[mabinty]

Dear all!

I m about to simulate half of a symmetric 2D 1x1m2 domain, with hot air entering from an inlet in the floor. The sides are open (ambient air can enter). My interest lays in the heat transfer to the ceiling at steady state. Unfortunately I m not able to reach a steady state as the velocities in the domain constantly increase over simulation time (total time 400s). Another strange fact is a min temperature in the air region slightly below ambient temperature (see log data). I observed that the increase in velocity is smaller with finer mesh (hex mesh) but still there. Below some specifications of my set-up are posted.

I would greatly appreciate your comments. Thanks in advance!
Aram

--- discretization schemes and solver settings ---

taken from default settings

--- BC for the air region ---

_U
inlet: fixedValue uniform (0 0.8 0);
floor: fixedValue uniform (0 0 0);
air_to_ceiling: fixedValue uniform (0 0 0);
minX: symmetryPlane;
maxX: pressureDirectedInletOutletVelocity;
inletDirection uniform (1 0 0);
value uniform (0 0 0);

_T
internalField: uniform 293;
inlet: fixedValue uniform 473;
floor: zeroGradient
air_to_ceiling: solidWallMixedTemperatureCoupled;
neighbourRegionName ceiling;
neighbourPatchName ceiling_to_air;
neighbourFieldName T;
K K;
value uniform 293;
minX: symmetryPlane;
maxX: inletOutlet;
inletValue uniform 293;
value uniform 293;

_epsilon (for standard k-eps): initial value 0.002;
inlet: fixedValue uniform 0.002;
zeroGradient for all other boundaries

_k (for standard k-eps): initial value 0.01;
inlet: fixedValue uniform 0.01;
zeroGradient for all other boundaries

_pd
maxX: zeroGradient;
fixedFluxBuoyantPressure uniform 0; for all other boundaries

_p
initial value 100000
inlet: zeroGradient
floor and air_to_ceiling: calculated
minX: symmetryPlane;
maxX: fixedValue uniform 100000;

--- log data from the last time step ---

Solving for fluid region air
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for h, Initial residual = 1.271221e-06, Final residual = 6.479811e-08, No Iterations 1
Min/max T:min(T) [0 0 0 1 0 0 0] 292.4249 max(T) [0 0 0 1 0 0 0] 473
GAMG: Solving for pd, Initial residual = 0.3610631, Final residual = 0.0001952987, No Iterations 1
GAMG: Solving for pd, Initial residual = 0.0002406985, Final residual = 9.19176e-06, No Iterations 2
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (air): sum local = 4.091744e-10, global = 1.526135e-10, cumulative = 7.550246e-05
GAMG: Solving for pd, Initial residual = 0.3604305, Final residual = 0.0001962409, No Iterations 1
GAMG: Solving for pd, Initial residual = 0.0002416951, Final residual = 5.678556e-07, No Iterations 6
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors (air): sum local = 2.535464e-11, global = -8.27864e-12, cumulative = 7.550245e-05
DILUPBiCG: Solving for epsilon, Initial residual = 5.23003e-06, Final residual = 1.120886e-08, No Iterations 2
DILUPBiCG: Solving for k, Initial residual = 6.230139e-06, Final residual = 2.278377e-08, No Iterations 2

Solving for solid region ceiling
DICPCG: Solving for T, Initial residual = 5.053041e-07, Final residual = 5.053041e-07, No Iterations 0
DICPCG: Solving for T, Initial residual = 5.05303e-07, Final residual = 5.05303e-07, No Iterations 0
Min/max T:min(T) [0 0 0 1 0 0 0] 293 max(T) [0 0 0 1 0 0 0] 295.2498
ExecutionTime = 13231.56 s ClockTime = 13290 s

End