A three-phase interpenetrating continua approach for wave and porous structure interaction

Purpose This paper aims to propose a three-phase interpenetrating continua model for the numerical simulation of water waves and porous structure interaction. Design/methodology/approach In contrast with one-fluid formulation or multi-component methods, each phase has its own characteristics, density, velocity, etc., and each point is occupied by all phases. First, the porous structure is modelled as a phase of continua with a penalty force adding on the momentum equation, so the conservation of mass is guaranteed without source terms. Second, the adaptive unstructured mesh modelling with P1DG-P1 elements is used here to decrease the total number of degree of freedom maintaining the same order of accuracy. Findings Several benchmark problems are used to validate the model, which includes the Darcy flow, classical collapse of water column and water column with a porous structure. The interpenetrating continua model is a suitable approach for water wave and porous structure interaction problem. Originality/value The interpenetrating continua model is first applied for the water wave and porous structure interaction problem. First, the structure is modelled as phase of non-viscous fluid with penalty force, so the break of the porous structure, porosity changes can be easily embedded for further complex studies. Second, the mass conservation of fluids is automatically satisfied without special treatment. Finally, adaptive anisotropic mesh in space is employed to reduce the computational cost.

Mathematical Modelling of Methane-Air Combustion in a Channel with a Porous Axial Insert

In the paper we construct a mathematical model of turbulent flow, combustion and heat transfer in an axisymmetric chamber with an axial zone of a compacted particulate material. The averaged equations written using the model of interacting and interpenetrating continua contain diffusion equations of individual components, the energy equation for the gas and the porous structure, the motion equation for a mixture of gaseous components, as well as the equation of the turbulence model. This system is closed by the equations of continuity and condition of the mixture. In the flow, an irreversible chemical reaction of stoichiometric mixture of methane and oxygen proceeds. Numerical study of porosity influencing the nature of turbulent combustion is conducted.

On the quest for a hyperbolic effective-field model of disperse flows

The cornerstone of multiphase flow applications in engineering practice is a scientific construct that translates the basic laws of fluid mechanics into a set of governing equations for effective interpenetrating continua, the effective-field (or two-fluid) model. Over more than half a century of development this model has taken many forms but all of them fail in a way that was known from the very beginning: mathematical ill-posedness. The aim of this paper is to refocus awareness of this problem from a unified fundamental perspective that clarifies the manner in which such failures took place and to suggest the means for a final closure.

The Equation of a State of Porous Mixture of Condensed Substances With Specific Heat the Dependence on the Temperature

The work is devoted to a problem of the description of behavior of multispecies mixtures of various powders under shock-wave loading. At the description of a mixture the model of interacting and interpenetrating continua, the principles of which construction are stated in the monographies of R. I. Nigmatulin, is used. The equilibrium condition is satisfied by conditions of equality of pressure, temperatures and mass velocity of species. The presence of gas inside pores is taken into account. The porous mixture of the several condensed substances in thermodynamic equilibrium is represented as single-phase continuous medium with the equation of a state in the Mie-Grüneisen form, which parameters expressed in terms of the corresponding parameters of the species. The numerical calculations of shock adiabats for porous substances and porous mixtures of the condensed species are performed with use of various models of the equation of a state of a mixture taking into account: a) only elastic pressure and elastic energy; b) both elastic, and thermal terms with constant specific heat of substance and Grüneisen oefficient; c) elastic and thermal terms with specific heat of substance the dependence on the temperature and variable Grüneisen coefficient. The results of computations are compared with experimental data.

CFD Modeling and X-Ray Imaging of Biomass in a Fluidized Bed

Computational modeling of fluidized beds can be used to predict the operation of biomass gasifiers after extensive validation with experimental data. The present work focused on validating computational simulations of a fluidized bed using a multifluid Eulerian–Eulerian model to represent the gas and solid phases as interpenetrating continua. Simulations of a cold-flow glass bead fluidized bed, using two different drag models, were compared with experimental results for model validation. The validated numerical model was then used to complete a parametric study for the coefficient of restitution and particle sphericity, which are unknown properties of biomass. Biomass is not well characterized, and so this study attempts to demonstrate how particle properties affect the hydrodynamics of a fluidized bed. Hydrodynamic results from the simulations were compared with X-ray flow visualization computed tomography studies of a similar bed. It was found that the Gidaspow (blending) model can accurately predict the hydrodynamics of a biomass fluidized bed. The coefficient of restitution of biomass did not affect the hydrodynamics of the bed for the conditions of this study; however, the bed hydrodynamics were more sensitive to particle sphericity variation.

A Validation Study for the Hydrodynamics of Biomass in a Fluidized Bed

Computational modeling of fluidized beds can be used to predict operation of biomass gasifiers after extensive validation with experimental data. The present work focused on computational simulations of a fluidized bed using a multifluid Eulerian-Eulerian model to represent the gas and solid phases as interpenetrating continua. Hydrodynamic results from the simulations were quantitatively compared with X-ray flow visualization studies of a similar bed. It was found that the Gidaspow model can accurately predict the hydrodynamics of the biomass in a fluidized bed. The coefficient of restitution of biomass was fairly high and did not affect the hydrodynamics of the bed; however, the model was more sensitive to particle sphericity variation.

Computational Modeling of Biomass in a Fluidized Bed Gasifier

Computational modeling of fluidized beds can be used to predict operation of biomass gasifiers after extensive validation with experimental data. The present work will focus on computational simulations of a fluidized bed gasifier with a multifluid Eulerian-Eulerian model to represent the gas and solid phases as interpenetrating continua. The simulations described in this paper will model cold-flow fluidized bed experiments, and consider factors such as particle sphericity, coefficient of restitution, and drag coefficient calibration. Hydrodynamic results from the simulations will be qualitatively compared with X-ray flow visualization studies of a similar bed.