Anybody any good at fluid mechanics??

boglej2 · #1 10-19-2008, 07:09 AM

Stuck doing a college assignment in fluid mechanics on energy loss in pipe fittings, any1 ne good at this?? (mostly about moody diagrams, friction factor and head loss)

FL Knifemaker · #2 10-19-2008, 07:43 AM

Whoa..............I had quite a bit of that back in my college days. At this point, you'd probably get better info from Google than me

That's one aspect of engineering I never used in the real world

Johnny Crab · #3 10-19-2008, 08:20 AM

20 something years agoI had a course with that title.
I STRONGLY suggest the following during your college career:

Go to the library and check out every good reference book on the subject. Deteremine "good" by seeing if your text mentions book titles and by scanning thru them to see if explanations are clear/understandable. Renew these books as long as possible. I used to return good ones during the week(after hitting max number of renewals) and check them out again the next day.

Buy a Schuam's and Problem Solver for EVERY subject you may be challenged in. Since I was in electrical engineering, I got a LOT of these. Here are references for your use:
http://www.amazon.com/Solved-Problem...ref=pd_sim_b_3
http://www.amazon.com/s/ref=nb_ss_gw...Problem+Solver
The Problem Solver was given a one star review but it sounds like a student problem....

Sorry I can't give instant help on your subject.

membranophone · #4 10-19-2008, 08:46 AM

I'm a 4th year chemical engineering PhD student. I just TA'd an applied fluid dynamics class last semester that covered everything that you mentioned. So ask away, I can probably help point you in the right direction.

blizzard · #5 10-19-2008, 08:51 AM

I'm currently doing a fluid mechanics course, although I don't think we've done too much on pipe flow yet. So sorry I can't be of much assistance.

Johnny, those books look real handy. If theres one thing I don't like about my courses is most of them lack decent worked examples.

Geddyfleaharris · #6 10-19-2008, 09:33 AM

I took it on college but haven't really applied it in the real world as I am not in design. I thought it was pretty interesting actually.

boglej2 · #7 10-19-2008, 11:15 AM

Cheers membranophone, i have to try an work out the friction factor from my experimental data, and i'm pretty sure i have to get it by drawing a moody chart in excel, but i'm not entirely sure.

Thats the experimental data from one particular pipe, the same exp was done on 4 more pipes.

The objective is to compare the two values of head loss(experimental and theoretical) and get a % difference but to do this i need the friction factor (f) i think??

Any help appreciated!!

Xorese · #8 10-19-2008, 11:26 AM

I've just started fluid mechanics, i can try, but i have my high doubts i'll be usefull.

jady · #9 10-19-2008, 11:29 AM

I did some fluid mechanics first thing this morning (I had a lot of beer last night)

Johnny Crab · #10 10-19-2008, 12:10 PM

Quote:

Originally Posted by blizzard

Johnny, those books look real handy. If theres one thing I don't like about my courses is most of them lack decent worked examples.

+1000 !!

For calculus and some other stuff, I spent uncountable hours working every problem in Schuams and Problem Solvers so tests/exams were less of a headache. Sort of like playing bass...the more you practice a part/piece/song...the easier it is to make it look easy.

About the only thing I remember from fluids is being amazed/impressed with understanding(from the math) that hit as to why the bottom of a dam has a lot more force on it than the top and why a huge chunk of iron(boat) can actually float.

I do use it some at work(petrochem plant) for control valves & flowmeters but software does calcs(BEWARE the faulty lookup tables!). The piping design guys in another department do what you're asking about.

membranophone · #11 10-19-2008, 06:21 PM

Quote:

Originally Posted by boglej2

Cheers membranophone, i have to try an work out the friction factor from my experimental data, and i'm pretty sure i have to get it by drawing a moody chart in excel, but i'm not entirely sure.

Thats the experimental data from one particular pipe, the same exp was done on 4 more pipes.

The objective is to compare the two values of head loss(experimental and theoretical) and get a % difference but to do this i need the friction factor (f) i think??

Any help appreciated!!

All of my notes and textbooks and whatnot are in my office, so I'll take a look at this tomorrow.

boglej2 · #12 10-20-2008, 07:59 AM

ne ideas anybody??

membranophone · #13 10-20-2008, 11:14 AM

Okay, without the assignment sitting in front of me, it's hard to exactly diagnose your problem, but if you need to find a friction factor, there are a few empirical models:

First, calculate your Reynolds number, Re = (rho)DV/(mu)
where rho is density, D is the pipe diameter, V is the average velocity in the pipe, and mu is the viscosity.

If Re is less than 2100, then f = 16/Re where f = friction factor.

If Re is larger, then the flow is turbulent, and there are two general empirical models.

If 10^4 < Re < 10^5, then use the Prengle-Rothfus model which states:

f = 0.0791 / (Re^.25)

and if 10^5 < Re < 10^6, use the Prandtl model,

1/f^.5 = 4.0 * log(Re*f^.5) - 0.4

Let me know if this helps at all.

What book are you using for this class? Bird, Stewart, Lightfoot?

boglej2 · #14 10-20-2008, 02:40 PM

cheers for the relpy an fiding that out for me, but i figured out what it was, and as i thought it was something really simple. I had the reynold's number and the relative roughness, so what i was supposed to do was using those figures and a moody chart(we were given in class) read off the friction factor from the moody chart. Very simple, and it was staring at me the whole time on the lab sheet. Hope i didn't waste too much of your time!!!

membranophone · #15 10-20-2008, 02:46 PM

Quote:

Originally Posted by boglej2

cheers for the relpy an fiding that out for me, but i figured out what it was, and as i thought it was something really simple. I had the reynold's number and the relative roughness, so what i was supposed to do was using those figures and a moody chart(we were given in class) read off the friction factor from the moody chart. Very simple, and it was staring at me the whole time on the lab sheet. Hope i didn't waste too much of your time!!!

No problem. The formulas I gave are what you use to construct the lines on a Moody diagram. It's much easier to do it graphically though like you did.

etoncrow · #16 10-20-2008, 02:52 PM

There is a great book published by Crane Fluids. It is orange, spiral bound and highly recommended to any mechanical or chemical engineer. I am away from my desk but I will post the information tomorrow. I mean you will throw away your other fluids reference books...

RHFusillo · #17 10-21-2008, 07:03 AM

I remember the words, "Navier Stokes."

etoncrow · #18 10-22-2008, 09:00 AM

Sorry, it took me longer to get back to the office than I anticipated. The book I referred to earlier is: "Flow of Fluids Through Valves, Fittings and Pipe" Technical Paper No. 410 (1988) written by the Engineering Department of the Crane Company, 800 3rd Ave., King of Prussia, PA 19406. In nearly thirty years of engineering this is by far the best fluids book I have found.