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Valve motion problem in two stroke combustion engine

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Old   December 23, 2019, 03:57
Default Valve motion problem in two stroke combustion engine
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Hubert
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Dear friends!

I'm writing my engineering thesis about flow in two-stroke combustion engine. I got a 3D model of my supervisors conception, it is very simple - sharp edges, simple rounds, just to see if his concept is correct and has any sense. It has two inlet valves in cylinder head and outlet "windows" revealed by piston as it moves down.

First I tried to simulate it without valves - the inlet ports were closed or opened in time, and it was acceptable simplification. But I have decided that I need to simulate it with valves, just to add more turbulent flow and mixing from valves shape.

And thats where I have a problem. I created in notepad profile of valve movement consisting of shaft angle and valve lift:

((valve_motion 361 points)
(angle 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360)

(lift 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1.22317E-05 4.8887E-05 0.000109846 0.000194911 0.000303803 0.000436167 0.000591573 0.000769512 0.000969404 0.001190599 0.001432373 0.001693938 0.001974441 0.002272968 0.002588544 0.002920141 0.003266676 0.003627019 0.003999995 0.004384387 0.004778942 0.005182373 0.005593362 0.006010572 0.006432639 0.006858187 0.00728583 0.00771417 0.008141813 0.008567361 0.008989428 0.009406638 0.009817627 0.010221058 0.010615613 0.011000005 0.011372981 0.011733324 0.012079859 0.012411456 0.012727032 0.013025559 0.013306062 0.013567627 0.013809401 0.014030596 0.014230488 0.014408427 0.014563833 0.014696197 0.014805089 0.014890154 0.014951113 0.014987768 0.015 0.014987768 0.014951113 0.014890154 0.014805089 0.014696197 0.014563833 0.014408427 0.014230488 0.014030596 0.013809401 0.013567627 0.013306062 0.013025559 0.012727032 0.012411456 0.012079859 0.011733324 0.011372981 0.011000005 0.010615613 0.010221058 0.009817627 0.009406638 0.008989428 0.008567361 0.008141813 0.00771417 0.00728583 0.006858187 0.006432639 0.006010572 0.005593362 0.005182373 0.004778942 0.004384387 0.003999995 0.003627019 0.003266676 0.002920141 0.002588544 0.002272968 0.001974441 0.001693938 0.001432373 0.001190599 0.000969404 0.000769512 0.000591573 0.000436167 0.000303803 0.000194911 0.000109846 4.8887E-05 1.22317E-05 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0))

I'm applying it into Fluent, checking if everything is working and moving, and it's ok. Then when I run calculation (in the meantime watching how the mesh moves), after about 225 degrees, when the valve is in it's return move (and creation of mesh is ok, because I am looking at it), these error shows:

"received a fatal signal (segmentation fault)
error object: #f"


Have you met with this kind of problem? I tried really everything - memory, different function, different mesh, and it is still the same error. Could it be problem with Fluent version?

Sorry for not explaining the whole concept, but it is a lot of writing to do it well
If you have any ideas about this please help me, I will appreciate very much, because I really don't know what to do with this .
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Old   December 24, 2019, 00:32
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Alexander
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AlexanderZ will become famous soon enoughAlexanderZ will become famous soon enough
basically, this error says that you are trying to access the memory, which is not allocated. May be the problem is in your profiles.
If you have same error at the same time moment for different cases (different meshes) - problem is in your settings or profile. Else it could be mesh problem

You may try to use UDF to define boundary conditions. You need DEFINE_PROFILE macro and put your data into arrays (more information in ansys fluent customization manual)
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piston engine, two-stroke, valve

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