Open Field Operation And Manipulation Research Articles

Simulating cross-scale flow dynamics around offshore monopile foundations with a GFD-CFD coupled model

Flow dynamics are complex and undergo significant impact from offshore engineering infrastructures, such as wind turbines, involving interactions across different temporal and spatial scales. Individual numerical models of geophysical fluid dynamics (GFD) or computational fluid dynamics (CFD) face challenges in accurately representing these dynamics. To effectively capture the three-dimensional cross-scale flow around offshore infrastructures, we propose a generalized coupling framework that integrates the unstructured-grid Finite-Volume Community Ocean Model (FVCOM) for GFD and the Open Field Operation and Manipulation (OpenFOAM) for CFD. With the validation against the flume experiment, the common-boundary nesting method was developed to allow an accurate representation of flow dynamics around offshore hydraulic infrastructures. Idealized monopile foundation experiments demonstrate the model's capability to capture the formation of Karman vortex street, rotating horseshoe vortex under realistic astronomical tidal conditions. Application of this coupling framework to the offshore wind farm in Yangjiang, China, reveals flow direction lagging of 15° in the wake of a monopile under diurnal tide. This coupling approach, leveraging the strengths of both CFD and GFD models, provides a universal downscaling methodology in geophysical conditions, for a better understanding of the impact of offshore hydraulic infrastructures on the surrounding environment and further planning offshore engineering projects.

Natural convection of water-based nanofluids in three-dimensional enclosures

The single-phase approach, in which nanofluids are treated as pure fluids assuming that the solid and liquid phases are in local thermal and hydrodynamic equilibrium, has been used with good results to simulate forced convection flows. Conversely, its extension to natural convection has revealed to be more problematic, as the obtained numerical results are substantially different from the experimental data, mainly due to the effects of the slip motion occurring between the suspended nanoparticles and the base liquid, whose consequent nonuniform distribution of the solid phase concentration can significantly affect both heat and momentum transfer. In the present article, a two-phase model based on a double-diffusive approach is proposed to study the natural convection flows of water-based metal oxide nanofluids inside cylindrical and rectangular enclosures heated and cooled at their opposite sides with the scope to reproduce a number of experimental data-sets available in the literature. Given the assumption of local thermal equilibrium between nanoparticles and host liquid, and considering the Brownian and thermophoretic diffusion as responsible for causing significant relative velocity between the solid and liquid phases, the governing equations are solved by a control-volume numerical method implemented using the open-source platform OpenFOAM (Open Field Operation and Manipulation). It has been found that the nanoparticle diffusion gives the major contribution to the decrease of the heat transfer rate red usually observed experimentally in natural convection flows of nanofluids inside differentially-heated enclosures. This means that a two-phase model, in conjunction with proper correlations for the evaluation of the nanofluid effective physical properties, must be necessarily enforced to obtain reliable results for many engineering applications.

Turbomachinery GPU Accelerated CFD: An Insight into Performance

Driven by the emergence of Graphics Processing Units (GPUs), the solution of increasingly large and intricate numerical problems has become feasible. Yet, the integration of GPUs into Computational Fluid Dynamics (CFD) codes still presents a significant challenge. This study undertakes an evaluation of the computational performance of GPUs for CFD applications. Two Compute Unified Device Architecture (CUDA)-based implementations within the Open Field Operation and Manipulation (OpenFOAM) environment were employed for the numerical solution of a 3D Kaplan turbine draft tube workbench. A series of tests were conducted to assess the fixed-size grid problem speedup in accordance with Amdahl’s Law. Additionally, tests were performed to identify the optimal configuration utilizing various linear solvers, preconditioners, and smoothers, along with an analysis of memory usage.

Hydrodynamic performance analysis of a new hybrid wave energy converter system using OpenFOAM

In this research study, a newly proposed hybrid device of Wave Energy Converters (WEC) is investigated by considering computational fluid dynamic (CFD)-based numerical wave tanks (NWTs). The open-source CFD code solver, OpenFOAM (Open Field Operation and Manipulation) is implemented, which is numerically solved the Reynolds-averaged Navier–Stokes (RANS) equations to simulate the two-phase flow. The hybrid system consists of an Oscillating Water Column (OWC) and a point absorber (Wavestar) device installed in a shared platform. The main goal is to recognize how wave diffractions caused by the adjacent floating body could affect the rate of power absorption by the Fixed-OWC. This aim is followed by a 2D numerical analysis of three different installation configurations, variable intervals between the Wavestars' buoy and the Fixed-OWCs' front wall, in four different wavelengths with and without Power Take-Off (PTO). Finally, the efficiency characteristics of the integrated system such as free surface velocity and air pressure within the chamber, besides floating body motions are investigated and compared for the hybrid system. Although the overall assessment for 28 different case studies reveals an efficiency reduction in some cases, the superiority of this hybrid plan is recording several incremental efficiency rates.

Numerical study of a novel ventilation system added to the structure of a catamaran for different slamming conditions using OpenFOAM

Large-size catamarans' structural behavior is sensitive and critical during the slamming phenomenon. “Ventilation pipes” within the center bow structure are proposed to discharge these cumulative pressure and related loads. The validation case is comprising two different simulation schemes, static and dynamic wedge. First, the appropriate method is chosen based on the accuracy and needed computational running time criteria. The numerical solution approach solves the RANS equation using the Open Field Operation and Manipulation (OpenFOAM) library called “InterFoam and OverInterDyMFoam for static and dynamic mesh respectively. Totally three different impact conditions with four different impact velocities (12 case studies) were considered for the case with added ventilation pipes (amended hull) and the standard model (parent-hull). Apart from the limitation of the proposed plan which is discussed, the results indicate that the recorded pressure and total force decreases by about (15%–50%), and (5%–25%) respectively.

The Effect of Pore-Scale Two-Phase Flow on Mineral Reaction Rates

In various natural and engineered systems, mineral–fluid interactions take place in the presence of multiple fluid phases. While there is evidence that the interplay between multiphase flow processes and reactions controls the evolution of these systems, investigation of the dynamics that shape this interplay at the pore scale has received little attention. Specifically, continuum scale models rarely consider the effect of multiphase flow parameters on mineral reaction rates or apply simple corrections as a function of the reactive surface area or saturation of the aqueous phase, without developing a mechanistic understanding of the pore-scale dynamics. In this study, we developed a framework that couples the two-phase flow simulator of OpenFOAM (open field operation and manipulation) with the geochemical reaction capability of CrunchTope to examine pore-scale dynamics of two phase flow and their impacts on mineral reaction rates. For our investigations, flat 2D channels and single sine wave channels were used to represent smooth and rough geometries. Calcite dissolution in these channels was quantified with single phase flow and two phase flow at a range of velocities. We observed that the bulk calcite dissolution rates were not only affected by the loss of reactive surface area as it becomes occupied by the non-reactive non-aqueous phase, but also largely influenced by the changes in local velocity profiles, e.g., recirculation zones, due to the presence of the non-aqueous phase. The extent of the changes in reaction rates in the two-phase systems compared to the corresponding single phase system is dependent on the flow rate (i.e., capillary number) and channel geometry, and follows a non-monotonic relationship with respect to aqueous saturation. The pore-scale simulation results highlight the importance of interfacial dynamics in controlling mineral reactions and can be used to better constrain reaction rate descriptions in multiphase continuum scale models. These results also emphasize the need for experimental studies that underpin the development of mechanistic models for multiphase flow in reactive systems.

Experiment and RANS modeling of solitary wave impact on a vertical wall mounted on a reef flat

A series of two-dimensional flume experiments were carried out to study turbulent bore impact on the vertical wall mounted on a reef flat. Turbulent bores were generated by solitary waves propagating on typical fringing reef profiles with and without reef crest. The idealized reef model has a 1:4 face slope and a long reef flat, with an impermeable vertical wall at the end. The solitary wave height varies from 14.1% to 30.0% of the water depth to cover a range of nonlinear wave conditions. Datasets of free surface elevation and flow velocity along fringing reef profiles and pressure on the vertical wall are acquired. Corresponding RANS (Reynolds-averaged Navier–Stokes)-type simulations are performed utilizing the open-source CFD (Computational Fluid Dynamics) OpenFOAM (Open Field Operation and Manipulation) package with the SST k−ω turbulence closure solver and validated using experimental data. The characteristics of the main hydrodynamic and impact processes are examined in detail. The predictive capability of OpenFOAM and three existing formulas for calculating the maximum lateral force are evaluated using measured data. A new predictive equation for peak pressure along the vertical wall is also proposed to achieve better agreement with the experimental data.

Equation for modelling energy transfers in multi-phase flows through porous media, optimised for liquid composite moulding processes

Liquid Composite Moulding LCM processes are increasingly popular in the aerospace and related industries for the production of high quality composite parts. Filling simulations are often used in the design of moulds for LCM processes for efficient and complete filling of the mould. This paper proposes an energy balance equation for modelling energy interactions in a typical LCM process for implementation in Computational Fluid Dynamics (CFD) tools such as Open Field Operation and Manipulation (OpenFOAM). The derivation of the energy balance is first described in detail, followed by a brief description of an additional equation to be solved to find the degree of cure for simulations involving a chemically reactive resin. For a preliminary validation, a simplified version of the energy equation is implemented in OpenFOAM and simulation results are compared to experiments. The temperatures predicted by the simulations are seen to closely match the experimentally observed temperatures.

OpenFOAM solver of the methane behaviour near the coal mine tunnelling face and its application

Abstract The methane near a tunnelling face seriously affects production safety in coal mines. A model considering methane seepage, adsorption, desorption and coal damage processes was established in this research. The open field operation and manipulation (OpenFOAM) solver was compiled to numerically solve the established model. The model is validated against data published in a previous theoretical study. The solver was used to investigate the effect of different parameters on methane emission regularity. This solver demonstrates that the effects of the original stress, coal cohesion and coal internal friction angle on the methane emission rate are limited, but their effects on the width of the fractured zone and effective stress are great. The effects of the initial methane pressure and coal adsorption parameters on the methane emission rate are also notable, but their effects on the width of the fractured zone and effective stress are limited.

An integral approach to simulate three-dimensional flow in and around a ventilated U-shaped chironomid dwelled burrow

Tube dwelling of chironomids often dominates benthic communities in freshwater ecosystems with high population density and pumping rates. This strongly enhances exchange across the sediment-water interface and impacts biogeochemical processes. Such processes are investigated by tracking the flow initiated by chironomid’s pumping through and around burrows using laboratory and computer models. We used modeling and experimental results of other authors considering U-shaped burrows embedded in the sediment to improve process-understanding and prove the plausibility of an integral modeling approach. In contrast to coupled models of pipe (burrow), surface water (overlying water column) and groundwater flow (surrounding sediment), we present a novel high-resolution integral formulation for the porous medium-surface water domain (called porousInter as part of OpenFOAM (Open Field Operation and Manipulation)). This approach solves the extended version of the Navier-Stokes equations allowing simultaneous flow simulation in the burrow, the overlying water column and the surrounding sediment to better account for feedback effects between the sediment and surface water. Using similar model setup as of a coupled approach, we performed scenarios of flow through burrow and sediment triggered by pumping in the center of the burrow. Plausible agreement of our integral model with results of a coupled model and experimental results was obtained when comparing flow patterns around the burrows, between two burrow branches and at burrow inlet and outlet.

Efficiency Assessment of an Amended Oscillating Water Column Using OpenFOAM

Oscillating water column (OWC) is an advanced form of wave energy converter (WEC). This study aims at improving the efficiency of an amended OWC through a novel methodology for simulating several vertical plates within the chamber. This paper provides a numerical investigation considering one, two, three, and four vertical plates. The open field operation and manipulation (OpenFOAM) solver is verified based on the Reynolds-Averaged Navier–Stokes (RANS) equation. Results show the number and the position of plates where the convertor’s efficiency improves. The work undertaken here also revealed a reduction in the net force imposed on the convertor’s structure, especially the front wall. Consequently, adding plates acquires more efficiency with lower force on the system.

Study of three-dimensional air gun bubble pulsation and the surrounding fluid pressure with finite volume method

Air guns can be used for seabed resource exploration, shock testing of naval vessels, polar ice breaking, etc. The study of air-gun bubble pulsation and near-field pressure is of great significance. In order to analyze the dynamic behavior and pressure characteristics of air gun bubble in detail and quantitatively, this study used the finite volume and volume of fluid methods to establish a compressible, three-dimensional air-gun bubble model in OpenFOAM (Open Field Operation and Manipulation). The characteristics of air-gun bubble pulsation and the surrounding flow-field pressures produced using various opening areas and forms were investigated. The maximum horizontal bubble displacement, main primary pulse, and bubble pulse were analyzed quantitatively. When the air-gun opening area was small, the bubble expansion time was short and the collapse time was long. The bubble surface was mostly smooth during the first bubble pulsation cycle. The bubble was nearly spherical when at its maximum volume. When collapse was nearly complete, an annular jet formed in the annular-opening air gun bubble, and four jets were formed from the four-opening air-gun bubble. The system with the largest air-gun opening area had the largest pressure wave primary pulse.

Three-dimensional topology optimization of thermal-fluid-structural problems for cooling system design

In the present study, a topology optimization method of thermal-fluid-structural problems is researched to design the three-dimensional heat sink with load-carrying capability. The optimization is formulated as a mean temperature minimization problem controlled by Navier-Stokes (N-S) equations as well as energy balance and linear elasticity equations. In order to prevent an unrealistic and low load-carrying design, the power dissipation of the fluid device and the normal displacement on the load-carrying surface are taken as constraints. A parallel solver of multi-physics topology optimization problems is built-in Open Field Operation And Manipulation (OpenFOAM) software. The continuous adjoint method is adopted for the sensitivity analysis to make the best use of built-in solvers. With the developed tool, the three-dimensional (3D) thermal-fluid topology optimization is studied. It is found that the Darcy number, which is suitable for fluid design, may cause severe problems in thermal-fluid optimization. The structural features of 3D thermal-fluid-structural problems are also investigated. The “2D extruded designs” are helpful to improve the structural stiffness, and channels with a larger aspect ratio in high-temperature areas improve the cooling performance.

Multi-Scale Modeling of Anode-Supported Solid Oxide Fuel Cell

Three-dimensional comprehensive model of micro-scale transport in positive electrode/ electrolyte/negative electrode(PEN) and macro-scale transport in gas channel of anode supported SOFCs (solid oxide fuel cells) is developed in object-oriented CFD code Open Field Operation and Manipulation (OpenFOAM). The numerical procedure consists of calculations of complex phenomena which are fully coupled together with electrochemical reaction kinetics, mass balance, and energy balance, interacting between porous PEN structure and fluid gas channel. Computational fluid dynamics (CFD) was performed in flow channels with calculations of mass balance and continuum micro-scale model were used to predict the electrochemical characteristics in PEN. The distributions of current density and mass fraction are employed to suggest a dependency. To validate our numerical model, we compare the simulated results with experimental data at intermediate temperatures. This study provides detailed information of heat and mass transport phenomena with electro-chemical characteristics for intermediate temperature SOFCs.

Dynamic mesh re‐partitioning considering iterative convergence rate for multiphase flows in OpenFOAM

SummaryFor parallel multiphase flows, the core procedure is solving linear systems using preconditioned iterative methods, and the iterative convergence rate is crucial to the overall efficiency. How the mesh is partitioned influences the iterative convergence rate. However, the numerical characteristics of the linear systems vary significantly along with the time steps because of the dramatic change of the flow fields. Traditional static mesh partition cannot guarantee a good convergence feature throughout the simulation. A dynamic mesh re‐partitioning scheme MDMRPar (Multiphase Dynamic Mesh Re‐Partitioning) is proposed and implemented in OpenFOAM (Open Field Operation And Manipulation). MDMRPar employs a new surface field to record the linear system information in every time step. For simple multiphase problems with topo‐invariant mesh, MDMRPar periodically adopts the numerical information from the previous time step and calculates a weighted graph from the mesh topology in a straightforward way. For multiphase flows using adaptive mesh refinement method, a coarse graph with vertex weights is built based on the mesh topology and refinement history. The numerical information on the surface field is integrated into the coarse graph as edge weights. In both cases, weighted graphs are re‐partitioned by ParMetis, a general multi‐level parallel graph re‐partitioning package. Experimental results on three multiphase flows show that MDMRPar significantly outperforms the traditional partitioning/re‐partitioning schemes both in the iterative convergence rate and the total simulation time.

Numerical Modeling of Anode-Supported Solid Oxide Fuel Cell Using Openfoam

Three-dimensional comprehensive model of micro-scale transport in PEN (positive electrode/ electrolyte/negative electrode) and macro-scale transport in gas channel of anode supported SOFCs (solid oxide fuel cells) is developed in object-oriented CFD code Open Field Operation and Manipulation (OpenFOAM). The numerical procedure consists of calculations of complex phenomena which are fully coupled together with electrochemical reaction kinetics, mass balance, and energy balance, interacting between porous PEN structure and fluid gas channel. The Computational fluid dynamics (CFD) was performed in flow channels with calculations of mass balance and continuum micro-scale model were used to predict the electrochemical characteristics in PEN. The temperature distributions, temperature profiles, and standard deviations are investigated at different average current densities to evaluate the uniformity. The distributions of current density and mass fraction are employed to suggest a dependency. This study provides detailed information of heat and mass transport phenomena with electro-chemical characteristics for intermediate temperature SOFCs

Analysis of natural convection in heat sink using OpenFOAM and experimental tests

A transient three-dimensional natural convection problem in heat sinks with rectangular fins positioned horizontally was studied using the software OpenFOAM (Open Field Operation and Manipulation). OpenFOAM is based on the Finite Volume Method for the discretization of the governing equations and was used to solve the three-dimensional equations of continuity, momentum and energy. These computational simulations were done with the PIMPLE solution algorithm for decoupling the equations. The NusseltCalc tool was used in the post-processing to obtain Nusselt number. The results of Nusselt number, temperature, velocity and vorticity fields were obtained. The temperature results were also obtained by numerical probes and compared with experimental and analytical results; presenting differences lower than 0.7%. The results of the average Nusselt number, $$ \overline{Nu} $$ , and the average heat transfer coefficient by convection, $$ \overline{h} $$ , numerically obtained with OpenFOAM were compared with the experimental and with those obtained from empirical correlation. All these results obtained with OpenFOAM presented good accordance with experiments and literature with differences lower than 10%. Uncertainty analyses were also carried out in order to prove the quality of the results and they presented differences lower than 5%. In addition, a Nusselt number correlation is proposed for Rayleight number in the range of 4.6 × 104 < Ra < 5.8 × 105.

Unsteady Simulation of a Full-Scale CANDU-6 Moderator with OpenFOAM

Three-dimensional moderator flow in the calandria tank of CANDU-6 pressurized heavy water reactor (PHWR) is computed with Open Field Operation and Manipulation (OpenFOAM), an open-source computational fluid dynamics (CFD) code. In this study, numerical analysis is performed on the real geometry model including 380 fuel rods in the calandria tank with the heat-source distribution to remove uncertainty of the previous analysis models simplified by the porous media approach. Realizable k-ε turbulence model is applied, and the buoyancy due to temperature variation is considered by Boussinesq approximation for the incompressible single-phase Navier-Stokes equations. The calculation results show that the flow is highly unsteady in the moderator. The computational flow visualization shows a circulation of flow driven by buoyancy and asymmetric oscillation at the pseudo-steady state. There is no region where the local temperature rises continuously due to slow circulating flow and its convection heat transfer.

Numerical Investigation of the Wave/Current–Induced Responses of Transient Soil around a Square Mono-Pile Foundation

Duan, L.; Jeng, D.-S.; Wang, S., and Zhu, B., 2019. Numerical investigation of the wave/current–induced responses of transient soil around a square mono-pile foundation. Journal of Coastal Research, 35(3), 625–636. Coconut Creek (Florida), ISSN 0749-0208.A mono-pile foundation is a commonly used supporting base for marine infrastructure in shallow water, such as offshore wind turbine foundations and cross-sea bridges and platforms. Sea floor instability around a pile foundation has attracted much attention among offshore geotechnical engineers. In this paper, a three-dimensional numerical model for wave–seabed–structure interactions is proposed using open field operation and manipulation (OpenFOAM). Unlike previous studies, currents are included in the proposed model and applied to a square cross-section mono-pile foundation. In the model, the flow motion is described by the Reynolds-averaged Navier–Stokes (RANS) equation and k–ϵ turbulence model, and the water free surface is tracked using the volume of fluid (VOF) method. Meanwhile, the soil response is determined by the Biot's poro-elastic equation (u–p approximation), in which the accelerations of the soil displacements are included. After the model is validated with the previous laboratory experiments, it is further used to investigate the transient soil response around the square mono-pile foundation. Numerical results demonstrate that the cross-section shape has significant influence on the distribution of wave/current–induced transient pore pressure but little influence on the maximum soil liquefaction depth. On the other hand, both the current velocity and the seabed permeability can greatly affect the maximum soil liquefaction depth and slightly affect the distribution of pore pressure. Furthermore, the cross-section dimension significantly affects both the maximum soil liquefaction depth and the distribution of the pore pressure around a mono-pile foundation.

Investigation of the impact of planetary boundary layer turbulence on the performance of onshore wind farm

Abstract In recent years, wind power has become the fastest growing renewable energy. In the wind power generation, wind energy assessment is also a crucial one, it is directly related to the layout and power generation forecast of a wind farm. Before a wind park is constructed, a site with high mean annual wind speeds in hub height has to be found. To analyse the wind resources at a potential wind park site the three-dimensional wind field has to be simulated. In this paper, accurate and reliable Computational Fluid Dynamics (CFD) simulations of wind flow over natural complex terrain in northern of Morocco have been performed. The Geographic Information System (GIS) is used to generate contour elevation data before can be directly imported into CAD to generate terraced three-dimensional topographic map of test area. The site is characterized regarding its flow features and the suitability for a wind turbine test field. An improved delayed detached eddy simulation (IDDES) was employed using measurement data to generate generic turbulent inflow. A good agreement of the wind profiles between the different approaches was reached. The terrain slope leads to a speed up, a change of turbulence intensity as well as to flow angle variations. For the numerical simulation the Open Source Computational Fluid Dynamics (CFD) Toolbox OpenFOAM (Open Field Operation and Manipulation) was used. It is a compressible finite volume flow solver using block-structured grids and featuring a wide range of turbulence models. This type of analysis may help in preliminary assessments and expedite the site selection process.