TUFLOW General Discussion: Difference between revisions
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** variation in pipe approach and exit angles at junctions
** variation in pipe approach and exit elevation at junctions
* Alternative loss methods to Engelund are also available, such as Fixed losses. The Fixed method conforms with some industry guidelines, such as the Qld Urban Drainage Manual (QUDM). Fixed losses are not set as the default as this generally requires the modeller to manually enter appropriate values at every manhole, whereas the Engelund approach in TUFLOW, which is based on that in MIKE Urban with several improvements developed in conjunction with Gold Coast City Council’s infrastructure team, provides an excellent automatic approach with no or minimal user input beyond the pipe and manhole geometry. The other advantage of the Engelund approach is that it is dynamic and adjusts losses according to the flow conditions, whereas the Fixed approach assumes the same energy loss coefficient for all flow regimes. TUFLOW also allows having a mix of different methods in the one model, for example, there may be a special manhole where the Fixed or other approach needs to be applied.
* 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.
* 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? ==
Different software will give different results for the simple reason that they all include different calculation assumptions. Understanding what those assumptions are and how they influence results will be important for the sensitivity testing.
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. 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. Helpful software support, coupling with 1D and integration with GIS also needs to be considered as it is very important for many users.<br>
The <u>[http://book.arr.org.au.s3-website-ap-southeast-2.amazonaws.com/ Australian Rainfall and Runoff document]</u> has a good section in Book 6 on flood hydraulics. This discusses difference in solution scheme such as finite difference, finite volume, finite element, and implicit versus explicit.
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