麻豆淫院

Turbulence, the chaotic, irregular motion that causes the bumpiness we sometimes experience on an airplane, has intrigued scientists for centuries. At the Okinawa Institute of Science and Technology (OIST), researchers are exploring this phenomenon in a special class of materials known as complex fluids.

Unlike simple fluids such as water, complex fluids behave in ways that fall between liquids and solids. For instance, when long chain molecules called polymers are added to a fluid, they can dramatically alter its turbulent behavior and shape its flow dynamics. These polymer fluids, which are a type of complex fluids, are all around us, in shampoos, dishwashing liquids, hand sanitizers, and even ketchup.

The fundamental physics that shapes the flow of polymer fluids has remained unclear and a subject of extensive research. Understanding it is crucial for applications such as targeted drug delivery, where flow behavior influences the rate at which drugs are released. But a complex interplay of factors like inertia and elasticity in polymer fluids means that a wide range of turbulent behaviors are possible, making it challenging to untangle the underlying dynamics.

Until recently, scientists believed that two different types of turbulence occurred under separate conditions. Inertial turbulence is the classic form, seen in the chaotic motion of air during airplane turbulence. It occurs when a fluid's inertial forces dominate, producing highly irregular flows.

The other type, known as elastic turbulence, is more unusual. Imagine stirring paint in water. Even when stirred slowly and gently, the fluid can suddenly swirl in unpredictable ways. This happens because the polymers in the fluid stretch and store elastic energy, which destabilizes the flow. In this case, elastic forces take control. Researchers believed that inertial turbulence only appeared in fast, large-scale flows, while elastic turbulence was confined to very slow, gentle flows.

Now, in a new study in 麻豆淫院ical Review Letters, researchers from OIST's Complex Fluids and Flows Unit have shown that these two forms of turbulence, in fact, coexist. Using advanced computer simulations, the team discovered that while large scale fluid motion behaves like inertial turbulence, the same flow shifts to elastic turbulence at the tiniest scales.

"The simulations required for this study were unprecedented," said Dr. Piyush Garg, first author of the study. "Capturing information at this small scale demanded a computing system capable of running extremely high-resolution models efficiently. Achieving this level of detail was essential to uncover the phenomenon, which might explain why it had never been observed before. In fact, this is the largest simulation ever done for these types of fluids."

The findings suggest that elastic turbulence is far more widespread than previously believed. "Until now, we thought that elastic turbulence occurs only in very slow, gentle flows where inertia is almost zero. Our research shows that this is not true. We discovered that elastic turbulence also appears at the small scale alongside inertial turbulence in polymer fluids. In other words, both types of turbulence exist in the same flow, but at different scales," explained Dr. Garg.

"This discovery bridges two branches of turbulence and complex fluids research that were previously thought to be separate. It is the result of OIST's interdisciplinary research environment, where researchers can share insights and tackle open problems from different fields," added Professor Marco Rosti, head of the Complex Fluids and Flows Unit and co-author of the paper.

By discovering that elastic turbulence can emerge within inertial polymer flows, this study could provide a crucial missing link in our understanding of turbulence. It has potential implications for industries relying on polymers to control fluid behavior, such as drag reduction in pipelines, chemical mixing, and biomedical applications.