Prediction of Combined Inline and Crossflow Vortex-Induced Vibrations Response of Deepwater Risers

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Jie Wu ◽  
Malakonda Reddy Lekkala ◽  
Muk Chen Ong ◽  
Elizabeth Passano ◽  
Per Erlend Voie
Keyword(s):  
Fatigue Damage ◽  
Massachusetts Institute Of Technology ◽  
Ocean Engineering ◽  
Flexible Cylinder ◽  
Load Model ◽  
Cylinder Test ◽  
Excitation Coefficient ◽  
Vortex Induced Vibrations ◽  
Institute Of Technology ◽  
Deepwater Risers

Deepwater risers are susceptible to vortex-induced vibrations (VIV) when subjected to currents. When responding at high modes, fatigue damage in the inline (IL) direction may become equally important as the crossflow (CF) components. Accurate calculation of both IL and CF responses is therefore needed. Empirical VIV prediction programs, such as VIVANA “Passano et al. (2016, “VIVANA—Theory Manual Version 4.8,” Trondheim, Norway),” SHEAR7 “(Vandiver, J. K., and Li, L., 2007, “Shear7 v4.5 Program Theoretical Manual,” Department of Ocean Engineering, Massachusetts Institute of Technology, Cambridge, MA),” and VIVA “Triantafyllou et al. (1999, “Pragmatic Riser VIV Analysis,” Offshore Technology Conference, Houston, TX, May 3–6, Paper No. OTC-10931-MS.)” are the most common tools used by the offshore industry. Progress has been seen in the prediction of CF responses. Efforts have also been made to include an IL load model in VIVANA. A set of excitation coefficient parameters were obtained from rigid cylinder test and adjusted using measured responses of one of the flexible cylinder VIV tests. This set of excitation coefficient parameters is still considered preliminary and further validation is required. Without an accurate IL response prediction, a conservative approach in VIV analysis has to be followed, i.e., all current profiles have to be assumed to be unidirectional or acting in the same direction. The purpose of this paper is to provide a reliable combined IL and CF load model for the empirical VIV prediction programs. VIV prediction using the existing combined IL and CF load model in VIVANA is validated against selected flexible cylinder test data. A case study of a deepwater top tension riser (TTR) has been carried out. The results indicate that VIV fatigue damage using two-dimensional directional current profiles is less conservative compared to the traditional way of using unidirectional current profiles.

Prediction of Combined IL and CF VIV Response of Deepwater Risers

2017 ◽  
Author(s):  
Jie Wu ◽  
Malakonda Reddy Lekkala ◽  
Muk Chen Ong ◽  
Elizabeth Passano ◽  
Per Erlend Voie
Keyword(s):  
Fatigue Damage ◽  
Cross Flow ◽  
Response Prediction ◽  
Flexible Cylinder ◽  
Load Model ◽  
Cylinder Test ◽  
Excitation Coefficient ◽  
The Cross ◽  
Offshore Industry ◽  
Deepwater Risers

Deepwater risers are susceptible to Vortex Induced Vibrations (VIV) when subjected to currents. When responding at high modes, fatigue damage the in in-line (IL) direction may become equally important as the cross-flow (CF) components. If a riser experiences directional currents, fatigue damage must be evaluated at several locations on the cross-section’s circumference. Accurate calculation of both IL and CF responses are therefore needed. Empirical VIV prediction programs, such as VIVANA, SHEAR7 and VIVA, are the most common tools used by the offshore industry to design against VIV loads. Progress has been seen in the prediction of CF responses. Efforts have also been made to include an IL load model in VIVANA. A set of excitation coefficient parameters were obtained from rigid cylinder test and adjusted using measured responses of one of the flexible cylinder VIV tests. This set of excitation coefficient parameters is still considered preliminary and further validation is required. Without an accurate IL response prediction, a conservative approach in VIV analysis has to be followed, i.e. all current profiles have to assumed to be uni-directional or acting in the same direction. The purpose of the present paper is to provide a reliable combined IL and CF load model for the empirical VIV prediction programs. VIV prediction using the existing combined IL and CF load model in VIVANA is validated against selected flexible cylinder test data. A case study of a deepwater top tension riser (TTR) has been carried out. The results indicate VIV fatigue damage 1 using 2D directional current profiles is less conservative compared to the traditional way of using unidirectional current profiles.

Hydrodynamics of Flexible Pipe With Staggered Buoyancy Elements Undergoing Vortex-Induced Vibrations

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Mengmeng Zhang ◽  
Shixiao Fu ◽  
Leijian Song ◽  
Jie Wu ◽  
Halvor Lie ◽  
...  
Keyword(s):  
Unit Length ◽  
Added Mass ◽  
Hydrodynamic Characteristics ◽  
Ocean Engineering ◽  
Flexible Pipe ◽  
Excitation Coefficient ◽  
Vortex Induced Vibrations ◽  
Sea Current ◽  
Coefficients Identification ◽  
Structural Mass

Flexible pipe with staggered buoyancy elements such as lazy wave riser and drilling riser has been widely used in ocean engineering. Under the influence of sea current, both of the buoyancy elements and the riser may experience vortex induced vibrations (VIV). However, when VIV occurs, hydrodynamic characteristics of the buoyancy elements and its influence on hydrodynamic force of the bare pipe still need investigation. The purpose of this paper is to reveal the hydrodynamic characteristics of flexible pipe with staggered buoyancy elements undergoing VIV. The crossflow (CF) hydrodynamic coefficients of the flexible pipe with 25%, 50%, and 100% coverage of staggered buoyancy are obtained from model tests, using hydrodynamic forces and coefficients identification method. Then, the characteristics of added mass coefficients and excitation coefficients in CF direction are analyzed. The results show that the added-mass coefficients of bare pipe are relatively larger than those of buoyancy module, while the total mass per unit length (sum of structural mass and added mass) is consistent along the pipe. Similarly, the range of excitation coefficient on the buoyancy elements is smaller than that on the bare pipe, and their ratio is equal to the reciprocal of diameter ratio 2.5.

Applying the Anderson-Darling Test to Suicide Clusters

Crisis ◽  
2013 ◽  
Vol 34 (6) ◽  
pp. 434-437 ◽  
Author(s):  
Donald W. MacKenzie
Keyword(s):  
Poisson Process ◽  
Goodness Of Fit ◽  
Small Samples ◽  
Massachusetts Institute Of Technology ◽  
Homogeneous Poisson Process ◽  
Cornell University ◽  
The Difference ◽  
Suicide Clusters ◽  
Institute Of Technology ◽  
Anderson Darling

Background: Suicide clusters at Cornell University and the Massachusetts Institute of Technology (MIT) prompted popular and expert speculation of suicide contagion. However, some clustering is to be expected in any random process. Aim: This work tested whether suicide clusters at these two universities differed significantly from those expected under a homogeneous Poisson process, in which suicides occur randomly and independently of one another. Method: Suicide dates were collected for MIT and Cornell for 1990–2012. The Anderson-Darling statistic was used to test the goodness-of-fit of the intervals between suicides to distribution expected under the Poisson process. Results: Suicides at MIT were consistent with the homogeneous Poisson process, while those at Cornell showed clustering inconsistent with such a process (p = .05). Conclusions: The Anderson-Darling test provides a statistically powerful means to identify suicide clustering in small samples. Practitioners can use this method to test for clustering in relevant communities. The difference in clustering behavior between the two institutions suggests that more institutions should be studied to determine the prevalence of suicide clustering in universities and its causes.

Editorial: Advancing the Debate on Architecture, Planning, and Built Environment Research

2015 ◽  
Vol 9 (2) ◽  
Author(s):  
Ashraf M. Salama
Keyword(s):  
Learning Styles ◽  
Cultural Values ◽  
Urban Studies ◽  
Wide Spectrum ◽  
Journal Ranking ◽  
Massachusetts Institute Of Technology ◽  
Open Access Journals ◽  
Practice Based Research ◽  
Institute Of Technology ◽  
Number Of Citations

With an acceptance rate that does not exceed 25% of the total papers and articles submitted to the journal, IJAR – International Journal of Architectural Research is moving forward to position itself among the leading journals in architecture and urban studies worldwide. As this is the case since the beginning of volume 5, issue 1, March 2011, one must note that the journal has been covered by several data and index bases since its inception including Avery Index to Architectural Periodicals, EBSCO-Current Abstracts-Art and Architecture, INTUTE, Directory of Open Access Journals, Pro-Quest, Scopus-Elsevier and many university library databases across the globe. This is coupled with IJAR being an integral part of the archives and a featured collection of ArchNet and the Aga Khan Documentation Centre at MIT: Massachusetts Institute of Technology, Cambridge, MA.In 2014, IJAR was included in Quartile 2 / Q2 list of Journals both in ‘Architecture’ and ‘Urban Studies.’ As of May 2015, IJAR is ranked 23 out of 83 journals in ‘Architecture’ and 59 out of 119 in ‘Urban Studies.’ Rankings are based on the SJR (SCImago Journal Ranking); an Elsevier- SCOPUS indicator that measures the scientific influence of the average article in a journal. SJR is a measure of scientific influence of scholarly journals that accounts for both the number of citations received by a journal and the importance or prestige of the journals where such citations come from. See here for more information (http://www.scimagojr.com/index.php) and (http://www.journalmetrics.com/sjr.php). While the journal is now on top of many of the distinguished journals in Elsevier- SCOPUS database, we will keep aspiring to sustain our position and move forward to Q1 group list and eventually in the top 10 journal list in the field. However, this requires sustained efforts and conscious endeavours that give attention to quality submissions through a rigorous review process. This edition of IJAR: volume 9, issue 2, July 2015 includes debates on a wide spectrum of issues, explorations and investigations in various settings. The issue encompasses sixteen papers addressing cities, settlements, and projects in Europe, South East Asia, and the Middle East. Papers involve international collaborations evidenced by joint contributions and come from scholars in universities, academic institutions, and practices in Belgium; Egypt; Greece; Italy; Jordan; Malaysia; Palestine; Qatar; Saudi Arabia; Serbia; Spain; Turkey; and the United Kingdom. In this editorial I briefly outline the key issues presented in these papers, which include topics relevant to social housing, multigenerational dwelling, practice-based research, sustainable design and biomimetic models, learning environments and learning styles, realism and the post modern condition, development and planning, urban identity, contemporary landscapes, and cultural values and traditions.

XX Rudi Dombusch, Keys to Prosperity. Free Markets, Sound Money, and bit of Luck The MIT Press 2000 Londres

2009 ◽  
Vol 33 (130) ◽  
Author(s):  
GERARDO REYES GUZMÁN
Keyword(s):  
Massachusetts Institute ◽  
Massachusetts Institute Of Technology ◽  
Free Markets ◽  
Institute Of Technology

Rudiger Dornbusch, destacado economista del Massachusetts Institute of Technology (MIT), analiza en esta trascendental obra tópicos como inflación, deuda, tipos de cambio, política externa y mercados emergentes. El marco conceptual descansa en la corriente de la escuela de Chicago, la cual parte del principio de que el mercado es el mecanismo que garantiza la creación del progreso en contraste con el Estado, que en su afán por encontrar soluciones perfectas, fracasa regularmente en sus cometidos.

Life sciences intellectual property licensing at the Massachusetts Institute of Technology

2021 ◽  
Vol 39 (3) ◽  
pp. 293-301
Author(s):  
Samuel Huang ◽  
Kien Wei Siah ◽  
Detelina Vasileva ◽  
Shirley Chen ◽  
Lita Nelsen ◽  
...  
Keyword(s):  
Intellectual Property ◽  
Life Sciences ◽  
Massachusetts Institute ◽  
Massachusetts Institute Of Technology ◽  
Institute Of Technology
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