{"id":293664,"date":"2023-07-18T15:58:29","date_gmt":"2023-07-18T15:58:29","guid":{"rendered":"\/forum\/forums\/reply\/293664\/"},"modified":"2023-07-18T15:58:29","modified_gmt":"2023-07-18T15:58:29","slug":"293664","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/293664\/","title":{"rendered":"Reply To: ALE elements &#8220;sticking&#8221; to rigid plate."},"content":{"rendered":"<p>&lt;p&gt;Hi Caleb,&lt;\/p&gt;&lt;p&gt;If the boundary is symmetrical on all sides, then this looks wrong.&lt;\/p&gt;&lt;p&gt;Check:&lt;\/p&gt;<\/p>\n<ul>\n<li>mat data<\/li>\n<li>BC&#8217;s &amp; IC&#8217;s (boundary, initial conditions)<\/li>\n<\/ul>\n<p>&lt;p&gt;Then check the interaction (or coupling).&nbsp;&lt;\/p&gt;&lt;p&gt;You may want to follow the following coupling tips.&lt;\/p&gt;&lt;p&gt;Hope this helps,&lt;\/p&gt;&lt;p&gt;Ian Do&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;$===============================================================================&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;$ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;TIPS ON LEAKAGE CONTROL &#8230; COUPLING TIPS \/ CHECKLIST&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;$===============================================================================&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 0] PLEASE! Always work with a cleanly and clearly formatted deck with well&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;organized KW input structured in a way that facilitates easy reading and&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;understanding of the model ==&gt; so much FASTER and EASIER to debug and&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;document your work.&nbsp;&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;(read it into LSPREPOST + SAVE KEYWORD + &#8220;ADVANCED&#8221; ==&gt; a little manual&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp; editing ==&gt; &nbsp;all would take but less than 10 minutes)&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;Though optional &#8211; this is highly recommended habit. It also helps us help&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;you much more efficiently when we need to help you review your model.&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;We will appreciate the efforts very much!&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 1] PLEASE DELETE ALL &nbsp;&#8220;not ABSOLUTELY required&#8221; cards.&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;In general, starting values for most parameters are best left as default.&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;Only intentionally change each when you know exactly what each change does.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 2] All mat data should be as accurate as possible&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;*** Important*** input BC&#8217;s and IC&#8217;s should be reasonable&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; and make physical sense.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 3] ALWAYS check initial thermodynamic state condition,i.e. *EOS_ def.&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;for each material, to make sure each is defined properly and gives&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;the desired condition at t=0.&nbsp;&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[**] FREQUENTLY USED (and typically best) FSI SETTINGS &#8230;&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;NQUAD = at least 2 coupling points per ALE elm. NOTE: NQUAD is distributed over&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp; &nbsp; each Lagr. elm surface. So this depends on relative Lagr-ALE meshes&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp; &nbsp; resolutions. Excessive NQUAD gives stiff response and instability.&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;CTYPE = 4 (in most cases), only use 5 when Lagr. solid parts may erode&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;DIREC = 2 (in most cases. for some special sloshing coupling:&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;DIREC=1 may be used). DIREC=3 is rarely appropriate!&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;MCOUP = -I = negative integer always (see manual for example &amp; note 5)&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;PFAC &nbsp;= load curve &lt;== tuning this is the key to FSI *** most important ***&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;PLEAK = DO NOT CHANGE from default value of 0.1&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;SALE uses *ALE_STRUCTURED_FSI:&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;Some of the ALE parameters above are now handled automatically inside SALE.&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;So there are less to be concerned about.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 4] Always try to have distinct AMMG IDs on either side of a shell surface.&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;Example, even if there is water on both sides of a shell, it is better&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;to define each side with a distinct AMMG ID. Then couple each side of&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;the shell to each of the AMMG ID. Make sure the NORM parameter is&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;defined properly in CLIS card.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;If couple to a solid structure, at least have the AMMG &#8220;in front of&#8221;&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;the solid LAG part impacting surface to be different from that behind&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;that surface &#8211; then couple specifically this AMMG to the LAG part.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 5] Always couple to a specific AMMG (ale multi-mat group) that is hitting&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;on one side of the Lagr. shell.&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;MCOUP = -INTEGER &nbsp;(see manual). Create dummy parts\/AMMGs if you need to.&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;See manual for example. You&#8217;ll need to define&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;SET_MULTI-MATERIAL_GROUP_LIST..&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 6] All the normals on a shell must point uniformly in the same direction,&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;preferrably toward the AMMG it couples to.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 7] To use penalty coupling, the user should provide at least a 3 or 4-elm&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;layer of ALE domain beyond the Lagrangian shell part\/surface. For&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;example, to model a tank sloshing, the ALE domain should extend OUTSIDE&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;the Lagrangian shell tank. This is to provide the ALE space for the&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;AMMGs to flow into and the fluid penetration amount across the shell&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;be computed. The shell cannot be located flushed on the free surface of&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;the ALE mesh.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 8] The first 4 parameters on the 1st lines (slave,master,sstyp,mstyp)&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;only tell the code where CONSTRAINED_LAGRANGE_IN_SOLID lcan ook for&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;Lagr mesh to ALE mesh overlap. Where those 2 domains overlap,&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;there is a possibility of FSI. This is strictly for geometrical search.&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;It does not tell the code which AMMG (or physical &#8220;fluid&#8221;) is to&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;be coupled to the shell. MCOUP must be defined to specify which&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;AMMG to be coupled to ==&gt; next.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[ 9] Relative resolutions between Lagr and ALE meshes must be as close to 1:1&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;as possible &nbsp;The meshes should be smooth and regular (uniform) with good&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;aspect ratios. Many times leakage occurs due to bad meshes. Sharp corners&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;of a LAG container, for example, can leak more easily because there are 2&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;(2D) or 3 (for 3D) LAG surfaces residing in 1 single ALE solid elm ==&gt;&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;there is only 1 plane fluid (AMMG) interface in that elm ==&gt; tougher&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;for coupling logics to handle. If possible, smooth out cornners.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[10] Make sure there are coupling points in each ALE elm (see remark on NQUAD)&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[11] Always try to use PFAC=load curve if the default 0.1 leaks (see manual) or&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;HOW TO CONSTRUCT PFAC LOAD CURVE:&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;- x-axis = penetration amount, y-axis = maximum estimated coupling pressure&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;- point 1: [0.0, 0.0] ==&gt; reads &#8220;no penetration, apply no P&#8221;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;- point 2:&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; x2 ~ estimated as 0.1*min_ALE_elm_width&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; To estimate y2: &nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;- &nbsp; &nbsp;run the model with PFAC=0.1=default ==&gt;&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;- &nbsp; &nbsp;select only the ALE mesh\/domain and plot up P contours.&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;- &nbsp; &nbsp;pick the highest P in the ALE domain &nbsp;(maybe we can try to pick value near the most intense FSI region).&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[12] If fine tuning PFAC is not enough to stop leakage ==&gt; try ILEAK=2&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[13] Check TSSF &#8211; perhaps it can be reduced (to 0.6 and less if necessary)&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[14] When all else fails, go back to simple model to perform conceptual test.&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;For example, instead of modeling the shuttle impacting water, model a&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;simple plate hitting water at about the same speed to get a feel for the&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;pressure, etc.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[15] It is better to couple to deformable LAG parts. Coupling to rigid LAG&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; &nbsp;parts sometimes does not work as well.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;GENERAL ALE OBSERVATIONS:&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;~~~~~~~~~~~~~~~~~~~~~~~~~&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;(a) In general ==&gt; DO NOT use mass scaling with ALE! If you do use it, you must&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; know how the model behaves in details.&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;(b) DO NOT use PRIT=1 (under *CONTROL_ALE) ==&gt; it is not as robust as the&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; default approach.&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;(c) Using air instead of vacuum tends to be more stable due to the 1 atm&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;&nbsp; &nbsp; PREF in air.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;$===============================================================================&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&nbsp;&lt;\/p&gt;&lt;p&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;$===============================================================================&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[MCOUP=0]&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;This means the code tries to couple to all ALE fluids (all AMMGs). This means&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;there may not be a more precise fluid interface with respect to which the code&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;tracks for penetration of the fluid. It can only try to track the relative&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;displacements between the ALE nodes and LAG nodes. The results may not be as&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;precise. Consider the case where you have air on both sides of a flag. If you&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;define the same AMMGID for the air surrounding the flag and MCOUP=0, then the&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;coupling force can still be estimated based on the relative displacements of the&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;ALE nodes VS. LAG nodes.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;[MCOUP=-123 &#8230;]&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;Now if you define 2 distinct AMMGIDs for the same physical air, at t=0, say,&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;AMMGID=1 on 1 side of the flag (a shell part), and AMMGID=2 on the other side.&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;Assume further that your shell part normals ALL point uniformly toward AMMGID=1.&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;Then you can now define 2 coupling cards (CLIS), 1 to couple to each of the&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;AMMGID on each of the shell surfaces.&lt;\/span&gt;&lt;\/p&gt;&lt;p&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;That summarizes the differences between the 2 MCOUP approaches. So you may find&nbsp;&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;their results to be different, and that is due to these fine points.&lt;\/span&gt;&lt;br&gt;&lt;span style=&#8221;font-size: 12pt;&#8221;&gt;$===============================================================================&lt;\/span&gt;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-293664","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Hi Caleb,If the boundary is symmetrical on all sides, then this looks wrong.Check:mat dataBC&#039;s &amp; IC&#039;s (boundary, initial conditions)Then check the interaction (or coupling). You may want to follow the following coupling tips.Hope this helps,Ian Do $===============================================================================$ TIPS ON LEAKAGE CONTROL ... 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You may want to follow the following coupling tips.Hope this helps,Ian Do $===============================================================================$ TIPS ON LEAKAGE CONTROL ... COUPLING TIPS \/\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/293664\/\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2023-07-18T15:58:29+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2023-07-18T15:58:29+00:00\" \/>\n\t\t<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n\t\t<meta name=\"twitter:title\" content=\"Reply To: ALE elements \u201csticking\u201d to rigid plate. | Ansys Learning Forum\" \/>\n\t\t<meta name=\"twitter:description\" content=\"Hi Caleb,If the boundary is symmetrical on all sides, then this looks wrong.Check:mat dataBC&#039;s &amp; IC&#039;s (boundary, initial conditions)Then check the interaction (or coupling). You may want to follow the following coupling tips.Hope this helps,Ian Do $===============================================================================$ TIPS ON LEAKAGE CONTROL ... 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You may want to follow the following coupling tips.Hope this helps,Ian Do $===============================================================================$ TIPS ON LEAKAGE CONTROL ... 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You may want to follow the following coupling tips.Hope this helps,Ian Do $===============================================================================$ TIPS ON LEAKAGE CONTROL ... 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You may want to follow the following coupling tips.Hope this helps,Ian Do $===============================================================================$ TIPS ON LEAKAGE CONTROL ... 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You may want to follow the following coupling tips.Hope this helps,Ian Do $===============================================================================$ TIPS ON LEAKAGE CONTROL ... COUPLING TIPS \/","og:url":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/293664\/","article:published_time":"2023-07-18T15:58:29+00:00","article:modified_time":"2023-07-18T15:58:29+00:00","twitter:card":"summary_large_image","twitter:title":"Reply To: ALE elements \u201csticking\u201d to rigid plate. | Ansys Learning Forum","twitter:description":"Hi Caleb,If the boundary is symmetrical on all sides, then this looks wrong.Check:mat dataBC's &amp; IC's (boundary, initial conditions)Then check the interaction (or coupling). You may want to follow the following coupling tips.Hope this helps,Ian Do $===============================================================================$ TIPS ON LEAKAGE CONTROL ... 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