# Total pressure drop

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 January 26, 2003, 14:40 Total pressure drop #1 Swapnil Guest   Posts: n/a Hi all, I am working on a system comprised of two triangular ducts intersecting each other at 90 degrees. There are two inlets and two outlets. At the intersection the flow gets diverted and a fraction of the flow coming from one inlet (say inlet 1) goes straight (outlet 1) and another fraction bends at 90 degrees and goes to outlet 2 . Same thing happens to flow from inlet 2. How to calculate the total pressure drop for this system. Regards, Swapnil.

 January 26, 2003, 19:56 Re: Total pressure drop #2 Jan Rusås Guest   Posts: n/a I guess that the difference of a volume average of the total pressure at the outlet and inlet could give the answer. (mass average will do if the flow is incompressible)

 January 27, 2003, 11:21 Re: Total pressure drop #3 fly Guest   Posts: n/a Hi, Jan: Did you compare the simulation results with real case? I compared the pressure drop. It seems the CFX results are smaller than that of regular method. fly

 January 27, 2003, 12:16 Re: Total pressure drop #4 Hannah liang Guest   Posts: n/a Hi, Fly: I found the same result with you. And If I refine the mesh, the result even become smaller. Could you find the explaination from theory in books? Hannah

 January 27, 2003, 15:22 Re: Total pressure drop #5 Swapnil Guest   Posts: n/a Hi fly and Hannah liang , are you people working on triangular ducts?

 January 27, 2003, 17:33 Re: Total pressure drop #6 Jan Rusås Guest   Posts: n/a I would be surprised if the values was exactly the same. There are some uncertainities in both measurements and numerical results. I know it is very difficult to get exact numbers when looking for the pressure drop. I have had some succes with predicting pressure drop when using higher order differencing, double precision and doing a grid independency investigation and calculating an estimate of the pressure drop from a Richardson extrapolation of the pressure drop obtained with the three grids. Regards Jan

 January 28, 2003, 10:38 Re: Total pressure drop #7 sxf Guest   Posts: n/a Hi, Jan: I agree with your on the pressure drop for measurements and numerical results. But I think they should be the same on some extend. Could you share your success results with me. Thanks SXF

 January 28, 2003, 14:27 Re: Total pressure drop #8 Jan Rusås Guest   Posts: n/a Dear sxf, You state that "they should be the same on some extend". I do agree with you, what could I else ). But when will you say you are satisfied, 5% or 10% or 20% etc. What kind of accuracy should be expected from a numerical code with many assumptions and with many constants based on old experiments with an accuracy on???. I remember once a paper with different test cases where several numerical codes was investigated, but I do not remember the exact values , but one should not be surprised if there are some deviations. Regards Jan

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