|
131 | 131 | <p>The classical RK4 method achieves fourth-order accuracy via four slope evaluations at intermediate points:</p> |
132 | 132 | <p>This yields a global error of order <span class="math notranslate nohighlight">\(O(\Delta t^4)\)</span> with four velocity evaluations per step.</p> |
133 | 133 | <p><strong>Sixth-Order Runge-Kutta (RK6)</strong></p> |
134 | | -<p>The seven-stage scheme <code class="docutils literal notranslate"><span class="pre">ERK6(7)</span></code> uses non-uniform weights to attain global <span class="math notranslate nohighlight">\(O(\Delta t^6)\)</span> accuracy. This method originates from <a class="reference internal" href="9_references.html#butcher" id="id1"><span>[Butcher]</span></a>. |
| 134 | +<p>The seven-stage scheme <code class="docutils literal notranslate"><span class="pre">ERK6(7)</span></code> uses non-uniform weights to attain global <span class="math notranslate nohighlight">\(O(\Delta t^6)\)</span> accuracy, originating from <a class="reference internal" href="9_references.html#butcher1964" id="id1"><span>[Butcher1964]</span></a>. |
135 | 135 | As for the coefficients for <code class="docutils literal notranslate"><span class="pre">RK6</span></code> are more complex to write into equations, the Butcher table is given as follows.</p> |
136 | 136 | <table class="docutils align-default"> |
137 | 137 | <thead> |
|
220 | 220 | </tr> |
221 | 221 | </tbody> |
222 | 222 | </table> |
223 | | -<p>In our computation, the up symbol side is applied, in other words, <code class="docutils literal notranslate"><span class="pre">±</span></code> represents <code class="docutils literal notranslate"><span class="pre">+</span></code>, taking <span class="math notranslate nohighlight">\(\lambda=+\sqrt{5}\)</span>.</p> |
| 223 | +<p>In our computation, the up symbol side is applied, in other words, <code class="docutils literal notranslate"><span class="pre">±</span></code> represents <code class="docutils literal notranslate"><span class="pre">+</span></code>, taking <span class="math notranslate nohighlight">\(\lambda=+\sqrt{5}\)</span>. With 15 digis are kept, the Butcher table used by the author is shown in the following table.</p> |
| 224 | +<table class="docutils align-default"> |
| 225 | +<thead> |
| 226 | +<tr class="row-odd"><th class="head"><p><span class="math notranslate nohighlight">\(c_i\)</span></p></th> |
| 227 | +<th class="head"><p><span class="math notranslate nohighlight">\(a_{i1}\)</span></p></th> |
| 228 | +<th class="head"><p><span class="math notranslate nohighlight">\(a_{i2}\)</span></p></th> |
| 229 | +<th class="head"><p><span class="math notranslate nohighlight">\(a_{i3}\)</span></p></th> |
| 230 | +<th class="head"><p><span class="math notranslate nohighlight">\(a_{i4}\)</span></p></th> |
| 231 | +<th class="head"><p><span class="math notranslate nohighlight">\(a_{i5}\)</span></p></th> |
| 232 | +<th class="head"><p><span class="math notranslate nohighlight">\(a_{i6}\)</span></p></th> |
| 233 | +<th class="head"><p><span class="math notranslate nohighlight">\(a_{i7}\)</span></p></th> |
| 234 | +</tr> |
| 235 | +</thead> |
| 236 | +<tbody> |
| 237 | +<tr class="row-even"><td><p>0</p></td> |
| 238 | +<td><p>0</p></td> |
| 239 | +<td><p>0</p></td> |
| 240 | +<td><p>0</p></td> |
| 241 | +<td><p>0</p></td> |
| 242 | +<td><p>0</p></td> |
| 243 | +<td><p>0</p></td> |
| 244 | +<td><p>0</p></td> |
| 245 | +</tr> |
| 246 | +<tr class="row-odd"><td><p>0.276393202250021</p></td> |
| 247 | +<td><p>0.276393202250021</p></td> |
| 248 | +<td><p>0</p></td> |
| 249 | +<td><p>0</p></td> |
| 250 | +<td><p>0</p></td> |
| 251 | +<td><p>0</p></td> |
| 252 | +<td><p>0</p></td> |
| 253 | +<td><p>0</p></td> |
| 254 | +</tr> |
| 255 | +<tr class="row-even"><td><p>0.723606797749979</p></td> |
| 256 | +<td><p>-0.223606797749979</p></td> |
| 257 | +<td><p>0.947213595499958</p></td> |
| 258 | +<td><p>0</p></td> |
| 259 | +<td><p>0</p></td> |
| 260 | +<td><p>0</p></td> |
| 261 | +<td><p>0</p></td> |
| 262 | +<td><p>0</p></td> |
| 263 | +</tr> |
| 264 | +<tr class="row-odd"><td><p>0.276393202250021</p></td> |
| 265 | +<td><p>0.0326237921249264</p></td> |
| 266 | +<td><p>0.309016994374947</p></td> |
| 267 | +<td><p>-0.0652475842498529</p></td> |
| 268 | +<td><p>0</p></td> |
| 269 | +<td><p>0</p></td> |
| 270 | +<td><p>0</p></td> |
| 271 | +<td><p>0</p></td> |
| 272 | +</tr> |
| 273 | +<tr class="row-even"><td><p>0.723606797749979</p></td> |
| 274 | +<td><p>0.0460655337083368</p></td> |
| 275 | +<td><p>0</p></td> |
| 276 | +<td><p>0.166666666666667</p></td> |
| 277 | +<td><p>0.510874597374975</p></td> |
| 278 | +<td><p>0</p></td> |
| 279 | +<td><p>0</p></td> |
| 280 | +<td><p>0</p></td> |
| 281 | +</tr> |
| 282 | +<tr class="row-odd"><td><p>0.276393202250021</p></td> |
| 283 | +<td><p>0.12060113295833</p></td> |
| 284 | +<td><p>0</p></td> |
| 285 | +<td><p>-0.181694990624912</p></td> |
| 286 | +<td><p>0.166666666666667</p></td> |
| 287 | +<td><p>0.170820393249937</p></td> |
| 288 | +<td><p>0</p></td> |
| 289 | +<td><p>0</p></td> |
| 290 | +</tr> |
| 291 | +<tr class="row-even"><td><p>1</p></td> |
| 292 | +<td><p>0.166666666666667</p></td> |
| 293 | +<td><p>0</p></td> |
| 294 | +<td><p>0.0751416197912285</p></td> |
| 295 | +<td><p>-3.38770632020821</p></td> |
| 296 | +<td><p>0.52786404500042</p></td> |
| 297 | +<td><p>3.61803398874989</p></td> |
| 298 | +<td><p>0</p></td> |
| 299 | +</tr> |
| 300 | +<tr class="row-odd"><td><p>b_i</p></td> |
| 301 | +<td><p>0.0833333333333333</p></td> |
| 302 | +<td><p>0</p></td> |
| 303 | +<td><p>0</p></td> |
| 304 | +<td><p>0</p></td> |
| 305 | +<td><p>0.416666666666667</p></td> |
| 306 | +<td><p>0.416666666666667</p></td> |
| 307 | +<td><p>0.0833333333333333</p></td> |
| 308 | +</tr> |
| 309 | +</tbody> |
| 310 | +</table> |
224 | 311 | </section> |
225 | 312 | </section> |
226 | 313 | <section id="ftle-computation"> |
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