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

  Von Kármán Vortex Street

  Posted by Aliyar Javadi on May 8, 2024 at 10:31 am

  Laminar or Turbulent Structure? What do you think about Von Kármán Vortex Street? Mostly we think that rotating flows with vorticities, eddies and vortex structures are always turbulent. However not every rotation and vorticities, and not all eddies means turbulent flow conditions.

  Von Kármán Vortex Street is one of these examples, which can be appeared as laminar vortex street or as the form of turbulent wakes. It typically refers to the pattern of alternating swirling vortices that forms in the wake of an object placed in a fluid flow.

  We had a short discussion on this interesting flow pattern, which can be a challenging mixed laminar-turbulent structure during first lecture of our course on turbulent flows ( https://lnkd.in/ewgQD3uz ) . This phenomenon can occur for various flow conditions, laminar or turbulent, depends on several factors, including the Reynolds number and interestingly for small scale mm to very large scale km scales atmospheric flow (attached movie).

  At low Reynolds numbers, The Von Kármán street may be predominantly laminar, characterized by smooth and orderly fluid motion with well-defined vortices. In this regime, the flow around the object is generally stable, and the vortex shedding pattern is relatively regular.
  However, as the Reynolds number increases, the flow in the von Kármán street can transform to a turbulent regime. In turbulent flow, the fluid motion becomes chaotic and irregular, with fluctuations and mixing occurring at various scales.

  In practical scenarios, the flow in the von Kármán street often exhibits characteristics of both laminar and turbulent flow, especially during the transition between the two regimes.

  The transition from laminar to turbulent flow in the von Kármán street can lead to changes in the vortex shedding pattern, increased drag on the object, and enhanced mixing in the wake.

  Therefore, whether the von Kármán street is laminar or turbulent depends on the specific flow conditions, including the Reynolds number, fluid properties, and geometry of the object. In many cases, the von Kármán street may exhibit features of both laminar and turbulent flow, making it a fascinating and complex phenomenon in fluid dynamics.

  To better understand such important mechanisms in fluid mechanics, deep understanding of the key concepts such as vorticity, Eddy and Vortex and their similarities, difference and relationships are important. We try to cover such comprehensive discussions about the physics of fluid towards reliable modeling and simulations during our running Live Courses on Transport Phenomena ( https://lnkd.in/ea59rdP8 ) Turbulence ( https://lnkd.in/ewgQD3uz ) and CFD Simulation Courses ( https://lnkd.in/etie_TBw ) on World-Academies.Com (Knowledge-Management Startup at Technical University of Dresden, Germany)

  Aliyar Javadi replied 5 months ago 1 Member · 0 Replies
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