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Discussion Starter · #1 ·
Just curious if anyone worked through the physics of runner taper, been chewin on it allot lately trying to figure out if it can crutch a undersized port
 

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I have some transient CFD simulations somewhere, what are you interested to know?
 

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Discussion Starter · #4 ·
I have some transient CFD simulations somewhere, what are you interested to know?
Have you ever thought of it in terms of hydrualics ? If the opening is 14 sq inch and the exit is 1 sqaure inch, then at 14 psi the rxit should have a significant increase in pressure ove the inlet
 

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Have you ever thought of it in terms of hydrualics ? If the opening is 14 sq inch and the exit is 1 sqaure inch, then at 14 psi the rxit should have a significant increase in pressure ove the inlet
I think you are only looking at the inlet side of the nozzle and forgetting the outlet's role.


Bernoulli Equation. The Bernoulli Equation can be considered to be a statement of the conservation of energy principle appropriate for flowing fluids. The qualitative behavior that is usually labeled with the term "Bernoulli effect" is the lowering of fluid pressure in regions where the flow velocity is increased.


https://www.google.com/imgres?imgur...ved=0ahUKEwiKrLbdicHRAhVr5IMKHSLRBCEQ9QEIIDAA
 

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Discussion Starter · #6 · (Edited)
I think you are only looking at the inlet side of the nozzle and forgetting the outlet's role.


Bernoulli Equation. The Bernoulli Equation can be considered to be a statement of the conservation of energy principle appropriate for flowing fluids. The qualitative behavior that is usually labeled with the term "Bernoulli effect" is the lowering of fluid pressure in regions where the flow velocity is increased.


https://www.google.com/imgres?imgur...ved=0ahUKEwiKrLbdicHRAhVr5IMKHSLRBCEQ9QEIIDAA

No i wasn't, lets try a experment, get a 4 ft pipe and a 4 foot funnel, put a pressure transducer at the bottom of each one, measure the difference. The outlet of a choke point offer in many cases a high delta to the inlet, so if you have high pressure at the inlet and low or no pressure at the outlet, you will get the delta, which should allow more flow in a compressable fluid
 

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Have you ever thought of it in terms of hydrualics ? If the opening is 14 sq inch and the exit is 1 sqaure inch, then at 14 psi the rxit should have a significant increase in pressure ove the inlet
I've talked to a lot of guys about taper and the consensus seems that taper is only effective regarding the reverse flow in the port. I'd certainly like to hear more.
 

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I think you have to look at the taper in the port or better yet the intake manifold like you would the expansion chamber for a 2 stroke, it's all about the wave.
It helps me to forget that there is a "port" and a "manifold" and not look at them separately. I look at the intake tract as one continuous path from the port opening in the plenum, to the valve.
 

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Discussion Starter · #11 ·
I've talked to a lot of guys about taper and the consensus seems that taper is only effective regarding the reverse flow in the port. I'd certainly like to hear more.
I think they are missing something
 

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Dynomation and Eng Mod 4T do a good job of simulating it.
That is the least expensive way to get a solid understanding.
 

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Discussion Starter · #14 ·
Dynomation and Eng Mod 4T do a good job of simulating it.
That is the least expensive way to get a solid understanding.
Do they consider the compressive benefit of taper ?
 

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Do they consider the compressive benefit of taper ?
They compute what happens, dynamic pressure and velocity at the valve. if you imagine something that doesn't happen, it will help you understand what's going on.

Dynomation is easier to use, EngMod 4T is vastly more detailed and customizable but more work to use.
 

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YB Liar and Chief
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No i wasn't, lets try a experment, get a 4 ft pipe and a 4 foot funnel, put a pressure transducer at the bottom of each one, measure the difference. The outlet of a choke point offer in many cases a high delta to the inlet, so if you have high pressure at the inlet and low or no pressure at the outlet, you will get the delta, which should allow more flow in a compressable fluid


Bernoulli's equation. Simple to calculate the pressure at the end of the pipe.
 

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So, do you have a thicker boundary layer at the top of a tapered port (including the manifold runner) or at the bottom where the velocity is higher but the pressure is lower and how does the "wave" effect the boundary layer? Do you want turbulence to "attach" the air flow to the chamber once the air gets past the valve or do you want laminar flow? Just something to think about.
 

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Discussion Starter · #18 ·
So, do you have a thicker boundary layer at the top of a tapered port (including the manifold runner) or at the bottom where the velocity is higher but the pressure is lower and how does the "wave" effect the boundary layer? Do you want turbulence to "attach" the air flow to the chamber once the air gets past the valve or do you want laminar flow? Just something to think about.
Dont know, just curious if the port would act longer or shorter with changes in taper
 

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Take a look at inlet restrictor design, which are designed so they flow the maximum amount of mass through a set MCSA:

The below University of Minnesota paper is very good, in the intro:
The angle of the diffuser
affects engine volumetric efficiency, especially at mid to
high RPM. The diffuser impacts volumetric efficiency
from not only flow and shock losses, but also by
impacting pulse tuning. An increase in volumetric
efficiency between two restrictors, compared at only one
RPM point, could be from reduced flow losses, tuning
effects, or both. While the two effects can never be
totally separated, they must be each examined to gain
an unbiased insight into improving the overall design.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.585.4283&rep=rep1&type=pdf

https://www.academia.edu/4839777/Intake_Manifold_Design_using_Computational_Fluid_Dynamics
http://www.iaeng.org/publication/WCE2013/WCE2013_pp1847-1851.pdf

If there is one take away, it's that the converging and divergent taper is not mutually exclusive. So the duct shape after the MCSA will dictate what happens leading up to it to some degree (pun intended).
 
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