Fluid Dynamics: Fundamentals of Flow

Discussion in 'Irrigation' started by Kiril, Aug 3, 2008.

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  1. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    Here are some of the more important fundamental equations and concepts involved in determining flow of fluids.
    Most links and all images are from Wiki since their reviews are an acceptable place to start.

    No smoke and screens here .... do what you want with the information.

    --------------------------

    1) Conservation of mass with respect to fluid dynamics (derived from Newton's second law of motion)

    Vol = A * V * t (where A = area, V = velocity, t = time)


    2) Bernoulli's principle: states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's gravitational potential energy

    [​IMG]


    3) Navier-Stokes equations: describe the motion of viscous fluid substances such as liquids and gases.
    The following equation is for incompressible flow of Newtonian fluids.

    [​IMG]


    4) Hagen-Poiseuille Equation: describes slow viscous incompressible flow through a constant circular cross-section

    [​IMG]


    5) Darcy-Weisbach Equation: relates the head loss or pressure loss due to friction along a given length of pipe to the average velocity of the fluid flow

    [​IMG] (pressure loss equation)


    6) Reynolds Number: ratio of inertial forces to viscous forces

    [​IMG]

    secondary reference given citation note on Wiki


    7) Colebrook-White equation: used to iteratively solve for the Darcy-Weisbach friction factor f

    [​IMG]


    8) Moody Diagram: relates the Friction factor, Reynolds number and relative roughness for fully developed pipe flow in a circular pipe. It can be used for working out pressure drop or flow rate down such a pipe.

    [​IMG]
     
  2. CAPT Stream Rotar

    CAPT Stream Rotar LawnSite Fanatic
    Posts: 5,892

    ::gets popcorn::

    Kiril-I'm impressed.....
     
  3. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,974

    And yet you can dispense with all that and derive numbers you can design with.
     
  4. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    Another guy who thinks he understands E=MC^2 but needs someone to turn on the light for him.

    I'm still not impressed. You can cut and paste formulas from the net or copy them from a book and that makes you smart. Fix something and I will begin to evaluate intelligence. As a rule, the best guys in the field don't claim to be scholars, but when they speak, the intelligent LISTEN.
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,974

    I may still have some notes supplied by a teacher of practical electronics, a section of which detailed a few essential approximations that would allow one to work without a calculator. That gave a bit more life to the old K&E slide rule.
     
  6. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    At least I have enough common sense not to run SCH40 into a quick coupler with a system pressure of 100 PSI and then push 60GPM through it using a 1" valve.
     
  7. Michael J. Donovan

    Michael J. Donovan Head Moderator, Online Communities Staff Member
    Posts: 3,390

    let's not turn all the threads here in the irrigation forum into a knock down, drag out fight between the two of you. :rolleyes:

    Thanks :waving:
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,974

    Yeah, but Rotar is trying to nail down the Pay-per-view rights. :hammerhead:
     
  9. CAPT Stream Rotar

    CAPT Stream Rotar LawnSite Fanatic
    Posts: 5,892


    Don't forget about T-shirt and hat $$!!1
     
  10. Waterit

    Waterit LawnSite Silver Member
    Posts: 2,888

    Mr. Donovan, please spank these two and send them to their rooms.
     
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