A Preliminary Study on the Interaction Between Slug Flow and Vortex Induced Vibration in Fatigue Life of Submarines Pipelines

2010 ◽  
Author(s):  
Armando Blanco ◽  
Euro Casanova
Keyword(s):  
Fatigue Life ◽  
Slug Flow ◽  
Structural Model ◽  
Fluid Model ◽  
Dynamical Behavior ◽  
Practical Interest ◽  
Flow Density ◽  
Wake Oscillator ◽  
Marine Current ◽  
Flow Induced Vibrations

Flow induced vibrations is a very important subject that should be carefully considered when facilities to transport hydrocarbons from marine sub-sea to shore line are designed. In particular, interaction between internal pipeline flow and external marine currents on horizontal, inclined or vertical (i.e. risers) pipelines need to be considered to properly estimate their fatigue life. Between these two form of excitations a coupling of resonances may appear, thus producing fatigue life predictions different from those calculated when each excitation is considered separately. In this paper a fluid-structural model for analyzing the dynamical behavior of a riser subjected to simultaneous internal slug flow and an external marine current uniform flow was developed. The fluid model was based on the classical wake oscillator model. A numerical model based on the finite difference method was implemented for the structure. Different tests cases were modeled to analyze the riser dynamics for a typical field case, when marine current velocity is constant. Preliminary results show that, in some cases of practical interest, the dynamical behavior of the riser could be influenced by the slug flow and the predicted fatigue life may be different from those predicted when each flow is considered separately. Additionally, results show that study of different slug flow scenarios may be simplified considering a monophasic flow whose density is equivalent to that of the average slug flow density.

Numerical Modeling of the Dynamical Interaction Between Slug Flow and Vortex Induced Vibration in Horizontal Submarine Pipelines

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Boris M. Bossio V. ◽  
Armando J. Blanco A. ◽  
Euro L. Casanova M.
Keyword(s):  
Fatigue Life ◽  
Flow Regime ◽  
Vortex Shedding ◽  
Slug Flow ◽  
Fluid Model ◽  
Reference Value ◽  
Dynamical Interaction ◽  
Vortex Induced Vibration ◽  
Resonance Effects ◽  
Cyclic Damage

Fatigue life of submarines pipelines is known to depend on many factors, e.g., materials, spanning length, vortex induced vibration (VIV), pipe soil-interaction, etc. In the case of VIV, the external flow due to marine currents can generate the well known alternate vortex shedding regime. In this regime, a time-varying pressure distribution over the surface of the pipeline imposes forces upon the pipeline itself, thus producing vibration with a defined frequency. On the other hand, in recent years some authors have shown that slug flow regime may produce a cyclic damage that could reduce in a significant way the fatigue life of submarine pipelines, thus constituting a governing mechanism in their design. In slug flow regime, slugs traveling in the pipe act as moving gravity loads for the pipeline structure, producing a dynamic response, especially important for the free spans. If both frequencies of the before mentioned effects are closer and, in addition, are in the same range of the natural frequency of the pipeline span, resonance effects can be expected to be reinforced and drastic changes in the dynamics of the pipeline could appear. In this work, a first study of the interaction between slug flow induced vibration in horizontal pipelines and cross-flow response due to vortex shedding is presented. The fluid model was based on the classical wake oscillator model. A numerical model based on the finite difference method was implemented for the structure. Two particular extreme cases were modeled to analyze the pipeline dynamics for “small-size” and “large-size” slugs, for a range of marine current velocities. For the case involving small-size slugs, it was observed a near 10% increment in the vibration amplitude (compared to a reference value), while in the case of “large-slugs” the VIV was overweighed by the slug induced vibration (SIV) phenomenon.

Initiation and Statistical Evolution of Horizontal Slug Flow With a Two-Fluid Model

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
A. O. Nieckele ◽  
J. N. E. Carneiro ◽  
R. C. Chucuya ◽  
J. H. P. Azevedo
Keyword(s):  
Experimental Data ◽  
Slug Flow ◽  
Fluid Model ◽  
Subsequent Development ◽  
Complex Flow ◽  
Horizontal Pipes ◽  
Dimensional Version ◽  
Two Fluid Model ◽  
Log Normal ◽  
Two Fluid

In the present work, the onset and subsequent development of slug flow in horizontal pipes is investigated by solving the transient one-dimensional version of the two-fluid model in a high resolution mesh using a finite volume technique. The methodology (named slug-capturing) was proposed before in the literature and the present work represents a confirmation of its applicability in predicting this very complex flow regime. Further, different configurations are analyzed here and comparisons are performed against different sets of experimental data. Predictions for mean slug variables were in good agreement with experimental data. Additionally, focus is given to the statistical properties of slug flows such as shapes of probability density functions of slug lengths (which were represented by gamma and log-normal distributions) as well as the evolution of the first statistical moments, which were shown to be well reproduced by the methodology.

A Phenomenological Model for Vortex-Induced Motions of the Monocolumn Platform and Comparison With Experiments

2009 ◽  
Author(s):  
Guilherme F. Rosetti ◽  
Rodolfo T. Gonc¸alves ◽  
Andre´ L. C. Fujarra ◽  
Kazuo Nishimoto ◽  
Marcos D. Ferreira
Keyword(s):  
Time Domain ◽  
Phenomenological Model ◽  
Structural Model ◽  
Design Phase ◽  
Van Der Pol ◽  
Floating Structures ◽  
Towing Tank ◽  
Wake Oscillator ◽  
Two Degree Of Freedom ◽  
Comparison With Experiments

Vortex-Induced Motions (VIM) of floating structures is a very relevant subject for the design of mooring and riser systems. In the design phase, Spar VIM behavior as well as Semi Submersible and Tension Leg Platform (TLP) flow-induced motions are studied and evaluated. This paper discusses flow-induced behavior on the Monocolumn concept by presenting a phenomenological model and comparing its results with a set of experiments that took place in the IPT Towing Tank - Brazil (September 2008). The experimental results have shown some fundamental differences from previous VIM tests on other units such as Spars. This numerical model attempts to identify these disparities in order to better understand the mechanics of this phenomenon. The model is based on a time-domain, two degree-of-freedom structural model coupled with a van der Pol type wake oscillator. The comparison was performed in order to calibrate the model, to study and better understand the tests results, and finally to identify important aspects to investigate in further experiments.

Blind Identification of Impact Forces From Multiple Remote Vibratory Measurements

2000 ◽  
Author(s):  
J. Antunes ◽  
P. Izquierdo ◽  
M. Paulino
Keyword(s):  
Explicit Knowledge ◽  
Transfer Functions ◽  
Dynamical Behavior ◽  
Practical Interest ◽  
Operating Conditions ◽  
Blind Identification ◽  
Minimum Entropy ◽  
Response Measurement ◽  
Identification Techniques ◽  
The Impact

Abstract Structures and mechanical components are often subjected to impulsive forces. There is a need for identification techniques which enable monitoring of such loads under operating conditions. For safety reasons and convenience, force identification must often be based on response motions sensed at accessible locations, remote from the impact points. In our previous work we presented techniques for the experimental identification of both isolated impacts and complex rattling forces on a beam, generated at a single and also at several impacting supports. The system dynamical behavior was modeled using traveling flexural beam waves. Although successful, these techniques obviously assume a good understanding of the system dynamic parameters. This is not always the case, a fact that highlights the practical interest of blind identification techniques. This relatively recent field, connected with higher-order statistics, avoids any explicit knowledge of the system transfer functions or impulse responses. Our previous work, based on a single response measurement, is extended in this paper to include several simultaneous responses. We develop a multi-trace version of Wiggins minimum-entropy blind deconvolution algorithm. From numerical simulations and experiments, it is shown that the robustness to noise contamination is increased by using multiple response data. These results suggest that blind identification techniques will prove very useful in practical situations.

The Influence of Switch Temperature on Coke Drum Fatigue Life

2010 ◽  
Author(s):  
Fa´bio de Castro Marangone ◽  
Ediberto Bastos Tinoco ◽  
Carlos Eduardo Simo˜es Gomes
Keyword(s):  
Fatigue Life ◽  
Structural Model ◽  
High Stress ◽  
Axial Direction ◽  
Pressure Vessels ◽  
High Stress Concentration ◽  
Short Period ◽  
Bending Stresses ◽  
Switch Temperature ◽  
Lower Temperature

Coke drums are thin-walled pressure vessels that experience severe thermal cycling condition which consists of heating, filling and rapidly cooling the drum in a short period of time. After some years under operation, cracks at the vessel may occur, especially at high stress concentration areas such as the skirt support to shell attachment. During the filling phase of the cycle, when the empty and cooled coke drum is filled with hot oil, the shell and cone temperatures increase rapidly compared to the skirt temperature and the last is pushed outward, since its bottom is at lower temperature and fixed at a concrete base. During quenching (sudden cooling) phase, the coke drum is filled with water at about 80°C and tends to cool faster than the skirt, which is pulled inward until equilibrium is obtained. The skirt expansion and contraction movement results in bending stresses in axial direction on the top of skirt. As lower the switch temperature is, more severe is the bending effect. One of PETROBRAS delayed coke unit presented some operational problems at pre-heating phase, resulting in lower switch temperatures. This paper presents an analysis showing the influence of the switch temperature on coke drum fatigue life. At first, the transient loading conditions were established from thermocouple measurements at skirt attachment weld (hot box region). Later, a transient thermal analysis was performed with FEA and the temperature gradient at the skirt attachment during entire thermal cycle was obtained. The thermal results were then converted to a structural model which was solved for linear elastic stress including other loads such as pressure. Finally, the maximum stress components for both filling and quenching phases were determined and a complete stress range was calculated as per ASME Section VIII, Div 2. The procedure described above was applied for different switch temperatures scenarios in order to show its influence on the fatigue life of the coke drum.

Numerical evaluation of separation efficiency in the diverging T-junction for slug flow

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Faheem Ejaz ◽  
William Pao ◽  
Hafiz Muhammad Ali
Keyword(s):  
Slug Flow ◽  
Design Methodology ◽  
Separation Efficiency ◽  
Fluid Model ◽  
Diameter Ratio ◽  
Maintenance Costs ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
Practical Implications ◽  
High Separation

Purpose Offshore industries encounter severe production downtime due to high liquid carryovers in the T-junction. The diameter ratio and flow regime can significantly affect the excess liquid carryovers. Unfortunately, regular and reduce T-junctions have low separation efficiencies. Ansys as a commercial computational fluid dynamics (CFD) software was used to model and numerically inspect a novel diverging T-junction design. The purpose of diverging T-junction is to merge the specific characteristics of regular and reduced T-junctions, ultimately increasing separation efficiency. The purpose of this study is to numerically compute the separation efficiency for five distinct diverging T-junctions for eight different velocity ratios. The results were compared to regular and converging T-junctions. Design/methodology/approach Air-water slug flow was simulated with the help of the volume of the fluid model, coupled with the K-epsilon turbulence model to track liquid-gas interfaces. Findings The results of this study indicated that T-junctions with upstream and downstream diameter ratio combinations of 0.8–1 and 0.5–1 achieved separation efficiency of 96% and 94.5%, respectively. These two diverging T-junctions had significantly higher separation efficiencies when compared to regular and converging T-junctions. Results also revealed that over-reduction of upstream and downstream diameter ratios below 0.5 and 1, respectively, lead to declination in separation efficiency. Research limitations/implications The present study is constrained for air and water as working fluids. Nevertheless, the results apply to other applications as well. Practical implications The proposed T-junction is intended to reduce excessive liquid carryovers and frequent plant shutdowns. Thus, lowering operational costs and enhancing separation efficiency. Social implications Higher separation efficiency achieved by using diverging T-junction enabled reduced production downtimes and resulted in lower maintenance costs. Originality/value A novel T-junction design was proposed in this study with a separation efficiency of higher than 90%. High separation efficiency eliminates loss of time during shutdowns and lowers maintenance costs. Furthermore, limitations of this study were also addressed as the lower upstream and downstream diameter ratio does not always enhance separation efficiency.

scholarly journals Analysis of Induced Vibrations in Fully-Developed Turbulent Pipe Flow Using a Coupled LES and FEA Approach

2010 ◽  
Author(s):  
Thomas Shurtz ◽  
Daniel Maynes ◽  
Jonathan Blotter
Keyword(s):  
Structural Model ◽  
Fluid Model ◽  
Surface Displacement ◽  
Turbulent Pipe Flow ◽  
Experimental Investigations ◽  
Time Step ◽  
Pipe Surface ◽  
Wall Displacement ◽  
Fully Developed Turbulent Flow ◽  
Pipe Vibration

This paper presents an approach using numerical simulations that have been used to characterize pipe vibration resulting from fully developed turbulent flow in a straight pipe. The vibration levels as indicated by; pipe surface displacement, velocity, and acceleration are characterized in terms of the influences of geometric and material properties of the pipe, and the effects of varying flow velocity, fluid density and viscosity have considered Reynold’s numbers ranging from 9.1×104 – 1.14×106. A large eddy simulation fluid model was coupled with a finite element structural model to simulate the fluid structure interaction using both one-way and two-way coupled techniques. The one-way technique passes the spatially and temporally varying wall pressure from a completed flow solution with fixed wall boundaries to the structural model. The structural model is then solved for wall displacements. The two-way technique involves the additional passing of wall displacement back to the fluid model which is then resolved given the new boundary location. The structural and fluid models are thus continually updated until convergence is reached at each time step. The results indicate a strong nearly quadratic dependence of pipe wall displacement on fluid average velocity. This relationship has also been verified in experimental investigations of pipe vibration. The results also indicate the pipe vibration has a power law type dependence on several variables. Dependencies on investigated variables are non-dimensionalized and assembled to develop a functional relationship that characterizes turbulence induced pipe vibration.

scholarly journals 3-D Geothermal Model of the Lurestan Sector of the Zagros Thrust Belt, Iran

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2140 ◽  
Author(s):  
Matteo Basilici ◽  
Stefano Mazzoli ◽  
Antonella Megna ◽  
Stefano Santini ◽  
Stefano Tavani
Keyword(s):  
Structural Model ◽  
Thermal Structure ◽  
Frictional Heating ◽  
Analytical Calculation ◽  
Geothermal Gradient ◽  
Hydrocarbon Exploration ◽  
Flow Density ◽  
Northwestern Part ◽  
Thrust Belt ◽  
Analytical Methodology

The Zagros thrust belt is a large orogenic zone located along the southwest region of Iran. To obtain a better knowledge of this important mountain chain, we elaborated the first 3-D model reproducing the thermal structure of its northwestern part, i.e., the Lurestan arc. This study is based on a 3-D structural model obtained using published geological sections and available information on the depth of the Moho discontinuity. The analytical calculation procedure took into account the temperature variation due to: (1) The re-equilibrated conductive state after thrusting, (2) frictional heating, (3) heat flow density data, and (4) a series of geologically derived constraints. Both geotherms and isotherms were obtained using this analytical methodology. The results pointed out the fundamental control exerted by the main basement fault of the region, i.e., the Main Frontal Thrust (MFT), in governing the thermal structure of the crust, the main parameter being represented by the amount of basement thickening produced by thrusting. This is manifested by more densely spaced isotherms moving from the southwestern foreland toward the inner parts of orogen, as well as in a lateral variation related with an along-strike change from a moderately dipping crustal ramp of the MFT to the NW to a gently dipping crustal ramp to the SE. The complex structural architecture, largely associated with late-stage (Pliocene) thick-skinned thrusting, results in a zone of relatively high geothermal gradient in the easternmost part of the study area. Our thermal model of a large crustal volume, besides providing new insights into the geodynamic processes affecting a major salient of the Zagros thrust belt, may have important implications for seismotectonic analysis in an area recently affected by a Mw = 7.3 earthquake, as well as for geothermal/hydrocarbon exploration in the highly perspective Lurestan region.

scholarly journals Dissipative unified dark fluid model

2019 ◽  
Vol 28 (09) ◽  
pp. 1950110
Author(s):  
Esraa Elkhateeb
Keyword(s):  
Dark Energy ◽  
Fluid Model ◽  
Dynamical Behavior ◽  
Power Laws ◽  
Viscosity Coefficient ◽  
Distance Modulus ◽  
Effective Equation ◽  
Dark Fluid ◽  
System Solution ◽  
The Universe

We consider a unified barotropic dark fluid model with dissipation. Our fluid asymptotes between two power laws and so can interpolate between the dust and dark energy (DE) equations-of-state at early and late times. The dissipative part is a bulk viscous part with constant viscosity coefficient. The model is analyzed using the phase-space methodology which helps to understand the dynamical behavior of the model in a robust manner without reference to the system solution. The parameters of the model are constrained through many observational constraints. The model is tested through many physical and observational tests. We first considered the model independent [Formula: see text] test. Results for [Formula: see text] are plotted against the BAO data for this quantity from different authors, which shows that the model is consistent with the data points for the full redshift range. The [Formula: see text] statistics results in the value of [Formula: see text] with a [Formula: see text]-value of [Formula: see text]. The Hubble parameter equation is solved numerically and results are plotted against the recent set of Hubble data. The [Formula: see text] test with the Hubble data resulted in the [Formula: see text] value of [Formula: see text] with a [Formula: see text]-value of [Formula: see text]. The distance modulus at different values of redshift is calculated numerically and results are compared to the newest set of SNe Ia data, the Pantheon Sample. We obtained a [Formula: see text] value of [Formula: see text] with a [Formula: see text]-value of [Formula: see text]. These results show that our model is efficiently consistent with observations. The model expectations for the evolution of the universe are also studied by testing the evolution of the deceleration parameter, the density of the universe, and the effective equation-of-state parameter of the model and of its underlying dark energy candidate. The value of the present day viscosity coefficient of the cosmic fluid, [Formula: see text], is estimated. It is found to be [Formula: see text][Formula: see text]Pa[Formula: see text]s. We argue that this model is able to explain the behavior of the universe evolution.

Transient Two-Phase Flow Model for High Viscous Liquids Over Hilly Terrain

2014 ◽  
Author(s):  
Abraham Parra ◽  
Miguel Asuaje
Keyword(s):  
Slug Flow ◽  
Mechanical Design ◽  
Fluid Model ◽  
Process Equipment ◽  
Maximum Deviation ◽  
Multiphase Model ◽  
Viscous Effects ◽  
Hilly Terrain ◽  
Two Phase ◽  
Wide Range

This paper presents the detailed development of a multiphase model to predict the behavior of terrain-induced slugging, influenced by the viscous effects and hilly terrain. Currently, high viscosity heavy crude oil represents most of the available fossil resources. This crude flows inside long and expensive pipelines, usually over hilly terrain, causing the formation of slug flow. A very common flow pattern produces critical effects on pipelines in terms of modelling, mechanical stress, induced oscillations, fatigue, production losses, and other negative effects for the system. An accurate characterization of this pattern may give critical data for the mechanical design of piping systems and provide valuable information for the downstream process equipment selection. At present, most of the existing models to predict the behavior of slug flow neglect relevant parameters such as the effect of liquid viscosity and the effect of topographic terrain profile. The objective of this study is to present a mechanistic fluid model to determine the behavior of slug flow affected by the hilly terrain using viscous fluids. The model predicts the four stages of slug flow proposed by Schmidt et al. [1], and extends these stages to hilly terrain systems. The model is valid for a wide range of fluid viscosities and considers a range of pipe inclinations between 0° and 90°. Model validation with available literature and experimental data, shows a maximum deviation of 6%.

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