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<p>Dear Roland,</p>
<p>I see.</p>
<p>Thanks for your information.</p>
<br>
<div>Best regards,</div>
<div>Chia-Hui</div>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>寄件者:</b> Roland Haas <rhaas@illinois.edu><br>
<b>寄件日期:</b> 2018年10月11日 下午 08:32:49<br>
<b>收件者:</b> 林家暉<br>
<b>副本:</b> Einstein Toolkit Users<br>
<b>主旨:</b> Re: [Users] separation of simulation domain</font>
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<div class="PlainText">Hello Chia-Hui,<br>
<br>
> I have a question about whether it is possible to separate the domain<br>
> of the simulation. I want to simulate with a larger scale such as (1<br>
> million km )^3 , however it is too computation-consuming to simulate<br>
> the whole domain with GR and it is not necessary to consider GR<br>
> because GR could be ignored in such large scale. But in the region<br>
> near center with high density , GR is important .<br>
Right now there is no way in Cactus to only allocate memory for some<br>
variables in one region of the grid but allocate memory for all of them<br>
in other regions.<br>
<br>
> Therefore I am wondering if it is possible that GR is included in the<br>
> center region ,say (1000 km)^3, but not included in the other region.<br>
> However another problem is that timescale is also very different.<br>
> ET's time scale is about ~ ms but what I need is around hours to<br>
> days. Is there some suggestion for me to deal with it ?<br>
That will always be difficult. With mesh refinement you can add<br>
resolution in only the regions where high spatial and temporal<br>
resolution is required and because Carpet implements sub-cycling in<br>
time, in regions where only the coarse levels exist time steps forward<br>
with the coarse timesteps and not with the fine one.<br>
<br>
You could also consider using Llama to have central region with high<br>
(Cartesian) resolution and an other spherical region with lower<br>
resolution.<br>
<br>
Yours,<br>
Roland<br>
<br>
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