OpenFOAM Assistant-AI OpenFOAM CFD help

Example

External aerodynamics (steady RANS) for a sedan at 30 m/s. - Solver & models: simpleFoam + kOmegaSST with wall functions; rhoConst, nu from transportProperties. - Mesh: snappyHexMesh with near-wall prismatic layers sized for target y+≈50; domain extents 5L downstream, 2L upstream, 2L lateral/top. - Numerics (draft snippets): system/controlDict: "application simpleFoam;\nstartFrom latestTime;\nendTime 3000;\ndeltaT 1;\nwriteControl timeStep;\nwriteInterval 500;\nadjustTimeStep yes;\nmaxCo 0.7;\nfunctions{ forces{ type forces; libs(\"libforces.so\"); patches(\"car\"); rhoInf 1.225; CofR(0 0 0); } }" system/fvSchemes: "divSchemes{ div(phi,U) bounded Gauss upwind; div(phi,k) bounded Gauss upwind; div(phi,omega) bounded Gauss upwind; }\nlaplacianSchemes{ default Gauss linear corrected; }\ngradSchemes{ default cellLimited Gauss linear 1; }" system/fvSolution: "SIMPLE{ nNonOrthogonalCorrectors 2; }\nrelaxationFactors{ fields{ p 0.3; } equations{ U 0.7; k 0.7; omega 0.7; } }"

Scenario

You provide geometry and target operating point. The assistant back-solves a viable y+ and first-cell height, gives snappyHexMesh refinement levels on the car, road, and wake, drafts fvSchemes/relaxation for steady convergence, adds a 'forces' functionObject for drag, and outlines a verification plan (residual targets, drag plateau, mesh refinement checklist).

Example

Symptoms: Divergence at ~t=50 s with interFoam; continuity blow-up and 'boundedness' warnings for alpha.water. - Rapid triage steps returned by the assistant: 1) Check CFL: Reduce deltaT or enable adjustTimeStep; set maxCo=0.3 (and maxAlphaCo=0.2 for VOF). 2) Switch to more robust div schemes for convection of alpha and momentum (e.g., 'div(phirb,alpha) Gauss interfaceCompression 1; div(phi,U) bounded Gauss limitedLinearV 1;'). 3) Tighten pressure solver and increase nOuterCorrectors in PIMPLE to decouple aggressiveness. 4) Reinitialize problematic regions or provide better initial fields with setFields. - Log pattern recognition example: "time step continuity errors : sum local = 2.1e-01, global = -3.4e-03" → assistant suggests smaller time step, improved pressure tolerance, and additional non-orthogonal correctors if mesh quality warrants. - Sanity checks: Compare forces histories, net mass balance, and monitor probes at key locations; ensure y+ is within model guidance.

Scenario

You paste a snippet of log and checkMesh output. The assistant identifies high skew/non-orthogonality and recommends: (a) laplacian 'corrected' plus more nNonOrthogonalCorrectors, (b) limiter-based div schemes for scalars, (c) relaxationFactors for pressure=0.2 and velocities=0.7, (d) local mesh smoothing or feature refinement in snappy. It then provides exact dictionary edits and a minimal Allrun sequence to rerun with safe defaults, plus expected signatures of a recovering run (monotonic residual drop, controlled Co, bounded alpha).

Example

Parallel run on a 64-core node; adding a custom momentum source without a new solver. - Decomposition & runtime: system/decomposeParDict: "numberOfSubdomains 64;\nmethod scotch;\ncoeffs{}" controlDict runtime tuning: "writeCompression on; purgeWrite 3; writeFormat ascii;" (or 'binary' for speed/size) and 'writeInterval' aligned with your sampling needs. Use 'distributed' and 'overDecomposition' when scaling beyond memory limits. - fvOptions vectorExplicitSource (no compile): "fvOptions{ momentumSource{ type vectorExplicitSource; active yes; selectionMode all; vectorExplicitSourceCoeffs{ volumeMode specific; injectionRateSuSp ( (U (10 0 0)) (0 0 0) ); } } }" - Minimal C++ hook (if editing a solver): "#include \"fvOptions.H\"\n...\nfvVectorMatrix UEqn( fvm::ddt(U) + fvm::div(phi,U) - fvm::laplacian(nuEff,U) );\nfvOptions.constrain(UEqn);\nUEqn.solve();\nfvOptions.correct(U);" - Automation: Allrun/Allclean templates that sequence mesh → decomposePar → solver → reconstructPar → postProcess with functionObjects (forces, wallShearStress, sample).

Scenario

You need overnight parametric runs. The assistant proposes overDecomposition to improve load balance, tweaks solver tolerances to reduce last-iteration churn, recommends 'binary' field format and lower writeInterval to cut I/O, and supplies a GNU parallel-based Allrun. For physics modification, it first tries fvOptions (no compile). If that’s insufficient, it provides a tiny, reviewable C++ patch to your solver and explains where to add fvOptions.addSup/correct. Finally, it adds a postProcess block to compute integrated forces and export CSV automatically.