Göttingen-type two-phase wind tunnel with closed test section. The test section is shown in more details in Fig. 2
Optically accessible test section with passive grid and bluff body, showing coordinate system and measurement planes (left) and the applied two-fluid atomizing nozzle with six orifices (right).
Droplet size distribution (DSD) and corresponding log-normal distribution function at x = 0, y = − 5, z = 90, measured by PDA.
Illustration of configurations M1–M4, respectively.
Convergence of the arithmetic mean and volume mean diameters measured by PDA as a function of the number of samples at a chosen measurement point. The volume mean diameter converges for around 8000 samples.
Mean droplet diameter profile across the measurement section at x; = 0, z; = 0, measured by means of PDA.
Mean axial velocity profile of the droplets across the measurement section at x = 0, z = 0, measured by means of LDV.
(Color) Mean axial velocity distribution of the air phase at x = 0, measured by means of LDV.
(Color) Mean turbulence intensity distribution of the air phase in x-direction at x = 0, measured by means of LDV.
(Color) Mean axial velocity of the droplets at x = 0, measured by means of PDA, for configuration M1, M2, M3, and M4, respectively (from top to bottom).
(Color) Droplet number density per unit volume in droplet cm−3 at x = 0 calculated from the PDA results as described by Roisman and Tropea.55
Change in mean and volume mean diameter (averaged over the cross section) of the droplets along the x-axis for configuration M3, measured by means of PDA and showing the increase in mean droplet size.
Example of a collision event at x = 0, z = 140 of configuration M3, measured by means of Shadowgraphy.
Comparison of calculated (theoretical) and measured (experimental) collision rate for a z-profile at x = 0, y = 150 mm for Configuration M4.
Typical values observed within cumulus clouds compared to that found in the wind tunnel.
Measured averaged flow and turbulence parameters for all configurations in the wind tunnel at the entrance of the test section (x = 0).
Quantities measured by PDA and needed for a theoretical estimation of collision probabilities, compared to the collision probability measured by Shadowgraphy for x = 0 at different z -values for Configuration M3.
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