Talk:Darcy's law

message: This whole article has been written from a hydrology standpoint.  I have rewritten a bunch of it in a more generalized form, that is one where fluids other than water are involved (as is frequently the case when using Darcy's law in oil field applications).  TastyCakes 05:20, 9 November 2006 (UTC)
thread_title: Article generalization

message: In the additional forms section an expression of Darcy's Law common to 'petroleum engineering' uses small 'q' for total discharge (units of volume per unit time). At the start of the article small 'q' is defined as flux, and large 'Q' as total discharge (units volume per unit time).
:I can't even see what new information that extra equation for petroleum engineers give to the article. I vote for removal or rewrite of that particular section. Berland 07:45, 29 January 2007 (UTC)
replies: text: I'd support that. I also made an article concerning that a few weeks ago, groundwater discharge (which I'm yet to integrate into other articles). I'm not 100% sure about petroleum engineers, however I know the civil/hydro engineers stick to the same 'q' vs 'Q' conventions as hydrogeologists.+mwtoews 00:40, 12 January 2007 (UTC)

text: No, gravity is (or can be) included, in \Delta P, in the equation q=-\kappa/\mu \Delta P. It is a vector equation, and \kappa possibly as a tensor if anisotropy is to be considered. Berland 17:33, 19 February 2007 (UTC)
thread_title: Article consistency

message: I think the symbol for porosity should be \phi, not n,  as in the porosity arcticle. Berland 07:25, 17 January 2007 (UTC)
replies: text: I know I've seen both, but I forget who uses what (different disciplines have different notations).  You might add a sentence to the article saying "Foo engineers use "x" to denote porosity, and bar engineers use "y"."  Lunch 18:31, 17 January 2007 (UTC)
replies: text: Unfortunately, there are many conventions used for the "symbol for porosity" (such as n, \phi, \beta). For the sake of consistency with the porosity article, I suggest using the same φ symbol, as Berland suggested, and perhaps add the sentence about the different conventions in the porosity article.  Fetter and Domingo and Schwartz use n, while Dingman uses \phi.  Personally, I'm a fan of \phi for porosity, and n for Manning's roughness coefficient.+mwtoews 19:40, 17 January 2007 (UTC)
replies: text: I changed to \phi. Berland 07:39, 29 January 2007 (UTC)
thread_title: Porosity

message: I believe there was a mistake in the derivation section, namely that in the application of the proportional but opposite viscous resisting force, a negative sign was omitted, which prevents the algebraic manipulation into the following step. I will make the change, but hope someone with better knowledge will check this. SselemanLuos (talk) 21:20, 13 January 2009 (UTC)
thread_title: Derivation

message: There's no discussion of anisotropic permeabilities; in this case, the permeability term, k, is a tensor. Please could someone add some information on how this tensor and the resulting equation are to be interpreted?
:The section 'In 3D' encompasses this, though it is not explicitly mentioned that \kappa there is a tensor/3 by 3 matrix. --Berland 21:16, 29 July 2007 (UTC)
thread_title: Tensor permeabilities

message: Aren't the two laws quite related? Beryllium-9 (talk) 09:53, 29 June 2011 (UTC)
thread_title:  What about Hagen-Poiseuille? 

message: It would be useful to see a related link to other kinds of porous medium, specially thin (in flow direction) PM.
174.112.104.110 (talk) 18:26, 28 January 2012 (UTC)
thread_title:  flow through other kinds of porous medium? 

message: It would be nice to see derivation from Navier-Stouks or at least reference to some paper  — Preceding unsigned comment added by 91.228.20.50 (talk) 14:39, 23 March 2012 (UTC)
thread_title:  Navier-Stouks 

message: The article defines Re for porous media as Re = ρ.v.d30/μ  ;  v is defined as specific discharge and d30 as representative grain diameter (often taken as 30% grain size ...) - I am paraphrasing here. I have two comments about that: 
1) specific discharge is effectively equal to flux, q, as defined earlier. I then propose that we use only one term and keep symbols consistent. 
2) d30 cannot be "a representative grain diameter". I propose we drop the 30 in the equation, but keep the description as is explaining that representative can be the d30 or d50. Also d30 or d50 can be measured in various ways, not necessarily via sieving so the mentioning the methodology is out of context. 
So, I propose to have: 
The Reynolds number (a dimensionless parameter) for porous media flow is typically expressed as 
Re = ρ q d / μ 
where ρ is the density of water (units of mass per volume), q is the flux (units of length per time), d is a representative grain diameter for the porous media (with units of length), and μ is the viscosity of the fluid. The representative grain diameter is often taken as the d50 (i.e. median grain size) or the d30 (i.e. the size of where 30% of the grains are smaller).--85.116.189.149 (talk) 14:38, 5 February 2013 (UTC)
thread_title:  Reynold's number 

message: In the first discussion of the formula the author states: length over which the pressure drop is taking place (m).  There is no m in the formula!! There is an "L" in the denominator.  I can't believe I'm the only one who noticed this!  — Preceding unsigned comment added by Siragrossman (talk • contribs) 19:08, 7 August 2013 (UTC)
replies: text: First, there are many authors to this any any article on Wikipedia. The "m" you are seeing in the text is the common abbreviation for metre, the SI unit of the length variable, L. Units don't usually appear in the formula, but are in parenthesis after explanation of each variable. +mt 05:00, 8 August 2013 (UTC)
thread_title:  Formula question 

message: Substituted at 12:49, 29 April 2016 (UTC)
thread_title: Assessment comment

message: The symbol k for absolute permeability is widespread in the petroleum industry, and the petreoleum industry includes a large number of people. We also use pressure and gravity as separate terms in the equations. The original version of Darcy's equation is deficient even for single phase flow for our (the reservoir engineers) use, and we always use multiphase (et least two-phase) flow equations as developed by Muskat et al. I have written  a significant expansion and contribution on multiphase equations that I am thinking to implement in this article. How widespread is the use of hydraulic conductivity parameter, and how widespread is the use of the symbol K for this parameter? My general impression is that there are no strict standard on use of symbols and units in Wkipedia articles. The impression is that the author of article or pargraph in question explains his selection of symbols and list his choice of units. Can you estimate how many articles in Wikipedia that contain kappa as symbol for permeability?  — Preceding unsigned comment added by Frode54 (talk • contribs) 03:04, 22 December 2016 (UTC)
replies: text: There are no strict standards on the use of symbols, but it is nice when there is consistency between articles. As for changing the symbol κ (kappa) to k, I think I now agree that is is more widespread and support changing it. (Hydraulic conductivity is pretty much always K, as I've never seen any other forms). How about we let this suggestion sit here for about another week to see if anyone wants to weight in on the topic. If there's no further discussion or objection, then please proceed to change the symbol. Other articles that I'm aware of include Permeability (earth sciences), Darcy (unit), Relative permeability, and Fluid flow through porous media (possibly more), which I'd advise to change too. +mt 04:04, 22 December 2016 (UTC)
replies: text: Update: I've updated most instances of kappa to lower k, as discussed above. +mt 03:13, 27 October 2018 (UTC)
thread_title:  Petroleum engineering and multiphase flow