[Shogan]

Hi guys,

A quite large (huge 781ft*674ft*50ft) warehouse is under simulation. Please refer to the figure below for a general idea.

setting: steady, gravity: z direction -9.8
model: energy, viscous-Laminar
boundary:
Roof temperature: constant 303.15 k
wall upper half temperature: constant 301.15 k
wall lower half temperature: constant 293.15 k
ground temperature: constant 291.15 k

in the "Solution control", the static temperature limit was set as 290k - 305k,

The aim is to get a temperature distribution of the air inside the warehouse.
I tried different under relaxation number:
group 1(default: pressure 0.3, momentum 0.7) ----> unstable
group 2(default: pressure 0.5, momentum 0.5) ----> unstable
group 3(default: pressure 0.7, momentum 0.3) ----> unstable
group 4(default: pressure 0.9, momentum 0.1) ----> relatively good comparing with others group. So I chose group for further calculation.

However, the calculation going wrong, and quite unstable, convergence does no happen.


Any advise about what should I check and change to improve simulation are welcome!! please inspire me~~~ Thank you.
bad mesh quality? wrong model choice? or other reason?

Here is other relevant information:
Mesh info -quality :
Mesh Quality:
Orthogonal Quality ranges from 0 to 1, where values close to 0 correspond to low quality.
Minimum Orthogonal Quality = 7.29669e-02
Maximum Aspect Ratio = 4.29217e+01




http://imgout.ph.126.net/27510046/5.jpg

[Shogan]

the last time I check the calculation: it shown:
7266 1.6541e+00 3.6002e-02 3.0408e-02 4.5353e+00 3.8074e-03 -1.4547e+00 -5.0413e-01 2.3152e-01 2.1346e+00 8.4543e+05 2.7000e+02 2.7000e+02 2.7000e+02 2.7000e+02 2.7000e+02 2.7000e+02 2:04:52 2734
temperature limited to 3.300000e+02 in 471575 cells on zone 4 in domain 1
temperature limited to 3.300000e+02 in 1684873 cells on zone 5 in domain 1
temperature limited to 3.300000e+02 in 17890 cells on zone 6 in domain 1

Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature





Meanwhile, I also try "k-epsilon model " with fully bouncy effect. The other setting are the same, however, the result turn out :
iter continuity x-velocity y-velocity z-velocity energy k epsilon fan1 fan2 fan3 fan4 x407planeint x407planemas x407planeare point1areawe point2areawe point3areawe point4areawe t
ime/iter
10049 4.2943e-01 1.8292e-02 2.0100e-02 3.6592e-01 6.1221e-05 9.0529e-03 1.0361e-02 2.3372e-01 1.9888e-02 -2.6312e-03 9.6392e-02 9.2493e+05 2.9653e+02 2.9539e+02 3.0340e+02 2.9086e+02 2.9059e+02 2.9757e+02 0:00:03 1
temperature limited to 2.900000e+02 in 6 cells on zone 4 in domain 1
temperature limited to 2.900000e+02 in 11055 cells on zone 5 in domain 1

turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 1 cells
10050 4.1905e-01 1.8670e-02 1.9900e-02 3.6310e-01 5.2695e-05 8.0936e-03 1.0017e-02 3.4978e-01 1.1507e-01 4.4124e-02 1.0427e-01 9.3864e+05 2.9927e+02 2.9977e+02 2.9056e+02 3.0284e+02 3.0258e+02 2.9819e+02 0:00:00 0

[Bionico]

Hello Shogan,
I suggest using RNG-k-epsilon as turbulence model and Boussinesq model for air density in Material properties menu.
Anyway it's always difficult to reach a convergence in closed domain with Natural convection (you can also do a transient simulation, very good in such a case, but you have to take into account the computational cost)

Regards

[Shogan]

Originally Posted by Bionico

Hello Shogan,
I suggest using RNG-k-epsilon as turbulence model and Boussinesq model for air density in Material properties menu.
Anyway it's always difficult to reach a convergence in closed domain with Natural convection (you can also do a transient simulation, very good in such a case, but you have to take into account the computational cost)

Regards

Hi Bionico,

With you guidance, The simulation finally converged!! Thank you very much!!
I will discuss the result with my supervisor and see what go out.

By the way, Italy is amazing especially Florence ! I've been there and still feel not enough of it.

---Shogan

[Bionico]

Hi Shogan,
I'm happy to see that my advice was good!
If you have any other problem don't hesitate to tell me (I often do Natural convection simulation in closed domain)!

Best Regards

PS: You're always welcome in Italy!