A numerical study of partitioned fluid-structure interaction applied to a cantilever in incompressible turbulent flow

This study presents an approach for partitioned fluid-structure interaction (FSI) applied to large structural deformations, where an incompressible turbulent solver is combined with a structural solver. The implementation is based upon two different open-source libraries by using MPI as a parallel communication protocol, the packages and OpenFOAM. FSI is achieved through a strongly-coupled scheme. The solver has been validated against cases with a submerged cantilever in a channel flow to which experiments, numerical calculations and theoretical solutions are available. The verification of the procedure is performed by using a solid-solid interaction (SSI) study. The solver has proven to be robust and has the same parallel efficiency as the fluid and the solid solver stand-alone.     

A Lagrangian cell‐centred finite volume method for metal forming simulation

The current article presents a Lagrangian cell‐centred finite volume solution methodology for simulation of metal forming processes. Details are given of the mathematical model in updated Lagrangian form, where a hyperelastoplastic J₂ constitutive relation has been employed. The cell‐centred finite volume discretisation is described, where a modified discretised is proposed to alleviate erroneous hydrostatic pressure oscillations; an outline of the memory efficient segregated solution procedure is given. The accuracy and order of accuracy of the method are examined on a number of 2‐D and 3‐D elastoplastic benchmark test cases, where good agreement with available analytical and finite element solutions is achieved. Copyright © 2016 John Wiley & Sons, Ltd.     

台阶式地形上双垂板透空系统的水动力学特性

基于开源计算流体动力学软件OpenFOAM中的工具箱waves2Foam,通过在双垂板透空系统下方布置不同尺寸的台阶式地形（潜堤）,对规则波-双垂板-地形耦合系统的水动力学特性进行数值分析. 在不同入射波况作用下,研究双垂板的间距和台阶式地形的尺寸对结构系统前/后的反/透射系数、波能的黏性耗散率及双垂板间的液面相对振动幅值等水动力参数的影响. 此外,探究波浪非线性对相关水动力参数的影响. 结果表明：合理布置台阶式地形尺寸,如令地形的长度与波长的比值约为1.0,能够有效减小双垂板系统的波能反射和透射,并可获得适中的黏性耗散率;地形的存在会加剧双垂板间的液面振动幅度,有效提升两板间的波能捕获能力;波高的增大会造成反射和透射系数的减小,增大黏性耗散率,降低板间液面振动幅值.     

A multi-region and open-source computational fluid dynamic tool for electrochemical systems with three-dimensional electrodes

In this work, a solver, implemented in OpenFOAM, is developed to investigate the mechanisms of ion transport through activated or resistive three-dimensional (3D) electrodes, and also leakage currents in the case of a bipolar connection. The transport model, which accounts for the balance of mass, momentum, species, and electric charge in the fluid, 3D and solid phases, was solved using a multi-region approach. The algorithm permits calculations for a fixed cell potential difference, and also for a current flowing through the cell under galvanostatic control. Analytical models and experimental results of the current and potential distribution are compared with the present tool, obtaining a close agreement between them. The model presented here is supplied as a free source code and can be employed to optimize both cell stack design and system operation conditions.     

SIMULATION OF TANK SLOSHING BASED ON OPENFOAM AND COUPLING WITH SHIP MOTIONS IN TIME DOMAIN

Tank sloshing in ship cargo is excited by ship motions, which induces impact load on tank wall and then affects the ship motion. Wave forces acting on ship hull and the retardation function are solved by using three-dimensional frequency domain theory and an impulse response function method based on the potential flow theory, and global ship motion is examined coupling with nonlinear tank sloshing which is simulated by viscous flow theory. Based on the open source Computational Fluid Dynamics (CFD) development platform Open Field Operation and Manipulation (OpenFOAM), numerical calculation of ship motion coupled with tank sloshing is achieved and the corresponding numerical simulation and validation are carried out. With this method, the interactions of wave, ship body and tank sloshing are completely taken into consideration. This method has quite high efficiency for it takes advantage of potential flow theory for outer flow field and viscous flow theory for inside tank sloshing respectively. The numerical and experimental results of the ship motion agree well with each other.     

URANS simulations of ship motion responses in long-crest irregular waves

In this paper, numerical prediction of ship motion responses in long-crest irregular waves by the URANS-VOF method is presented. A white noise spectrum is applied to generate the incoming waves to evaluate the motion responses. The procedure can replace a decade of simulations in regular wave with one single run to obtain a complete curve of linear motion response, considerably reducing computation time. A correction procedure is employed to adjust the wave generation signal based on the wave spectrum and achieves fairly better results in the wave tank. Three ship models with five wave conditions are introduced to validate the method. The computations in this paper are completed by using the solver naoe-FOAM-SJTU, a solver developed for ship and ocean engineering based on the open source code OpenFOAM. The computational motion responses by the irregular wave procedure are compared with the results by regular wave, experiments and strip theory. Transfer functions by irregular wave closely agree with the data obtained in the regular waves, showing negligible difference. The comparison between computational results and experiments also show good agreements. The results better predicted by CFD method than strip theories indicate that this method can compensate for the inaccuracy of the strip theories. The results confirm that the irregular wave procedure is a promising method for the accurate prediction of motion responses with less accuracy loss and higher efficiency compared with the regular wave procedure.     

基于三种方法的螺旋桨敞水性能数值预报

该文基于三种不同的CFD方法:多重坐标参考系法(MRF)、任意网格界面元法(AMI)和重叠网格方法(Overset)对某一四叶螺旋桨的敞水性能进行数值模拟和预报,并对螺旋桨周围的流场进行了分析。其中,对于任意网格界面元法(AMI)与多重坐标参考系法(MRF),分别采用开源CFD计算软件Open FOAM所提供的求解器pimple Dy MFoam与MRFSimple Foam进行计算;对于重叠网格方法(Overset),采用基于Open FOAM平台开发的具有重叠网格模块的船舶与海洋工程水动力求解器—naoe-FOAM-SJTU进行求解。通过与试验结果的对比以及方法间的比较,验证了三种方法在螺旋桨敞水性能预报中的可靠性和有效性,并总结了各方法的特征与优劣。同时也对螺旋桨附近的流场特征进行了讨论与分析。     

Mixing in a co‐current upflow bubble column reactors with and without internals

Liquid phase mixing is a phenomenon that results mainly due to convective and turbulent flow fields, which are generated by hydrodynamic interactions between the gas and liquid phases within a continuous co‐current upflow bubble column reactor. The extent of liquid phase mixing is usually quantified through the mixing time, or the axial dispersion coefficient. In the present work, the computational fluid dynamics (CFD) simulations for mixing and RTD in a continuous bubble column (with and without internals) are performed by using OpenFOAM 2.3.1. The superficial gas velocities were 0.014, 0.088, and 0.221 m/s and the superficial liquid velocities were 0.005 and 0.014 m/s. The simulations have been performed for three different configurations of the bubble column, that is, (a) an open bubble column, (b) a column with one vertical central rod of 36 mm diameter, (c) a column with the same central rod and four vertical additional rods of 12 mm diameter. The effects of superficial gas and liquid velocities and column internals were investigated on liquid phase mixing and the axial dispersion coefficient. Comparisons have been made between the experimental measurements and the CFD simulations.

     

BIOTC: An open-source CFD code for simulating biomass fast pyrolysis

The BIOTC code is a computer program that combines a multi-fluid model for multiphase hydrodynamics and global chemical kinetics for chemical reactions to simulate fast pyrolysis of biomass at reactor scale. The object-oriented characteristic of BIOTC makes it easy for researchers to insert their own sub-models, while the user-friendly interface provides users a friendly environment as in commercial software. A laboratory-scale bubbling fluidized bed reactor for biomass fast pyrolysis was simulated using BIOTC to demonstrate its capability.     

Implementation of density-based solver for all speeds in the framework of OpenFOAM

In the framework of open source CFD code OpenFOAM, a density-based solver for all speeds flow field is developed. In this solver the preconditioned all speeds AUSM+(P) scheme is adopted and the dual time scheme is implemented to complete the unsteady process. Parallel computation could be implemented to accelerate the solving process. Different interface reconstruction algorithms are implemented, and their accuracy with respect to convection is compared. Three benchmark tests of lid-driven cavity flow, flow crossing over a bump, and flow over a forward-facing step are presented to show the accuracy of the AUSM+(P) solver for low-speed incompressible flow, transonic flow, and supersonic/hypersonic flow. Firstly, for the lid driven cavity flow, the computational results obtained by different interface reconstruction algorithms are compared. It is indicated that the one dimensional reconstruction scheme adopted in this solver possesses high accuracy and the solver developed in this paper can effectively catch the features of low incompressible flow. Then via the test cases regarding the flow crossing over bump and over forward step, the ability to capture characteristics of the transonic and supersonic/hypersonic flows are confirmed. The forward-facing step proves to be the most challenging for the preconditioned solvers with and without the dual time scheme. Nonetheless, the solvers described in this paper reproduce the main features of this flow, including the evolution of the initial transient.