How particle shape reshapes turbulence

Particles suspended in turbulent flows occur in clouds, oceans, and industrial processes, where they influence mixing, drag, and transport. Yet, how the shape of these particles affects the surrounding turbulence remains poorly understood. From spherical droplets to elongated microplastic fibers, the geometry of suspended solids can alter the way turbulence cascades energy across scales, which is central to predicting and controlling multiphase flows in nature and technology.

Cannon, Olivieri, and Rosti used fully coupled direct numerical simulations with the immersed boundary method to investigate how finite-size spheres and fibers modify turbulence across a broad range of Reynolds numbers. They found that both shapes suppress turbulent kinetic energy, but fibers have a far stronger effect, altering even the smallest dissipative scales. A scale-by-scale energy analysis revealed that particles create a “spectral shortcut,” redirecting energy toward dissipation, a process that penetrates further into the small scales for fibers. The multifractal structure of dissipation shows that spheres intensify sheet-like dissipation, while fibers produce complex, filamentary structures that disrupt vortex stretching. Together, these findings show that particle shape acts as a control parameter for turbulence, linking microscopic geometry to macroscopic flow behavior.