Hairpin Detection

AmarAli · January 29, 2017, 00:50

Hello everyone,

I'm trying to detect a hairpin vortex in the average field from DNS data set.
I tried to follow the procedure of Adrian (2007), sec II,
http://aip.scitation.org/doi/full/10.1063/1.2717527
but, unfortunately, I couldn't obtain same results.

The procedure is

1) Get the JPDF f(u,v) between u and v
2) Get the value of u and v (u0,v0) that maximize the ejection event in the second Quadrant Q2 such that -uvf(u,v) is maximum.
3) Conditionally average the velocity field around the point (u0,v0)
4) Calculate the swirling strength lambda_ci

Dose anyone have any suggestions?

Thanks a lot,

Amar

aerosjc · February 5, 2017, 18:50

If the input is averaged, can you expect to get vortex? I suspect it. I guess you should use raw velocity data.

AmarAli · February 5, 2017, 22:20

Thanks Jingchang.Shi for reply.

But actually, I tried both of them. I used the raw velocity field and the averaged one, and both introduce same results.

January 29, 2017, 00:50	Hairpin Detection	#1
AmarAli New Member Amar Join Date: Dec 2016 Posts: 7 Rep Power: 9	Hello everyone, I'm trying to detect a hairpin vortex in the average field from DNS data set. I tried to follow the procedure of Adrian (2007), sec II, http://aip.scitation.org/doi/full/10.1063/1.2717527 but, unfortunately, I couldn't obtain same results. The procedure is 1) Get the JPDF f(u,v) between u and v 2) Get the value of u and v (u0,v0) that maximize the ejection event in the second Quadrant Q2 such that -uvf(u,v) is maximum. 3) Conditionally average the velocity field around the point (u0,v0) 4) Calculate the swirling strength lambda_ci Dose anyone have any suggestions? Thanks a lot, Amar

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February 5, 2017, 18:50		#2
aerosjc Member Jingchang.Shi Join Date: Aug 2012 Location: Hang Zhou, China Posts: 78 Rep Power: 14	If the input is averaged, can you expect to get vortex? I suspect it. I guess you should use raw velocity data.

February 5, 2017, 22:20		#3
AmarAli New Member Amar Join Date: Dec 2016 Posts: 7 Rep Power: 9	Thanks Jingchang.Shi for reply. But actually, I tried both of them. I used the raw velocity field and the averaged one, and both introduce same results.