scholarly journals Numerical Simulation of Fluctuating Wind Effects on an Offshore Deck Structure

2017 ◽  
Vol 2017 ◽  
pp. 1-17 ◽  
Author(s):  
Jin Ma ◽  
Dai Zhou ◽  
Zhaolong Han ◽  
Kai Zhang ◽  
Jennifer Nguyen ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Parametric Design ◽  
Structural Response ◽  
Simulation Method ◽  
Offshore Structures ◽  
Vital Role ◽  
Structural Dynamic ◽  
Eddy Simulation ◽  
Wind Pressures ◽  
Fluctuating Wind

The offshore structures that play a vital role in oil and gas extraction are always under complicated environmental conditions such as the random wind loads. The structural dynamic response under the harsh wind is still an important issue for the safety and reliable design of offshore structures. This study conducts an investigation to analyze the wind-induced structural response of a typical offshore deck structure. An accurate and efficient mixture simulation method is developed to simulate the fluctuating wind speed, which is then introduced as the boundary condition into numerical wind tunnel tests. Large eddy simulation (LES) is utilized to obtain the time series of wind pressures on the structural surfaces and to determine the worst working condition. Finally, the wind-induced structural responses are calculated by ANSYS Parametric Design Language (APDL). The numerically predicted wind pressures are found to be consistent with the existing experimental data, demonstrating the feasibility of the proposed methods. The wind-induced displacements have the certain periodicity and change steadily. The stresses at the top of the derrick and connections between deck and derrick are relatively larger. These methods as well as the numerical examples are expected to provide references for the wind-resistant design of the offshore structures.

Stability of offshore structures in shallow water depth

2011 ◽  
Vol 2 (2) ◽  
pp. 320-333
Author(s):  
F. Van den Abeele ◽  
J. Vande Voorde
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Fossil Fuels ◽  
Oil And Gas ◽  
Structural Response ◽  
Offshore Structures ◽  
Exploration And Production ◽  
Subsea Pipelines ◽  
Wave Induced ◽  
Shallow Water Depth

The worldwide demand for energy, and in particular fossil fuels, keeps pushing the boundaries of offshoreengineering. Oil and gas majors are conducting their exploration and production activities in remotelocations and water depths exceeding 3000 meters. Such challenging conditions call for enhancedengineering techniques to cope with the risks of collapse, fatigue and pressure containment.On the other hand, offshore structures in shallow water depth (up to 100 meter) require a different anddedicated approach. Such structures are less prone to unstable collapse, but are often subjected to higherflow velocities, induced by both tides and waves. In this paper, numerical tools and utilities to study thestability of offshore structures in shallow water depth are reviewed, and three case studies are provided.First, the Coupled Eulerian Lagrangian (CEL) approach is demonstrated to combine the effects of fluid flowon the structural response of offshore structures. This approach is used to predict fluid flow aroundsubmersible platforms and jack-up rigs.Then, a Computational Fluid Dynamics (CFD) analysis is performed to calculate the turbulent Von Karmanstreet in the wake of subsea structures. At higher Reynolds numbers, this turbulent flow can give rise tovortex shedding and hence cyclic loading. Fluid structure interaction is applied to investigate the dynamicsof submarine risers, and evaluate the susceptibility of vortex induced vibrations.As a third case study, a hydrodynamic analysis is conducted to assess the combined effects of steadycurrent and oscillatory wave-induced flow on submerged structures. At the end of this paper, such ananalysis is performed to calculate drag, lift and inertia forces on partially buried subsea pipelines.

Numerical Simulation on Fatigue Life Assessment of Free Span for Submarine Pipeline

2015 ◽  
Vol 750 ◽  
pp. 153-159
Author(s):  
Jie Dong ◽  
Xue Dong Chen ◽  
Bing Wang ◽  
Wei He Guan ◽  
Tie Cheng Yang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Fatigue Life ◽  
Oil And Gas ◽  
Structural Response ◽  
Simulation Method ◽  
Life Assessment ◽  
Response Analysis ◽  
Submarine Pipeline ◽  
Fatigue Life Assessment ◽  
Harmonic Response Analysis

The upper and lower courses of sea oil and gas exploitationare connected by submarine pipeline which is called life line project. Free span often occurs because of the unevenness and scour of seabed, and fatigue is one of the main failure modes.In this paper, with the finite element numerical simulation method, based on the harmonic response analysis, the research on the structural response of free span under the vibration induced by vortex was investigated, and the effect of the factors such as flow velocity, length of free span. According to the analysis results,the fatigue life of free span was evaluated.

scholarly journals Transient flows past arrays of yawed finite prisms

2017 ◽  
Vol 95 (12) ◽  
pp. 1285-1298 ◽  
Author(s):  
I-Han Liu ◽  
Bashar Attiya ◽  
Alparslan Oztekin
Keyword(s):  
Drag Coefficient ◽  
Three Dimensional ◽  
Simulation Method ◽  
Offshore Structures ◽  
Wake Flow ◽  
Transient Flows ◽  
Eddy Simulation ◽  
Marine Current ◽  
Yaw Angle ◽  
Energy Harvesting Devices

Transient flows past arrays of yawed finite-length prisms in tandem and staggered arrangements are simulated. Large eddy simulation method is employed to characterize spatial and temporal characteristics of flows in the vicinity of prisms. Drag coefficients of prisms are determined for different spacing and yaw angle of prisms. Three-dimensional effects are investigated for different spacings of prisms in a tandem array. Drag coefficient of downstream prism is significantly lower compared to that of upstream prism when prisms are tightly spaced. Drag coefficient of downstream prism predicted by simulations in three-dimensional geometry is recovered fully as spacing approaches 10 times the height of the prism while drag coefficient predicted by simulations in two-dimensional geometry is only about 30% of the upstream prism even when two prisms are separated by 20 times the height of the prism. The wake flow patterns do not influence the drag coefficient strongly for the staggered arrays of yawed prisms. Prisms can be placed in a tighter arrangement without a significant penalty of drag reduction. Mathematical models and numerical methods employed are validated by comparing simulation results against experimental results. Drag exerted on these prisms can directly be related to power generation by devices containing translating blades of marine-current applications. This study demonstrates that arrangement, spacing, and yaw angle can be used to design and optimize energy harvesting devices and other offshore structures.

A Study on Dynamic Behavior of Offshore Structures Under the Blast Load

2011 ◽  
Author(s):  
Kun-Hee Lee ◽  
Ki Young Yoon
Keyword(s):  
Nonlinear Dynamic ◽  
Oil And Gas ◽  
Nonlinear Dynamic Analysis ◽  
Structural Response ◽  
Offshore Structures ◽  
Blast Load ◽  
Economic Approach ◽  
Offshore Structure ◽  
Oil And Gas Development ◽  
High Possibility

Safety verification against blast load is important in offshore structure for oil and gas development which have the high possibility of explosion accident. The structural response against blast is a nonlinear dynamic phenomenon, it is necessary the nonlinear dynamic analysis for accurate structural behavior. But it requires much more computing resource and manpower than conventional linear analysis. Therefore, simple approaches such as modified code check and Biggs’ simplified SDOF have been widely used for the structural verification. These approaches are very useful in design for simplicity and conservativeness. However, they don’t represent proper dynamic characteristics, thus sometimes they may cause excessively conservative. In this paper, the dynamic characteristic of structures beyond the yield point is studied by using nonlinear dynamic FE analysis and more safe and economic approach is suggested.

scholarly journals Derivation of the Probability Distribution of Extreme Values of Offshore Structural Response by Efficient Time Simulation Method

2013 ◽  
Vol 7 (1) ◽  
pp. 261-272 ◽  
Author(s):  
M.K. Abu Husain ◽  
N.I. Mohd Zaki ◽  
G. Najafian
Keyword(s):  
Probability Distribution ◽  
Extreme Values ◽  
Structural Response ◽  
Simulation Method ◽  
Offshore Structures ◽  
Random Wave ◽  
Wave Loading ◽  
Sampling Variability ◽  
Economical Design ◽  
Ocean Environment

Offshore structures are exposed to random wave loading in the ocean environment and hence the probability distribution of the extreme values of their response to wave loading is required for their safe and economical design. To this end, the conventional simulation technique (CTS) is frequently used for predicting the probability distribution of the extreme values of response. However, this technique suffers from excessive sampling variability and hence a large num-ber of simulated response extreme values (hundreds of simulated response records) are required to reduce the sampling variability to acceptable levels. A more efficient method (ETS) was recently introduced which takes advantage of the cor-relation between the extreme values of surface elevation and their corresponding response extreme values. The method has proved to be very efficient for high-intensity sea states; however, the correlation and hence the efficiency and accura-cy of the technique reduces for sea states of lower intensity. In this paper, a more efficient version of the ETS technique is introduced which takes advantage of the correlation between the extreme values of the nonlinear response and their corre-sponding linear response values.

Modelling Two-Dimensional Ice-Induced Vibrations of Offshore Structures With Geometric Nonlinearities

2015 ◽  
Author(s):  
Hugh McQueen ◽  
Narakorn Srinil
Keyword(s):  
Numerical Model ◽  
Oil And Gas ◽  
Numerical Models ◽  
Wedge Angle ◽  
Offshore Structures ◽  
Degree Of Freedom ◽  
Two Dimensional ◽  
Structural Dynamic ◽  
Geometric Nonlinearities ◽  
Nonlinear Stress

Oil and gas exploration and production has been expanding in Arctic waters. However, numerical models for predicting the ice-induced vibrations (IIV) of offshore structures are still lacking in literature. This study aims to develop a mathematical reduced-order model for predicting the two-dimensional IIV of offshore structures with geometric coupling and nonlinearities. A cylindrical structure subject to a moving uniform ice sheet is analysed using the well-known Matlock model which, in the present study, is extended and modified to account for a new empirical nonlinear stress-strain rate relationship determining the maximum compressive stress of the ice. The model is further developed through the incorporation of ice temperature, brine content, air volume, grain size, ice thickness and ice wedge angle effects on the ice compressive strength. These allow the effect of multiple ice properties on the ice-structure interaction to be investigated. A further advancement is the inclusion of an equation allowing the length of failed ice at a point of failure to vary with time. A mixture of existing equations and newly proposed empirical relationships are used. Structural geometric nonlinearities are incorporated into the numerical model through the use of Duffing oscillators, a technique previously proposed in vortex-induced vibration studies. A one-degree-of-freedom (DOF) model is successfully validated against experimental results from the literature whilst the extended two-degree-of-freedom model produces new insights. Parametric studies highlight the effect of asymmetric geometric nonlinearities and ice velocity on the structural dynamic response. Results were compared to Palmer et al. (2010) which identified quasi-static, random-like or chaotic and locked-in motions. This numerical model has advanced the original Matlock model, showing a potential to be used in future IIV analysis of arctic cylindrical structures, particularly fixed offshore structures such as lighthouses, gravity bases and wind turbine monopiles.

The Effect of Current on the Dynamic Responses of Truss Spar in Malaysia Water

2016 ◽  
Author(s):  
S. N. A. Tuhaijan ◽  
C. Y. Ng ◽  
V. J. Kurian
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Model Tests ◽  
Dynamic Responses ◽  
Water Current ◽  
Sea Waves ◽  
Structural Dynamic ◽  
Gas Industry ◽  
Truss Spar

In South East Asia, Malaysia is one of the leading countries in the oil and gas industry. Today, Malaysia has expanded the explorations into the deeper water region. Before the installation of the Malaysia first deepwater platform, the Kikeh Spar, spar platforms can only be found in the Gulf of Mexico. Malaysian offshore regions are subjected to significant water current. From the literature review carried out, it was found that the current would change the behavior of the sea waves. This is contributing significantly to the environmental loading and affect the dynamic responses of the offshore structures. Hence, the study that focused on the effects of the current together with the wave on the structural dynamic response is necessary. In this study, the effect of the current coexisting with the wave on the dynamic responses of a truss spar model was experimentally investigated and quantified. The model tests were performed in the wave tank of the Offshore Laboratory in Universiti Teknologi PETRONAS with a scaling factor of 1:100. Two sets of environmental conditions were considered in the model tests i.e. wave only and wave-current condition. The dynamic responses of the truss spar model subjected to these conditions were measured. In order to quantify the effect of current, the measured results for the condition with and without current were compared among and presented here. From this investigation, it was found that the existence of the current in the water body has increased the truss spar motions, whereby the higher current velocity, give the higher response.

Long-Term Probability Distribution of Extreme Offshore Structural Response via an Efficient Time Simulation Method

2013 ◽  
Author(s):  
M. K. Abu Husain ◽  
N. I. Mohd Zaki ◽  
L. Lambert ◽  
Y. Wang ◽  
G. Najafian
Keyword(s):  
Probability Distribution ◽  
Extreme Values ◽  
Structural Response ◽  
Simulation Method ◽  
Offshore Structures ◽  
Random Wave ◽  
Wave Loading ◽  
Sampling Variability ◽  
Extreme Response

Offshore structures are exposed to random wave loading in the ocean environment and hence the probability distribution of the extreme values of their response to wave loading is required for their safe and economical design. To this end, the conventional simulation technique (CTS) is frequently used for predicting the probability distribution of the extreme values of response. However, this technique suffers from excessive sampling variability and hence a large number of simulated response extreme values (hundreds of simulated response records) are required to reduce the sampling variability to acceptable levels. A more efficient method (ETS) was recently introduced which takes advantage of the correlation between the extreme values of linear response and their corresponding response extreme values. The method has proved to be very efficient for both low and high-intensity sea states. In this paper, further development of this technique, which leads to more accurate estimates of the long term probability distribution of the extreme response, is reported.

Research on Numerical Simulation of High-Speed Railway Noise Barrier Aerodynamic Pressure

2013 ◽  
Vol 274 ◽  
pp. 45-48 ◽  
Author(s):  
Hong Mei Li ◽  
Yan Xuan ◽  
Lan Wang ◽  
Yan Liang Li ◽  
Xing Fang ◽  
...  
Keyword(s):  
Finite Element ◽  
Structural Design ◽  
High Speed ◽  
Extreme Values ◽  
Element Model ◽  
Simulation Method ◽  
Noise Barriers ◽  
Aerodynamic Pressure ◽  
Wind Pressures ◽  
Fluctuating Wind

Based on finite volume method of finite element method, the aerodynamics models of the train passing through bridge noise barriers (high respectively, for 2.15m, 1.93m) and the subgrade (high respectively, for 2.95m,3.95m) noise barriers is established by large commercial fluid dynamics calculation software. The three dimensional transient outflow field is numerical simulated by applying dynamic mesh technology and large eddy simulation method (LES) for the train passing through noise barriers. The extreme value, schedule curve and pressure cloud contour of fluctuating wind pressures of the different height noise barriers on bridge and roadbed are acquired for 300 ~ 420 km/h different speeds. Extreme values of fluctuating wind pressures product by trains with different speeds are contrast analyzed. The simulation results are very close to the experimental data, proves the validity and feasibility of the finite element model and the accuracy of the parameters. This research provides the theory support to the structural design of the noise barriers and can effectively guide the structural design of the noise barriers.

A method of technical diagnostics for offshore structures

1994 ◽  
Vol 16 (2) ◽  
pp. 43-48
Author(s):  
Do Son
Keyword(s):  
Diagnostic Method ◽  
Joint Venture ◽  
Oil And Gas ◽  
Residual Life ◽  
Life Time ◽  
Offshore Structures ◽  
Technical Diagnostics ◽  
Offshore Platforms ◽  
South Vietnam ◽  
Local Destruction

This paper describes the results of measurements and analysis of the parameters, characterizing technical state of offshore platforms in Vietnam Sea. Based on decreasing in time material characteristics because of corrosion and local destruction assessment on residual life time of platforms is given and variants for its repair are recommended. The results allowed to confirm advantage of proposed technical diagnostic method in comparison with others and have been used for oil and gas platform of Joint Venture "Vietsovpetro" in South Vietnam.

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