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K N T U CIVIL ENGINEERIG FACULTY

`. K N T U CIVIL ENGINEERIG FACULTY. FLOW IN PIPES. With special thanks to Mr.VAKILZADE. Velocity profile:. open channel. pipe. Friction force of wall on fluid. For pipes of constant diameter and incompressible flow.

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K N T U CIVIL ENGINEERIG FACULTY

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  1. ` KNTUCIVILENGINEERIGFACULTY FLOW IN PIPES With special thanks to Mr.VAKILZADE

  2. Velocity profile: open channel pipe Friction force of wall on fluid

  3. For pipes of constant diameter and incompressible flow Vavg stays the same down the pipe, even if the velocity profile changes Vavg Vavg Conservation of Mass same same same

  4. For pipes with variable diameter, m is still the same (due to conservation of mass), but V1 ≠ V2 D1 D2 m V1 V2 m 2 1

  5. Laminar and Turbulent Flows

  6. Definition of Reynolds number: Re < 2300  laminar 2300 ≤ Re ≤ 4000  transitional Re > 4000  turbulent

  7. Hydraulic diameter: Dh = 4Ac/ P • Ac = cross-section area • P = wetted perimeter

  8. Consider a round pipe of diameter D. The flow can be laminar or turbulent. In either case, the profile develops downstream over several diameters called the entry lengthLh. Lh/D is a function of Re.

  9. Instantaneousprofiles Comparison of: laminar and turbulent flow

  10. Laminar Turbulent slope slope w w w,turb > w,lam w = shear stress at the wall, acting on the fluid

  11. w Take CV inside the pipe wall P1 P2 V L 2 1 Conservation of Mass

  12. Conservation of x-momentum Terms cancel since 1 = 2 and V1 = V2

  13. or Energy equation (in head form): cancel (horizontal pipe) V1 = V2, and 1 = 2 (shape not changing) hL = irreversible head loss & it is felt as a pressuredrop in the pipe

  14. w = func( V, , D, )  = average oughness of the inside wall of the pipe

  15. But for laminar flow, roughness does not affect the flow unless it is huge Laminar flow: f = 64/Re Turbulent flow: f = Moody Chart

  16. i pipe sections j components Minor Losses: KL is the loss coefficient.

  17. Energy Line (EL) and Hydraulic Grade Line (HGL) (Source: Larock, Jeppson and Watters, 2000: Hydraulics of Pipeline Systems)

  18. Pipe Networks : • Pipes in series • Pipes in parallel

  19. 1 A 2 B 3

  20. Any question?

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