Sampling at time-varying locations

mturcios777 · April 16, 2010, 19:07

To my knowledge no one has asked this question, so here goes.

I am currently calculating a field that exists only on wall patches. I would like to be able to use the sample utility to extract the value at certain locations. However, the boundary is moving (translating only), and I can't think of a way to use sample to get the values.

I know where the mesh starts, so one possibility I was mulling was to change sample so that it would identify the patch that is at the initial sampling location and only output data from that patch afterwards.

I've done similar things before using very basic for loops, but I was looking do things using pre-existing OpenFOAM code for better performance. What are some pieces of code I could look at to get ideas?

Due to legacy support I am using OpenFoam 1.4 (will be making the transition to 1.(whatever-the-current-version-is) in about a year).

mturcios777 · July 15, 2010, 17:58

As a follow up, I see that as of OF1.6, there is the option to sample a movingWall. From the sampleDict in the sample application directory, it looks like I can only sample the patch itself, is this correct?

mturcios777 · October 12, 2010, 19:58

One solution I thought of was writing a script that changed the sampleDict sample line points, since its only one coordinate that is required to change. This is tricky as I would have to be able to identify the exact place the coordinate occurs in. Then I would have to call sample with the -time argument. This looks very messy.

I was poking around the documentation for ParaView, and saw that "Programmable Filter" might do the trick. I don't have much experience with Python though.

What I would like to do is use "Programmable Filter" on "Plot over Line" to shift the position of the line so that it remains in the same place relative to a particular patch. I know how to calculate the displacement based on the current time, but I don't know how to

1) Retrieve the time
2) Change the coordinates of the line endpoints

Anyone have ideas of how to do this? This could actually open up a lot of cool stuff.

April 16, 2010, 19:07	Sampling at time-varying locations	#1
mturcios777 Senior Member Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 740 Rep Power: 28	To my knowledge no one has asked this question, so here goes. I am currently calculating a field that exists only on wall patches. I would like to be able to use the sample utility to extract the value at certain locations. However, the boundary is moving (translating only), and I can't think of a way to use sample to get the values. I know where the mesh starts, so one possibility I was mulling was to change sample so that it would identify the patch that is at the initial sampling location and only output data from that patch afterwards. I've done similar things before using very basic for loops, but I was looking do things using pre-existing OpenFOAM code for better performance. What are some pieces of code I could look at to get ideas? Due to legacy support I am using OpenFoam 1.4 (will be making the transition to 1.(whatever-the-current-version-is) in about a year).

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July 15, 2010, 17:58		#2
mturcios777 Senior Member Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 740 Rep Power: 28	As a follow up, I see that as of OF1.6, there is the option to sample a movingWall. From the sampleDict in the sample application directory, it looks like I can only sample the patch itself, is this correct?

October 12, 2010, 19:58		#3
mturcios777 Senior Member Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 740 Rep Power: 28	One solution I thought of was writing a script that changed the sampleDict sample line points, since its only one coordinate that is required to change. This is tricky as I would have to be able to identify the exact place the coordinate occurs in. Then I would have to call sample with the -time argument. This looks very messy. I was poking around the documentation for ParaView, and saw that "Programmable Filter" might do the trick. I don't have much experience with Python though. What I would like to do is use "Programmable Filter" on "Plot over Line" to shift the position of the line so that it remains in the same place relative to a particular patch. I know how to calculate the displacement based on the current time, but I don't know how to 1) Retrieve the time 2) Change the coordinates of the line endpoints Anyone have ideas of how to do this? This could actually open up a lot of cool stuff.