TUFLOW General Discussion: Difference between revisions

The implicit approach is to estimate the future state based on the current state and the future rate of change. There are two common approaches to this “circular reference” problem. One is to reformulate the equations as a matrix problem, and the other is to use an iterative approach whereby the future state is repeatedly updated after successive calculations of the rate of change at the future time – also known as a backward implicit scheme. Both approaches can be very stable and enable larger timesteps, but the solution is permitted to “skip over” physics that happens on timescales smaller than the time increment. The timestep must still be appropriate based on Courant, Celerity, and Peclet numbers, but due to the iterative nature of the solution the time step can often be 10-20 times larger than that required for an explicit solution.<br>

 

== What is the difference between a finite difference scheme and a finite volume scheme? ==

TUFLOW HPC utilises an explicit finite volume scheme. This means that it has to use smaller timesteps and is guaranteed to capture the shortest time-scale physics that the given spatial resolution admits. The solution is conserving of mass and momentum to numerical precision. The scheme is not as computationally efficient as the implicit finite difference scheme of TUFLOW classic, if forced to execute on a single CPU core it is many times slower than Classic. However, as the cell-by-cell computation of fluxes and derivatives are completely independent, the scheme is well suited to utilise highly parallelised compute hardware such as modern GPUs. The end result is that with a good GPU, TUFLOW HPC can be up to 100 times faster than classic for some models.<br>

 

== Can TUFLOW's 1D engine be used for modelling complex pipe hydraulics? ==

* There are numerous pit inlet options, from automatic capture rates to manually defined depth-discharge relationships. In all cases the 2D cell water depth at the inlet influences the amount of flow entering the pit, and as such the 1D underground pipe network.

* The 2020 TUFLOW release offers sub-grid topography sampling to process all elevations within the cell into a depth/volume relationship for its calculations. This approach ensures much more accurate water depth estimations at pit inlets, even if the 2D cell resolution is much larger than the geometry of the drain at the inlet. This in turn translates to more accurate representation of the pit inflow, and as such flow through the entire pipe network. No other 1D/2D stormwater drainage modelling software offers this functionality. The new Quadtree functionality also allows the user to model key flowpaths, such as road drains, in high resolution.

 

== How closely do TUFLOW results match other hydraulic software? ==

TUFLOW, like all hydraulic modelling software, needs to be applied appropriately and models should be calibrated to real world events if calibration data are available.<br>

The three pillars of TUFLOW's development focus are solution accuracy, simulation speed, workflow efficient. Extensive benchmarking globally have demonstrated TUFLOW is top in its class in all three categories.

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