Risers Clashing Induced by the Wake Interference

2008 ◽  
Author(s):  
Antonio C. Fernandes ◽  
Stefania D. Rocha ◽  
Fabio M. Coelho ◽  
Breno P. Jacob ◽  
Joseane V. Queiroz ◽  
...  
Keyword(s):  
Relative Position ◽  
Minimum Distance ◽  
Petroleum Industry ◽  
Experimental Results ◽  
Numerical Code ◽  
Drag Coefficients ◽  
Vortex Induced Vibration ◽  
Wake Interference ◽  
Water Depths ◽  
Made In

The offshore petroleum industry has great technological challenges as new field discoveries are made in increasing water depths. Risers of systems having little space between its elements, subjected to current reach static deflections that depend on the wakes formed by the each riser. Depending on the relative position, each riser will be submitted to a stronger or weaker effect from each neighbor. This work presents results from experiments with flexible jumpers submitted to current. The clashing between the lines caused by the wake interference is the focus of the work. The work presents results in terms of minimum distance between the jumpers comparing experimental results to a numerical code that applies automatically the Huse’s formula for the drag coefficients. It also discusses the validity of this theory. As expected, during the tests the jumpers presented Vortex Induced Vibration (VIV), VIV under Interference (VIV-UI) and friction after contact. The results can be extrapolated to real cases and shows the possibility of clashing on closely spaced systems, putting in evidence other phenomena related to it.

Interference Between Risers

2007 ◽  
Author(s):  
Ricardo Franciss ◽  
Andre´ Fujarra
Keyword(s):  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Maximum Amplitude ◽  
Elastic Base ◽  
Drag Coefficients ◽  
Vortex Induced Vibration ◽  
Two Degrees Of Freedom ◽  
Towing Tank ◽  
Lift And Drag ◽  
Made In

This article shows the results of the tests of interference between rigid risers, in relation of Vortex Induced Vibration (VIV), made in the Institute de Pesquisas Tecnolo´gicas do Estado de Sa˜o Paulo (IPT), Brazil. It was tested several conditions with different arrangements with two cylinders in tandem and side by side positions, with different distances between them. The models were installed in an elastic base with two degrees of freedom for each cylinder. The stiffness and the natural frequencies were calibrated to have the maximum amplitude of VIV within the possible range of velocities in the IPT towing tank. The final lift and drag coefficients were measured, for one cylinder with and without strakes and for two cylinders. All these data are used in Riser Analyses giving more real results in relation of VIV analysis, clashing and interference between risers.

scholarly journals On the development of a nonlinear time-domain numerical method for describing vortex-induced vibration and wake interference of two cylinders using experimental results

2021 ◽  
Author(s):  
Milad Armin ◽  
Sandy Day ◽  
Madjid Karimirad ◽  
Mahdi Khorasanchi
Keyword(s):  
Time Domain ◽  
Hydrodynamic Force ◽  
Maximum Amplitude ◽  
Added Mass ◽  
Duffing Equation ◽  
Experimental Results ◽  
Interference Phenomenon ◽  
Vortex Induced Vibration ◽  
Coupled Equations ◽  
Wake Interference

AbstractA nonlinear mathematical model is developed in the time domain to simulate the behaviour of two identical flexibly mounted cylinders in tandem while undergoing vortex-induced vibration (VIV). Subsequently, the model is validated and modified against experimental results. Placing an array of bluff bodies in proximity frequently happens in different engineering fields. Chimney stacks, power transmission lines and oil production risers are few engineering structures that may be impacted by VIV. The coinciding of the vibration frequency with the structure natural frequency could have destructive consequences. The main objective of this study is to provide a symplectic and reliable model capable of capturing the wake interference phenomenon. This study shows the influence of the leading cylinder on the trailing body and attempts to capture the change in added mass and damping coefficients due to the upstream wake. The model is using two coupled equations to simulate the structural response and hydrodynamic force in each of cross-flow and stream-wise directions. Thus, four equations describe the fluid–structure interaction of each cylinder. A Duffing equation describes the structural motion, and the van der Pol wake oscillator defines the hydrodynamic force. The system of equations is solved analytically. Two modification terms are added to the excitation side of the Duffing equation to adjust the hydrodynamic force and incorporate the effect of upstream wake on the trailing cylinder. Both terms are functions of upstream shedding frequency (Strouhal number). Additionally, the added mass modification coefficient is a function of structural acceleration and the damping modification coefficient is a function of velocity. The modification coefficients values are determined by curve fitting to the difference between upstream and downstream wake forces, obtained from experiments. The damping modification coefficient is determined by optimizing the model against the same set of experiments. Values of the coefficients at seven different spacings are used to define a universal function of spacing for each modification coefficient so that they can be obtained for any given distance between two cylinders. The model is capable of capturing lock-in range and maximum amplitude.

scholarly journals Helical growth during the phototropic response, avoidance response, and in stiff mutants of Phycomyces blakesleeanus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Joseph K. E. Ortega ◽  
Revathi P. Mohan ◽  
Cindy M. Munoz ◽  
Shankar Lalitha Sridhar ◽  
Franck J. Vernerey
Keyword(s):  
Avoidance Response ◽  
Experimental Results ◽  
Sensory Transduction ◽  
Growth Responses ◽  
Phycomyces Blakesleeanus ◽  
Sensory Stimuli ◽  
Phototropic Response ◽  
Biophysical Models ◽  
Helical Growth ◽  
Made In

AbstractThe sporangiophores of Phycomyces blakesleeanus have been used as a model system to study sensory transduction, helical growth, and to establish global biophysical equations for expansive growth of walled cells. More recently, local statistical biophysical models of the cell wall are being constructed to better understand the molecular underpinnings of helical growth and its behavior during the many growth responses of the sporangiophores to sensory stimuli. Previous experimental and theoretical findings guide the development of these local models. Future development requires an investigation of explicit and implicit assumptions made in the prior research. Here, experiments are conducted to test three assumptions made in prior research, that (a) elongation rate, (b) rotation rate, and (c) helical growth steepness, R, of the sporangiophore remain constant during the phototropic response (bending toward unilateral light) and the avoidance response (bending away from solid barriers). The experimental results reveal that all three assumptions are incorrect for the phototropic response and probably incorrect for the avoidance response but the results are less conclusive. Generally, the experimental results indicate that the elongation and rotation rates increase during these responses, as does R, indicating that the helical growth steepness become flatter. The implications of these findings on prior research, the “fibril reorientation and slippage” hypothesis, global biophysical equations, and local statistical biophysical models are discussed.

Numerical investigation of the propagation of shock waves in rigid porous materials: development of the computer code and comparison with experimental results

1996 ◽  
Vol 324 ◽  
pp. 163-179 ◽  
Author(s):  
A. Levy ◽  
G. Ben-Dor ◽  
S. Sorek
Keyword(s):  
Porous Materials ◽  
Initial Conditions ◽  
Computer Code ◽  
Experimental Results ◽  
Numerical Code ◽  
Materials Development ◽  
Numerical Predictions ◽  
Wide Range ◽  
Dimensional Version ◽  
The One

The governing equations of the flow field which is obtained when a thermoelastic rigid porous medium is struck head-one by a shock wave are developed using the multiphase approach. The one-dimensional version of these equations is solved numerically using a TVD-based numerical code. The numerical predictions are compared to experimental results and good to excellent agreements are obtained for different porous materials and a wide range of initial conditions.

Performance and Boundary Layer Development of a High Turning Compressor Cascade at Sub- and Supercritical Flow Conditions

2012 ◽  
Author(s):  
Christoph Bode ◽  
Dragan Kožulović ◽  
Udo Stark ◽  
Heinz Hoheisel
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Density Ratio ◽  
Boundary Layer Separation ◽  
Experimental Results ◽  
Numerical Code ◽  
Compressor Cascade ◽  
Boundary Layer Development ◽  
Boundary Layer Interaction ◽  
Inlet Angle

Based on current numerical investigations, the present paper reports on new Q2D midspan-calculations and results for the well known high turning (Δβ = 50°) supercritical (Ma1 = 0.85) compressor cascade V2. A Q2D treatment of the problem was chosen in order to avoid the difficult modelling of the porous endwalls in a corresponding 3D approach. All simulations were done with the RANS solver TRACE of the DLR Cologne in combination with modified versions of the Wilcox turbulence model and Langtry/Menter transition model. Existing experimental Q2D midspan-results for the V2 compressor cascade were used to demonstrate the improved ability of the numerical code to determine performance characteristics, blade pressure and Mach number distributions as well as boundary layer parameter and velocity distributions. The loss characteristics show minimum loss regions when plotted against inlet angle or axial velocity density ratio. Within these regions, increasing with decreasing Mach number, the experimental results were adequately predicted. Outside these regions it turned out difficult to reproduce the experimental results due to increasing boundary layer separation. Furthermore, the prediction quality was very good for subsonic conditions (Ma1 = 0.60) and still reasonable for supercritical conditions (Ma1 = 0.85), where shock/boundary layer interaction made the prediction more difficult.

Caveats and Pitfalls of Production Forecast Uncertainty Analysis Using Design of Experiments

2021 ◽  
Author(s):  
Boxiao Li ◽  
Hemant Phale ◽  
Yanfen Zhang ◽  
Timothy Tokar ◽  
Xian-Huan Wen
Keyword(s):  
Design Of Experiments ◽  
Uncertainty Analysis ◽  
History Matching ◽  
Petroleum Industry ◽  
Production Forecast ◽  
Forecast Uncertainty ◽  
Field Development ◽  
Development Alternatives ◽  
Modeling Principles ◽  
Made In

Abstract Design of Experiments (DoE) is one of the most commonly employed techniques in the petroleum industry for Assisted History Matching (AHM) and uncertainty analysis of reservoir production forecasts. Although conceptually straightforward, DoE is often misused by practitioners because many of its statistical and modeling principles are not carefully followed. Our earlier paper (Li et al. 2019) detailed the best practices in DoE-based AHM for brownfields. However, to our best knowledge, there is a lack of studies that summarize the common caveats and pitfalls in DoE-based production forecast uncertainty analysis for greenfields and history-matched brownfields. Our objective here is to summarize these caveats and pitfalls to help practitioners apply the correct principles for DoE-based production forecast uncertainty analysis. Over 60 common pitfalls in all stages of a DoE workflow are summarized. Special attention is paid to the following critical project transitions: (1) the transition from static earth modeling to dynamic reservoir simulation; (2) from AHM to production forecast; and (3) from analyzing subsurface uncertainties to analyzing field-development alternatives. Most pitfalls can be avoided by consistently following the statistical and modeling principles. Some pitfalls, however, can trap experienced engineers. For example, mistakes made in handling the three abovementioned transitions can yield strongly unreliable proxy and sensitivity analysis. For the representative examples we study, they can lead to having a proxy R2 of less than 0.2 versus larger than 0.9 if done correctly. Two improved experimental designs are created to resolve this challenge. Besides the technical pitfalls that are avoidable via robust statistical workflows, we also highlight the often more severe non-technical pitfalls that cannot be evaluated by measures like R2. Thoughts are shared on how they can be avoided, especially during project framing and the three critical transition scenarios.

Seismic Loss Mechanisms

Geophysics ◽  
1981 ◽  
Vol 46 (5) ◽  
pp. 806-808 ◽  
Author(s):  
N. C. Dutta
Keyword(s):  
Wave Attenuation ◽  
Dynamic Properties ◽  
Petroleum Industry ◽  
Seismic Energy ◽  
Seismic Wave Attenuation ◽  
Seismic Loss ◽  
Research Workshop ◽  
Rock Specimens ◽  
Made In ◽  
Loss Mechanisms

In the petroleum industry there is considerable current interest in understanding the causes of seismic energy loss. During the past few years, considerable progress has been made in the field of seismic wave attenuation as a result of both controlled laboratory studies of the static and the dynamic properties of rock specimens and theoretical modeling. During the 49th Annual International Meeting of the Society of Exploration Geophysicists in New Orleans, a research workshop on Seismic Loss Mechanisms was organized. The purpose of this workshop was to assess current understanding of the physical processes that cause attenuation of seismic energy. The workshop, organized by Kenneth Larner of Western Geophysical and the author, featured a multispeaker format involving invited papers from both industry and academia. The presentations were followed by discussions lasting approximately 90 minutes which included the speakers, the audience, and a panel of experts in the field of seismology.

ADDITIONAL HEAT FLOW DETERMINATIONS IN THE AREA OF MOULD BAY, ARCTIC CANADA

1966 ◽  
Vol 3 (2) ◽  
pp. 237-246 ◽  
Author(s):  
W. S. B. Paterson ◽  
L. K. Law
Keyword(s):  
Heat Flow ◽  
Canadian Arctic ◽  
The Arctic ◽  
Canadian Arctic Archipelago ◽  
General Area ◽  
Geothermal Heat ◽  
Field Methods ◽  
The Mean ◽  
Water Depths ◽  
Made In

Seven determinations of geothermal heat flow were made in the general area of southern Prince Patrick Island in the Canadian Arctic Archipelago. Measurements were made from sea ice in water depths of between 200 and 600 m. The mean heat flow for the two stations on the continental shelf in the Arctic Ocean was 0.46 ± 0.08 μcal cm−2 s−1. The mean heat flow for the five stations in the channels to the east of Mould Bay was 1.46 ± 0.16 μcal cm−2 s−1. The instrument and field methods are described. Errors due to the instrument and to the environment are discussed.

scholarly journals Hemispherical–directional reflectance measurements of natural snow in the 0.9–1.45 μm spectral range: comparison with adding–doubling modelling

1998 ◽  
Vol 26 ◽  
pp. 59-63 ◽  
Author(s):  
Claude Sergent ◽  
Catherine Leroux ◽  
Evelyne Pougatch ◽  
Florence Guirado
Keyword(s):  
Temperature Gradient ◽  
Spectral Range ◽  
Experimental Results ◽  
Natural Snow ◽  
Reflectance Measurements ◽  
Directional Reflectance ◽  
Made In

The authors present the results of snow hemispherical–directional reflectance measurements on natural snow in the 0.9–1.45 μm spectral range. The measurements were made in a cold laboratory on snow collected in the field. Some of the samples have been subjected to controlled metamorphism in the laboratory before measurements were made. In the first part, the adding–doubling model, experimental assumptions and methodology are described. In the second part, experimental results are discussed and compared with theoretical values for different typical snow types and for different stages of snow evolution when subjected to temperature-gradient and wetness metamorphisms.

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