Notes. The range of pressure values correspond to different settings used to seed particles of various sizes and densities in the flow. The range in temperature values corresponds to the cooling that occurs as the gas expands to reach steady low-pressure conditions. The Reynolds numbers are calculated using the definition, Re = ρvL/μ, where ρ is the density of the gas, v the characteristic velocity, L the characteristic length scale, and μ_air = 1.8 × 10^-5 kg m^-1 s^-1 is the dynamic viscosity of air at room temperature. For the particle Reynolds number, we take the characteristic velocity and size to be the terminal velocity and the particle diameters, respectively. The density of the gas is estimated using the measured values of temperature and pressure, assuming a mean molar mass of air M_air = 0.02891 kg mol^-1 and molar gas constant R = 8.314 m³ Pa K^-1 mol^-1. The global Reynolds number comes from the mean flow velocity and the tube diameter. Similarly, the Mach number is the ratio of the mean flow velocity to the sound speed at the measured temperature, again assuming the same values of R and M_air.