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Thread: vortex size

  1. #11
    Jumbo
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    Dick

    I mentioned it, but maybe not too clearly:

    'I would look at having some solids removal on each bottom drain independently.'

    Mark

  2. #12
    Sansai Andrew's Avatar
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    Simon,

    If you don't want water rotation with-in the chamber, as with answer units, then fit a 90 degree internal elbow, direct the water vertically, and I'd suggest upwards away from where gravity has the S, H one T, setteling out.

  3. #13
    Oyagoi bekko's Avatar
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    I made the mistake of building (from scratch) a 5 foot diameter x 3 foot deep vortex for 3600 gph. It was an expensive and pain-staking project which was a complete waste of time. Nothing could settle out in that whirlpool and all the leaves ended up in the little pump trap which had to be emptied daily. I threw 100 square feet of 1/2 inch woven predator netting into the vortex to slow the flow and trap debris, but the debris does not fall to the bottom of the cone bottom so it is a pain to clean. Should have made it 8 foot diameter.


    steve hopkins

  4. #14
    Sansai Vogata's Avatar
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    OK her just my to pence and small brain

    I see some comment on stopping the whirlpool effect. As far as I know this effect is just a mean to keep retention contact time in settlement high.

    At the normal “low” speed we have in normal pond construction should not give anything like industrial vortex separation. Industrial separation is easily to design but to my knowledge comes out for non-commercial standards “VERY” expensive in power consumption pr passing unit.



    Have always figured that the settlement in vortex was due to the old speed principle. It will badly translated read something like this:

    Speed at vortex wall 0.0-speed at centre off whirl given by pump and diameter off vortex – speeds at in and outlet (centre top off unit) given by pump and pipe diameter.



    All particles with higher density than water will fall if given an opportunity. The speed will drop accordingly to diameter and goes for the speed off wall the nearer you get. In the “film” closes to the wall it’s in principle equal too zero. This film will let particles fall to the lowest part off the unit.



    Objects placed in this scenario only gives me thoughts off turbulence and no real peace off mind or settlements. I have always placed this kind off fine practical settlement outside (read after) the “vortex” unit.





    Please feel very free to comment, harass or enlighten me.





    PS Dear BB

    Not always as you comment. The countermove is adjustable restrictions (with option to close on purge) on each feed. Measuring and adjusting too the flow pattern needed. Purging each line separately as it was a single line.

    The pro is level off awareness and control and the possibility to automate the system. Con as always cost and need off commitment.
    Tone - Truls -Petter
    Vogata NI

  5. #15
    Oyagoi bekko's Avatar
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    Here is my GUESS at how particles seem to move towards the center of a gyre in defiance of centrifugal force. My vision is that there is some random motion as particles are moved along by the circular motion. When this random motion moves them towards the center, the particles become "trapped" by the velocity gradient (zero at center to maximum at perimeter). The trapping is related to a relative reduction in the random motion at a lower velocity.

    I also wonder if there is another factor at work. As a particle is pushed along by the circular water current, could the difference in the pressure exerted on the side of the particle facing towards the perimeter where the velocity if higher be greater than the force applied to the side of the particle facing towards the center of the gyre where the velocity if lower? If so, then there would be a net force pushing the particle towards the center.

    I have never been able to find any information on this subject and do not know if I am correect in this thinking. Vogata, you seem to have an engineering background. Have you ever seen an explaination of how solids are moved towards and are concentrated at the center of a gyre? Is there a name for this?

    Thanks,
    steve hopkins

  6. #16
    Sansai Bancherd's Avatar
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    Talking

    Just to take my mind off the earthquake in Niigata.


    This is what I think is happening to particles of different sizes and masses in the vortex tank:
    a) When we have strong whirling motion and in equilibrium, all particles should have approximately same total energy(kinetic plus potential energy).
    Potential energy = m*g*h where m is mass of particle, g is constant~9.8m/sec**2 and h is height above some reference point(tank's bottom)
    Kinetic energy is mainly rotational kinetic energy =(mv**2)/2 where v is directly proportional to radial distance from center of rotation and angular velocity

    Therefore particles with larger mass will tend to be in the center and lighter massed particles will be towards the outside.

    b) In normal "vortex" tanks, the settlement occurs when kinetic energy(hence velocity) is low enough such that most of the energy is potential energy; particles falls towards the bottom where potential energy is lower(things will moves towards lower energy states). This could occur near boundary of the tank due to much reduced rotational velocity caused by friction/obstruction by the wall against the flow of the water. Rough wall surfaces could enhance the effectiveness of the settlement. I believe someone(Peter Menear?) did an experiment where he put ridge surfaces or baffles along wall of the vortex, resulting in much improved settlement action.

    Whew......I had not had to use my brain this way for a longggg time. It hurts.



    Please excuse my poor grammar.

  7. #17
    Daihonmei
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    Whew,
    Hard to believe people can think as wrong as they do........
    I won't go into every silly statement above but.........an object with a greater density will have more energy and therefore will be more prone to travel in a staight line and will therefore in a liquid will push all other matter out of its way in an attempt to move in a straight line and will thereby work itself to the OUTSIDE of the body of liquid.
    I will Not argue with people who have opposing opinions as this is not about a person's faulty opinion or their daydreaming.
    It is not about particle size..it is about density.....particles more dense than water will sink, and particles more dense than water will work towards the outside of the spinning water.
    When they reach the boundary layer their fall will be much more pronounced due to the fact that water movement has the attribute of causing particles that are slightly more dense than water to remain in solution(float within the water) just as the errant newspaper in a strong breeze...and remnants of homes in a hurricane.
    Elementary Physics.

  8. #18
    Sansai Bancherd's Avatar
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    Hi luke:


    Particles whose density is less than water(ice, styrofoam blocks, etc.) will NOT settle, regardless of whether or not we have vortex or water movement. So I hope we are on the same page and discuss the particles whose density is greater than that of the fluid(water in this case).

    I sent you a PM, think about what I said.

    You can try a little experiment, put some sands of different sizes/masses(approximately equal density but denser than water) in a big bucket of water, swirl the heck out of it until EVERYTHING is being suspended by water. You will notice that the surface of the water is lowest at center and highest near the bucket's surface. Then let the water settle and you can see a distribution of particles of different masses(with ~equal density).

    I am willing to learn something new on how things work, so please educate me. It would not be the first time that I had misconception of physics, and I am sure that this would not be my last.

    Oh luke, before moving to Puyallup, WA. I used to work for Harris and lived in Melbourne/Palm Bay, just across the river from you.

  9. #19
    Oyagoi bekko's Avatar
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    OK, put some stuff (s.g.>1) in the bucket, swirl it to suspend everything, wait a few seconds, and look - all the stuff is spinning around at the center of the bucket. Wait for the water movement to stop and look - all the stuff is deposited on the bottom at the center of the bucket. Following the Bancherd or luke logic, all the stuff would be deposited at the perimeter of the bucket. You have not described the forces that pull material to the center.steve

  10. #20
    Sansai Bancherd's Avatar
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    Thank you Steve! They settle at the center of the bucket, NOT on the outside, especially the larger massed ones.

    What you saw was the stuff that easily settle out, no problems there. The larger massed particles should settle closer to the center which is be explained by the total energy consideration.

    I think the tougher stuff to settle out is the lower massed particles, which is easily suspended and might be kept in suspension by the movement of the water. Now, if we could slow down these particles enough, given time, they will settle out before they exit the chamber. Please note that most things have less energy when slowed down(all elses are equal).

    How do we slow these things down? One way is to create an area near surfaces where fluid's velocity is slowed down by drags. Which is perfect, since these difficult particles to settle out are already on the outer edge of the vortex(by energy consideration).

    I hope I am not too far off on the tangent here(puns intended).

    Steve, are you in Hawaii? I went to high school in Kaneohe, HI.

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