What is Turbulence: Definition and 88 Discussions

In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between those layers.Turbulence is commonly observed in everyday phenomena such as surf, fast flowing rivers, billowing storm clouds, or smoke from a chimney, and most fluid flows occurring in nature or created in engineering applications are turbulent. Turbulence is caused by excessive kinetic energy in parts of a fluid flow, which overcomes the damping effect of the fluid's viscosity. For this reason turbulence is commonly realized in low viscosity fluids. In general terms, in turbulent flow, unsteady vortices appear of many sizes which interact with each other, consequently drag due to friction effects increases. This increases the energy needed to pump fluid through a pipe.
The onset of turbulence can be predicted by the dimensionless Reynolds number, the ratio of kinetic energy to viscous damping in a fluid flow. However, turbulence has long resisted detailed physical analysis, and the interactions within turbulence create a very complex phenomenon. Richard Feynman has described turbulence as the most important unsolved problem in classical physics.

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  1. N

    Airflow Turbulence at carburettor flange

    Hi Guys/Girls, Please may I seek your collective minds for help? I have an issue with poor mixture distribution from a carburettor that uses a spray bar and throttle slide (known as a Throttle Body Injector TBI) The holes in the spray bar are at the side of the spray bar in full rich, the...
  2. D

    Measuring Flow Velocity in Pipe Expansion: Laminar vs. Turbulent | Explained

    Hi there, I have a double-barreled question for you all. So I have two pipes connected to each other. The first pipe is 0.64cm and has a Re = 5000, the second pipe is 4.5cm and has a Re = 700. The two are connected so that the gas expands from the the first pipe to the second. Now, I wish to...
  3. J

    Turbulence in pipe flow (Reynold's Number)

    I have some confusion about how blockages result in the laminar/turbulent flow of fluids in pipes. From my understanding, there is a certain diameter of a blockage in a pipe that will cause the flow to transition from laminar to turbulent (depending on the velocity of flow, etc.) What is the...
  4. M

    Turbulence and Structure Functions

    Hey PF! I was wondering if any of you were familiar with structure functions and how they relate to turbulence? Do you know of any good articles to research? Structure functions may be defined as $$S_{ij}(\vec{R}) = \mathbb{E} \Big[ \big( u_i(\vec{x}+\vec{R}) - u_i(\vec{x}) \big) \big(...
  5. Abel Cavaşi

    Mass of Turbulence: Does Turbulent Fluid Have More Energy?

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  6. P

    [Aerodynamics] Why does the drag coefficient increase after turbulence

    As you can see, around Reynolds number of 5 105 the transition occurs for a smooth sphere. However, why is it that after this transition that the drag coefficient increases at turbulence?
  7. C

    About Turbulence and Navier-Stokes

    I was discussing this with my friend the other night. I mentioned that proving existence of smooth solutions for the Navier-Stokes equations would win a $1,000,000 prize from the Clay Mathematics Institute, and also that turbulence is considered one of the unsolved problems of physics; as a...
  8. G

    Topology-bornology as a basis of turbulence

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  9. G

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  10. N

    K41 Kolmogorov scaling relation and structure functions (turbulence)

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  11. R

    Questions about turbulence spectra

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  12. K

    Turbulence and Steering Control

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  13. B

    Why Does Air Break Up into Swirls Behind a Blunt Body in Fast Motion?

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  14. A

    Exploring the Limits of Turbulence in Fluid Dynamics

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  15. M

    Phase-space structures in plasma turbulence

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  16. Loren Booda

    Turbulence - just a phenomenon of cavitation?

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  17. F

    Recent publications on plasma turbulence.

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  18. J

    Why is turbulence the most important unsolved problem of classical physics?

    I've heard it said that 'we don't really understand turbulence', and that it is one of the biggest outstanding problems in classical physics right now. (Or at least Feynman thought so back in his day) But what is there to understand about turbulence and why don't we understand it? I thought...
  19. J

    Relationship between turbulence and freezing?

    How fast do i need to pump water in a 10" aluminum pipe to prevent freezing? Assume 32*F inlet temp and 0*F ambient . For my conditions, the temps will vary and T ambient easily gets down to -20*F or more.
  20. D

    Questions about engineering and turbulence

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  21. C

    Evening out turbulence in a 3 pipe

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  22. K

    Why is turbulence so little understood?

    As ole' Feynman said: "Turbulence is the most important unsolved problem of classical physics." So why is it so, that this everyday phenomena is so little understood by scientists?
  23. R

    Turbulence Kinetic Energy in pipe flow

    What is the equation to estimate the turbulence kinetic energy per unit volume in pipe flow? Any information is appreciated. Thanks.
  24. N

    Could nanomachines reduced turbulence?

    Right now I think one of the key problems with confining fusion in a tokamak is that turbulence is generated within the plasma. I was wondering if it were hypothetically possible a hypothethical nanomachine to control the random bombard of atoms that create turbulence and thus cease turbulence...
  25. Loren Booda

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  26. T

    Explanation of Wavenumber wrt Turbulence and Energy dissipation

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  27. A

    When is turbulence beneficial?

    Hi guys. I know turbulence is a b($#H when trying to explain and often poses problems in flyid dynamics. However, our university lecturuer has thrown this at us to think about as it's a pretty interesting topic and I thought there might be some people out there that have ideas about it...
  28. B

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  29. E

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  30. H

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  31. Helios

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  32. A

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  33. Astronuc

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  34. A

    Understanding the Relationship between Turbulence, Drag, and the Reynolds Number

    Just to the point How to calculate Re number? in example for calculating Re number at diffrent points in a boat. How turbulence affect drag? I know simply turbulence will increase the drag but, to what extent; or simply, the formula connecting both. Comparing the drag between turbulence...
  35. Clausius2

    Turbulence and Lorenz Attractor

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  36. Clausius2

    Turbulence & Physics: Unsteady & Random Behaviour?

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  37. Clausius2

    Is the Adherence Condition Still Valid in Turbulent Flow?

    Hey I came into a doubt in the classical physics forums, and I want to know if I said something stupid. Usually we employ in Fluid Mechanics the adherence condition (u=0 just on the wall, where fluid and solid meets; u=velocity field). But I'm not sure if in turbulent regimenes this keeps on...
  38. A

    Exploring Turbulence in Thermal Baths

    Hi all, the other day I was in a thermal bath where they had some whirlpool jets at the bottom of a basin about breast-deep. I was standing right over the jets, and the turbulence in the water was so strong at the surface, that I couldn't stand straight but was forced to sway back and forth and...
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