Velocity statistics for rough-wall turbulent boundary layer flow over LEGO roughness elements in different layouts

This dataset presents 2D PIV experimental data collected over a range of twelve urban roughnesses with different frontal and plan solidities. These are described in: [1] Placidi, M., Ganapathisubramani, B. (2015). Effects of frontal and plan solidities on aerodynamic parameters and the roughness sublayer in turbulent boundary layers. Journal of Fluid Mechanics, 782, 541–566. http://doi.org/10.1017/jfm.2015.552 [2] Placidi, M., Ganapathisubramani, B. (2018). Turbulent Flow Over Large Roughness Elements: Effect of Frontal and Plan Solidity on Turbulence Statistics and Structure. Boundary-Layer Meteorology, 167, 99–121. http://doi.org/10.1007/s10546-017-0317-3 PLEASE CITE THESE PAPERS AND THIS DATASET DOI WHEN USING THE DATA. Please contact Dr Marco Placidi ([e-mail]) or Prof Bharathram Ganapathisubramani ([e-mail]) for any queries on the dataset. $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ Format of the dataset: d = Virtual origin [mm] delta = Boundary layer thickness (delta99 [mm]) deltas = Displacement thickness [mm] dyn_visc_air = Air dynamic viscosity [Kg/(m s)] h = Height of the roughness [mm] K = Acceleration parameter as in [1] rho_air = Air density [kq/m^3] run = Case ID as in [1] and [2] theta = Momentum thickness [mm] U = Mean streamwise velocity [m/s] U_edge = Mean streamwise velocity at the edge of the boundary layer [m/s] utau = Skin friction velocity [m/s] based on drag measurements uu = Streamwise velocity fluctuations uv = Reynolds shear stresses V = Mean wall-normal velocity [m/s] vv = Wall-normal velocity fluctuations X = Streamwise coordinate [mm] Y = Wall-normal coordinate [mm] y0 = Roughness length [mm] Additional notes on the dataset: - The 2D PIV dataset has been averaged across the Field of View in the streamwise direction to obtain 1D profiles. - utau is measured directly by means of a floating-element drag balance as described in [1]. - y0,d, are obtained via best fitting the velocity profiles as in [1]. - The entire dataset has been filtered to match the local resolution for all cases, as discussed in [1]. - The acceleration parameter is defined in [1], and it is calculated from 2D PIV data across the size of the drag balance sensing element (i.e. 200 mm x200 mm). As such, it is affected by a significant experimental uncertainty. Additional verification of ZPG conditions were obtained via Pitot tube measurements between the inlet and outlet of the tunnel test section. The pressure gradient was considered negligible.