2026/03/30 by Matteo Puccioni, Giacomo Valerio Iungo, Michele Guala +3 · 1 voice
Engineering · Environmental Science · #Combustion and flame dynamics #Fluid Dynamics and Turbulent Flows #Wind and Air Flow Studies
paper · pdf · doi:10.1017/jfm.2026.11370
openalex publication_date 2026/03/30 · openalex created_date 2026/03/31 · openalex updated_date 2026/07/28
The forward leaning inclination angle, γ , of coherent turbulent structures is a well-known feature of wall-bounded turbulent flows. Although invariant across friction Reynolds numbers within the range Reτ =103-106 , γ can vary significantly across turbulent scales within a high-Reynolds-number flow. Very-large-scale motions (VLSMs) are known to induce significant changes in the instantaneous shear profile, which is a conditioning event that could trigger variability in the inclination angle of smaller coherent turbulent structures. Although this aspect has been extensively studied via numerical and laboratory experiments, few studies have explored this feature for a very-high-Reynolds-number atmospheric flow. In this work, the inclination angle of turbulent structures within the atmospheric surface layer at a very high Reynolds number ( Reτ =7.9× 105 ) is investigated by deploying a scanning Doppler light detection and ranging and a super large particle image velocimetry (SLPIV) apparatus. The inclination angle of wall-attached eddies is inferred either from the two-point correlation of streamwise velocity ( γ =41.1^∘ ) or with a scale-dependent approach through the spectral linear stochastic estimator (SLSE). The SLSE (and, thus, the scale-dependent inclination angle) is conditionally evaluated based on the high- and low-momentum events induced by VLSMs, both in the streamwise ( u'VLSM ) and in the vertical ( w'VLSM ) velocity components. As a result, lower inclination angles ( γ =30^∘ -50^∘ ) are found for u'VLSM\gt 0 ( w'VLSM\lt 0 ), while higher values ( 50^∘ -85^∘ ) are ascribed to u'VLSM\lt 0 ( w'VLSM\gt 0 ). This result emphasises the primary role that VLSMs play in shaping the wall-attached eddy geometry, which, in turn, is crucial to determine the Reynolds stress balance within the wall-attached eddy range.