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

In summary, the assumption is that when two free jets collide at an impingement angle, there is a stagnation point in the impingement zone where stream lines are deflected and a liquid sheet is created. However, recent results suggest that the collision may not be 100% elastic. It is possible for a turbulent impingement zone to have a stagnation point, which may also be a fixed point in the flow. This can occur when the flow is separated into different paths and there is counterflow or an eddy present. This concept is similar to the Brouwer fixed-point theorem.
  • #1
rdemyan
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TL;DR Summary
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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  • #2
Welcome to PF.

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.
 
  • #3
I don't understand your comment regarding a fixed point. I assume you are stating that the fixed point is the stagnation point.
 
  • #4
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
 

1. What is a stagnation point in turbulent flows?

A stagnation point is a point in a fluid flow where the velocity of the fluid is zero. This occurs when the fluid particles come to a complete stop, causing a build-up of pressure at that point.

2. How is a stagnation point different in turbulent flows compared to laminar flows?

In laminar flows, the stagnation point is a single, well-defined point where the fluid particles come to a complete stop. In turbulent flows, however, the stagnation point is not well-defined and can vary in location and intensity due to the chaotic nature of turbulence.

3. Can a stagnation point occur in turbulent flows without the presence of solids?

Yes, a stagnation point can occur in turbulent flows without the presence of solids. It can occur at the interface between two fluids with different velocities or at the boundary of a fluid and a solid surface.

4. How does the presence of a stagnation point affect the behavior of a turbulent flow?

The presence of a stagnation point can cause a significant increase in turbulence and mixing in the surrounding flow. This is because the fluid particles near the stagnation point experience a sudden change in velocity, leading to the formation of vortices and eddies.

5. How do scientists study the existence of stagnation points in turbulent flows?

Scientists use various experimental and computational techniques to study the existence and behavior of stagnation points in turbulent flows. This includes flow visualization techniques, such as dye or particle tracing, as well as mathematical models and simulations to analyze the complex flow patterns near the stagnation point.

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