## Laminar flow in pipe-wrong results

wojwach83
Posts: 6
Joined: 24 Apr 2016, 18:27
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### Laminar flow in pipe-wrong results

Hi, I'm new in this forum and new user of elmer. PLease tell me what is wrong with my simulation. I analized flow from this article

It's about fluid velocity development in laminar pipe flow. The inner diameter is 24mm, medium is water in room temp. Profile of full development velocity should be after 1,33m. Vo=38,7mm/s and expected Vmax after 1,33m flow is 77,4mm/s.
In my Elmer's simulation Vmax=58mm/s
In laminar flow in pipe Vmax=2xVo. In Elmers simulation Vmax=1,5xVo , What is wrong?
I attach my results
Wojtek
Attachments
Molki Elmer.jpg
Elmers results by Paraview

wojwach83
Posts: 6
Joined: 24 Apr 2016, 18:27
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### Re: Laminar flow in pipe-wrong results

Now i know what's wrong. I used rectangular mesh and coordinate system as cartesian so the case is as caonical flow (like in tutorial 6) How to set boundary conditions to make a pipe flow i rectangular mesh?

wojwach83
Posts: 6
Joined: 24 Apr 2016, 18:27
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### Re: Laminar flow in pipe-wrong results

there is my SIF

CHECK KEYWORDS Warn
Mesh DB "." "."
Include Path ""
Results Directory ""
End

Simulation
Max Output Level = 4
Coordinate System = Cartesian
Coordinate Mapping(3) = 1 2 3
Steady State Max Iterations = 100
Output Intervals = 1
Timestepping Method = BDF
BDF Order = 1
Solver Input File = case.sif
Post File = case.ep
End

Constants
Gravity(4) = 0 -1 0 9.82
Stefan Boltzmann = 5.67e-08
Permittivity of Vacuum = 8.8542e-12
Boltzmann Constant = 1.3807e-23
Unit Charge = 1.602e-19
End

Body 1
Target Bodies(1) = 2
Name = "Body 1"
Equation = 1
Material = 1
End

Solver 2
Equation = Navier-Stokes
Procedure = "FlowSolve" "FlowSolver"
Variable = Flow Solution[Velocity:2 Pressure:1]
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-3
Nonlinear System Max Iterations = 20
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStab
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e-3
BiCGstabl polynomial degree = 2
Linear System Preconditioning = ILU1
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End

Solver 1
Equation = Result Output
Output File Name = case
Output Format = Vtu
Procedure = "ResultOutputSolve" "ResultOutputSolver"
Exec Solver = Always
End

Equation 1
Name = "navier-stokes"
Active Solvers(1) = 2
End

Equation 2
Name = "Equation 2"
Active Solvers(1) = 1
End

Material 1
Name = "Water (room temperature)"
Heat Conductivity = 0.58
Heat Capacity = 4183.0
Viscosity = 1.004e-3
Sound speed = 1497.0
Heat expansion Coefficient = 0.207e-3
Porosity Model = Always saturated
Relative Permittivity = 80.1
Density = 998.23
End

Boundary Condition 1
Target Boundaries(1) = 4
Name = "inlet"
Velocity 1 = 0.0385
Velocity 2 = 0.0
End

Boundary Condition 2
Target Boundaries(1) = 1
Name = "outlet"
Velocity 2 = 0.0
End

Boundary Condition 3
Target Boundaries(1) = 2
Name = "walls"
Velocity 1 = 0.0
Velocity 2 = 0.0
End

raback
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Joined: 22 Aug 2009, 11:57
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Location: Espoo, Finland
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### Re: Laminar flow in pipe-wrong results

Hi

Use "axi symmetric" coordinate system and set your mesh such that (x,y) corresponds to (r,z). This means that in your mesh x \in [0,R].

-Peter

wojwach83
Posts: 6
Joined: 24 Apr 2016, 18:27
Antispam: Yes

### Re: Laminar flow in pipe-wrong results

Thank You for interest. I made a mesh, like in attachment, is it correct?
Attachments MESH1.jpg (130.34 KiB) Viewed 3112 times

wojwach83
Posts: 6
Joined: 24 Apr 2016, 18:27
Antispam: Yes

### Re: Laminar flow in pipe-wrong results

I think now is correct, but what boundary condition set on bottom edge (axis)?
left edge is inlet, top edge is wall, right edge is outlet
Attachments
MESH2.jpg