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Navier-Stokes Solver
Posted: 24 Jun 2015, 14:43
by hamed
Dear Elmer group
Hi
I’m working on a very simple axisymmetric model of tube with Navier-Stokes Solver.
I apply pressure=5000 pa in the inlet and pressure=0 pa in the outlet.
While the case seems really simple, it does not converge. Can you please help me solve this problem?
Thanks, Hamed
Re: Navier-Stokes Solver
Posted: 24 Jun 2015, 15:24
by mzenker
Hi Hamed,
I cannot help personally since I have never used the NS solver. But I think you should post your case here (mesh and sif files) in order to enable others with NS knowledge to have a look at it.
Matthias
Re: Navier-Stokes Solver
Posted: 24 Jun 2015, 15:58
by hamed
Hi Matthias
Here is the test case.
Thanks for your help, Hamed
Re: Navier-Stokes Solver
Posted: 25 Jun 2015, 15:06
by dmitry
Hi Hamed!
Thetr was no second velosity component given for inlet.
See code below
Code: Select all
Header
Mesh DB "." "TubeMesh"
End
Constants
End
Simulation
Coordinate System = Axi Symmetric
Simulation Type = Steady State
Steady State Max Iterations = 50
Steady State Min Iterations = 2
Output Intervals = 1
Post File = "Stenosis.ep"
End
Body 1
Equation = 1
Material = 1
End
Material 1
Density = 1000.0
Viscosity = 0.004
End
Solver 1
Equation = Navier-Stokes
Stabilize = True
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStabl
Linear System Preconditioning = ILU1
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e-8
Nonlinear System Max Iterations = 10
Nonlinear System Convergence Tolerance = 1.0e-5
Nonlinear System Newton After Tolerance = 1.0e-5
Nonlinear System Newton After Iterations = 20
Nonlinear System Relaxation Factor = 0.7
Steady State Convergence Tolerance = 1.0e-4
End
Equation 1
Active Solvers(1) = 1
End
! inlet
Boundary Condition 1
Target Boundaries = 1
Velocity 1 = 0
Velocity 2 = 1
Pressure = 5000.0
End
! outlet
Boundary Condition 2
Target Boundaries = 3
Velocity 1 = 0.0
Pressure = 0.0
End
! symmetriy
Boundary Condition 3
Target Boundaries = 4
Velocity 1 = 0.0
End
! Wall
Boundary Condition 4
Target Boundaries = 2
Velocity 1 = 0.0
Velocity 2 = 0.0
End
Re: Navier-Stokes Solver
Posted: 26 Jun 2015, 23:30
by hamed
Hi dmitry
Thanks for your comment. But the inlet velocity is not 1 or anything else prescribed. It's actually a part of solution.
I hope Peter read this post and help me.
Thanks, Hamed
Re: Navier-Stokes Solver
Posted: 27 Jun 2015, 16:47
by annier
Hi Hamed,
I cannot open the attached .rar file in my Ubuntu 14.04 desktop. can you attach it in .gz version (so that it would be convenient for your targeted commenters)?
I am thankful to Dmitry for making the SIF file available on behalf of Hamed. Cheers.
Yours Sincerely,
Anil Kunwar
Re: Navier-Stokes Solver
Posted: 28 Jun 2015, 13:35
by hamed
Hi Anil
Thanks for your kind attention.
I attached the .tgz file.
Best regards, Hamed
Re: Navier-Stokes Solver
Posted: 28 Jun 2015, 16:32
by annier
Hi Hamed,
Your convergence issue is defined as:
Code: Select all
IterSolver: Using iterative method: bicgstab
CRS_IncompleteLU: ILU(1) (Real), Starting Factorization:
CRS_IncompleteLU: ILU(1) (Real), NOF nonzeros: 81226
CRS_IncompleteLU: ILU(1) (Real), filling (%) : 137
CRS_IncompleteLU: ILU(1) (Real), Factorization ready at (s): 0.00
1 0.1124E+05
2 0.7514E+04
3 0.5889E+04
4 0.1708E+05
5 0.3866E+04
6 0.2429E+04
7 0.2580E+04
8 0.2275E+04
9 0.3035E+04
10 0.1031E+06
11 0.2049E+04
12 0.1822E+04
13 0.2328E+04
14 0.1327E+04
15 0.1211E+04
16 0.1222E+04
17 0.1139E+04
18 0.1130E+04
19 0.1147E+04
20 0.1106E+04
21 0.1089E+04
22 0.1182E+04
23 0.1358E+04
24 0.1402E+04
25 0.1570E+04
26 0.1381E+04
27 0.1409E+04
28 0.6168E+03
29 0.5025E+03
30 0.2913E+03
31 0.3302E+03
32 0.1333E+03
33 0.1059E+03
34 0.1962E+03
35 0.8856E+02
36 0.8878E+02
37 0.9958E+02
38 0.9659E+02
39 0.3875E+02
40 0.3510E+03
41 0.3105E+03
42 0.3118E+03
43 0.3135E+03
44 0.2634E+03
45 0.7139E+02
46 0.6194E+02
47 0.6374E+02
48 0.1161E+03
49 0.5760E+01
50 0.5687E+01
51 0.1241E+01
52 0.1185E+01
53 0.1287E+01
54 0.9660E-01
55 0.1075E+00
56 0.5053E-01
57 0.3380E-01
58 0.2505E-01
59 0.2436E-01
60 0.2422E-01
61 0.1878E-01
62 0.1883E-01
63 0.1655E+00
64 0.4446E-01
65 0.1493E-02
66 0.1373E-02
67 0.1298E-02
68 0.1621E-02
69 0.1719E-02
70 0.4436E-03
71 0.5970E-03
72 0.8140E-03
73 0.1712E-03
74 0.1372E-04
75 0.2752E-04
76 0.2608E-04
77 0.2598E-04
78 0.3635E-03
79 0.3873E-04
80 0.3631E-04
81 0.9381E-04
82 0.7828E-04
83 0.1010E-03
84 0.9913E-04
85 0.9599E-04
86 0.1026E-03
87 0.3557E-04
88 0.3782E-04
89 0.4027E-04
90 0.3586E-03
91 0.8586E-05
92 0.8552E-05
93 0.7416E-05
94 0.6277E-05
95 0.1689E-05
96 0.1410E-05
97 0.1916E-05
98 0.1727E-05
99 0.1453E-05
100 0.1964E-05
101 0.1968E-05
102 0.1677E-05
103 0.3624E-06
104 0.3147E-06
105 0.3398E-06
106 0.3393E-06
107 0.3394E-06
108 0.3979E-06
109 0.3284E-06
110 0.3265E-06
111 0.2866E-06
112 0.2866E-06
113 0.2835E-06
114 0.2844E-06
115 0.2838E-06
116 0.2838E-06
117 0.2838E-06
118 0.2838E-06
119 0.2838E-06
120 0.2838E-06
121 0.2838E-06
122 0.2838E-06
123 0.2838E-06
124 0.2838E-06
125 0.2838E-06
126 0.2838E-06
127 0.2838E-06
128 0.2838E-06
129 0.2838E-06
130 0.2838E-06
131 0.2838E-06
132 0.2838E-06
133 0.2838E-06
134 0.2838E-06
135 0.2838E-06
136 0.2838E-06
137 0.2838E-06
138 0.2838E-06
139 0.2838E-06
140 0.2838E-06
141 0.2838E-06
142 0.2838E-06
143 0.2838E-06
144 0.2838E-06
145 0.2838E-06
146 0.2838E-06
147 0.2838E-06
148 0.2838E-06
149 0.2838E-06
150 0.2838E-06
151 0.2838E-06
152 0.2838E-06
153 0.2838E-06
154 0.2838E-06
155 0.2838E-06
156 0.2838E-06
157 0.2838E-06
158 0.2838E-06
159 0.2838E-06
160 0.2838E-06
161 0.2838E-06
162 0.2838E-06
163 0.2838E-06
164 0.2838E-06
165 0.2838E-06
166 0.2838E-06
167 0.2838E-06
168 0.2838E-06
169 0.2838E-06
170 0.2838E-06
171 0.2838E-06
172 0.2838E-06
173 0.2838E-06
174 0.2838E-06
175 0.2838E-06
176 0.2838E-06
177 0.2838E-06
178 0.2838E-06
179 0.2838E-06
180 0.2838E-06
181 0.2838E-06
182 0.2838E-06
183 0.2838E-06
184 0.2838E-06
185 0.2838E-06
186 0.2838E-06
187 0.2838E-06
188 0.2838E-06
189 0.2838E-06
190 0.2838E-06
191 0.2838E-06
192 0.2838E-06
193 0.2838E-06
194 0.2838E-06
195 0.2838E-06
196 0.2838E-06
197 0.2838E-06
198 0.2838E-06
199 0.2838E-06
200 0.2838E-06
201 0.2838E-06
202 0.2838E-06
203 0.2838E-06
204 0.2838E-06
205 0.2838E-06
206 0.2838E-06
207 0.2838E-06
208 0.2838E-06
209 0.2838E-06
210 0.2838E-06
211 0.2838E-06
212 0.2838E-06
213 0.2838E-06
214 0.2838E-06
215 0.2838E-06
216 0.2838E-06
217 0.2838E-06
218 0.2838E-06
219 0.2838E-06
220 0.2838E-06
221 0.2838E-06
222 0.2838E-06
223 0.2838E-06
224 0.2838E-06
225 0.2838E-06
226 0.2838E-06
227 0.2838E-06
228 0.2838E-06
229 0.2838E-06
230 0.2838E-06
231 0.2838E-06
232 0.2838E-06
233 0.2838E-06
234 0.2838E-06
235 0.2838E-06
236 0.2838E-06
237 0.2838E-06
238 0.2838E-06
239 0.2838E-06
240 0.2838E-06
241 0.2838E-06
242 0.2838E-06
243 0.2838E-06
244 0.2838E-06
245 0.2838E-06
246 0.2838E-06
247 0.2838E-06
248 0.2838E-06
249 0.2838E-06
250 0.2838E-06
251 0.2838E-06
252 0.2838E-06
253 0.2838E-06
254 0.2838E-06
255 0.2838E-06
256 0.2838E-06
257 0.2838E-06
258 0.2838E-06
259 0.2838E-06
260 0.2838E-06
261 0.2838E-06
262 0.2838E-06
263 0.2838E-06
264 0.2838E-06
265 0.2838E-06
266 0.2838E-06
267 0.2838E-06
268 0.2838E-06
269 0.2838E-06
270 0.2953E-38
ERROR:: IterSolve: Failed convergence tolerances.
Observation:
i.) Your linear system convergence tolerance setting is 1.0e-8.
ii.)The solver failed to converge in the 270th iteration, when the tolerance jumped from 1.0e-6 (within tolerance) to 1.0e-38 (far smaller tolerance width than the set 1.0e-8).
I express herein my rough guesses:
1. Try changing Linear System Preconditioning tools from ILU1 to others.
2. What is the fineness of your axisymmetric meshes?
For more information, you can view the following posts:
viewtopic.php?f=3&t=3920&p=13729&hilit= ... 5be#p13729
viewtopic.php?f=3&t=3372&p=13061&hilit= ... 5be#p13061
Yours Sincerely
Anil Kunwar
Re: Navier-Stokes Solver
Posted: 28 Jun 2015, 16:45
by annier
Hi Hamed,
1. I changed the keyword "Pressure" in BCs to the keyword "External Pressure" in your solver input file and the solver converged.
Code: Select all
!Inlet
Boundary Condition 1
...
External Pressure = -1.01e5
...
Code: Select all
!Outlet
Boundary Condition 2
...
External Pressure = -1.0e5
...
Results
- pressure distribution for external pressure
- External_Pressure_P_Result.jpg (40.6 KiB) Viewed 7338 times
- veclocity distribution for external pressure
- External_Pressure_v_result.jpg (36.51 KiB) Viewed 7338 times
Yours Sincerely
Anil Kunwar
Re: Navier-Stokes Solver
Posted: 28 Jun 2015, 17:04
by annier
Hi Hamed,
2. I applied Pressure (force) boundary conditions in BCs as:
Code: Select all
! inlet
Boundary Condition 1
Target Boundaries = 1
...
Pressure 1 = 30.0
Pressure 2 = 40.0
...
End
Code: Select all
! outlet
Boundary Condition 2
Target Boundaries = 3
...
Pressure 1 = 0
Pressure 2 = 0
...
End
And, then it converged.
The results are as following:
- Pressure Result
- pressure.jpg (37.96 KiB) Viewed 7338 times
- velocity result
- velocity.jpg (36.62 KiB) Viewed 7338 times
Please Note that:
Elmer_Models_Manual wrote:Boundary Condition bc id
...
External Pressure Real
An external pressure boundary condition directed normal to the surface.
...
Pressure i Real
A pressure force in the given direction i= 1,2,3 (It has a unit of Newtons/m^2.
In Elmer, Force at boundary condition has the unit of N/m^2)
...
Yours Sincerely
Anil Kunwar