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Line 1: =Introduction= This page of the TUFLOW Wiki discusses 2D cell size convergence. ~~Cell~~In well design modelling software such as TUFLOW, cell size convergence refers to the tendency for model results to trend towards a common answer as cell size decreases. This behaviour occurs due to topographic features that influence the hydraulic flow behaviour better approximating reality as resolution increases. The series of creek cross-section images below demonstrate this. As model resolution increases from 20m to 5m the modelled topography progressively matches the real-world geometry more closely.<br> [[File:Mesh_Converge_XS_20m.png\|500px]][[File:Mesh_Converge_XS_10m.png\|500px]][[File:Mesh_Converge_XS_05m.png\|500px]]<br> Unfortunately it isn't practical for all models to be designed at an infinitely fine resolution due to the impact it has on simulation speed. Increasing a model resolution will make a simulation run slower. As a rule of thumb, halving the cell size in a model will typically increase the simulation run time by a factor 8. This is due to the number of cells increasing by a factor of (4) four and the necessity for a calculation timestep half that of the larger resolution, translating to (2) twice the number of calculations (4 x 2 = 8). <br> Whilst high resolution modelling is always desirable, unfortunately it isn't practical in all situations due to the impact increasing resolution has on simulation speed. Even though TUFLOW with GPU hardware technology is arguably the fastest simulation software available, the time it takes for a model to run is still an important consideration. The challenge for modellers is knowing what resolution is necessary to achieve results that are fit for purpose with sufficient accuracy and having a model that can run within a reasonable time (i.e. hours, not days). <br> <u>[https://tuflow.com/download/Australian_Rainfall_Runoff_Project15_TwoDimensional_Modelling_DraftReport.pdf Australian Rainfall and Runoff Guideline - Two Dimensional Modelling in Urban and Rural Floodplain]</u> provides some recommendations on this topic. It states: <br>

TUFLOW 2D Cell Size Selection: Difference between revisions