Aim – to obtain experience and training of using the PIV system for use on subsonic wind tunnel.
The session was held in room 41 of the Heavy Engineering Building at the University of Brighton. It was conducted by Guillaume De Sercey. A brief was given before the demonstration, the main objective of the session was to measure the airflow around certain objects, using the laser beam to target air particles around the object. The displacement of the particles between the two consecutive laser pulses are recorded by one or two camera and processed to calculate the flow velocity. Models may be inserted to disturb the air flow.
Figure 1
In figure 1 it can be seen the placement of the PIV system and the wind tunnel. Airflows in between the tunnels and a car model is placed in between it to measure the air flow around it. This is done by beaming laser from the YAG laser (532 nm wavelength) of class 4 which targets the air particles around the car.
The air flow and other parameters are taken from the instrument shown in figure 2.
Figure 2
Once the laser is on safety goggles must be worn in order to avoid damages that the laser can cause.
Figure 3
The laser must be connected to the room interlock system, which requires all doors to be closed and the interlock system to be powered for the laser shutter to open.
Figure 4
The laser light scattered by these particles is then recorded by the PIV camera. The pulsing of the laser is normally controlled by software which only pulses the laser after the operator has acknowledged a warning and only for the duration of the recording.
Figure 5
Figure 5 shows the image taken by the camera before the airflow and figure 6 shows the the image taken after the air starts flowing through the wind tunnel.
Figure 6
The airflow is calculated by superimposing both the images one top of the other and a grid is placed on the image to calculate the distance between the air particles on each grid.