Effect variable cylinder radius has on airflow

Click For Summary

Discussion Overview

The discussion revolves around the effect of variable cylinder radius on airflow, particularly in the context of fluid dynamics. Participants explore the implications of changing diameters in a hypothetical scenario, examining concepts such as mass flow rate and pressure dynamics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about the impact of the radius ratio on airflow, suggesting that it may not significantly affect the system.
  • Another participant references the principle of mass flow rate conservation and suggests researching venturi tubes as a related concept.
  • A different participant argues that the presence of a section in the pipe does not affect the net flow rate unless work is done, implying that diameter changes alone do not create a difference.
  • One participant highlights that the problem is complex due to factors like air pressure and friction, noting that high velocities could lead to choked flow conditions.

Areas of Agreement / Disagreement

Participants exhibit differing views on the significance of the cylinder radius and the presence of additional sections in the airflow system. There is no consensus on the overall impact of these factors, and the discussion remains unresolved.

Contextual Notes

Participants acknowledge that the problem is hypothetical and may not adhere to established fluid dynamics principles. There are indications of missing assumptions regarding flow conditions and the specific setup of the system.

serveboy
Messages
1
Reaction score
0
Can someone shed some light on the following problem? I'm unable to get any traction on it as I know nothing about fluid dynamics (I'm a computer engineer).

It's a problem I made up over a lunch discussion with a friend. I've illustrated it as folows:

airflow_problem.jpg
 
Engineering news on Phys.org
I don't believe your r2/r1 ratio will have much of an effect.

Try researching venturi tubes, as yours appears to be the inverse of one.

On the most basic of terms.
mass flow rate in = mass flow rate out
and
mass flow rate = density*velocity*cross sectional area
and
volume flow rate = velocity*cross sectional area
 
I don't believe there will be any difference with or without the w1 section either. For there to be any change in the net flow rate, work needs to be done somewhere in the pipe, which itself would just be counted as a restriction of flow no matter if the pipe is changing diameter or not.
 
Since the working fluid is air under pressure, this problem is not as simple as it seems. The velocity of the air from the high pressure side depends, in part, on the friction in the connecting duct. If the velocity is high enough, then the flow into the low pressure reservoir could choke, which means that there is a maximum flow rate which is attained.

Since this is a 'made-up' problem, I don't know what I can tell you do other than consult someone who is knowledgeable in fluid dynamics and gas dynamics.
 

Similar threads

Replies
6
Views
6K
  • · Replies 45 ·
2
Replies
45
Views
7K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 5 ·
Replies
5
Views
22K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 17 ·
Replies
17
Views
6K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
7K