Three-dimensional wake division and scale recognition after a multi-scale fractal tree based on Hilbert–Huang transform DOI
Shiyun Liu, Chun‐Ho Liu

Physics of Fluids, Год журнала: 2025, Номер 37(5)

Опубликована: Май 1, 2025

The aerodynamic performance of fractal geometries is a critical concern in engineering, such as urban trees, whose multi-scale wake structures warrant detailed examination. Identifying the contributions from multiple sub-scale tree to dynamics requires decomposition and recognition characteristic scales, which can encounter scale mixing conventional methods fast-fourier transform (FFT) bare empirical mode (EMD). This study analyzes characteristics behind trees with varying crown porosities using Hilbert–Huang (HHT). HHT decomposes by EMD into intrinsic functions (IMFs) first, then determines each IMF's instantaneous frequency amplitude Hilbert spectral analysis. statistical peaked frequency, calculated via marginal spectrum, reveals similar major but different spatial energy distribution compared FFT. joint probability density function (JPDF) denotes consistent high-occurrence peaks at Sth = 0.2, 0.6, 1.2, recommending including 1, 0.33, 0.17 h greening parameterization. reconstructed turbulence field exhibits specific patterns. finding validates bond between JPDF peaks. interaction peak scales investigated look coherence. central oval-like slope offer novel perspective on instability assessment. Additionally, momentum fluxes driven are examined, elucidating pollutant transport, providing valuable guidance for optimizing design.

Язык: Английский

Three-dimensional wake division and scale recognition after a multi-scale fractal tree based on Hilbert–Huang transform DOI
Shiyun Liu, Chun‐Ho Liu

Physics of Fluids, Год журнала: 2025, Номер 37(5)

Опубликована: Май 1, 2025

The aerodynamic performance of fractal geometries is a critical concern in engineering, such as urban trees, whose multi-scale wake structures warrant detailed examination. Identifying the contributions from multiple sub-scale tree to dynamics requires decomposition and recognition characteristic scales, which can encounter scale mixing conventional methods fast-fourier transform (FFT) bare empirical mode (EMD). This study analyzes characteristics behind trees with varying crown porosities using Hilbert–Huang (HHT). HHT decomposes by EMD into intrinsic functions (IMFs) first, then determines each IMF's instantaneous frequency amplitude Hilbert spectral analysis. statistical peaked frequency, calculated via marginal spectrum, reveals similar major but different spatial energy distribution compared FFT. joint probability density function (JPDF) denotes consistent high-occurrence peaks at Sth = 0.2, 0.6, 1.2, recommending including 1, 0.33, 0.17 h greening parameterization. reconstructed turbulence field exhibits specific patterns. finding validates bond between JPDF peaks. interaction peak scales investigated look coherence. central oval-like slope offer novel perspective on instability assessment. Additionally, momentum fluxes driven are examined, elucidating pollutant transport, providing valuable guidance for optimizing design.

Язык: Английский

Процитировано

0