Questions tagged [porous-media]
Porous media are solid materials that contain interconnected pores allowing fluids to pass through.
46
questions
0
votes
0
answers
18
views
Boussinesq Approximation Term in Momentum Equation
According to the Boussinesq equation: $\rho = \rho_o ( 1 - \beta_t ( t – t_o) - \beta_c ( c – c_o ) ) $
So, $\rho \cdot g$ should be equal to : $\rho g = g \rho_o ( 1 - \beta_t ( t – t_o) - \...
- 1
0
votes
0
answers
16
views
The local and average Nusselt number in a square cavity
I am in the process of programming the local & average Nusselt number in a left vertical wall but my Matlab script gives me inappropriate values and it doesn't change with changing of Rayleigh ...
- 1
0
votes
0
answers
42
views
Pressure driven vs flux driven
What's the difference between pressure-driven and flux-driven flows in the context of porous media?
- 23
0
votes
1
answer
21
views
Ability of some porous solids to tentatively sit on water for a while before sinking
How does a porous solid such as the cereal "Wheatena" manage to tentatively sit on water for a while before sinking? I assume it initially somehow evades capillary action, perhaps through ...
- 55
0
votes
0
answers
26
views
Leaking water from leaky pots
I have two absolutely identical pots with round bottoms. Each bottom has the same number of absolutely identical holes drilled in it. In the first pot, all the holes are quite far apart, while in the ...
- 121
0
votes
2
answers
59
views
Groundwater flow with external forcing
I want to solve the diffusion equation in porous media with some external forcing at the origin. The regular diffusion equation-
$$
\frac{\partial h}{\partial t}=D\nabla^2h
$$
But I want to solve for ...
- 101
1
vote
1
answer
35
views
Which kind of paper has highest absorption speed? [closed]
I am experimenting to analyse the liquid wicking(radial) behaviour of various liquids. I have performed initial studies and experiments on household paper towels but they tend to deform and stick to ...
- 111
2
votes
0
answers
34
views
What does it mean for resistance, as it appears in Ohm's law, to be an integral, evaluated over the body as a whole?
In literature I read:
The three linear flux laws mentioned are:
As seen, a correspondence exist between the hydraulic conductivity $K$, thermal conductivity $\lambda$, and electrical conductivity $\...
- 1,255
0
votes
1
answer
31
views
Diffusion in porous media - interface flow
i have been working on a problem lately where i think i m missing some basic understanding:
I consider the diffusion of a macromolecule in porous media, which i see as Brownian motion through the ...
0
votes
0
answers
56
views
Can Friedlander Equations be used to Model Buried Explosive
To quote from WIKIPEDIA
The simplest form of a blast wave has been described and termed the Friedlander waveform.[11] It occurs when a high explosive detonates in a free field, that is, with no ...
3
votes
1
answer
88
views
Superfluids in areogel and porous media: why?
Aerogels are materials that are like ~90% or more air. As I understand, the topology of the material (i.e. of that part of the aerogel that is not air) is not such that air is contained into bubbles. ...
- 2,935
1
vote
0
answers
34
views
Definition of (fully) saturated porous medium
Let us consider a porous medium and let $\psi$ be a hydraulic head. If $\psi \geq 0$ we say that porous medium is fully saturated, otherwise is unsaturated.
How can I imagine saturated porous medium? ...
- 11
0
votes
1
answer
51
views
Porous media flow equation in terms of fluid compressibility and determination of coefficients?
I'm having trouble understanding an equation and solution method given in literature. The 1D flow equation for "high rate" linear gas flow through a porous medium is given as:
$$\tag{1} p_1-...
- 1,255
1
vote
1
answer
121
views
Fluid dynamics for the sepiolite
I would like to know some about the physics of an interesting material, the sepiolite. I mean the material from the Wikipedia article Sepiolite where are explained the general and identification ...
- 37
2
votes
1
answer
142
views
Origin of terms in the Nernst-Planck equation
We know the Nernst Planck equation is
$$ \frac{\partial c}{\partial t} = - \nabla \cdot J \quad | \quad J = -\left[ D \nabla c - u c + \frac{Dze}{k_\mathrm{B} T}c\left(\nabla \phi+\frac{\partial \...
- 795
0
votes
0
answers
24
views
What is the relationship between pressure and concentration in liquids in porous media?
I am working on a model in porous media. In particular, it is about the formation damage due to the precipitation. I assigned Dirichlet boundary condition for the concentration near the well-bore, ...
1
vote
0
answers
43
views
"Directional" conductivity in linear flux-potential laws?
Question: Has the notion of "directional conductivity" been defined and used in the study of heat flow and electric current flow?
Context: The table below gives three laws that describe linear flux-...
- 1,255
1
vote
1
answer
37
views
Reynolds limits on laminar flow between irregular plates (fracture)
I'm trying to understand the limits of laminar flow in a system comprised of two plates of varying width. The idea is to model a naturally fractured system and understand up to when flow and pressure ...
- 113
3
votes
0
answers
69
views
Dimension reducing of heat equation 2D problem
I have two metal objects of different thickness and conductivity:
1) thicker, but poorly conductive. It's properties: $k_1, H$
2) thin and much better conductive. It's properties: $k_2, h$
...
- 83
2
votes
1
answer
58
views
What are the assumptions for porous media to be considered as continuum?
The poroelastic models like - Biot theory- are built on the continuum approach. But I am not able to understand, how this heterogeneous media can be considered as a continuum.
However, If the porous ...
- 71
2
votes
2
answers
272
views
What is the meaning of effective density in porous media? Is the density of air inside the pore space not same as density of free air?
I am trying to understand the physical meaning of using effective density in porous media. Is it a fictitious value? Can't I use the density of solid and fluid as it is while modeling porous media?
- 71
1
vote
0
answers
121
views
Onsager reciprocal relations and Darcy's permeability tensor for anisotropic porous media
The wiki entry on soil tensor permeability states that
The tensor is symmetric by the Onsager reciprocal relations
Bear & Cheng (2010, p122)* state that:
The hydraulic conductivity tensor, $...
- 1,255
2
votes
1
answer
57
views
Acoustics: Construction of the pressure field with transmitted and reflected plane waves
So I have been reading one of the papers about wave manipulation, which takes advantage of the phase shifted reflection by tailoring the design of the system. The design has two domains: air and foam (...
- 151
1
vote
0
answers
25
views
Computing the porosity of a core sample from a set of digital images
Are there any references of books and/or papers about methods to compute the porosity of a given core sample (from an oil and gas reservoir) if this core is given as a set of digital images (for ...
0
votes
0
answers
228
views
Can the principal values and directions (axes) of a rock's permeability anisotropy be determined on a single cylindrical core sample?
If a rock core (a right-cylinder of rock), as shown at the left of the image below, has bedding planes oriented arbitrarily with respect to the long axis of the core, how does one go about determining ...
- 1,255
2
votes
2
answers
124
views
Percolation theory: What is the critical amplitude for the "backbone" of a 2-D network?
Disclaimer: I am just learning about percolation theory for the first time, so I am not too familiar with some of the terminology.
Suppose you have a 2-D square lattice with bonds connecting sites. ...
- 183
6
votes
1
answer
317
views
Percolation theory: Is there a clear relationship between "probability of connection" and "effective porosity"?
Disclaimer: I am a geophysicist, not a physicist. Sometimes we speak a slightly different language and use different terms.
Suppose you have an $N$ x $N$, 2-D rectangular lattice with bonds which ...
- 183
0
votes
1
answer
100
views
Can the coefficient of inertial resistivity ($\beta$-factor) be a 2nd rank tensor?
Question: Can the Forchheimer $\beta$-factor be a 2nd rank tensor (like permeability, $k$)?
In most cases in literature, the quadratic Forchheimer equation is applied only to one-dimensional flow. ...
- 1,255
0
votes
1
answer
92
views
Integrating the quadratic Forchheimer equation
Starting with the commonly cited Forchheimer equation:
$$\tag{1} -\frac{dp}{ds}=\frac{\mu q}{kA}+\frac{\beta \rho q^2}{A^2}$$
multiplying through by density
$$\tag{2} -\rho \frac{dp}{ds}=\frac{\mu \...
- 1,255
1
vote
1
answer
258
views
Darcy's law using Hubbert potential vs pseudo-pressure for a gas
How does one show the equivalence (or difference) of Darcy's law written using Hubbert's potential of a real gas to that of Darcy's law written using the concept of pseudo-pressure (aka pseudo-...
- 1,255
1
vote
0
answers
69
views
When does a finite size random graph percolate?
Assume we are simulating percolation on a 2d lattice. While the system is of finite size, we say that the critical state appears when a cluster connects two opposing ends of the lattice. The bigger ...
1
vote
1
answer
575
views
How to implement Hubbert's potential to calculate permeability using Darcy's law?
Question: How does one implement Hubbert's potential to calculate permeability without making assumptions to neglect any aspects of the potential defined by Hubbert?
Question's supplemental material: ...
- 1,255
1
vote
0
answers
30
views
Permeability anisotropy of porous media
Imagine if one were to cut a cylindrical plug out of a perfectly homogeneous rock exactly along one of the principal axis of permeability anisotropy, specifically Kmax. Then, imagine inserting only ...
- 1,255
1
vote
1
answer
285
views
Biot coefficient as function of porosity
Can the Biot poroelasticity coefficient $\alpha$ be approximated as a function solely of porosity $\phi$, and if so then how (and under what conditions)?
I've read (e.g. 2.02-3 here) that it can, ...
- 755
0
votes
3
answers
187
views
Does groundwater flow depend on the geometry of the aquifer?
I consider two cases of a confined aquifer and want to calculate the pressure / hydraulic head in a quasi 1d case. These two cases are shown in my drawing.
I assume homogenious, isotropic darcy flow, ...
1
vote
1
answer
2k
views
Non-Darcy Flow : Forchheimer plotting method
Recalling Darcy's equation for gas flow, assuming ($z\mu_g$) = Constant
$$\tag{1} q_{g,sc}=\frac{kA}{L}\left(\frac{T_{sc}}{Tp_{sc}}\right)\left(\frac{1}{2z\mu_g}\right)(p_1^2-p_2^2)$$
For ...
- 1,255
2
votes
1
answer
903
views
Darcy Flow in porous material - consider porosity in cross-section area?
According to Darcy's Law, the volumetric flow rate Q of a fluid occuring due to a pressure difference $\Delta p$ over a distance L and through a cross-sectional area A of a porous medium (volume V) ...
- 51
4
votes
1
answer
444
views
Can Smoothed-Particle Hydrodynamics (SPH) be used to simulate porous media flow and deformation?
I am trying to use Smoothed-Particle Hydrodynamics (SPH) to study fluid flow in and around porous media. The aim is to observe how it causes erosion and failure. For this, from my understanding, there ...
- 293
6
votes
2
answers
350
views
Are there solid materials with controllable porosity?
In analogy to piezoelectric materials, where the application of an electrical field creates mechanical deformation in the material, I have the following question.
Are there solid materials whose ...
- 1,238
4
votes
2
answers
13k
views
Can facial surgical mask effectively filter particles of smoke pollution?
Singapore is having an episode of its regular hazy season because of smoke from forest fires. Some people have been using surgical masks like the the one shown at the bottom of this post, presumably ...
- 57
0
votes
1
answer
370
views
Darcy law yields extreme speed for gas flow through packed spheres
The Darcy law is as follows:
$$u=-\frac{k}{\mu}\nabla p.$$
Assume we have a gas, then $\mu$ is about $10^{-5}$.
For packed spheres a few $\rm mm$ in diameter, $k$ is of order $10^{-8}\ {\rm m^2}$.
Say ...
- 195
3
votes
0
answers
172
views
How do I simulate a constant velocity flow in porous media
I am modelling gas combustion in porous media. Most contemporary models assume that the pressure drop from the porous media is small enough to disregard, but I want to include that in my investigation....
- 195
11
votes
1
answer
241
views
How can one build a multi-scale physics model of fluid flow phenomena?
I am working on a problem in Computational Fluid Dynamics, modeling multi-phase fluid flow through porous media. Though there are continuum equations to describe macroscopic flow (darcy's law, ...
Paul
1
vote
2
answers
6k
views
How thin a filter to filter particles out of salt water to make salt for human consumption?
I have gathered some salt in the Death Valley and for the fun of it I would like to clean it and make it edible. The process I plan to follow is simple:
Dissolve the salt in water.
Boil water for 30 ...
- 13
3
votes
2
answers
559
views
Laws of fluid flow in porous medium
What are the equations that describe the flow of a fluid in a porous medium? Is there a variation of the Navier-Stokes equations?
I would like to model the flow of air through a sponge-like structure....
- 381
51
votes
3
answers
15k
views
When water climbs up a piece of paper, where is the energy coming from?
Take a glass of water and piece of toilet paper. If you keep the paper vertical, and touch the surface of the water with the tip of the paper, you can see the water being absorbed and climbing up the ...
- 4,771