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Flow Visualization and Particle Dispersion Measurements Inside an Ambulance Rear Saloon while Stationary and in Motion
Abstract:
The following article presents flow field and particle dispersion data from a
United Kingdom (UK) National Health Service (NHS) ambulance, under static and
dynamic driving conditions and when using different ventilation modes. Data were
recorded using laser sheet flow visualization, particle image velocimetry (PIV),
and hot wire anemometry from a common plane positioned about the patient
centerline. Results indicated a significant influence of the ceiling fan
ventilation system on gross flow field behavior, with the ventilation fan on
extract or intake mode. With either ventilation mode, flow velocities in the
patient region were found to double from a quiescent condition to around 50-100
mm/s. Particle dispersion data also showed dispersion decay rates over five
times faster when using the ceiling fan extraction system. All these results
were consistent when the vehicle was stationary or driving at a constant speed
of 60 mph. However, with the vehicle under dynamic driving conditions, such as
acceleration or braking, the regular flow patterns were substantially disrupted,
with the bulk movement of the flow in the direction of the acceleration or
braking action. Under these dynamic conditions, the magnitude of the net
velocity change on the fluid exceeded any flow generated from the ceiling
ventilation system.