TUFLOW General Discussion: Difference between revisions
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***The coupled TUFLOW 1D engine requires the use of the double precision solver to achieve better stability in 1D with more significant numbers. This usually happens with 1D/2D models with ground elevation greater than 100m (TUFLOW 1D engine uses water level as the primary variable as TUFLOW Classic), carved 1D channels within the 2D domain where either the 1D channel itself or the boundary links between 1D and 2D domain can cause the mass error. ***On rare occasions, models with higher elevations and small QT inflow would require double precision, because QT boundaries have hidden 1D node and as such are solved in the TUFLOW 1D engine.
***When the simulation time is long or the model has large Start Time value (more than 100000.0 hours), the around up issue can happen to the simulation time because the model timestep is typically in the order of 0.1~10 seconds. This might cause issues in reading and outputting boundary data.
***When very small inflow or outflows are applied, for example when representing evapotranspiration or the tail ends of storm events.
The single precision version of TUFLOW uses significantly less memory (RAM) and is about 20% faster for TUFLOW Classic and four times faster for HPC. Unless required otherwise, the single precision version of TUFLOW is recommended. A good step in the model development is to run the model with both the single and the double precision and if the results / mass balance are similar then the single precision version is sufficient.<br>
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* 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.
* The 2D overland approach used by TUFLOW ensures any above ground inundation is defined by the model topography. This approach avoids any engineering judgement flow path definition mistakes which the 1D overland software suffer from.<br>
* In addition, TUFLOW' s 1D solver (ESTRY) solves the full one-dimensional (1D) free-surface St Venant flow equations using a Runge-Kutta explicit solver. TUFLOW 1D has seen continuous development since 1972.The network schematisation technique used by TUFLOW 1D allows realistic simulation of a wide variety of 1D and quasi-2D situations including: complex river geometries; associated floodplains and estuaries; and urban channel and pipe network systems. There is a considerable amount of flexibility in the way network elements can be interconnected, allowing the representation of a river and floodplain by many parallel channels with different resistance characteristics and the simulation of braided streams and rivers with complex branching. This flexibility also allows a variable resolution within the network so that areas of particular interest can be modelled in fine detail, with a coarser network representation being used elsewhere.
==Can TUFLOW model flows in steep slopes accurately?==
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:<font color="blue"><tt>Viscosity Coefficients </tt></font><font color="red"><tt>== </tt></font>k, n, muLow, muHigh, tau0
Where k is the viscosity coefficient in Pa.s when ''n'' = 1. Where ''n''=1, this relates to a Newtonian fluid. You can then use an appropriate value for tau0, the stress required to make the fluid move. The Non-Newtonian model uses the Herschel-Bulkley approach which can be used to model Newtonian fluids with different viscosities. See section 5.4 of the <u>[https://downloads.tuflow.com/TUFLOW/Releases/2020-10/TUFLOW%20Release%20Notes.2020-10-AD.pdf 2020 Release Notes]</u> for more information.
The graphs below explains the Herschel-Bulkley approach and it’s flexibility:
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:[[File:Formula 004.PNG | 130px]]
It should be seen that where
You can test this out using the following commands.
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:<font color="blue"><tt>Viscosity Coefficients </tt></font><font color="red"><tt>== </tt></font>0.001, 1, 0.0, 1000, 0
This uses a ''n'' value of 1, a
== How closely do TUFLOW results match other hydraulic software? ==
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