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<p style="margin-top:0;margin-bottom:0">Dear Sijo,</p>
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<p style="margin-top:0;margin-bottom:0">In the ocyl2 case, the delta is based on a dimension that</p>
<p style="margin-top:0;margin-bottom:0">is related to the model. (Here, delta=2*D, where D=1 is</p>
<p style="margin-top:0;margin-bottom:0">the diameter of the cylinder.)</p>
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<p style="margin-top:0;margin-bottom:0">Such a choice would be reasonable for all flow past a cylinder</p>
<p style="margin-top:0;margin-bottom:0">cases for that particular geometry, independent of the mesh</p>
<p style="margin-top:0;margin-bottom:0">resolution.</p>
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<p style="margin-top:0;margin-bottom:0">The boundary-layer thickness criterion is important when there</p>
<p style="margin-top:0;margin-bottom:0">are multiple objects that are potentially touching.</p>
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<p style="margin-top:0;margin-bottom:0">Keep in mind that any of these choices are moderated by the</p>
<p style="margin-top:0;margin-bottom:0">fact that we are simply computing a blending function that is</p>
<p style="margin-top:0;margin-bottom:0">the solution to the (modified) Laplace equation. It will have</p>
<p style="margin-top:0;margin-bottom:0">more or less the correct shape --- even the unmodified Laplace</p>
<p style="margin-top:0;margin-bottom:0">solution is not a terrible blending function. The modification is</p>
<p style="margin-top:0;margin-bottom:0">designed simply to help preserve mesh sizes near boundaries.</p>
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<p style="margin-top:0;margin-bottom:0">I paste below a snippet of code that computes the average </p>
<p style="margin-top:0;margin-bottom:0">thickness of elements near the moving wall.</p>
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<p style="margin-top:0;margin-bottom:0">Paul</p>
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integer e,f</p>
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nxz = nx1*nz1</p>
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nxyz = nx1*ny1*nz1</p>
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n = nxyz*nelv</p>
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srfbl = 0. ! Surface area of elements in b.l.</p>
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volbl = 0. ! Volume of elements in boundary layer</p>
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do e=1,nelv</p>
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do f=1,nface</p>
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if (cbc(f,e,1).eq.'mv ') then</p>
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srfbl = srfbl + vlsum(area(1,1,f,e),nxz )</p>
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volbl = volbl + vlsum(bm1 (1,1,1,e),nxyz)</p>
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endif</p>
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enddo</p>
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enddo</p>
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srfbl = glsum(srfbl,1) ! Sum over all processors</p>
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volbl = glsum(volbl,1)</p>
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delta = volbl / srfbl ! Avg thickness of b.l. elements</p>
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call rone (h1,n)</p>
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call rzero(h2,n)</p>
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call cheap_dist(d,1,'mv ')</p>
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deltap = 2*delta ! Protected b.l. thickness</p>
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do i=1,n</p>
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arg = -(d(i)/deltap)**2</p>
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h1(i) = h1(i) + 9*exp(arg)</p>
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enddo</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Nek5000-users <nek5000-users-bounces@lists.mcs.anl.gov> on behalf of nek5000-users@lists.mcs.anl.gov <nek5000-users@lists.mcs.anl.gov><br>
<b>Sent:</b> Monday, November 27, 2017 7:52 AM<br>
<b>To:</b> nek5000-users<br>
<b>Subject:</b> [Nek5000-users] mesh deformation</font>
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<div>Hello Nek,</div>
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<div> I was trying to validate moving cylinder test cases (ocyl2.usr more specifically). I could validate it properly. Even though I have some doubts regarding the mesh motion. Mesh deformation more precisely. I have seen a function to send the deformation
to far field apart from the near wall region (Laplace equation with h1 as blending coefficient).So in order to find h1 in the equation there is a parameter called delta (which is 2 in this case). I have also read a paper regarding this equation. In that paper
its clearly states that it is the average thickness of the element which is close to the object. So my question is, is there anyway to calculate it automatically or easily to calculate the thickness of that particular elements from any input files? because
if I change the mesh (suppose if I refine the mesh size everything will change right?) how can I find the new average thickness of the elements which is close to the object? or how can I measure the area or volume of the elements which is close to the wall.
so could you please help me with this?</div>
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<div>Thanks with regards</div>
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<div>Sijo George</div>
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