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Line 7: * All of the above can be configured with "operation controls". [https://www.tuflow.com/products/tuflow/ TUFLOW’s 2D Fixed Grid Engines] are dynamically linked to TUFLOW 1D. There are two 2D grid options, namely TUFLOW Classic and TUFLOW HPC. Both provide second order depth averaged 2D solutions to the shallow water equations (SWE). TUFLOW Classic development began in 1989. It uses a finite difference implicit solution, and is the recommended tool for single core CPU compute. TUFLOW HPC development began in 2010. It uses a finite volume explicit solution. TUFLOW HPC is the recommended tool for GPU compute hardware, where code parallelisation across 1000's of GPU CUDA cores can achieve simulation speed increases of up to 100 times compared to a single CPU. Functionally model input and outputs from TUFLOW Classic and TUFLOW HPC use identical formats. Both solvers are internationally recognised as industry leaders in simulation software for flood, catchment, integrated urban drainage and stormwater modelling applications.<br> <br> =Frequently Asked Questions (FAQ)= Line 55 ⟶ 56: 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 ~~non-water~~flows ~~liquids~~in steep slopes accurately?== The Saint-Venant equations are commonly shown in 1D form and represent the conservation of volume and momentum along a flow channel (also known as the dynamic wave equations). When extended to two dimensions, the Saint-Venant equations become what is commonly called the “Full shallow water equations”. These equations are physically correct and comprehensive, but do require a eddy-viscosity closure term for stability when higher-order interpolation schemes are used. This applies to both finite-difference and finite-volume form. When solved correctly, the solution accurately reproduces both subcritical and supercritical flow, as well as the location of transitions between the two including, importantly, locations of hydraulic jumps. Therefore the equations remain perfectly valid on steep ground. As a further note, we recommend using the sub-grid-sampling (SGS) feature for direct rainfall models as this improves the hydraulic response of small flow channels that are not well defined at the model cell size. Yes, this can be used by setting the following commands:▼ Empirical validation of TUFLOW up to a slope of approximately 10% is documented in Huxley (2005), refer to Figure 33 and Figure 39: <u>[https://www.tuflow.com/media/4989/2004-tuflow-testing-and-validation-huxley.pdf TUFLOW Validation and Testing, Chris Huxley Thesis.doc]</u> <br>The <font color="blue"><tt>viscosity coefficients </tt></font><font color="red"><tt>== </tt></font>command on its own is used to set the eddy viscosity. In this instance, you need to set the dynamic viscosity, which is a property of the fluid itself. This can be used by setting the following commands: The following link documents a <u>[https://www.tuflow.com/media/5015/2016-tuflow-gpu-best-practice-advice-for-hydrologic-and-hydraulic-model-simulations-huxley-et-al-hwrs-nz.pdf real world TUFLOW calibration example]</u> for a case study location where the average catchment slope is over 15% in the upper half of the catchment. <font color="blue"><tt>Viscosity Formulation </tt></font><font color="red"><tt>== </tt></font>Non-Newtonian<br> ▼ This original package of work was completed in 2015 using TUFLOW’s traditional cell centre/side zpt topography processing approach. The model was rerun in 2020 using the new SGS topography sampling feature for the <u>[https://www.tuflow.com/library/webinars/#feb2021_direct_rainfall Direct Rainfall webinar]</u>. <font color="blue"><tt>Viscosity Coefficients </tt></font><font color="red"><tt>== </tt></font>k, n, muLow, muHigh, tau0▼ Collectively, these simulations demonstrate that TUFLOW’s solution works well in steep catchments. They also highlight the benefits of using SGS. ==Can TUFLOW model non-water liquids?== ▲Yes, this can be used by setting the following commands: ▲:<font color="blue"><tt>Viscosity Formulation </tt></font><font color="red"><tt>== </tt></font>Non-Newtonian<br> ▲:<font color="blue"><tt>Viscosity Coefficients </tt></font><font color="red"><tt>== </tt></font>k, n, muLow, muHigh, tau0 Where Kk is the viscosity coefficient in Pa S.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 ~~new release notes [~~<u>[https://downloads.tuflow.com/TUFLOW/Releases/2020-10/TUFLOW%20Release%20Notes.2020-10-AD.pdf ~~here]~~2020 Release Notes]</u> for more information. The graphs below explains the Herschel-Bulkley approach and it’s flexibility. : :::[[File:Newtonian_Model.png \| 400px]] With a Newtonian fluid, the shear stress is linearly proportional to the shear rate. ~~:::::::::::::::::::~~:[[File:Formula 001.PNG \| 100px]] For a non-Newtonian fluid, the shear stress varies non-linearly with shear rate, this is what is represented with the power law model in the graph above. :[[File:Formula 002.PNG \| 100px]] ~~τ=k(du/dy)^n~~ We then have Bingham plastics which have a linear shear stress to shear rate relationship but this time an offset which means there needs to be some force for the fluid to move, but then the shear stress varies linearly with shear rate. :[[File:Formula 003.PNG \| 130px]] ~~τ=τ_0+k(du/dy)~~ The Heschel-Bulkley model takes aspects from both the Bingham Plastic Model and the Power Law Model resulting in the following. :[[File:Formula 004.PNG \| 130px]] ~~τ=τ_0+k(du/dy)^n~~ It should be seen that where Ƭ0''Ƭ<sub>0</sub>=''0, the Herschel-Bulkley equation is the same as the power law model. If ''n'' is 1, then the Herschel-Bulkley equation is the same as the Bingham Plastic model. If Ƭ0''Ƭ<sub>0</sub>''=0 and ''n'' =1, then the Herschel-Bulkley equation is the same as the Newtonian fluid approach. By using the Herschel-Bulkley equation as a Newtonian model, it does allow you to define the viscosity coefficient for the fluid. InThere ~~your~~may ~~case~~be ~~you’ll~~a need to convert the viscosity from centiStokes to Pa S (if using an N''n'' value of 1). ~~You~~It ~~can~~is ~~then~~also possible to define the fluid density using the <font color="blue"><tt>Density of Water</tt></font> command ~~you mention~~. You can test this out using the following commands. :<font color="blue"><tt>Viscosity Formulation </tt></font><font color="red"><tt>== </tt></font>Non-Newtonian<br> :<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 Ƭ0''Ƭ<sub>0</sub>''=0 and a viscosity coefficient of 0.001 Pa S which is a typical viscosity of water at 20 ℃. This should give comparable outputs to a standard TUFLOW model without the Non-Newtonian functionality. == 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. <br> == What should managers and reviewers look out for? == Evidence the modelling is being quality controlled using the tests such as cell size results convergence as explained in greater details in our <u>[https://www.tuflow.com/library/webinars/#nov2020_2d_cell_size 2D cell size webinar]</u>. For modelling that is to be used for providing more precise metrics (e.g. for building floor levels) ensure the software being used is at the more accurate end of the spectrum and a good quality data is being used. If calibration data or anecdotal evidence exists, calibration or checking of the model should be carried out to help reduce the modelling uncertainty. <br> == How to check the flow in 2D model is the same as the source? == A mass balance is a good check on the model, e.g. with no losses the catchment area times rainfall depth should be the volume of water being applied as flow boundary to the hydraulic model. This is particularly important if using separate hydrologic and hydraulic models. If a sub catchment is missed or double counted then both the hydraulic model and the hydrologic model may show 0% mass error, but due to check for any errors a total volume check (Total in from source model - Total out from hydraulic model = Change in hydraulic model volume) should be carried out. In TUFLOW Plot Output lines can be included downstream of inflows to compare the hydraulic model inflow against the hydrology model results. For more information see our <u>[https://www.tuflow.com/library/webinars/#oct2022_quality_control Quality Control webinar]</u>.<br> == How to do hydraulic modelling with scarce site data? == The best thing to do in this case is to build the model using industry standard values. Do sensitivity testing of model inputs to identify if the results change dramatically due to the modelling choices, e.g. cell sizes, inflows, boundary influences. After building the model, any opportunity to conduct community consultation is usually well worthwhile as the locals will have a feel whether the model is demonstrating the flood behavior they have observed. For more information see <u>[https://www.tuflow.com/library/webinars/#maximise_accuracy Maximising the Accuracy of Hydraulic Model webinar]</u>.<br> <br> {{Tips Navigation \|uplink=[[TUFLOW_Modelling_Guidance \| Back to TUFLOW Modelling Guidance]]