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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Hi everyone,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">I am running an experiment to study mixing driven by internal wave breaking. I have incorporated a passive tracer into the experiment as a Gaussian patch in the area where the wave is breaking
to study the evolution of its vertical variance and infer an effective eddy diffusivity from that. I have set arbitrarily the passive tracer concentration to be between 0 (outside of the Gaussian patch) and 1 (in the center of the Gaussian patch).
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Very rapidly in the simulation, I get negative values of the passive tracer concentration outside of the Gaussian patch where it is supposed to be zero. Is there a way to avoid that? I am using
the default advection scheme right now.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Thank you,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt">Bertrand<o:p></o:p></span></p>
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