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Physics of turbulence

Physics of turbulence. muna Al_khaswneh Dr.Ahmad Al-salaymeh. Introduction. Turbulence cannot exist by itself, however; it requires a continuous supply of energy& changes in velocity& direction. Objective. The Definition of turbulence Examples of turbulence Boundary layer

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Physics of turbulence

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  1. Physics of turbulence muna Al_khaswneh Dr.Ahmad Al-salaymeh

  2. Introduction Turbulence cannot exist by itself, however; it requires a continuous supply of energy& changes in velocity& direction .

  3. Objective • The Definition of turbulence • Examples of turbulence • Boundary layer • Study Reynolds numbers • Study the differential continuity equation • Study Navier-Stocks equation • Kolmogorov theory • Laminar-turbulent transition Problems of turbulence

  4. Definition & properties It is a flow with disordered in time & space . 1-three-dimensionality. 2-Unsteadiness. 3-strong vorticity. 4-Unpredictability. 5-Broad spectrum.

  5. Reynolds number 1. inertia forces 2. viscous forces 1. ρ u2 ,ρ: fluid density ,u : fluid speed 2. μ u , μ: viscous fluid , d : diameter fluid d

  6. Re = inertia forces viscous forces = ρ d uμ

  7. So that Reynolds number depend on fluid properties as ; speed , pipe diameter ,viscosity & density .

  8. Random pipe Re

  9. Boundary layer

  10. Laminar-turbulent transition . • Linear stability theory . • Primary instability of free shear flow . • Later stage of transition in free shear flows .

  11. Continuity equation The conservation of mass principle is applied to the control volume

  12. Continuity equation For three dimension (our interest ) z Δz y Δy Δx x = uxî + uyў +uzќ

  13. Continuity equation or

  14. Navier-stokes equation the momentum translate with tow ways & tow forces ways • Convection transition • Molecular transition forces 1.Gravity force 2.Pressure force

  15. Forces 1.Gravity force Pressure force

  16. Convection transition

  17. Molecular transition Shear stress

  18. Molecular transition

  19. For x direction

  20. Navier-stokes equation

  21. Newtonian equation

  22. stocks equation

  23. Kolmogorov theory • The physics of turbulence is the same in all turbulent system . • It is independent of large scale forcing & small scale dissipative • Fluctuation occur in an incompressible medium-density 4.Energy flows from large scales to small scales .

  24. laminar flow (average speed) turbulent pressure (drop)

  25. Primary instability of free shear flow

  26. Primary instability of free shear flow

  27. Later stage of transition in free shear flows . Some vorticity remains between the vortices , we will call it {secondary instability} .

  28. Problems

  29. The endThank you

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