DeltaSizer: a cross-platform planner for mesh resolution, time step and computational cost of CFD, fire and finite-element simulations

Choosing the cell size, near-wall resolution and time step is the first decision in every numerical simulation, and it largely determines both accuracy and cost. The relevant criteria are scattered across the turbulence, fire, combustion, multiphase and finite-element literature. DeltaSizer gathers them in one free desktop application for Windows and macOS. Ten calculators cover flow-regime characterisation; first-cell height for a target y+ , inflation layers and wall-unit spacing for RANS, wall-modelled and wall-resolved LES and DNS; turbulence scales, LES filter width and RANS inlet values; element size and time step for transient conduction and structural dynamics; Lagrangian particle response; Fire Dynamics Simulator (FDS) planning based on the characteristic fire diameter; premixed-flame resolution and combustion regime; convective, acoustic and diffusive time-step limits; the Grid Convergence Index; and the cell count, memory, run time and storage of a complete simulation. Every result is reported with the equations, assumptions and references used, and can be exported as a PDF report. The implementation is verified against published values, including the worked example of the ASME grid-convergence procedure.