Negative Volume Calculation for Cylindrical Objects

wrossell · June 21, 2021, 12:41

Hello again. I have recently been successful in simulating a rectangular box floating body using a similar input file to these included below, with the exception that now I am trying to simulation a cylinder. I have checked my inputs in order to make sure they are appropriate and accurate, and to the extent that I can tell, they are. I prescribed a homogeneous density (X 21) to the cylinder, and then upon running REEF3D, it reports a negative calculation of volume and a negative calculation for mass for the floating body as shown in the included image. I'm at a loss. Could someone please provide assistance in understanding what is causing these issues, and however to resolve them?

Edit: Since posting earlier, I have attempted to decrease mesh size and also cleared some previous present issues with my input files. The ones included below, along with the image reflect my current status and issues.

kamath · June 22, 2021, 03:12

Did it help with grid refinement?

wrossell · June 22, 2021, 07:54

Kamath: Unfortunately no, grid refinement did not help the problem at all. The calculation error still persisted, and once the grid was made too small, I returned to an earlier issue that has been previously addressed on the forum where a segmentation fault occurred.

kamath · June 23, 2021, 02:57

I can reproduce the error, I will get back to you soon.

You get a segmentation fault probably due to running out of memory? The number of cells increases very quickly when you refine a 3D domain with regular grids.

You could explore using the stretched grids with B 2 and B 101 /102/ 103 to get a grid that is focused around your structure

valgrinda · June 23, 2021, 07:16

I would like to comment that the volumen is not negative, but very small. We will check this.

Another thing: you use 2 processors, but go for 13 mil. cells, that could be be too much to run this simulation efficiently.

wrossell · June 23, 2021, 15:55

I will explore the of stretched grids, Kamath. I look forward to your response on the error.

Dr. Bihs, I see that in the attached image the volume is only very small. I apologize for not addressing that. The confusion is due to me editing the original post after making some alterations of my own while trying to overcome the issue. I assure you, however, that in previous iterations, I did encounter negative quantities as well. So I thought it was worth addressing.

kamath · June 24, 2021, 03:21

Please download the latest RC, there was bug with the X 132 command, fixed now.

Hope that helps

wrossell · June 24, 2021, 15:17

I have done as you instructed, and the volume calculation is working properly now. Thank you all.

June 22, 2021, 03:12		#2
kamath Senior Member Arun Kamath Join Date: Nov 2014 Location: Trondheim, Norway Posts: 265 Rep Power: 13	Did it help with grid refinement? __________________ Arun X years with REEF3D

June 23, 2021, 02:57		#4
kamath Senior Member Arun Kamath Join Date: Nov 2014 Location: Trondheim, Norway Posts: 265 Rep Power: 13	I can reproduce the error, I will get back to you soon. You get a segmentation fault probably due to running out of memory? The number of cells increases very quickly when you refine a 3D domain with regular grids. You could explore using the stretched grids with B 2 and B 101 /102/ 103 to get a grid that is focused around your structure wrossell likes this. __________________ Arun X years with REEF3D

June 23, 2021, 07:16		#5
valgrinda Super Moderator Hans Bihs Join Date: Jun 2009 Location: Trondheim, Norway Posts: 377 Rep Power: 17	I would like to comment that the volumen is not negative, but very small. We will check this. Another thing: you use 2 processors, but go for 13 mil. cells, that could be be too much to run this simulation efficiently. wrossell likes this. __________________ Hans Bihs Team REEF3D www.reef3d.com

June 24, 2021, 03:21		#7
kamath Senior Member Arun Kamath Join Date: Nov 2014 Location: Trondheim, Norway Posts: 265 Rep Power: 13	Please download the latest RC, there was bug with the X 132 command, fixed now. Hope that helps __________________ Arun X years with REEF3D

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June 22, 2021, 07:54		#3
wrossell New Member Will Join Date: May 2021 Posts: 11 Rep Power: 4	Kamath: Unfortunately no, grid refinement did not help the problem at all. The calculation error still persisted, and once the grid was made too small, I returned to an earlier issue that has been previously addressed on the forum where a segmentation fault occurred.

June 23, 2021, 15:55		#6
wrossell New Member Will Join Date: May 2021 Posts: 11 Rep Power: 4	I will explore the of stretched grids, Kamath. I look forward to your response on the error. Dr. Bihs, I see that in the attached image the volume is only very small. I apologize for not addressing that. The confusion is due to me editing the original post after making some alterations of my own while trying to overcome the issue. I assure you, however, that in previous iterations, I did encounter negative quantities as well. So I thought it was worth addressing.

June 24, 2021, 15:17		#8
wrossell New Member Will Join Date: May 2021 Posts: 11 Rep Power: 4	I have done as you instructed, and the volume calculation is working properly now. Thank you all.