Enlarge / Great white sharks can reduce drag at different swimming speeds thanks to high and low ridged denticles in its skin. (credit: Terry Goss/CC BY 2.5)

The great white shark (Carcharodon carcharias) is a swift and mighty hunter, capable of reaching speeds as high as 6.7 m/s when breaching, although it prefers to swim at slower speeds for migration and while waiting for prey. A team of Japanese researchers has studied the structure of the great white's skin to learn more about how these creatures adapt so well to a wide range of speeds. Their findings could lead to more efficient aircraft and boats with greatly reduced drag, according to a recent paper published in the Journal of the Royal Society Interface.

As previously reported, anyone who has touched a shark knows the skin feels smooth if you stroke from nose to tail. Reverse the direction, however, and it feels like sandpaper. That's because of tiny translucent scales, roughly 0.2 millimeters in size, called "denticles" (because they strongly resemble teeth) all over the shark's body, especially concentrated in the animal's flanks and fins. It's like a suit of armor for sharks, and it also serves as a means of reducing drag in the water while swimming.

Pressure drag is the result of flow separation around an object, like an aircraft or the body of a mako shark as it moves through water; the magnitude of pressure drag is determined by the shape of the object. It's what happens when the fluid flow separates from the surface of an object, forming eddies and vortices that impede the object's movement. Since the shark's body is constantly undulating as it swims, it needs something to help keep the flow attached around that body to reduce that drag. Denticles serve that purpose.

Enlarge (credit: jules/CC BY 2.0)

Inertial confinement fusion is one method for generating energy through nuclear fusion, albeit one plagued by all manner of scientific challenges (although progress is being made). Researchers at Lehigh University are attempting to overcome one specific bugbear with this approach by conducting experiments with mayonnaise placed in a rotating figure-eight contraption. They described their most recent findings in a new paper published in the journal Physical Review E with an eye toward increasing energy yields from fusion.

The work builds on prior research in the Lehigh laboratory of mechanical engineer Arindam Banerjee, who focuses on investigating the dynamics of fluids and other materials in response to extremely high acceleration and centrifugal force. In this case, his team was exploring what's known as the "instability threshold" of elastic/plastic materials. Scientists have debated whether this comes about because of initial conditions, or whether it's the result of "more local catastrophic processes," according to Banerjee. The question is relevant to a variety of fields, including geophysics, astrophysics, explosive welding, and yes, inertial confinement fusion.

How exactly does inertial confinement fusion work? As Chris Lee explained for Ars back in 2016: