Shark skin has a unique design that reduces drag and boosts speed

Have you ever wondered why a shark is such a prolific swimmer, effortlessly cruising through the sea at variable speeds? The secret ingredient lies in their skin.

Sharks, especially the notorious great white shark, are revered predators of the oceans. These magnificent creatures are known for their relentless hunting skills, reaching impressive speeds of up to 6.7 meters per second.

They are also known for their marathon-like swimming capabilities, covering distances of up to 20,000 kilometers.

How is this possible? The secret is in their tiny tooth-like structures known as dermal denticles present on their skin which are believed to reduce frictional drag while they swim.

These denticles not only give sharks their signature rough skin but have also sparked curiosity among engineers designing riblets or small unidirectional ridges for aircraft and sailboats.

Studying shark denticles

While the purpose of denticles might seem straightforward, understanding their function is far from simple.

The variation in the shape, size, and spacing of denticles across a shark’s body adds layers of complexity to understanding how they work together to reduce drag. Researchers from the Tokyo Institute of Technology set out to untangle this complexity.

To investigate, the scientists developed 3D models of white shark denticles, observing their hydrodynamic size of the high middle ridges and the low side ridges.

The team’s findings were nothing short of remarkable. The study provided evidence of how these well-designed denticles function at various swim speeds, facilitating sharks to reach top speeds during hunting and maintaining steady cruising speeds during long-distance journeys.

“Our calculations suggest that the combination of high and low ridges of the denticles results from adapting to both slow and high swimming speeds, thereby offering robustness to various swimming conditions,” noted study co-author Professor Hiroto Tanaka.

Understanding shark denticles

Getting closer to understanding the mystery of shark skin, the researchers used microfocus X-ray CT scanner to obtain skin samples from 17 different locations on a white shark.

The samples were then used to create detailed 3D models enabling the scientists to measure the spacing and height of the ridges.

Previous studies suggest that these ridges might play a critical role in countering frictional drag by lifting turbulent vortices away from the shark’s skin surface.

The scientists hypothesized that the dimensions and spacing of the ridges are vital in determining how effectively the shark interacts with these vortices at different swimming speeds.

Simulating various swimming conditions, the research team calculated non-dimensional values that could provide insights into how the ridge spacing of shark denticles influences drag reduction across different speeds.

The results confirmed their hypothesis, demonstrating how ridges contribute to drag reduction.

“We found that high ridges likely reduce drag at low swimming speeds, and high-low alternating ridges reduce drag at high swimming speeds, thereby covering the full range of swimming speeds,” explained Professor Tanaka.

Implications for engineering and evolution

The insights from this study not only shed light on the remarkable adaptability of shark denticles but could inspire more efficient designs in engineering, particularly for aircraft and sailboats.

Furthermore, the research introduces new methods of analyzing the biological evolution of sharks, including extinct species like the giant megalodon.

Surprisingly, data derived from fossils suggests that the swimming speeds of the megalodon might not have differed much from those of the great white shark.

This discovery allows us to appreciate the time-tested brilliance of nature’s design and could potentially help shape our understanding of efficient movement, not just underwater but in the air as well.

Harnessing shark skin innovations

As researchers continue to uncover the secrets behind shark skin and denticles, the potential applications extend beyond marine biology.

The unique properties of shark skin could lead to innovations in biomimicry, inspiring new materials that minimize friction in various industries.

For instance, sports gear designers might explore shark skin-inspired textures to enhance athletic performance, while the automotive sector could integrate these principles to improve fuel efficiency by reducing drag.

Moreover, advancements in 3D printing technology could enable the production of synthetic surfaces that mimic the shark’s dermal denticles, providing a sustainable solution for industries looking to optimize performance and reduce energy consumption.

As we delve deeper into the marvels of nature, the lessons learned from sharks might not only enhance our understanding of aquatic life but also revolutionize how we design and engineer products across multiple fields.

The study is published in the journal Journal of The Royal Society Interface.

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