Natural convection problem

[GastónGarcía]

Hi, I'm modelling something like a heater, it's a rectangle, one of its boundaries have imposed temperature and only a very little velocity (just for destabilize), the others have heat flux zero and no slip wall. The problem is that I have no convection, even in long times. Anyone can help me please?
Here is the sif file

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 = Transient
Steady State Max Iterations = 1
Output Intervals = 1
Timestepping Method = BDF
BDF Order = 2
Timestep intervals = 60
Timestep Sizes = 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) = 1
Name = "Body 1"
Equation = 1
Material = 1
Initial condition = 1
End

Solver 2
Equation = Heat Equation
Procedure = "HeatSolve" "HeatSolver"
Variable = -dofs 1 Temperature
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-8
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-8
Linear System Preconditioning = ILU0
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 = 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-8
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-6
Linear System Preconditioning = ILU0
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End

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

Material 1
Name = "Water (Density temperature dependent)"
Viscosity = 1.002e-3
Heat expansion Coefficient = 0.207e-3
Compressibility Model = Incompressible
Heat Conductivity = 0.58
Sound speed = 1497.0
Heat Capacity = 4183.0
Density = variable temperature;real;0 999.8;5 1000.0;10 998.7;15 996.1;20 994.2;25 992.0;30 989.6;35 987.1;40 985.2;45 983.2;50 981.1;55 978.7;60 976.2;65 973.6;70 970.8;75 967.9;80 964.8;90 965.3;100 958.4;end;;
End

Initial Condition 1
Name = "InitialCondition 1"
Velocity 2 = 0
Pressure = 0
Velocity 1 = 0
Temperature = 10
Velocity 3 = 0
End

Boundary Condition 1
Target Boundaries(1) = 1
Name = "BoundaryCondition 1"
Heat Flux = 0
Noslip wall BC = True
End

Boundary Condition 2
Target Boundaries(1) = 2
Name = "BoundaryCondition 1"
Heat Flux = 0
Noslip wall BC = True
End

Boundary Condition 3
Target Boundaries(1) = 3
Name = "BoundaryCondition 1"
Heat Flux = 0
Noslip wall BC = True
End

Boundary Condition 4
Target Boundaries(1) = 4
Name = "BoundaryCondition 2"
Velocity 3 = 0
Velocity 1 = 0
Velocity 2 = 1e-9
Temperature = 40
End

Thanks

[janlietaer]

Hello
Maybe moving

Velocity 1 = 0
Velocity 2 = 1e-9

from the Boundary Condition to the Initial condition?
jan

[GastónGarcía]

Janlietaer, thanks, but I proved it and I lost convergence. My model seems to work ok, but the results shows like the solvers works separated, I noticed that the velocity in my boundary got into the mesh only for viscosity, and the thermal solution is only diffusive. Porbably I'm making a mistake, but I can't find it.
Thanks

[raback]

Hi, It seems that you have no body force defined. It could be just "Boussinesq=True" which uses the heat expansion, or if you want to use the variable density then probably set "Flow BodyForce 2 = -9.81". Preferably not both at the same time. There is a working tutorial on this case. -Peter

[GastónGarcía]

Thank you Peter, I really didn't find in the tutorial, a case using natural convection with variable density. I'll prove with the "flow bodyforce".
Thanks again
Gastón