New insights into hydrodynamics and potential applications

A team of researchers from King Abdullah University of Science and Technology in Saudi Arabia and Sofia University in Bulgaria has embarked on a collaborative effort to protect marine animals and promote sustainability in marine environments. Their interdisciplinary study focuses on the hydrodynamics of buoyant objects at the interface between air and water.

The researchers aim to enhance our understanding of fluid hydrodynamics and complex interactions occurring on the water’s surface. They believe that this knowledge will advance various fields, including the design and performance of marine engineering systems, buoy systems, and underwater vehicles.

Their recent publication in the journal “Physics of Fluids” explores the dynamics of buoyant spheres resembling skipping stones at the air-water interface. By examining these dynamics, the team unraveled the intricate hydrodynamics involved in creating horizontal air cavities and the transition between floating and skipping. The article is titled “Skipping under water: Buoyant sphere hydrodynamics at the air-water interface.”

The study encompasses several fundamental principles of fluidics and physics related to buoyancy, hydrodynamics, fluid resistance, and the Reynolds number. Buoyancy refers to the upward force experienced by an object immersed in a fluid, while hydrodynamics focuses on the movement of the fluid and its interactions with solid objects.

Fluid resistance, also known as drag, occurs when an object moving through a fluid encounters resistance due to friction between its surface and the fluid. The amount of resistance depends on factors such as the object’s shape, size, speed, and fluid properties.

Scientists utilize a dimensionless parameter called the Reynolds number to analyze fluid behavior and determine the type of flow around an object.

One of the notable findings of the team’s research is that as the pulling force and speed of the spheres increase, their behavior becomes more unpredictable. Co-author Farrukh Kamoliddinov from KAUST explains that the spheres exhibit oscillatory motions, diving into the water, rising towards and breaking the water surface, and creating horizontal air cavities. These phenomena occur as the pulling angle affects the hydrodynamics of the buoyant spheres significantly.

Additionally, the researchers discovered that larger pulling angles lead to varying air-cavity lengths, greater skipping distances, and earlier water exit behavior. The pulling angle, therefore, plays a crucial role in shaping the hydrodynamics of the buoyant spheres.

Moreover, the study unveiled that the air cavity maintains a consistent horizontal motion at a constant velocity over a certain distance. The formation of the air cavity exhibits distinct characteristics, including an inverted wing shape and a turbulent wake trailing behind it. The controlled and steady horizontal motion of the cavity offers valuable insights into complex fluid dynamics, paving the way for further exploration and practical applications.

Co-author Farrukh Kamoliddinov believes that understanding the dynamics of buoyant spheres and cavity formation can inspire new designs and innovations across various fields beyond marine engineering. This knowledge has the potential to contribute to the development of novel propulsion systems, strategies for reducing drag, fluidic propulsion systems, and fluidic devices that leverage the characteristics of buoyant spheres.

Source: American Institute of Physics

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