truss Spar technology. The primary difference between the RAW Spar and the conventional Truss Spar is the wellbay arrangement. An integral structural component of the RAW Spar is the ABCD (Adjustable Buoyancy Centerwell Device) located in the lower portion of the centerwell. The ABCD is connected to the interior of the hard tank using a number of shear plates. The ABCD captures the buoyancy in the open centerwell and contributes to the total buoyancy of the hard tank. As an option, the ABCD can be used for in-hull storage. On the RAW drilling Spar, the ABCD can be used to support the setback and pipe racking system. Design applications using the ABCD raise an additional requirement in the design of the hard tank, specifically, an accurate estimate of the load in the structure that connects the ABCD to the hard tank. Contributions to this load come from the inertia effect of the Spar motions, hydrostatic responses affected by ballast conditions in the device, and hydrodynamic forces affected by pressure in the riser slot gap. Connection loads are required to design the structure connecting the ABCD to the interior walls of the hard tank. An ABAQUS™ based time domain semi-empirical model was developed to predict the local and global loads on the ABCD. A series of 1:50 scale model tests on the RAW Spar were carried out at the OTRC basin in College Station, Texas. The model’s ABCD, mounted on a dynamometer system inside the hard tank, was used to measure the six-degree-of-freedom forces between the hard tank and the ABCD. The paper focuses on a comparison of the predicted and measured loads.

Analysis of the Tunnel Immersion for the Busan-Geoje Fixed Link Project Through Scale Model Tests and Computer Simulations

2009 ◽  
Author(s):  
Hans Cozijn ◽  
Jin Wook Heo
Keyword(s):  
Simulation Model ◽  
Computer Simulations ◽  
Time Domain ◽  
Extreme Values ◽  
Sensitivity Study ◽  
Model Tests ◽  
Direct Access ◽  
Scale Model ◽  
Mooring System ◽  
Sea Bed

In Korea a four lane motorway is constructed between the city of Busan and the island Geoje, reducing traveling times from 1 hour by ferry to just 10 minutes by car. The so-called Busan-Geoje Fixed Link consists of 2 cable-stayed girder bridges and a tunnel, crossing the bay of Jinhae. The submerged tunnel is built by transporting each of its 18 elements below 2 pontoons from a construction dock to their final positions and lowering them on the sea bed. The project is unique, because the tunnel elements are installed in a bay with direct access towards open sea. For this reason, the effects of incoming swells and wind seas were investigated in detail, so that the operational limits of the tunnel element immersion could be accurately determined. This was achieved by using an approach of combined hydrodynamic scale model tests and time-domain computer simulations. First, scale model tests were carried out in MARIN’s Shallow Water Basin. A detailed test set-up was constructed, including the trench in which the tunnel elements are placed, as is shown in the photograph. Models of a tunnel element, two pontoons, the mooring system, contraction lines and suspension wires were constructed at a scale of 1:50. The motions of the pontoons and the submerged tunnel element, as well as the tensions in the lines, were measured in a range of different wave conditions. Different stages of the tunnel immersion were investigated. Second, a simulation model of the pontoons and tunnel element was constructed in MARIN’s time-domain simulation tool aNySIM. The large number of mooring lines, contraction lines and suspension wires resulted in a relatively complex numerical model. The simulation model was calibrated such that the results from the model tests could be accurately reproduced. Subsequently, a sensitivity study was carried out, investigating the parameters most critical to the operation and the mooring system of the pontoons was further optimized. Finally, the operational limits of the tunnel immersion were evaluated by carrying out more than 6,500 time-domain simulations, investigating a large number of different combinations of wind sea and swell. The simulation results included motions, velocities and accelerations, as well as line tensions. The extreme values were used to perform a combined evaluation of more than 10 structural and operational criteria. The photograph below (copyright Peter de Haas, Royal Haskoning) shows the immersion of the first of 18 tunnel elements in the bay of Jinhae, in February 2008.

scholarly journals Design and Calibration of a Hall Effect System for Measurement of Six-Degree-of-Freedom Motion within a Stacked Column

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3740
Author(s):  
Olafur Oddbjornsson ◽  
Panos Kloukinas ◽  
Tansu Gokce ◽  
Kate Bourne ◽  
Tony Horseman ◽  
...  
Keyword(s):  
Hall Effect ◽  
Degrees Of Freedom ◽  
Reactor Core ◽  
Degree Of Freedom ◽  
Life Extension ◽  
Scale Model ◽  
Design Development ◽  
Seismic Safety ◽  
Six Degrees Of Freedom ◽  
Six Degree Of Freedom

This paper presents the design, development and evaluation of a unique non-contact instrumentation system that can accurately measure the interface displacement between two rigid components in six degrees of freedom. The system was developed to allow measurement of the relative displacements between interfaces within a stacked column of brick-like components, with an accuracy of 0.05 mm and 0.1 degrees. The columns comprised up to 14 components, with each component being a scale model of a graphite brick within an Advanced Gas-cooled Reactor core. A set of 585 of these columns makes up the Multi Layer Array, which was designed to investigate the response of the reactor core to seismic inputs, with excitation levels up to 1 g from 0 to 100 Hz. The nature of the application required a compact and robust design capable of accurately recording fully coupled motion in all six degrees of freedom during dynamic testing. The novel design implemented 12 Hall effect sensors with a calibration procedure based on system identification techniques. The measurement uncertainty was ±0.050 mm for displacement and ±0.052 degrees for rotation, and the system can tolerate loss of data from two sensors with the uncertainly increasing to only 0.061 mm in translation and 0.088 degrees in rotation. The system has been deployed in a research programme that has enabled EDF to present seismic safety cases to the Office for Nuclear Regulation, resulting in life extension approvals for several reactors. The measurement system developed could be readily applied to other situations where the imposed level of stress at the interface causes negligible material strain, and accurate non-contact six-degree-of-freedom interface measurement is required.

scholarly journals EXTREME WAVE PRESSURES AND LOADS ON A PILE-SUPPORTED WHARF DECK - INFLUENCES OF AIR GAP AND WAVE DIRECTION

2018 ◽  
pp. 5
Author(s):  
Andrew Cornett
Keyword(s):  
Offshore Structures ◽  
Model Tests ◽  
Scale Model ◽  
Extreme Waves ◽  
Wave Direction ◽  
Coastal Structures ◽  
Extreme Wave ◽  
Wave Impact ◽  
The Past ◽  
Water Depths

Many deck-on-pile structures are located in shallow water depths at elevations low enough to be inundated by large waves during intense storms or tsunami. Many researchers have studied wave-in-deck loads over the past decade using a variety of theoretical, experimental, and numerical methods. Wave-in-deck loads on various pile supported coastal structures such as jetties, piers, wharves and bridges have been studied by Tirindelli et al. (2003), Cuomo et al. (2007, 2009), Murali et al. (2009), and Meng et al. (2010). All these authors analyzed data from scale model tests to investigate the pressures and loads on beam and deck elements subject to wave impact under various conditions. Wavein- deck loads on fixed offshore structures have been studied by Murray et al. (1997), Finnigan et al. (1997), Bea et al. (1999, 2001), Baarholm et al. (2004, 2009), and Raaij et al. (2007). These authors have studied both simplified and realistic deck structures using a mixture of theoretical analysis and model tests. Other researchers, including Kendon et al. (2010), Schellin et al. (2009), Lande et al. (2011) and Wemmenhove et al. (2011) have demonstrated that various CFD methods can be used to simulate the interaction of extreme waves with both simple and more realistic deck structures, and predict wave-in-deck pressures and loads.

Large scale model tests on Royal Schelde SES

1989 ◽  
Author(s):  
R. DE GAAIJ ◽  
E. VAN RIETBERGEN ◽  
M. SLEGERS
Keyword(s):  
Large Scale ◽  
Model Tests ◽  
Scale Model ◽  
Large Scale Model

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.

Application of a General Technique for Prediction of Riser Vortex-Induced Response in Waves and Current

1989 ◽  
Vol 111 (2) ◽  
pp. 82-91 ◽  
Author(s):  
G. J. Lyons ◽  
M. H. Patel
Keyword(s):  
Time Domain ◽  
Calculation Method ◽  
Prediction Method ◽  
Induced Response ◽  
Flow Properties ◽  
General Technique ◽  
Prediction Technique ◽  
Combined Action ◽  
Semi Empirical ◽  
Surface Vessel

This paper describes applications of an extension to a recently developed calculation method for vortex-induced response of risers and tethers. The vortex-induced vibration response for the excited modes is generated using a semi-empirical formulation which is applied within a time domain calculation. This makes it possible to take account of the variation of flow properties along the riser length, as well as in time. The calculation method has been verified by comparison with model test data for vortex-induced response to surface vessel motions in still water. This paper presents applications of the technique for vortex shedding due to the combined action of current, surface vessel motions and waves. The mathematics of the extended prediction technique is described and results are illustrated by presenting typical vortex-induced responses for single-tube risers. The results of the prediction method are used to highlight the relative magnitudes and nature of vortex-induced response excited by currents, surface vessel motions and waves.

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