A Tree Swaying in a Turbulent Wind: A Scaling Analysis

TL;DR

This paper develops a scaling theory for how trees sway in turbulent wind, linking turbulence characteristics to branch morphology and dynamics, suggesting branches respond passively to airflow.

Contribution

It introduces a novel scaling analysis connecting turbulent wind properties to tree branch response and morphology, emphasizing passive branch dynamics.

Findings

The turbulence within the tree crown is in the inertial regime.

The penetration depth of wind correlates with branch morphology.

Branch dynamics are primarily passive, influenced by turbulence.

Abstract

A tentative scaling theory is presented of a tree swaying in a turbulent wind. It is argued that the turbulence of the air within the crown is in the inertial regime. An eddy causes a dynamic bending response of the branches according to a time criterion. The resulting expression for the penetration depth of the wind yields an exponent which appears to be consistent with that pertaining to the morphology of the tree branches. An energy criterion shows that the dynamics of the branches is basically passive. The possibility of hydrodynamic screening by the leaves is discussed.