Pipe Flow- Comparison Fluent-OpenFoam

Federer83 · November 1, 2019, 13:41

Dear all,

I run my case (pipe flow with mass flow at intlet and pressure outlet) both in Fluent and in OpenFoam.
The BCs are the following:
Inlet:
massflow=0.11kg/s
Outlet
Pressure outlet
Fluid: water

Operating Pressure: 1 bar

Fluent: steady state, pressure based solver, standard setup for numeric.
OpenFoam: icoFoam with kinematic viscosity for water
Same mesh has been used for comparison reason. The inlet is placed upstream with a semi-spherical shape.

Results:
Pressure at inlet:
a) Fluent :about 5 bar
b) OpenFoam: about 2.4 bar

Any idea why the OpenFoam is not matching the fluent result?

Many thanks in advance.

Bloerb · November 1, 2019, 14:11

Since you are not giving any information....my best guess is....because you did something wrong.

You are using icoFoam, hence this must be laminar flow. For laminar flow in a pipe there is an analytic solution. Which software is closer to the truth? A Reynoldsnumber, diameter, the actual boundary conditions used etc, a case etc, might be needed to find that error.

Federer83 · November 1, 2019, 14:18

Sorry i was using simpleFoam. It is a turbulent flow. Pipe Diameter 2mm

cryabroad · November 4, 2019, 01:22

Are you running RANS? Which turbulence model are you using in both solvers?

As pointed out by others, you can estimate the pressure drop along the pipe. For turbulent flow you can use the Moody diagram I guess.

GerhardHolzinger · November 4, 2019, 04:12

Depending on the choice of turbulence model, you can get pressure-differences that are way off, if you get y+ wrong. The OP provides too little information for any further discussion/suggestions.

November 1, 2019, 13:41	Pipe Flow- Comparison Fluent-OpenFoam	#1
Federer83 New Member Fab Join Date: Dec 2018 Posts: 13 Rep Power: 7	Dear all, I run my case (pipe flow with mass flow at intlet and pressure outlet) both in Fluent and in OpenFoam. The BCs are the following: Inlet: massflow=0.11kg/s Outlet Pressure outlet Fluid: water Operating Pressure: 1 bar Fluent: steady state, pressure based solver, standard setup for numeric. OpenFoam: icoFoam with kinematic viscosity for water Same mesh has been used for comparison reason. The inlet is placed upstream with a semi-spherical shape. Results: Pressure at inlet: a) Fluent :about 5 bar b) OpenFoam: about 2.4 bar Any idea why the OpenFoam is not matching the fluent result? Many thanks in advance.

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November 1, 2019, 14:11		#2
Bloerb Senior Member Join Date: Sep 2013 Posts: 353 Rep Power: 20	Since you are not giving any information....my best guess is....because you did something wrong. You are using icoFoam, hence this must be laminar flow. For laminar flow in a pipe there is an analytic solution. Which software is closer to the truth? A Reynoldsnumber, diameter, the actual boundary conditions used etc, a case etc, might be needed to find that error.

November 1, 2019, 14:18		#3
Federer83 New Member Fab Join Date: Dec 2018 Posts: 13 Rep Power: 7	Sorry i was using simpleFoam. It is a turbulent flow. Pipe Diameter 2mm

November 4, 2019, 01:22		#4
cryabroad Senior Member Ruiyan Chen Join Date: Jul 2016 Location: Hangzhou, China Posts: 162 Rep Power: 9	Are you running RANS? Which turbulence model are you using in both solvers? As pointed out by others, you can estimate the pressure drop along the pipe. For turbulent flow you can use the Moody diagram I guess.

November 4, 2019, 04:12		#5
GerhardHolzinger Senior Member Gerhard Holzinger Join Date: Feb 2012 Location: Austria Posts: 339 Rep Power: 28	Depending on the choice of turbulence model, you can get pressure-differences that are way off, if you get y+ wrong. The OP provides too little information for any further discussion/suggestions.