


{"id":463100,"date":"2026-08-31T09:27:22","date_gmt":"2026-08-31T09:27:22","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/mesh-replacement-causes-cdr-error-in-droplet-vof-simulation\/"},"modified":"2026-08-31T09:27:22","modified_gmt":"2026-08-31T09:27:22","slug":"mesh-replacement-causes-cdr-error-in-droplet-vof-simulation","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/mesh-replacement-causes-cdr-error-in-droplet-vof-simulation\/","title":{"rendered":"Mesh replacement causes CDR error in droplet VOF simulation"},"content":{"rendered":"<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">Hi,<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">I am modelling water droplets falling in air to reach their terminal velocity using a VOF multiphase model. I received the results I was expecting once, and I am now trying to swap out my current mesh for a different mesh to change the droplet size and mesh refinement.<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">When I try to read in a new mesh file, it reads successfully &#8211; however, the following error message is displayed, and the simulation does not run as expected afterward (pressure field becomes unstable, droplet moves in the opposite direction to expected):<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">&nbsp;<\/p>\n<p style=\"margin: 0in;font-family: &#039;var(--font-mono)&#039;;font-size: 11.0pt;color: #14181f\"><span style=\"color: #ffffff\">Error: CDR: invalid argument [1]: wrong type [not a pair]<\/span><br \/><span style=\"color: #ffffff\">Error Object: #f<\/span><\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">&nbsp;<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">This occurs right after the mesh finishes building and Fluent replays the case settings onto the new mesh (zone matching, boundary conditions, etc. all complete with &#8220;Done&#8221; before the error appears). I have triple-checked that none of my setup or solution settings have changed in the process of replacing the mesh.<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">&nbsp;<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">One thing I&#8217;ve noticed that may be related: my case has the Adjoint Solver active (I did not intentionally enable this), and I&#8217;ve found adjoint x-velocity, adjoint y-velocity, and adjoint pressure fields appearing in my Patch panel. I suspect the mesh-settings may be failing while trying to carry adjoint-related data across onto the new mesh, but I haven&#8217;t been able to find a straightforward way to fully deactivate the Adjoint Solver via the TUI or ribbon. Any guidance on properly disabling it would also be appreciated, in case that resolves the mesh-read issue.<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">&nbsp;<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">Below is a description of my model, in case it helps:<\/p>\n<ul style=\"direction: ltr;unicode-bidi: embed;margin-top: 0in;margin-bottom: 0in\" type=\"disc\">\n<li style=\"margin-top: 0;margin-bottom: 0;vertical-align: middle\"><span style=\"font-family: Calibri;font-size: 11.0pt\">VOF model with explicit volume fraction parameters, implicit body force formulation, sharp interface modelling, and interfacial anti-diffusion all activated.<\/span><\/li>\n<li style=\"margin-top: 0;margin-bottom: 0;vertical-align: middle\"><span style=\"font-family: Calibri;font-size: 11.0pt\">Phase interaction between water and air with a constant surface tension coefficient of 0.072 N\/m; surface tension force modelling and continuum surface force both enabled.<\/span><\/li>\n<li style=\"margin-top: 0;margin-bottom: 0;vertical-align: middle\"><span style=\"font-family: Calibri;font-size: 11.0pt\">I am modelling 2D droplets with a diameter of 0.1 mm. I am using an axisymmetric boundary condition (with gravity defined along the positive x-axis, and the domain in the positive y-direction), so I am only modelling half the droplet. The mesh is 15 mm long &times; 1.5 mm wide, with pressure outlets on all other sides, so that when initialised with hybrid initialisation, the pressure is constant throughout the field. The droplet is patched in after initialisation.<\/span><\/li>\n<li style=\"margin-top: 0;margin-bottom: 0;vertical-align: middle\"><span style=\"font-family: Calibri;font-size: 11.0pt\">I am currently using a PISO solution method with the following spatial discretization settings: <\/span><\/li>\n<ul style=\"direction: ltr;unicode-bidi: embed;margin-top: 0in;margin-bottom: 0in\" type=\"circle\">\n<li style=\"margin-top: 0;margin-bottom: 0;vertical-align: middle\"><span style=\"font-family: Calibri;font-size: 11.0pt\">Gradient: Least Squares Cell Based<\/span><\/li>\n<li style=\"margin-top: 0;margin-bottom: 0;vertical-align: middle\"><span style=\"font-family: Calibri;font-size: 11.0pt\">Pressure: PRESTO!<\/span><\/li>\n<li style=\"margin-top: 0;margin-bottom: 0;vertical-align: middle\"><span style=\"font-family: Calibri;font-size: 11.0pt\">Momentum: Second Order Upwind<\/span><\/li>\n<li style=\"margin-top: 0;margin-bottom: 0;vertical-align: middle\"><span style=\"font-family: Calibri;font-size: 11.0pt\">Volume Fraction: Geo-Reconstruct<\/span><\/li>\n<\/ul>\n<\/ul>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">&nbsp;<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">Any suggestions on how to avoid this error when reading in a different mesh, how to fully deactivate the Adjoint Solver, or general comments on improving my current model\/solver settings would be greatly appreciated.<\/p>\n<p style=\"margin: 0in;font-family: Calibri;font-size: 11.0pt\">Thanks!<\/p>\n","protected":false},"template":"","class_list":["post-463100","topic","type-topic","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, I am modelling water droplets falling in air to reach their terminal velocity using a VOF multiphase model. 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