Airflow vortices study could improve airport runway efficiency

When an aircraft takes off, it leaves behind trailing vortices in the air that can affect other aircraft takeoff and landing. As a result, airports require separation distances between aircraft that affect runway capacity and efficiency.

To better understand vortex prediction models and improve separation distance, Nguyen et al. conducted high-resolution direct numerical simulations of a counter-rotating vortex pair interacting with a flat wall. The simulations captured how the vortices deformed, stretched, twisted, and eventually broke down. By analyzing the flow with physical metrics, the researchers determined the underlying topological mechanisms responsible for the rapid decay of the vortices.

“We identified new 3D topologies, including scaly-shaped vortices and a figure-eight-shaped vortex structure that undergoes a unique severing process before detaching from the main system,” said author Van Luc Nguyen. “To our knowledge, this provides one of the most detailed topological descriptions of vortex-wall interactions to date.”

The authors hope the work can contribute to improved physical understandings of how aircraft vortices behave near the ground, which could eventually help optimize aircraft separation distances during takeoff and landing. The findings about turbulence with strong wall interactions is also applicable to other engineering and environmental flow problems.

“Bridging this knowledge gap between physical triggers and vortex transition is vital both for advancing the fundamental physics of complex vortex dynamics and for supporting next-generation wake-vortex prediction and safety management strategies in aviation,” Nguyen said.

Next, the authors plan to study higher Reynolds numbers that more closely reflect real conditions and investigate the interplay between short-wave instabilities and long-wave Crow instability.

Source: “Direct numerical simulation of instability in counter-rotating vortex pair–wall interaction,” by Van Luc Nguyen, The Hoang Nguyen, Dinh Thang Nguyen, and Van Quang Anh Vo, Physics of Fluids (2026). The article can be accessed at https://doi.org/10.1063/5.0331042 .