<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">Hi Yangxin<div><br></div><div>If the time constant is 0 then the sponge is not a sponge, its like setting the boundary value, and your non-compliant signal will reflect back into the domain from the edge of the sponge</div><div><br></div><div>If the time constant is infinite, then the sponge has no effect, and your non-compliant signal will reflect from the boundary. </div><div><br></div><div>The best effect is to set the inner to something large and the outer to something smaller and to make the sponge region a good fraction of a mode-1 wavelength.</div><div><br></div><div>Cheers, Jody</div><div><br></div><div><br><div id="AppleMailSignature">Sent from my iPad</div><div><br>On Nov 10, 2017, at 9:39 AM, Yangxin He <<a href="mailto:y67he@uwaterloo.ca">y67he@uwaterloo.ca</a>> wrote:<br><br></div><blockquote type="cite"><div>
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<p>Hi,</p>
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<p>I am not sure if my questions are related with the coding stuff, but I guess I can give it a try. In the OBCS sponge layer, I need to set 4 time scales as the following,<span style="color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, 'Segoe UI', 'Segoe WP', Tahoma, Arial, sans-serif; font-size: 13.333333015441895px;"></span></p>
<pre>"&OBCS_PARM03
Urelaxobcsinner=864000.E0,
Urelaxobcsbound=43200.E0,
Vrelaxobcsinner=864000.E0,
Vrelaxobcsbound=43200.E0,"</pre>
<pre>I have read the "obcs_sponge.F" code, and see how these parameters fit in the sponge forcing. But I am still a bit confused.</pre>
<pre>Then I looked through MITgcm archives and Matthew suggested these numbers in one correspondence back in 2011. My question is, how and why did he set these values? For example, if I set <span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">Urelaxobcsinner=5000.E0, why it is not good? </span><span style="font-size: 12pt; font-family: Calibri, Arial, Helvetica, sans-serif;">Is there any </span><span style="font-size: 12pt; font-family: Calibri, Arial, Helvetica, sans-serif;">numerical/theoretical </span><span style="font-size: 12pt; font-family: Calibri, Arial, Helvetica, sans-serif;">reason behind it?</span></pre>
<pre>By the way, I am modeling internal waves in the ocean, if its helpful.</pre>
<pre>Thanks a lot.</pre>
<pre>Yangxin</pre>
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