Case Studies in the Human Respiratory System - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 286

Table 8.10 Measured
parameters from a spray
device

Measured Parameters Value

Nozzle diameter ≈ 0.5 mm

≈

Diameter at break-up length 4mm

≈

30 ◦ Spray cone angle

Initial particle velocity ≈ 15 m/s

Break-up length ≈ 3.5 mm

break-up length and d n is the nozzle diameter. However this linear approximation
doesn't take into account any momentum losses during the entire spray penetration
and may give an over-prediction of the diameter as L bu gets further downstream.
Information such as the design sketches of nasal sprays are often sensitive due to
corporate patents for the design, and detailed information such as the nozzle diameter,
pressure-swirl chambers and cone angles can be difficult to obtain. One method to
obtain the required information is to take an image of the spray device and measure
the parameters needed through imaging analysis software. The measurements in
Table 8.10 give approximate values, allowing a parametrical study to evaluate the
performance of each parameter.
In addition to the measured data, a 2D velocity field produced by a Particle
Image Velocimetry (PIV) system found that the exit velocity from the nozzle was
approximately 15 m/s produced from a continuous spray under an upstream pressure
of 600 kPa. Maximum velocity reached was 17 m/s approximately 0.1 m downstream
(Fig. 8.44 ).

Fig. 8.44 Single image
snapshot of the spray under
the PIV lasers, and the
resulting PIV 2D vector plot
which shows the averaged
mean droplet velocity field of
the spray nozzle