"Radius" by BigBen2k

[bigben2k]

Originally posted by unregistered
Ben
I spent 10 years on committee work at the national level (ASTM, API, etc)
I have very definite ideas about how I will NOT spend the balance of my life

...and I'm happy for you.

You may not agree with the way that this development is going, and I understand that. I will however ask you to respect the fact that very few of us have the same level of knowledge and experience as you, and as such, if you wish to continue looking down at this, then by all means go ahead: we won't hold it against you.

Originally posted by unregistered
I still don’t think you’re hearing what’s being said

I gave Cathar not a single answer (that I recall anyway)
but suggested areas of ‘interest’
which HE followed, and came up with HIS design

if I tell you what to do, are you then going to think its ‘your’ design ?
(I know the answer to this question, and its depressing)

why solicit answers from others ?
spend the time, learn it yourself, answer your own questions
(independence, initiative, self-reliance, blah blah blah– that’s my song, always)

...and your comments are welcome. You do however have to understand that I cannot rely on a single source of information. (which makes your o-ring statements most difficult to deal with).

I don't expect anyone to give me the answer to #7, nor any other question, but I will openly state what issues I am encountering, in the hope of being pointed in the right direction.

This development has gone beyond my doing, to some extent, but it started that way anyways! I will claim the original idea as mine, even though I realize that it has probably already been done. I fully expect someone out there to chime in here at any time with "I did (something similar to) that, here's my result". It'll be a dissapointment, but at least I can honestly say that I wasn't copying someone else's work.

I will however sollicit some assistance (beyond what you would provide) for the structural integrity, in the form of concept, and possibly formulaes. I already have a fair idea of how to calculate the deflection of standard shapes, so if I have to "rough it" by using standard data available pretty much anywhere, then I'll have to go with that, and add a big safety margin. It may not be efficient, but it will work.

Originally posted by unregistered
#7
address the flow issue
THEN worry about machining it
you're still bassackwards

Of course this is "bassakwards", I agree.

IMO, this forum's purpose is to share ideas, so that we can learn from one another. As a result, most of the comments will address the simple issues, in no particular order, and some more complex ones, perhaps more as an overview. I take full responsability for the most complex ones (thermal property calcs).

The secondary purpose of this thread is to share the personal experience. I have found this to be mostly a Canadian thing, go figure.

I will address #7 when I'm good and ready to. I'm not happy aproaching it from a machining point-of-view, but that's otherwise what I'm open to hear right now.

[utabintarbo]

Originally posted by bigben2k
...

IMO, this forum's purpose is to share ideas, so that we can learn from one another. As a result, most of the comments will address the simple issues, in no particular order, and some more complex ones, perhaps more as an overview. I take full responsability for the most complex ones (thermal property calcs).

The secondary purpose of this thread is to share the personal experience. I have found this to be mostly a Canadian thing, go figure.

This IS the purpose of forums in general, as I see it. To share information, not information about links to information, nor obscure references to pearls of wisdom scattered about the web. To state that the information exists helps no one (especially if it is stated in a snide and unctuous manner) - everyone knows it exists. If that is all you have to contribute, you contribute nothing.

[/thread hijack mode]

Bob

[Alchemy]

bigben2k, you flatter me to suggest I could actually absorb all this information and have any useful information to offer in enough time to be of any service.

This design is more a mechanical engineering issue than a chemical engineering issue. With the sort of complex flow patterns you're discussing, I wouldn't be able to offer up much more than educated guesses about the design.

I suppose I could come up with some estimated performance specs given a number of conditions. That wouldn't take too long, but I'd need some more information before I started.

My current concern with this design is that the fins don't seem to disrupt the flow much, and will probably impede turbulence rather than improve it.

This isn't a bad thing, really. It might make a very effective high-flow-rate block.

Anyway, if you could give me the following info I could get started:

1) Estimated flow rates

2) Estimated heat dissipation (I'd assume ~100 watts)

3) Some info about the top mating piece for the block - at least enough to tell me something about the channels. I'm having trouble determining the current design and dimensions of the channels from your posts.

I'm a bit busy this week, so it may take a few days before I can get to work on this, but I hope whatever I find is helpful.

Alchemy

[bigben2k]

That would be very helpful, if you're willing to help.

I'd rather use a 100 W heat source, in an 8 by 10 mm area that's centered. That's an AMD Athlon core, overclocked.

I have yet to balance the flow in this thing, and it will depend on the size of the nozzle that I use. If I go with a 3/8 inch nozzle, then the flow splits 16 ways, in a 1mm wide channel that is 5 mm high. The copper fins are 1.5 mm wide. As you can observe, because of the 1mm cuts, there is a varying ratio of copper-to-channel from 1.5 to 0.75 . This block might have a nozzle that is 9/32 inch in diameter, which would force the flow to split 8 ways. Nozzle size is not final...

The top rests right on top of the fins, improving structural integrity. It may be made of copper, or polycarbonate. In any case, all channels are 5mm high, and 1 mm wide.

You should notice right away (?) that the flow isn't balanced at the outer edge: the flow is higher along the main 4 fins. I plan to balance this with the right openings in the top.

Flow rate: I will be using a "Little Giant" 2-MDQ-SC, which has a 14.4 feet max head, but otherwise capable of flow rates of more than 500 gph. See specs here I haven't done my homework yet so I can't give you an exact flow rate, but I have been shooting for 5 gpm (300 gph). 2 to 3 gpm (120 to 180 gph) would be more realistic.

You're otherwise correct: I'm not concerned so much (not at all actually) with turbulence as I am with flow speed.

I will also attempt to calculate the thermal properties, but I was hoping that you might have some wise words about how I'm going to optimize the flow over the very center of this block.

[bigben2k]

Here's my address (and full thought process!) to #7:


Option 1: extend the fins in the center area into the nozzle, in the shape of a blade.

Pros: will split the flow 4 ways, may add a bit more flow in the center
Cons: it was already split 4 ways. Effect would be negligeable


Option 2: extend the fins (same as #1) but wrap the inner hose tightly around them

Pros: might serve to put more flow in the middle
Cons: no provision for different nozzles, nozzle is tube size


Option #3: add a 1.5 mm needle in the middle

pros: none, really
cons: unnecessarily complex


Option 4: lower the fin height (cone) in the middle

pros: Excellent distribution
cons: no cooling from the fins (no fins!)


Option 5: same as #4, but from the bottom of the fins

pros: ?
cons: effect negligeable, impossible to do?


So the best solution being #4, a cone cut into the middle, there's still a number of issues (or sub-issues):
1-weaker structure
2-no cooling effect from fins

Answer:
The cone does not have to extend down to the baseplate. Is a compromise possible... not really.

How about a ball end mill, 6mm in diameter? Not much different than a cone. A cone cut would leave a triangle that ends in the center. This would be the reinforcement, as an extension from the top.

The structure at that point is not reinforced straight down by the top, regardless of any option, so the structure issue is minor, except for the rigidity provided by the solid main fins, as pointed out by Nicozeg. With a 9/32 nozzle, the radius is 3.57 mm, so with a fin height of 5 mm, the angle would be about 35 degrees from vertical. (relevance?)

Conclusion: cone cut in the center, about 35 degrees from vertical axis.

I still have a couple of options that I'm pondering. More when they're finalized.



Headache time.

[Fixittt]

Ok, I have to add on this too. I have talked with Ben, (Great guy) in PM about making this block. He is going to fund it. Granted its not going to cost an arm and a leg as would any other small order from a machine shop, because I have pulled a few strings.

I basicly told him to finish the design as to how he wants it, and I will try my damdest to make the sucker to his specs. Will it be possable, dont know untill we cut some copper. If it can be done, we can do it. Will it eat a bunch of 1mm endmills, prolly. At least untill we get the feed and depths right. Will it take forever and a day to machine? YUP....... Do I care? NOPE! Will I be proud to be some part of the venture. OHHH YEAH!

[jaydee]

Originally posted by Fixittt
Ok, I have to add on this too. I have talked with Ben, (Great guy) in PM about making this block. He is going to fund it. Granted its not going to cost an arm and a leg as would any other small order from a machine shop, because I have pulled a few strings.

I basicly told him to finish the design as to how he wants it, and I will try my damdest to make the sucker to his specs. Will it be possable, dont know untill we cut some copper. If it can be done, we can do it. Will it eat a bunch of 1mm endmills, prolly. At least untill we get the feed and depths right. Will it take forever and a day to machine? YUP....... Do I care? NOPE! Will I be proud to be some part of the venture. OHHH YEAH!

Yeah I am in to! If you (Ben) can come up with design I can work with I will also attemp to make this thing (and yes, in Copper). My mill works good with tiny endmills even with copper as that is what the thing was made for, small work. 1/8" endmills cut through it like butter so 1mm should work if I can get the mill to run slow enough.

Also fixittt, new website in my sig! If you need anything posted let me know. Slowly getting things moved over. And this site is here to stay! Bought the domain name this time.

[Alchemy]

Originally posted by bigben2k
I have yet to balance the flow in this thing, and it will depend on the size of the nozzle that I use. If I go with a 3/8 inch nozzle, then the flow splits 16 ways, in a 1mm wide channel that is 5 mm high. The copper fins are 1.5 mm wide. As you can observe, because of the 1mm cuts, there is a varying ratio of copper-to-channel from 1.5 to 0.75 . This block might have a nozzle that is 9/32 inch in diameter, which would force the flow to split 8 ways. Nozzle size is not final...

The top rests right on top of the fins, improving structural integrity. It may be made of copper, or polycarbonate. In any case, all channels are 5mm high, and 1 mm wide.

You should notice right away (?) that the flow isn't balanced at the outer edge: the flow is higher along the main 4 fins. I plan to balance this with the right openings in the top.

Flow rate: I will be using a "Little Giant" 2-MDQ-SC, which has a 14.4 feet max head, but otherwise capable of flow rates of more than 500 gph. See specs here I haven't done my homework yet so I can't give you an exact flow rate, but I have been shooting for 5 gpm (300 gph). 2 to 3 gpm (120 to 180 gph) would be more realistic.

You're otherwise correct: I'm not concerned so much (not at all actually) with turbulence as I am with flow speed.

I will also attempt to calculate the thermal properties, but I was hoping that you might have some wise words about how I'm going to optimize the flow over the very center of this block.

I assumed the channels were etched on the bottom to disrupt flow and cause turbulence. I didn't realize the fluid was actually going to be forced to flow within them.

I ran some calculations, and it looks like you're going to have totally laminar flow throughout most of this block - that is, everywhere but the entry where the fluid is striking the center of the block.

I hate to argue, but I really think this design isn't going to work well. You really, really need turbulent flow in this sort of application.

I think you would get improved performance if you affixed the top plate such that there was a gap between the top of the channels and the top plate - 5mm should do. This would also significantly decrease friction and allow for higher flow rates.

How much of a difference it would make, I can't say for sure. Since almost all heat transfer is going to occur directly below the cold water inlet (assuming you're placing that just above the center) most of the heatsink outside that area serves little purpose anyway. But you asked for my advice, so here it is.

Alchemy

[Cathar]

Originally posted by unregistered
I gave Cathar not a single answer (that I recall anyway)
but suggested areas of ‘interest’
which HE followed, and came up with HIS design

About this point:

Perhaps the single most important statement that came from Bill that sticks in my mind as driving the design my block was this:

"Think about how to decrease the thermal gradient of pure copper"

I really have to thank Bill for that statement.

There were subsequent discussions about improving nozzle geometry, but again, these were comments along the line of "Think about boosting water velocity".

So those were the two driving comments behind my design.

There were no direct statements of what to do, and I even requested such of Bill to not tell me anything directly.

[utabintarbo]

Originally posted by Alchemy
I assumed the channels were etched on the bottom to disrupt flow and cause turbulence. I didn't realize the fluid was actually going to be forced to flow within them.

I ran some calculations, and it looks like you're going to have totally laminar flow throughout most of this block - that is, everywhere but the entry where the fluid is striking the center of the block.

I hate to argue, but I really think this design isn't going to work well. You really, really need turbulent flow in this sort of application.

Alchemy

How deep would the channels need to be "etched" to alleviate this problem? Would sand or bead blasting do the trick?

Bob

[bigben2k]

Right on Bob.

I got a PM from Dave, and he pointed out that because the fins don't run across the core (like Cathar's), the fins do not have the same heat dissipation effect. The baseplate thickness is also becoming an issue, where I was shooting for 2 mm, the heat dispersion from the fin pattern doesn't match the heat spread within the baseplate. That's also a reference to the "heat gradient" factor.

As Alchemy so importantly pointed out, turbulent flow may not be achieved. I was under the impression that it could be achieved in one of two ways: turbulators or plain high speed. Can you tell me more? What about Utabintarbo's suggestion?

The 5 mm gap between the top and the fins defeats the structural integrity. I agree that it would give much more flow, but I can also see that most of the flow would occur above the fins, and as such, would decrease the cooling effect.

I got an e-mail from Utabintarbo this morning. The saw blade diameter seriously limits the amount of cutting that it can be used for, because it will either cut into other fins, or into the block's outside wall, with its 20, 25 or 32mm diameter.

With some of the info above, I'm going to temporarily reduce the fin pattern radius to 7.5 mm (15mm diameter), pending my calculations. I'll look into some more ways of improving the flow, with turbulence in mind.

Someone started a thread in the liquid forum, about socket mounts. Check it out

It seems to me that a socket mount is possible, using the Maze3 scheme. I will spec this out later, but that mount is pretty close to what I was aiming for.

Many thanks to BillA, for putting me back on track, as usual. I have much work to do on this block, and I really need to go through the calculations before getting more into it, like I have been here.

[Alchemy]

Originally posted by bigben2k
As Alchemy so importantly pointed out, turbulent flow may not be achieved. I was under the impression that it could be achieved in one of two ways: turbulators or plain high speed. Can you tell me more? What about Utabintarbo's suggestion?

Well, turbulence is determined by a dimensionless value called a "Reynolds number." The exact range between turbulent and laminar flow is disagreed upon in some circles.

According to McCabe, Smith, and Harriott, turbulent flow will occur at Reynolds numbers above Re~24,000. Turbulence can be forced by obstructions in the flow as long as the Reynolds number is well above Re=2,100. Below that, there's no way to avoid laminar flow.

Sieder and Tate define turbulent flow for significant heat transfer to be abover Re=100,000.

In the inner channels, you're going to have Re=2600. In the outer channels, Re=1300.

This makes for an extremely inefficient design - the increase in surface area these channels create won't make up for this.

My *rough estimate* of the heat transfer coefficient between the copper channels and the the fluid is h~4 kW/m^2 C.

Under the very best of conditions, you could get perhaps a 3 degree C difference between the copper walls and the fluid. This might still be acceptable, but I don't think this is going to outperform most WB's on the market.

Alchemy

[nicozeg]

Ben, look at the good side, what alchemy said could be interpreted as: Your block sure is not going to start a revolution, but it could perform just de same that the best currently available.

But I suspect from those numbers, 3ºc between water and copper would be extremely well for 100w heatload. Let`s guesstimate some numbers:

1.5ºc delta in TIM
2.5ºc " inside copper
3ºc " in water
4ºc " in rad.
---------------
10ºc delta temp between cpu and cooling air.

That equals 0.1 C/W

[bigben2k]

Thanks for the guestimate! I need to be able to calculate that, which shouldn't be complicated at all. Knowing thickness and thermal properties, I should be able to build such a gradient.

About Alchemy's post: I don't know if the numbers are different with the flow reversed, I'm really having a hard time putting together a mental picture (lack of sleep?!?).

I am working on some changes. The flow in the center is still a problem, so right now I'm looking at solutions where the flow is reversed, where the inner tube is actually an outlet.

What I gather from Alchemy is that the high speed route isn't practical, and that turbulator(s) would be more practical, given a common range of flow rates. I may yet pull an ace out of my sleeve: what's clear to me is that as soon as one gets into turbulators, there is a potential for a sweet spot, where the turbulence becomes in tune within the channel, within a very narrow range of flow rates.

More later.

[Alchemy]

Originally posted by bigben2k
Thanks for the guestimate! I need to be able to calculate that, which shouldn't be complicated at all. Knowing thickness and thermal properties, I should be able to build such a gradient.

About Alchemy's post: I don't know if the numbers are different with the flow reversed, I'm really having a hard time putting together a mental picture (lack of sleep?!?).

I tried to ignore the effect of the water jet striking the copper just above the core, so I'd imagine my numbers would be more accurate if you made a design that avoided that effect.

If you do design the flow striking the center of the block from above, you'd get better performance than my k=4 estimate.

The basic problem with the design is that you're forcing the flow into channels so narrow that the fluid can't become turbulent.

By the by, Reynolds number is equal to linear velocity multiplied by channel diameter multiplied by density, all divided by viscosity. So to get turbulent flow by increasing flow only, you'd have to increase flow rate a hundred times.

Re = V * D * rho / mu

I am working on some changes. The flow in the center is still a problem, so right now I'm looking at solutions where the flow is reversed, where the inner tube is actually an outlet.

Well, that would be much easier for me to model mathematically, but will probably worsen performance.

What I gather from Alchemy is that the high speed route isn't practical, and that turbulator(s) would be more practical, given a common range of flow rates. I may yet pull an ace out of my sleeve: what's clear to me is that as soon as one gets into turbulators, there is a potential for a sweet spot, where the turbulence becomes in tune within the channel, within a very narrow range of flow rates.

That's my suggestion.

Alchemy

[MadDogMe]

The thing that most worried me about your fin design was that they 'branched out', you'd loose pressure like crazy with each branching, I was going to post before but was unsure of the size/area the barb would cover, if it was small it would of resulted in a single channel branching into four!.

Why not try the calculations on the 'circle cross cut many times style'?, so easy to manufacture!, if the outerwall is in the way, get rid of it!, incorporate it into the plate above(and the O ring cjhannel) 2mm will still be enough to countersink some flush bolts into won't it?. if not: don't get rid of it, just lower it enough for the blades '9 o'clock' point to miss...

I think you're worrying to much about the fins when the real revolution is in the outlet and full balanced use of radial flow...
********************************************

PS. what is the definition of 'Impingment'?...

[morphling1]

Originally posted by Alchemy
I
By the by, Reynolds number is equal to linear velocity multiplied by channel diameter multiplied by density, all divided by viscosity. So to get turbulent flow by increasing flow only, you'd have to increase flow rate a hundred times.

Re = V * D * rho / mu

As I know Reynolds number is v*d/kinematic viscosity

v.... velocity [m/s]
d... diameter [m]
kinematic viscosity [m2/s]

if the chanell isn't round you have to take the equivalent hidraulic diameter d' = 4*A/C
A... cross area [m2]
P... circumference [m]

so for bb2k rectangular chanell d'=2ab/(a+b)
So you can see that narrow rectangular chanell isn't realy too good for introducing turbolence round chanell is much better.
Also to manny channells (to big cross area) reduce water velocity
and again lower Reynolds. So in your case the flow would be lamilar IF the fins would be long and that kind of design. But with central nozzle and short paths I realy don't think that there would be lamilar flow in that kind of block

[myv65]

Originally posted by morphling1
As I know Reynolds number is v*d/kinematic viscosity

v.... velocity [m/s]
d... diameter [m]
kinematic viscosity [m2/s]

if the chanell isn't round you have to take the equivalent hidraulic diameter d' = 4*A/C
A... cross area [m2]
P... circumference [m]

so for bb2k rectangular chanell d'=2ab/(a+b)
So you can see that narrow rectangular chanell isn't realy too good for introducing turbolence round chanell is much better.
Also to manny channells (to big cross area) reduce water velocity
and again lower Reynolds. So in your case the flow would be lamilar IF the fins would be long and that kind of design. But with central nozzle and short paths I realy don't think that there would be lamilar flow in that kind of block

I'm pretty good with fluids, but will not go so far as to guarantee all that follows is 100% correct. Consider another "educated viewpoint".

First of all, your equation is the same as Alchemy's. The two viscosity values differ only in that one already includes the density value.

Second, the hydraulic diameter equation applies to converting odd shaped channels to an equivalent sized round one when calculating pressure drop vs flow rate, but not for calculating the Reynolds number. The Reynolds number is based on a "characteristic" dimension, which is open to some interpretation. In a round passage, it is diameter. In a square passage it is leg length. In rectangular (or any other odd) passage, it is not so easily estimated.

When the aspect ratio gets large (one rectangle leg vs the other), the characteristic dimension tends to become dictated by the short leg. eg, if you had two channels, one 1 cm by 10 cm and the second 1 cm by 100 cm, and defined flow in terms of liters/cm of width, each channel would have pretty much the same Reynolds number despite having dramatically different hydraulic diameters.

Alchemy has been talking about laminar flow. This is an area that I believe is greatly misunderstood and rarely have I seen what I feel are correct statements made about it in various forums. The Reynolds will tell you the flow regime (with some room for intepretation), but only for a uniform, undisturbed run of plumbing. Laminar flow will be upset by any change in cross sectional area, shape, or sometimes even deviation from a straight path. Laminar flow takes time (rather distance) to develop following a change in the flow passage. This time/distance may be exceedingly short if the Reynolds number is very low, but still exists. The very thought of having completely laminar flow in most blocks that I've seen is absurd.

All you need to do is take a look at what defines laminar flow. In my understanding, it is "flow along streamlines" (insert Ghostbusters joke here). In layman's terms, this means that a given "particle" of fluid remains in the same precise 2-d location relative to the the "side walls" that define its pathway. Turbulent flow means that the true path of any given particle may not be analytically determined (ie: it's random). These are broad definitions and there is a possibility for both conditions to co-exist in a given setup (at different locations or different times). Specifically, because fluid at a surface essentially has zero velocity, you'll always have a laminar region within the boundary layer of a turbulent flow regime. The thickness of this laminar portion will vary with Reynolds number. Perhaps this is what Alchemy has been driving at.

I'll admit, it's been a long time since I took a hard look at the distinctions between laminar and turbulent flow, but that's how I remember it. I'd appreciate any comments/corrections.

[morphling1]

Ups I missed that Alchemy didn't use kinematic viscosity, but rather dynamic viscosity; kinematic visc. = dyn. visc. / denstity.
So that's the same equation.

But I agree that lamilar flow cant' occur in waterblock. As I know lamilar flow is actualy very hard to achieve, but there is rather more turbolent or less turbolent flow. Unideal surface quality has a lot to do with this too.
Definition of Laminar flow is following: this is the flow where particles are moving in infinetly thin layers which slides between themself without mixing .

With turbolent flow particles are moving iregulary in all directions

I hope I wrote correctly so it is understandable (english isn't my native language)

[bigben2k]

Many good comments, thanks to all.

What's obvious here is that turbulence from speed is directly proportional to flow rate. If I had a target Reynolds number, which I don't right now, I'd have a better idea of where I'm headed. It'll come, in time.

MadDogMe: the flow speed is reduced in the outer channels on purpose. The speed of the coolant is highest where it is important for it to be. Having more channels in the outer area reduces the overall pressure drop, or flow restriction.

There is a certain logic behing round channels: since a circle is the optimal shape for the greatest area with the smallest perimeter, the boundary layer is reduced to a minimum.

As for Radius' Reynolds number, estimated to range between 2600 and 1300 throughout the design, as Alchemy says, there's some error. In the design, I was hoping that the 90 degree bend from the center inlet would have some effect.

What I'm shooting for (and forgot/put-aside in this design) is the addition of turbulators specifically to create vortices over the baseplate and fins. I've been doing a lot of reading about vortex flow meters, and I'm picking up gobs of good information.

Alchemy: I'm going to refer you to Cathar's block Click me! . I think you'll see some similarities, and some differences. Maybe you could give us some comments on it?

Some notes:
-1mm baseplate
-channels/fin width = 1 mm
-Center inlet, dual outlet
-7 fins, 8 channels.
-channel depth = 5 mm

Myv65: You wrote "Laminar flow will be upset by any change in cross sectional area, shape, or sometimes even deviation from a straight path". That reminded me that the channel width in this design varies from 1.0mm to 2.0mm. I still plan on adding more turbulence, but I'd like to know your opinion on this varying channel width, as it relates to turbulence.

To throw the discussion into turbulence, I'll post a link to this most interesting article by Mike Larsen.

In the mean time, I'll post a link to Nicozeg's thread, and his excellent waterblock design.

Click me!

Some notes:
-the base of the block has ridges, to create turbulence.
-The top is conical, not flat.
-there are no fins



Here's a preliminary idea of a revision to Radius.

[bigben2k]

Googl'ing through the web, it seems that turbulent flow is achieved somewhere between Reynolds 2000 to 4000, as far as I've searched (opinions DO vary!).

Here are some of the links that I found.

http://www.mas.ncl.ac.uk/~sbrooks/bo...p07/node9.html
("Turbulent Reynolds stress" for Dave!)

http://www.wikipedia.org/wiki/Reynolds_number
(basic definition)

http://www.ichmt.org/abstracts/MECT-...tracts/2-2.pdf
(You'll like this one Dave!)

http://www.nag.co.uk/simulation/Fast...html/node8.htm
("Theory of laminar and turbulent flow")

http://psdam.mit.edu/2.000/Administr...ulent-Flow.pdf
(simplistic, but there)

http://www.efm.leeds.ac.uk/CIVE/CIVE..._turbulent.htm
(dye experiment)

http://www.sigmaxi.org/amsci/article...demenos-5.html
(a medical perspective!)

http://wuche.wustl.edu/~sato/flowtrans/flowtrans2a.html
(Reynold's experiment)

http://www.icase.edu/Dienst/Reposito...e/TR-99-33/pdf
("Streamwise Vorticity Generation in laminar and turbulent jets")

http://home.olemiss.edu/~cmprice/lectures/turb.html
(some basics about turbulent flow)

http://www.uts.com/products/tkintro.html
(A software)

http://www.me.mtu.edu/courses/me328/...328formula.pdf
(A formulae roundup)

[myv65]

Originally posted by bigben2k
Myv65: You wrote "Laminar flow will be upset by any change in cross sectional area, shape, or sometimes even deviation from a straight path". That reminded me that the channel width in this design varies from 1.0mm to 2.0mm. I still plan on adding more turbulence, but I'd like to know your opinion on this varying channel width, as it relates to turbulence.

To throw the discussion into turbulence, I'll post a link to this most interesting article by Mike Larsen.

I have never spoken (at least that I know of) to Mike Larsen. I'll say only a couple of things about that article, which I did read quite some time ago.

One, those diagrams look suspiciously similar to those that exist in the fluids text I used in college. [edit start] Glad to see credit was given to the source. [edit end]

Two, all those diagrams have the same basic premise. They all pertain to an "infinite flow field". This means the conditions upstream of the "x=0" or the "entrance point" are uniform. Once you toss out this premise (as will happen anytime you go through a bend or real life fitting) things get a whole heckuva lot more interesting and complicated.

To put it bluntly, I thought it was a decent discussion but rather misleading. Call it the difference between understanding and applying concepts. Pretty much all students that make it through introductory fluids will understand the concepts of laminar/turbulent, entrance length, etc. Not too many really get an appreciation for the practical aspects of how these things exist in real life.

A lot can happen when trying to write technical stuff for a non-technical audience. Believe me I know. Perhaps Mike has a solid grasp on all of this and didn't wish to bog down the readers. I can't say for certain.

[utabintarbo]

Originally posted by myv65
I have never spoken (at least that I know of) to Mike Larsen. I'll say only a couple of things about that article, which I did read quite some time ago.

One, those diagrams look suspiciously similar to those that exist in the fluids text I used in college. Makes me wonder why there's no bibliography covering what are obviously copywrited diagrams.

From the end of page 2:

All images courtesy of "Fundamentals of Heat and Mass Transfer" by Incropera and De Witt.

Just so nobody gets the wrong idea!

Bob

[myv65]

I heartily retract point one from above. My eyes and brain may not be good enough to recall that part of the text, but at least I remembered the diagrams.

[BillA]

and the above is why, despite the passage of 50 years, that
"Flow of Fluids through Valves, Fittings, and Pipe"
- Crane, Technical Paper No. 410
is still a reference today, in print, and as interactive software
(~$450 as I recall, I use the book @ $40)

as an experimentalist, it is most informative

EDIT:
I do know Mike, he posts on OC and OCAU as Aesik
one needs to note the intro
"the basic physics behind flow in a water cooling system"
it was written for those with no technical education - how far can a single article go

for some background the OC threads on 'turbulence' are illustrative
here are a few words by Mike (Aesik)
(and the usual misbehaving types)