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Calculating speed of specific Rising Gas

  1. Jul 28, 2014 #1
    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.
  2. jcsd
  3. Jul 28, 2014 #2
    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?
  4. Jul 28, 2014 #3


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    Staff: Mentor

    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?
  5. Jul 28, 2014 #4
    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.
  6. Jul 28, 2014 #5
    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.
  7. Jul 29, 2014 #6


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    Staff: Mentor

    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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