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Hi, Peter,</div>
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Thanks for your suggestions, which are quite helpful. </div>
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I was using the independent "Dissipation" thorn</div>
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Dissipation::epsdis = 0.1
<div>Dissipation::order = 5</div>
<div>Dissipation::vars = "</div>
<div> ML_CCZ4::ML_log_confac</div>
<div> ML_CCZ4::ML_metric</div>
<div> ML_CCZ4::ML_trace_curv</div>
<div> ML_CCZ4::ML_curv</div>
<div> ML_CCZ4::ML_Gamma</div>
<div> ML_CCZ4::ML_lapse</div>
<div> ML_CCZ4::ML_shift</div>
<div> ML_CCZ4::ML_dtlapse</div>
<div> ML_CCZ4::ML_dtshift</div>
"<br>
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for RK4, which turned out to be not enough dissipation for damping out the high frequency oscillation of the constrain violation.</div>
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Then I turned on the dissipation of ML_CCZ4::epsdiss = 0.1, It worked, no more large violation near refinement boundaries. <br>
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However, not very sure about how these two "<span style="background-color:rgb(255, 255, 255);display:inline !important">epsdis</span>" work differently. </div>
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BR</div>
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KZ</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Peter Diener <diener@cct.lsu.edu><br>
<b>Sent:</b> Thursday, July 8, 2021 10:47 PM<br>
<b>To:</b> CHEN, Kenneth <kchen@link.cuhk.edu.hk><br>
<b>Cc:</b> users@einsteintoolkit.org <users@einsteintoolkit.org><br>
<b>Subject:</b> Re: [Users] Unexpected Hamiltonian constraint violation from refinement when using CCZ4</font>
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<div class="PlainText">Hi Kenneth,<br>
<br>
It is expected that the mesh refinement boundaries will reflect <br>
Hamiltonian constraint violations. From what you have provided us, it is <br>
not clear whether the level of constraint violations that you see is a <br>
cause of concern. You specifically mention CCZ4, but have you tried with <br>
BSSN? Does the constraint violations look better, the same, or worse with <br>
BSSN?<br>
<br>
It is also possible that an issue like this might be caused by some other <br>
problem potentially related to parameter settings, so in order to <br>
investigate this can you provide your thornlist and parameter file?<br>
<br>
Cheers,<br>
<br>
Peter<br>
<br>
On Sun, 4 Jul 2021, CHEN, Kenneth wrote:<br>
<br>
> While using CCZ4 to simulate a single star, the Hamiltonian constraint<br>
> violation initially came from the star surface as expected, but after some<br>
> time, the violation was dominated by areas near corners of refinement levels<br>
> (by Carpet) as shown in following figures, which were strange. Any<br>
> suggestions?<br>
> <br>
> Thanks and regards,<br>
> KZ<br>
> <br>
> <br>
> <br>
> <br>
> [IMAGE]<br>
> [IMAGE]<br>
> [IMAGE]<br>
> [IMAGE]<br>
> <br>
> <br>
> <br>
><br>
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