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We measure the deceleration of liquid nitrogen drops floating at the surface of a liquid bath. On water, the friction force is found to be about 10 to 100 times larger than on a solid substrate, which is shown to arise from wave resistance. We investigate the influence of the bath viscosity and show that the dissipation decreases as the viscosity is increased, owing to wave damping. The measured resistance is well predicted by a model imposing a vertical force (i.e., the drop weight) on a finite area, as long as the wake can be considered stationary.
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http://dx.doi.org/10.1073/pnas.1106662108 | DOI Listing |
Phys Rev Lett
February 2025
Service de Physique de l'Etat Condensé, Université Paris-Saclay, CNRS, CEA, 91191 Gif-sur-Yvette, France.
The scale-invariant inverse energy cascade is a hallmark of 2D turbulence, with its theoretical energy spectrum observed in both direct numerical simulations (DNS) and laboratory experiments. Under this scale-invariance assumption, the effective diffusivity of a 2D turbulent flow is dimensionally controlled by the energy flux and the friction coefficient only. Surprisingly, however, we show that such scaling predictions are invalidated by numerical solutions of the 2D Navier-Stokes equation forced at intermediate wave number and damped by weak linear or quadratic drag.
View Article and Find Full Text PDFSci Rep
February 2025
Polytechnic University of Bari, DICATECh, Via E. Orabona 4, 70125, Bari, Italy.
This paper investigates the complex interaction between wave hydrodynamics and aquatic vegetation, emphasizing its importance for the management of coastal ecosystems. Vegetation plays a crucial role in the dynamics of river and coastal flows, influencing their structure and turbulence, as well as the transport and distribution of nutrients, sediments, ecosystems, and habitats. For example, mangroves serve as a natural defense against tsunamis and extreme waves.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
February 2025
Department of Environmental, Land and Infrastructure Engineering, Politecnico di Torino, Torino 10129, Italy.
The wave attenuation properties of seagrasses are key to accurately predict how effective these plants are at protecting coasts from erosion and floods. While recent studies have significantly advanced the understanding of seagrass wave attenuation in pure-wave conditions, the presence of a current introduces several complications that have yet to be fully explored. In the present study, we quantify the wave attenuation of seagrass canopies in the presence of a current parallel to the direction of wave propagation via experiments conducted with dynamically scaled mimics of seagrass installed in a laboratory flume facility.
View Article and Find Full Text PDFBioinspir Biomim
February 2025
Department of Mathematics and Statistics, 2000 Pennington Road, The College of New Jersey, Ewing Township, NJ 08628, United States of America.
Tomopterids are mesmerizing holopelagic swimmers. They use two modes of locomotion simultaneously: drag-based metachronal paddling and bodily undulation.has two rows of flexible, leg-like parapodia positioned on opposite sides of its body.
View Article and Find Full Text PDFPlants (Basel)
January 2025
State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China.
Based on field observation at the north coast of the Zhanjiang Bay in southern China, the characteristics of wave attenuation due to the drag force of one mangrove species, (Forsk.) Viern., were quantitatively analyzed.
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