Skip to main content

Flume experiments on intermittency and zero-crossing properties of canopy turbulence

Publication ,  Journal Article
Poggi, D; Katul, G
Published in: Physics of Fluids
January 1, 2009

How the presence of a canopy alters the clustering and the fine scale intermittency exponents and any possible connections between them remains a vexing research problem in canopy turbulence. To begin progress on this problem, detailed flume experiments in which the longitudinal and vertical velocity time series were acquired using laser Doppler anemometry within and above a uniform canopy composed of densely arrayed rods. The time series analysis made use of the telegraphic approximation (TA) and phase-randomization (PR) methods. The TA preserved the so-called zero-crossing properties in the original turbulent velocity time series but eliminated amplitude variations, while the PR generated surrogate data that preserved the spectral scaling laws in the velocity series but randomized the acceleration statistics. Based on these experiments, it was shown that the variations in the dissipation intermittency exponents were well described by the Taylor microscale Reynolds number (Reλ) within and above the canopy. In terms of clustering, quantified here using the variance in zero-crossing density across scales, two scaling regimes emerged. For spatial scales much larger than the canopy height hc, representing the canonical scale of the vortices dominating the flow, no significant clustering was detected. For spatial scales much smaller than hc, significant clustering was discernable and follows an extensive scaling law inside the canopy. Moreover, the canopy signatures on the clustering scaling laws were weak. When repeating these clustering measures on the PR data, the results were indistinguishable from the original series. Hence, clustering exponents derived from variances in zero-crossing density across scales primarily depended on the velocity correlation function and not on the distributional properties of the acceleration. In terms of the connection between dissipation intermittency and clustering exponents, there was no significant relationship. While the former varied significantly with Reλ, the latter showed only minor variations within and above the canopy sublayer. © 2009 American Institute of Physics.

Duke Scholars

Published In

Physics of Fluids

DOI

ISSN

1070-6631

Publication Date

January 1, 2009

Volume

21

Issue

6

Related Subject Headings

  • Fluids & Plasmas
  • 51 Physical sciences
  • 49 Mathematical sciences
  • 40 Engineering
  • 09 Engineering
  • 02 Physical Sciences
  • 01 Mathematical Sciences
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Poggi, D., & Katul, G. (2009). Flume experiments on intermittency and zero-crossing properties of canopy turbulence. Physics of Fluids, 21(6). https://doi.org/10.1063/1.3140032
Poggi, D., and G. Katul. “Flume experiments on intermittency and zero-crossing properties of canopy turbulence.” Physics of Fluids 21, no. 6 (January 1, 2009). https://doi.org/10.1063/1.3140032.
Poggi D, Katul G. Flume experiments on intermittency and zero-crossing properties of canopy turbulence. Physics of Fluids. 2009 Jan 1;21(6).
Poggi, D., and G. Katul. “Flume experiments on intermittency and zero-crossing properties of canopy turbulence.” Physics of Fluids, vol. 21, no. 6, Jan. 2009. Scopus, doi:10.1063/1.3140032.
Poggi D, Katul G. Flume experiments on intermittency and zero-crossing properties of canopy turbulence. Physics of Fluids. 2009 Jan 1;21(6).

Published In

Physics of Fluids

DOI

ISSN

1070-6631

Publication Date

January 1, 2009

Volume

21

Issue

6

Related Subject Headings

  • Fluids & Plasmas
  • 51 Physical sciences
  • 49 Mathematical sciences
  • 40 Engineering
  • 09 Engineering
  • 02 Physical Sciences
  • 01 Mathematical Sciences