flow rate surface tension


i have a drip tube with water dripping and when i increase the flow rate or frequency of drips they get bigger/more massive.

i see the equation mass x gravity = 3.14(tube diameter)(surface tension)

my mass is changing but not gravity, 3.14 or tube diameter so surface tension must be related to flow rate but I cant find anything online on how to figure this out.

conversely I have a known flow rate and mass and want to determine tube diameter but unsure how to get it as it appears surface tension must be related to flow rate but I dont know how


  • RobRob UKForum Coordinator
    edited October 23

    Surface tension is a material property so is generally constant for a given temperature.

    The above equation is some sort of force balance which would (usually) be solved to find the mass given the other values are generally known.

    I assume the 3.14 is PI to give the tube circumference?

    I don't think you can use that equation for mass flow as the units don't balance.

  • i have a known flow rate and known mass of the drip and need to determine the diameter of the tube

  • RobRob UKForum Coordinator

    A quick google found a Researchgate paper, droplet rate from tube

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