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Start Over Descriptor "two-phase flow" Publication Type Reviews
5 results on '"two-phase flow"'

1. A compressible solver for two phase-flows with phase change for bubble cavitation.

Author

Bibal, M., Deferrez, M., Tanguy, S., and Urbano, A.

Subjects
*COMPRESSIBLE flow, *CAVITATION, *PRESSURE drop (Fluid dynamics), *TWO-phase flow, *FLUID flow, *EQUATIONS of state
Abstract

The present work describes the development of a novel fully compressible solver for two-phase flows with liquid-vapour phase change. Phase change phenomena in compressible two-phase flows are driving mechanisms for a multitude of phenomena including cavitation, droplet evaporation in acoustic fields, phase change in closed environments. Those are fundamental for a large number of technological applications including combustion chambers, propellant management in space and submarine engine design. The accurate simulation of phase change phenomena in compressible flows requires a direct numerical solver thermodynamically consistent and able to describe the smallest driving scales and to handle capillary effects. The present solver has these characteristics. It solves the full system of conservation equations for real fluid compressible flows of single species written in primitive variables using a semi-implicit pressure based solver. It leads to the energy equation being a Screened Poisson equation for the pressure that can be solved as a linear system. For the sake of thermodynamic consistency, several cubic equations of state are proposed to describe liquid and vapour phases as well as evolving saturation conditions at the interface. The proposed solver can be considered as an extension of classical incompressible solvers for nucleate boiling based on sharp interface approaches towards configurations with temporally and spatially evolving saturation conditions at the interface. It enables a complete coupling between local liquid-vapour phase change at the interface and pressure variations due to local flow features or time evolving thermodynamic conditions. Its interest is demonstrated with several benchmarks of increasing complexity with an ultimate configuration involving bubble cavitation due to the pressure drop in a convergent pipe. • Solver to simulate phase change phenomena in two-phase compressible flows. • Solver based on a semi-implicit projection method for compressible flows. • Generalized cubic equations of state for liquid, vapour and saturation conditions. • Simulation of phase change induced by pressure and temperature variations. • Example of cavitating bubble in a convergent nozzle. [ABSTRACT FROM AUTHOR]

Published
2024
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2. r.avaflow v1, an advanced open-source computational framework for the propagation and interaction of two-phase mass flows.

Author

Mergili, Martin, Fischer, Jan-Thomas, Krenn, Julia, and Pudasaini, Shiva P.

Subjects
*OPEN source software, *TWO-phase flow, *MASS transfer
Abstract

r.avaflow represents an innovative open-source computational tool for routing rapid mass flows, avalanches, or process chains from a defined release area down an arbitrary topography to a deposition area. In contrast to most existing computational tools, r.avaflow (i) employs a twophase, interacting solid and fluid mixture model (Pudasaini, 2012); (ii) is suitable for modelling more or less complex process chains and interactions; (iii) explicitly considers both entrainment and stopping with deposition, i.e. the change of the basal topography; (iv) allows for the definition of multiple release masses, and/or hydrographs; and (v) serves with built-in functionalities for validation, parameter optimization, and sensitivity analysis. r.avaflow is freely available as a raster module of the GRASS GIS software, employing the programming languages Python and C along with the statistical software R. We exemplify the functionalities of r.avaflow by means of two sets of computational experiments: (1) generic process chains consisting in bulk mass and hydrograph release into a reservoir with entrainment of the dam and impact downstream; (2) the prehistoric Acheron rock avalanche, New Zealand. The simulation results are generally plausible for (1) and, after the optimization of two key parameters, reasonably in line with the corresponding observations for (2). However, we identify some potential to enhance the analytic and numerical concepts. Further, thorough parameter studies will be necessary in order to make r.avaflow fit for reliable forward simulations of possible future mass flow events. [ABSTRACT FROM AUTHOR]

Published
2017
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3. gVOF: An open-source package for unsplit geometric volume of fluid methods on arbitrary grids.

Author

López, Joaquín and Hernández, Julio

Subjects
*LIQUID-liquid interfaces, *MULTIDIMENSIONAL databases, *COMPUTATIONAL fluid dynamics, *TWO-phase flow, *FREE surfaces, *ADVECTION, *LEVEL set methods
Abstract

The gVOF package implements several accurate and efficient geometric volume of fluid (VOF) methods on arbitrary grids, either structured or unstructured with convex or non-convex cells, based on multidimensional unsplit advection and piecewise linear interface calculation (PLIC) schemes, with the purpose of facilitating and extending the use of advanced unsplit geometric VOF methods in new or existing computational fluid dynamics codes. The package includes a complete and self-contained set of routines for VOF initialization, interface reconstruction and fluid advection, and uses as external libraries a set of publicly available in-house tools to perform several analytical and geometrical operations. These operations may involve handling of high-complex non-convex flux polyhedra, even with self-intersecting faces, which are robustly and efficiently treated in this work without the need of costly techniques based on convex decomposition. Results for the accuracy, computational efficiency, and volume (local and global) conservation properties of different combinations of the implemented advection and reconstruction methods are presented for several numerical tests on structured and unstructured grids. An extensive comparison with results obtained by other authors using advanced geometric VOF methods shows the outstanding performance of the gVOF package in terms of efficiency and accuracy. To demonstrate the performance of the package in solving complex two-phase flow problems, the implemented methods are combined with an existing in-house code to simulate the impact of a water drop on a free surface. Program Title: gVOF CPC Library link to program files: https://doi.org/10.17632/9gmn6gsb6p.1 Licensing provisions: GPLv3 Programming language: FORTRAN and C, with C interfaces External routines/libraries: VOFTools (https://doi.org/10.17632/brrgt645bh.3) and isoap (https://doi.org/10.17632/4rcf98s74c.1) libraries Nature of problem: The software package includes efficient and accurate routines for volume of fluid initialization, reconstruction of interfaces and fluid advection on arbitrary grids, either structured or unstructured with convex or non-convex cells, which are used to implement advanced unsplit geometric VOF methods. In particular, the package includes a fluid volume fraction initialization method, six PLIC reconstruction methods and three multidimensional unsplit advection methods. Routines to visualize interfaces and compute reconstruction errors; tests to assess the accuracy, computational efficiency, and volume conservation of the implemented methods for the reconstruction and advection of complex interfaces on arbitrary grids; and a user manual have also been included in the supplied package. Solution method: Basically, the implemented methods, which can be used on grids with polyhedral cells of arbitrary geometry, have the following general characteristics. The methods implemented for fluid volume fraction initialization and reconstruction error calculation are based on a recursive grid refinement procedure to compute the fluid volume bounded by cell edges and an implicitly-defined fluid interface. The six implemented interface reconstruction methods are the following: a least-squares gradient interface reconstruction method; three isosurface-based interface reconstruction methods; an extension to 3D of the iterative Swartz interface reconstruction; and a least-squares fit interface reconstruction method. Three unsplit advection methods, which are based on edge-matched, face-matched and non-matched flux polyhedra and are valid for 3D arbitrary grids, are implemented. All the implemented methods can be combined by the user to solve different tests on arbitrary grids. The implemented routines can be used in FORTRAN or C. The OpenMP application programming interface is used to improve the computational efficiency. [ABSTRACT FROM AUTHOR]

Published
2022
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