TY - JOUR
T1 - Vertical Coherence of Turbulence in the Atmospheric Surface Layer
T2 - Connecting the Hypotheses of Townsend and Davenport
AU - Krug, Dominik
AU - Baars, Woutijn J.
AU - Hutchins, Nicholas
AU - Marusic, Ivan
PY - 2019/8/15
Y1 - 2019/8/15
N2 - Statistical descriptions of coherent flow motions in the atmospheric boundary layer have many applications in the wind engineering community. For instance, the dynamical characteristics of large-scale motions in wall turbulence play an important role in predicting the dynamical loads on buildings, or the fluctuations in the power distribution across wind farms. Davenport (Quarterly Journal of the Royal Meteorological Society, 1961, Vol. 372, 194-211) performed a seminal study on the subject and proposed a hypothesis that is still widely used to date. Here, we demonstrate how the empirical formulation of Davenport is consistent with the analysis of Baars et al. (Journal of Fluid Mechanics, 2017, Vol. 823, R2) in the spirit of Townsend’s attached-eddy hypothesis in wall turbulence. We further study stratification effects based on two-point measurements of atmospheric boundary-layer flow over the Utah salt flats. No self-similar scaling is observed in stable conditions, putting the application of Davenport’s framework, as well as the attached-eddy hypothesis, in question for this case. Data obtained under unstable conditions exhibit clear self-similar scaling and our analysis reveals a strong sensitivity of the statistical aspect ratio of coherent structures (defined as the ratio of streamwise and wall-normal extent) to the magnitude of the stability parameter.
AB - Statistical descriptions of coherent flow motions in the atmospheric boundary layer have many applications in the wind engineering community. For instance, the dynamical characteristics of large-scale motions in wall turbulence play an important role in predicting the dynamical loads on buildings, or the fluctuations in the power distribution across wind farms. Davenport (Quarterly Journal of the Royal Meteorological Society, 1961, Vol. 372, 194-211) performed a seminal study on the subject and proposed a hypothesis that is still widely used to date. Here, we demonstrate how the empirical formulation of Davenport is consistent with the analysis of Baars et al. (Journal of Fluid Mechanics, 2017, Vol. 823, R2) in the spirit of Townsend’s attached-eddy hypothesis in wall turbulence. We further study stratification effects based on two-point measurements of atmospheric boundary-layer flow over the Utah salt flats. No self-similar scaling is observed in stable conditions, putting the application of Davenport’s framework, as well as the attached-eddy hypothesis, in question for this case. Data obtained under unstable conditions exhibit clear self-similar scaling and our analysis reveals a strong sensitivity of the statistical aspect ratio of coherent structures (defined as the ratio of streamwise and wall-normal extent) to the magnitude of the stability parameter.
KW - Atmospheric stability
KW - Atmospheric surface layer
KW - Eddy structure
KW - Spectral coherence
UR - http://www.scopus.com/inward/record.url?scp=85064437640&partnerID=8YFLogxK
U2 - 10.1007/s10546-019-00445-4
DO - 10.1007/s10546-019-00445-4
M3 - Article
AN - SCOPUS:85064437640
SN - 0006-8314
VL - 172
SP - 199
EP - 214
JO - Boundary-Layer Meteorology
JF - Boundary-Layer Meteorology
IS - 2
ER -