I want to calculate the flow rate of water through holes in a mesh.

In the following hypothetical situation water is flowing through a 13mm diameter pipe at a velocity of 3 meters per second and a pressure of 0.55 mega pascals. (I do not know the water temperature or the surface roughness of the interior of the pipe, or whether the flow is laminar or turbulent)

Inside the pipe is a mesh, also 13mm in diameter, 2mm thick. The mesh contains 69 holes, each hole is 0.2mm in diameter.

Is it possible to calculate (or perhaps I should say estimate) the flow rate of the water through each individual hole in the mesh?

I am assuming that the flow rate through a 0.2mm diameter hole will be less than the flow rate through the 13mm diameter pipe, but I don’t know how to calculate this.

  • $\begingroup$ You have enough information to calculate a statistical average for each hole. $\endgroup$ Oct 16, 2020 at 1:04
  • $\begingroup$ Thank you Adrian Howard. Could you perhaps tell me how I can do that? I don’t know the calculations to use. $\endgroup$
    – EddieP
    Oct 16, 2020 at 1:06
  • $\begingroup$ How much have you researched this subject of pressure drop in flow through screen? $\endgroup$ Oct 16, 2020 at 10:53

1 Answer 1


Figure the volume of 3 meters of 13 mm pipe, this is the flow rate per second in the pipe. Then divide the volume by 69 and you will have the average flow rate per second for each hole. The precise flow rate for each individual hole would depend on multiple variables, but the total of the 69 holes will equal the flow rate of the main pipe as flow rate in volume per time does not change.


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