Moronic Tuning "Advice" WARNING! (Related to RX7Club)

[vex]

Originally Posted by dr.occa

I must have wondered into the wrong room. I heard something about hockey pucks...I like the two I picked up for a buck fiddy each.

I'm not so sure I'd jump in the same boat regarding the comment about air and water having the same exact flow characteristics especially when water's own natural surface tension is a quantitative variable to factor in. Shouldn't surface tension be factored in since it's most likely a contributing factor to water pump cavitation issues? Speaking from a post (even pre) combustion side, even the weight of spent gas is an important variable to consider when flow testing.

Again, surface tension is not what he stated. Surface tension is nothing more than two different mediums interacting with each other. You get the same effect when different densities are present; for instance salt and fresh water or nitrogen and helium. Note that the surface tension between the two mediums becomes negligible as their densities approach unity. This is simple incompressible flow.

Water obeys the same fundamental laws as air does (energy, mass, and momentum). Hence why both mediums have circulation, currents, laminar and turbulent flows, etc, etc, etc. They both flow exactly the same. As I stated earlier you can prove this by solving for the Reynolds Number (which is a dimensionless number that accounts for the various medium's density) and applying it to both water and air. The results will be exactly the same. In fact, this is how engineers do various testing.

Anyway, I guess that might be considered splitting hairs on my part. Am I wrong in this?

It depends where you're looking at it from. From a flow stand point; both air and water flow exactly the same. From a atomization mixture stand point you are correct in that water and air will not necessarily travel the same path from an Eulerian perspective; however that does not negate the fact that they still flow exactly the same. They still are adhering to the fundamental laws which dictate flow path and direction.

[dr.occa]

Originally Posted by vex

The results will be exactly the same. In fact, this is how engineers do various testing...

So will liquid also emulate the same exact areas of turbulence as air in flow testing?

I'm asking not because I'm doubtful of the previously mentioned method of water injection. I'm primarily putting forth these questions for more clarification when considering the accuracy of flow testing results. I don't want to settle because it's what's been accepted for ions. It would be better to scrutinize and challenge the findings and let them stand on their own merits rather than what's spouted/parroted off by a lineage of engineers in an informal daisy chain if you know what I mean. The world is much too dynamic to take it for granted that it's ALWAYS going to do what's expected every time.

[Mazdabater]

Originally Posted by vex

Again, surface tension is not what he stated. Surface tension is nothing more than two different mediums interacting with each other. You get the same effect when different densities are present; for instance salt and fresh water or nitrogen and helium. Note that the surface tension between the two mediums becomes negligible as their densities approach unity. This is simple incompressible flow.

Water obeys the same fundamental laws as air does (energy, mass, and momentum). Hence why both mediums have circulation, currents, laminar and turbulent flows, etc, etc, etc. They both flow exactly the same. As I stated earlier you can prove this by solving for the Reynolds Number (which is a dimensionless number that accounts for the various medium's density) and applying it to both water and air. The results will be exactly the same. In fact, this is how engineers do various testing.

It depends where you're looking at it from. From a flow stand point; both air and water flow exactly the same. From a atomization mixture stand point you are correct in that water and air will not necessarily travel the same path from an Eulerian perspective; however that does not negate the fact that they still flow exactly the same. They still are adhering to the fundamental laws which dictate flow path and direction.

You must have missed reading those parts.

[dr.occa]

Originally Posted by Mazdabater

You must have missed reading those parts.

Not at all. It's called dotting your "I's" and crossing your "T's".

"Knowledge" can be bad for the ego apparently: by puffing it up and giving those who have gained any information from others a false sense of self-importance.

"Stupid" questions should be asked along with the "Not-So-Stupid" questions. That way you can better distinguish between them. Especially so in a public forum so that others can witness the difference and avoid repeating them.

Off to find wisdom somewhere else. I'm sure there are more people out in the internets that are wrong that ya'll need to take care of or something...

[Herblenny]

Originally Posted by dr.occa

The world is much too dynamic to take it for granted that it's ALWAYS going to do what's expected every time.

I agree with you. I'm in Molecular Bio/Genetics and things that worked 10 years ago now doesn't work. Physics, chemistry, etc... in theory a lot stands in place, but some just doesn't work in the real world.

[vex]

Originally Posted by dr.occa

So will liquid also emulate the same exact areas of turbulence as air in flow testing?

Yes. They flow exactly the same, one just needs to match the Reynolds number. All calculations concerning flow of a medium use Reynolds number as the basis of calculation. This accounts for the density alterations between the two mediums.

I'm asking not because I'm doubtful of the previously mentioned method of water injection. I'm primarily putting forth these questions for more clarification when considering the accuracy of flow testing results. I don't want to settle because it's what's been accepted for ions.

Ions have nothing to do with anything you're talking about unless you're considering hypersonic velocities (I believe you meant eons).

It would be better to scrutinize and challenge the findings and let them stand on their own merits rather than what's spouted/parroted off by a lineage of engineers in an informal daisy chain if you know what I mean. The world is much too dynamic to take it for granted that it's ALWAYS going to do what's expected every time.

Unfortunately this is pretty standard flow knowledge. It's been done this way for ages because this is the correct way to do it. The mathematics behind it model natural occurrence very accurately. Laminar, and boundary flow are very well explored and mathematically modeled with no issues. These laws hold true regardless of what Newtonian fluid is being considered. There are of course exceptions to this but they are non-Newtonian in nature. These include things like Liquid Helium and other super fluids.

Back to the proposed comment "Water does not flow like air" is absolutely false. Point in fact the original exploration of air flow was done with water and the results extrapolated out to air, which was then tested and confirmed. Now-a-days with the proper instruments and technical ability we can test air independent of water, however, what we learn from air only reinforces what we already have known. That is, if you solve for a particular flow using the Reynolds number you can match any medium you want to the same exact flow. This means I can not only match water and air, but I could also match oil, nitrogen, helium, oxygen, etc, etc, etc.

Here's something to consider: Air (mostly composed of nitrogen, and so nitrogen is used), has a molecular weight of 14.0067 g/mol, and water has a molecular weight of (1.00794 g/mol)*2+ 15.9994 g/mol (or 18.01528 g/mol), flow exactly the same. However if we take the hypothesis of "water does not flow like air" we by extension must emphatically state that the components of water do not flow like air. This means hydrogen and oxygen do not follow the same laws as nitrogen. This is obviously false, as both hydrogen and oxygen flow exactly the same as nitrogen when one matches the Reynolds number. Since water is a Newtonian fluid as well one can do the same. Another thought experiment; what if water was turned gaseous? Would the flow be any different? No. The medium is water, but just in its gaseous state. One need only match the Reynolds number and the flows will be exact.

Now for turbulent flows:

Turbulent flows are a bit harder to model as they are equivalent to white noise in radio. They therefore remain random when looked at molecular level Eulerian perspective. This means statistical analysis is done on the medium using various fluid properties (and other boundary conditions) to determine the numerical basis of the turbulent region of concern. What I'm basically saying is that all Newtonian fluids that experience a turbulent region of flow will behave exactly the same. This means that when the Re is matched, the flow (regardless of density) remains the same. Turbulent Boundary regions, Turbulent flows, Laminar Flows, they flow the same. This is how fluids work.

The exceptions to this rule however do exist. They include super fluids, or fluids that have almost no viscosity. These fluids are never used inside of commercial engines and play no part in the discussion at hand, but they do bear mentioning. They do not behave the same as regular Newtonian fluids. For more information concerning these fluids I suggest reading the wiki-article concerning them.

[vex]

Originally Posted by Herblenny

I agree with you. I'm in Molecular Bio/Genetics and things that worked 10 years ago now doesn't work. Physics, chemistry, etc... in theory a lot stands in place, but some just doesn't work in the real world.

From my knowledge on the subject thus far; the only big change is when Caloric theory was killed off by thermodynamics.

All flow experiments and research have only reinforced what was first discovered all those years ago by people by the name of:

Bernoulli
Mach
Reynolds
Froude

Just to name a few. Unless something drastic were to happen tomorrow such as the laws of Thermo Dynamics were found to be wrong, the flow laws and mathematics will remain intact.

[RETed]

Okay, I cleaned up the recent drama and hopefully left the flow of the thread intact.

Now back to our regularly scheduled programming...


-Ted

[Slides]

I know the above is a bit old now, but making arguments about the flow characteristics of air and water in entirely separate environments with matched Re numbers flowing as single fluids is entirely besides the point taken from the other forum regards water/charge distribution between cylinders/chambers rotors/whatever. I am a degreed mech eng, i get that, but it is entirely irrelevant to the original point someone was trying to make regards our fluid injection application.

By chance I found a very flawed post by lawyer in hte ai section of rx7club and replied before reading this thread, suffice to say I don't agree with him on all but the fact that mass distribution of an injected fluid (in the context of water injection in air/fuel SI turbo engines), be it water, meth, petrol, pepsi or whatever between airstreams into different runners/ports/whatever is effected by flow paths/profiles/shapes.

In an automotive, pre-plenum, over-saturated, be that equilibrium condition or quasi due to fluid particle surface area evaporation limitation giving remaining non gaseous particles fluid injection application, it is expected that high density suspended particles will not follow your streamlines of the main gas/fluid flow in which they are suspended, that is how centrifuges work. It is entirely reasonable, if used in an application where gas accelerations vary between flow paths to assume that, if the fluid injection is being relied upon for knock suppression an imbalance in fluid distribution between chambers/pistons/whatever could cause problems for the running of the engine system if air flow (and thus combustion conditions/required heat dissipation/knock limit between pistons/rotors/chambers) would otherwise be equal. In the case of most mazda 2 rotor throttle/plenum setups it doesn't really bother us due to their geometry (perhaps the short radius intake hat holley type throttles might experience this problem however), but in the case of piston engine intake manifolds, it could.

[Kontakt]

Thanks Slides. Reading through this thread that was the #1 point on my mind the whole way through.

Water in water may flow the same as air in air, but water in air does NOT flow the same as air in air.

Correct me if I am wrong, but if it is primarily the temperature reduction of the intake charge that is sought, and evaporation is attained in large part, then we are talking about water vapor vs air. Those two have much closer densities and flow together much better than water droplets in air. Rain falls, clouds float.

If that isn't the goal of it all, then why not just run a high pressure steam system for your injection. No pump necessary, just a boiler. (joking)

[dr.occa]

I had forgotten about this thread so sorry for yet bumping it.

For me vex clarified quite a few questions I had and actually I focused on what exactly it was I was getting side tracked by - the speed of flowing liquids/gases, etc...I believe for me I lost track of the purpose of flowbench testing: which (correct me if I'm wrong) is discovering points of restriction, poor port activity and where they can and need to be improved for a desired performance target. Water, which is easier to contain, control as well as observe than air/gas will display the necessary characteristics of flow.

I realized I'm not looking to alter what it is that'll be flowing through the engine because all I'm looking for is flow PATH. Water will show me that path because it will take same route(s) as air.

It's an "ah ha!" moment for me. Thanks vex.

Oh, and you're right, I did mean eon/aeon. I just now saw that I goofed that up.