Scaling Laws in Canopy Flows: A Wind-Tunnel Analysis
2013 (English)In: Boundary-layer Meteorology, ISSN 0006-8314, E-ISSN 1573-1472, Vol. 148, no 2, 269-283 p.Article in journal (Refereed) Published
An analysis of velocity statistics and spectra measured above a wind-tunnel forest model is reported. Several measurement stations downstream of the forest edge have been investigated and it is observed that, while the mean velocity profile adjusts quickly to the new canopy boundary condition, the turbulence lags behind and shows a continuous penetration towards the free stream along the canopy model. The statistical profiles illustrate this growth and do not collapse when plotted as a function of the vertical coordinate. However, when the statistics are plotted as function of the local mean velocity (normalized with a characteristic velocity scale), they do collapse, independently of the streamwise position and freestream velocity. A new scaling for the spectra of all three velocity components is proposed based on the velocity variance and integral time scale. This normalization improves the collapse of the spectra compared to existing scalings adopted in atmospheric measurements, and allows the determination of a universal function that provides the velocity spectrum. Furthermore, a comparison of the proposed scaling laws for two different canopy densities is shown, demonstrating that the vertical velocity variance is the most sensible statistical quantity to the characteristics of the canopy roughness.
Place, publisher, year, edition, pages
Springer Netherlands, 2013. Vol. 148, no 2, 269-283 p.
Canopy flows, Turbulence statistics, Velocity spectrum
Meteorology and Atmospheric Sciences
IdentifiersURN: urn:nbn:se:kth:diva-125545DOI: 10.1007/s10546-013-9813-2ISI: 000321949300002ScopusID: 2-s2.0-84880510703OAI: oai:DiVA.org:kth-125545DiVA: diva2:640276
FunderSwedish Energy AgencyStandUp
QC 201506252013-08-132013-08-092015-06-25Bibliographically approved