CFD modeling of bubbling fluidized beds using OpenFOAM®: Model validation and comparison of TVD differencing schemes

The two-fluid model with kinetic theory of granular flow is implemented into the open source CFD package OpenFOAM^®. The effect of total variation diminishing (TVD) convection schemes is investigated by simulating two bubbling fluidized beds. Five TVD schemes are employed to discretize the convection terms of phase velocity and solid volume fraction. Simulated results of the two test cases give reasonable agreement with the experimental data in the literature. For the discretization of the phase velocity convection terms, the five schemes give quite similar time-averaged radial profiles of particle axial velocity. The predicted bubbles in the bed with a central jet are not influenced by the different schemes. For the discretization of the solid volume fraction convection terms, the limitedLinear01, Sweby01 and vanLeer01 schemes give the converged and reasonable solutions, whereas the SuperBee01 and MUSCL01 schemes diverge the solutions. When using the faceLimited gradient scheme the convection scheme becomes more diffusive.     

基于OpenFOAM的化学危害扩散预测求解器的开发与验证

化学危害扩散预测是精确化防护保障的关键基础,解决化学危害扩散预测的关键是如何精确表达下垫面、建筑物、湍流对危害物的扩散影响机理。立足化学危害扩散预测实际需求,在计算流体力学软件OpenFOAM中创新性植入信息融合模块、数据同化模块、源项反演模块和智能寻优算法,设计开发适用于化学危害扩散预测的求解器ChdpFOAM,并对ChdpFOAM求解器的适用性进行实验分析。研究结果表明：ChdpFOAM求解器在下垫面相对平坦、建筑物少的区域预测精度较高,在建筑物密集区域预测精度有所下降;相对于PISOFOAM求解器,ChdpFOAM求解器的计算精度约提升6%,计算效率下降约32.57%,具备良好的可移植性和拓展性,为化学危害扩散预测提供了一种新思路与方法。     

减摇水舱液体晃荡固有特性数值与模型试验

为研究某海洋工程船舶减摇水舱液体晃荡的固有周期及其阻尼特性,设计有机玻璃模型,开展模型试验。利用开源软件OpenFOAM开发基于两相流求解器InterFOAM的计算程序包,对该减摇水舱模型液体晃荡的固有周期和阻尼进行数值预报,并讨论模型网格尺寸、水舱阻尼板、水舱液面高度等因素对固有特性的影响,预报结果与模型试验结果吻合较好。研究成果可为减摇水舱的设计提供技术指导。     

基于OpenFOAM的连铸方坯凝固过程数值模拟

针对连铸大方坯凝固过程数值分析问题,探讨了开源软件OpenFOAM程序设计和边界条件处理的方法。利用OpenFOAM的扩展性,对其基本导热方程求解器laplacianFoam进行修改,满足了连铸坯传热凝固计算的要求。用所开发的程序计算了低碳钢连铸大方坯的凝固过程,并通过实际生产现场测温和射钉实验,验证了数值计算的可靠性。     

Bipolar corona assisted jet flow for fluidic application

In this paper, we present a study on a jet flow, assisted by low net charge ion wind from bipolar corona discharge setup. The ion wind is simultaneously generated from both positive and negative electrodes placed in parallel, adding momentum to the bulk flow directed alongside the electrodes and focused in the middle of interelectrode space. The electrodes are connected to a single battery-operated power source in a symmetrical arrangement, where the electrode creating charged ions of one polarity also serves as the reference electrode to establish the electric field required for ion creation by the opposite electrode, and vice versa. Multiphysics numerical simulation is carried out with programmable open source OpenFOAM, where the measured current-voltage is applied as a boundary condition to simulate the electrohydrodynamics flow. The jet flow inside the device is verified by hotwire anemometry using hotwires embedded within the device, with the measured values in good agreement with simulation. The corona discharge helped to focus the jet and increased the flow peak velocity from 1.41 m/s to 2.42 m/s with only 27.1 mW of consumed discharge power. The device is robust, ready-to-use and minimal in cost. In addition, as the oppositely charged corona flows are self-neutralized, the generated air flow remains neutral and therefore does not attach to a particular target, which expands the application range. These are important features, which can contribute to the development of multi-axis fluidic inertial sensors, fluidic amplifiers, micro blowers, gas mixing, coupling and analysis with space constraints and/or where neutralized discharge process is required, such as circulatory flow heat transfer or the formation of low charged aerosol for inhalation and charged particle deposition.     

Evaluation of thermal and energy consumption behavior of novel foamed copper slag based geopolymer masonry blocks

The building sector is focused on adopting passive design strategies to reduce the energy needs of the building envelope. Currently there has been lack of research related to the understanding of thermal and energy efficiency performance of foamed geopolymer based material. In this regard, this research provides a solution of thermally efficient wall material developed from copper industry by-product (copper slag). All the performance criteria (i.e. physical, mechanical and thermal) of the developed foamed copper slag geopolymer (FCSG) blocks as a building block was found to be in compliance with the performance of standard commercial product (i.e., autoclave aerated block). Further, the numerical analysis of the developed FCSG material is performed and the conjugate heat transfer through three different solid-wall zones to the fluid domain is perceived. The incompressible conjugate heat transfer solver is developed in the open-source computational fluid dynamics (CFD) tool OpenFOAM to perform the present numerical analysis. It is noted that the temperature in the fluid zone for the FCSG layer attained less than 300 (K) however, for the red clay bricks it reaches 302 (K). Hence, the thermal efficiency of the FCSG incorporated insulation layer reduces the heat transmission from outdoor to indoor, consequently improving the comfortable environment of occupants. Further, the developed blocks were subjected to simulation study using eQuest tool to understand the influence of its thermal characteristics on energy demands. The study found that the yearly energy savings was found to be 7.5% in comparison to commercially available clay bricks. Also, the cost savings can reach up to 8.94% during the peak summer month and 7.4% annually. Thus, the developed blocks emphasize waste utilization, providing better indoor thermal for occupant and energy efficiency benefits for end-users. Thus, achieving overall sustainability as a building envelope component.     

Design and numerical investigation of a circular microchannel for particle/cell separation using dielectrophoresis

Precisely separating particles/cells with different sizes and physical properties has been an interest for point-of-care diagnostics and personalized treatment. Dielectrophoresis (DEP) is widely known as a powerful and non-invasive technique to separate particles and cells. This paper presents a comprehensive numerical investigation of particle/cell separation in circular microchannels using DEP. First, the geometrical parameters of the circular microchannel affecting DEP force are determined by performing an analytical solution. Then, by developing a solver in OpenFOAM, the effect of these parameters on particles deflection is investigated. According to the results, two different circular microchannels are presented to investigate the continuous separation of bio-particles (based on their physical properties) and polystyrene particles (based on their size). The results showed that a minimum voltage of 7, 9, and 12 V is required to achieve 100 % purity and separation efficiency for separating red blood cells from MDA-MB-231 cancer cells at the flow rate of 0.5, 1.0, and 1.5 µl/min, respectively. Also, the efficient separation of 5 and 10 µm polystyrene particles at the flow rate of 0.1 µl/min is possible only at the voltage of 9 V. The results of this numerical study can be useful for the fabrication of an optimal microdevice for the continuous DEP separation of particles and cells.     

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.     

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.