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.

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.

Tandem Riser Hydrodynamic Tests at Prototype Reynolds Number

2013 ◽  
Author(s):  
Yiannis Constantinides ◽  
Kamaldev Raghavan ◽  
Metin Karayaka ◽  
Don Spencer
Keyword(s):  
Reynolds Number ◽  
Theoretical Models ◽  
Reynolds Numbers ◽  
Full Scale ◽  
Experimental Methodology ◽  
Small Scale ◽  
Hydrodynamic Coefficients ◽  
Cylinder Wake ◽  
Standard Models ◽  
Viv Suppression

Deepwater riser interference is an area of significant technical complexity and uncertainty in the design cycle due to the intricacies of wake hydrodynamics. Existing models, found in industry guidelines, are based on approximate theoretical models of bare cylinder wake and nominally checked against small scale tests at low Reynolds numbers. In actual conditions the Reynolds number is sufficiently higher and the risers are fitted with vortex-induced vibration (VIV) suppression devices. This raises questions on the applicability of the standard models and hydrodynamic coefficients used, especially if the geometry is different than a circular cylinder. A series of full scale tests, at supercritical Reynolds numbers, were conducted to address these uncertainties and obtain hydrodynamic coefficients for interference design. The tests were carried out utilizing two full scale cylinders fitted with actual VIV suppression devices and towed either in fixed or spring supported configurations. The paper discusses the experimental methodology and findings from the testing program, showing deviations from the standard models found in industry codes.

scholarly journals Behavior of Strengthened Composite Prestressed Concrete Girders under Static and Repeated Loading

2017 ◽  
Vol 2017 ◽  
pp. 1-13
Author(s):  
Abbas AbdulMajeed Allawi
Keyword(s):  
Prestressed Concrete ◽  
Experimental Tests ◽  
Full Scale ◽  
Repeated Loading ◽  
Test Results ◽  
Concrete Girders ◽  
Load Carrying ◽  
Prestressed Concrete Girders ◽  
Aashto Lrfd ◽  
Analysis Models

The use of external posttensioning technique for strengthening reinforced concrete girders has been considerably studied by many researchers worldwide. However, no available data are seen regarding strengthening full-scale composite prestressed concrete girders with external posttensioned technique under static and repeated loading. In this research, four full-scale composite prestressed I-shape girders of 16 m span were fabricated and tested under static and repeated loading up to failure. Accordingly, two girders were externally strengthened with posttensioned strands, while the other two girders were left without strengthening. The experimental tests include deflection, cracking load, ultimate strength and strains at midspan, and loading stages. Test results were compared with the design expressions mentioned in AASHTO LRFD specifications and ACI 318-2014 code. Also, a nonlinear analysis was conducted using the finite element method (FEM). The presented analysis models were verified by comparing the model results with test results. The general theme abstracted from both experimental tests and numerical analysis reflects that the performance and procedure of strengthening with external prestressing of girders were found to be effective in increasing the load carrying capacity of the strengthened girders.

Comparison of mixed liquor filterability measured with bench and pilot-scale membrane bioreactors

2007 ◽  
Vol 56 (6) ◽  
pp. 155-162 ◽  
Author(s):  
J.P. Nywening ◽  
H. Zhou ◽  
H. Husain
Keyword(s):  
Experimental Tests ◽  
Pilot Scale ◽  
Membrane Bioreactors ◽  
Full Scale ◽  
Test Results ◽  
Critical Flux ◽  
Mixed Liquor ◽  
Module Design ◽  
Side Stream ◽  
Dead End

Parallel experimental tests to measure mixed liquor filterability for submerged membrane bioreactors were conducted over a six month period using three ZW-500 pilot plants and a ZW-10 lab-scale filterability apparatus. Non-air sparged conditions during the tests yielded operation behaviour that was equivalent to dead-end filtration. The fouling resistance increased linearly with the intercepted mass until a critical point was reached at which point significant cake compression was induced and the resistance began to increase exponentially. Although the point of cake compression appears to be dependent on the membrane module design, similar resistance per unit solid mass intercepted per unit area (Rmass) values were observed when the same mixed liquor was filtered. Coupled with the established correlation between the Rmass and the critical flux, it is suggested that the filterability test results from a side-stream, lab-scale module may be used to predict fouling potential in a full scale MBR wastewater treatment system without interrupting the full-scale MBR operation.

scholarly journals A bearing structure and finished construction behavior analysis based on the full-scale experimental research

2010 ◽  
Vol 8 (1) ◽  
pp. 119-127
Author(s):  
Slavko Zdravkovic ◽  
Dragan Zlatkov ◽  
Biljana Mladenovic ◽  
Tomislav Igic ◽  
Nikola Stojic
Keyword(s):  
Experimental Tests ◽  
Full Scale ◽  
Frame Structure ◽  
Ambient Vibration ◽  
Test Results ◽  
Structural System ◽  
Orthogonal Direction ◽  
Significant Discrepancy ◽  
Fourier Spectra ◽  
Bearing Structure

The paper deals with a brief presentation of a part of the performed experimental tests of the prefabricated reinforced concrete structural system 'AMONT' for construction of various types of modern industrial halls. The test results are analyzed for two industrial halls both constructed according to this structural system but in the different phases of construction, tested in the full scale by application of AMBIENT vibration method. From the obtained Fourier spectra for measured ambient vibrations in two orthogonal direction for the structure without walls and the other with fa?ade and filling walls, a significant discrepancy in their natural frequencies has been observed, and some conclusions about the influence of panel walls on dynamic characteristic the frame structure have been drawn out. The paper used some data of the research after the earthquake in Montenegro which took place on 15th of April 1979.

Experimental study of the strength and durability of metal-composite high-pressure tanks

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 49-56 ◽  
Author(s):  
A. M. Lepikhin ◽  
V. V. Moskvichev ◽  
A. E. Burov ◽  
E. V. Aniskovich ◽  
A. P. Cherniaev ◽  
...  
Keyword(s):  
High Pressure ◽  
Strain State ◽  
Full Scale ◽  
Fracture Mechanisms ◽  
Metal Composite ◽  
Test Results ◽  
Stress Strain ◽  
Pneumatic Pressure ◽  
Stress Strain State ◽  
Composite Tank

The results of unique experimental studies of the strength and service life of a metal-composite high-pressure tank are presented. The goal of the study is to analyze the fracture mechanisms and evaluate the strength characteristics of the structure. The methodology included tests of full-scale samples of the tank for durability under short-term static, long-term static and cyclic loading with internal pneumatic pressure. Generalized test results and data of visual measurements, instrumental and acoustic-emission control of deformation processes, accumulation of damages and destruction of full-scale tank samples are presented. Analysis of the strength and stiffness of the structure exposed to internal pneumatic pressure is presented. The types of limiting states of the tanks have been established experimentally. Change in the stress-strain state of the tank under cyclic and prolonged static loading is considered. Specific features of the mechanisms of destruction of a metal-composite tank are determined taking into account the role of strain of the metal liner. The calculated and experimental estimates of the energy potential of destruction and the size of the area affected upon destruction of the tank are presented. Analysis of test results showed that the tank has high strength and resource characteristics that meet the requirements of the design documentation. The results of the experiments are in good agreement with the results of numerical calculations and analysis of the stress-strain state and mechanisms of destruction of the metal-composite tank.

Predicting Roof Diaphragm and Endwall Stiffness From Full-Scale Test Results of a Metal-Clad, Post-Frame Building

1992 ◽  
Vol 35 (3) ◽  
pp. 977-985 ◽  
Author(s):  
K. G. Gebremedhin ◽  
J. A. Bartsch ◽  
M. C. Jorgensen
Keyword(s):  
Full Scale ◽  
Test Results ◽  
Full Scale Test ◽  
Frame Building ◽  
Scale Test

On axial compressive behavior of steel fiber reinforced concrete confined by FRP

2021 ◽  
pp. 136943322098165
Author(s):  
Hossein Saberi ◽  
Farzad Hatami ◽  
Alireza Rahai
Keyword(s):  
Reinforced Concrete ◽  
Experimental Test ◽  
Steel Fiber ◽  
Experimental Tests ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Test Results ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Frp Confinement

In this study, the co-effects of steel fibers and FRP confinement on the concrete behavior under the axial compression load are investigated. Thus, the experimental tests were conducted on 18 steel fiber-reinforced concrete (SFRC) specimens confined by FRP. Moreover, 24 existing experimental test results of FRP-confined specimens tested under axial compression are gathered to compile a reliable database for developing a mathematical model. In the conducted experimental tests, the concrete strength was varied as 26 MPa and 32.5 MPa and the steel fiber content was varied as 0.0%, 1.5%, and 3%. The specimens were confined with one and two layers of glass fiber reinforced polymer (GFRP) sheet. The experimental test results show that simultaneously using the steel fibers and FRP confinement in concrete not only significantly increases the peak strength and ultimate strain of concrete but also solves the issue of sudden failure in the FRP-confined concrete. The simulations confirm that the results of the proposed model are in good agreement with those of experimental tests.

Experimental and Analytical Investigation of Compact Liquid Cooled Heat Sinks

2004 ◽  
Author(s):  
M. Zugic ◽  
J. R. Culham ◽  
P. Teertstra ◽  
Y. Muzychka ◽  
K. Horne ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Tests ◽  
Reynolds Numbers ◽  
High Heat ◽  
Analytical Investigation ◽  
Boundary Resistance ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Air Cooling ◽  
Design Tools

Compact, liquid cooled heat sinks are used in applications where high heat fluxes and boundary resistance preclude the use of more traditional air cooling techniques. Four different liquid cooled heat sink designs, whose core geometry is formed by overlapped ribbed plates, are examined. The objective of this analysis is to develop models that can be used as design tools for the prediction of overall heat transfer and pressure drop of heat sinks. Models are validated for Reynolds numbers between 300 and 5000 using experimental tests. The agreement between the experiments and the models ranges from 2.35% to 15.3% RMS.

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