Stochastic modeling of rough wall turbulent boundary layers: a wind tunnel and atmospheric scale study

The statistical properties of uniform momentum zones (UMZ) in rough wall turbulent boundary layers are investigated at the laboratory and field scales to identify potential similarities in their probability distribution functions in the logarithmic region. In particular, we focus on the thickness H_m and the modal velocity U_m , as a function of the wall distance. These are critical to reproduce the attached eddy scaling laws and the mean velocity profile, while providing a significant contribution to the observed variability of the streamwise velocity component. We will show that building and inverting the H_m, U_m cumulative density functions, allow us to generate synthetic velocity profiles, from the ground up, that mimic the vertical distribution of UMZs while retaining some of the statistical properties of turbulent boundary layers, such as the mean velocity and the variance profiles. Spatio-temporally resolved PIV velocity fields, acquired as part of the Grand-scale Atmospheric Imaging Apparatus (GAIA) collaboration and covering a field of view of 8 x 9 m 2 in the atmospheric surface layer, allow us to derive and test our semi-stochastic algorithm at high Reynolds numbers. Preliminary results show the generalizability of our framework and the potential to develop a computationally affordable, low dimensional, dynamic near wall model.