Talk:Frictional pressure drop

Merger proposal
There are a lot of wikipedia pages contains single equations relating to the frictional pressure drops. Most of these are stubs, and have little prospect of progressing beyond stub-hood. I would like to suggest merging them all under the name Frictional pressure drop Bluap 17:05, 14 October 2007 (UTC)

I agree  —Preceding unsigned comment added by 63.97.226.5 (talk) 12:29, 6 November 2007 (UTC)

Title seems too broad
The title seems too broad to me. Most of the articles suggested for merger relate to single-phase flow in a full conduit.

The Manning formula is for open-channel flow. It doesn't seem to fit well with the other topics.

And there are other contexts where frictional pressure drop occurs:
 * Two-phase flow
 * Flow through porous media
 * Filters -- pressure drop increases as the media becomes loaded with filtrate

Aerodynamic drag also involves friction. Perhaps it can also be perceived as a "pressure drop".

Providing at least an outline of the envisioned structure of the article which is expected to result from the merger might draw more support.

Merging articles which present various approximations of the friction factor would be an easier place to start.

Ac44ck 17:35, 14 October 2007 (UTC)


 * You're right that I'm envisaging a page dealing with flow through a full conduit. If you can think of a better name, I'm open to suggestions.  Looking at the Manning page again, you're right - it doesn't fit well with the others, and I'll withdraw my suggestion that it be merged.  For two-phase flow, I think that a brief introduction to correlations for two-phase flow through a conduit would be useful, using summary style to link to a main page elsewhere (which I don't think currently exists.  Likewise for non-Newtonian flow through a conduit.  Bluap 00:20, 15 October 2007 (UTC)


 * The Manning page still has a merger notice.


 * The closing procedure here isn't clear to me:
 * http://en.wikipedia.org/wiki/Wikipedia:Merging_and_moving_pages#Closing.2Farchive_a_proposed_merger


 * Is some closing action needed on each page where the merger was proposed?


 * I probably have some repair work to do already in merging the five articles about the friction factor -- if that's what ends up happening to them. I didn't make the right notes in the edit history yet.  It seems that I'll have to do that if I put redirects in the pages where I copied the info from.


 * I haven't removed a "proposed merger" note before. If I replace the content of the friction-factor pages with redirects, deleting the "proposed merger" notes might entail some extra handling.  Maybe I can watch the Manning page to see how it is done.
 * --Ac44ck 16:37, 16 October 2007 (UTC)


 * I've been bold and removed the proposed merge from the Manning page. When performing a merge, the important fact is to ensure that people viewing the edit-history of the page are directed to the pre-merge pages.  This allows us to retain credit for all edits (which is required as part of the copyright licensing of everyone's contributions to Wikipedia).  If this hasn't been done on the merge target, then the best thing to do is to make a null edit to the page, and note the original source pages in the edit summary. Bluap 20:31, 16 October 2007 (UTC)
 * Will you please explain a "null edit"?


 * I tried just entering "merge content from Colebrook equation" in the Edit Summary box (of the consolidation page that I created) without making any actual change to the text of the article. It doesn't show up in the edit history.  My guess is that the archiving routine has smarts in it to prevent logging a "change" where nothing changed.


 * Is there a way to note multiple merge sources in one Edit Summary? I'd rather not clutter the archive with (or endure the tedium of) a bunch of one-character edits just to get the attention of the archiving routine for each of five "mergefrom" notes.


 * The instructions for merging say to use a specific form of text in the edit history: Save the destination page, with an edit summary noting "merge content from article name" (This step is required in order to conform with §4(I) of the GFDL. Do not omit it or omit the page name.)


 * I see a note in the "Colebrook equation" history page which seems to use a "mergefrom" keyword. I find what looks like a "mergeto" keyword elsewhere.


 * Is the form of the wording in the edit history so important? Is some robot trying to read it or is it only for human readers to be able to follow?


 * Thanks.
 * --Ac44ck 22:18, 16 October 2007 (UTC)


 * A null edit is one where you don't change the page itself. As far as I know, the exact wording in the edit history isn't important, as long as you provide a wiki-link to the page which you're merging from. Bluap 00:53, 17 October 2007 (UTC)

Limited merge
I'd definitely support the merging of the following:


 * Darcy-Weisbach equation
 * Colebrook equation
 * Colebrook-White equation
 * Haaland equation
 * Hazen-Williams equation
 * Swamee-Jain equation
 * Serghide's solution
 * Hydraulic diameter

For the others, I think it's better to keep them as separate, short articles. Separate articles allow the nomenclature and description in the article to be tailored to profession most interested in using them, e.g. Manning formula is clearly written by a civil engineer, Friction loss by a piping engineer (possibly even a firefighter). Neither type would be keen to read through text written by the other to get to the part of the merged page that interests them.

I'm particularly keen to keep a few things on separate pages, as follows:
 * Firstly, Fanning friction factor and Darcy friction factor. In the past I have found it difficult to get graduate mechanical engineers to understand the difference between these two friction factors.  It's much easier today, as they can find them on two separate wikipedia pages with unambiguous titles.  If we merged them into one article, next year's batch would get confused (believe me, any hint of ambiguity can cause a new graduate's mind to blow a fuse).


 * Secondly, Atkinson friction factor and Atkinson resistance. These are a bit specialized (they're only used in mine/tunnel ventilation).  The background detail on those pages (e.g. the summary of Atkinson's reasoning) would look excessive for a subsection of frictional pressure drop and it would end up being cut down.  But for the few thousand people in that field, it's useful to have the background detail on wikipedia, as many of the really experienced people in the field are reaching retirement and their knowledge of this background detail is being lost.

Ac44ck makes a valid point about the title being too broad. I think we need to call it something else but I can't think of a good (short) alternative.

Ecb 20:21, 14 October 2007 (UTC)


 * In terms of which friction factor to use, I think that it's actually best to include both on the same page, and to be explicit as to which friction factor to use in which equation (and in some cases, to include the equivalent equations for each friction factor. One advantage of keeping them on the same page is that all friction factors could have an explicit subscript stating which friction factor it is.  A lot of the applications (e.g. Atkinson resitance) could be written in summary style, with a brief introduction on the main page, and a more detailed page elsewhere. Bluap 00:15, 15 October 2007 (UTC)

Partial consolidation accomplished
I have created a page which consolidates info from the following articles:
 * Colebrook Equation
 * Colebrook-White equation
 * Haaland equation
 * Swamee-Jain equation
 * Serghide's solution

The page is here: Darcy friction factor formulae

I did some cut-and-paste operations, added an intro, and "borrowed" another reference from Pipe Networks. It could use some elaboration, but it's a place to start in that it puts related info in one place.

It could use a section on the relative accuracy of each formula.

Such a comparison would probably assume that the Colebrook equation is "right". But how well would Colebrook's equation do against a modern curve-fit of his own data? Is his implicit formula actually "better" than _every one_ of the perhaps hundreds of explicit formulae which might be obtained from a modern curve-fitting program? And was his data better than we might obtain today?

I didn't turn the five articles listed above into redirects to the Darcy friction factor formulae page. I was tempted to be bold and do so, but we're already in a discussion about merging those and other articles.

Thanks to Bluap for compiling the list of similar articles and lighting the fire which inspired me to put forth at least this much effort. Maybe the consolidation on the page that I created can be folded into a larger merger?

It seems to me that keeping the consolidation of info from those five articles (and any other Colebrook approximations which might be added) in a single-purpose article is useful.

I would favor simple redirects from the five articles consolidated so far. To include such a number of closely-related items in a larger mega-article could make them less convenient to access.

Ac44ck 02:56, 15 October 2007 (UTC)
 * Added content from another article to the consolidation page.
 * Ac44ck 19:30, 15 October 2007 (UTC)


 * The consolidation page has grown to be bigger than I expected. And there is more that could be added.  It seems to me that wrapping it in an even larger mega-article could make accessing the information somewhat cumbersome.


 * Perhaps the article isn't fully ready for "prime time", but I have spent about as much time on it as I want to for a while. I think that it is probably close to being ready for "prime time".  I do think it is ready for "day-time" and that  now would be a good time for others who are interested in the five related articles to begin making changes before it gets too far down some path that they might find to be in need of major revision.


 * I propose making redirects to that page (perhaps giving it a different beforehand if someone has a better name for it) and removing the five related pages from the currently proposed merger.


 * Again, the consolidation page is here: Darcy friction factor formulae


 * Any thoughts on the above?
 * --Ac44ck 02:25, 17 October 2007 (UTC)


 * Congratulations, Ac44ck. I think your Darcy friction factor formulae article is a well-written merge of its source pages.
 * I'm arranging to get hold of Colebrook's 1939 paper from the ICE, and when I get it, I'll clear up some of the questions you've raised on the new page. I'll add Moody's 1944 explicit equation (since I keep coming across it) and express the formulae in terms of natural logarithms as well as base 10 logarithms, just to avoid any confusion.Ecb 17:59, 20 October 2007 (UTC)


 * Thanks, Ecb.


 * It will be helpful to have the perspective of someone who actually has Colebrook's paper in hand. Info from "the horse's mouth" is always good.


 * I found a statement about Colebrook's formula which was intriguing. It seems that a more precise version of it may be available.  I made a write-up about it on the Talk page for the consolidation page -- Darcy friction factor formulae.


 * I didn't know about Moody's 1944 explicit equation. That will be a good addition.


 * I wondered whether it should be noted that "log" means "log10". I would hesitate to add the natural-log forms -- they will require adding/tweaking constants, and introduce rounding errors which may propagate without adequate caution.  The write-up on the Talk page mentioned above may suggest what can happen when rounding errors are ignored.


 * Most spreadsheets, etc., have both Ln and Log10 functions built in. I think that it would be sufficient for the article to document _which_ log it means by "log". --Ac44ck 00:39, 21 October 2007 (UTC)

Suggestions for merger
Here are my suggestions for the merger:


 * Friction factor -- leave as is; this is a useful disambiguation page


 * Hydraulic diameter -- merge/copy "hydraulic radius" section from Manning page to here; I have a draft of this ready to go.


 * Moody chart -- leave separate; it seems worthy of its own article


 * Fanning friction factor -- leave separate, per observation by Ecb about ease of confusion.


 * Possibly create a merge page for formulae of historical significance:
 * + Hazen-Williams equation (though still in use, I suspect that its popularity is waning greatly)
 * + Prony equation

Leave separate; they seem to have specific audiences in mind:
 * + Friction loss
 * + Atkinson friction factor
 * + Atkinson resistance


 * Darcy-Weisbach equation -- merge all of the following to here
 * + Darcy friction factor
 * + Darcy friction factor formulae -- which contains a merge-ready consolidation of all of the following (including some tweaks not found in the source articles):
 * Colebrook equation
 * Haaland equation
 * Colebrook-White equation
 * Swamee-Jain equation
 * Serghide's solution

--Ac44ck 05:11, 17 October 2007 (UTC)
 * That all seems sensible to me.Ecb 17:59, 20 October 2007 (UTC)


 * In light of what I read here http://www.psig.org/papers/2000/0112.pdf (re: the Talk page mentioned in my earlier comment here today), it seems that the Colebrook equation isn't so much empirical in itself as derived from two other formulae. Now I'm even more curious about what Ecb will find in Colebrook's actual paper.


 * Therefore, I propose making the Darcy friction factor formulae page a landing place for people who:
 * 1. Know what a Darcy friction factor is and how to use it
 * 2. Want a quick (wiki) source for _a_ formula.
 * 3. Don't necessarily care about many details of the Colebrook equation


 * That is, to make it a "just the facts" kind of page -- with one form of the Colebrook equation (and mention that a free-surface form exists) there; and a link to a larger article which is devoted to just the Colebrook equation.


 * When we started down this road, I wouldn't have expected that a page might include:
 * 1. A derivation of the Colebrook equation
 * 2. An extended-precision version of the Colebrook equation


 * Plus, a "free surface" version of the Colebrook equation is of narrower interest and is not alluded to anywhere else on the Darcy friction factor formulae page -- it might get buried without notice there.


 * I am now backing away from the position of building an "Everything you wanted to know about the Darcy formula and its parts in one place" page. Specifically, that:
 * 1. Any article whose name begins with the word "Darcy" (including the new consolidation page) would remain separate.
 * 2. The two Colebrook articles be merged
 * 3. Other Colebrook-ish articles be merged into the consolidation page, as exists --Ac44ck 02:45, 21 October 2007 (UTC)


 * I think it should be kept in mind that the Hazen-Williams equation is still used extensively in hydraulic modeling of water distribution systems as it is not computationally intensive. I don't believe it'd be appropriate to be considered a "formulae of historical significance".
 * Zakarov 04:12, 25 October 2007 (UTC)

Suggest closing discussion
There seems to be a lack of interest in making this merge happen.

Since I started some work on this merge, I encountered an editor elsewhere who seemed to be tagging articles which were not necessarily of active interest to them. They apparently saw themselves as "inspiring editors to improve articles." I came to find their tagging of an article on my watch list to be much less than inspiring.

It also affected my thoughts about the "merge" tagging which points here. And raised questions about why my attention was being drawn to this particular task. Perhaps fairly, perhaps not.

I am reminded of garage sale signs. People may be much more interested in putting the signs up than taking them down after the sale. I recall it becoming my job to dispose of their signs after they lost interest in them. They didn't frequent the area, so they weren't motivated to take them down. Signs advertising yesterday's sale elsewhere were litter in my neighborhood. It became my job to take them down.

Ditto the utility markers placed by MISS DIG or one of her sisters. The markers were in my lawn long after any construction work seemed to be happening in the area. I finally called and asked whose job it was to declare the project "done" and remove the markers. They had someone whose job it was to clutter my lawn with markers. They didn't seem to have anyone whose job it was to declare the project "done" and de-clutter my lawn. Nor was anyone willing to tell me that it was okay with them if I removed the markers. I finally declared the project "done" myself and took the markers out. It could have been trouble for me if someone showed up later with a backhoe and ripped up a gas line.

I removed a Wikipedia tag that I thought was bogus and stirred up a hornet's nest.

Several articles are tagged with a "merge" suggestion that encourages discussion here. Is it time to take those tags out? Whose job is it to do that? -Ac44ck (talk) 06:52, 17 February 2008 (UTC)


 * I actually am interested in this subject, and am not a random pass-by. It's simply that "real life" has been taking a priority over Wikipedia...  I think that the work done on the Darcy Friction Factor formulae is enough - my original merge suggestion was patently too wide-ranging in scope.  Bluap (talk) 07:31, 17 February 2008 (UTC)


 * Thanks, Bluap. And thanks for converting several of the tagged pages to redirects.  Your follow-through is inspiring to me.  I hope that "real life" is going better for you these days.  No rush or pressure to necessarily do it yourself – just to be on the same page: what would you like to happen to the remaining tags that point here: Frictional pressure drop?  And now that this article exists as its own page, maybe some of the links in the heading of this article become part of its body? I wouldn't suggest deleting this article because there is some good stuff in this talk page: the industries where the various factors are important, etc., which might eventually make its way into the article. –Ac44ck (talk) 02:17, 18 February 2008 (UTC)