Calculating speed of specific Rising Gas

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Discussion Overview

The discussion revolves around calculating the speed at which hydrogen gas rises in air after being generated through electrolysis. Participants explore the factors influencing this speed, including the dimensions of the cylinder, air temperature, and the potential use of heavier gases to enhance buoyancy. The inquiry includes whether gases reach terminal velocity and seeks relevant equations or models for this scenario.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant seeks to calculate the rising speed of hydrogen gas from an initial velocity of 0 in room air, questioning if gases reach terminal velocity.
  • Another participant inquires about existing equations for calculating the speed of a rising gas, expressing difficulty in finding relevant materials.
  • A participant clarifies that their interest lies in the behavior of hydrogen in air, not in water, and emphasizes the need for variables such as cylinder diameter and air temperature in the calculations.
  • There is mention of the possibility of substituting atmospheric air with a heavier gas to increase the buoyancy of hydrogen, raising questions about the implications of such a substitution.
  • One participant suggests that simulating gas flow may be necessary, as there are no simple formulas for general cases of gas mixing, and asks about the boundary conditions and simulation software available.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the specific equations or models to use for calculating the speed of rising hydrogen gas, and multiple viewpoints regarding the factors influencing this speed remain present.

Contextual Notes

The discussion highlights limitations in available resources for calculating gas behavior, including the need for specific boundary conditions and the complexity of gas mixing scenarios.

KyleKidd
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Hello everyone. I am a college graduate perusing independent research of my own. I'm trying to figure out how to calculate how fast a specific gas (hydrogen) will rise from an initial velocity of 0 in room air and temperature.

Basically, I'm trying to figure out how fast hydrogen would be traveling as it rose in a cylinder after electrolysis per given distance (do gasses reach terminal velocity?).

Also, it would be helpful to be able to calculate the speed in a heavier gas if my experiment called for using a more inert gas.
 
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Is there an equation for calculating the speed of a rising gas? Despite my best effort, I cannot find any material on it. Perhaps I am using invalid search parameters. Any help?
 
KyleKidd said:
Hello everyone. I am a college graduate perusing independent research of my own. I'm trying to figure out how to calculate how fast a specific gas (hydrogen) will rise from an initial velocity of 0 in room air and temperature.

Basically, I'm trying to figure out how fast hydrogen would be traveling as it rose in a cylinder after electrolysis per given distance (do gasses reach terminal velocity?).

Also, it would be helpful to be able to calculate the speed in a heavier gas if my experiment called for using a more inert gas.

KyleKidd said:
Is there an equation for calculating the speed of a rising gas? Despite my best effort, I cannot find any material on it. Perhaps I am using invalid search parameters. Any help?

Welcome to the PF.

Since you mention electrolysis, should we assume that you are asking how fast the hydrogen and oxygen bubbles rise through the water at the bottom of the tubes?
 
Thank you for the warm welcome.

Your assumption would be incorrect. I am interested in how fast hydrogen would rise in air. The only reason I mentioned electrolysis was for context.

Basically, I want to know how fast I could expect hydrogen to rise straight upwards if confined to a cylinder of room air.

The diameter of the cylinder, height of measurement, and air temperature would all be great variables to include in the equation I'm looking for.
 
Also, I may be interested in substituting normal atmospheric air with a heavier elemental gas. Possibly to increase buoyancy of the hydrogen as it rose, or to substitute air with a less reactive gas.
 
KyleKidd said:
Thank you for the warm welcome.

Your assumption would be incorrect. I am interested in how fast hydrogen would rise in air. The only reason I mentioned electrolysis was for context.

Basically, I want to know how fast I could expect hydrogen to rise straight upwards if confined to a cylinder of room air.

The diameter of the cylinder, height of measurement, and air temperature would all be great variables to include in the equation I'm looking for.

KyleKidd said:
Also, I may be interested in substituting normal atmospheric air with a heavier elemental gas. Possibly to increase buoyancy of the hydrogen as it rose, or to substitute air with a less reactive gas.

Bubbles in a liquid would probably be easier, but in the general case, maybe not.

Can you say more about what you want to simulate? There aren't any simple "formulas" for general cases of mixing gasses. You would usually use simulation software to try to approximate those flow rates.

What are the boundary conditions? What laminar flow / FEA simulation software do you have access to?
 

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