1.2 TUFLOW FV

1.2.1 Flexible Mesh Finite Volume

TUFLOW FV is a two and three dimensional flexible mesh hydrodynamic modelling engine designed for use in a broad range of environmental and engineering applications. Typical uses include the simulation of riverine and floodplain hydraulics, coastal and estuarine hydrodynamics, sediment transport and morphological processes, lake dynamics and integrated water quality and ecological modelling. Applications extend to tidal and current simulation, storm tide and tsunami propagation and inundation, pollutant and outfall plume dispersion, freshwater and receiving water process modelling (including lakes, rivers, reservoirs, estuaries and other related waterways), and metocean characterisation, supporting both detailed engineering design and environmental assessment workflows.

The TUFLOW FV solver is based on a conservative finite volume formulation of the nonlinear shallow water equations, providing robust handling of wetting and drying processes and effective shock capturing. The solver is available for Windows and Linux platforms and can be executed using either CPU or GPU hardware. GPU acceleration is provided through the TUFLOW FV GPU Module. The CPU implementation employs shared memory parallelism via OpenMP to scale efficiently across available cores, while the GPU implementation targets CUDA enabled NVIDIA devices. Numerical results are consistent to round off between CPU and GPU builds, enabling portability of models across hardware configurations and operating systems.

Both cartesian and spherical coordinate systems are supported. The model includes representation of key environmental processes such as bed friction, Coriolis effects, wind stress, rainfall, evaporation, and atmospheric pressure. A comprehensive set of boundary condition formulations is available for coastal, estuarine, and riverine applications, including open boundaries, fixed and moving point source inflows, and spatially and temporally varying forcings such as wind fields and short wave radiation. Optional coupling to externally defined spectral wave fields is supported, along with integration with selected third party models for oceanic and atmospheric boundary condition specification.

Model configuration follows TUFLOW’s layered data approach, whereby input datasets are read sequentially and later layers may override earlier ones. This allows localised modifications such as refined bathymetry or bed classification to be applied without duplicating base datasets, supporting transparent, auditable, and maintainable model development.

Simulation management functionality includes support for model scenarios, events, and user defined variables. These features enable multiple simulations to be generated from a single, well configured model definition. In combination with batch and multi run execution, restart chaining, and scheduler compatible command line operation, TUFLOW FV supports automated, parallelised, and reproducible workflows on local workstations and cloud based systems.

One dimensional hydraulic structures that exchange mass and momentum with the two or three dimensional domain are supported. Available structure types include weirs, culverts, bridges, gates, pumps, and destratification units, with optional operational control logic.

Model outputs include two dimensional map based results in SMS, DAT and XMDF formats, combined two and three dimensional outputs in NetCDF format, and CSV time series for detailed analysis. TUFLOW FV integrates with common GIS and graphical user interface tools such as ArcGIS, QGIS, and SMS. MATLAB and Python toolboxes are provided to support model construction, results visualisation, specialised plotting, and post processing workflows.

1.2.2 Add-on Modules

1.2.2.1 Three Dimensional (3D) Module

The TUFLOW FV Three Dimensional (3D) Module resolves vertical structure using sigma or z coordinate vertical meshes. Baroclinic pressure gradient terms are included, enabling the flow field to respond to density variations arising from temperature, salinity, and suspended sediment, the advection dispersion simulation of which is included within the 3D module. The conservative finite volume formulation is well suited to representing strong vertical gradients, including thermal stratification, fronts, and sharp pycnoclines, while maintaining mass balance, numerical accuracy, and stability.

Vertical turbulence and scalar mixing are represented through inbuilt closure schemes based on k-epsilon and k-omega formulations, providing consistent parameterisation of eddy viscosity and tracer mixing. Background terms and limiters may be configured to maintain numerical stability across weakly and strongly stratified regimes. A fully integrated atmospheric heat exchange balance is available to drive temperature evolution from standard meteorological inputs, and boundary condition formulations support baroclinic inflows and outflows as well as flexible specification of initial conditions.

Three dimensional analysis and data extraction are supported through QGIS, the TUFLOW FV Python Toolbox, and the TUFLOW FV MATLAB Toolbox. Available outputs include vertical profiles, slices, layer based maps, and depth averaged products to support streamlined calibration and reporting. In addition, TUFLOW FV natively outputs a comprehensive range of three dimensional result fields for detailed inspection and post processing.

1.2.2.2 Sediment Transport (ST) Module

The TUFLOW FV Sediment Transport (ST) Module simulates two and three dimensional sediment dynamics for mixed beds and suspended loads across creek, river, reservoir, estuarine, and coastal or oceanic environments. The module represents current driven and wave enhanced transport, exchange between the water column and bed through erosion and deposition, and bed level evolution with full hydrodynamic feedback. Suspended sediment is transported within the flow field (through deployment of advection dispersion capability included within the ST module), while bedload is routed along the bed with slope and curvature effects, enabling representation of bars, channels, and shoreface evolution under transient forcing.

Process formulations are provided for both noncohesive and cohesive sediment erosion and deposition, with user control over critical shear stresses, availability limits, and settling velocity specifications. The framework supports consolidation effects, hindered settling, near bed concentration corrections, and slope driven gravity adjustments. Morphological updating is mass conservative and may be accelerated where appropriate to support long term simulations.

One or more sediment fractions may be defined and tracked in both the water column and the bed. Simulations may include multiple cohesive and noncohesive fractions, each with independent transport formulations and parameter sets. This enables representation of grain size dependent behaviour, sorting and armouring, hiding and exposure effects, and multilayer bed stratigraphy within an active layer. The fraction based approach supports targeted calibration and scenario testing for mixed bed systems, dredging and disposal operations, and morphology change assessments.

The module supports spatially and temporally varying sediment sources and boundary concentrations, and provides diagnostic outputs to support quality assurance and calibration, including mass budgets, erosion and deposition totals, bed level change, and shear stress metrics. Results are available as maps, time series, and profile or curtain outputs, consistent with TUFLOW FV post processing toolchains for efficient analysis and reporting.

Documentation for the TUFLOW FV ST module configuration (beyond activation from TUFLOW FV) is available in the TUFLOW FV Sediment Transport and Particle Tracking Modules User Manual.

1.2.2.3 Water Quality (WQ) Module

The TUFLOW FV Water Quality (WQ) Module supports two and three dimensional simulation of water quality and ecological processes, with a configurable level of process complexity to suit a wide range of project requirements. The module includes advection and dispersion of constituents as well as associated transformation processes. Typical constituents include dissolved oxygen, inorganic nitrogen and phosphorus species, silicate, labile and refractory organic matter, one or more phytoplankton groups, and one or more pathogen groups.

Represented processes include water column transformations between constituents, benthic exchange with the sediment bed (for example, sediment oxygen demand), and atmospheric exchanges such as oxygen dissolution and rainfall deposition. Phytoplankton dynamics include primary production, respiration, and exudation, while pathogen dynamics include mortality, inactivation, settling, and attachment and detachment processes.

The framework supports spatially and temporally varying initial and boundary conditions, external loads, and scenario specific parameter sets. Diagnostic outputs include mass balance checks and constituent budgets to support calibration and QA/QC. Results align with TUFLOW FV post processing tools for mapping, profile and curtain analysis, and time series extraction in both two and three dimensional configurations.

Documentation for the TUFLOW FV WQ module configuration (beyond activation from TUFLOW FV) is available in the TUFLOW FV Water Quality (WQ) Module User Manual.

1.2.2.4 Particle Tracking (PT) Module

The TUFLOW FV Particle Tracking (PT) Module simulates discrete Lagrangian particles in two or three dimensions, transported by the modelled flow field and optional external forcings such as wind or wave driven drift.

Particle behaviour options include settling and buoyancy, first order decay, sedimentation and resuspension, stochastic dispersion, and simplified interaction rules with boundaries and shorelines, such as beaching or stranding. Particles may be released from fixed points, lines, areas, or moving sources, with flexible scheduling and attribute specification to support applications including larval transport, and debris trajectory assessment.

Outputs include particle position, age, and state or fate classification, along with diagnostic metrics to support quality assurance, such as counts by class and time within zone statistics. Results are provided in formats suitable for mapping, time series analysis, and profile or curtain visualisation, and integrate with QGIS, the TUFLOW FV Python Toolbox, and the MATLAB Toolbox to support efficient analysis and reporting.

Documentation for the TUFLOW FV PT module configuration (beyond activation from TUFLOW FV) is available in the TUFLOW FV Sediment Transport and Particle Tracking Modules User Manual.

1.2.2.5 GPU Hardware (GPU) Module

The TUFLOW FV GPU Module enables execution of the TUFLOW FV solver on NVIDIA CUDA capable graphics processing units. The module provides drop in acceleration of the standard solver, using identical model inputs and producing outputs that are numerically consistent with the CPU build to round off accuracy.

GPU acceleration can deliver substantial reductions in simulation run time for large meshes and long duration simulations. Project benchmarks demonstrate order of magnitude performance improvements relative to single core CPU execution.