Is there a stagnation point in turbulent flows not involving solids?

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Discussion Overview

The discussion revolves around the existence of stagnation points in turbulent flows, specifically in the context of colliding free jets of liquids without solid objects. Participants explore the implications of turbulence on the formation of stagnation points in the impingement zone of these jets.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant suggests that in the impingement zone of colliding free jets, a stagnation point may exist around which streamlines are deflected, despite the turbulence created by energy release during the collision.
  • Another participant argues that if a steady flow is separated by a collision into different paths, a stagnation point must exist, although it may be dynamically moving due to turbulence.
  • A third participant seeks clarification on the concept of a fixed point, interpreting it as synonymous with a stagnation point, while another clarifies that a stagnation point is indeed a fixed point where fluid velocity is zero.
  • It is proposed that there may be other fixed points in turbulent flow, and if the flow divides at one of those points, it could also be considered a stagnation point.

Areas of Agreement / Disagreement

Participants express differing views on the nature and existence of stagnation points in turbulent flows, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

The discussion includes assumptions about the behavior of fluids in turbulent conditions and the definitions of stagnation and fixed points, which may not be universally agreed upon.

rdemyan
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TL;DR
Is there a stagnation point in turbulent flows not involving solids?

Reference: https://www.physicsforums.com/forums/classical-physics.61/post-thread
When two free jets collide at some impingement angle (not necessarily a head on collision), the usual assumption is that in the impingement zone there is a stagnation point around which stream lines are deflected. From this stagnation point, a thin liquid sheet is created, which eventually breaks down into droplets at some distance downstream. Originally, all analyses assumed that there was no loss of energy in the impingement zone. However, more recent results seem to suggest that the collision is not 100% elastic. My question is: if there is in fact turbulence created in the impingement zone of colliding free jets (as a result of an energy release), can there be a stagnation point? Is a stagnation point possible in a turbulent impingement zone especially when only two liquids are involved and there is no solid object.
 
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If a steady flow is separated, by any collision, into one or more different paths, there must be a stagnation point. That stagnation point may be moving dynamically as a result of the turbulence.

Where there is counterflow, or an eddy, there must also be a fixed point.
 
I don't understand your comment regarding a fixed point. I assume you are stating that the fixed point is the stagnation point.
 
rdemyan said:
I assume you are stating that the fixed point is the stagnation point.
I am saying the inverse, that the stagnation point is a fixed point. The fluid there has zero velocity.

There may be other fixed points in a turbulent flow. If the flow divides into two paths at one of those points, then it is also a stagnation point.
https://en.wikipedia.org/wiki/Brouwer_fixed-point_theorem
 

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