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<tt>In the spirit of getting things right, it is Lewy and not Levy.
<span class="moz-smiley-s3"><span>;-)</span></span><br>
<br>
<a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Courant%E2%80%93Friedrichs%E2%80%93Lewy_condition">https://en.wikipedia.org/wiki/Courant%E2%80%93Friedrichs%E2%80%93Lewy_condition</a><br>
<br>
Tomek<br>
--</tt><br>
<div class="moz-cite-prefix">On 05/23/17 00:01, Suoqing Ji wrote:<br>
</div>
<blockquote cite="mid:599101e7-d05e-4a34-acd9-c3a95045aa48@Spark"
type="cite">
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<div name="messageBodySection" style="font-size: 14px;
font-family: -apple-system, BlinkMacSystemFont, sans-serif;">Hi
Siyi,
<div><br>
</div>
<div>I can provide you a quick one, and others might have more
comprehensive answers.</div>
<div><br>
</div>
<div>The time step is determined at each step by the subroutine
Driver_computeDt, which computes the timestep required by all
of the units used, and take the minimum dt over different
units. Say, Hydro_computeDt gives dt1 for hydro unit, and
Particles_computeDt gives dt2 for particle unit and so on,
then final dt = min(dt1, dt2, …)</div>
<div><br>
</div>
<div>How dt is computed for each unit varies. As a classical
example, the timestep for hydro obeys
the Courant-Friedrichs-Levy condition. Physical quantities in
each cell corresponds to a certain value of dt under this
condition, and Hydro_computeDt computes dt for each cell,
selects the minimum dt over the entire domain, and return it
to Driver_computeDt.</div>
<div><br>
</div>
<div>Hope this helps!</div>
</div>
<div name="messageSignatureSection" style="font-size: 14px;
font-family: -apple-system, BlinkMacSystemFont, sans-serif;"><br>
Best wishes,
<div>—</div>
<div>Suoqing Ji</div>
<div>Ph.D Candidate</div>
<div>Department of Physics</div>
<div>University of California, Santa Barbara</div>
<div><a moz-do-not-send="true"
href="http://physics.ucsb.edu/%7Esuoqing">http://physics.ucsb.edu/~suoqing</a></div>
</div>
<div name="messageReplySection" style="font-size: 14px;
font-family: -apple-system, BlinkMacSystemFont, sans-serif;"><br>
On May 22, 2017, 7:50 PM -0700, Siyi Yu <a class="moz-txt-link-rfc2396E" href="mailto:siyiyu@lbl.gov"><siyiyu@lbl.gov></a>,
wrote:<br>
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<div>Dear Flash users and developers,<br>
</div>
Permit-me to ask a little question about the simulation
delta t. How the system defines the time interval it
takes? When I launch a simulation, it appears that delta
t is not a constant and decrease as the simulation goes
on. Could I know why please?<br>
</div>
Best<br>
</div>
Siyi YU<br>
</div>
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