Two-Phase Model for Simulating Current-Induced Scour Beneath Subsea Pipelines at Different Initial Elevations

2018 ◽  
Author(s):  
Jun Y. Lee ◽  
Jasmin B. T. McInerney ◽  
Fauzi A. Hardjanto ◽  
Shuhong Chai ◽  
Remo Cossu ◽  
...  
Keyword(s):  
Numerical Results ◽  
Scour Depth ◽  
Flow Conditions ◽  
Eulerian Model ◽  
Two Phase ◽  
Mesh Dependency ◽  
Steady Current ◽  
Equilibrium Scour Depth ◽  
Subsea Pipelines ◽  
Good Agreement

When a subsea pipeline is laid on an uneven seabed, the pipeline can have an initial elevation, potentially compromising its on-bottom stability; scouring due to flow conditions around the pipe can further exacerbate the problem. We assess the capability of the two-phase Eulerian-Eulerian OpenFOAM solver, twoPhaseEulerFoam, in terms of predicting the equilibrium scour depth beneath a pipe at different initial elevations under a steady current for the live bed condition. The predictions were found to be in good agreement with published experimental and numerical results; however, similar to a recent study involving another two-phase Eulerian-Eulerian model, the scour time scale was under-predicted. The predicted equilibrium scour depth was seen to decrease with an increase in the initial pipe elevation. The numerical results were also compared to predictions that were made using previous empirical equations. The most comprehensive equation to date showed a good agreement with the present numerical results. We conclude that this open-source solver, twoPhaseEulerFoam, can be used to predict the equilibrium scour depth beneath subsea pipelines, with short computation times and negligible mesh dependency.

The Flow Phenomena and the Non-Uniform Filling of the Unvulcanized Rubber in Process of Filling

2009 ◽  
Author(s):  
Shintarou Sakai ◽  
Toru Shigemitsu ◽  
Junichiro Fukutomi ◽  
Tsukasa Matsuoka
Keyword(s):  
Numerical Analysis ◽  
Narrow Channel ◽  
Numerical Results ◽  
Flow Conditions ◽  
Flow Phenomena ◽  
Rubber Product ◽  
Vulcanization Process ◽  
Filling State ◽  
Optimum Flow ◽  
Good Agreement

Rubber products like oil seal are produced by vulcanization molding and the vulcanization molding of rubber product is performed by past experience, trial and error. It is important issues to decrease the product cost, reduce defective products and solve the environmental problems by saving natural resources. If the vulcanization moldings of rubber products are reappeared by computer simulation, it is very useful and it could contribute to solve the above problems. In order to reduce surplus rubber and defective products, numerical analysis of flow phenomena of unvulcanized rubber was performed using commercial software FIDAP. In several types of rubber mold model, the numerical analysis was conducted taken the characteristic of visco-elasticity fluid obtained by an experiment without considering the effect of heat. And experiments were conducted for the comparison of numerical results and actual phenomena. In the experiment, vulcanization process was stopped by arbitrary interval. Then the filling state and the shape of the rubber at each interval are observed in numerical and experiment results. The results showed that the filling state of numerical results represented good agreement with the experimental results. And it was clarified from the numerical analysis that shear stress increased when the unvulcanized rubber flowed in a narrow channel and there was the relation between pressure and velocity. In the present paper, the flow phenomena under the condition of the compression molding are shown and the optimum flow conditions are discussed from the numerical results. Furthermore mechanism of occurrence of defective products is considered with the experimental and the numerical results.

Effect of Reynolds Number on Local Scour Around a Monopile in Steady Current

2019 ◽  
Author(s):  
Xiaofan Lou ◽  
Kaibing Zhang ◽  
Zhenhong Chen
Keyword(s):  
Reynolds Number ◽  
Time Scale ◽  
Time History ◽  
Local Scour ◽  
Circular Cylinders ◽  
Scour Depth ◽  
Clear Water ◽  
Number Range ◽  
Steady Current ◽  
Equilibrium Scour Depth

Abstract The effect of Reynolds number (Re) on the local scour around a monopile encountering steady current was investigated experimentally in a water flume. The experiment was performed using circular cylinders with different diameters under two different freestream velocities, covering both clear-water and live-bed scours and a Reynolds number range of approximately 9,000–60,000. The time-series of the scour depth was recorded during the whole scour process and the scour pit was scanned after the scour process reached equilibrium. Results are presented in terms of the equilibrium scour depth, the time-scale of the scour process and the three-dimensional scour profile at different Reynolds numbers. For both clear-water and live-bed scours, the time history of the scour process indicate that the time-scale becomes larger as Re increases. It is also found that the normalized equilibrium scour depth, as well as the normalized scour radius, decrease with the increasing Re. An empirical equation of the equilibrium scour depth is derived as a function of Reynolds number based on the experimental results so as to better account for Re effect in the scour design.

Prediction of film inversion in two-phase flow in coiled tubes

1992 ◽  
Vol 236 ◽  
pp. 497-511 ◽  
Author(s):  
G. F. Hewitt ◽  
S. Jayanti
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Two Phase Flow ◽  
Thickness Distribution ◽  
Thin Liquid Film ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
New Criterion ◽  
Good Agreement

Depending on the flow conditions, the liquid film in annular two-phase flow in coiled tubes may be pushed towards the outer or the inner side by the centrifugal force. It is important to understand the mechanism of this ‘film inversion’ in order to develop a predictive model for the film thickness distribution. In this paper, this phenomenon is studied analytically, and a new criterion, based on the secondary flow in the thin liquid film, is proposed to predict its occurrence. The criterion shows good agreement with available experimental data. It is suggested that the analytical model can readily be extended to predict the distribution of the film thickness and film flow rate in coiled tubes.

Equilibrium Scour Prediction for Uniform and Non-Uniform Cylindrical Structures Under Clear Water Conditions

2016 ◽  
Author(s):  
Nicholas S. Tavouktsoglou ◽  
John M. Harris ◽  
Richard R. Simons ◽  
Richard J. S. Whitehouse
Keyword(s):  
Experimental Data ◽  
Pressure Gradient ◽  
Euler Number ◽  
Offshore Structures ◽  
Scour Depth ◽  
Flow Conditions ◽  
Mean Flow ◽  
Cylindrical Structures ◽  
Cylindrical Structure ◽  
Equilibrium Scour Depth

Offshore Gravity Base Foundations (GBFs) are often designed with non-uniform cylindrical geometries. Such structures interact with the local hydrodynamics which amplify the adverse dynamic pressure gradient, which is responsible for all flow and scour phenomena including the bed shear stress amplification. In this study a method for predicting the effect non-uniform cylindrical structure geometries have on local scour around offshore structures under the forcing of a unidirectional current is presented. The interaction of the flow field with the sediment around these complex structures is described in terms of non-dimensional parameters that characterize the similitude of water-sediment movement. The paper presents insights in the influence a form of the Euler number has on the equilibrium scour around uniform and non-uniform cylindrical structures. Here the Euler number is defined as the depth averaged pressure gradient (calculated using potential flow theory) divided by the product of the square of mean flow velocity and the fluid density. The insights are confirmed through a series of experiments where the equilibrium scour was monitored for different types of structures and flow conditions. The results of this study show that the Euler number is a more appropriate parameter for describing the scour potential of a structure compared to using the equivalent pile diameter. The experimental data show that an increasing Euler number yields an increase in the non-dimensional equilibrium scour. The results of this study also suggest that an increase in the water depth yields a decrease in the equilibrium scour depth for the conical, cylindrical base structures and truncated cylinders and an increase in the equilibrium scour depth for the uniform cylinders which can also be explained in terms of changes in the Euler number. Finally, the Buckingham π theorem in conjunction with the experimental data was used to derive a simple shape correction factor that could be used to determine the scour depth of a non-uniform cylindrical structure based on the equilibrium scour produced for the same flow conditions by a uniform cylinder.

Two-Phase Critical Flow under Diabatic Conditions

1969 ◽  
Vol 184 (3) ◽  
pp. 127-133
Author(s):  
A. E. Bergles ◽  
J. T. Kelly
Keyword(s):  
Experimental Investigation ◽  
Equilibrium Model ◽  
Small Diameter ◽  
Critical Flow ◽  
Subcooled Boiling ◽  
Flow Conditions ◽  
Two Phase ◽  
Wide Range ◽  
Good Agreement ◽  
Non Equilibrium

This paper summarizes an experimental investigation of steam-water critical flow in heated tubes. A wide range of data was taken for water at pressures below 100 lbf/in2 (abs.) in tubes of small diameter. It is demonstrated that critical flow conditions can occur in subcooled boiling at low exit subcoolings. At equilibrium qualities below about 0·04, the data differ significantly from adiabatic data for a similar exit geometry. The deviations can be explained in terms of the additional non-equilibrium effects present in heated flows. For higher qualities, the diabatic data are in good agreement with adiabatic data, and can be approximately predicted by a slip equilibrium model.

Numerical Investigation of Scour Around Subsea Pipelines Near the Seabed

2019 ◽  
Author(s):  
Guang Yin ◽  
Zhen Cheng ◽  
Shengnan Liu ◽  
Muk Chen Ong
Keyword(s):  
Granular Flow ◽  
Present Model ◽  
Scour Depth ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Simulations ◽  
2D Simulation ◽  
Binary Collisions ◽  
Simulation Results ◽  
Subsea Pipelines

Abstract In the present study, two-phase flow simulations using SedFoam (an open-source multi-dimensional Eulerian two-phase solver based on OpenFOAM) are employed to investigate the scour phenomenon around pipelines in the vicinity of the seabed. A complete transport profile from the immobile bed, to slowly moving quasi-static bed and upper transport layers can be captured by the present model. The fluid Reynolds stress is modeled using the two-phase k-ε model. The particle stresses due to binary collisions and enduring contacts are modeled by kinetic theory for granular flow and a phenomenological frictional model, respectively. The model is first validated through a two-dimensional (2D) simulation of scour around a single pipeline near the seabed. The predicted time-dependent scour profiles as well as the scour depth are compared with the simulation results of Lee et al. (2016) and the experimental data reported by Mao (1986). A numerical experiment is then carried out to investigate the scour around the piggyback near the seabed. The effects of different locations of the small pipeline on the scour depth are studied.

scholarly journals Experimental Investigation of Scour Prediction Methods for Offshore Tripod and Hexapod Foundations

2020 ◽  
Vol 8 (11) ◽  
pp. 856
Author(s):  
Xuan Ni ◽  
Leiping Xue
Keyword(s):  
Laboratory Experiments ◽  
Prediction Methods ◽  
Scour Depth ◽  
Effective Diameter ◽  
Bed Sediment ◽  
Clear Water ◽  
Pile Groups ◽  
Steady Current ◽  
Complex Shapes ◽  
Equilibrium Scour Depth

Scour prediction is essential for the design of offshore foundations. Several methods have been proposed to predict the equilibrium scour depth for monopiles. By introducing an effective diameter, such methods could also be applied to predicting scour depth for pile groups. Yet, there are still difficulties in estimating the equilibrium scour depth of foundations in complex shapes, such as the tripod foundation. This study investigates the clear-water scour around the tripod and hexapod foundations through laboratory experiments, with uniform bed sediment and steady current. Here, the authors propose an approach to calculate the effective diameter for the tripod and hexapod models, which is similarly as for the pile groups. Three widely-used methods in predicting equilibrium scour depth have been evaluated, and the best method is recommended.

On the Propagation Buckling and Effects in Ultra-Long Deep Subsea Pipelines

2011 ◽  
Author(s):  
Hossein Khalilpasha ◽  
Faris Albermani
Keyword(s):  
Experimental Investigation ◽  
Analytical Solution ◽  
Analytical Solutions ◽  
Numerical Results ◽  
Series Of Experiments ◽  
Buckle Propagation ◽  
Subsea Pipelines ◽  
Good Agreement

This paper considers buckling propagation in ultra-long deep subsea pipelines. Experimental investigation of buckle propagation in ultra-deep pipelines was conducted to verify the analytical solutions proposed by the authors in a previous paper [1]. A series of experiments were designed and conducted to calibrate the equations and verify the analytical and numerical results. The tests include tensile coupon tests, ring squash tests and buckle propagation tests on intact and dented Aluminum pipes with three different D/t ratios. The results are in good agreement with the proposed analytical solution.

scholarly journals The Equilibrium Scour Depth around a Pier under the Action of Collinear Waves and Current

2020 ◽  
Vol 8 (1) ◽  
pp. 36 ◽  
Author(s):  
Ainal Hoque Gazi ◽  
Subhrangshu Purkayastha ◽  
Mohammad Saud Afzal
Keyword(s):  
Velocity Profile ◽  
Arbitrary Shape ◽  
Scour Depth ◽  
Mathematical Equation ◽  
Flowing Fluid ◽  
Scour Hole ◽  
Sediment Particles ◽  
Equilibrium Scour Depth ◽  
Work Done ◽  
Good Agreement

In this paper, a mathematical equation is developed for the equilibrium scour depth considering an arbitrary shape of the scour hole around a pier under the action of collinear waves and current. A power-law current velocity profile is assumed for the purpose of the analysis. The equilibrium scour depth is obtained by equating the work done by the flowing fluid while interacting with the pier under the action of the collinear waves and the current and the work done by the total volume of the sediment particles removed from the scour hole, respectively. The equilibrium scour depths predicted by the model show good agreement with the experimental and numerical results available in the literature.

scholarly journals Scour Characteristics and Equilibrium Scour Depth Prediction around Umbrella Suction Anchor Foundation under Random Waves

2021 ◽  
Vol 9 (8) ◽  
pp. 886
Author(s):  
Ruigeng Hu ◽  
Hongjun Liu ◽  
Hao Leng ◽  
Peng Yu ◽  
Xiuhai Wang
Keyword(s):  
Numerical Simulation ◽  
Present Model ◽  
Euler Number ◽  
Horseshoe Vortex ◽  
Scour Depth ◽  
Random Waves ◽  
Depth Prediction ◽  
Equilibrium Scour Depth ◽  
Scour Morphology ◽  
Good Agreement

A series of numerical simulation were conducted to study the local scour around umbrella suction anchor foundation (USAF) under random waves. In this study, the validation was carried out firstly to verify the accuracy of the present model. Furthermore, the scour evolution and scour mechanism were analyzed respectively. In addition, two revised models were proposed to predict the equilibrium scour depth Seq around USAF. At last, a parametric study was carried out to study the effects of the Froude number Fr and Euler number Eu for the Seq. The results indicate that the present numerical model is accurate and reasonable for depicting the scour morphology under random waves. The revised Raaijmakers’s model shows good agreement with the simulating results of the present study when KCs,p < 8. The predicting results of the revised stochastic model are the most favorable for n = 10 when KCrms,a < 4. The higher Fr and Eu both lead to the more intensive horseshoe vortex and larger Seq.

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