• Transport Phenomena Academy: Fluid Mechanics, Heat & Mass Transfer

  Vorticity Vortex and Eddy in Laminar and Turbulent Flows

  Posted by Aliyar Javadi on October 19, 2024 at 2:21 pm

  Vortex, Vorticity and Eddy in Laminar and Turbulent Flows? What are the differences, similarities, origins and relationships? Why we have vorticity but not vortex in visco-boundary layer of turbulent flows? We had very fruitful discussion on this topic in our recent turbulence course (video from part of the class is attached here, longer video on WAC Transport Phenomena Academy). Our next Turbulence Course will be started next week (Turbulent Flows: Basic Concept, Modeling and CFD Simulation, Run4 2024: https://lnkd.in/ewgQD3uz ).

  Vorticity:

  Vorticity is a defined mathematical vector quantity that describes the local rotation of fluid elements within a flow (curl of the velocity field). Vorticity measures the tendency of fluid parcels to rotate around their local axes. A non-zero vorticity indicates the presence of rotational motion in the flow, which can happen in laminar or turbulent conditions. However in laminar flow can be an initiation towards turbulence, but not necessarily.

  Vortex:

  A Vortex is “A physical region within a fluid flow” where the fluid rotates around an imaginary axis line. It is characterized by swirling motion, typically forming structures such as spirals or whirlpools. Vortex can arise due to various mechanisms, such as the presence of solid boundaries, shear in the flow, or the interaction of different flow streams. Vortexes play crucial roles in lift and drag forces on objects, mixing, and flow stability.

  Regarding the presence of the vorticity and vortex in laminar/turbulent flows:

  -In laminar flow, with defined streamlines, while vortexes may still form in laminar flow, they are typically smaller and less pronounced compared to turbulent flow. Similarly, vorticity exists in laminar flow, but it is often confined to specific regions, such as near solid boundaries or in regions of shear, where rotational motion occurs. The vorticity in laminar flow is generally more uniform and organized.

  In turbulent flow, fluid motion is characterized by chaotic and irregular fluctuations, with high levels of mixing and eddy formation. Vortexes in turbulent flow are larger, more energetic, and more prevalent compared to laminar flow. Turbulent flows exhibit significant vorticity throughout the flow field, with Vortexes continuously forming, interacting, and dissipating. The vorticity in turbulent flow is highly dynamic spatially and temporally.

  Eddies:

  Eddies are commonly associated with turbulent flows, however they can also occur in laminar flows in smaller scales. Eddies and vorticity are closely related, vorticity often being a precursor to the formation of eddies from very small to very large scales.
  We may say, vortex is integration of many temporary vorticities and eddies that appear and dissipate, while vortexes are continuous alive mean flow structure.

  #fluiddynamics #CFD #aerodynamic #mechanicalengineering #Processengineering

  Aliyar Javadi replied 3 months ago 1 Member · 0 Replies
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