An accurate prediction of non-isothermal gas-liquid interfaces in cryogenic two-phase flows is crucial for the high-efficiency energy storage, transportation, and utilization of liquid hydrogen. However, temperature d...
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An accurate prediction of non-isothermal gas-liquid interfaces in cryogenic two-phase flows is crucial for the high-efficiency energy storage, transportation, and utilization of liquid hydrogen. However, temperature difference and interfacial mass and energy transport can change the thermodynamic state of gas-liquid interfaces and thereby impact the distribution. And the lower surface tension coefficient and viscosity of liquid hydrogen, compared to room-temperature fluids, increase the likelihood of the instability and breakage of non- isothermal interfaces. Conventional numerical methods suffer from a scarcity of precision and the propagation of spurious velocities in predicting such flows. In this study, a new numerical framework called cryoFoam was developed based on an open source CFD code OpenFOAM to address the issue of the inaccurate capture of non- isothermal cryogenic interfaces. A practical interface-capturing model involving phase change was implemented to achieve the uniform distribution of surface forces in both gas and liquid phases. The tangential surface force was incorporated into the governing equations to realize thermocapillary convection. The Schrage model, a widely-used phase change model, was employed to deal with condensation and evaporation. The performance of the solver was assessed using five benchmarks which involve thermocapillary flows and phase changes in liquid hydrogen, liquid oxygen, liquid nitrogen, and liquid methane. The results show that the new method can reduce large spurious velocities and prevent the distortion of isotherms near the curved interface in cryogenic fluids. It demonstrates higher precision than the traditional VOF method in predicting cryogenic thermocapillary convection and interfacial energy transport.
This paper analyzes a low-dissipation discretization for the resolution of immiscible, incompressible multiphase flow by means of interface-capturing schemes. The discretization is built on a three-dimensional, unstru...
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This paper analyzes a low-dissipation discretization for the resolution of immiscible, incompressible multiphase flow by means of interface-capturing schemes. The discretization is built on a three-dimensional, unstructured finite-volume framework and aims at minimizing the differences in kinetic energy preservation with respect to the continuous governing equations. This property plays a fundamental role in the case of flows presenting significant levels of turbulence. At the same time, the hybrid form of the convective operator proposed in this work incorporates localized low-dispersion characteristics to limit the growth of spurious flow solutions. The low-dissipation discrete framework is presented in detail and, in order to expose the advantages with respect to commonly used methodologies, its conservation properties and accuracy are extensively studied, both theoretically and numerically. Numerical tests are performed by considering a three-dimensional vortex, an exact sinusoidal function, and a spherical drop subjected to surface tension forces in equilibrium and immersed in a swirling velocity field. Finally, the turbulent atomization of a liquid-gas jet is numerically analyzed to further assess the capabilities of the method. (C) 2017 Elsevier Ltd. All rights reserved.
In this lead paper of the special issue, we provide some comments on challenges and directions in computational fluid-structure interaction (FSI). We briefly discuss the significance of computational FSI methods, thei...
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In this lead paper of the special issue, we provide some comments on challenges and directions in computational fluid-structure interaction (FSI). We briefly discuss the significance of computational FSI methods, their components, moving-mesh and nonmoving-mesh methods, mesh moving and remeshing concepts, and FSI coupling techniques.
Purpose - The purpose of this paper is to find an efficient way by using finite volume method (FM to simulate the aluminum alloy profile extrusion processes. Design/methodology/approach - By assuming isotropic conditi...
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Purpose - The purpose of this paper is to find an efficient way by using finite volume method (FM to simulate the aluminum alloy profile extrusion processes. Design/methodology/approach - By assuming isotropic conditions, the hot aluminum material is described as a non-linear Newtonian fluid material. Semi-implicit method for pressure-linked equations algorithm is used to calculate the physical fields, and the dynamic viscosity is updated then. Volume of fluid method and moving grid method are also used for unsteady flow to catch the free surface of the material and the moving bound. Findings - FVM model in this paper is an accurate and efficient method for the numerical simulation of aluminum profile extrusion processes. Compared with finite element method software, FVM model is both memory and CPU efficient. Practical implications - Provide theoretical reference for sound extrusion process and die designs, which are the key factors to produce desirable products in industrial production. Originality/value - The paper finds an efficient way to introduce the FVM in computational fluid dynamics field into the simulation of the steady and unsteady aluminum alloy profile extrusion processes. It provides a reference for people who are interested in FVM and extrusion processes.
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