Turbulent flow in a channel occupied by a porous layer considering the stress jump at the interface (original) (raw)
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International Journal of Heat and Mass Transfer, 2006
Flow over a finite porous medium is investigated using different interfacial conditions. In such configuration, a macroscopic interface is identified between the two media. In the first model, no diffusion-flux is considered when treating the statistical energy balance at the interface. The second approach assumes that diffusion fluxes of turbulent kinetic energy on both sides of the interface are unequal. Comparing these two models, this paper presents numerical solutions for such hybrid medium, considering here a channel partially filled with a porous layer through which fluid flows in turbulent regime. One unique set of transport equations is applied to both regions. Effects of Reynolds number, porosity, permeability and jump coefficient on mean and turbulence fields are investigated. Results indicate that depending on the value of the stress jump parameter, substantially dissimilar fields for the turbulence energy are obtained. Negative values for the stress jump parameter give results closer to experimental data for the turbulent kinetic energy at the interface.
Simulation of Turbulent Flow Through Hybrid Porous Medium: Clear Fluid Domains
Heat Transfer: Volume 5, 2000
Turbulent flow in a channel, totally and partially filled with a porous medium, is simulated with a proposed turbulence model. Two cases are analyzed, namely clear flow past a porous obstacle and flow through a porous medium having a cavity with a higher porosity. Mean and turbulence quantities were solved within both computational domains using a single numerical technique. The control volume approach was used to discretize the governing equations. In the first case analyzed, the flow penetration into the porous substrate is accompanied by generation of turbulence kinetic energy within the obstacle. In the second geometry, the flow is pushed towards the cavity as porosity increases.
NUMERICAL ANALYSIS OF THE STRESS JUMP INTERFACE CONDITION FOR LAMINAR FLOW OVER A POROUS LAYER
Numerical Heat Transfer Part A-applications, 2003
A number of natural and engineering systems can be characterized by some sort of porous structure through which a working fluid permeates. Boundary layers over tropical forests and spreading of chemical contaminants through underground water reservoirs are examples of important environmental flows that can benefit form appropriate mathematical treatment. For hybrid media, involving both a porous structure and a clear flow region, difficulties arise due to the proper mathematical treatment given at the interface. The literature proposes a jump condition in which stresses at both sides of the interface are not of the same value. The objective of this article is to present a numerical implementation for solving such a hybrid medium, considering here a channel partially filled with a porous layer through which fluid flows in laminar regime. One unique set of transport equations is applied to both regions. Numerical results are compared with available analytical solutions in the literature for two cases, namely, with and without the nonlinear Forchheimer term. Results are presented for the mean velocity across both the porous structure and the clear region. The influence of medium properties, such as porosity and permeability, is discussed.
Novel Boundary Conditions for Turbulent Flows Enclosed by Porous Media
In this paper we present the new boundary conditions for the turbulent flows enclosed by porous medium. Such flows play a crucial role in many areas such as filters, oil wells, heat exchangers, catalytic reactors, ground water pollution, scouring and deposition of pollutions at river bed. Since the porous media always consist of multi-scale structures starting from the dimension of the porous medium itself down to pore scale. Resolving all of these structures is too expensive considering the uncertainty of the porous media geometry representation. Under certain conditions, the effects of the porous media to the turbulent flows can be modeled as boundary conditions. However, the approach adopted in [1], [2] and [3] lacks some physical property of the flow at the porous media interface because in those works, either the slip velocity or the interface-normal velocity is assumed zero. The boundary conditions proposed in this work, are validated against the pore scaled simulation in which the whole porous media are resolved. The proposed boundary conditions deliver excellent normalized mean velocity and fluctuations. The numerical simulation using boundary conditions only uses 0.92 Million grid cells and it is computed on a simple workstation compared to 230 Million grid cells of the pore scaled simulation which is computed on a cluster with 512 nodes. The proposed boundary conditions allow accurate predictions of such flows to be accessible by the computing resources available in Thailand.
Interface between turbulent flows above and within rough porous walls
Acta Geophysica, 2008
This paper explores the concept of a macroscopic boundary between turbulent flows above and within rough permeable walls. The macroscopic boundary and the associated conditions for macroscopic flow variables have been thoroughly investigated for laminar, but not for turbulent flows. The literature on laminar flows follows two main conceptual models of the boundary: sharp boundary with step changes in macroscopic variables and gradual boundary with smooth changes of variables. The former approach is usually associated with the twodomain simulation models and the latter one with the single-domain models. This paper presents the derivation of the step conditions for velocity and shear stress at the macroscopic boundary between turbulent boundary layer and turbulent porous media flows. The physical meaning of the main terms in the shear stress condition is discussed in order to clarify the relationship between two-domain and single-domain simulation models.
Improved Eddy-Viscosity Modelling of Turbulent Flow around Porous–Fluid Interface Regions
Transport in Porous Media
The RANS modelling of turbulence across fluid-porous interface regions within ribbed channels has been investigated by applying double (both volume and Reynolds) averaging to the Navier-Stokes equations. In this study turbulence is represented by using the Launder and Sharma (1974) low-Reynolds number k − ε turbulence model, modified via proposals by either Nakayama and Kuwahara (2008) or Pedras and de Lemos (2000), for extra source terms in turbulent transport equations to account for the porous structure. One important region of the flow, for modelling purposes, is the interface region between the porous medium and clear fluid regions. Here, corrections have been proposed to the above porous drag/source terms in the k and ε transport equations that are designed to account for the effective increase in porosity across a thin near-interface region of the porous medium, and which bring about significant improvements in predictive accuracy. These terms are based on proposals put forward by Kuwata and Suga (2013), for second-moment closures. Two types of porous channel flows have been considered. The first case is a fully developed turbulent porous channel flow, where the results are compared with DNS predictions obtained by Breugem et al. (2006) and experimental data produced by Suga et al. (2010). The second case is a turbulent solid/porous rib channel flow to examine the behaviour of flow through and around the solid/porous rib, which is validated against experimental work carried out by Suga et al. (2013). Cases are simulated covering a range of porous properties, such as permeability and porosity. Through the comparisons with the available data, it is demonstrated that the extended model proposed here shows generally satisfactory accuracy, except for some predictive weaknesses in regions of either impingement or adverse pressure gradients, associated with the underlying eddy-viscosity turbulence model formulation.
RANS Simulation of Turbulence in a Porous Channel with Constant Mass Injection
In the present paper, a numerical study of flow in a channel with fluid injection through a porous wall is conducted. The study is performed using the method of Reynolds-Averaged Navier-Stokes (RANS) simulation. Turbulence modeling plays a significant role here, in light of the complex flow generated, so several popular engineering turbulence models with good track records are evaluated, including five different turbulence models. Descriptions of f v − 2 and an extended ε − k of Chen and Kim turbulence models are also considered. Numerical results with available experimental data show that the flow evolves significantly with the distance from the front wall such that different regimes of flow development can be observed. The comparison between these computational models with an experimental data for the axial velocity profiles and turbulent stresses is performed. Generally, the best numerical results are obtained from the shear-stress transport ω − k model (SST ω − k) and f v − 2 tu...
Journal of Applied Fluid Mechanics, 2015
The transition from laminar to turbulent flow in porous media is studied with a pore doublet model consisting of pipes with different diameter. The pressure drop over all pipes is recorded by pressure transducers for different flow rates. Results show that the flow in the parallel pipes is redistributed when turbulent slugs pass through one of them and six different flow zones were identified by studying the difference between the Re in the parallel pipes. Each flow zone starts when the flow regime of one of the pipe changes. Transitional flow of each pipe increases the correlation between different pipes pressure drop fluctuations. Frequency analysis of the pressure drops show that the larger pipe makes the system to oscillate by the presence of turbulent patches in its flow. However, when the flow in the smaller pipe enters into the transitional zone the larger pipe starts to follow the fluctuations of the smaller pipe.
2013
The objective of this thesis is to get new equations with out empirical constants to estimate discharge through porous medium for laminar, turbulent and transition flow regimes using easily measurable parameters in the field. It is necessary to analyze the relation between various flow parameters, connected with flow through porous media in parallel flow, to study in depth the various forms of friction equations and the behavior of Darcy and Non-Darcy parameters with physical properties of the media.
Flow through Porous Bed of Turbulent Stream
Journal of Engineering Mechanics-asce, 1993
An analysis of the flow through an inclined-plane pervious substratum coupled to a turbulent, steady, uniform, and fully developed open channel flow above it is introduced. The porous material is taken to be homogeneous, isotropic, and formed by a square-arrayed lattice made of circular cylinders with axes normal to the flow direction. Starting from the Navier-Stokes equation for the flow through the pores, a combination of the ensemble average method and the method of multiple scales is used to derive the equations governing the macroscale flow through the bed. From them, the vertical variation of the velocity in the substratum, as well as the boundary at the pervious interface are obtained. Application of the derived boundary condition, which guarantees continuity of the total stress across the interface, to the frontier between a laminar flow and a porous material, recovers the condition proposed by Beavers and Joseph in 1967. Joint use of the obtained equation for the velocity distribution and available data, suggests that the parameter controlling its exponential decay, from the slip-velocity at the interface to the Darcy velocity away from it, may be a function of the properties of the porous material. The analysis also indicated that the nonlinearity of the flow through the substratum originates from the curvature of the streamlines and the flow separation around the solid particles at the microscale level.