Simple Tunnel ram Question

[Tuner]

Well now, finally a breath of fresh air, somebody gets it. Thank you. Someone else with the mathematical inclination to do so, calculate the the percentage of acceleration gravity supplies to the overall acceleration of the air mass. In racing where 1 % can be significant, 2 % is nothing to ignore. 150/2.4 = 62.5 1/62.5 = 0.016, so 1.6 %.

I ran a test far more sensitive than 1%, it showed nothing.

How did you accomplish accelerating, and decelerating, and accelerating again, repetitively, the air mass in pulses, like the intake dynamics in a running engine?

[Tuner]

This effect will more than cancel any gravitational effect. https://www.youtube.com/watch?v=y2iBbwocYZw

If you can cancel gravity you are not only the Most Interesting Man In The World .... you will soon be the Richest And Most Interesting Man In The World.

[SchmidtMotorWorks]

Well now, finally a breath of fresh air, somebody gets it. Thank you. Someone else with the mathematical inclination to do so, calculate the the percentage of acceleration gravity supplies to the overall acceleration of the air mass. In racing where 1 % can be significant, 2 % is nothing to ignore. 150/2.4 = 62.5 1/62.5 = 0.016, so 1.6 %.

I ran a test far more sensitive than 1%, it showed nothing.

How did you accomplish accelerating, and decelerating, and accelerating again, repetitively, the air mass in pulses, like the intake dynamics in a running engine?

The question at hand is whether gravity assists acceleration of air flowing into a duct.

For air to flow into a duct it must accelerate.
The velocity of air flowing in a duct is not uniform even when it has a constant cross section until at least one diameter into the duct.
So the question does not require testing intermittent flow or reversing flow to be answered.
If it will be more convincing to you in can do the test with a tapered duct so that there is certainly acceleration all the length of the duct.

I asked you what length you want me to test on a single cylinder dyno engine. Did you answer?
I can run this on an engine that has hundreds of pills on it to measure very small changes, a 1% A, B, A, B change would be easy to see since it could be done in less than a minute.

[pcnsd]

I ran a test far more sensitive than 1%, it showed nothing.

How did you accomplish accelerating, and decelerating, and accelerating again, repetitively, the air mass in pulses, like the intake dynamics in a running engine?

The question at hand is whether gravity assists acceleration of air flowing into a duct.

For air to flow into a duct it must accelerate.
The velocity of air flowing in a duct is not uniform even when it has a constant cross section until at least one diameter into the duct.
So the question does not require testing intermittent flow or reversing flow to be answered.
If it will be more convincing to you in can do the test with a tapered duct so that there is certainly acceleration all the length of the duct.

I asked you what length you want me to test on a single cylinder dyno engine. Did you answer?
I can run this on an engine that has hundreds of pills on it to measure very small changes, a 1% A, B, A, B change would be easy to see since it could be done in less than a minute.

I have seen this word "Pill" used here many times and I have to admit I have not been able to divine its meaning in application. I suspect it refers to a sensor of some type. Could you please define it for me?

Thanks.

[SchmidtMotorWorks]

Sorry, mobile phone auto correct changed pull to pill.

[SchmidtMotorWorks]

challenge question

Is gravity an attractive or repelling force?

In other words, how do you know that there is not a force that pushes all objects from all sides but the mass of an object blocks that force. So any 2 masses would appear to be attracted but in reality they are being pushed together.

How could you conduct a test to answer that question?

[GARY C]

challenge question

Is gravity an attractive or repelling force?

In other words, how do you know that there is not a force that pushes all objects from all sides but the mass of an object blocks that force. So any 2 masses would appear to be attracted but in reality they are being pushed together.

How could you conduct a test to answer that question?

How do you know it's not pulling?

[GRTfast]

challenge question

Is gravity an attractive or repelling force?

In other words, how do you know that there is not a force that pushes all objects from all sides but the mass of an object blocks that force. So any 2 masses would appear to be attracted but in reality they are being pushed together.

How could you conduct a test to answer that question?

This question is irrelevant to the discussion. If mass interrupts this hypothetical pushing force such that objects have a net force towards each other, we call that effect gravity, that effect is indistinguishable from an attraction between the two objects. Kudos for outside the box thinking though.

[GARY C]

challenge question

Is gravity an attractive or repelling force?

In other words, how do you know that there is not a force that pushes all objects from all sides but the mass of an object blocks that force. So any 2 masses would appear to be attracted but in reality they are being pushed together.

How could you conduct a test to answer that question?

This question is irrelevant to the discussion. If mass interrupts this hypothetical pushing force such that objects have a net force towards each other, we call that effect gravity, that effect is indistinguishable from an attraction between the two objects. Kudos for outside the box thinking though.

What happens i it don't?

[SchmidtMotorWorks]

challenge question

Is gravity an attractive or repelling force?

In other words, how do you know that there is not a force that pushes all objects from all sides but the mass of an object blocks that force. So any 2 masses would appear to be attracted but in reality they are being pushed together.

How could you conduct a test to answer that question?

This question is irrelevant to the discussion. If mass interrupts this hypothetical pushing force such that objects have a net force towards each other, we call that effect gravity, that effect is indistinguishable from an attraction between the two objects. Kudos for outside the box thinking though.

I am past the question about gravity making a difference unless someone can post a diagrammed argument that shows how it does.

So I have moved on to something that is actually debatable.

[SchmidtMotorWorks]

challenge question

Is gravity an attractive or repelling force?

In other words, how do you know that there is not a force that pushes all objects from all sides but the mass of an object blocks that force. So any 2 masses would appear to be attracted but in reality they are being pushed together.

How could you conduct a test to answer that question?

How do you know it's not pulling?

We don't know either way, that is the point of the question.

The challenge is to imagine a way that you could test, to find out which way it is.

[SchmidtMotorWorks]

The point in mentioning an upside down engine was to illustrate the need to accelerate the weight of air from zero to port velocity. 650 HP requires approx. 1000 CFM. 1000 cubic feet of standard air weighs approximately 75 lbs. and will be accelerated from zero to approximately 300 fps. The acceleration force of gravity is always there and to compare updraft to down draft was to illustrate the intake air's weight is either being lifted or falling. Accelerating the air from zero to port velocity is a portion of an engine's pumping loss. In a tunnel ram with vertical down-draft runners, gravity assists the acceleration of the air.

In the image below will more air flow into duct A or B or will they be the same? (The top opening is facing up)

tunnel_ram.jpg

[BenE64]

Maybe the question should be which duct will reach peak flow the fastest?

[digger]

It is a bit more complicated than this. https://en.wikipedia.org/wiki/Buoyancy

Tuner was pointing to a reduced or depressed local atmosphere which would display a lower pressure gradient. He is then considering a parcel or ensemble of particles/molecules that at a given point in time have a higher average density than that of the local atmosphere they are moving into. The acceleration due to gravity would then exceed the buoyancy force.

The counter is that the parcel is mixing with the local atmosphere and interacting with the molecules.

The counter is then that the mixing is not simultaneous across the boundaries of the parcel.

Another counter is that the parcel is not a valid construct...

And so it goes. Meanwhile, engineers like to have workable or pragmatic solutions to problems.

~~~~~~~~~~~~~~~~~~~~

Simplifications of the physics are so ingrained now in everyday life that they are ignored. Sometimes what is considered normal physics is deadly as when mine shafts contain stratified layers of deadly gases or inversions in lakes release large and also deadly quantities of carbon dioxide. http://www.slate.com/blogs/atlas_obscur ... f_co2.html

Yes, I know, more B.S. Saved you some trouble...

"drop" a dense pocket of air into "vacuum" hypothetically s, after 1 foot accelerating at 1g it is travelling at most 2.4m/s. this is compared to being accelerated to 150-180m/s due to pressure ratio. so its a small effect even in this unrealsitic case. In reality is there is a gradient within the runner so you are not going to have a small pocket of highly dense air in a low dense air field. so the effect is going to be even more neglibile in the overall scheme.

Well now, finally a breath of fresh air, somebody gets it. Thank you. Someone else with the mathematical inclination to do so, calculate the the percentage of acceleration gravity supplies to the overall acceleration of the air mass. In racing where 1 % can be significant, 2 % is nothing to ignore. 150/2.4 = 62.5 1/62.5 = 0.016, so 1.6 %.

that was a hypothetical analogy that isnt close to reality though

another way of looking at gravity is the "potential energy" term = rho x g x h from bernoulli or sometimes called hydraulic head

for something a foot high is = 1.2 x 9.8 x 0.3 = 3.5 Pa (0.0035 kPa)

the kinetic energy term 0.5 x rho x v^2 from bernoulli

for something that accelerates from essentially stationary to mach 0.5 (170 m/s) = 0.5 x 1.2 x 170^2 = 17,340 Pa (17.34 kPa)

so the potnetial energy is negligible

[SchmidtMotorWorks]

Maybe the question should be which duct will reach peak flow the fastest?

If they end up at the same flow, that would be because the force was equal.
If the force is equal, the acceleration is equal.

I guess what people that imagine that gravity is a factor in this are thinking that gravity does force force the air into the duct facing up,,,
but forget that the atmospheric pressure at the opening of the lower duct is greater (by the same distance and the same force of gravity)