Notes. The Reynolds numbers for both the container and particle diameters correspond to laminar gas conditions. The values of the volumetric filling factor, ϕ, andspatially averaged solid-gas ratio, ϵ, depend directly on the mean particle number, n, and/or the value of V_meas, given in the text. The momentum diffusion time, t_d, is less than the friction time, T_f, in all cases, and both are in units of s. The particle diameter d_{p, St−Ep} is obtained using Eq. (3), where the prescript Ep or St indicates whether the particles belong to either the Epstein or Stokes drag regime. The particle diameter d_p derives from Eq. (5), and is the value assumed for the calculation of Re, ϕ, ϵ, T_f, and t_d. The variance on the mean settling velocity for all experiments in a data set is and is used to estimate the range in mean particle size d_p. The last column reports the number of trajectories in a given data set, which is the total sample size for the mean quantities displayed in the data analysis.