Elmer Discussion Forum

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
"https://www.google.pl/url?sa=t&rct=j&q= ... Gg&cad=rja"

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
Please answer
Wojtek

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?

there is my SIF

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

Simulation
Max Output Level = 4
Coordinate System = Cartesian
Coordinate Mapping(3) = 1 2 3
Simulation Type = Steady state
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

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

Thank You for interest. I made a mesh, like in attachment, is it correct?

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

I found the answer in older posts