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=Backward Compatibility Change Register=
'''<font color="red">For changes in defaults post the 2017-09 build, see Chapter 18 of the <u>[https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]</u>.'''</font>
{|class="wikitable"
|No backward compatible workaround provided.<br>
|-
|If using “Reveal“<font color="blue"><tt>Reveal 1D Nodes</tt></font> <font color="red"><tt>==</tt></font><tt> ON”ON</tt>”, “Time“<font color="blue"><tt>Time Series Output Interval</tt></font> <font color="red"><tt>==</tt></font> ” must be specified.
|No backward compatible workaround provided.<br>
|-
|Set <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt>PRE 2016</tt> if similar results are required to the 2013-12-AC release.<br>
|-
|WARNING 2460 has been escalated to an ERROR and stricter command line syntax rules have been introduced ("=" will now return an ERROR message if TUFLOW is expecting "<font color="red"><tt>==</tt></font>")
|Set <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt>PRE 2016</tt> if similar results are required to the 2013-12-AC release.<br>
|-
| rowspan=1|2013-12-AA
| New default settings – see <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>==</tt></font><tt> PRE 2013-12</fonttt> in the user manual for a list of the commands that have changed in their default setting.
| Set <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt>PRE 2013-12</tt> if similar results are required to the 2012-05 release.
|-
| rowspan=1|2013-12-AC
| The default setting for <font color="blue">Link 2D2D Approach</font> has changed.
| Set <font color="blue"><tt>Link 2D2D Approach </tt></font> <font color="red"><tt>== </tt></font><tt>METHOD B</fonttt> to achieve the same results as Builds 2013-12-AA and 2013-12-AB. See Link 2D2D Approach for more information.
|-
| rowspan=2| 2012-05-AA
| New default settings – see <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt>PRE 2012-05</fonttt> for a list of the commands that have changed in their default setting.
| Set <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt>PRE 2012-05</tt> if similar results are required to the 2011-09 or 2010-10 releases.
|-
| The approach to the sizing of automatic manholes and the application of losses has been enhanced.
| Set <font color="blue"><tt>Manhole Approach </tt></font> <font color="red"><tt>== </tt></font><tt>Method A</fonttt> to achieve the same results as Build 2011-09-AA.
|-
| No workaround. Use the same platform (w32 or w64) for all simulations. Use <font color="blue">Model Platform</font> to force which platform should be used.
|-
| New default settings – see <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt> PRE 2010-10</fonttt> for a list of the commands that have changed in their default setting.
| Set <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt>PRE 2010-10</tt> if similar results are required to the 2008-08 or 2009 07 releases.
|-
| rowspan=1| 2008-08-AC
| The default setting for <font color="blue"><u>Shallow Depth Stability Factor</u></font> has changed.
| Set <font color="blue"><tt>Shallow Depth Stability Factor </tt></font> <font color="red"><tt>== 3</tt></font><tt> 3</tt> for models without direct rainfall to achieve the same results as Builds 2008-08-AA and 2008-08-AB. See <font color="blue">Shallow Depth Stability Factor</font> for more information.
|-
|-
| Uses a new set of defaults for a number of commands (see <font color="blue">Defaults</font> ).
| The new defaults produce slightly different results, and very slight differences also occur between the three versions offered. For established models run using the 2007-07-XX builds, use <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt>PRE 2008-08</tt> to use the default settings used by the 2007-07-XX builds. Testing of a range of models has shown zero change in results if <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt> PRE 2008-08</fonttt> switch is set, and the Compaq Fortran compiled version (cSP) is used. Each of the new default settings and their effects are discussed in the rows below.
|-
| The method for interpolating n values where the 2D Manning’s n varies with depth has been enhanced from a linear interpolation of the M (1/n) value to a spline interpolation of the n value. See <font color="blue"><u>Bed Resistance Depth Interpolation</u></font>.
| The new defaults may produce slightly different results. For established models run using the 2006-06-XX builds, use <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt>PRE 2007-07-AA</tt> to use the default settings used by the 2006-06-XX builds. Each of the new default settings and their affects are discussed in the rows below.
|-
| Change <font color="blue"><tt>Zero Material Values to One </tt></font> <font color="red"><tt>== OFF</tt></font><tt> OFF</tt> (previously ON)
| Will not cause different results if a <font color="blue"><tt>Set Mat </tt></font> <font color="red"><tt>== </tt></font><tt> 1</tt> is specified before other material settings in the .tgc file, or if every cell has been assigned a material value.
|-
| <font color="blue"><tt>Inside Region </tt></font> <font color="red"><tt>== </tt></font><tt> Method B</fonttt> (previously Method A)
| Testing thus far has not shown any difference between the two methods (other than the substantial gains in processing time of polygons).
|-
| <font color="blue"><tt>Line Cell Selection </tt></font> <font color="red"><tt>== </tt></font><tt> Method D</fonttt> (previously Method C)
| May change results slightly, but improved stability and a smoother water levels along HX lines result.
|-
| <font color="blue"><tt>VG Z Adjustment </tt></font> <font color="red"><tt>== </tt></font><tt> MAX ZC</fonttt> (previously ZC)
| May change results slightly, but stability should be significantly enhanced in some situations.
|-
| <font color="blue"><tt>Bed Resistance Cell Sides </tt></font> <font color="red"><tt>== INTERROGATE</tt></font><tt> INTERROGATE</tt> (previously AVERAGE M)
| Will influence results, usually slightly, but more pronounced where there are sudden changes in Manning’s n values such as in the urban environment.
|-
| <font color="blue"><tt>Culvert Flow </tt></font> <font color="red"><tt>== </tt></font><tt> Method D</fonttt> (previously Method C)
<font color="blue"><tt>Culvert Critical H/D </tt></font> <font color="red"><tt>== OFF</tt></font><tt> OFF</tt> (previously <font color="blue"><tt>Culvert Critical H/D </tt></font> <font color="red"><tt>== </tt></font><tt> 1.5</tt>)
| The most significant influences are the selection of upstream or downstream controlled regimes depending on the H/D ratio, and the bug fix relating to Regime E if <font color="blue"><tt>Structure Losses </tt></font> <font color="red"><tt>== ADJUST</tt></font><tt> ADJUST</tt>. Offers improved stability, better convergence for Regime C and smoother transitioning between some regimes.
|-
| Changed the setting of the default width (if eN1 < 0.001) of automatic weirs over R and C channels (i.e. RW and CW) to be the diameter/width multiplied by the number of culverts (previously, the width was not multiplied by the number of culverts).
|-
| Bug fix that incorrectly set the water levels on dried VG cells (only applies to simulations with source inflows, e.g. SA or RF, somewhere within in the model).
| May cause slight changes in results. Backward compatibility provided if <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt> PRE 2007-07-AA</fonttt> is set (noting that setting this command reinstates the bug). This bug also causes the mass error calculations to falsely give a mass error that is not occurring.
|-
| Fixed bug that did not correctly apply the reduction in conveyance for a FC BD (bridge deck) of FD (floating deck) cell using the 2d_fc Mannings_n attribute.
|-
| Uses a new set of defaults for a number of commands.
| The new defaults will produce different results. For established models run using the 2005-05-XX builds, use <font color="blue"><tt>Defaults </tt></font> <font color="red"><tt>== </tt></font><tt> PRE 2006-06-AA</fonttt> to use the previous default settings. Each of the new default settings and their affects are discussed in the rows below.
|-
| <font color="blue"><tt>Cell Wet/Dry Depth </tt></font> <font color="red"><tt>== </tt></font><tt> 0.002</fonttt> (previously 0.05) and <font color="blue"><tt>Cell Side Wet/Dry Depth </tt></font> <font color="red"><tt>== </tt></font><tt> 0.001</fonttt> (previously 0.03)
| The most pronounced effect of the shallower wet/dry depths is likely to occur in areas that are still filling at the flood peak, such as behind a levee that is only just overtopped. The shallower wet/dry depths provides a greater flow depth for a longer period over the levee.
|-
| <font color="blue"><tt>Adjust Head at ESTRY Interface </tt></font> <font color="red"><tt>== OFF</tt></font><tt> OFF</tt> (previously ON)
| Usually does not have a major influence on results except where very high velocities occur.
|-
| <font color="blue"><tt>Boundary Cell Selection </tt></font> <font color="red"><tt>== </tt></font><tt> Method C</fonttt> (previously Method A) and <font color="blue"><tt>Line Cell Selection </tt></font> <font color="red"><tt>== </tt></font><tt> Method C</fonttt> (previously Method A)
| May select slightly different cells along boundary/link lines. This may cause a difference where the line is along the top of levee, possibly creating a “hole” in embankment.
|-
| <font color="blue"><tt>Viscosity Formulation </tt></font> <font color="red"><tt>== Smagorinsky</tt></font><tt> Smagorinsky</tt> (previously Constant) and <font color="blue"><tt>Viscosity Coefficient </tt></font> <font color="red"><tt>== </tt></font><tt> 0.2</fonttt> (previously 1.0)
| Can have a significant effect where the viscosity term is influential. This occurs where the friction term is less dominant (i.e. low Manning’s n and/or deeper water such as the lower, tidal, reaches of rivers).
|-
| <font color="blue"><tt>Structure Losses </tt></font> <font color="red"><tt>== ADJUST</tt></font><tt> ADJUST</tt> (previously FIX)
| Can have a significant affect in the vicinity of structures within a 1D network and for culvert networks. Does not affect 1D structures linked to a 2D domain or at the structure ends not connected to another 1D channel.
|-
| <font color="blue"><tt>Storage Above Structure Obvert (%) </tt></font> <font color="red"><tt>== 5</tt></font><tt> 5</tt> (previously CHANNEL WIDTH)
| Usually negligible effect unless the model storage is predominantly within 1D closed sections (i.e. B, C and R channels). The 1D domain is likely to be more sensitive to instabilities due to the much smaller storage above the top of the closed sections, therefore, a smaller 1D timestep may be required and/or the Storage Above Structure Obvert (%) increased.
|-
| <font color="blue"><tt>Depth Limit Factor </tt></font> <font color="red"><tt>== 10</tt></font><tt> 10</tt> (previously 1)
| No effect as previously the model would have become “unstable” as the trigger for an instability was the top of the channel/node.
|-
| <font color="blue"><tt>Culvert Flow </tt></font> <font color="red"><tt>== </tt></font><tt> Method C</fonttt> (previously Method B)
| Usually only minor effects plus improved stability.
|-
| <font color="blue"><tt>Culvert Add Dynamic Head </tt></font> <font color="red"><tt>== ON</tt></font><tt> ON</tt> (previously OFF)
| Minor influence.
|-
| <font color="blue"><tt>Bridge Flow </tt></font> <font color="red"><tt>== </tt></font><tt> Method B</fonttt> (previously Method A)
| Negligible influence plus improved stability. However, note the different treatment of energy losses once the bridge deck obvert/soffit is submerged if a BG or LC table is specified.
|-
| <font color="blue"><tt>WLL Approach </tt></font> <font color="red"><tt>== </tt></font><tt> Method B</fonttt> (previously Method A)
| Only affects the presentation of results. Note, that Method A is no longer recommended or supported.
|-
| <font color="blue"><tt>Apply All Inverts </tt></font> <font color="red"><tt>== ON</tt></font><tt> ON</tt> (previously OFF)
Does not affect hydraulic calculations, however, if a Blank, B or W channel is now lowered/raised because the inverts are now used, this will affect results/stability - see note at end of Apply All Inverts).
|-
| <font color="blue"><tt>Conveyance Calculation </tt></font> <font color="red"><tt>== </tt></font><tt> ALL PARALLEL</fonttt> (previously CHANGE IN RESISTANCE)
| Will affect results as ALL PARALLEL can be around 10% more “slippery” than CHANGE IN RESISTANCE. For calibrated or established models developed using build prior to Build 2006-06-AA , recommend setting to CHANGE IN RESISTANCE
|-
| <font color="blue"><tt>Flow Calculation </tt></font> <font color="red"><tt>== </tt></font><tt> Method B</fonttt> (previously Method A)
| Negligible effect.
|-
|'''Builds prior to 2006-06-XX'''
| Contact <font[mailto:support@tuflow.com color="blue">support@tuflow.com</font>]
|
|}
The recommendation is usually for new or reworked models to use the newest build to take advantage of the latest features and enhancements, some level of calibration might be required for reworked models. The new TUFLOW executable is not different from the previous ones in the meaning that any existing model should be re-calibrated if there are available calibration data. However, particularly if a model is already calibrated, using prior builds of TUFLOW or winding back default settings using <font color="blue"><tt>Defaults</tt></font> <font color="red"><tt>== </tt></font> command is considered reasonable for established models that are to be used for minor tasks and an update of the model would not be cost effective.<br>
== What is the difference between single and double precision and when should I use them? ==
For each release of TUFLOW, both single and double precision engine versions are available. In the executable filename the single precision version of TUFLOW will include iSP and iDP for the double precision version. The double precision won't make the results twice as good, it stores numbers as 8-byte real numbers (15-17 significant figures) as opposed to 4-byte (6-9 significant figures). <br>
When to use single or double precision depends on the solution scheme:
* TUFLOW Classic uses water level as the primary variable within the hydrodynamic solver and double precision is typically necessary when using direct rainfall or with model elevations above 100m. In these cases, numerical precision (rounding errors) can cause mass conservation errors. For example, a small rainfall (e.g. 1mm/hr) converted to metres / second (~2.78e-7) may be lost through numerical precision and result in accumulated mass balance error, specially for longer model run time.<br>
* TUFLOW HPC uses cell-averaged water depth as the primary variable within the solver, rather than using water surface elevation as the primary variable and computing water depth on the fly from surface elevation minus bed elevation. This means that precision issues associated with applying a very small rainfall and/or modelling high elevations are not applicable in HPC. Unless testing shows otherwise, the single precision version of TUFLOW should be used for all HPC simulations. An error message will be triggered if TUFLOW HPC is used with double precision unless <font color="blue"><tt>HPC DP Check </tt></font> <font color="red"><tt>==</tt></font><tt> OFF</tt> is specified within the TCF. The need to use double precision with HPC could occur when the coupled ESTRY 1D engine requires the use of the double precision solver to achieve better stability in 1D with more significant numbers. This usually happens with carved 1D channels within the 2D domain, either the 1D channel itself or the boundary links between 1D and 2D domain are causing the mass error. On rare occasions, models with higher elevations and small QT inflow would also require to run in double precision, because QT boundaries have hidden 1D node and as such are solved in the 1D ESTRY engine.
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>
Advanced reasoning to use single precision with TUFLOW HPC:<br>
* HPC is an explicit finite volume scheme which is mass conserving to numerical precision.
* The HPC scheme uses 4th order time integration, which means the simulation completes in fewer time steps compared to 1st or 2nd order time integration schemes.
==I am running existing and developed case and see differences away from the model changes. Why?==
Any geometry changes between models, no matter how small, will affect results, sometimes to a greater degree than that occurring in the area of change. For example, a few millimetres increase in water level can determine whether or not overtopping of an embankment occurs, and this can consequently cause even larger impacts on the downstream side of the embankment. Furthermore, these changes can be compounded by subsequent changes in timestepping when using the adaptive timestepping option (the default in TUFLOW HPC), especially at fringes of the flood extent, where cells are constantly wetting and drying. Modellers and reviewers should be judicious and pragmatic when assessing which impacts are real and which are numerical noise.<br>
Suggestions:
* Use the latest TUFLOW HPC release available.
* Check that cell size is appropriate to the modelling exercise.
* Use depth varying manning's n (lower manning's n for shallow water depths), specifically for direct rainfall models.
* Set appropriate <font color="blue"><tt>Map Cutoff Depth </tt></font> for the modelling task. e.g. direct rainfall models might have higher values to avoid undesirable noise on the wet/dry interface.
==Why seemingly identical models can produce non-identical results?==
Generally speaking single path numerical solvers such as those used for hydraulic modelling should be able to produce the same numerical results twice to the last bit of every binary number calculated and output. However, this can become difficult with parallel computations as the order in which a list of single or double precision numbers are summated can produce slightly different rounding errors and thereby produce very slightly different results. For the vast majority of models TUFLOW Classic, TUFLOW HPC and TUFLOW FV will reproduce numerically identical results when run on the same CPU/GPU. Occasionally this might not be the case when identical simulations are run on different CPUs/GPUs due to hardware differences.<br>
Prior to 2020-10-AB release, the new boundary method introduced in TUFLOW HPC 2020-01-AA release for inflowing HT and QT boundaries (refer see Section 6.1 of the 2020 Release Notes) can in rare situations be affected by bitwise reproducibility when parallelised. When this issue occurs, very slight numerical differences can occur throughout the model, noting that they will be of a much smaller magnitude than those that occur when carrying out impact assessments, but will cause undesirable numerical noise in the impact mapping.<br>
== Do I need TUFLOW licence to create TUFLOW inputs and view results from TUFLOW models? ==
No, a TUFLOW licence is only needed to run simulations. All TUFLOW inputs and outputs use free open formats that are read and editable by third party software, for example QGIS and Notepad++:
* Download Notepad++ to create and review tabular data: <u>[[NotepadPlusPlus_Tips | Notepad++ installation and tips]]</u>.
* Download QGIS: <u>[[QGIS_Tips | QGIS installation and tips]]</u>.
* To review maximum ASC/FLT grids just drag and drop them into QGIS.
* Install the TUFLOW Plugin: <u>[[TUFLOW_QGIS_Plugin | TUFLOW QGIS plugin installation and tips]]</u>.
* Use TUFLOW Viewer to review XMDF results: <u>[[TUFLOW_Viewer |TUFLOW Viewer]]</u>.
== How closely would 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.<br>
== Can TUFLOW's 1D engine be used for modelling complex pipe hydraulics? ==
TUFLOW can model complex pipe hydraulics with a level of accuracy similar or better than industry peers. There are a few notable features that place TUFLOW ahead of other software:
* TUFLOW's 1D solution accurately accounts for both non-pressurised and pressurised flows within the pipe network.
* TUFLOW's treatment of pipe junction losses is one of the most sophisticated. The default method (Engelund) will adjust losses dynamically every timestep of the simulation based on the hydraulic conditions at that time and the following:
** changes in pipe size
** expansion/contraction if there is a manhole at the pipe junction
** 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.
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