Vortex-Induced Vibration of a Free-Hanging Riser Under Irregular Vessel Motion

2016 ◽  
Author(s):  
Jungao Wang ◽  
Rajeev Kumar Jaiman ◽  
Peter Francis Bernad Adaikalaraj ◽  
Linwei Shen ◽  
Sue Ben Tan ◽  
...  
Keyword(s):  
Literature Review ◽  
Experimental Validation ◽  
Ocean Current ◽  
Current Profile ◽  
Vortex Induced Vibration ◽  
Norwegian Sea ◽  
Irregular Wave ◽  
Riser Design ◽  
Similarities And Differences ◽  
Vessel Motion

In this paper, we focus on vortex-induced vibration (VIV) of a free-hanging riser attached to a vessel under irregular wave conditions. The global in-plane responses of the hanging riser are firstly studied numerically in order to generate the equivalent current profile under vessel motion, and a simplified irregular vessel motion-induced VIV prediction methodology is then proposed based on the understanding from previous experimental observations and literature review. Further comparison on irregular vessel motion-induced VIV and ocean current-induced VIV at the same operation site with the same return period is performed to emphasize the importance of vessel motion-induced VIV. Numerical results highlight that vessel motion-induced VIV can cause similar stresses, fatigue damage and drag amplification similar to the steady ocean current cases, especially to the operation site like Norwegian Sea where strong wave field exists with mild current condition. It should be mentioned that although the simplified methodology proposed in this paper requires further experimental validation, it is believed that the presented numerical pre-study would help the industry and the researchers to have initial understanding on the possible occurrence of vessel motion-induced VIV. We further show the similarities and differences of vessel motion-induced VIV with respect to the ocean current-induced VIV and its implications on riser design and operation.

Experimental Investigation on Vortex-Induced Vibration of a Free-Hanging Riser Under Vessel Motion and Uniform Current

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Jungao Wang ◽  
Shixiao Fu ◽  
Jiasong Wang ◽  
Huajun Li ◽  
Muk Chen Ong
Keyword(s):  
Prediction Models ◽  
Ocean Basin ◽  
Dynamic Responses ◽  
Ocean Current ◽  
Response Frequency ◽  
Vortex Induced Vibration ◽  
Out Of Plane ◽  
Future Prediction ◽  
Uniform Current ◽  
Vessel Motion

A model test of a free-hanging riser under vessel motion and uniform current is performed in the ocean basin at Shanghai Jiao Tong University to address four topics: (1) confirm whether vortex-induced vibration (VIV) can happen due to pure vessel motion; (2) to investigate the equivalent current velocity and Keulegan–Carpenter (KC) number effect on the VIV responses; (3) to obtain the correlations for free-hanging riser VIV under vessel motion with VIV for other compliant risers; and (4) to study the similarities and differences with VIV under uniform current. The top end of the riser is forced to oscillate or move, in order to simulate vessel motion or ocean current effects. Fiber Bragg Grating (FBG) strain sensors are used to measure the riser dynamic responses. Experimental results confirm that the free-hanging riser will experience significant out-of-plane VIV under vessel motion. Meanwhile, vessel motion-induced VIV responses in terms of response amplitude, response frequency, and cross section trajectories under different test cases are further discussed and compared to those under ocean uniform current. Most importantly, the correlation among VIV response frequency, vortex shedding pairs, and maximum KC number KCmax is revealed. The presented work is supposed to provide useful references for gaining a better understanding on VIV of a free-hanging riser and for the development of future prediction models.

Strength Performance of Steel Catenary Riser Using Short Term and Long Term Analysis Methodologies

2016 ◽  
Author(s):  
Feng Wang ◽  
Roger Burke ◽  
Anil Sablok ◽  
Kristoffer H. Aronsen ◽  
Oddgeir Dalane
Keyword(s):  
Bending Moment ◽  
Current Profile ◽  
Short Term ◽  
Sea State ◽  
Strength Performance ◽  
Steel Catenary Riser ◽  
Analysis Methodology ◽  
Riser Design ◽  
Term Analysis

Strength performance of a steel catenary riser tied back to a Spar is presented based on long term and short term analysis methodologies. The focus of the study is on response in the riser touch down zone, which is found to be the critical region based on short term analysis results. Short term riser response in design storms is computed based on multiple realizations of computed vessel motions with various return periods. Long term riser response is based on vessel motions for a set of 45,000 sea states, each lasting three hours. The metocean criteria for each sea state is computed based on fifty six years of hindcast wind and wave data. A randomly selected current profile is used in the long term riser analysis for each sea state. Weibull fitting is used to compute the extreme riser response from the response of the 45,000 sea states. Long term analysis results in the touch down zone, including maximum bending moment, minimum effective tension, and maximum utilization using DNV-OS-F201, are compared against those from the short term analysis. The comparison indicates that the short term analysis methodology normally followed in riser design is conservative compared to the more accurate, but computationally more expensive, long term analysis methods. The study also investigates the important role that current plays in the strength performance of the riser in the touch down zone.

Riser Concept Selection for FPSO in Deepwater Norwegian Sea: A Case Study

2018 ◽  
Author(s):  
Arvind Keprate ◽  
R. M. Chandima Ratnayake
Keyword(s):  
Literature Review ◽  
Geographical Location ◽  
Weather Conditions ◽  
Large Vessel ◽  
Concept Selection ◽  
Flexible Riser ◽  
Norwegian Sea ◽  
Daunting Task ◽  
Selection For

Selecting a riser concept for FPSOs stationed in deep water has posed challenges, due to the high hydrostatic pressure and large vessel payload. One of the major factors governing the riser concept selection for deepwater FPSOs is the geographical location and weather conditions prevalent in the region. For example, the free hanging flexible riser has been mostly used in the moderate environments of offshore Brazil, while concepts like the SCR and Hybrid Riser Tower (HRT) are dominant in the calm weather conditions of the West of Africa (WoA). Selecting a riser concept for an FPSO stationed in harsh weather conditions like those of the Northern Norwegian Sea is a daunting task. This is due to the large vessel offsets and dynamics, which are directly transferred along the riser’s length to its base, thereby causing considerable fatigue damage to the riser. The main aim of this paper is to recommend a suitable riser concept, which may be hooked to an internal turret moored FPSO stationed in water of 1500m depth and in the harsh environmental conditions of the Northern Norwegian Sea. The recommendations are based on the literature review and the case study performed in the manuscript. On the basis of the literature review, a lazy wave configuration of flexible riser and Steel Lazy Wave Riser (SLWR) has been considered as a viable riser concept. Thereafter, a case study is performed to compare the two riser concepts, on the basis of vessel payload, fabrication cost and installation cost.

scholarly journals Towards Developing Innovation Management Framework (IMF) for ICT Organizations at Pakistan

2021 ◽  
Author(s):  
Eram Abbasi ◽  
Imran Amin ◽  
Shama Siddiqui
Keyword(s):  
Comparative Analysis ◽  
Literature Review ◽  
Innovation Management ◽  
Factors Affecting ◽  
Management Framework ◽  
Underdeveloped Countries ◽  
The Past ◽  
Similarities And Differences ◽  
Industry Culture ◽  
Developed World

Abstract Various aspects of innovation management have been discussed in literature over the past few decades. Most of the innovation management frameworks have been formulated by undertaking studies in the developed world and lack the industry / culture specific focus. In this paper we revisit the generic innovation management studies to develop an innovation management framework for highlighting the factors affecting innovation specifically at the ICT sector of Pakistan. A detailed literature review has been conducted to identify the factors included in the past innovation management models. To identify the factors specific for Pakistan, senior level professionals, working at the Pakistani ICT organizations were interviewed. A comparative analysis of the innovation management frameworks for Pakistan against those previously found in literature revealed interesting similarities and differences. Based on the study findings, an innovation management framework is developed that highlights the present factors which are important for innovation in the ICT sector for Pakistan. This framework can be used by Pakistan and other underdeveloped countries for improving their innovation in ICT sectors in particular and other sectors in general.

An Approach to Include Observed VIV Likelihood in Drilling Riser Fatigue Analyses

2009 ◽  
Author(s):  
Michael A. Tognarelli ◽  
Rene D. Gabbai ◽  
Mike Campbell
Keyword(s):  
Fatigue Damage ◽  
Field Measurements ◽  
Scaling Analysis ◽  
Current Profile ◽  
Vortex Induced Vibration ◽  
Probability Of Occurrence ◽  
Industry Standard ◽  
Annual Probability ◽  
Analysis Computer ◽  
Viv Suppression

Field measurements of the response of a number of drilling risers indicate that vortex-induced vibration (VIV) occurs significantly less often than predicted by the industry-standard fatigue analysis computer program SHEAR7 V4.4. Several comparisons to model tests and field data, including one published by BP and 2H in 2007 [1], demonstrate that this analysis program is generally quite conservative, given that VIV occurs. Furthermore, this conservatism does not take into account those situations in which VIV fatigue is predicted but none is observed in the field, which adds yet another layer of “hidden” conservatism to design analyses. In an effort to address this and reduce conservatism to a more appropriate level, the probability of occurrence of vortex-induced vibration (VIV) is examined using full-scale measured data. The data has been collected over the past several years from five drilling risers without VIV suppression devices. These risers are on rigs under contract to BP at high-current-susceptible sites worldwide. Collectively, the data correspond to 9,600 10-minute field measurements, equivalent to 0.18 years of continuous monitoring. The riser response is obtained from motion loggers placed at selected positions along the riser as described in [1]. Each logger measures 3D accelerations and 2D angular rates. Through-depth currents are measured via Acoustic Doppler Current Profilers (ADCP). By comparison of measurements to computer predictions based on the observed current profile, a relationship is developed between the intensity of the fatigue damage predicted and the probability that VIV is observed in the field. Subsequently, an approach is proposed for scaling analysis predictions to reflect the relative likelihood of VIV. The database of measured and SHEAR7 maximum predicted fatigue damage rates is statistically characterized to determine how it may be used to determine factors of safety (FOS) for VIV design. A worked example for a deepwater drilling riser in the GoM is used to show how the FOS methodology can be applied in the case of multiple design currents each with a different annual probability of occurrence.

Theoretical and Empirical Comparative Analysis on Quantitative and Qualitative Marketing Researches

2015 ◽  
pp. 1712-1730
Author(s):  
Piotr Tarka ◽  
Mirosława Kaczmarek
Keyword(s):  
Qualitative Research ◽  
Comparative Analysis ◽  
Literature Review ◽  
Empirical Research ◽  
Marketing Research ◽  
Research Projects ◽  
Research Project ◽  
Quantitative And Qualitative Research ◽  
Similarities And Differences ◽  
Methodological Aspects

This chapter focuses on the similarities and differences between quantitative and qualitative marketing research projects and the possibilities of combining them in triangulation. The comparative analysis of both types of the research was conducted on the basis of literature review and the empirical research results, which were obtained from the evaluation of usability of Polish bank website. In the following sections, the authors discuss issues such as: 1) specificity of quantitative vs. qualitative marketing research, with regards to the implemented research projects; 2) methodological aspects of quantitative and qualitative research. They compare the selected research and sampling methods. Also, the problems which may occur with reference to quantitative and qualitative marketing research triangulation on different stages of the research project are discussed. Moreover, strengths and weaknesses of triangulation are analyzed. At the end, the example of quantitative and qualitative triangulation in the research project investigating the usability of websites is presented.

Experimental Study on the Avoidance and Suppression Criteria for the Vortex-Induced Vibration of a Cantilever Cylinder

2002 ◽  
Vol 124 (2) ◽  
pp. 187-195 ◽  
Author(s):  
Takaaki Sakai ◽  
Masaki Morishita ◽  
Koji Iwata ◽  
Seiji Kitamura
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Water Flow ◽  
Experimental Validation ◽  
Flow Direction ◽  
High Viscosity ◽  
Design Guideline ◽  
Vortex Induced Vibration ◽  
High Viscosity Oil ◽  
Effect Of Structure

Experimental validation of the design guideline to prevent the failure of a thermometer well by vortex-induced vibration is presented, clarifying the effect of structure damping on displacement amplitudes of a cantilever cylinder. The available experimental data in piping are limited to those with small damping in water flow, because of the difficulty in increasing structure damping of the cantilever cylinders in experiments. In the present experiment, high-viscosity oil within cylinders is used to control their structure damping. Resulting values of reduced damping Cn are 0.49, 0.96, 1.23, 1.98, and 2.22. The tip displacements of the cylinder induced by vortex vibration were measured in the range of reduced velocity Vr from 0.7 to 5 (Reynolds number is 7.8×104 at Vr=1). Cylinders with reduced damping 0.49 and 0.96 showed vortex-induced vibration in the flow direction in the Vr>1 region. However, in cases of reduced damping of 1.23, 1.98, and 2.22, the vibration was suppressed to less than 1 percent diameter. It is confirmed that the criteria of “Vr<3.3 and Cn>1.2” for the prevention of vortex-induced vibration is reasonably applicable to a cantilever cylinder in a water flow pipe.

Simulation of Strong Inertial Currents to Support Preliminary Engineering Offshore Namibia

2013 ◽  
Author(s):  
Gus Jeans ◽  
Ian Wade
Keyword(s):  
Ocean Current ◽  
Current Profile ◽  
Sea Breezes ◽  
The Public ◽  
Current Regime ◽  
Local Current ◽  
Exploration Drilling ◽  
Inertial Currents ◽  
Inertial Energy

The vertical profile of ocean current needs to be characterised for preliminary engineering applications such as exploration drilling. The acquisition of suitable current profile data can be a key challenge, especially in relatively unexplored deepwater frontier regions. Recent years have seen a dramatic increase in the use of ocean current models for this purpose, frequently involving freely available data from the HYCOM consortium. These data have proven reliable in some locations, but the accuracy remains questionable, or unproven, in many others. This paper describes a study in which it was clear from the outset that HYCOM would not represent dominant features of the local current regime. This concerned the region offshore Namibia, near 30°S, at which latitude the inertial period of natural ocean oscillation equals the diurnal period of 24 hours. This region is also subjected to relatively strong diurnal sea breezes, which can drive nearly resonant inertial responses in the ocean, which can, in turn, dominate the current regime. The spatial resolution of the wind field used to drive the global HYCOM model is insufficient to resolve this critical wind forcing, so the resulting model currents cannot represent the dominant features. Fortunately some relevant measurements were well documented in the public domain, from which a pragmatic inertial current simulation methodology was developed. Lack of inertial energy was actually beneficial for using HYCOM daily spot values to represent other, longer term, components of the flow. If inertial currents had been represented in the model, then more frequent values would be required to capture them. HYCOM data proved useful for representing long term inter-annual variability in the features it does represent, including meanders in the seasonal Benguala current.

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