Knife edge runner openings on single plane manifolds?

[ADR]

The only problem with using and airplane wing as an example is the wing is shaped that way to create lift, the air is supposed to travel over the top of the wing at a higher rate of speed creating a low pressure area ( or something like that) Hey maybe we're onto something
Dale

[todd8541]

Vena Contracta

This is a condition caused by not having a entry radius of a pipe (port in this case) not being large enough to allow complete usage of crossectional area. What happens is the flow field actually looks like a converging and diverging nozzle shape. This in effect produces a actual smaller crossectional shape condition. The flow acts like it is going thru a smaller crossectional area inflicting a flow restriction on itself. The air can't follow a sharp edge like it can a radius. To be able to get maximum usage of available crossectional area the entry must be radiused.

Thats a quick and dirty explaination. It's alittle more technical than that but thats the jist of it.

Todd

[cboggs]

Yea the airplane wing might not have been the best way to explain
what Todd did, .. it's a fluid dynamics thing, the air will follow
the round shape better, .. or, .. what Todd said.

There's a good book on this subject, .. Physical Fluid Dynamics
by D. J Tritton, Oxford Science Publications.

Curtis

[todd8541]

in my fluids book (from school) it has the correct ratio of entry radii to pipe diameter or crossectional area ( I don't have it here with me im working off memory) I will try to look it up tonight and post it here.

Todd

[PRH]

[quote] If a knife edge was a better aerodynamic shape........wouldn't the nose of that plane be pointed like an arrow instead of rounded??? [quote]

i dunno Curtis, those Concord noses are pretty darned pointy

[SchmidtMotorWorks]

I think I remember hearing that pointy shaped planes are used if they go faster the the speed of sound.

[cboggs]

If a knife edge was a better aerodynamic shape........wouldn't the nose of that plane be pointed like an arrow instead of rounded???

i dunno Curtis, those Concord noses are pretty darned pointy

From what I've been told, .. your head is just as pointy, ..
( blaaa, .. good one, .. thank you, thank you, .. I'll be here all week. )

OK, .. the "point" was that the rounded shape of an airplane wing, ..
allows the air to follow the shape and not separate. we all understand
how a wing works, ..
but going down the runway, raining, .. you can watch the rain on the
wing surface, see it follows the shape, .. and once lift is created, see
how it changes, .. just an observation from a guy who spent
too much time on planes.

The round shape allows the air to follow or stay attached to the surface, ..
the knife edge may not, .. ..

Curtis

[OldSStroker]

I think I remember hearing that pointy shaped planes are used if they go faster the the speed of sound.

Or a LOT faster than Mach 1. I believe the angle of the point on the nose or inlet cone of a supersonic aircraft relates to its max Mach.

Fortunately engine inlet flow rarely reaches much over .5 Mach, so round is better than sharp.

[Ken_Parkman]

If the airflow is equal in both runners and there is no angle of attack issues a sharp point is likely better. I'd bet a sharp divider in the head of a multi-valve engine would be better, but i don't have testing to back this up. But in an intake manifold the flow is not simultaneous on adjacent runners and the air is entering from the plenum, so a radiused inlet is necessary to minimize pressure drop.

In the aircraft engines we have very sharp edges in the compressor, and this is critical for maximum efficiency. And the mach numbers are subsonic. But this is a continuous flow system, not from a plenum.

[ADR]

Ahhh...Mr Parkman

Thats kind of what I was thinking, I hope I'm headed in the right direction with this.
The 4V Ford heads I have are already shaped like this....they are not production castings but rather a Ford FR500 performance piece.
Dale