Kirigami-inspired wind steering for natural ventilation

TL;DR

This study explores how kirigami-inspired angled structures can enhance natural urban ventilation by directing wind flows, using simulations and experiments to optimize design for improved air exchange and adaptability.

Contribution

It introduces a novel kirigami-based approach for wind steering in urban ventilation, demonstrating its effectiveness through simulations and experimental validation.

Findings

Louver geometry significantly improves air exchange rates.

Non-homogeneous louver orientations enhance multi-directional ventilation.

Kirigami structures can replace traditional louvers for adaptive airflow control.

Abstract

Ensuring adequate ventilation of exterior and interior urban spaces is essential for the safety and comfort of inhabitants. Here, we examine how angled features can steer wind into areas with stagnant air, promoting natural ventilation. Using Large Eddy Simulations (LES) and wind tunnel experiments with particle image velocimetry (PIV) measurements, we first examine how louvers, located at the top of a box enclosed on four sides, can improve ventilation in the presence of incoming wind. By varying louver scale, geometry, and angle, we identify a geometric regime wherein louvers capture free-stream air to create sweeping interior flow structures, increasing the Air Exchange Rate (ACH) significantly above that for an equivalent box with an open top. We then show that non-homogeneous louver orientations enhance ventilation, accommodating winds from opposing directions, and address the generalization to taller structures. Finally, we demonstrate the feasibility of replacing louvers with lattice-cut kirigami ("cut paper"), which forms angled chutes when stretched in one direction, and could provide a mechanically preferable solution for adaptive ventilation. Our findings for this idealized system may inform the design of retrofits for urban structures -- e.g. canopies above street canyons, and "streeteries" or parklets -- capable of promoting ventilation, while simultaneously providing shade.