# Problems with input parameters

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 November 14, 2019, 15:55 Problems with input parameters #1 New Member   Ярослав Join Date: Nov 2019 Posts: 1 Rep Power: 0 Hello, I'm new to Star CCM+. Please help me. Imagine a pipe and water flows in it. I only know the value of the differential pressure, such as inlet pressure(P1) and outlet pressure (P2). Given: P1-P2=15 atmospheres (atm). How do I do that? I think it is necessary to create a field function, but how? P.S. forgive me for my English. I don't speak it well.

November 14, 2019, 22:53
#2
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Chaotic Water
Join Date: Jul 2012
Posts: 140
Rep Power: 9
Inlet: Stagnation Inlet with Pressure set to 15 atm
Outlet: Pressure Outlet with Pressure set to 0 atm
All those pressure values are given with respect to Reference Pressure (in Continua -> Physics -> Reference Values -> Reference Pressure) which is 1 atm by default, so absolute pressure would be 16 atm and 1 atm.
No difference for incompressible flow, but keep that in mind for compressible flows.

But if you just set 15 atm at Inlet - you'll get high velocity in first iterations, so it is better to increase the pressure at inlet as iterations go, for example via a Field Function:

Quote:
 (\$Iteration <= 100) ? \$Iteration/100 * 15E5 // keep in mind that default units (m, s, g, K, Pa) are used : 15E5
this will make pressure on the inlet grow from 0 (+Reference Pressure) to 15 atm in 100 iterations.

PS Если с английским тяжко - найди группу по стар вконтакте.
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 Tags inlet and outlet pressure, star ccm+