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[sparta-users] Question about the energy distribution between translational and rotational energy
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From: 罗健 <luo...@ma...> - 2019-09-09 12:41:37
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<div><span style="line-height: 1.6;">Hello everyone,</span></div><div><br></div><div>Recently, I found something unusual when I simulated a hypersonic flow past a cylinder with SPARTA. The vibrational excitation is in included while chemical reaction is excluded in the case. What confuse me is the translational temperature Ttra, rotational temperature Trot and vibrational temperature Tvib along the stagnation streamline don't vary as I expected. Then, I run a simple test case, thermal gas in a 3d box with collisions, to check the energy transfer between these modes. The vision of SPARTA is the last one on Github, and the files, <i>air.species</i> and <i>air.vss</i>, are not modified. The input script is attached below</div><div><br></div><div>seed<span class="Apple-tab-span" style="white-space: pre;"> </span> <span class="Apple-tab-span" style="white-space: pre;"> </span> 12345</div><div>dimension <span class="Apple-tab-span" style="white-space:pre"> </span> 3</div><div>global gridcut 1.0e-5 comm/sort yes</div><div>boundary<span class="Apple-tab-span" style="white-space:pre"> </span> <span class="Apple-tab-span" style="white-space:pre"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;">rr rr rr</span></div><div>create_box <span class="Apple-tab-span" style="white-space:pre"> </span> 0 0.0001 0 0.0001 0 0.0001</div><div>create_grid <span class="Apple-tab-span" style="white-space:pre"> </span> 1 1 1</div><div>balance_grid rcb part</div><div>species<span class="Apple-tab-span" style="white-space:pre"> </span> air.species O2</div><div>mixture<span class="Apple-tab-span" style="white-space:pre"> </span> air O2 vstream 0.0 0.0 0.0 temp 300</div><div>global nrho 7.07043E22</div><div>global fnum 7.07043E6</div><div>collide <span class="Apple-tab-span" style="white-space:pre"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;">vss air air.vss relax variable</span></div><div>collide_modify<span class="Apple-tab-span" style="white-space:pre"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;">rotate yes vibrate smooth</span></div><div>create_particles air n 10000</div><div>stats<span class="Apple-tab-span" style="white-space:pre"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;">100</span></div><div>compute temp temp</div><div>stats_style<span class="Apple-tab-span" style="white-space:pre"> </span> <span class="Apple-tab-span" style="white-space:pre"> </span>step cpu np nattempt ncoll c_temp</div><div>compute <span class="Apple-tab-span" style="white-space:pre"> </span>1 grid all all trot tvib</div><div>compute<span class="Apple-tab-span" style="white-space:pre"> </span> <span class="Apple-tab-span" style="white-space:pre"> </span>therm thermal/grid all all temp</div><div>fix <span class="Apple-tab-span" style="white-space:pre"> </span> <span class="Apple-tab-span" style="white-space:pre"> </span>1 ave/grid all 1 100 100 c_therm[*] c_1[*] ave one</div><div>dump <span class="Apple-tab-span" style="white-space:pre"> </span>1 grid all 100 grid* f_1[*]</div><div>timestep <span class="Apple-tab-span" style="white-space:pre"> </span> <span class="Apple-tab-span" style="white-space:pre"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;">7.00E-9</span></div><div>run <span class="Apple-tab-span" style="white-space: pre;"> </span> <span class="Apple-tab-span" style="white-space: pre;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;"> </span><span style="line-height: 1.6;">500</span></div><div><br></div><div>The dump file shows that the temperatures (Ttra Trot Tvib) are (340.752 237.269 299.517), Ttra and Trot are not equal anymore. It seems that the energy distribution between translational and rotational mode doesn't work properly. I am wondering if my settings are incorrect or, if there is a problem with the program itself.</div><div><br></div><div>Best regards,</div></div><div>
</div><div>Jian LUO</div>
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