Laminar Flow Vs Turbulent Flow

[Space Goat]

ive done a few searches around and come up empty handed so ill make it simple...

What flow is better though your intake piping turbulent or laminar (straight, smooth flow)???

in my opinion and this is just assuming so correct me if i'm wrong laminar flow would allow a quicker flow through your intake piping/cooler ect. however turbulent flow would give a better fuel mixture but slow the flow of the air going through your intake...

or does it make no difference... what sort of power figures do people start worrying about these issues?? or dont they??? im guessing it would do sweet "f" all to a shitbox hyundai or sumthing....

cheers Rick

[djr81]

Whether a flow is laminar or turbulent depends on the Reynolds number for the particular circumstance. So maybe start looking for that.

[SECURITY]

from the logic thats twirling around in my head i think that the intake will need to be laminar so the turbo picks it up easier. wont a turbulent intake cause some kind of restriction?

as for the intercooler pipes.. the air is pressurised so luminar or turbulent airflow isnt really an issue because you really just want the quickest easiest flow.

the air is made turbulant to mix with the fuel by the intake port as it is quite . some people out there dont port and polish the intake side because they believe that the air is made turbulent before it enters the combustion chamber by how coarse it is. the exhaust side is usually ported and polished more to help the air escape more efficiently.

but thats just what i have made sense of, and what makes sense to me.

[nikr33turb]

from what i can figure stright smooth flowing would be more benificial... i know it defiantly is on the exhaust side hence why mandrel bent is preffered to make it flow faster. I presume it would do the same on the intake and more flow = more power (from what i know anyways) please correct me if im wrong : )

[WRRR]

In an ideal world I think you will find laminar flow will provide the lowest pressure drop for a given volume of fluid moved at a given velocity.

With a car I think you will find space governs how far you can go.

Remember bigger is not always better as with a forced induction engine you have the interia of the air mass you are pushing through the system to overcome. ie really big intercooler, pipe and intake volumes will increase lag time as you have to get all that mass moving.

Sharp changes in direction, edges, gasket ridges,etc all promote turbulent behaviour so minimising those all helps no matter what system. ie match porting and so on.

Hope this helps

Cheers

[QWK32]

even on the pressurised side you don't want turbulent flow. turbulant flow can generate heat aswell as pressure drop and resitriction. and heat is one thing that we don't want. on the intake turbulance could in worst case senario create somewhat of a restriction of flow. i'd say for and intake pipe least amount of bends, if bends are needed don't make them sharp, if welding the pipes try to smooth out the welds/slag on the inside.

[RB30-POWER]

may or may not be directly related to what you guys are talking about

but, alot of newer cars now that are emissions friendly, have tumble or swirl valves to help air fuel mix and gain better emissions and lower fuel economy.

on the honda lean burn engines, they close one valve altogether to aid swirl and they run 22:1 air fuel ratio under light cruise conditions.

all the above is good, but hard to implement in the aftermarket so your stuck with the base motor you have from factory.

[vinnie32GTS4]

when i was doing my work experience for school and my VET Course (automotive servicing and repair) at a mitsubishi dealership/service centre a few mechanics and i were talking about this (intake manifolds tho) and they all said with a turbocharged engines there needs to be some turbulance in the intake manifold so dont get the intake manifold smoothed and polished etc.

hope that helps even if its not about intake piiping but the manifold lol

but witht the pipin i would guess you would want it smooth and then have turbulance in the intake manifold.

[T04GTR]

turbuant. laminar flow is not benificial for intake. the more turbulant it is the better cylinder filling you get. remember the intake flow is pulsed. so if its wirling around it grabs the most posible thats available. thats also the same principle for larger intke plemums. its got more reserve to grab.

[T04GTR]

yeah, piping lamilar. soon as it hits the manifold you want to to tumble around as much as posible.

[Bass Junky]

Having super smooth walls on air passages can actually cause a drop in flow because the air 'sticks' to the walls.

You need enough 'roughness' on the walls to allow some turbulance to assist the flow. This isn't to say that a cast finish on the inside of your head is a good thing, but something you can see a reflection of yourself in can be a bad thing.

Turbulent flow can assist in fuel mixing, and the new 2.0 Litre TFSI (Turbo Fuel Stratified Injection) Golf GTI engine features valves in the head which open and close according to the power requirements, closing when low flow is required for better velocity of air, and opening when high power is required for more volume of air.

These valves are infinitely adjustable, and actually between the plenum and the head ports.

[wolverine]

i'm with dave.

turbulent flows provides the swirl is to aid in homogenising the mixture so i'd think it's a good thing entering the cylinder.

i would have thought the smoother the intercooler pipe work the higher the flow, roughening the walls slows the flow.

BMW F1 turbo engines had intercooler piping with fine ridges on the inner radius of their bends. this was done to slow the air down slightly here as this maintains a more laminar flow.

[Roy]

You actually want turbulent flow in the intercooler as well

[LiQuid IcE]

I'm guessing a lot of you have done Engineering? Or engineering subjects??

I'm studying this stuff at the moment and all I can say is Thermo-Fluids freaking suks dog balls

[sh@un]

The only turbulence you want is inside the chamber, to aid combustion. Turbulence anywhere else is just adding to the pumping losses and costing you power.

[GeeTR]

I’m no engineer, but i would have thought large scale turbulence anywhere would increase pumping losses regardless, its just the stronger and more complete mixture burn from a thoroughly even mixture of fuel and air negates this loss.

Some are assuming the only cause and assister of turbulence in the chamber is the inertia of it entering past the intake valves. The act of the chamber floor (piston top) going through BDC and then squashing the charge against the head chamber itself, creates the more substantial eddy currents (swirling from centre to outside) I believe. Due to laminar skin friction, the pressure front caused by the piston is centred in the middle, it hits the spark plug and flows outwards (like a outwardly flowing vortex in a smoke ring) I saw a video when I was a kid of glass cylindered combustion motor that BMW made. Watching the combustion of this vortex of fuel and air was quiet beautiful.

With the above in mind, turbo motors with 1.7bar boost levels and fuel at over almost 70psi rail pressure don’t need excess turbulence, the nature of high RPM air speeds, boost and the turbulent effect of in chamber mixture compression does this for us.

Added turbulence through swirl inducers and phased intake valve opening is clearly to aid tumble and roll at low air speeds. Manufactures do it for emissions mostly, hence why id suggest in the in high performance world, inducing turbulence isn’t really needed (when in comparison to the negative effect it could have at higher engine speeds)

Sticking to the high performance at high engine speeds theme, full blow turbulence isn’t required in an intercooler as the natural resultant increase of surface areas when the intake charge goes down each intercooler runner is enough. Iv personally seen a fair few different variances of “in runner” turbulators. I think it was the TX5 turbo which had quiet evasive and restricting looking little devices. I would think there would be a pretty clear weighting in of “Turbulence at low air speeds for increased heat transfer VS Increased drag at high airspeeds”

On a final thought, remember surface irregularities can be used to reduce friction and increase flow over a surface. The dimples in golf balls, and knives use this.

Eddy producing dimples can also increase heat transfer measurements without the large expectant increase in drag as per >> http://pdf.aiaa.org/preview/CDReadyMCFD03_...PV2003_3964.pdf

All my morning cents gone

Edited September 27, 2007 by GeeTR

[discopotato03]

My 2c , laminer flow because the shortest distance between two points is the direct path . Turbulent air or fliud has to go further because the direction its moving in is not necessarily the shortest distance if you know what I mean .

Barrier flow . Fluid/gas tends to form a slow or non moving layer against a rough surface and it sort of lubricates the main flow mass from the barriers surface . Heat exchangers such as intercoolers/coolant radiators/oil coolers have "turbulators" inside their tubes to add a lot of surface area for extra exposure to the gas/liquid beeing cooled . Its the reason why a core with lots of narrow tubes works better than a core with fewer large tubes - note intercoolers made from truck cores with large tubes , great for flow but often not the best for heat transfer .

The effects of swirl and fuel/air mixing is largely up to how the ports and valves are designed - most production inlet manifolds seem to have the injectors close to the head so much of the inlet manifold is said to be "dry" air only . Wet systems ie single point EFI or Carburettor/s have a few more issues with keeping the fuel in suspension with the charge air .

There are some big advantages with GDI or gasoline direct injection because the system become more like a Diesel in that the whole inlet tract is dry . You don't have to time the injection to have any bearing on fuel being carried into the cylinders - its already there . There is also the sizable advantage of being able to control inlet air throttling purely with the inlet valves though thats pretty complex in itself . More potential VE .

Cheers A .

[GeeTR]

Cool, we all agreence then hahaha. Laminar flow everywhere is wanted in a performance environment, as designing for turbulence at low speeds at the sacrifice of high rpm power is for gurls.

Disco - do you really think though that simple intake valve alterations are the biggest determintor manufactures use to promote swirl? I still would have though it to be chamber / piston design; keeping in mind too much swirl at high speeds cause the charge to reach super sonic speeds and increases chance of uncontrolled ignition.

[ryano]

Gday just skipped a few reply's so hope no ones allready talked about it. That is a swirl air thing. My dad was gunna buy a swirl air for his camry intake as he does alot of long distance driving to try for better fuel economy. He didnt buy one but instead copied the design and made one out of a baby food can and a drink can( not recomended for forced induction). Not sure exactly how he made it but it just sits in the intake pipe and the fins inside (almost like turbo wheel blades) make the air twirl before entering the intake. He now gets better fuel economy on his trips down south. So yeah I think turbulant is better for combustion.

[GeeTR]

Gday just skipped a few reply's so hope no ones allready talked about it. That is a swirl air thing. My dad was gunna buy a swirl air for his camry intake as he does alot of long distance driving to try for better fuel economy. He didnt buy one but instead copied the design and made one out of a baby food can and a drink can( not recomended for forced induction). Not sure exactly how he made it but it just sits in the intake pipe and the fins inside (almost like turbo wheel blades) make the air twirl before entering the intake. He now gets better fuel economy on his trips down south. So yeah I think turbulant is better for combustion.

Gday,

Ups to your dad, nice work! Though theres no doubt bit of extra turbulence helps at low rpm with economy. Its if it's warranted on forced induction motors at the expense of power / det at high revs.