2D Pressure Drop through pipe bottleneck

turbulentFlowEnjoyer · April 13, 2023, 04:24

Good day everyone,

We are tasked to study, using NX, a 2D laminar flow throughout a uniform pipe that goes through a brief bottleneck before seeing its initial section restored.
After doing this with CFD software Siemens NX, we would like to back our results with some litterature. However, all we've been able to find is references for 3D cases.
Hence, my question is the following: has anyone got knowledge of specific theoretical litterature about such 2D flows, or knows how to extrapolate the 3D results to 2D (I suppose this is not trivial, since for instance taking the limit for the z-dimension going to 0 changes geometry and adimensionnal values which inherently modifies the flow)

Thanks in advance! :-)

LuckyTran · April 14, 2023, 08:33

Look up a venturi calculator. OEMS of venturis normally provide this for free.

And check out the ASME standards for how to calculate flow in a venturi, etc. In particular:
MFC-3M - 2004 or more recent and AME PTC 19.5 - 2004 or more recent

Turbulent flows are much easier to extrapolate since they are less dependent on BL effects. None of these sources will tell you "this is how to go from 2D to 3D." But they tell you what a 3D flow depends on and how real flowrates are calculated in real life. You can reapply the same foundation know-how to calculate flowrates and losses in 2D devices .

In summary, you determine the area ratio of your 2D case ( $\beta$ ), get the loss coefficient there, and apply it to the 3D case.

April 13, 2023, 04:24	2D Pressure Drop through pipe bottleneck	#1
turbulentFlowEnjoyer New Member Virgil Join Date: Apr 2023 Posts: 1 Rep Power: 0	Good day everyone, We are tasked to study, using NX, a 2D laminar flow throughout a uniform pipe that goes through a brief bottleneck before seeing its initial section restored. After doing this with CFD software Siemens NX, we would like to back our results with some litterature. However, all we've been able to find is references for 3D cases. Hence, my question is the following: has anyone got knowledge of specific theoretical litterature about such 2D flows, or knows how to extrapolate the 3D results to 2D (I suppose this is not trivial, since for instance taking the limit for the z-dimension going to 0 changes geometry and adimensionnal values which inherently modifies the flow) Thanks in advance! :-)

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April 14, 2023, 08:33		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 66	Look up a venturi calculator. OEMS of venturis normally provide this for free. And check out the ASME standards for how to calculate flow in a venturi, etc. In particular: MFC-3M - 2004 or more recent and AME PTC 19.5 - 2004 or more recent Turbulent flows are much easier to extrapolate since they are less dependent on BL effects. None of these sources will tell you "this is how to go from 2D to 3D." But they tell you what a 3D flow depends on and how real flowrates are calculated in real life. You can reapply the same foundation know-how to calculate flowrates and losses in 2D devices . In summary, you determine the area ratio of your 2D case ( $\beta$ ), get the loss coefficient there, and apply it to the 3D case.