How to enhance the correlation and SNR while measuring the velocity profile induced by a propeller jet

Hi

I am conducting an experiment regarding to the propeller wash by using the ADVP Vectrino II.

HpDuring my experiment, for the low rpm of propeller, the correlation and SNR can be acheived at around 85 and 45, respectively.

however, as the rpm increases from 400 to 1200, the highly tubulent flow makes the reduction of correlation and SNR to 40 and 30, respectively.

Finally, the velocity measuremnts do not look good.

I used two ways to generate the seeding particles.

One is body powder the other one is bubble generator.

both works very well for low flow condition, but for high flow with highly 3-d turbulent flow, it seems not good.

Thank you very much for your kind help.

Dino

Hi Dino,

  The best way to increase correlation in a highly turbulent flow is to adjust your velocity range. For a highly turbulent flow you will typically need a much larger velocity range than the mean flow would suggest. For your conditions, it sounds like you will be working with a larger velocity, which for the Vectrino II means dual-PRF operation. You'll need to ensure there is adequate SNR to make good measurements in this type of flow as well.

  I think many researchers have used things like talc powder and micro-bubbles to seed flows for acoustic instruments with good success. Mean SNRs of 30 are not bad for the Vectrino II, so I think adjusting the velocity range should handle most of the low correlation issue.

 

P.J.

Hi P.J.

Thank you so much.

Actually, I try your suggestion this morning and it works.

Thank you in advance.

Dino