Multiphase Flow Simulation of Subsea Pipeline Leakage Detected by Acoustic Emission Method

Subsea Pipelines ◽

Abstract Subsea pipelines are the heart of the oil transportation system. Oil leakages from subsea pipelines is one of the principal risks associated with oil transportation. An experimental test rig was designed to identify a range of scenarios that could cause leakage, and consequently marine pollution. The Acoustic Emission (AE) technique was employed to sense the flow behaviour inside the pipeline through quantifying and analysing key parameters, such as; energy, amplitude, and the counts number. Although, the size and location of the oil leakage were acquired experimentally utilising highly sensitive acoustic sensors. Two series of numerical simulations utilising Computational Fluid Dynamics (CFD) – Reynolds-Averaged Navier-Stokes (RANS) model, were performed to accurately predict the rate of the oil spill and the corresponding trajectory to the free-surface at Reynolds number Re range from 0.3702 × 103 to Re 9.775 × 103 for flow inside pipeline. The computed results showed good agreement with the experimental data. The results demonstrated that the current experimental measurements analysis could determine the leakage location and the leakage hole capacity, then the numerical calculations could predict the leaked oil volume and the leaked oil route to prevent oil diffusion and mitigate its harmful impact. The findings of this work is a step forward for preventing and controlling oil pollution to protect the marine environment.

Mechanism and Flow Control on the Mismatching of Impeller and Vaned Diffuser Caused by Inlet Prewhirl for Centrifugal Compressors

Volume 2D: Turbomachinery ◽

10.1115/gt2016-56244 ◽

2016 ◽

Cited By ~ 1

Author(s):

Qiangqiang Huang ◽

Xinqian Zheng ◽

Aolin Wang

Keyword(s):

Flow Control ◽

Control Method ◽

Three Dimensional ◽

Navier Stokes ◽

Vaned Diffuser ◽

Inlet Distortion ◽

Stagger Angle ◽

Good Agreement ◽

Matching Relation

Air often flows into compressors with inlet prewhirl, because it will obtain a circumferential component of velocity via inlet distortion or swirl generators such as inlet guide vanes. A lot of research has shown that inlet prewhirl does influence the characteristics of components, but the change of the matching relation between the components caused by inlet prewhirl is still unclear. This paper investigates the influence of inlet prewhirl on the matching of the impeller and the diffuser and proposes a flow control method to cure mismatching. The approach combines steady three-dimensional Reynolds-averaged Navier-Stokes (RANS) simulations with theoretical analysis and modeling. The result shows that a compressor whose impeller and diffuser match well at zero prewhirl will go to mismatching at non-zero prewhirl. The diffuser throat gets too large to match the impeller at positive prewhirl and gets too small for matching at negative prewhirl. The choking mass flow of the impeller is more sensitive to inlet prewhirl than that of the diffuser, which is the main reason for the mismatching. To cure the mismatching via adjusting the diffuser vanes stagger angle, a one-dimensional method based on incidence matching has been proposed to yield a control schedule for adjusting the diffuser. The optimal stagger angle predicted by analytical method has good agreement with that predicted by computational fluid dynamics (CFD). The compressor is able to operate efficiently in a much broader flow range with the control schedule. The flow range, where the efficiency is above 80%, of the datum compressor and the compressor only employing inlet prewhirl and no control are just 25.3% and 31.8%, respectively. For the compressor following the control schedule, the flow range is improved up to 46.5%. This paper also provides the perspective of components matching to think about inlet distortion.

ICCM2015: A Comparison of RANS and LES Computational Methods in Analyzing Ventilation Flow Through a Room Fitted with a Two-Sided Windcatcher

International Journal of Computational Methods ◽

10.1142/s0219876217500219 ◽

2017 ◽

Vol 14 (03) ◽

pp. 1750021 ◽

Cited By ~ 2

Author(s):

A. Niktash ◽

B. P. Huynh

Keyword(s):

Natural Ventilation ◽

Three Dimensional ◽

Navier Stokes ◽

Interior Space ◽

Eddy Simulation ◽

Large Eddy ◽

Flow Through ◽

Cfd Method ◽

A windcatcher is a structure for providing natural ventilation using wind power; it is usually fitted on the roof of a building to exhaust the inside stale air to the outside and supplies the outside fresh air into the building interior space working by pressure difference between outside and inside of the building. In this paper, the behavior of free wind flow through a three-dimensional room fitted with a centered position two-canal bottom shape windcatcher model is investigated numerically, using a commercial computational fluid dynamics (CFD) software package and LES (Large Eddy Simulation) CFD method. The results have been compared with the obtained results for the same model but using RANS (Reynolds Averaged Navier–Stokes) CFD method. The model with its surrounded space has been considered in both method. It is found that the achieved results for the model from LES method are in good agreement with RANS method’s results for the same model.

CFD Investigation on Hydrodynamic Resistance of a Novel Subsea Shuttle Tanker

Journal of Marine Science and Engineering ◽

10.3390/jmse9121411 ◽

2021 ◽

Vol 9 (12) ◽

pp. 1411

Author(s):

Yihan Xing ◽

Marek Jan Janocha ◽

Guang Yin ◽

Muk Chen Ong

Keyword(s):

High Efficiency ◽

Navier Stokes ◽

Hydrodynamic Resistance ◽

Detached Eddy Simulation ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation ◽

Large Eddy ◽

Carbon Dioxide Co2 ◽

Subsea Pipelines

The Subsea Shuttle Tanker (SST) was proposed by Equinor as an alternative to subsea pipelines and surface tankers for the transportation of liquid carbon dioxide (CO2) from existing offshore/land facilities to marginal subsea fields. In contrast to highly weather-dependent surface tanker operations, the SST can operate in any condition underwater. Low resistance is paramount to achieving maximum range. In this paper, the resistance of the SST at an operating forward speed of 6 knots (3.09 m/s) and subject to an incoming current velocity of 1 m/s is computed using Computational Fluid Dynamics (CFD). The Delayed Detached Eddy Simulation (DDES) method is used. This method combines features of Reynolds-Averaged Navier–Stokes Simulation (RANS) in the attached boundary layer parts at the near-wall regions, and Large Eddy Simulation (LES) at the unsteady, separated regions near to the propeller. The force required to overcome forward resistance is calculated to be 222 kN and agrees well with experimental measurements available in the open literature. The corresponding power consumption is calculated to be 927 kW, highlighting the high efficiency of the SST. The method presented in this paper is general and can be used for resistance optimization studies of any underwater vessel.

Numerical Flow Prediction in Inlet Pipe of Vertical Inline Pump

Journal of Fluids Engineering ◽

10.1115/1.4038533 ◽

2017 ◽

Vol 140 (5) ◽

Cited By ~ 8

Author(s):

Christopher Stephen ◽

Shouqi Yuan ◽

Ji Pei ◽

Xing Cheng G

Keyword(s):

Stokes Equations ◽

Reverse Flow ◽

Pressure Coefficient ◽

Navier Stokes ◽

Mean Flow ◽

Inlet Pipe ◽

Navier Stokes Equations ◽

The Mean ◽

For a pump, the inlet condition of flow determines the outlet conditions of fluid (i.e., energy). As a rule to minimize the losses at the entry of pump, the bends should be avoided as one of the methods. But for the case of vertical inline pump, it is unavoidable in order to save the space for installation. For the purpose of investigation in inlet pipe of vertical inline pump, the unsteady Reynolds-averaged Navier–Stokes equations are solved using the computational fluid dynamics (CFD) code. The results have been shown that there is a good agreement between the performance characteristics obtained from the simulation and experiments. The velocity coefficient from the simulation along the inlet pipe sections is well matched with the theoretical values and found to have variation near the exit of inlet pipe. The pressure and velocity coefficients studies depict the flow physics at each section along with the study of helicity at the exit of inlet pipe to determine the recirculation effects. It is observed that the vortices associated with the motion of the particles are moved toward the surfaces and are more intense than the mean flow. The trends of pressure coefficient at the exit of inlet pipe were addressed with reference to the various flow rates for eight set of radial lines. Hence, this work concludes that for inlet pipe, the generation of circulation was due to the stream path and the reverse flow from the impeller and was reconfirmed with the literature.

A Comparison Between CFD, Potential Theory and Model Tests for Oscillating Aircushion Supported Structures

Volume 1: Offshore Technology ◽

10.1115/omae2009-79766 ◽

2009 ◽

Author(s):

J. L. F. van Kessel ◽

F. Fathi

Keyword(s):

Potential Theory ◽

Stokes Equations ◽

Linear Method ◽

Model Tests ◽

Navier Stokes ◽

Navier Stokes Equations ◽

University Of Technology ◽

Good Agreement ◽

Theory And Model

This contribution presents a comparison between Computational Fluid Dynamics (CFD), potential theory and model tests for an oscillating aircushion supported structure. The linear method was developed at Delft University of Technology and uses a linear adiabatic law to describe the air pressure inside the cushion. In this method, the structure and the water surface within the aircushion are modelled by means of panel distributions representing oscillating sources. The CFD solver is the commercial software CFX which solves the whole flow field using Reynolds Averaged Navier Stokes Equations (RANSE). The free surface is modelled by a Volume of Fluid (VOF) approach. The results in this paper show a good agreement between experimental results and numerical results of both methods for aircushion pressure variations, added mass, damping and wave elevations inside the aircushion. As such it is validated that the behaviour of an aircushion supported structure subjected to forced heave oscillations can be well predicted by both CFD and potential theory.

Development and Design of a Centrifugal Compressor Volute

International Journal of Rotating Machinery ◽

10.1155/ijrm.2005.190 ◽

2005 ◽

Vol 2005 (3) ◽

pp. 190-196 ◽

Cited By ~ 21

Author(s):

Cheng Xu ◽

Michael Müller

Keyword(s):

Centrifugal Compressor ◽

Stokes Equations ◽

Flow Simulation ◽

Navier Stokes ◽

Vaneless Diffuser ◽

Navier Stokes Equations ◽

Flow Mechanisms ◽

Compressor Efficiency ◽

Design Guidance ◽

The volute is one of the key components of a centrifugal compressor. The design of the volute not only impacts the compressor efficiency but also influences the operating range. The detailed flow simulation presented here helps to better understand the volute flow mechanisms and provide design guidance in volute design to meet performance goals. In this study, the viscous Navier-Stokes equations are used to simulate the flow inside the vaneless diffuser and volute. The detailed flow structures for different volute tongue geometries are studied in detail. The numerical calculations are compared with experimental data and good agreement is found. The results also suggest direction for further investigations in volute design.

Experimental and Numerical Model Investigations of the Underwater Towing of a Subsea Module

Journal of Marine Science and Engineering ◽

10.3390/jmse7110384 ◽

2019 ◽

Vol 7 (11) ◽

pp. 384 ◽

Cited By ~ 1

Author(s):

Yingfei Zan ◽

Ruinan Guo ◽

Lihao Yuan ◽

Zhaohui Wu

Keyword(s):

Drag Force ◽

Stokes Equations ◽

Resistance Coefficient ◽

Navier Stokes ◽

Cfd Simulations ◽

Lateral Direction ◽

Navier Stokes Equations ◽

Numerical Result ◽

In underwater towing operations, the drag force and vertical offset angle of towropes are important considerations when choosing and setting up towing equipment. The aim of this paper is to study the variation in drag force, vertical offset angle, resistance, and attitude for towing operations with a view to optimizing these operations. An underwater experiment was conducted using a 1:8 scale physical model of a subsea module. A comprehensive series of viscous Computational Fluid Dynamics (CFD) simulations were carried out based on Reynolds-averaged Navier–Stokes equations for uniform velocity towing. The results of the simulation were compared with experimental data and showed good agreement. Numerical results of the vorticity field and streamlines at the towing speeds were presented to analyze the distribution of vortexes and flow patterns. The resistance components were analyzed based on the numerical result. It was found that the lateral direction was a better direction for towing operations because of the smaller drag force, resistance, and offset angle. Similar patterns and locations of streamlines and vortexes were present in both the longitudinal and lateral directions, the total resistance coefficient decreases at a Reynolds number greater than that of a cylinder.

The curled wake model: A three-dimensional and extremely fast steady-state wake solver for wind plant flows

10.5194/wes-2020-86 ◽

2020 ◽

Cited By ~ 3

Author(s):

Luis A. Martínez-Tossas ◽

Jennifer King ◽

Eliot Quon ◽

Christopher J. Bay ◽

Rafael Mudafort ◽

...

Keyword(s):

Steady State ◽

Wind Power ◽

Power Plants ◽

Stokes Equations ◽

Computational Cost ◽

Three Dimensional ◽

Flow Simulation ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Abstract. This work focuses on minimizing the computational cost of steady-state wind power plant flow simulations that take into account wake steering physics. We present a simple wake solver with a computational cost on the order of seconds for large wind plants. The solver uses a simplified form of the Reynolds-averaged Navier-Stokes equations to obtain a parabolic equation for the wake deficit of a wind plant. We compare results from the model to supervisory control and data acquisition (SCADA) from the Lillgrund wind plant; good agreement is obtained. Results for the solver in complex terrain are also shown. Finally, the solver is demonstrated for a case with wake steering showing good agreement with power reported by large-eddy simulations. This new solver minimizes the time – and therefore the related cost – it takes to conduct a steady-state wind plant flow simulation to about a second on a personal laptop. This solver can be used for different applications including wake steering for wind power plants and layout optimization, and it will soon be available within the FLOw Redirection and Induction in Steady State (FLORIS) framework.

Simulation of Unsteady Flow Around a Cylinder

Wasit Journal of Engineering Sciences ◽

10.31185/ejuow.vol3.iss2.38 ◽

2015 ◽

Vol 3 (2) ◽

pp. 28-49

Author(s):

Ridha Alwan Ahmed

Keyword(s):

Stokes Equations ◽

Lift Coefficient ◽

Reynolds Numbers ◽

Mean Value ◽

Navier Stokes ◽

Cylinder Surface ◽

Navier Stokes Equations ◽

Flow Around A Cylinder ◽

Numerical Grid ◽

In this paper, the phenomena of vortex shedding from the circular cylinder surface has been studied at several Reynolds Numbers (40≤Re≤ 300).The 2D, unsteady, incompressible, Laminar flow, continuity and Navier Stokes equations have been solved numerically by using CFD Package FLUENT. In this package PISO algorithm is used in the pressure-velocity coupling. The numerical grid is generated by using Gambit program. The velocity and pressure fields are obtained upstream and downstream of the cylinder at each time and it is also calculated the mean value of drag coefficient and value of lift coefficient .The results showed that the flow is strongly unsteady and unsymmetrical at Re>60. The results have been compared with the available experiments and a good agreement has been found between them

Numerical Modeling of Evolution of Boundary Between Incompressible Gas and Liquid in Two-Dimensional Region

Proceedings of the Mavlyutov Institute of Mechanics ◽

10.21662/uim2006.1.020 ◽

2006 ◽

Vol 4 ◽

pp. 224-236

Author(s):

A.S. Topolnikov

Keyword(s):

Numerical Modeling ◽

Interphase Boundary ◽

Incompressible Liquid ◽

Stokes Equations ◽

Numerical Code ◽

Navier Stokes ◽

Two Phase ◽

Navier Stokes Equations ◽

Incompressible Media ◽

The paper is devoted to numerical modeling of Navier–Stokes equations for incompressible media in the case, when there exist gas and liquid inside the rectangular calculation region, which are separated by interphase boundary. The set of equations for incompressible liquid accounting for viscous, gravitational and surface (capillary) forces is solved by finite-difference scheme on the spaced grid, for description of interphase boundary the ideology of Level Set Method is used. By developed numerical code the set of hydrodynamic problems is solved, which describe the motion of two-phase incompressible media with interphase boundary. As a result of numerical simulation the solutions are obtained, which are in good agreement with existing analytical and experimental solutions.