TUFLOW is designed to model free-surface flow in coastal waters, estuaries, rivers, creeks, floodplains and urban drainage systems. Flow regimes through structures are handled by adaptation of the 1D St Venant Equations and the 2D Shallow Water Equations using standard structure equations. Supercritical flow areas can be represented (see note below).
Limitations and recommendations to note are:
In areas of super-critical flow through the 2D and 1D domains, the results should be treated with caution, particularly if they are in key areas of interest. Hydraulic jumps and surcharging against obstructions may occur in reality – these highly 3D localised effects are not modelled by software such as TUFLOW.
Where the 2D cell size is less than the water depth, the Smagorinsky viscosity formulation is preferred over the default constant viscosity formulation to model sub-cell turbulence (Barton 2001). It is always good practice to carry out sensitivity tests to ascertain the importance of the viscosity coefficient and formulation.
Caution should be used when using 2D cell sizes less than 2m, particularly when the flow depth exceeds the cell width (Barton 2001).
Modelling of hydraulic structures should always be cross-checked with desktop calculations or other software, especially if calibration data is unavailable. All 1D and 2D schemes are only an approximation to the complex flows that can occur through a structure, and regardless of the software used should be checked for their performance (Syme 1998, Syme 2001).
There is no momentum transfer between 1D and 2D connections. Although in most situations this is not of concern, it does influence results where a large structure (relative to the 2D cell size) is modelled as a 1D element.
