Spinning jets in a crosswind: how swirl changes mixing, recirculation, and cooling

What is it about?

This paper uses high-fidelity computer simulations to examine what happens when many small jets of warm air are blown upward into a crosswind, and those jets are given a “spin” (swirl). The model mirrors real situations such as the warm air discharged by arrays of cooling fans. The study shows that moderate swirl pushes more air sideways, creating stronger reverse flow near the surface and keeping warm air closer to the ground. Very strong swirl quickly breaks down the jet core so the jet does not rise far, again trapping heat near the surface. The work also tracks how turbulence evolves downstream, revealing when the flow moves from a non-equilibrium state to a more balanced, predictable state.

Featured Image

Photo by Sona Balayan on Unsplash

Photo by Sona Balayan on Unsplash

Why is it important?

Arrays of swirling jets appear in industrial cooling and emissions systems, where unwanted hot-air recirculation can cut performance and reliability. This study is one of the first to resolve, in detail, how adding swirl to multiple jets changes jet height, mixing and the build-up of heat near equipment. The results explain when swirl worsens recirculation and when it mainly alters turbulence without big gains in vertical transport. These insights can guide the design and operation of fan arrays—such as choosing swirl levels or layouts that limit heat being drawn back into intakes—and provide data for improving turbulence models used by engineers.