Results 1 to 3 of 3
Like Tree1Likes
  • 1 Post By Harold14370

Thread: Trajectory of a jet of water

  1. #1 Trajectory of a jet of water 
    New Member
    Join Date
    Jun 2012

    As the title suggests, my question concerns the trajectory of a jet of water, for example arising from water flowing out of a vessel with a hole in it. The standard approach to this phenomenon would be to treat the jet of water as undergoing free fall, and approximating its trajectory by a quadratic curve.

    However, I have some doubts about the validity of this model, specificially, the assumption that the water of the jet undergoes free fall. There are obviously internal forces in the jet of water, so when concidering a small segment of said jet, there is, in my opinion, not only the force of gravity to consider, and therefore we are not dealing with free fall.

    Any attempts at shedding some light on this issue are most welcome.

    Reply With Quote  


  3. #2  
    Join Date
    Apr 2007
    I think a free fall would be a very good approximation, neglecting air resistance. What internal forces do you think would exist? As the water exits the hole, it is depressurized. If the stream of water is a constant velocity, the water droplets are all leaving at the same speed and undergo the same acceleration. There wouldn't be any tendency for a droplet to catch up to the droplet ahead of it. It's a liquid, so there wouldn't be any shear forces, or hardly any. The droplets would tend to form into bigger drops due to surface tension. I don't think it would signficantly alter the trajectory. As the droplets fall they will pick up speed and the stream will get thinner because the same volumetric flow rate is spread out over a larger distance. This will tend to separate the stream into smaller drops.

    Last edited by Harold14370; June 5th, 2012 at 03:47 PM.
    msafwan likes this.
    Reply With Quote  

  4. #3  
    New Member
    Join Date
    Jun 2012
    I think you are right. At first I mas making the analogy between the jet of water and a sequence of balls connected with springs, making the point that as the speed of the jet was increasing the separation between the water molecules would increase and thus give rise to an internal force. However, as you pointed out, the water jet merely gets thinner and the separation of the water molecules remains constant, so there is no such effect as I first suggested.

    Reply With Quote  

Similar Threads

  1. Period of the DE trajectory
    By srm in forum Computer Science
    Replies: 0
    Last Post: February 10th, 2012, 09:41 AM
  2. Replies: 3
    Last Post: January 26th, 2012, 02:09 PM
  3. Help my ignorance on trajectory
    By takenaptly in forum Physics
    Replies: 1
    Last Post: March 14th, 2010, 03:50 PM
  4. vector and trajectory calculation
    By the man of science in forum Physics
    Replies: 23
    Last Post: January 10th, 2009, 05:22 PM
  5. Replies: 9
    Last Post: September 20th, 2008, 05:06 AM
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts