Tube for thought

[bsharpish]

I get involved in aerodynamic (and fluid dynamics) from time to time.

Usually it's issues surrounding accuracy on fiscal metering stations involving ultrasonic,coriolis and orifice based technologies.

to cut a long story short ... you need to think about laminar flow, vortex induced swirl and ,with those strakes, the impact of vortex shear on turbulence ( part of von karman street vortex issues).

Essentially, the strakes may throw numerous small vortices into the flow path which could be useful in the event of harmonic resonance but may actually slow down the velocity ..... might improve fuel air mixing though

tnen again - its late, I'm tired and none of this may apply

[Blue Falcon]

I get involved in aerodynamic (and fluid dynamics) from time to time.

Usually it's issues surrounding accuracy on fiscal metering stations involving ultrasonic,coriolis and orifice based technologies.

to cut a long story short ... you need to think about laminar flow, vortex induced swirl and ,with those strakes, the impact of vortex shear on turbulence ( part of von karman street vortex issues).

Essentially, the strakes may throw numerous small vortices into the flow path which could be useful in the event of harmonic resonance but may actually slow down the velocity .....might improve fuel air mixing though

tnen again - its late, I'm tired and none of this may apply

might improve fuel air mixing

The whole point in 5 words....outstanding.

[Blue Falcon]

I just blew my own mind..... DIMPLES .... like on a golf ball..... throughout the intake area. Turbulence would not allow any fuel to pool and would provide maximum mixture. would have to throughout the entire intake area.

just looked this up...it's already a thing.

[mmattockx]

Was showing some people today and we cant decide if this be wierd or wonderful as a "improvement"

I will go on record as saying this will do SFA overall, and very possibly be a negative. You can't get significant amounts of swirl with those tiny little ridges in the stack and it will introduce significant turbulence into the boundary layer along the walls, likely reducing the amount the stacks flow. The point of a velocity stack is to smooth the flow (ie - reduce turbulence) and allow more air in for any given pressure difference from atmospheric to the carb throat. This is working against that goal.

The second model with the grooves in the bore won't do anything at all regarding swirl as the air will simply pass over the grooves with no effect. It also shouldn't hurt anything, either.

That additional velocity is through the rotating vortex which is essentially at right angles to the axial flow so the net is a cork screw of flow, with apparently much lower pressure. That Is if the receiving side will support the flow.

My 1100E has an intake velocity of ~ 22m/s @ 9000rpm (assuming steady flow, 100% volumetric efficiency and 34mm carb bores). Because the total velocity vector will be the square root of the sum of the squares you will need an unobtainable amount of swirl to significantly lower the pressure beyond what it achieves without the swirl. To achieve a 1% increase in the total velocity over the 22m/s you need a tangential velocity (the swirl velocity) of 3.12m/s. In a 34mm bore that equates to a swirl of 1750RPM. And only the very outer portion of the bore achieves that much velocity increase, the rest drops off with the radius it is swirling at from the bore centerline.

to cut a long story short ... you need to think about laminar flow

Velocities in the stack will be high enough that the boundary layer should be fully turbulent before it ever gets to the carb throat itself.


If someone wants to do the fluids calcs to prove me right or wrong on the boundary layer, feel free. Also someone redoing my calcs for the intake velocity and swirl velocity would be welcome as well. As bsharpish says, it is a bit late.


Mark

[posplayr]

I just blew my own mind..... DIMPLES .... like on a golf ball..... throughout the intake area. Turbulence would not allow any fuel to pool and would provide maximum mixture. would have to throughout the entire intake area.

just looked this up...it's already a thing.

IIRC, Golf ball dimples are used to convert laminar (smooth flow) to turbulent (chaotic flow) by "tripping the boundary layer". In boundary layer theory, turbulent flow has more energy and can stay attached to the ball longer as it flows around to the back of the ball. This reduces pressure drag. Pressure drag is not really present in a venturi.

On the other hand many guys that do head porting leave ports purposefully rough to improve flow mixing (i.e. turbulence). To a limit it is beneficial.

As pointed out already, trying to spin the flow with vaning or tubes or grooves will also create a certain amount of turbulence along with the axial vortex.

The bottom line is that if you try and create a vortex, you probably increase turbulence and flow at the same time. (some combination of better gas mileage and better power).

The one I bought years ago did not seem to do anything for my 440 4B, but others have reported benefits that could certainly be attributed to the vortex action.

[posplayr]

My 1100E has an intake velocity of ~ 22m/s @ 9000rpm (assuming steady flow, 100% volumetric efficiency and 34mm carb bores). Because the total velocity vector will be the square root of the sum of the squares you will need an unobtainable amount of swirl to significantly lower the pressure beyond what it achieves without the swirl. To achieve a 1% increase in the total velocity over the 22m/s you need a tangential velocity (the swirl velocity) of 3.12m/s. In a 34mm bore that equates to a swirl of 5500RPM. And only the very outer portion of the bore achieves that much velocity increase, the rest drops off with the radius it is swirling at from the bore centerline.

Mark

OK I refreshed my memory (it was blearaly correct).

An ideal (potential flow) vortex has a velocity profiles of 1/R (R is distance from the center) so even in practice it gets pretty high velocity (lowering the pressure) right at the center. V can't go to infinity because viscosity starts to come into play.

Vortexes are a fundamental part of fluid dynamics and is what is used to explain circulation which is what generates Lift.

Those aircraft wing tip vortices have a lot of energy in them just generated by the spanwise flow, rounding the tips of the wings.

[Blue Falcon]

IIRC, Golf ball dimples are used to convert laminar (smooth flow) to turbulent (chaotic flow) by "tripping the boundary layer". In boundary layer theory, turbulent flow has more energy and can stay attached to the ball longer as it flows around to the back of the ball. This reduces pressure drag. Pressure drag is not really present in a venturi.

On the other hand many guys that do head porting leave ports purposefully rough to improve flow mixing (i.e. turbulence). To a limit it is beneficial.

As pointed out already, trying to spin the flow with vaning or tubes or grooves will also create a certain amount of turbulence along with the axial vortex.

The bottom line is that if you try and create a vortex, you probably increase turbulence and flow at the same time. (some combination of better gas mileage and better power).

The one I bought years ago did not seem to do anything for my 440 4B, but others have reported benefits that could certainly be attributed to the vortex action.

Sharkskin intake

dimpled valves

its a thing already

[Blue Falcon]

OK I refreshed my memory (it was blearaly correct).

An ideal (potential flow) vortex has a velocity profiles of 1/R (R is distance from the center) so even in practice it gets pretty high velocity (lowering the pressure) right at the center. V can't go to infinity because viscosity starts to come into play.

Vortexes are a fundamental part of fluid dynamics and is what is used to explain circulation which is what generates Lift.

Those aircraft wing tip vortices have a lot of energy in them just generated by the spanwise flow, rounding the tips of the wings.

we are flying air through a cylinder not an airplane lol... on that note... why not add a honeycomb to the stack? with dimples

[posplayr]

Sharkskin intake

dimpled valves

its a thing already

Have at it.

[Blue Falcon]

Have at it.

couldn't you see my 450 with a full on racing level intake..... bahahahaha... I would feel like one of those guys that puts $10k rims on a $1k car or a $20k stereo system in a $500 car. Now if I was into the high performance racing bike thing...I would fully look into this... F1 racing seems to be at the leading edge of all this.

[posplayr]

couldn't you see my 450 with a full on racing level intake..... bahahahaha... I would feel like one of those guys that puts $10k rims on a $1k car or a $20k stereo system in a $500 car. Now if I was into the high performance racing bike thing...I would fully look into this... F1 racing seems to be at the leading edge of all this.

You would be better off putting golf ball dimples on your helmet. Be the first one on your block.

[Blue Falcon]

You would be better off putting golf ball dimples on your helmet. Be the first one on your block.

too late... I'm in Orlando... I have seen every helmet known to man, the cycler's have dimpled helmets. Best one I have seen is a full on custom Boba Fett helmet... fully approved... sweetest helmet I've seen. guy said it was around $1600. It is DOT and SNELL approved. That guy paid more for his helmet than I will have in my bike from purchase to two years of ownership.

edit: the Boba Fett helmet added no significant performance enhancement to the bike/rider.... disclaimer . hehehehehe

dimple motorcycle helmet

[sharpy]

wow. this is more reaction then i ever thought. And no one has mentioned its basically a TRUMPet. Even better. So presuming i was a rich person with a well sorted 1000S superbike. It be ok to go get some plastic 3D stacks made and see if any effect. Trouble is im not rich. dont have a 1000s Superbike but i will have a tougher streeter than my current 1000 one day but even then i wont be running filter less carbs. Ohh and those grooves are semi circle. just cant tell in that pic. I was too lazy to make larger grooves as it would involve breaking into the other surface and have to make some extensions to suit. Thanks heaps everyone
Opps. This is where everyone can call me a wa*ker... just for looks in the pits on a race stand, would the grooved stacks on the RHS be in opposite direction to the 2 stacks on the LHS. Mite make more "bench racing" chat or get me punched on the nose for being a smart-ass.

[posplayr]

we are flying air through a cylinder not an airplane lol... on that note... why not add a honeycomb to the stack? with dimples

You are clearly struggling with a priori synthetic analysis.

[Cipher]

I bet it got him loads of women though.