Puff Testing
puff_testing_720.mp4Why Puff Testing?
Puff testing is a critical part of preparing for a wind tunnel test. Pressure tapping is generally a very time consuming process with many sources of potential error. These include (but are not limited to):
Squashing tubes in regions of high tube concentration
Damaging the flexible tubing what attaching with pliers or cutting on the brass tap attachment
Blocking of the brass tubes due from glue during installation or dust from sanding
Damaging the brass tube/not ensuring both orifices are open after cutting.
Generally, you do not have access to the wind tunnel before the testing day, meaning that you might only identify faulty taps during the initial runs, requiring you to waste precious testing time repairing taps. In addition, sometimes it is not easily noticeable what a tap is blocked, especially if you are expecting regions of flow with pressured similar to static.
Puff testing allows you to check that all the taps are functional prior to testing by providing a (more or less) known pressure to a port and watching the response. Please watch the video here outlining how to complete a puff test.
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Troubleshooting
If a faulty port it identified, it is key that a troubleshooting is carried out in a logical order. I always check the potential cause which is the least invasive and the move up to the most invasive. This saves time and prevents unnecessary work. For example, the pressure tap system using the manometers shown in the video above has 5 components.
The manometer tube
The larger flexible tube connecting to the manometer tube
The syringe adaptor
The flexible tubing connecting to the brass tube
The brass tubes
It does not make sense to go straight into removing the brass tube, as it has already been cut to shape, drilled out and glued in. The following steps should be done.
Check the manometer tube has fluid/is not damaged, if yes then move to step 2.
Blow into the large flexible tube and see if there is a response, if yes then move to step 3.
Check the syringe is not damaged, if not damaged the move to step 4.
Check the flexible tubing is not kinked or damaged. Blow into the signal end and see if there is a response on the manometer. If not, then you should remove the brass tubing and replace it with a new piece. Then redo the puff test and observe if there is a response.
If using the scanivalve then there are less parts of the system. The procedure should be:
Using the live view software and a tube connected directly to the port of interest, blow lightly and observe if a signal is recorded. If yes, then move to step 2.
Complete step 4 as above