LowMachReact-Hex Documentation

Welcome to the technical documentation for LowMachReact-Hex, a Fortran 2008 MPI finite-volume solver for constant-density low-Mach / incompressible flow on hexahedral meshes.

The current staged solver supports incompressible projection, passive species transport, passive sensible-enthalpy transport, Cantera thermodynamic/property evaluation, VTU/PVTU output, and MPI-aware profiling. Variable-density low-Mach coupling, reactions, reaction heat release, and external radiation physics remain future work.

Documentation Sections

• Numerical Method: Governing equations, finite-volume discretization, projection method, species transport, and sensible-enthalpy transport.
• Current Solver State: Current enabled physics, disabled physics, runtime ordering, and density/thermo conventions.
• Installation and Run Guide: Conda environment creation, OpenMPI setup, build commands, mesh generation, and case execution.
• Input Configuration: Compact case.nml reference.
• Input Configuration Guide: Longer configuration guide with recommended validation modes and examples.
• Energy and Thermodynamic Conventions: Sensible enthalpy, temperature recovery, Cantera reference state, heat conduction, and qrad sign convention.
• Enthalpy/Species Coupling Convention: Option A convention for preserving transported h when species composition changes.
• Cantera Interface Notes: Cantera bridge responsibilities, sensible enthalpy convention, composition rules, density rules, and cache dependencies.
• Profiling Guide: How to enable and interpret the MPI-aware nested profiler.
• Validation Ladder: Recommended build, regression, energy, Cantera thermo, species, and future qrad validation steps.

• Architecture: System design, MPI decomposition, module responsibilities, and future growth path.

• DEVELOPER_GUIDE.: Instructions for development.

Current Solver Stage

The current solver should be interpreted as a constant-density projection code with optional passive scalar physics:

rho_flow = params%rho
p0       = params%background_press
h        = transported sensible enthalpy
T        = T(h, Y, p0)

Cantera thermodynamic density is available as rho_thermo, but it is diagnostic/future-use only and is not used by the pressure projection.

Project Goal

The primary objective is to provide a scalable, research-oriented framework for validating finite-volume flow, species, enthalpy, thermodynamic-property, and future radiation/chemistry coupling on hexahedral meshes.

Key Features

• Fractional-Step Projection: Pressure-velocity coupling for constant-density incompressible flow.
• Scale-on-Demand Species: Dynamic handling of passive species mass fractions.
• Passive Sensible-Enthalpy Transport: Transported h with temperature recovered from h, Y, and p0.
• Cantera Integration: Transport properties and thermodynamics through Cantera, including h <-> T, cp, lambda, and diagnostic rho_thermo.
• Replicated Mesh MPI: Full mesh visibility on each rank with owned-cell decomposition for current flow/species/energy work.
• MPI-Aware Profiling: Inclusive flat and nested timing reports for projection, species, energy, Cantera sync, output, and MPI communication.
• VTU/PVTU Output: ParaView-ready visualization output and CSV diagnostics.

Generated using FORD (Fortran Documenter).