TUFLOW 2D Cell Size Selection: Difference between revisions
Content deleted Content added
Chris Huxley (talk | contribs) |
Chris Huxley (talk | contribs) |
||
Line 159:
As per Test Case 1, selection of the appropriate cell resolution during a real-world project requires consideration of the intended use of the results and also how the simulation run time impacts the overall project timeline.
* Detailed integrated 1D/2D urban modelling may adopt the 15ft (4.6m) or slightly finer 12ft (3.7m) cell resolution if the cumulative simulation time for all model events/scenarios does not adversely impact the project timeline. This timeframe consideration is particularly relevant in locations such as Australia where an ensemble methodology is currently replacing single event approaches as a way to address uncertainty associated with hydrologic assumptions.
* Broad-scale quick run simulation for urban flood forecasting purposes may adopt a coarser 20ft cell resolution or investigate the suitability of a 25ft cell resolution to achieve a quicker simulation turnaround time.<br>
The run time results from this test case highlight a useful relationship used by modellers who wish to estimate likely simulations times for models that use a higher resolution than that presently simulated. The simulation time trend is as follows:
* A factor 1.5 increase in model resolution (eg. increasing the resolution from 30ft to 20ft) will increase the simulation time by a factor of 4.5.
* A factor 2.0 increase in model resolution (eg. increasing the resolution from 30ft to 15ft) will increase the simulation time by a factor of 8.0.
* A factor 3.0 increase in model resolution (eg. increasing the resolution from 30ft to 10ft) will increase the simulation time by a factor of 16.0.
This relationship is due to doubling the resolution (halving the cell size) increasing the number of cells by a factor (4) four and requiring half the time step to maintain stability (i.e. 2 two times the number of calculations).
The ratios for this test case don't match the above generalised trend exactly, though are close enough to be useful when optimising the cell size to meet project requirements.
[[File:Mesh_Converge_Direct_Rainfall_Simulation_Time_Factor.png|550px]]
| |||