{"id":184654,"date":"2021-07-23T09:17:14","date_gmt":"2021-07-23T09:17:14","guid":{"rendered":"\/forum\/forums\/reply\/184654\/"},"modified":"2021-07-23T09:17:14","modified_gmt":"2021-07-23T09:17:14","slug":"184654","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/184654\/","title":{"rendered":"Reply To: Fluent: explicit VOF criteria excedance"},"content":{"rendered":"

\nThanks for your suggestions and sorry for my late response but I have been working on it. I cannot perform Dynamic Adaption because my mesh is large, so the computational time would be very large.
\nInstead, I have been doing some findings in the simulation. Before the VOF CFL rise up to values higher than the specified one (0.15), it is possible to see how the GLOBAL CFL rise up to values which are higher than the specified one (0.3). Figure below show how GLOBAL CFL evolves along the X-direction (Wave propagation direction). As you can see the CFL value near the platform is higher than 0.3 which is the specified maximum. Indeed, when the simulation continues this value keeps rising up to 250 when the simulation blows up.
\nThe values shown in the graph above are not in accordance with those shown by Fluent in the console output when the simulation runs
\nAlso, I would like to point that the simulations converges to the specified criteria even when whte CFL values are higher than expected in 10 to 15 iterations. So, I would say it is not a problem with the mesh that has a good quality (Orthogonal quality values -> Min: 0.2 – Max: 1.0- Mean: around 0.8)
\nI do not know why it is happening. According to documentation you provided to me and to the section “36.14.4. Multiphase-Specific Time Stepping”, the time step used should be the minimum of all the time steps calculated for different physics in the mesh. So, there should not be any cell where the CFL value where higher than 0.3.
\nHere is a quick summary of my simulation setup:
\nSolver type: Pressure based
\nTim: Transient
\nGravity: On
\nMuliphase: VOF – Open Channel Flow – Open Channel Wave BC – Inerface: sharp – Interfacial Anti-diffusion: enabled – Formulation: explicit
\nViscous: Laminar
\nPV Coupling sheme: PISO
\nGradient: LSCB
\nPressure: Presto!
\nMomentum: Second Order Upwind
\nVolume Fraction: Compressive (I have also tested with Geo-Reconstruct)
\nTransient Formulation: First Order Implicit
\nWarped-Face Gradient correction: enabled
\nHybrid Rhie-Chow term: enabled<\/p>\n

Here, I attatch to you an snapshot of my mesh
\n
\nWhy the prediction algorithm is not working properly? Is there something wrong in my simulation setup?<\/p>\n

Best Regards
\nSergio<\/p>\n

<\/p>\n","protected":false},"template":"","class_list":["post-184654","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t