The tendency to get out of chaos is hidden in the most basic equations of fluid mechanics

Science

While order is often brought into chaos, sometimes the opposite. For example, turbulent fluids tend to spontaneously form a regular pattern: parallel lines.

Although physicists can explain this phenomenon experimentally, they now observe why this is done using the basic equations of fluid dynamics, taking one step closer to understanding why particles behave in this way.

When there is liquid in the laboratory between two parallel plates that move in opposite directions, the flow becomes turbulent. But after a while, turbulence begins to fade in a striped manner. The result is a screen of fine lines and turbulence running at an angle to the flow (imagine light wind waves in the river).

“You get a clear structure and order chaotic movements of turbulence,” said senior author Tobias Schnyder, assistant professor at the Swiss Federal Institute of Technology technical school in Lausanne. This “strange and very vague” behavior has long fascinated scholars. “

Physicist Richard Feynman estimates that the explanation must be hidden in the fundamental equation of fluid dynamics, the Navie-Stokes equation.

But this equation is very difficult to solve and analyze, Schneider said about Live Science. (Seeing that Navier-Stokes even has subtle solutions in 3D fluids everywhere is one problem, at a price of one thousand million dollars worth $ 1 million.) So, until now nobody knows how that equation predicts this behavior modeling. Schnyder and his team have a combination of methods, including computer simulations and theoretical calculations, to find a series of “very specific solutions” to this equation that mathematically describe each step of the transition from chaos to order.

In other words, they have broken chaotic behavior into non-haute building blocks and found solutions for every small part. “The behavior that we observe is not mysterious physics,” Schinder said. – This is rather hidden in a standard equation that describes fluid flow.

This model is important to understand because it shows how turbulent and silent, otherwise known as “laminar flow” competes with each other to determine final status, according to the explanation. When this model appears, turbulent and laminar flow is just as strong – without the country that wins the war.

However, this pattern is not observed in natural systems such as turbulence in the air. Schneider noted that such a model would be “very bad” for the plane because it had to fly through an uneven and turbulent outline.

The main objective of this experiment is to understand the basic physics of fluids in a controlled environment, he said. Only by understanding the very simple fluid movements, can we begin to understand the more complex turbulence systems that are around us, starting from the air flow around the aircraft to the interior of the pipe, he added.

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