box position for FlowTool


I am using the flowTool to get volume flow rate through an opening in between two chambers in a geometry where fluid passes from one chamber through that opening.

To get the accurate flowrate, should I place the box such that that opening falls somewhere in the middle of the box that encompass the opening coordinates? Or should I try to position the box such that the opening falls flush on any of the face of the box that is same size of the opening?


  • It is a bit difficult to comment on w/o any pictures, but could you perhaps do both and see the end result?

    Then you should have the insight needed to decide what is most suitable for your understanding of the physics.

    Kind regards

  • hello,

    i am simulating the cowl plenum system of an automotive. that is the passages infront of the windshield that takes rain water down. so these are hidden underneath the hood area close to the wipers. There are two openings on LHS and RHS of those conduits. Both openings have 4 flaps. I am monitoring the flow rate through the LHS flaps and I removed those flaps when I simulated with SPH.

    In the attached pictures, in the Box1 picture I have shown the box around those flaps. In simulation the flaps are removed as I said before. But I kept those in the snap shot just for demonstration. However, the flow measurement was giving zero flow rate. This can be seen in the attached xls file.

    In the 2nd attached picture, box 2 is a bigger size box as I thought may be there is no fluid that pass through the box 1 because of insufficient time being simulated which would allow some fluid to pass through that box. But still I see zero flow are. See 2nd attached xls file.

    Please let me know if any set up is incorrect. Thanks.

  • Please can you send the following files to

    • XML file (no need to send to us any STL or important geo)
    • these two .png
    • these tow .xlsx
    • bat (or sh) file you use to compute FlowTool
    • boxes.txt that FlowTool is using


  • thanks. I have sent an email.

  • Email received, we will check when possible

  • Hello Asalih,

    were you able to extract any useful information from the files I sent? Any comment?

  • edited October 2021

    No - I do not download images / data files sorry - I only see what is directly visible on the forum.

    If you are struggling with understanding the flow tool (which I do not have much experience with either), I would advise to make a simplified case of a 3d inlet-outlet flow and then move the position of the boxes to see what difference in results you get.

    This would allow you to understand the tool a bit better and know what is best for your interesting chamber simulation case - sounds like a really fun simulation!

    Kind regards

  • Hello Alex amd ASalih,

    I created a simplified case where water is flowing down from a top chamber to a bottom chamber through a conduit and the flow tool seem to work fine as the flowrate through it first increases and then becomes zero as all the water paases from top chamber to bottom chamber through the conduit. Then Also I tried a dfferent size flow measurement box and the two results are shown in the plot.

    That means the procedure I am following is correct. So, I am not sure why it is not working for the other case that I am concerrned about. dualSphysics already has some files which I emailed to them (see notes above).

  • hello,

    Is ther any comment from the developers on this topic and the files I shared before? Thanks and happy new year.

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