Cross Correlation Velocimetry

[Bastos17]

Thank you for the VI, I wouldn't have been able to do this !

I have done an experiment which is more realistic. A hot air flow pass through a 28 mm diameter pipe, with my thermocouples inside. There is a 15 mm gap between them, and the velocity measured with an anemometer is 0.7 m/s. So theoretically, the time delay must be 0.214 sec. But I can't find it. Here's the TDMS file of this experiment (duration : 60 sec at 100Hz)

Could you help me again please ? And thank you again !!!! 🙂

Bapt.

[Bastos17]

Here's your VI that I have worked one. I think I'm near, but I still haven't good results. Can someone hlep me please ?

BTW, the theoretical time is 0.0214 sec, and not 0.214 sec.

Bapt.

[johnsold]

Baptiste,

For an expected delay of 0.0214 s and a sampling period of 0.01 s you are going to have very poor resolution.  The second signal will be delayed about 2 samples.  Can you try a higher sampling rate, perhaps 500 Hz or 1 kHz?

Lynn

[Bastos17]

I can't have a higher sampling rate, the NI 9214 module's max sampling rate is 100 S/s. So I know I will have a very poor resolution, but I don't even see the 2 samples shifting. And even with a data set where the theoretical transit time is about 0.09 sec, I still can't visualize it. Also, it seems that the samples are not shifted when I saw them on the graph, but maybe it because I didn't dind the good ones.

Here is my data set with the max time lag.